WO2016020207A1

WO2016020207A1 - Method for producing double-sided metallised ceramic substrates

Info

Publication number: WO2016020207A1
Application number: PCT/EP2015/066959
Authority: WO
Inventors: Alexander Rogg; Gabriel ZIER
Original assignee: Heraeus Deutschland GmbH & Co. KG
Priority date: 2014-08-05
Filing date: 2015-07-24
Publication date: 2016-02-11
Also published as: DE102014215377A1; TWI597257B; EP3177580A1; DE102014215377B4; TW201612137A

Abstract

The invention relate to a method for producing a double-sided metallised ceramic substrate, in which the ceramic substrate and the metal layers are inclined and/or curved during the production thereof.

Description

METHOD FOR PRODUCING DOUBLE-SIDED METALLIZED CERAMIC SUBSTRATES Description

The present invention relates to a method for producing a double-sided metallized ceramic substrate, the double-sided metallized ceramic substrates and substrates obtainable by the method, which are 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 Lelstungshalblelrer- module. In this case, a ceramic substrate is provided on the upper and lower surface with a metallization, wherein usually at least one metallized side later has a shading-generated structure, for example, by etching processes. The known method for producing these double-sided metallized ceramic substrates is by eutectic bonding and is generally referred to as a direct bonding process.

Basic descriptions of processes for producing metallized ceramic substrates by bonding processes can be found in US Pat. Nos. 3,744,120, 3,994,430, EP 0 085 914 A or DE 23 19 854 A, the disclosure of which is incorporated herein by reference is included. In the context of the direct copper bonding process (DCB process), it is common to these known production methods that a copper foil is firstly oxidized in such a way that a substantially uniform copper oxide gap results. The resulting copper foil is then placed on a ceramic substrate and the ceramic substrate / copper foil composite is heated to a process or bonding temperature of between about 1025 and 1083 ° C, which results in the formation of a metallized ceramic substrate. Substrate is coming. Finally, the resulting metallized ceramic substrate is cooled.

The bonding of ceramic substrate and metal foil is generally carried out in so-called bonding ovens. Corresponding bonding furnaces, often also referred to as tunnel furnaces, include, inter alia, an elongated tunnel-like furnace. raum (also called muffle) and a transport device with a transport element, for example in the form of a flexible and hflzebeständlgen conveyor belt for transporting the material to be treated by the heated with a heater furnace 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 roll is cooled down 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 producing double-sided metallized ceramic substrates, the ceramic is bonded in two furnace passes to the metal layers on the opposite selvages of the ceramic substrate. For the intended purpose, a ceramic substrate is first positioned on a support and then placed on the overhead, i. The side facing away from the carrier covered with a metal foil. By the action of heat, the side of the ceramic substrate is connected to the metal layer and then the resulting arrangement is cooled. Subsequently, the substrate is turned over and in a second Bondschrttt the other side of the substrate is provided on the same catfish with a metal layer. Therefore, all metallized ceramic substrates produced in a two-step bonding process pass through the tunnel furnace twice.

In the case of the coating of the second substrate chain, the metal plate already formed on the ceramic substrate in the first bond layer is generally applied to the carrier, whereby due to the required bond heat for the second metallization, the first metal layer already formed is also melted can. In this case, misalignments may result in the initially formed metal layer on the ceramic substrate, since there are generally interactions between the partially melted first metal layer and the carrier on which the first formed metal layer is located with the substrate. comes. Corresponding misalignments can result, for example, from residues of the support material or other foreign bodies which adhere to the molten metal layer after removal from the support. In order to report the disadvantage of the known methods for producing double-sided metallized substrates, the use of carriers has been proposed in which the substrates which have already been bonded on one side are fixed on carriers in such a way that there is no direct contact of the already bonded ceramic surface other surfaces, such as the carrier or conveyor belt, in the second Bondschrrrt comes. This occurs for example by dle use of carriers, in which one side bonded substrates dle only at the edges on a support up or lie over narrow restrictions on the short Rarely of the substrates ¹ carried the advertising. Corresponding carriers - also called bond boats - are shown in FIGS. 1a and 1b.

However, the double-sided metallized substrates produced by means of the so-called bond boats also have disadvantages. For example, when using bond boats according to FIG. 1a with oblique supports 2, there is the problem that already tored substrates 1 slip into a position of the lowest center of gravity and thus the torsion already resulting from the ceramic substrate or the first process step becomes even wetter strengthened. In the embodiment of bond carriers illustrated in FIG. 1 b, in which the substrate 1 rests on edges 3, it is again disadvantageous that the substrates on the underside are in contact with, for example, the transport chain on which they are pulled through the oven will come, which will also lead to a loss of quality.

Furthermore, on the ceramic side, the first step of the process can not be used. Deposit kiln dust, which then leads to malpositions in the second metallization.

Furthermore, the conventional two-stage bonding process for producing double-sidedly metallized substrates has 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 positioning accuracy of metal layer and substrate, in particular in the second Bondschrfft.

To overcome the disadvantages of the two-stage process for producing double-sided metallic In order to circumvent the substrates, methods for simultaneous double-sided bonding of metal layers to substrates have been developed. These methods perform simultaneous bonding of the metal layers in only one process step on both rare of the ceramic substrate. For example, DE 10 2010 023 637 A describes a method for producing double-sidedly metallized substrates in a single method step, wherein a first metal layer, a substrate and a second metal layer are sequentially positioned on a support in the given order, wherein the support on the upper panel, facing the assembly of the first and second metal plates and the substrate, having a plurality of protruding lobes tapering in the direction of the first and second metal plate and substrate arrangement. According to 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 double-sided bonding process. This is intended to prevent damage to the metal layer, which rests on the carrier during the bonding process. Nevertheless, there are still adverse interactions at the points of contact between the projecting lugs and the metal sheet to be bonded, and particularly when using supports based on nitride ceramics, eg AIN, a surface oxydatlon and thus possibly a bond with the latter occurs bonding metal foil.

DE 10 2004 056 879 A relates to a method for producing double-sidedly metallized ceramic substrates using the direct bonding process, in which an arrangement of at least two metal layers and a ceramic substrate arranged between the metal layers on a is positioned with a release layer provided carrier and then the arrangement is heated to a temperature at which there is a bonding of the two metal layers with the ceramic substrate. By dle use of a corresponding separation layer should not come to a connection of the carrier with the adjacent Metallschlcht the arrangement.

DE 10 2004 056 879 A focuses 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 of less than 0.1% of the carrier plates. By dlese Particularly high demands on the carrier should be made for the production of particularly flat double-sided metallized ceramic substrates. Nevertheless, 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 is, for example, due to raw material influences that are noticeable. The deflection of the resolling double-sided metallized ceramic substrates therefore fluctuates considerably even when the method described in DE 10 2004 056 879 A is used both in the longitudinal / transverse direction and in the height, and is furthermore unoriented.

In addition, the resulting double-sided metallized ceramic substrates made with asymmetric metal thicknesses (eg, bezel metal 0.3 mm and metal back 0.2 mm) have different metal volumes on the two series of substrate after bonding an undefined bending in the longitudinal and transverse direction, whereby the thicker metal layer is usually formed on the concave side.

In addition to the problem of resistance to aftertaste, the positional accuracy of both metal layers in relation 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 any step of aligning the two metal layers and the substrate, respectively. 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 subsequent process steps, then have to be removed again, for example by etching, and moreover lead to an unnecessary material rejection.

Variations in the resulting problems of the prior art The specifications of the resulting double-sided metallized ceramic substrates, 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 the prior art, the present invention thus first of all sets itself the general task of remedying the previously discussed disadvantages of the state of the art.

In particular, it is the object of the present invention to provide a method for producing double-sidedly metallized ceramic substrates, wherein the bonding process can preferably take place in one stage and thus simultaneously on both rare materials of the ceramic substrate.

More importantly, 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 sheet to ceramic is improved. It is another object of the present invention to provide a method of making double-sided metallized ceramic substrates in which the resulting double-sided metallized ceramic substrates have a defined, i. Essentially constant deflection, which plays a role in particular in subsequent system soldering or chip soldering or in use in a bottomless module.

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

Positioning an assembly comprising at least a first metal sheet, at least one second metal sheet, and a ceramic substrate disposed between the first and second metal sheets on a support;

(2) heating the assembly resulting from process step (1) to a temperature such that it forms a composite of the ceramic substrate and the two adjacent metal layers by bonding to form a double-sided metal layer. talllslerten ceramic substrate comes.

The method according to the invention is then characterized in that the carrier is tilted and / or curved in the process section (1) before the positioning of the arrangement and / or the carrier is in process step (1) after the positioning of the arrangement on the carrier and / or during the process Verfahrensschrttt (2) is inclined. It may also be a pivoting movement up to a zero slope or a tendency to a negative angle is 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 the preferably planar or plate-shaped elements consisting of a ceramic material, which are or are provided with metallization on two of their surface sorts The ceramic substrates used do not involve angular ceramic bodies, as are used in particular in DE 10 2008 001 224. The planar or plate-shaped ceramic substrates which only have a maximum of 1% on an edge length of the ceramic substrates, based on an ideal pkanare level (For example, with a substrate length of 200 mm, the deviation would be a maximum of 2 mm.) Thus, the ceramic substrates have at best a slight curvature (and in no case an angular curvature).

In a preferred embodiment, therefore, the ceramic substrate is additionally characterized in that the flatness of the ceramic substrate is less than 1%, based on the edge length of the ceramic substrate. With regard to the carrier is inventively provided that dleser also has only a slight curvature. In particular, it is preferred if the carrier has a bulge of not more than 5%, preferably not more than 3%, preferably not more than 1%, in each case based on the edge length of the carrier and based on an ideal planar plane. In a preferred embodiment, the carrier is therefore additionally identified by net, that the flatness of the carrier is less than 5%, preferably less than 3%. preferably less than 1%, in each case based on the length of the carrier.

In the context of the present invention, a flatness of the ceramic substrate or carrier is understood to mean a shape tolerance of the ceramic substrate or of the carrier in which the flat surface of the ceramic substrate or carrier must be located. The tolerance limits result from two imaginary surfaces, parallel to the ideal planar surface of the ceramic substrate or support, in which case, in which case the real surface of the ceramic substrate or support is produced by the one of the parallel surfaces pierces the tolerance is exceeded. In the context of the present invention, an arrangement is understood to mean a composite of two metal layers between which a ceramic substrate is provided, wherein the arrangement may be before, during or after the bonding.

The term "substantially" in the sense 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 Anwendungsmögllketten 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, in themselves or in any combination, are fundamentally the subject matter of the invention, regardless of their summary in the claims or their backwardness. Also, the content of the claims is made part of the description,

In a first embodiment, the method according to the invention provides that the arrangement comprising the at least two metal plates and the ceramic substrate arranged therebetween is inclined before or during actual bonding in process step (2). This inclination of the arrangement can be achieved by positioning the support on which the arrangement of the two metal layers and the ceramic substrate arranged therebetween is either mechanically inclined after the positioning of the arrangement or to the point in time at which the arrangement is already tilted from the two metal plates and the interposed ceramic substrate is positioned on the carrier. Should it be provided that the carrier is tilted after positioning the arrangement, so can Tending the carrier both in process step (1), ie before heating the arrangement, or In Verfahrensschrttt (2), ie during the heating of the arrangement occur.

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 through the inclination of the carrier in a predetermined position, so that their arrangement to each other as defined is seen. Therefore, with the method according to the invention, double-sidedly 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 one another.

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

The inventive method provides in a further second embodiment that the carrier has a curvature. The arrangement positioned on the carrier, comprising the at least two metal layers and the ceramic substrate arranged therebetween, will approach the curvature of the carrier in the subsequent bonding process in method step (2) under the effect of corresponding bonding temperatures Overall, curved double-sided metallized ceramic substrates are formed, but in their entirety they have a defined and constant curvature. It is thus possible by the method according to the invention to produce reproducibly double-sidedly metallized ceramic substrates in series, the deflection of which is determined both in the z direction (height) and in the x and y direction (longitudinal and transverse direction). is clearly defined. This reproducible deflection in height as well as longitudinal and transverse direction is particularly noticeable in asymmetric material combinations, i. in the case of double-sided metallized ceramic substrates, in which the thickness of the two metal plates is different on the two rants of the ceramic substrate (for example 0.3 mm Cu / 0.38 mm ceramic / 0.25 mm Cu).

By combining the first embodiment (inclination) and the second embodiment (curvature), it is possible to produce, especially in series, double-sided metallized ceramic substrates which have constant characteristics, in particular with regard to orientation of the individual layers and curvature. Therefore, the present invention relates in particular to a method according to the invention, which in series production has a multiplicity of double-sidedly metallized ceramic substrates with substantially 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 method according to the invention for producing double-sided metallized ceramic substrates uses a support 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 selection of the materials of the bonding boat are to be selected such that, if the wearer approaches the horizontal position as required, the individual components of the assembly do not slip.

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

The support used in the process according to the invention is preferably made a material with a high hardness, which is inert and / or not wettable at the temperatures of the bonding process used. As Malerlallen for the support according to the invention are in particular materials selected from the group consisting of graphite, Mulllt, Slecrttt, Cordlerit, Zr0 ₂ , Al ₂ 0 ₃ , AIN, BN, ZrN, SijN * SIC and mixtures thereof, in question.

The support used in the method 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, preferably 1 to 5 to 5 mm.

In a first embodiment, the carrier has a slope or is formed so that it can be inclined. Due to the tendency to tilt, after the positioning of the adjacent metal layer, the subsequent ceramic substrate layer and the closing metal layer, the individual layers are positioned relative to one another. In order for the arrangement to remain fixed on the carrier, it is provided that, for example, a substantially rectangular carrier is provided with at least one stop on at least one of the respective edges lying below by the inclination with a boundary. If the arrangement comprising the at least two metal layers and the ceramic substrate arranged therebetween is now 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 so that they also have a clearly defined positioning relative to one another.

In comparison, a positioning in the method of the prior art 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 exact positioning of the two metal sheets and the ceramic layer must be realized in the prior art methods or the resulting double-sided metallized ceramic substrates have a lack of clarity in the positioning of the two - 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 excluded after their production.

Assuming a substantially rectangular carrier, several possibilities exist for a tendency of the carrier to be realized within the meaning of the present invention. ren.

2 shows a possible rectangular geometry of the carrier, with rotations about the edge 5 (see FIG. 2a) or about the edges 8 and 9 (see FIG. In the embodiment shown initially in FIG. 2a, the essentially rectangular plane of the carrier is tilted only over one edge 5, so that a total of two corners of the rectangular carrier 6 and 7 result, which after the inclination lie on a substantially identical lower level are located.

In the embodiment illustrated in FIG. 2b, the substantially rectangular plane of the carrier is tilted about two edges 8 and 9, so that in total only one corner of the rectangular carrier 10 is at the lowest level.

In the context of the present invention, the embodiment shown in FIG. 2b is preferred since, because of the two-sided positioning, it permits a more precise positioning of the individual components of the arrangement relative to one another. According to the invention preferably dle the term .Niveau "lateral plane were comparable. In what is dle substantially rectangular plane of the medium can at least partially located. It is the .Ausgangsniveau ^* to which all other arrival gave are relatively related, the Level in which the substantially rectangular plane of the carrier first extends (process step (1) positioning of the carrier) All other terms of the "level" are to be understood relative to their starting level. In particular, a lower level ^{1 * is} understood to mean a lateral plane which is displaced in a vertical direction parallel to the plane of the initial level. Preferably, the lower level is thus lowered vertically relative to the starting level. Furthermore, it is understood, in particular under a .tiefsten level ^* dle lateral plane which is displaced parallel to the plane of the output levels in the vertical direction and thereby comprises dle highest relative displacement in which is still at 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 starting level than the lower level (according to the invention, the cases in which there is only a relative vertical shift is referred to as a case of a lower level; is the deeper oil level at the lowest level). The carrier inclined from them about the axes of rotation 8 and 9 then has an inclination which is described by the angles α, β and γ shown in FIG.

Depending on the choice of the angles a and ß results in an angle γ, which is generally 0.5 to 45 °, preferably 0.5 to 40 °, welter preferably 0.5 to 35 °, more preferably 1 to 30 ° welter 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 overall height of the carrier used is too large and again the height of the used tunnel kiln 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, alignment takes place with slippage of the individual metal layers or of the ceramic substrate on the alignment of Metallschlchten and ceramic substrate to each other defined arrangement is achieved. Preferably, the individual layers or the substrate slip following the inclination of the carrier until they hit a boundary.

The boundary on the support to which the metal braids and the ceramic substrate of the assembly are positioned due to the inclination of the carrier may be made bulky as long as it is capable of arranging the assembly of the metal sheets and the interposed therebetween Ceramic substrate in case of inclination of the carrier or already inclined carrier to fix. In general, the delimitation is designed in such a way that, in the sense of a projection or abutment on the supporting element of the arrangement to be positioned, it is provided peripherally on the carrier and protrudes beyond the carrier.

In the embodiment illustrated in Figure 2a, in which the carrier is tilted over the edge 5, a boundary at the downwardly sloping edge is sufficient to fix the assembly of the two metal plates and the ceramic substrate. In this case, the boundary can be formed from a projection or stop protruding beyond the carrier in the direction of the arrangement, either in one piece and thus is consistently formed, or aiser is interrupted and thus from several individualized, ie at least two individual projections or attacks looks.

In the case of the embodiment of Figure 2b, the corresponding boundary can also be formed by a protruding projection or stop which is located on the two adjacent inclined edges of the carrier and, for example, points pointedly to the point 10 below. It is also possible that the limitation in the embodiment according to FIG. 2 b is formed from two or more, for example two, three, four, five or six, short and separate checks or stops, wherein the projections or stops on the both downwardly inclined, adjacent edges of the carrier are provided.

The shape, dimension and position of these limitations can be designed almost arbitrarily. However, the boundaries are preferably made as narrow as possible, so that they have a small contact surface to the bond and include ceramic materials, such as Al ₂ 0 ₃ . In a second embodiment, the carrier has a curvature. By heating the ceramic substrate and metal layers in process step (2), the resulting arrangement is adapted 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 preferably 2000 to 4000 mm. In the case of a curvature of the carrier following an elliptical function, the two wheels of the ellipse are also in the above-mentioned ranges. The carrier with the aforementioned curvature may be formed both convex and concave.

The determination of the radius in a corresponding circular or elliptical function is shown in FIG. 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 bar.

The dimension of the support can be granted in a wide range and depends on the orders of magnitude of the double-sidedly metallised 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, basically single or multi-level structures as well as single or multi-row structures of the beams are conceivable. In the context of the present invention, therefore, embodiments are also provided in which carriers are used which are designed for the simultaneous bonding of several arrangements. With such a combination of a plurality of mounting areas, 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 arrangement which rests on the support is generally passed through the furnace at a constant transport speed and thus brought to a temperature at which bonding of metal foil and ceramic substrate takes place, and subsequently cooled again by passing through the heating zones of the furnace.

In the bonding furnace, the lowest point of the carrier used in accordance with the invention can be in the transport direction both at the front and at the rear.

The process according to the invention is preferably not for simultaneous production of several, for example two or three, double-sided metallized ceramic substrates used as by means of a stacking arrangement according to DE 10 2008 001 224 A,

Engobe / Cleavers During the double-sided bonding process, the metal layer located between the substrate and the ceramic substrate melts opecifically. If, at that time, it comes into contact with other surfaces, such as the support, 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 assigned to the carrier, it is known from the prior art, so-called release agents on the

Provide support,

Therefore, in a preferred embodiment of the present invention, a tilted and / or tiltable and / or curved support is used, which is provided on the surface side oriented towards the metal layer of the double-sided metallized ceramic substrate with a release layer such that during bonding a connection of the metal layer adjoining the separating layer with the carrier does not occur. In this way, it is possible, in particular, to provide on the separating layer in each case an arrangement consisting of an underlying first metal layer immediately adjacent to the separating layer, of a ceramic layer arranged above it and of a further metal layer arranged above it, and then through the entire arrangement Bonding to connect the double-sided metallized ceramic substrate.

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

In particular, the separating layer comprises a material which is selected from

Group consisting of silicate, especially alkali metal and alkaline earth metal silicates, Mulllt, Steatrt, Cordlerii Al ₂ O ₃ , TiO ₂ , ZrO ₂ , MgO, CaO, yttria, SnO ₂ , CaCO ₃ , BN, ZrN, graphite, zirconia-reinforced alumina (ZTA), BeO, aluminum trfanar (Al ₂ TiO ₅ ), CaSO ₄ , MgSO ₄ , BaSO ₄ and mixture of the aforementioned materials, Furthermore, it is preferred that the separation layer comprises a material which is selected from the group consisting of Mulllt, Steaflt, Cordlertt, Al ₂ O ₃ , ZrO ₂ , MgO, Al ₂ HO _e , SnO ₂ , Yttrlumoxld, BaSO ₄ , MgSO ₄ and mixture of the aforementioned materials.

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

The release layer, which may optionally be 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 visually easy to see whether the separation flaw has a defect and is therefore to be replaced if necessary. The colored additive may, for example, be chromium oxide.

In a welteren embodiment of the present invention, the separation layer may be composed of at least two separate sub-separating layers, wherein the separate sub-separating layers are applied to the carrier in succession. Of the welter It is possible that the separate subdividing layers have essentially the same or a different composition.

It is also possible that the lower separating layer, which is in direct contact with the carrier, has the colored additive, for example chromium oxide.

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, particles of the release layer still adhere to the metal layer, then they can be removed by a suitable method, preferably with an alloy mechanical processes (eg brushing) or with a chemical process (eg, etching a thin surface layer).

Further embodiments of the separating layer can be found in DE 10 2004 056 879 A, the disclosure of which is incorporated by reference in the present invention.

arrangement

The inventive method is suitable for the manufacture of 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 dle ceramic layer, for example, an aluminum oxide ceramic (Al ₂ O ₃₎ with a proportion of zirconium is suitable oxide (ZrO ₂₎ in the order of about 2-30%, or an aluminum nitride ceramics _", for example, yttrium oxide as an additive, or a silicon nitride ceramic, wherein the aluminum nitride ceramic and / or the silicon nitride ceramic, for example, an oxidic surface layer, for example, a surface layer of Alumlnlumoxld may have. 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 can be formed starting from metal sheets or metal foils, before the bonding step has a thickness of generally 100 to 1000 .mu.m, preferably 125 to 750 .mu.m, more preferably 150 to 700 .mu.m, more preferably 1 75 to 600 μm.

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

The process 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 (DGB), 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 support according to the invention is used in a tunnel kiln or continuous furnace for the production of double-sided metallized ceramic substrates, the tunnel kiln or continuous furnace for a heat treatment of treated material with at least one tunnel-like furnace space and with at least one heating device for heating the at least one furnace chamber is provided and has a transport unit which transports the carrier according to the invention through the furnace chamber.

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 the conveyor via a conveyor unit, which allows the conveyor to be transported 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 has a non-wettable material. The bearing surface of the carrier can be made, for example, of a heat-resistant or high-temperature-resistant material, preferably a ceramic material. In particular, graphite, mullite, steatite, Cordlertt, ZrO ₂ , Al ₂ O _3> AIN, BN, ZrN, Si ₃ N ₄ , SIC and mixtures thereof. 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 preferred for weathering if the support surface is can be used again.

In the case of using SIC for the support surface of the support according to the invention, which is particularly preferred in the context of the present invention, recrystallized SIC, bonded SIC, isostatically pressed SiC, SI-infiltrated SIC, non-pressure sintered SiC or liquid phase sintered SIC come into question.

Embodiments of carriers according to the invention are also encompassed by the present invention, which are designed for a plurality of substrates, for example for two, three, four, five or six arrangements. An exemplary embodiment of such a carrier is shown in FIG. 7, wherein different arrangement possibilities of individual carriers are shown in the oven in FIG.

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; 1 ceramic substrate,

2, 3 carriers of the prior art,

4 supports (according to the invention),

5, 8, 9 rotary axes,

6, 7, 10, 1 1 corner points of a substantially rectangular support 4, 12 '12 ", 12" ^ 12 "" formed by inclination height difference to Zero level, 13 bearing surface,

14 ', 14 ", 14'.14" "limits and

15 ', 15 "height adjustable feet. Show dle

Figure 1 shows two conventional trained as a bond boats carrier of the prior

Technique with which two-sided metallized substrates are produced in a two-stage process. The substrates 1, which have already been bonded on one side, are fixed on carriers 2, 3 in such a way that there is no direct contact of the already bonded copper or ceramic surface with other surfaces, for example the conveyor belt, in the second bond line , This takes place, for example, by the use of carriers in which the unilaterally bonded substrates 1 rest on a carrier only at the edges 2 (cf., FIG. 1a) or are carried over narrow supports 3 on the short sides of the substrates 1 (FIG. see Figure 1 b).

Femer shows dle

2 shows a substantially rectangular inclined support 4, the In the figure

2a is inclined over an edge 5 is. so that the corner points 6 and 7 of the carrier are located in a plane located below the zero plane of the carrier. In FIG. 2b, the carrier is inclined overall by two edges 8 and 9, so that the corner points 10 and 11 of the carrier are located below the zero plane of the carrier. The illustrated arrows 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 an unequal and / or curved form.

FIG. 3 shows an inclined support 4 in which the inclination of the support is given by the illustrated angles α, β and γ. By selecting suitable angles α and β, an angle γ results, which represents a measure of the deviation of the inclined carrier from the zero plane. The angle γ in the context of the present invention may be 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

FIG. 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 bearing surface 13 on which the arrangement comprising at least two metal layers and a ceramic substrate arranged therebetween is positioned. The support 4 and the supporting surface 13 have an inclination, whereby, after the arrangement has been laid, the arrangement 14 slips or reliably positions itself in the direction of the limitations 14 provided on the support at the periphery.

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

Femer shows dle

Figure 5 shows an embodiment of a carrier 4 which is inclined, wherein the inclination of the carrier 4 is achieved by height-adjustable feet 15 \ 15 "and 15 ^m located at the corners of the substantially rectangular support 1.

The

Figure 6 shows an inclined and curved support 4, the three boundaries

14 ', 14 ", 14'", wherein on the long by the inclination underlying edge 2 boundaries 14 'and 14 "' and at the bottom lying by the indent Nel tion limiting 14 is provided.

The

FIG. 7 shows an embodiment of a carrier 4 according to the invention with two Mounting areas 15 and 16, while dle

FIG. 8 shows a multiplicity of possible arrangements of the carrier in the tunnel.

In the context of the present invention, this shows the dependence of the deflection on the radius of curvature on 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 board 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:

In the context of the present invention is therefore in the case of a curvature of the carrier in the form of a circular or elliptical shape at a substrate length 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.

Claims

Claims: 1. Method for producing 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 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, characterized in that the Carrier in process step (1) is inclined and / or curved before the positioning of the arrangement Is and / or the carrier is tilted in process step (1) after positioning of the arrangement on the carrier and / or during the process Schrttt (2) ,

2. The method according to claim 1, characterized in that the carrier is formed substantially rectangular and is inclined over an edge 5, so that a total of two corners of the rectangular support 6 and 7 result, dle after tilting on an im Substantially identical lower-level.

3. The method according to claim 1, characterized in that the carrier is substantially rectangular in shape and is inclined over two edges 8 and 9, so that in total only one corner of the rectangular carrier 10 is at the lowest level.

4 .. The method according to any one of claims 1 to 3, characterized in that in the process carriage (1) and / or (2) provided inclination of the carrier is designed so that it comes to an alignment of the arrangement and / or dle individual components of the arrangement, comprising at least the two metal layers and the ceramic substrate, to each other.

5 .. The method according to any one of claims 1 to 4, characterized in that the carrier randseltlg at least one boundary in the form of at least two attacks or at least two Karrten.

6. The method according to any 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 Logartthmusfunktlon follows.

7. The method according to any one of claims 1 to 6, characterized in that on the carrier a separating layer is provided, wherein at least one of the metal tallschichten the arrangement bears against the separating layer.

8. Arrangement, comprising at least a first metal layer, at least a second metal layer and a ceramic substrate arranged between the first and second metal layer, obtainable by the method according to one of the claims Ί to 7.

9. carrier for producing a double-sided metallized ceramic substrate, characterized in that the carrier is inclined, tiltable and / or curved.

10. A carrier according to claim 9, characterized in that the carrier is used in a tunnel kiln or continuous furnace for producing double-sided metallized ceramic substrates, wherein the tunnel kiln or continuous furnace for a Httze treatment of material to be treated with at least one tunnel-like furnace chamber and at least a heating device is provided for heating the at least one furnace chamber and has a transport unit that transports the carrier through the furnace chamber.

11. A carrier according to claim 9 or 10, characterized in that the carrier randseltlg at least one boundary in the form of at least two or at least two edges.

12. A carrier according to any one of claims 9 to 1 1, characterized in that the carrier has a curvature and the camber of the carrier of a circular, elliptical, parabolic, sinusoidal, tangent and / or Logartthmusfunktlon follows.