DE102014215377A1 - Method for producing double-sided metallized ceramic substrates - Google Patents

Abstract

Disclosed is a method of making a double-sided metallized ceramic substrate in which the ceramic substrate and metal layers are tilted and / or domed during manufacture.

Description

The present invention relates to a method for producing a double-sided metallized ceramic substrate, to the double-sided metallized ceramic substrates obtainable by this method, and to carriers used in the method according to the invention for producing the double-sided metallized ceramic substrates.

Double-sided metallized ceramic substrates are used in the field of power semiconductor modules. In this case, a ceramic substrate is provided on the top and bottom with a metallization, wherein usually at least one metallized side later has a generated, for example, by etching processes circuit structure. The known method for producing these double-sided metallized ceramic substrates is by eutectic bonding and is commonly referred to as a direct-bonding process.

Basic descriptions of methods of making metallized ceramic substrates by bond processes can be found in the references US 3,744,120 . US 3,994,430 . EP 0 085 914 A or the DE 23 19 854 A are taken from, the corresponding disclosure of which is incorporated by reference into the present invention. This known production method is common, for example in the context of the direct copper bonding process (DCB process), that a copper foil is first oxidized in such a way that a substantially uniform copper oxide layer results. The resulting copper foil is then positioned on a ceramic substrate and the ceramic substrate / copper foil composite is heated to a bonding temperature between about 1025-1083 ° C, thereby forming a metallized ceramic substrate. Finally, the resulting metallized ceramic substrate is cooled.

The implementation of the bonding of ceramic substrate and metal foil is generally carried out in so-called bonding ovens. Corresponding bonding ovens, often referred to as tunnel ovens include, inter alia, an elongated tunnel-like furnace chamber (also called muffle) and a transport device with a transport element, for example in the form of a flexible and heat-resistant conveyor belt for transporting the material to be treated by the heated furnace with a heater chamber. The ceramic substrates are positioned together with the metal foil on a carrier on the conveyor belt and then passed through in the bonding oven by the conveyor belt driven a heating area in which the required bonding temperature is reached. At the end of the bonding process, the resulting composite of ceramic substrate and metal foil is cooled again.

The production of double-sided metallized substrates can take place either via a two-stage bonding process or alternatively via a one-step bonding process.

In the two-step bonding process for making double-sided metallized ceramic substrates, the ceramic is bonded in two furnace passes to the metal layers on opposite sides of the ceramic substrate. For this purpose, a ceramic substrate is first positioned on a support and then placed on the overhead, d. H. By the action of heat, the side of the ceramic substrate is connected to the metal layer and then the resulting assembly is cooled. Subsequently, the substrate is turned over and in a second bonding step, the other side of the substrate is provided in the same way with a metal layer. Therefore, all metallized ceramic substrates produced in a two-step bonding process pass through the tunnel kiln twice.

In the case of the coating of the second substrate side, the metal layer already formed on the ceramic substrate in the first bonding step generally rests on the carrier, and due to the required bond heat for the second metallization, this already formed first metal layer can also be melted. In this case, misalignments in the initially formed metal layer on the ceramic substrate may result, as it usually comes to interactions between the partially melted first metal layer and the carrier on which the first formed metal layer with the substrate is. Corresponding misalignments can result, for example, from residues of the carrier material or other foreign bodies which hope for the molten metal layer after removal from the carrier.

To avoid this disadvantage of the known methods for producing double-sided metallized substrates, the use of carriers has been proposed in which the already one-sided Bonded substrates are fixed on carriers so that there is no direct contact of the already bonded ceramic surface with other surfaces, such as the carrier or conveyor belt, in the second bonding step. This is done for example by the use of carriers in which the substrates bonded on one side only rest on a carrier at the edges or are supported on narrow supports on the short sides of the substrates. Corresponding carriers - also called bond boats - are in the 1a and 1b shown.

However, the double-sided metallized substrates produced with the aid of these so-called bond boats also have disadvantages. For example, when using bond boats according to 1a with sloping supports 2 to the problem that already twisted substrates 1 slip into a position of the lowest center of gravity and thus further amplifies the already resulting from the ceramic substrate or first process step torsion. At the in 1b illustrated embodiment of bond carriers, in which the substrate 1 on edges 3 rests, is again disadvantageous that the substrates on the bottom can come in contact with, for example, the transport chain on which they are supported by the furnace, which will also result in quality losses.

Furthermore, on the ceramic side, which is not bonded in the first process run, deposit kiln dust, which then leads to malpositions in the second metallization.

Furthermore, these conventional two-stage bonding methods for producing double-sided metallized substrates have the disadvantage that the substrates have to be processed twice in succession, which is disadvantageous from a procedural economic point of view.

Another disadvantage of the known methods of the prior art is the hitherto insufficient positional accuracy of the metal layer and the substrate, in particular in the second bonding step.

To circumvent these disadvantages of the two-step process for making double-sided metallized substrates, methods have been developed for simultaneously double-sided bonding of metal layers to substrates. These methods perform simultaneous bonding of the metal layers in only one process step on both sides of the ceramic substrate.

For example, describes the DE 10 2010 023 637 A a method for producing double-sided metallized substrates in a single method step, wherein a first metal layer, a substrate and a second metal layer are sequentially positioned in a given order on a support, wherein the carrier at the top, that of the arrangement of the first and second Metal plate and facing the substrate, having a plurality of projecting lugs, which taper in the direction of the arrangement of the first and second metal plate and the substrate. According to the statement DE 10 2010 023 637 A Due to the structuring of the carrier with tips, it is achieved that the composite of metal plates and ceramic substrate can be detached from the carrier without residue after the two-sided bonding process. This is intended to prevent damage to the metal layer which rests on the carrier during the bonding process. Nevertheless, at the points of contact between the projecting lugs and the metal layer to be bonded, there are still adverse interactions, and particularly with the use of nitridic ceramics based materials, e.g. B. AlN it comes to a superficial oxidation and thus possibly to a compound with the metal foil to be bonded.

The DE 10 2004 056 879 A relates to a method for producing double-sided metallized ceramic substrates using the direct bonding process, wherein an array of at least two metal layers and a ceramic substrate disposed between the metal layers is positioned on a release coated carrier and then the array is heated to a temperature at which it comes to a bonding of the two metal layers with the ceramic substrate. The use of a corresponding separating layer should not lead to a connection of the carrier to the adjacent metal layer of the arrangement.

The DE 10 2004 056 879 A focusses on the use of particularly flat carriers which have a deviation from an ideally flat plate of less than 0.2% of the carrier length and / or less than 0.1% of the carrier width. These particularly high demands on the carrier to succeed in the production of particularly flat double-sided metallized ceramic substrates. Nonetheless, the resulting double-sided metallized ceramic substrates have a residual bend whose orientation is undefined.

In addition, assuming a continuous process for producing double-sided metallized ceramic substrates, the orientation of the residual bend will vary from device to device.

The reason for the varying nonspecific residual bending, for example, is due to raw material influences that are noticeable. The deflection of the resulting double-sided metallized ceramic substrates therefore varies even when using in the DE 10 2004 056 879 A described approach both in the longitudinal / transverse direction and in height considerably and is also unoriented.

In addition, the resulting double-sided metallized ceramic substrates fabricated with asymmetric metal thicknesses (for example, 0.3 mm metal front side and 0.2 mm metal back metal) have an in-bonding capability due to the different metal volumes on both sides of the substrate after bonding Longitudinal and transverse undefined bending, wherein the thicker metal layer is usually formed on the concave side.

In addition to this deflection problem, the positional accuracy of both metal layers to ceramic is disadvantageous in the above-mentioned prior art methods. Industrial fabrication of double-sided metallized ceramic substrates according to the above-mentioned prior art methods does not involve a step of aligning the two metal layers and the substrate with each other. If, for example, the two metal layers are not positioned exactly flush on the substrate, arrangements of the respective methods result, for example, in which the metal layers extend beyond the edge of the ceramic substrate. These excess metal residues, which lead to further problems in the downstream process steps, then have to be removed, for example, by etching again and also lead to an unnecessary material scrap.

The variations in the specifications of the resulting double-sided metallized ceramic substrates resulting from these problems of the prior art, in particular deflection and inaccurate positioning of the metallizations, can bring about considerable negative effects in the subsequent processes as well as the processing and are therefore preferably to be avoided.

On the basis of this prior art, the present invention thus first of all sets itself the general task of remedying the disadvantages of the prior art discussed above.

In particular, the present invention has the object to provide a method for producing double-sided metallized ceramic substrates, wherein the bonding process can preferably be carried out in one stage and thus simultaneously on both sides of the ceramic substrate.

Furthermore, the present invention has the object to provide a method for producing double-sided metallized ceramic substrates, in which preferably the position accuracy of metal layer to ceramic is improved.

Furthermore, the present invention has the object to provide a method for producing double-sided metallized ceramic substrates, wherein the resulting double-sided metallized ceramic substrates a defined, d. H. have substantially constant deflection, which plays a role in particular in a subsequent system soldering or chip soldering or when used in a bottomless module.

• (1) Positionieren von einer Anordnung, umfassend zumindest eine erste Metallschicht, zumindest eine zweite Metallschicht und ein zwischen der ersten und zweiten Metallschicht angeordnetem Keramik-Substrat, auf einem Träger;
• (2) Erhitzen der aus dem Verfahrensschritt (1) resultierenden Anordnung auf eine Temperatur, so dass es zu einem Verbund aus dem Keramik-Substrat und den zwei anliegenden Metallschichten durch Bonden unter Ausbildung eines doppelseitig metallisierten Keramik-Substrats kommt.

This object is achieved by a method for producing a double-sided metallized ceramic substrate, which is characterized by the following method steps:

• (1) positioning an assembly comprising at least a first metal layer, at least one second metal layer, and a ceramic substrate disposed between the first and second metal layers on a support;
• (2) heating the assembly resulting from the process step (1) to a temperature such that bonding of the ceramic substrate and the two adjacent metal layers by bonding to form a double-sided metallized ceramic substrate.

The method according to the invention is then characterized in that, in method step (1), the carrier is inclined and / or curved before the positioning of the arrangement and / or the carrier in method step (1) after the positioning of the arrangement on the carrier and / or during the process step (2) is tilted. It can also be a pivoting movement up to a zero slope or an inclination to a negative angle comes here in question.

In the context of the present invention, metal layers are, for example, metal foils or metal sheets made of copper, of a copper alloy or of a copper-containing alloy or of aluminum, of an aluminum alloy or of an aluminum-containing alloy.

"Ceramic substrates" in the context of the present invention are made of a ceramic material, preferably plate-shaped elements, which are provided on two of their surface sides with a metallization or are.

In the context of the present invention, an arrangement is understood as meaning a composite of two metal layers between which a ceramic substrate is provided, wherein the arrangement may be present before, during or after the bonding.

The term "essentially" in the context of the invention means deviations from the respective exact value by +/- 10%, preferably by +/- 5% and / or deviations in the form of changes insignificant for the function.

Further developments, advantages and applications of the invention will become apparent from the following description of exemplary embodiments and from the figures. In this case, all described and / or illustrated features alone or in any combination are fundamentally the subject of the invention, regardless of their summary in the claims or their dependency. Also, the content of the claims is made an integral part of the description.

In a first embodiment, the method according to the invention provides that the arrangement comprising the at least two metal layers and the ceramic substrate arranged therebetween is inclined before or during actual bonding in method step (2). This inclination of the arrangement can take place in that the carrier on which the arrangement of the two metal layers and the interposed ceramic substrate is positioned, after the positioning of the arrangement is either mechanically inclined or at the time at which the arrangement of the Both metal layers and the interposed ceramic substrate is positioned on the support is already inclined. Should it be provided that the carrier is tilted after the positioning of the arrangement, tilting of the carrier may occur both in process step (1), i. H. before heating the assembly, or in process step (2), d. H. during the heating of the arrangement.

Due to the inclination of the carrier, there is a defined alignment of the two metal layers and the interposed ceramic substrate with each other:
The two metal layers and the ceramic substrate slip by the inclination of the carrier in a predetermined position, so that their arrangement is considered to be defined each other. Therefore, with the method according to the invention double-sided metallized ceramic substrates can be produced, which in their entirety have a defined and constant orientation of the two metal layers and the ceramic substrate to each other.

In addition, due to the inclination of the carrier, a fixation of the two metal layers and of the ceramic substrate arranged therebetween is achieved in such a way that slippage in the subsequent method steps is avoided.

The inventive method provides in a further second embodiment that the carrier has a curvature. In the subsequent bonding process in method step (2), the arrangement positioned on the support, comprising the at least two metal layers and the ceramic substrate arranged therebetween, will approach the curvature of the support under the influence of corresponding bonding temperatures, whereby a total of curved double-sided metallised layers Ceramic substrates are formed, but in their entirety have a defined and constant curvature. The inventive method, it is thus possible to produce reproducible double-sided metallized ceramic substrates in series, the deflection in both the z-direction (height) and in the x and y directions (longitudinal and transverse directions) is clearly defined. This reproducible deflection in height as well as longitudinal and transverse direction is particularly noticeable in asymmetric material combinations, d. H. in the case of double-sided metallized ceramic substrates in which the thickness of the two metal layers on the two sides of the ceramic substrate are formed differently (eg 0.3 mm Cu / 0.38 mm ceramic / 0.25 mm Cu) ,

By combining the first embodiment (inclination) and the second embodiment (curvature), a total of two-sided metallized ceramic substrates can be produced in series, which have constant characteristics, in particular with regard to orientation of the individual layers and curvature.

The present invention therefore relates in particular to a method according to the invention which, in series production, has a multiplicity of double-sidedly metallized ceramic substrates having essentially constant properties of layer orientation and overall curvature.

In the following, the carrier used in the method according to the invention will first be discussed.

method

The inventive method for producing double-sided metallized ceramic substrates uses a carrier which is tiltable and / or inclined and / or curved. The inclination is achieved either by the design of the carrier or mechanically.

In a first variant, the carrier can be greatly tilted after placing the metal foil and the substrate, so that there is a positioning of the individual components of the arrangement. So that the spatial height of the carrier for the passage in the bonding oven is not too large, the carrier can then be approximated to a horizontal position with the then positioned components of the arrangement.

In a second variant, the carrier may already be highly inclined before the individual components of the arrangement are positioned on it, which also leads to a positioning of the individual components of the arrangement. Also in this case, the carrier with the then positioned components of the arrangement can then be approximated to a horizontal position again.

In this case, the inclination and the selection of the materials of the bonding boat are to be chosen so that it does not come to a slipping of the individual components of the arrangement in the case where the intended approach of the carrier to a horizontal position.

Corresponding carriers are also generally referred to as bond boats, bond ships or the like in the field of direct metal bonding.

The support used in the method according to the invention is preferably made of a material having high heat resistance, which is inert and / or non-wettable at the applied temperatures of the bonding process. Materials for the support according to the invention are, in particular, materials selected from the group consisting of graphite, mullite, steatite, cordierite, ZrO ₂ , Al ₂ O ₃ , AlN, BN, ZrN, Si ₃ N ₄ , SiC and mixtures thereof Question.

The support used in the process according to the invention has in particular a support plate which has a thickness of in particular 0.2 to 10 mm, preferably 1 to 7 mm, more preferably 1.5 to 5 mm.

In a first embodiment, the carrier has an inclination or is formed so that it can be inclined. Due to the inclination, after the positioning of the adjacent metal layer, the subsequent ceramic substrate layer and the final metal layer, the individual layers are positioned relative to one another. So that the arrangement remains fixed on the support, it is provided that, for example, a substantially rectangular support is provided with at least one stop on at least one of each lying by the slope below edge with a boundary. If the arrangement comprising the at least two metal layers and the ceramic substrate arranged therebetween is then positioned on the carrier, the individual layers of the arrangement can slip following the inclination of the carrier and thus abut the boundary of the carrier. As a result, a clearly defined positioning of the three layers is achieved, which thus also have a clearly defined positioning relative to one another.

In comparison, a positioning in the prior art method in which no inclination of the carrier is provided is not achieved. In the production of double-sided metallized ceramic substrates, therefore, either a very precise positioning of the two metal layers and the ceramic layer must be realized in the prior art methods, or the resulting double-sided metallized ceramic substrates have an inaccuracy in the positioning of the individual Layers to each other, which may for example lead to protruding metal layers in relation to the ceramic substrate. Such double-sided metallized ceramic substrates are then rejected after their production.

Assuming a substantially rectangular support there are several possibilities to realize a tendency of the carrier in the sense of the present invention.

The 2 shows a possible rectangular geometry of the carrier, wherein the inclination of the carrier in total rotations about the edge 5 (see. 2a ) or around the edges 8th and 9 (see. 2 B ) possible are.

In the first in 2a In the illustrated embodiment, the substantially rectangular plane of the carrier is only over one edge 5 tilted, giving a total of two corners of the rectangular support 6 and 7 result, which are located after the inclination on a substantially identical lower level.

In the in 2 B In the embodiment shown, the substantially rectangular plane of the carrier is about two edges 8th and 9 tilted, leaving a total of only one corner of the rectangular support 10 is at the lowest level.

In the context of the present invention, the in 2 B embodiment shown preferred because it allows a more accurate positioning of the individual components of the arrangement to each other due to the two-sided positioning.

According to the invention, the term "level" is preferably understood to mean the lateral plane in which the substantially rectangular plane of the carrier can be located at least partially. In this case, the "initial level", to which all other information is relative, is the level at which the substantially rectangular plane of the carrier first extends (method step (1) positioning of the carrier). All other terms of the "level" are to be understood relative to this initial level. Thus, in particular a "lower level" is understood to mean a lateral plane which is displaced in the vertical direction parallel to the plane of the initial level. Preferably, the lower level is thus lowered vertically relative to the starting level. Furthermore, in particular, a "lowest level" is understood to mean the lateral plane which is displaced in a vertical direction parallel to the plane of the initial level and in this case has the highest relative displacement in which there is still a corner of the carrier. Preferably, the lowest level is thus also lowered relative to the initial level. In this case, the lowest level always has a greater vertical displacement relative to the initial level than the lower level (according to the invention, the cases where there is only a relative vertical displacement is referred to as a case of a lower level, in which case the lower level equal to the lowest level). The out of this about the axes of rotation 8th and 9 inclined support then has an inclination, which by the in 3 illustrated angle α, β and γ will be described.

Depending on the choice of the angle α and β, an angle γ, which is generally 0.5 to 45 °, preferably 0.5 to 40 °, more preferably 0.5 to 35 °, more preferably 1 to 30 °, further preferably 1 and 25 °. The resulting angle γ must be large enough that an alignment by slipping of the metal layers and the ceramic substrate is possible, but again should not be too large, otherwise the height of the carrier used is too large and in turn the height of the tunnel kiln used would have to be increased.

Due to the present inclination of the carrier, after the positioning of the first metal layer, the ceramic substrate and the second metal layer on the carrier, the slipping of the individual metal layers or the ceramic substrate occurs, so that one with respect to the alignment of Metal layers and ceramic substrate to each other defined arrangement is achieved. Preferably, the individual layers or the substrate slip following the inclination of the carrier so far until they hit a boundary.

The boundary on the support to which the metal layers and the ceramic substrate of the device are positioned due to the inclination of the carrier may be arbitrarily formed as long as it is capable of the arrangement of the metal layers and the interposed ceramic substrate Tilt the carrier or already inclined carrier to fix. In general, the boundary is designed so that it is provided in the sense of a projection or stop on the support side of the arrangement to be positioned on the edge of the carrier and protrudes beyond the carrier.

In the in 2a illustrated embodiment, wherein the carrier over the edge 5 is tilted, a limitation at the downside by the edge is sufficient to fix the arrangement of the two metal layers and the ceramic substrate.

The boundary can be formed from a projecting over the carrier in the direction of the arrangement projection or stop, which is either integrally formed and therefore continuous, or is interrupted and thus from a plurality of individualized, d. H. at least two individual projections or stops.

In the case of the embodiment of the 2 B the corresponding boundary can also be formed by a projecting projection or stop, which is located on the two adjacent inclined edges of the carrier and, for example, pointed to the point below 10 hinläuft. Optionally, it is also possible that the limitation in the embodiment according to 2 B is formed of two or more, for example, two, three, four, five or six, short and separate Vorsprügen or stops, wherein the projections or stops on the two downwardly inclined adjacent edges of the support are provided.

The shape, dimension and position of these boundaries can be made almost arbitrary. However, the boundaries are preferably as narrow as possible, so that they have a small contact surface to the bond and include ceramic materials, such as Al ₂ O ₃ .

In a second embodiment, the carrier has a curvature. Heating the ceramic substrate and metal layers in process step (2) results in an adaptation of the resulting arrangement to the curved shape of the support. The resulting arrangement therefore also has a curvature predetermined by the carrier after method step (2).

In the case of a substantially rectangular support, the curvature produced by the curvature may be possible both in one direction and in both directions of the plane spanned by the support.

The curvature of the carrier provided according to the invention can follow a circular, elliptical, parabolic, sinusoidal, tangent and / or logarithmic function.

In the case that the curvature of the carrier follows a circular or elliptical function, at least one radius of the function is generally 200 to 1000 mm, preferably 500 to 8000 mm, more preferably 1000 to 6000 mm, further preferably 1500 to 5000 mm, farther preferably 2000 to 4000 mm. In the case of a curvature of the carrier, which follows an ellipse function, the two radii of the ellipse are also in the above-mentioned areas.

The carrier with the aforementioned curvature may be formed both convex and concave.

The determination of the radius in a corresponding circular or ellipse function is in 9 shown.

In a general embodiment of the present invention, the carrier has a curvature corresponding to a deviation from an ideal, absolutely flat plate of 0.2% or more of the carrier length and / or 0.1% or more of the carrier width.

The dimension of the support can be chosen within a wide range and depends on the orders of magnitude of the double-sided metallized ceramic substrates to be produced and the bonding furnaces used. Suitable dimensions of the carrier are between 20 × 20 mm ² and 300 × 350 mm ² , wherein the shape of the carrier is preferably either substantially square or substantially rectangular.

In the bonding furnace, which is generally a tunnel kiln or continuous furnace, are basically one- or multi-storey and single or multi-row constructions of the carrier conceivable.

In the context of the present invention, embodiments are therefore also provided in which carriers are used which are designed for the simultaneous bonding of a plurality of arrangements. With such a combination of several mounting surfaces, the size described above increases according to the number of arrangements. These carriers then have a plurality of support plates arranged one above the other and / or next to one another, on each of which an arrangement to be bonded is positioned.

In the bonding furnace, the assembly which rests on the support is usually passed through the furnace at a constant transport speed and thus brought to a temperature at which joining of metal foil and ceramic substrate takes place, and subsequently after passing through the heating zones cooled down again.

In the bonding furnace, the lowest point of the carriers used according to the invention, which is formed by the inclination, can be in the transport direction both at the front and at the rear.

Engobe / release agent

During the double-sided bonding process, the metal layer disposed between the substrate and the ceramic substrate melts superficially. If contact with other surfaces, such as the support, occurs at this time, there is a possibility that defects in the generated metal coating on the ceramic substrate will occur.

In order to avoid such defects on the metal surface, which is associated with the carrier, it is known from the prior art to provide so-called release agents on the carrier.

Therefore, in a preferred embodiment of the present invention, an inclined and / or inclinable and / or domed support is used, which is provided on the surface side oriented to the metal layer of the double-sided metallized ceramic substrate with a release layer such that during bonding, a bond of the on this release layer adjacent metal layer does not enter the carrier. This makes it possible in particular to provide on the separating layer in each case an arrangement consisting of a lower, the separating layer immediately adjacent the first metal layer, a ceramic layer disposed above and from a further metal layer disposed above, and this overall arrangement then by bonding to the double-sided metallized ceramic substrate to connect.

The release layer optionally provided on the support may comprise a material which is selected from the group consisting of oxidic, nitridic or carbidic ceramics and salts.

In particular, the release layer comprises a material selected from the group consisting of mullite, steatite, cordierite, Al ₂ O ₃ , TiO ₃ , ZrO ₂ , MgO, CaO, yttria, SnO ₂ , CaCO ₃ , BN, ZrN, graphite , Zirconia-reinforced alumina (ZTA), BeO, Al ₂ TiO ₅ , CaSO ₄ , MgSO ₄ , BaSO ₄ and mixture of the aforementioned materials.

Furthermore, it is preferred that the separating layer comprises a material which is selected from the group consisting of mullite, steatite, cordierite, Al ₂ O ₃ , ZrO ₂ , MgO, Al ₂ TiO ₅ , SnO ₂ , yttrium oxide, BaSO ₄ , MgSO ₄ and mixture of the aforementioned materials.

The separating layer optionally used on the carrier has in particular a thickness of 10 to 1000 .mu.m, preferably 25 to 750 .mu.m, more preferably 50 to 500 .mu.m, more preferably 75 to 400 .mu.m, more preferably 100 to 350 .mu.m. Furthermore, it is preferred if the release layer has a porosity, i. H. a ratio of the pore volume to the volume of solids of greater than 10%, more preferably greater than 15%, more preferably greater than 20%. The particle size of the particles forming the separating layer is generally less than 50 μm, preferably less than 40 μm, more preferably less than 35 μm, more preferably less than 30 μm.

The separating layer provided according to the invention may, for example, also be provided with a colored additive. The use of such a colored additive has the advantage that it is easy to see visually whether the release layer has a defect and is thus to be replaced if necessary. The colored additive may, for example, be chromium oxide.

In a further embodiment of the present invention, the separating layer may be composed of at least two separate sub-separating layers, wherein the separate sub-separating layers are applied on the carrier in succession.

Furthermore, it is possible for the separate sub-separating layers to have a substantially identical or a different composition.

It is also possible that the lower release layer, which is in direct contact with the carrier, the colored additive, such as chromium oxide having.

The sub-separating layer has a layer thickness of generally 50 to 1000 μm, preferably 75 to 800 μm, more preferably 100 to 600 μm, more preferably 125 to 400 μm, further preferably 150 to 350 μm.

If, after the bonding process and after removal of the assembly from the support, particles of the release layer still adhere to the metal layer, they can then be removed by a suitable method, for example by a mechanical process (eg brushing) or by a chemical process (eg, etching a thin surface layer).

Further embodiments of the separation layer can the DE 10 2004 056 879 A are taken from the relevant disclosure by reference in the present invention.

arrangement

The inventive method is suitable for producing double-sided metallized ceramic substrates, which are also the subject of the present invention. The arrangements according to the invention can have, in addition to the two metal layers and the ceramic substrate, further layers, such as a solder layer.

The ceramic substrate may, for example, be substrates of aluminum oxide, aluminum nitride, silicon nitride or silicon carbide. For the ceramic layer, for example, an alumina ceramic (Al ₂ O ₃ ) with a content of zirconium oxide (ZrO ₂ ) in the order of about 2-30% or an aluminum nitride ceramic, for example with yttria as an additive, or a silicon nitride Ceramic, wherein the aluminum nitride ceramic and / or the silicon nitride ceramic, for example, may have an oxidic surface layer, for example, a surface layer of aluminum oxide. The thickness of the ceramic layer is preferably in the range between 0.2 and 1.5 mm.

The metal layers on the ceramic substrate may be formed starting from metal sheets or metal foils having a thickness of generally 100 to 1000 μm, preferably 125 to 750 μm, more preferably 150 to 700 μm, more preferably 175 to 600 μm before the bonding step.

Before the process according to the invention, the metal foils or sheets can be oxidized on both sides in a known manner.

The method according to the invention is suitable for the production of metal-ceramic substrates (MCS) and substrates which are produced by means of direct copper bonding (DCB), direct aluminum bonding (DAB) or active metal bonding (AMB).

The resulting arrangements differ from those of the prior art in an improved positional accuracy of the metal layers and the ceramic substrate to each other and / or in a defined curvature.

carrier

Another object of the present invention is a carrier for producing a double-sided metallized ceramic substrate, which is used in the method described above. With regard to the specific embodiments of the carrier according to the invention, reference is therefore made to the above statements.

In particular, the carrier according to the invention is used in a tunnel kiln or continuous furnace for the production of double-sided metallized ceramic substrates, wherein the tunnel kiln or continuous furnace is provided for a heat treatment of treated with at least one tunnel-like furnace space and at least one heating device for heating the at least one furnace chamber and a transport unit which transports the carrier according to the invention through the oven space.

The carrier may comprise at least two parts, wherein the carrier comprises a support surface for receiving the metal layers and the ceramic substrate and a tool carrier. The support surface is connected to a transport unit via the tool train carrier, which makes it possible to transport the carrier through the tunnel kiln.

The bearing surface of the carrier should consist of a material which is reaction-inert or at least relatively inert in relation to the bonding process and which preferably is not wettable. The support surface of the carrier may for example consist of a heat-resistant or high temperature resistant material, preferably a ceramic material, in particular graphite, mullite, steatite, cordierite, ZrO ₂ , Al ₂ O ₃ , AlN, BN, ZrN, Si ₃ N ₄ , SiC and mixtures thereof , consist. Furthermore, high-temperature-resistant metals are suitable for the bearing surface, in particular alloyed steel, preferably Inconel, or an alloy comprising a constituent selected from the group consisting of molybdenum, titanium, chromium, nickel, tungsten or mixtures thereof.

It is further preferred if the support surface can optionally be reused after cleaning.

In the case of using SiC for the support surface of the present invention, which is particularly preferred in the present invention, recrystallized SiC, nitride-bonded SiC, isostatically pressed SiC, Si-infiltrated SiC, non-pressure sintered SiC or liquid-phase sintered SiC are suitable.

Embodiments of inventive beams of the present invention are also contemplated that are configured for multiple substrates, for example, two, three, four, five, or six arrays. An exemplary embodiment of such a carrier is in the 7 represented, with different arrangement possibilities of individual carriers in the oven in the 8th are shown.

The present invention will now be explained in more detail with reference to the following description of the figures.

The reference numerals used in the description of the figures have the following meaning:

LIST OF REFERENCE NUMBERS

1

Ceramic substrate,

2, 3

Carrier of the prior art,

4

Carrier (according to the invention),

5, 8, 9

Axes of rotation

6, 7, 10, 11

Corner points of a substantially rectangular support 4 .

12 ', 12' ', 12' '', 12 '' ''

by inclination formed height difference to zero level,

13

Supporting surface,

14 ', 14' ', 14' '', 14 '' ''

Limits and

15 ', 15' '

height adjustable feet.

Show them the
1 two conventional prior art designed as bond boats carrier, with which two-sided metallized substrates are prepared in a two-stage process. The already one-sided bonded substrates 1 become so on carriers 2 . 3 fixes that there is no direct contact of the already bonded copper or ceramic surface with other surfaces, such as the conveyor belt, in the second bonding step. This is done for example by the use of carriers in which the one-side bonded substrates 1 only at the edges 2 resting on a support (cf. 1a ) or over narrow runs 3 on the short sides of the substrates 1 be carried (cf. 1b ).

Furthermore, the shows
2 a substantially rectangular inclined support 4 , the Indian 2a over an edge 5 is inclined so the vertices 6 and 7 of the wearer are in a plane below the zero level of the wearer. In the 2 B the carrier is a total of two edges 8th and 9 , inclined so the vertices 10 and 11 of the wearer are below the zero level of the wearer. The arrows shown 12 ' . 12 '' . 12 ''' and 12 '''' indicate the inclination of the wearer.

In the context of the present invention, a zero plane is understood to mean that plane which is stretched by the carrier in a non-inclined and / or arched form.

The
3 shows a sloped carrier 4 in which the inclination of the carrier is given by the illustrated angles α, β and γ. By selecting suitable angles α and β results in an angle γ, which is a measure of the deviation of the inclined carrier from the zero plane, the angle γ in the present invention, 0.5 to 40 °, preferably 0.5 to 35 °, more preferably 0.5 to 30 °, more preferably 1 to 25 °, more preferably 1 and 5 °.

The
4 shows an embodiment of a carrier 4 which is used in the context of the method according to the invention. The carrier 4 has a support surface 13 on which the assembly comprising at least two metal layers and a ceramic substrate interposed therebetween is positioned. The carrier 4 and the wing 13 have an inclination, whereby it after laying the arrangement to a slipping or reliable positioning of the arrangement in the direction of the edges provided on the support boundaries 14 comes.

The carrier 1 is to the point 4 inclined, wherein the carrier is inclined about the axes parallel to the edges a and b. The inclinations respectively achieved correspond to the angles α and β, resulting in an angle γ forming on the horizontal. The angle γ in the context of the present invention is preferably 0.5 to 45 °.

Furthermore, the shows
5 an embodiment of a carrier 4 which is inclined, taking the inclination of the wearer 4 through at the corners of the substantially rectangular support 1 located height-adjustable feet 15 ' . 15 '' and 15 ''' is reached.

The
6 shows a sloping and arched support 4 , the three limits 14 ' . 14 '' . 14 ''' having, at the long edge lying down through the inclination 2 limitations 14 ' and 14 ''' and at the short edge defined by the inclination a limit 14 ''' is provided.

The
7 shows an embodiment of a carrier according to the invention 4 with two mounting surfaces 15 and 16 while the

8th represents a variety of possible arrangements of the support in the tunnel furnace.

The
9 shows in a curved support according to the present invention, the dependence of the deflection of the radius of curvature at a curvature of the carrier, which follows a circular or elliptical shape. The radius of curvature R results from the deflection d of the carrier at a length or width a of the carrier as follows:

This results in exemplary substrate widths or substrate lengths of 140 mm or 190 mm following exemplary ratios of radius of curvature R to deflection d: Deflection d Substrate length / width of the substrate 190 mm 140 mm Radius of curvature (mm) 9000 0.5 0.3 6000 0.8 0.3 2000 2.3 1.2 1000 4.5 2.5 500 9.1 4.9 200 24.0 12.7

In the context of the present invention, in the case of a curvature of the carrier in the form of a circular or elliptical shape with a substrate length or substrate width of 190 mm (140 mm), the deflection d is at least 0.5 mm (0.3 mm).

The inventive method makes it possible to connect at least one ceramic substrate on the top and bottom in only one process run, each with a metal layer. In this case, a high positional accuracy of the layers is achieved and achieved a reproducible defined curvature of the resulting arrangement.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• US 3744120 [0003]
• US 3994430 [0003]
• EP 0085914 A [0003]
• DE 2319854 A [0003]
• DE 102010023637 A [0014, 0014]
• DE 102004056879 A [0015, 0016, 0018, 0087]

Claims (12)

A method of manufacturing a double-sided metallized ceramic substrate, characterized by the following method steps: (1) positioning an assembly comprising at least a first metal layer, at least a second metal layer, and a ceramic substrate disposed between the first and second metal layers on one Carrier; (2) heating the assembly resulting from the process step (1) to a temperature such that bonding of the ceramic substrate and the two adjacent metal layers by bonding to form a double-sided metallized ceramic substrate, characterized in that the Carrier in step (1) before positioning the arrangement is inclined and / or curved and / or the support in step (1) after positioning the arrangement on the support and / or during the process step (2) is inclined. A method according to claim 1, characterized in that the carrier is formed substantially rectangular and an edge 5 is tilted, giving a total of two corners of the rectangular support 6 and 7 result, which are located after the inclination on a substantially identical lower level. A method according to claim 1, characterized in that the carrier is formed substantially rectangular and two edges 8th and 9 is tilted, leaving a total of only one corner of the rectangular beam 10 is at the lowest level. Method according to one of claims 1 to 3, characterized in that the inclination of the carrier provided in the method steps (1) and / or (2) is designed so that it comes to an alignment of the arrangement and / or the individual components of the Arrangement comprising at least the two metal layers and the ceramic substrate, to arrange each other. Method according to one of claims 1 to 4, characterized in that the carrier edge has at least one boundary in the form of at least two stops or at least two edges. Method according to one of claims 1 to 5, characterized in that the carrier has a curvature and the curvature of the carrier of a circular, elliptical, parabolic, sinusoidal, tangent and / or logarithmic function follows. Method according to one of claims 1 to 6, characterized in that on the carrier a separating layer is provided, wherein at least one of the metal layers of the arrangement bears against the separating layer. An assembly comprising at least a first metal layer, at least one second metal layer and a ceramic substrate disposed between the first and second metal layers, obtainable by the method according to one of claims 1 to 7. Carrier for producing a double-sided metallized ceramic substrate, characterized in that the carrier is inclined, tiltable and / or curved. Carrier according to claim 9, characterized in that the carrier is used in a tunnel kiln or continuous furnace for the production of double-sided metallized ceramic substrates, wherein the tunnel kiln or continuous furnace for a heat treatment of treated with a at least one tunnel-like furnace space and at least one heating device for heating the at least one furnace chamber is provided and has a transport unit which transports the carrier through the furnace chamber. Carrier according to claim 9 or 10, characterized in that the carrier edge has at least one boundary in the form of at least two stops or at least two edges. Carrier according to one of claims 9 to 11, characterized in that the carrier has a curvature and the curvature of the carrier of a circular, elliptical, parabolic, sinusoidal, tangent and / or logarithmic function follows

Images