WO1992002040A1 - Package for incorporating an integrated circuit and a process for the production of the package - Google Patents

Package for incorporating an integrated circuit and a process for the production of the package Download PDF

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Publication number
WO1992002040A1
WO1992002040A1 PCT/NL1991/000132 NL9100132W WO9202040A1 WO 1992002040 A1 WO1992002040 A1 WO 1992002040A1 NL 9100132 W NL9100132 W NL 9100132W WO 9202040 A1 WO9202040 A1 WO 9202040A1
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WO
WIPO (PCT)
Prior art keywords
package
plastic
packages
integrated circuit
lead frame
Prior art date
Application number
PCT/NL1991/000132
Other languages
French (fr)
Inventor
Eduard Pierre Marie Rousseau
Wouter Bastiaan Verwoerd
Frederik Ernst Nix
Original Assignee
Dsm N.V.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Dsm N.V. filed Critical Dsm N.V.
Publication of WO1992002040A1 publication Critical patent/WO1992002040A1/en

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L23/00—Details of semiconductor or other solid state devices
    • H01L23/12—Mountings, e.g. non-detachable insulating substrates
    • H01L23/13—Mountings, e.g. non-detachable insulating substrates characterised by the shape
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L23/00—Details of semiconductor or other solid state devices
    • H01L23/48—Arrangements for conducting electric current to or from the solid state body in operation, e.g. leads, terminal arrangements ; Selection of materials therefor
    • H01L23/488—Arrangements for conducting electric current to or from the solid state body in operation, e.g. leads, terminal arrangements ; Selection of materials therefor consisting of soldered or bonded constructions
    • H01L23/498—Leads, i.e. metallisations or lead-frames on insulating substrates, e.g. chip carriers
    • H01L23/4985—Flexible insulating substrates
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L25/00—Assemblies consisting of a plurality of individual semiconductor or other solid state devices ; Multistep manufacturing processes thereof
    • H01L25/03—Assemblies consisting of a plurality of individual semiconductor or other solid state devices ; Multistep manufacturing processes thereof all the devices being of a type provided for in the same subgroup of groups H01L27/00 - H01L33/00, or in a single subclass of H10K, H10N, e.g. assemblies of rectifier diodes
    • H01L25/10—Assemblies consisting of a plurality of individual semiconductor or other solid state devices ; Multistep manufacturing processes thereof all the devices being of a type provided for in the same subgroup of groups H01L27/00 - H01L33/00, or in a single subclass of H10K, H10N, e.g. assemblies of rectifier diodes the devices having separate containers
    • H01L25/105—Assemblies consisting of a plurality of individual semiconductor or other solid state devices ; Multistep manufacturing processes thereof all the devices being of a type provided for in the same subgroup of groups H01L27/00 - H01L33/00, or in a single subclass of H10K, H10N, e.g. assemblies of rectifier diodes the devices having separate containers the devices being of a type provided for in group H01L27/00
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    • H01L2224/01—Means for bonding being attached to, or being formed on, the surface to be connected, e.g. chip-to-package, die-attach, "first-level" interconnects; Manufacturing methods related thereto
    • H01L2224/10—Bump connectors; Manufacturing methods related thereto
    • H01L2224/15—Structure, shape, material or disposition of the bump connectors after the connecting process
    • H01L2224/16—Structure, shape, material or disposition of the bump connectors after the connecting process of an individual bump connector
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    • H01L2224/42—Wire connectors; Manufacturing methods related thereto
    • H01L2224/44—Structure, shape, material or disposition of the wire connectors prior to the connecting process
    • H01L2224/45—Structure, shape, material or disposition of the wire connectors prior to the connecting process of an individual wire connector
    • H01L2224/45001—Core members of the connector
    • H01L2224/45099—Material
    • H01L2224/451—Material with a principal constituent of the material being a metal or a metalloid, e.g. boron (B), silicon (Si), germanium (Ge), arsenic (As), antimony (Sb), tellurium (Te) and polonium (Po), and alloys thereof
    • H01L2224/45138—Material with a principal constituent of the material being a metal or a metalloid, e.g. boron (B), silicon (Si), germanium (Ge), arsenic (As), antimony (Sb), tellurium (Te) and polonium (Po), and alloys thereof the principal constituent melting at a temperature of greater than or equal to 950°C and less than 1550°C
    • H01L2224/45144—Gold (Au) as principal constituent
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    • H01L2224/4805—Shape
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    • H01L2224/48091—Arched
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    • H01L2224/80—Methods for connecting semiconductor or other solid state bodies using means for bonding being attached to, or being formed on, the surface to be connected
    • H01L2224/81—Methods for connecting semiconductor or other solid state bodies using means for bonding being attached to, or being formed on, the surface to be connected using a bump connector
    • H01L2224/8119—Arrangement of the bump connectors prior to mounting
    • H01L2224/81192—Arrangement of the bump connectors prior to mounting wherein the bump connectors are disposed only on another item or body to be connected to the semiconductor or solid-state body
    • H—ELECTRICITY
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    • H01L2225/03—All the devices being of a type provided for in the same subgroup of groups H01L27/00 - H01L33/648 and H10K99/00
    • H01L2225/10—All the devices being of a type provided for in the same subgroup of groups H01L27/00 - H01L33/648 and H10K99/00 the devices having separate containers
    • H01L2225/1005—All the devices being of a type provided for in the same subgroup of groups H01L27/00 - H01L33/648 and H10K99/00 the devices having separate containers the devices being of a type provided for in group H01L27/00
    • H01L2225/1011—All the devices being of a type provided for in the same subgroup of groups H01L27/00 - H01L33/648 and H10K99/00 the devices having separate containers the devices being of a type provided for in group H01L27/00 the containers being in a stacked arrangement
    • H01L2225/1017—All the devices being of a type provided for in the same subgroup of groups H01L27/00 - H01L33/648 and H10K99/00 the devices having separate containers the devices being of a type provided for in group H01L27/00 the containers being in a stacked arrangement the lowermost container comprising a device support
    • H01L2225/1023—All the devices being of a type provided for in the same subgroup of groups H01L27/00 - H01L33/648 and H10K99/00 the devices having separate containers the devices being of a type provided for in group H01L27/00 the containers being in a stacked arrangement the lowermost container comprising a device support the support being an insulating substrate
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    • H01L2225/03—All the devices being of a type provided for in the same subgroup of groups H01L27/00 - H01L33/648 and H10K99/00
    • H01L2225/10—All the devices being of a type provided for in the same subgroup of groups H01L27/00 - H01L33/648 and H10K99/00 the devices having separate containers
    • H01L2225/1005—All the devices being of a type provided for in the same subgroup of groups H01L27/00 - H01L33/648 and H10K99/00 the devices having separate containers the devices being of a type provided for in group H01L27/00
    • H01L2225/1011—All the devices being of a type provided for in the same subgroup of groups H01L27/00 - H01L33/648 and H10K99/00 the devices having separate containers the devices being of a type provided for in group H01L27/00 the containers being in a stacked arrangement
    • H01L2225/1041—Special adaptations for top connections of the lowermost container, e.g. redistribution layer, integral interposer
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L2225/00—Details relating to assemblies covered by the group H01L25/00 but not provided for in its subgroups
    • H01L2225/03—All the devices being of a type provided for in the same subgroup of groups H01L27/00 - H01L33/648 and H10K99/00
    • H01L2225/10—All the devices being of a type provided for in the same subgroup of groups H01L27/00 - H01L33/648 and H10K99/00 the devices having separate containers
    • H01L2225/1005—All the devices being of a type provided for in the same subgroup of groups H01L27/00 - H01L33/648 and H10K99/00 the devices having separate containers the devices being of a type provided for in group H01L27/00
    • H01L2225/1011—All the devices being of a type provided for in the same subgroup of groups H01L27/00 - H01L33/648 and H10K99/00 the devices having separate containers the devices being of a type provided for in group H01L27/00 the containers being in a stacked arrangement
    • H01L2225/1076—Shape of the containers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L24/00—Arrangements for connecting or disconnecting semiconductor or solid-state bodies; Methods or apparatus related thereto
    • H01L24/01—Means for bonding being attached to, or being formed on, the surface to be connected, e.g. chip-to-package, die-attach, "first-level" interconnects; Manufacturing methods related thereto
    • H01L24/42—Wire connectors; Manufacturing methods related thereto
    • H01L24/44—Structure, shape, material or disposition of the wire connectors prior to the connecting process
    • H01L24/45—Structure, shape, material or disposition of the wire connectors prior to the connecting process of an individual wire connector
    • H—ELECTRICITY
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    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L24/00—Arrangements for connecting or disconnecting semiconductor or solid-state bodies; Methods or apparatus related thereto
    • H01L24/01—Means for bonding being attached to, or being formed on, the surface to be connected, e.g. chip-to-package, die-attach, "first-level" interconnects; Manufacturing methods related thereto
    • H01L24/42—Wire connectors; Manufacturing methods related thereto
    • H01L24/47—Structure, shape, material or disposition of the wire connectors after the connecting process
    • H01L24/48—Structure, shape, material or disposition of the wire connectors after the connecting process of an individual wire connector
    • H—ELECTRICITY
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    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L2924/00—Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
    • H01L2924/0001—Technical content checked by a classifier
    • H01L2924/00014—Technical content checked by a classifier the subject-matter covered by the group, the symbol of which is combined with the symbol of this group, being disclosed without further technical details
    • H—ELECTRICITY
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    • H01L2924/01—Chemical elements
    • H01L2924/01078—Platinum [Pt]
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    • H01L2924/10—Details of semiconductor or other solid state devices to be connected
    • H01L2924/11—Device type
    • H01L2924/14—Integrated circuits
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    • H01L2924/15—Details of package parts other than the semiconductor or other solid state devices to be connected
    • H01L2924/151—Die mounting substrate
    • H01L2924/153—Connection portion
    • H01L2924/1532—Connection portion the connection portion being formed on the die mounting surface of the substrate
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    • H01L2924/15—Details of package parts other than the semiconductor or other solid state devices to be connected
    • H01L2924/161—Cap
    • H01L2924/1615—Shape
    • H01L2924/16152—Cap comprising a cavity for hosting the device, e.g. U-shaped cap
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    • H01L2924/15—Details of package parts other than the semiconductor or other solid state devices to be connected
    • H01L2924/181—Encapsulation

Definitions

  • the invention relates to a package for incorporating an integrated circuit comprising a plate substantially consisting of a plastic and of electrically conductive material, which plate is at least partly provided with an upright side with at least one contact point.
  • Such plastic packages for incorporating integrated circuits are generally known and are used on a large scale. See, for instance, the 'Microelectronics Packaging Handbook', chapter 8, pages 523-672 (Van Nostrand Reinhold, New York, 1989, ISBN 0-442-20578-3).
  • plastic packages are described of which the upright sides consist of metal strips projecting from the package and which may be bent, if so desired, in a particular shape.
  • the ends of the strips further form the contact points.
  • the known plastic packages are substantially composed of a metal lead frame, an integrated circuit (chip or IC), very thin gold connecting wires and a plastic or plastic moulding compound.
  • the lead frame is the central supporting structure of the package which every other element is fastened to.
  • a lead frame is punched from a thin metal strip or film or etched in a filigree of narrow leads projecting from a central platform (die pad).
  • the integrated circuit is fastened to the central platform and is electrically connected with the filigree of narrow leads by means of the very thin gold wires.
  • the ends of the narrow leads eventually form the so-called contact points.
  • the contact points constitute those places where the electric contact is established between the package and its environment, for instance a printed circuit board (PCB) .
  • PCB printed circuit board
  • pin counts are limited.
  • the pin count is the total number of leads of a package. Such a lead is referred to in technical jargon also as I/O pin (Input/Output pin).
  • I/O pin Input/Output pin
  • the limitation of the pin count lies particularly in the fact that the leads become too thin and too long. This causes a deterioration of the mechanical rigidity of the leads, which may therefore become bent during their encapsulation with a plastic.
  • a process cycle is understood to mean, for instance, the encapsulation of the frame with a plastic.
  • thermal strains are brought about on the interface of the frame and of the plastic and on the interface of the frame and of the integrated circuit.
  • the thermal strains on the interfaces of the frame and plastic may result in the formation of microcracks, so that moisture can penetrate into the package. This may lead to failure of the package.
  • the strains On the interface between the frame and the integrated circuit the strains may result in the faulty operation of the integrated circuit.
  • a process cycle is the soldering of the package on a substrate.
  • vapour phase soldering a package is heated up to about 260oC. This, of course, causes thermal strains again at all places where the frame is in contact with another material, such as the integrated circuit, the plastic, etc.
  • Thermal fatigue mainly occurs at those places where two relatively rigid components (integrated circuit, frame, substrate, printed circuit) are connected with each other (see 'Microelectronics Packaging Handbook', chapter 5.5, pages 277-320, Van Nostrand Reinhold, New York, 1989 and 'Soldering in Electronics', pages 305-310,
  • Another disadvantage of the known packages is the frequently inadequate adhesion between the frame and the encapsulating plastic. If the adhesion is insufficient, moisture may penetrate into the package. This may result in failure of the package. Particularly when thermoplastics ar used, the adhesion is very moderate. The adhesion is particularly poor if a thermoplastic liquid crystalline polymer is used as encapsulating material. Liquid crystalline polymers are polymers that have a more rigid molecular structure, unlike the traditional thermoplastics. That is why in the melted phase these polymers show a so-called nematic behaviour.
  • Such polymers orient themselve readily in a field of current, so that on the interfaces between the polymer and the lead frame a very highly oriented layer of polymer molecules is formed. In consequence, hardly any adhesion takes place between the molecules and the frame.
  • a disadvantage of the known packages is that a frame may interfere with the production process and therefore cause an increase in costs.
  • Each individual component (for instance a frame) of a composite article (fo instance the known package) must be produced and later on b combined to form the desired article. It will be clear that in every production step disturbances may occur. That is wh during the production of composite articles a maximum reduction of the number of components is generally aimed at.
  • the object of the invention is to provide a packag that does not have said disadvantages and problems.
  • the upright side contains a plastic, while the electrically conductive material is applied in the form of layers on the plate and on the upright side.
  • the effect is that for plastic packages no separate lead frame will be required any more, so that the pin count will no longer be limited by the frame technology. Moreover, there will no longer be any problems relating to the difference in thermal expansion coefficients of a lead frame and the integrated circuit, the plastic and the substrate.
  • the electrically conductive material applied on the package according to the invention takes care of the electric contact between the integrated circuit and the contact points (the places where the package is in contact electrically with its environment) . These electrically conductive contact paths are called conducting paths. These conducting paths may be very thin. Thin conducting paths are ductile, yielding, so that, owing to the interaction of the conducting paths and the plastic, thermal strains caused by the differences in expansion coefficients are absorbed by elastic deformations.
  • plastic frameless packages that does not incorporate a frame, but whose conducting paths constitute at least in part the contact points. See for instance: 'Application of Liquid Crystal Polymer for Molded Circuit Component', Gosei Jushi (Synthetic Resin), vol. 35, no. 8, 28 ff., 1989.
  • Such frameless plastic packages are called plastic leadless chip carriers (PLLCC).
  • PLLCC plastic leadless chip carriers
  • MID moulded interconnection device
  • Such PLLCCs are intended to be mounted and soldered on the surface of a substrate (SMT) . It here concerns a frame provided with conducting paths extending via the side to the underside of the frame.
  • PLLCCs frameless packages
  • the soldered connection between the package and the substrate is rigid. This causes thermal strains between the package and the substrate during the soldering and during use, which may give rise to thermal fatigue. This is due to the fact that the contact points are situated on the rigid part of the package.
  • Other disadvantages of the known frameless packages are the production of such packages, which is realized through the so-called two-shot moulding process, that is two-step injection moulding, and the patternization of the conducting paths, which is limited to a particular fixed form (outline). Further, the moulds for the production of the known frameless packages are complicated.
  • the plate and the upright side(s) of the package according to the invention will usually be of the same plastic material.
  • the advantage is that the plate and the side(s) can be made in one production step.
  • the package according to the invention is suited for various kinds of soldering technique such as, for instance, the 'through hole technology' and the 'surface mounting technology' . If so desired, the packages according to the invention can also be connected with a substrate via a so-called connector.
  • the die pads and the conducting paths can be applied to the thermoplastic material by the appropriate techniques such as, for instance, sputtering, an electrochemical treatment or a transfer technique.
  • the choice of the electrically conductive material is determined by the technique used in applying the material, the use of the package, the desired electrical and chemical characteristics of the material, the plastic and the cost of the package. Some options are, for instance, iron-nickel alloys, copper alloys and laminates of various metals and/or alloys. The person skilled in the art will be able to find the most suitable material.
  • the plastic from which the package according to the invention is produced can basically be chosen from all thermoplastics or thermosetting plastics known in the art. These are understood also to include all plastic compositions based on such plastics, such as blends and compounds.
  • the choice of a particular plastic or plastic moulding compound is substantially determined by the basic criteria which plastics or plastic moulding compounds must comply with if applied in packages for integrated circuits. Some basic criteria are the melt viscosity, the dimensional stability, the thermal stability, the possibility of metallizing the surface and a low moisture absorption.
  • Suitable plastics can be chosen from the category of high-grade thermoplastic engineering plastics such as, for instance, polyether etherketone, polyether ketone, polyamide imide, polyamides, polyphenylene sulphide, polyethylene halides such as polytetrafluoroethylene, polyether sulphone, aromatic polyesters, aromatic polyester amides and polyester carbonates. Preference is given to choosing the plastic from the group of aromatic polyesters, polyester amides or polyester carbonates, which are of a liquid, crystalline nature in the melted phase, the so-called liquid crystalline polymers (LCPs).
  • LCPs liquid crystalline polymers
  • Liquid crystalline polymers are known for their good (gas-)barrier properties, low expansion coefficients, good flow behaviour, low flammability (no flame retardants required), chemical inertness, thermal stability and the possibility of metallizing (preplating) the surfaces.
  • a plastic moulding compound of a liquid crystalline character may comprise, fo instance:
  • thermosetting plastics such as, for instance, epoxy resins and bismaleimide resins.
  • Packages according to the invention produced from the above-mentioned plastic moulding compounds have a high chemical and thermal inertness and are therefore resistant against the high temperatures encountered in the customary soldering techniques, such as vapour phase soldering.
  • the properties of the chosen plastic can be influenced, if so desired, by compounding the plastic with fillers such as, for instance, silica, alpha-quartz, aluminium oxide, carbon, fused silica, kaolin, talcum, wollastonite and/or combinations of these.
  • a special advantage of the package according to the invention is that the possibilities in respect of the dimensions and the design of the package are virtually unlimited.
  • the essential conditions defined for instance, a defined plastic moulding compound or a defined permissible thermal expansion/shrinkage of the total package
  • Optimum properties may, for instance, be a defined elastic deformation under strain in 2 or 3 dimensions or a certain degree of flexibility. It is likewise possible to produce packages for one particular application containing different plastics or plastic moulding compounds. These plastics and/or plastic moulding compounds will generally have different intrinsic properties.
  • the chosen plastics and/or plastic moulding compounds may further show an isotropic mechanical behaviour with a high or a low thermal expansion coefficient, but also an anisotropic mechanical behaviour such as, for instance, in the use of liquid crystalline polymers.
  • an isotropic mechanical behaviour with a high or a low thermal expansion coefficient
  • an anisotropic mechanical behaviour such as, for instance, in the use of liquid crystalline polymers.
  • Another special advantage of the package is that the upright sides may become wider as seen from the plate, so that the distances between the contact points are greater than the distances between the conducting paths. This configuration has major advantages if the pin counts are very high and the soldered connections at the contact points are therefore situated close together.
  • a second advantage of such a configuration is that the package can be modified to comply with the various requirements in respect of the place of and the distances between the contact points. The dimensions of the packages according to the invention can then be modified in a simple manner to comply with the essential conditions defined.
  • Another special advantage of the package according to the invention is that its design makes it possible for all contact points to be kept in one plane (coplanar). As the contact points are situated on the upright sides, they are fixed in space. This makes it impossible for the contact points, during the assembly of a package, when the pin count rises, to reach the substrate beside their appropriate place
  • the package according to the invention is produced in one step without inserts, using an injection moulding technique. This is a great advantage compared with the known packages.
  • the packages according to the invention are highly suited for incorporating a plurality of integrated circuits. Thanks to the constructional freedoms of the package according to the invention, a plurality of platforms (die pads) can be applied.
  • the platforms can be interconnected, if so desired, by conducting paths, which take care of the contacts between the platforms.
  • the application of a plurality of platforms does not involve any problem in so far as it concerns the technique (for instance sputtering, electrochemical, transfer technique) of applying the platforms and conducting paths on the plastic.
  • the package according to the invention may further be, or come to be, provided with constructional elements such as elevations or recesses enhancing the ease of handling the package during the production process such as, for instance, centring during the application and connection of an integrated circuit.
  • the package according to the invention may be, or come to be, provided with additional upright sides allowing the package to be sealed with a sealing element.
  • a sealing element provided with upright sides, so that the additional upright sides on the package need not be provided, if so desired.
  • the joint between the upright sides and the sealing element may, for instance, be glued or welded.
  • the welding operation may be chosen from, for instance, the category of laser welding. induction welding, friction welding and ultrasonic welding.
  • the cross section of the package is substantially U-shaped.
  • the packages according to the invention are U-shaped if all additional constructional elements are left out of consideration. Constructional elements are understood to mean all elevations, recesses and upright sides as described above.
  • the basic geometry of the package is basically simple, mechanically very stable, constructionally easy to produce, capable of being easily modified for specific uses and that there is basically perfect freedom in choosing the dimensions.
  • the shape can further be modified to suit the chosen plastic or plastic moulding compound, so that an optimum behaviour is obtained near the contact points.
  • Optimum behaviour may, for instance, be a defined elastic deformation under strain in 2 or 3 dimensions, or a certain degree of flexibility.
  • the geometry of the package in the vicinity of the contact points is preferably such as to suit the plastic in the package, so that a defined flexibility is obtained, reducing thermal effects during the soldering to an absolute minimum, and thermal fatigue does not play a critical role.
  • a plastic or plastic moulding compound has specific intrinsic properties.
  • the chosen plastic or plastic moulding compound may, for instance, show an isotropic mechanical behaviour with a high or a low thermal expansion coefficient, but also the anisotropic mechanical behaviour of, for instance, the liquid crystalline polymers.
  • Beside a straight geometry preference is given to a geometry which substantially looks like the edge of a stamp or a serrated edge.
  • Another preferred geometry is the so-called thick-thin configuration.
  • the thickness of the package between two neighbouring contact points is smaller than at each of the individual contact points.
  • the flexibility obtained at the contact points may be such as t allow the contact points under changing thermal conditions to move with the expansion or shrinkage of the substrate without mechanical strains arising.
  • a particular soldering technology may be taken into account i designing the geometry of the package near the contact poin
  • the integrated circuit can be applied in the package and be connected by means of existing technologies. Depending on the manner in which the package is sealed or closed, the moment of applying and connecting the integrate circuit can be chosen freely. This makes it possible for the integrated circuit to be applied later on in the production process. This may be an advantage particularly when expensive integrated circuits are used, because the risk of failure is reduced.
  • a special advantage of the package according to the invention is that, when the so-called flip-chip techniques are used, the required 'bumps', as they are called, can be applied on the conducting paths of the package, so that standard integrated circuits can be used. This contrasts with existing flip-chip systems, where the bumps must be applied on the integrated circuits. Such integrated circuits are very expensive. See for existing flip-chip techniques, for instance, 'Multichip Assembly with Flipped Integrated Circuits', IEEE Transactions on Components, Hybrids and Manufacturing Technology, vol. 12, no. 4, pages 650-657, December 1989.
  • the package according to the invention preferably has a plate provided all along its perimeter with an uninterrupted upright side.
  • the integrated circuit is preferably covered with a sealing element. The choice of the material of the sealing element is not critical. Examples are: metal, ceramics or a plastic.
  • a sealing element may be chosen comprising metal, ceramics or a plastic. Particularly suited is a sealing element provided with upright sides allowing the additional upright sides on the package to be omitted, if so desired.
  • it is possible to improve the quality of the weld by bringing the surface geometry of the contact faces in agreement with the chosen welding technique. It is known, for instance, that in order to obtain an optimum joint in the ultrasonic welding of plastics, the contact faces must be of a particular shape.
  • the above-mentioned welding ridges may be welded precisely onto each other such as, for instance, a triangular welding ridge on a triangular welding ridge or a trapezium-shaped welding ridge on a trapezium-shaped welding ridge, or a combination of these.
  • the package and/or the sealing element may be provided with a plurality of such upright sides.
  • Another preferred embodiment for sealing a package according to the invention is the sealing by means of blob-top.
  • Blob-top is the sealing of an integrated circuit using silicone gel or an epoxy. See, for instance, 'Die Losung gegen Stre ', Productronic, vols 7/8, pages 76-77, 1989.
  • the package according to the invention is preferably provided with one or more inserts.
  • Possible inserts are, for instance, an element for fastening the package such as, for instance, a screw attachment, an element for the removal of heat or an element for incorporating a battery, for instance.
  • All packages described above are preferably provided with an element for the removal of heat.
  • a package according to the invention is that the package is provided with ducts for the removal of heat. This makes it possible for the temperature of the package to be regulated arbitrarily, independently of the heat generated and/or of the ambient temperature.
  • the packages according to the invention are highly suited for incorporating, beside one or more integrated circuits, additional discrete parts or components.
  • Discrete parts or components are, for instance, eletcronic parts such as resistors, transistors and/or condensators and, for instance, feed units such as accumulators, solar cells, galvanic elements operating on temperature differences and/or batteries. Random combinations of parts are possible also.
  • the packages according to the invention are suited also for incorporating parts or components other than integrated circuits.
  • Suitable components are, for instance, i) electronic components such as resistors, transistors and condensators, ii) feed units as accumulators, solar cells, galvanic elements operating on temperature differences and batteries, iii) hybrid circuits, iv) resistor blocks. Random combinations of parts or components are possible also.
  • the packages according to the invention can be produced in various ways.
  • the package according to the invention is produced by injection-moulding the package in one step.
  • the advantages of this process are that different kinds of plastic moulding compounds can be used, that the rate of production is high, that a constant product can be moulded having accurate, stable dimensions and that the design is virtually unlimited.
  • the die pads and the conducting paths can be applied on the moulded thermoplastic material using the appropriate techniques such as, for instance, sputtering, electrochemical treatment or a transfer technique.
  • the electrically conducting layer can be applied, if so desired, during the injection moulding using a transfer technique.
  • the choice of the electrically conducting material is determined by the technique by which the material is applied, the use of the package, the desired electrical and chemical characteristics of the material and the plastic. A few options are iron-nickel alloys, copper alloys and laminates of various materials and/or alloys.
  • the package is produced from a thermoplastic material by moulding the material mechanically and/or thermally/mechanically, upon which the package is provided with electrically conductive material in the form of layers.
  • the known moulding techniques can be applied for the moulding of the thermoplastic material.
  • the package is produced from a laminate of a substantially flat shape, which laminate consists of a thermoplastic and of an electrically conductive material, the electrically conductive material being present in the form of layers, upon which the package is moulded by moulding the laminate mechanically and/or thermally/mechanically.
  • the application of the electrically conductive material is easier and cheaper.
  • a so-called 2-D(imensional) plating technology can be applied instead of a 3-D(imensional) plating technology.
  • a further effect is that the entire production of the package is simplified.
  • the package according to the invention is preferably subjected to a thermal after-treatment, which substantially increases the adhesion between the electrically conductive material applied and the plastic. This may increase the mechanical strength of the electrically conductive material.
  • the plastic used contains a thermoplastic or thermosetting polymer, which can be subjected to an after-condensation treatment, a further effect is that the average molecular mass of the polymer increases, so that the strength and, in specific cases, the impact resistance of the plastic is enhanced. As a result, the mechanical properties of the entire package are enhanced.
  • the package according to the invention is particularly suited for automatic further processing such as automatic mounting and automatic soldering techniques. Due to the construction or design of the package according to the invention, combined with the intrinsic vibration-damping properties of plastics, the packages according to the invention are less sensitive to shocks. Owing to their reduced sensitivity to shocks, the packages according to the invention are highly suited for use in the automotive industry, the aircraft industry, the spacecraft industry and for military applications.
  • the packages according to the invention are preferably combined or stacked to form modules.
  • the package may be provided, if so desired, with electrically conductive material on both sides. It is possible also for the packages to be provided on both sides with integrated circuits and/or other discrete parts, in order to obtain the highest possible density. Discrete parts are understood not only to include electronic components, but also feed units such as accumulators, solar cells, galvanic elements using temperature differences and batteries. Such stackable packages are highly suited for use as memory modules.
  • the packages can be mounted against or on top of one another using the appropriate techniques such as the so-called click-fit or snap-fit connections, adhesive. soldering and welding techniques.
  • the welding operation can be chosen from, for instance, the category of laser welding induction welding, friction welding and ultrasonic welding. Though not necessary, preference should be given to the surface geometry of the contact faces being formed in agreement with the chosen welding technique.
  • Figure 1 is a diagrammatic representation of a cross section of a possible embodiment of a package.
  • Figure 2 is a diagrammatic representation of a rectangular package with four upright sides.
  • Figure 3 is a diagrammatic representation of a rectangular package with two upright sides.
  • Figure 4 is a diagrammatic representation of the bottom view of a rectangular package provided with four upright sides, with a stamp-like or serrated edge, and with conducting paths.
  • Figure 5 is a diagrammatic representation of a sid view of a rectangular package provided with two upright sides with a thick-thin configuration.
  • Figure 6 is a diagrammatic representation of a cross section of a possible embodiment of the package of Figure 5.
  • Figures 7 and 8 are diagrammatic representations o cross sections of possible embodiments of the package.
  • Figure 9 is a diagrammatic representation of a cross section of a possible module.
  • Figure 1 shows the basic configuration of a package, featuring the basic U-shaped form.
  • This package comprises a flat plate provided with upright sides 1, a platform (die pad) 2 which the integrated circuit is mounte on and conducting paths 3 and 4. These conducting paths constitute, on the sides, the contact points of the package with the environment.
  • Figure 2 represents a diagrammatic view of a rectangular package provided with four upright sides. Owing to the projection, only two sides are visible.
  • Figure 3 represents a diagrammatic view of a rectangular package provided with two upright sides.
  • Figure 4 basically represents a bottom view of a rectangular package comprising a plate provided with four upright sides 6.
  • the four upright sides are provided with a stamp-like or serrated edge.
  • the package is provided with electrically conductive material in the form of a platform (die pad) 5 and conducting paths 7.
  • the conducting paths extend into the points of the stamp-like or serrated edge. These points constitute the contact points of the package.
  • Figure 5 basically represents the side view of a rectangular package comprising a plate provided with two upright sides 8 and conducting paths 11.
  • the sides are provided with a thick-thin configuration. This configuration implies that the thickness of the package between two neighbouring contact points is smaller than at each individual contact point.
  • Figure 6 basically represents the configuration of the package of Figure 5 comprising a plate provided with upright sides 8, a platform 10, conducting paths 11 and 12, an integrated circuit 9 and connecting wires 13 and 14. The package is sealed with a blop top 15.
  • Figure 7 basically represents the configuration of a package comprising a plate provided with upright sides 16, a platform 18, conducting paths 19 and 20, an integrated circuit 17 and connecting wires 22.
  • the package is sealed with a sealing element provided with upright sides and an opening 21 for taking up and connecting the integrated circuit.
  • the contact faces of the upright sides of the sealing element are provided with triangular welding ridges, which makes this configuration eminently suited for ultrasonic welding techniques.
  • the sealing element is applied on the package before applying, and connecting, the integrated circuit via the opening. Thi opening in its turn can then be sealed with another sealing element (flat plate or an element for the removal of heat).
  • the space containing the integrated circuit can be filled with heat transfer medium. It will be clear that if the sealing element is not provided with an opening for the placement o an integrated circuit, said circuit is mounted before the application of the sealing element.
  • Figure 8 basically represents the configuration of a package comprising a plate provided with upright sides 24 conducting paths 28 and 29 provided with bumps 26 and 27, a integrated circuit 25 and a sealing element 30 provided wit upright sides.
  • the contact faces of the upright sides of the sealing element are provided with triangular welding ridges which makes this configuration eminently suited for ultrasonic welding techniques.
  • FIG. 9 basically represents the configuration of a module built up from three identical packages.
  • Each packages comprises a plate provided with at least one upright side 31, a conducting path 32, a die pad 33, an integrated circuit 34, a connecting wire 35 and a blob top 36.
  • the packages are provided on their sides or outsides also with electrically conductive materia in the form of layers.

Abstract

The invention relates to a package for incorporating an integrated circuit comprising a plate (1) substantially consisting of a plastic and of electrically conductive material, which plate is at least partly provided with an upright side with at least one contact point, characterized in that the upright side contains a plastic, while the electrically conductive material is applied in the form of layers (3, 4) on the plate and on the upright sides. Such a package no longer has a separate lead frame, so that the pin count is no longer limited by the lead frame. Further, owing to the design of the package, thermal fatigue is no longer critical. The packages are suited for incorporating integrated circuits and other discrete parts and/or electronic components. The packages are highly suited for stacked applications such as memory modules. The invention also relates to the process for producing such packages. The packages can be produced using an injection moulding technique, or using a mechanical and/or thermal/mechanical moulding technique in combination with a technique for applying the electrically conductive material.

Description

PACKAGE FOR INCORPORATING AN INTEGRATED CIRCUIT AND A PROCESS FOR THE PRODUCTION OF THE PACKAGE
The invention relates to a package for incorporating an integrated circuit comprising a plate substantially consisting of a plastic and of electrically conductive material, which plate is at least partly provided with an upright side with at least one contact point.
Such plastic packages for incorporating integrated circuits are generally known and are used on a large scale. See, for instance, the 'Microelectronics Packaging Handbook', chapter 8, pages 523-672 (Van Nostrand Reinhold, New York, 1989, ISBN 0-442-20578-3).
In it plastic packages are described of which the upright sides consist of metal strips projecting from the package and which may be bent, if so desired, in a particular shape. The ends of the strips further form the contact points.
The known plastic packages are substantially composed of a metal lead frame, an integrated circuit (chip or IC), very thin gold connecting wires and a plastic or plastic moulding compound.
The lead frame is the central supporting structure of the package which every other element is fastened to. A lead frame is punched from a thin metal strip or film or etched in a filigree of narrow leads projecting from a central platform (die pad). The integrated circuit is fastened to the central platform and is electrically connected with the filigree of narrow leads by means of the very thin gold wires. The ends of the narrow leads eventually form the so-called contact points. The contact points constitute those places where the electric contact is established between the package and its environment, for instance a printed circuit board (PCB) .
A disadvantage of the known plastic packages is that the so-called pin counts are limited. The pin count is the total number of leads of a package. Such a lead is referred to in technical jargon also as I/O pin (Input/Output pin). The limitation of the pin count lies particularly in the fact that the leads become too thin and too long. This causes a deterioration of the mechanical rigidity of the leads, which may therefore become bent during their encapsulation with a plastic.
Further, as the pin count rises, it will be increasingly difficult to keep the leads in one plane (coplanar leads, see 'Microelectronics Packaging Handbook', page 1136). As the pin count rises, the dimensional accuracy will play an increasingly important part, because the dimensions of the contact points become smaller and smaller. Even a small deviation may then cause one or more leads, while they are being mounted on a substrate, not to be soldered at, but beside their appropriate place.
Another disadvantage of the packages known in the art is due to the difference in thermal expansion coefficients between the frame material and the integrated circuit, the encapsulating plastic and the substrate.
Packages for integrated circuits are exposed to two kinds of heating: process cycles, which generally cause the package to be heated strongly, but a few times at most, and application cycles, which occur frequently, but with smaller temperature steps. A process cycle is understood to mean, for instance, the encapsulation of the frame with a plastic. During the cooling phase thermal strains are brought about on the interface of the frame and of the plastic and on the interface of the frame and of the integrated circuit. The thermal strains on the interfaces of the frame and plastic may result in the formation of microcracks, so that moisture can penetrate into the package. This may lead to failure of the package. On the interface between the frame and the integrated circuit the strains may result in the faulty operation of the integrated circuit. Another example of a process cycle is the soldering of the package on a substrate. During the so-called vapour phase soldering, a package is heated up to about 260oC. This, of course, causes thermal strains again at all places where the frame is in contact with another material, such as the integrated circuit, the plastic, etc.
Application cycles are understood to mean the fluctuating temperatures of a package during its lifetime. If this causes a package to fail, for instance in consequence of breakage somewhere, it is referred to as thermal fatigue. Such thermal fatigue mainly occurs at those places where two relatively rigid components (integrated circuit, frame, substrate, printed circuit) are connected with each other (see 'Microelectronics Packaging Handbook', chapter 5.5, pages 277-320, Van Nostrand Reinhold, New York, 1989 and 'Soldering in Electronics', pages 305-310,
Electrochemical Publications Ltd, 1984). Particularly at the soldered joints, thermal fatigue may occur. Signs of fatigue at the soldered joint may be due to the heat fluctuations generated in an integrated circuit during the application of such circuit, which heat is carried off to the substrate via the frame, which is a very good thermal conductor. These signs of fatigue occur at the soldered joints where the metal lead is passed through a hole in the substrate (or printed circuit) and then soldered, the so-called 'through hole technology' (THT), as well as at the soldered joints where the connection is made on the substrate, the so-called 'surface mounting technology' (SMT). Using well-designed components (for instance the leads) , the risk of a fatigue fracture can be strongly reduced, but recent research has shown that, particularly when the pin count increases, signs of fatigue at the soldered joints will again result in an increased risk of fatigue fracture (see 'Microelectronics Packaging Handbook'), page 306, lines 10-16, and page 804, figures 11-18 (Van Nostrand Reinhold, New York, 1989).
Another disadavantage of the known packages is the frequently inadequate adhesion between the frame and the encapsulating plastic. If the adhesion is insufficient, moisture may penetrate into the package. This may result in failure of the package. Particularly when thermoplastics ar used, the adhesion is very moderate. The adhesion is particularly poor if a thermoplastic liquid crystalline polymer is used as encapsulating material. Liquid crystalline polymers are polymers that have a more rigid molecular structure, unlike the traditional thermoplastics. That is why in the melted phase these polymers show a so-called nematic behaviour. Such polymers orient themselve readily in a field of current, so that on the interfaces between the polymer and the lead frame a very highly oriented layer of polymer molecules is formed. In consequence, hardly any adhesion takes place between the molecules and the frame.
Finally, a disadvantage of the known packages is that a frame may interfere with the production process and therefore cause an increase in costs. Each individual component (for instance a frame) of a composite article (fo instance the known package) must be produced and later on b combined to form the desired article. It will be clear that in every production step disturbances may occur. That is wh during the production of composite articles a maximum reduction of the number of components is generally aimed at. The object of the invention is to provide a packag that does not have said disadvantages and problems.
This object is achieved according to the invention in that the upright side contains a plastic, while the electrically conductive material is applied in the form of layers on the plate and on the upright side.
The effect is that for plastic packages no separate lead frame will be required any more, so that the pin count will no longer be limited by the frame technology. Moreover, there will no longer be any problems relating to the difference in thermal expansion coefficients of a lead frame and the integrated circuit, the plastic and the substrate. The electrically conductive material applied on the package according to the invention takes care of the electric contact between the integrated circuit and the contact points (the places where the package is in contact electrically with its environment) . These electrically conductive contact paths are called conducting paths. These conducting paths may be very thin. Thin conducting paths are ductile, yielding, so that, owing to the interaction of the conducting paths and the plastic, thermal strains caused by the differences in expansion coefficients are absorbed by elastic deformations. As a result, the thermal strains at each contact face between conducting path and plastic and at each contact face between platform and integrated circuit are reduced to an absolute minimum. Owing to the combination of thin conducting paths, the intrinsic properties of the plastic material, the shape of the upright side and the reduced heat transmission, an elastic soldered connection is formed at the contact points which is not critically prone to thermal fatigue.
It should be pointed out that a type of plastic package is known that does not incorporate a frame, but whose conducting paths constitute at least in part the contact points, the so-called plastic frameless packages. See for instance: 'Application of Liquid Crystal Polymer for Molded Circuit Component', Gosei Jushi (Synthetic Resin), vol. 35, no. 8, 28 ff., 1989. Such frameless plastic packages are called plastic leadless chip carriers (PLLCC). Another name by which such package is referred to is moulded interconnection device (MID). Such PLLCCs are intended to be mounted and soldered on the surface of a substrate (SMT) . It here concerns a frame provided with conducting paths extending via the side to the underside of the frame.
The disadvantage of these known frameless packages (PLLCCs) is that the soldered connection between the package and the substrate is rigid. This causes thermal strains between the package and the substrate during the soldering and during use, which may give rise to thermal fatigue. This is due to the fact that the contact points are situated on the rigid part of the package. Other disadvantages of the known frameless packages are the production of such packages, which is realized through the so-called two-shot moulding process, that is two-step injection moulding, and the patternization of the conducting paths, which is limited to a particular fixed form (outline). Further, the moulds for the production of the known frameless packages are complicated. The plate and the upright side(s) of the package according to the invention will usually be of the same plastic material.
The advantage is that the plate and the side(s) can be made in one production step. The package according to the invention is suited for various kinds of soldering technique such as, for instance, the 'through hole technology' and the 'surface mounting technology' . If so desired, the packages according to the invention can also be connected with a substrate via a so-called connector.
The die pads and the conducting paths can be applied to the thermoplastic material by the appropriate techniques such as, for instance, sputtering, an electrochemical treatment or a transfer technique. The choice of the electrically conductive material is determined by the technique used in applying the material, the use of the package, the desired electrical and chemical characteristics of the material, the plastic and the cost of the package. Some options are, for instance, iron-nickel alloys, copper alloys and laminates of various metals and/or alloys. The person skilled in the art will be able to find the most suitable material.
The plastic from which the package according to the invention is produced can basically be chosen from all thermoplastics or thermosetting plastics known in the art. These are understood also to include all plastic compositions based on such plastics, such as blends and compounds. The choice of a particular plastic or plastic moulding compound is substantially determined by the basic criteria which plastics or plastic moulding compounds must comply with if applied in packages for integrated circuits. Some basic criteria are the melt viscosity, the dimensional stability, the thermal stability, the possibility of metallizing the surface and a low moisture absorption. Suitable plastics can be chosen from the category of high-grade thermoplastic engineering plastics such as, for instance, polyether etherketone, polyether ketone, polyamide imide, polyamides, polyphenylene sulphide, polyethylene halides such as polytetrafluoroethylene, polyether sulphone, aromatic polyesters, aromatic polyester amides and polyester carbonates. Preference is given to choosing the plastic from the group of aromatic polyesters, polyester amides or polyester carbonates, which are of a liquid, crystalline nature in the melted phase, the so-called liquid crystalline polymers (LCPs). Liquid crystalline polymers are known for their good (gas-)barrier properties, low expansion coefficients, good flow behaviour, low flammability (no flame retardants required), chemical inertness, thermal stability and the possibility of metallizing (preplating) the surfaces. A plastic moulding compound of a liquid crystalline character may comprise, fo instance:
- 20-70% (wt) monomeric units obtained from parahydroxybenzoic acid,
- 5-50% (wt) monomeric units obtained from biphenol and/or hydroquinone,
- 5-50% (wt) monomeric units obtained from terephthalic and/or isophthalic acid, and
- 1-60% (wt) fillers.
Other suitable plastics are the thermosetting plastics such as, for instance, epoxy resins and bismaleimide resins.
Packages according to the invention produced from the above-mentioned plastic moulding compounds have a high chemical and thermal inertness and are therefore resistant against the high temperatures encountered in the customary soldering techniques, such as vapour phase soldering. The properties of the chosen plastic can be influenced, if so desired, by compounding the plastic with fillers such as, for instance, silica, alpha-quartz, aluminium oxide, carbon, fused silica, kaolin, talcum, wollastonite and/or combinations of these.
A special advantage of the package according to the invention is that the possibilities in respect of the dimensions and the design of the package are virtually unlimited. Now, with the essential conditions defined (for instance, a defined plastic moulding compound or a defined permissible thermal expansion/shrinkage of the total package), it will be possible for a design to be found having optimum properties for the present application. Optimum properties may, for instance, be a defined elastic deformation under strain in 2 or 3 dimensions or a certain degree of flexibility. It is likewise possible to produce packages for one particular application containing different plastics or plastic moulding compounds. These plastics and/or plastic moulding compounds will generally have different intrinsic properties. The chosen plastics and/or plastic moulding compounds may further show an isotropic mechanical behaviour with a high or a low thermal expansion coefficient, but also an anisotropic mechanical behaviour such as, for instance, in the use of liquid crystalline polymers. Through a relatively simple modification of, for instance, the injection mould, different plastics or plastic moulding compounds can be used for that particular application, while the package will always have the optimum properties for each specific purpose. A person skilled in the art will be able to find a plastic or plastic moulding compound that complies with the mechanical, rheological, thermal, dielectric and chemical requirements set by him and to find the most suitable form or geometry of the package to match the chosen plastic, because the package according to the invention is not in any way limited by dimension and/or design.
Another special advantage of the package is that the upright sides may become wider as seen from the plate, so that the distances between the contact points are greater than the distances between the conducting paths. This configuration has major advantages if the pin counts are very high and the soldered connections at the contact points are therefore situated close together. A second advantage of such a configuration is that the package can be modified to comply with the various requirements in respect of the place of and the distances between the contact points. The dimensions of the packages according to the invention can then be modified in a simple manner to comply with the essential conditions defined. Another special advantage of the package according to the invention is that its design makes it possible for all contact points to be kept in one plane (coplanar). As the contact points are situated on the upright sides, they are fixed in space. This makes it impossible for the contact points, during the assembly of a package, when the pin count rises, to reach the substrate beside their appropriate place
It is possible also for the package according to the invention to be produced in one step without inserts, using an injection moulding technique. This is a great advantage compared with the known packages.
The packages according to the invention are highly suited for incorporating a plurality of integrated circuits. Thanks to the constructional freedoms of the package according to the invention, a plurality of platforms (die pads) can be applied.
The platforms can be interconnected, if so desired, by conducting paths, which take care of the contacts between the platforms. The application of a plurality of platforms does not involve any problem in so far as it concerns the technique (for instance sputtering, electrochemical, transfer technique) of applying the platforms and conducting paths on the plastic.
The package according to the invention may further be, or come to be, provided with constructional elements such as elevations or recesses enhancing the ease of handling the package during the production process such as, for instance, centring during the application and connection of an integrated circuit.
The package according to the invention may be, or come to be, provided with additional upright sides allowing the package to be sealed with a sealing element. Particularly suited is a sealing element provided with upright sides, so that the additional upright sides on the package need not be provided, if so desired. The joint between the upright sides and the sealing element may, for instance, be glued or welded. The welding operation may be chosen from, for instance, the category of laser welding. induction welding, friction welding and ultrasonic welding. Preferably the cross section of the package is substantially U-shaped. The packages according to the invention are U-shaped if all additional constructional elements are left out of consideration. Constructional elements are understood to mean all elevations, recesses and upright sides as described above. The effect is that the basic geometry of the package is basically simple, mechanically very stable, constructionally easy to produce, capable of being easily modified for specific uses and that there is basically perfect freedom in choosing the dimensions. Using the appropriate techniques the shape can further be modified to suit the chosen plastic or plastic moulding compound, so that an optimum behaviour is obtained near the contact points. Optimum behaviour may, for instance, be a defined elastic deformation under strain in 2 or 3 dimensions, or a certain degree of flexibility.
The geometry of the package in the vicinity of the contact points is preferably such as to suit the plastic in the package, so that a defined flexibility is obtained, reducing thermal effects during the soldering to an absolute minimum, and thermal fatigue does not play a critical role. A plastic or plastic moulding compound has specific intrinsic properties. The chosen plastic or plastic moulding compound may, for instance, show an isotropic mechanical behaviour with a high or a low thermal expansion coefficient, but also the anisotropic mechanical behaviour of, for instance, the liquid crystalline polymers.
Further, with essential conditions defined (for instance, defined plastic moulding compound and/or defined thermal expansion/shrinkage of the total package), it is possible for a design to be found with the optimum properties for the present application.
Beside a straight geometry, preference is given to a geometry which substantially looks like the edge of a stamp or a serrated edge. Another preferred geometry is the so-called thick-thin configuration. Here the thickness of the package between two neighbouring contact points is smaller than at each of the individual contact points.
Through such constructional measures the flexibility obtained at the contact points may be such as t allow the contact points under changing thermal conditions to move with the expansion or shrinkage of the substrate without mechanical strains arising. If so desired, a particular soldering technology may be taken into account i designing the geometry of the package near the contact poin The integrated circuit can be applied in the package and be connected by means of existing technologies. Depending on the manner in which the package is sealed or closed, the moment of applying and connecting the integrate circuit can be chosen freely. This makes it possible for the integrated circuit to be applied later on in the production process. This may be an advantage particularly when expensive integrated circuits are used, because the risk of failure is reduced. A special advantage of the package according to the invention is that, when the so-called flip-chip techniques are used, the required 'bumps', as they are called, can be applied on the conducting paths of the package, so that standard integrated circuits can be used. This contrasts with existing flip-chip systems, where the bumps must be applied on the integrated circuits. Such integrated circuits are very expensive. See for existing flip-chip techniques, for instance, 'Multichip Assembly with Flipped Integrated Circuits', IEEE Transactions on Components, Hybrids and Manufacturing Technology, vol. 12, no. 4, pages 650-657, December 1989. The package according to the invention preferably has a plate provided all along its perimeter with an uninterrupted upright side. The integrated circuit is preferably covered with a sealing element. The choice of the material of the sealing element is not critical. Examples are: metal, ceramics or a plastic.
In this way a hermetically sealed package can be obtained providing optimum protection for the integrated circuit against influences from the invironment. Depending on an application, a sealing element may be chosen comprising metal, ceramics or a plastic. Particularly suited is a sealing element provided with upright sides allowing the additional upright sides on the package to be omitted, if so desired. Though not necessary, it is possible to improve the quality of the weld by bringing the surface geometry of the contact faces in agreement with the chosen welding technique. It is known, for instance, that in order to obtain an optimum joint in the ultrasonic welding of plastics, the contact faces must be of a particular shape. The most simple shapes, which can be used for amorphous as well as semi-crystalline polymers, are the triangular and the trapezium-shaped ridges on a flat opposite surface (the so-called butt joint). It is further known that for the ultrasonic welding of more crystalline polymers the so-called scarf joint and the so-called shear joint give better results, see F.C. Jaarsma, S.P.E. ANTAC Congress, 1982, Ultrasonic Welding of Crystalline Thermoplastic Injection. However, it is possible also for the above-mentioned welding ridges to be welded precisely onto each other such as, for instance, a triangular welding ridge on a triangular welding ridge or a trapezium-shaped welding ridge on a trapezium-shaped welding ridge, or a combination of these. If so desired, the package and/or the sealing element may be provided with a plurality of such upright sides.
Another preferred embodiment for sealing a package according to the invention is the sealing by means of blob-top. The effect of this technique is that for many applications the integrated circuit is adequately protected against influences from the environment, while the speed of producing such packages increases with a simultaneous decrease of costs, compared with packages provided with a sealing element comprising metal, ceramics or a thermoplastic. Blob-top is the sealing of an integrated circuit using silicone gel or an epoxy. See, for instance, 'Die Losung gegen Stre ', Productronic, vols 7/8, pages 76-77, 1989.
The package according to the invention is preferably provided with one or more inserts. Possible inserts are, for instance, an element for fastening the package such as, for instance, a screw attachment, an element for the removal of heat or an element for incorporating a battery, for instance.
All packages described above are preferably provided with an element for the removal of heat.
The effect of it is that, in the integrated circuit, the removal of the generated heat to the environment is improved, so that the circuit will not be too hot. Such an element is called 'heat sink'. In view of the high degree of constructional freedom of the basic shape of the package according to the invention, a great many variations are possible on the shape and on the number of such elements, as well as on the places where such elements can be applied. If during its use the integrated circuit produces so much heat that the removal of the heat is insufficient, so that the integrated circuit will be too hot, preference is given to providing the sealed spaces of the suitable embodiments with a heat dissipation medium. This will improve the removal of the heat generated in the integrated circuit to the environment.
Another preferred embodiment of a package according to the invention is that the package is provided with ducts for the removal of heat. This makes it possible for the temperature of the package to be regulated arbitrarily, independently of the heat generated and/or of the ambient temperature.
The packages according to the invention are highly suited for incorporating, beside one or more integrated circuits, additional discrete parts or components. Discrete parts or components are, for instance, eletcronic parts such as resistors, transistors and/or condensators and, for instance, feed units such as accumulators, solar cells, galvanic elements operating on temperature differences and/or batteries. Random combinations of parts are possible also.
The packages according to the invention are suited also for incorporating parts or components other than integrated circuits.
Suitable components are, for instance, i) electronic components such as resistors, transistors and condensators, ii) feed units as accumulators, solar cells, galvanic elements operating on temperature differences and batteries, iii) hybrid circuits, iv) resistor blocks. Random combinations of parts or components are possible also. The packages according to the invention can be produced in various ways.
According to one preferred mode of realization, the package according to the invention is produced by injection-moulding the package in one step. The advantages of this process are that different kinds of plastic moulding compounds can be used, that the rate of production is high, that a constant product can be moulded having accurate, stable dimensions and that the design is virtually unlimited. The die pads and the conducting paths can be applied on the moulded thermoplastic material using the appropriate techniques such as, for instance, sputtering, electrochemical treatment or a transfer technique. The electrically conducting layer can be applied, if so desired, during the injection moulding using a transfer technique. The choice of the electrically conducting material is determined by the technique by which the material is applied, the use of the package, the desired electrical and chemical characteristics of the material and the plastic. A few options are iron-nickel alloys, copper alloys and laminates of various materials and/or alloys.
According to a second mode of realization, the package is produced from a thermoplastic material by moulding the material mechanically and/or thermally/mechanically, upon which the package is provided with electrically conductive material in the form of layers. For the moulding of the thermoplastic material, the known moulding techniques can be applied.
An advantage of this process is that, compared with the injection moulding of such packages, no injection mould is needed and that the rate of production can be increased. According to a third mode of realization, the package is produced from a laminate of a substantially flat shape, which laminate consists of a thermoplastic and of an electrically conductive material, the electrically conductive material being present in the form of layers, upon which the package is moulded by moulding the laminate mechanically and/or thermally/mechanically.
In such a process the application of the electrically conductive material is easier and cheaper. A so-called 2-D(imensional) plating technology can be applied instead of a 3-D(imensional) plating technology. A further effect is that the entire production of the package is simplified. For the moulding of the laminate by means of a mechanical and/or thermal moulding technique, techniques can be used generally known in the art for the moulding of plastics. Before the application of the integrated circuit, the package according to the invention is preferably subjected to a thermal after-treatment, which substantially increases the adhesion between the electrically conductive material applied and the plastic. This may increase the mechanical strength of the electrically conductive material. If the plastic used contains a thermoplastic or thermosetting polymer, which can be subjected to an after-condensation treatment, a further effect is that the average molecular mass of the polymer increases, so that the strength and, in specific cases, the impact resistance of the plastic is enhanced. As a result, the mechanical properties of the entire package are enhanced.
The package according to the invention is particularly suited for automatic further processing such as automatic mounting and automatic soldering techniques. Due to the construction or design of the package according to the invention, combined with the intrinsic vibration-damping properties of plastics, the packages according to the invention are less sensitive to shocks. Owing to their reduced sensitivity to shocks, the packages according to the invention are highly suited for use in the automotive industry, the aircraft industry, the spacecraft industry and for military applications.
The packages according to the invention are preferably combined or stacked to form modules. To this end the package may be provided, if so desired, with electrically conductive material on both sides. It is possible also for the packages to be provided on both sides with integrated circuits and/or other discrete parts, in order to obtain the highest possible density. Discrete parts are understood not only to include electronic components, but also feed units such as accumulators, solar cells, galvanic elements using temperature differences and batteries. Such stackable packages are highly suited for use as memory modules. The packages can be mounted against or on top of one another using the appropriate techniques such as the so-called click-fit or snap-fit connections, adhesive. soldering and welding techniques. The welding operation can be chosen from, for instance, the category of laser welding induction welding, friction welding and ultrasonic welding. Though not necessary, preference should be given to the surface geometry of the contact faces being formed in agreement with the chosen welding technique.
The invention will be elucidated with reference to the attached figures without being limited thereto.
Figure 1 is a diagrammatic representation of a cross section of a possible embodiment of a package.
Figure 2 is a diagrammatic representation of a rectangular package with four upright sides. Figure 3 is a diagrammatic representation of a rectangular package with two upright sides.
Figure 4 is a diagrammatic representation of the bottom view of a rectangular package provided with four upright sides, with a stamp-like or serrated edge, and with conducting paths.
Figure 5 is a diagrammatic representation of a sid view of a rectangular package provided with two upright sides with a thick-thin configuration.
Figure 6 is a diagrammatic representation of a cross section of a possible embodiment of the package of Figure 5.
Figures 7 and 8 are diagrammatic representations o cross sections of possible embodiments of the package. Figure 9 is a diagrammatic representation of a cross section of a possible module.
Figure 1 shows the basic configuration of a package, featuring the basic U-shaped form. This package comprises a flat plate provided with upright sides 1, a platform (die pad) 2 which the integrated circuit is mounte on and conducting paths 3 and 4. These conducting paths constitute, on the sides, the contact points of the package with the environment. Figure 2 represents a diagrammatic view of a rectangular package provided with four upright sides. Owing to the projection, only two sides are visible.
Figure 3 represents a diagrammatic view of a rectangular package provided with two upright sides.
Figure 4 basically represents a bottom view of a rectangular package comprising a plate provided with four upright sides 6.
The four upright sides are provided with a stamp-like or serrated edge. The package is provided with electrically conductive material in the form of a platform (die pad) 5 and conducting paths 7. The conducting paths extend into the points of the stamp-like or serrated edge. These points constitute the contact points of the package.
Figure 5 basically represents the side view of a rectangular package comprising a plate provided with two upright sides 8 and conducting paths 11. In this case, the sides are provided with a thick-thin configuration. This configuration implies that the thickness of the package between two neighbouring contact points is smaller than at each individual contact point.
Figure 6 basically represents the configuration of the package of Figure 5 comprising a plate provided with upright sides 8, a platform 10, conducting paths 11 and 12, an integrated circuit 9 and connecting wires 13 and 14. The package is sealed with a blop top 15.
Figure 7 basically represents the configuration of a package comprising a plate provided with upright sides 16, a platform 18, conducting paths 19 and 20, an integrated circuit 17 and connecting wires 22. The package is sealed with a sealing element provided with upright sides and an opening 21 for taking up and connecting the integrated circuit. The contact faces of the upright sides of the sealing element are provided with triangular welding ridges, which makes this configuration eminently suited for ultrasonic welding techniques. In this configuration, the sealing element is applied on the package before applying, and connecting, the integrated circuit via the opening. Thi opening in its turn can then be sealed with another sealing element (flat plate or an element for the removal of heat).
If so desired, in order to completely seal the package, the space containing the integrated circuit can be filled with heat transfer medium. It will be clear that if the sealing element is not provided with an opening for the placement o an integrated circuit, said circuit is mounted before the application of the sealing element.
Figure 8 basically represents the configuration of a package comprising a plate provided with upright sides 24 conducting paths 28 and 29 provided with bumps 26 and 27, a integrated circuit 25 and a sealing element 30 provided wit upright sides.
The contact faces of the upright sides of the sealing element are provided with triangular welding ridges which makes this configuration eminently suited for ultrasonic welding techniques.
In such a configuration the integrated circuit is applied with a flip chip technique, upon which the package is sealed with a sealing element. Figure 9 basically represents the configuration of a module built up from three identical packages. Each packages comprises a plate provided with at least one upright side 31, a conducting path 32, a die pad 33, an integrated circuit 34, a connecting wire 35 and a blob top 36. In such a package, the packages are provided on their sides or outsides also with electrically conductive materia in the form of layers.

Claims

C L A I M S
1. Lead frame for supporting a chip with leads consisting of a frame made of plastic and leads in the form of strips of electrically conductive material applied on the plastic frame.
2. Lead frame according to claim 1, characterized in that the plastic material is flexible.
3. Lead frame according to claim 1, characterized in that the frame is of an approximately rectangular shape with upright sides.
4. Lead frame according to claim 3, characterized in that the upright side has pointed parts and that leads end in the points.
5. Lead frame according to claims 1-4, characterized in that the frame incorporates an insert.
6. Lead frame according to claim 5, characterized in that the insert is an element removing heat.
7. Lead frame according to claims 1-6, characterized in that the parts of the upright side between the leads are chosen to be thicker than at the leads.
8. Lead frame according to claims 1-7, characterized in that the frame has a sealing element on the side facing the chip.
9. Lead frame according to claims 1-8, characterized in that the plastic contains a liquid crystalline polymer.
PCT/NL1991/000132 1990-07-25 1991-07-22 Package for incorporating an integrated circuit and a process for the production of the package WO1992002040A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
NL9001690 1990-07-25
NL9001690 1990-07-25

Publications (1)

Publication Number Publication Date
WO1992002040A1 true WO1992002040A1 (en) 1992-02-06

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Application Number Title Priority Date Filing Date
PCT/NL1991/000132 WO1992002040A1 (en) 1990-07-25 1991-07-22 Package for incorporating an integrated circuit and a process for the production of the package

Country Status (1)

Country Link
WO (1) WO1992002040A1 (en)

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EP0698921A3 (en) * 1994-08-26 1996-10-23 Hughes Aircraft Co Layered features for co-fired module integration
WO1997015078A1 (en) * 1995-10-16 1997-04-24 Siemens N.V. Polymer stud grid array
WO1997015077A1 (en) * 1995-10-16 1997-04-24 Siemens N.V. Polymer stud-matrix housing for microwave circuit arrangements
EP0840369A1 (en) * 1995-06-30 1998-05-06 Kabushiki Kaisha Toshiba Electronic component and method of production thereof
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US5639990A (en) * 1992-06-05 1997-06-17 Mitsui Toatsu Chemicals, Inc. Solid printed substrate and electronic circuit package using the same
EP0598914A4 (en) * 1992-06-05 1994-11-23 Mitsui Toatsu Chemicals Three-dimensional printed circuit board, electronic circuit package using this board, and method for manufacturing this board.
EP0598914A1 (en) * 1992-06-05 1994-06-01 MITSUI TOATSU CHEMICALS, Inc. Three-dimensional printed circuit board, electronic circuit package using this board, and method for manufacturing this board
EP0698921A3 (en) * 1994-08-26 1996-10-23 Hughes Aircraft Co Layered features for co-fired module integration
EP0840369A4 (en) * 1995-06-30 2001-12-19 Toshiba Kk Electronic component and method of production thereof
EP0840369A1 (en) * 1995-06-30 1998-05-06 Kabushiki Kaisha Toshiba Electronic component and method of production thereof
US6628043B2 (en) 1995-06-30 2003-09-30 Kabushiki Kaisha Toshiba Electronic component and method of production thereof
US6754950B2 (en) 1995-06-30 2004-06-29 Kabushiki Kaisha Toshiba Electronic component and method of production thereof
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WO1997015078A1 (en) * 1995-10-16 1997-04-24 Siemens N.V. Polymer stud grid array
DE10345464A1 (en) * 2003-09-30 2005-05-04 Infineon Technologies Ag Multi-chip housing has carrier substrate with terminal line regions for connecting semiconductor chip metallization contacts with printed circuit board contact surfaces acting as encapsulation housing

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