EP3325265A1

EP3325265A1 - Substrate for electrical circuits and method for producing a substrate of this type

Info

Publication number: EP3325265A1
Application number: EP16745646.6A
Authority: EP
Inventors: Andreas Meyer; Karsten Schmidt
Original assignee: Rogers Germany GmbH
Current assignee: Rogers Germany GmbH
Priority date: 2015-07-17
Filing date: 2016-07-18
Publication date: 2018-05-30
Also published as: KR102295797B1; US10821704B2; CN107848245A; JP6894425B2; JP2018523593A; WO2017013073A1; KR20180030150A; DE102015111667A1; US10940671B2; JP2018533197A; US20180200990A1; US20180200989A1; KR102311944B1; KR20180030151A; JP6803369B2; WO2017013075A1; EP3325264A1; CN107848246A

Abstract

The invention relates to a substrate (1) for electrical circuits comprising at least one first composite layer (2) which is produced by means of roll cladding and, after said roll cladding, has at least one copper layer (3) and an aluminium layer (4) attached thereon, wherein at least the surface side of the aluminium layer (4) facing away from the copper layer (3) is anodised for the generation of an anodic or insulating layer (5) made of aluminium oxide, and wherein the anodic or insulating layer (5) made of aluminium oxide is connected to a metal layer (7) or at least one second composite layer (2') or at least one paper-ceramic layer (11) via at least one adhesive layer (6, 6').

Description

Substrate for electrical circuits and method for producing such

Substrates The invention relates to a substrate for electrical circuits and to a method for producing such a substrate.

Substrates for electrical circuits in the form of printed circuit boards are well known.

For this purpose, such substrates are of multilayer construction and have at least one insulating layer and at least one connected to this insulating layer

Metal layer or metallization on. The metal layer or metallization is flat with the insulation layer either directly or possibly via additional metal or

Insulation layers connected and is structured to form interconnects, contacts, contact and / or pads in several Metallisierungsflächenabschnitte.

In particular, when using such substrates in the field of power electronics, namely so-called "low voltage" applications, for example, for the construction of power semiconductor modules in a voltage range of less than 2.5 kV, it is necessary that the substrates or the insulating layer height

Insulation resistance, i. Have voltage and dielectric strength. In the field of power electronics, therefore, metal-ceramic substrates are often used whose insulation layer is characterized by at least one high

Insulation resistance having ceramic layer is formed. The ceramic layer is made of, for example, an oxide, nitride or carbide ceramic such as alumina (Al 2 O 3) or aluminum nitride (AlN) or silicon nitride (Si 3 N 4) or silicon carbide (SiC) or alumina with zirconia (Al 2 O 3 + ZrO 2).

For surface connection of the ceramic layer with at least one metal layer forming a metallization, depending on the ceramic material used and / or the metal to be bonded of the metal layer different, known per se manufacturing method use, namely, for example, a "direct copper Bonding "method, a" direct aluminum bonding "method and an" active metal bonding "method

process technology consuming and cost intensive. Also, when using conventional ceramic layers, the shape is limited.

Furthermore, methods for the production of highly filled papers are known in which the paper structure in the paper structure up to 85 wt .-% is enriched with functional fillers, for example with a sinterable ceramic powder, highly adsorptive powder or powder with good thermal conductivity. From the enriched with a sinterable ceramic powder, such as alumina powder preceramic paper is optionally after another

Deformation process by thermal reaction, i.a. Carrying out a two-stage thermal reaction, a so-called sintered paper or a paper ceramics produced. As part of the first stage of the thermal conversion, the organic components of the preceramic papers, such as pulp, starch and latex, are oxidatively removed to form a so-called "brownling." Subsequently, in a second stage of the thermal conversion, the "brownling" is sintered The result is a ceramic material with the typical bending strength of a ceramic. The microstructure of this sintered paper or of the paper ceramics shows i.a. typical for ceramics material properties, for example, a high insulation resistance. In such paper ceramics, the advantages of ceramic materials with the paper technology

Benefits, such as the simple deformation and low weight are connected together.

Based on the above-mentioned prior art, the present invention seeks to provide a substrate for electrical circuits and an associated method for producing such a substrate, which is simple and inexpensive compared to the known manufacturing processes. The object is achieved by a substrate according to the patent claim 1 and a method according to the patent claim 1 5.

The essential aspect of the substrate according to the invention for electrical circuits is to be seen in that at least one first produced by roll-plating Composite layer is provided, which after the roll cladding at least one

Copper layer and an adjoining aluminum layer has. At least the side of the aluminum layer facing away from the copper layer is anodised to produce an anodization layer made of aluminum oxide, and the anodization layer or insulating layer made of aluminum oxide is at least one anodized

Adhesive layer is connected to a metal layer or at least a second composite layer or a paper ceramic layer. The roll-laminated composite layer is fast, easy and inexpensive to produce and advantageous as a roll or

Plate goods are manufactured and processed in the subsequent processes. The

required insulation resistance of the substrate is by generating an insulating layer of alumina by appropriately oxidizing the

Achieved aluminum layer, the layer thickness can be selected depending on the required insulation properties. Here, the metal layer can assume a cooling function and a corresponding material thickness and / or

Have surface enlargement. When using a second composite layer, which is preferably constructed analogously to the first composite layer, the

Insulation resistance, in particular the voltage and dielectric strength are further increased. Alternatively, by using a

Paper ceramic layer the insulation resistance are also improved.

Advantageously, the second composite layer also has an anodizing or

Insulation layer on and the anodization of the first and second composite layer are connected to each other via the at least one adhesive layer, i. There is a direct connection between the two composite layers via at least one adhesive layer.

Alternatively, the first and second composite layers are connected to each other via at least one further intermediate layer by means of an adhesive layer in each case.

The intermediate layer is formed in one embodiment by an aluminum layer, which is used to produce two opposite Eloxal- or

Insulation layers of aluminum oxide at their opposite

Surface sides is anodized. Alternatively, the intermediate layer can be formed by a third composite layer comprising an aluminum layer, a copper layer and a further aluminum layer, wherein in each case the surface side of the aluminum layers facing away from the copper layer is used to produce two opposing anodized or

Insulating layers of aluminum oxide are anodized.

The anodization or insulating layers made of aluminum oxide of the first composite layer is preferably via an adhesive layer with the one anodization or insulating layers of aluminum oxide of the respective intermediate layer and the anodized or

Insulation layers of aluminum oxide of the second composite layer connected via a further adhesive layer with the other anodization or insulating layers of aluminum oxide of the respective intermediate layer. Due to the described construction of the intermediate layers, improved heat spreading and dissipation as well as improved insulation resistance can be achieved.

In one embodiment variant, the respective aluminum layer is led to anodized over part of its layer thickness, or the layer thickness of the insulation layer produced from the at least partially converted aluminum layer is between 5 μm and 50 μm.

Alternatively, at least one aluminum layer of the substrate can be completely anodized and thus the aluminum layer can be completely converted into the anodized or insulating layer of aluminum oxide. Particularly in the case of aluminum layers having a small layer thickness, an anodic coating is advantageous since contamination of the etching bath for introducing structuring into the copper layer through the aluminum layers can be avoided.

Advantageously, the copper layer has a layer thickness of between 35 μm and 2 mm, the aluminum layer has a layer thickness of between 10 μm and 300 μm and the

Metal lschicht a layer thickness between 300 vm and 50 mm.

In one embodiment variant of the invention, at least one aluminum layer has a profiling introduced before the anodization process is carried out, which, for example, has a multiplicity of pyramid-shaped or prism-shaped recesses includes. As a result, the surface of the subsequently generated anodization or insulation layer is increased and thus improves the adhesive force of the adhesive bond and the thermal conductivity of the substrate. With direct connection of two

Composite layers over an adhesive layer, the profiles of the respective aluminum layers are adapted to each other, in such a way that they interlock with each other.

Advantageously, an adhesive layer is used which is made of an epoxy resin adhesive, acrylic adhesive or polyurethane adhesive. The adhesive used to make the adhesive layer has an advantageous

Variant to a low viscosity in order to penetrate any cracks in the surfaces of the insulation layers and fill this can. This prevents inclusions in the substrate, in particular in the connection region, which would lead to a deterioration of the insulation resistance.

Advantageously, at least one of the copper layers for forming printed conductors, contact surfaces and / or connection surfaces is structured in a plurality of metallization sections. Preferably, the copper layer of the composite layer is patterned and forms the layout side of the substrate. With a corresponding thickness of the substrate, in particular use of two composite layers and possibly a further intermediate layer, structuring of the two metallizations of the substrate can also be carried out.

The invention likewise provides a process for producing a substrate for electrical circuits, in which at least one first composite layer is produced from a copper foil and at least one aluminum foil by means of roll cladding, the at least one copper layer and an adjoining one

An aluminum layer, in which at least the copper layer facing away from the surface side of the aluminum layer is anodized and thereby an anodic or insulating layer of aluminum oxide is produced, wherein the produced anodization or insulating layer of aluminum oxide over at least one adhesive layer with a metal layer or at least a second composite layer is glued.

The expressions "approximately", "substantially" or "approximately" in the sense of the invention mean deviations from the respective exact value by +/- 10%, preferably by +/- 5% and / or deviations in the form of insignificant for the function

Changes.

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, in principle, 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.

The invention will be explained in more detail below with reference to the figures of exemplary embodiments. Show it:

Fig. 1 is a simplified schematic sectional view through a

inventive substrate comprising a first composite layer and a metal layer,

Fig. 2 is a simplified sectional view through an alternative

Embodiment of a substrate according to the invention comprising a first and second composite layer,

Fig. 3 is a simplified sectional view through a further alternative

Embodiment of a substrate according to the invention comprising a first and second composite layer with an intermediate layer,

Fig. 4 is a simplified sectional view through a turn alternative

Embodiment of a substrate according to the invention comprising a first to third composite layer,

Fig. 5 is a simplified sectional view through a further alternative

Embodiment of a substrate according to the invention comprising a first and second composite layer, each having a profiled insulation layer, a simplified schematic sectional view through a

Inventive substrate with a paper-ceramic layer,

7 is a simplified schematic sectional view through a substrate according to FIG. 6 with a differently constructed composite layer and a solder connection to the paper-ceramic layer and FIG

8 is a schematic sectional view through an eloxal bath for anodising the aluminum layer or aluminum alloy layer of a roll-bonded composite layer.

Figure 1 shows in a simplified schematic representation a section through an inventively designed substrate 1 for electrical circuits, which has a plate-shaped and multilayer structure, i. in the form of a

Printed circuit board is formed.

The substrate 1 according to the invention consists in a first embodiment of at least one first composite layer 2, which is produced by roll-plating a Kupferfol with at least one aluminum foil. Accordingly, the first composite layer 2 has a copper layer 3 and an adjoining one

Aluminum layer 4 on.

The aluminum layer 4 is made to produce an insulating layer 5

Anodized alumina, namely, the insulating layer 5 extends

Aluminum oxide or Eloxalschicht of the facing away from the copper layer 3 surface side of the aluminum layer 4 over at least a part of

Aluminum layer 4, ie a part of the aluminum layer 4 of the first composite layer 2 is subjected to an anodization process known per se, namely an anodic oxidation, and thereby converted into an insulation layer 5 of aluminum oxide or anodized layer. The insulating layer 5 of alumina has a high voltage and dielectric strength and a thermal conductivity between 8 W / mK and 30 W / mK. The insulating layer 5 of the inventively embodied substrate 1 is connected via an adhesive layer 6, for example, with a metal lschicht 7 or glued. The adhesive layer 6 preferably extends completely over the surface of the insulating layer 5. The metal layer 7 may be formed, for example, by a further aluminum layer or an aluminum plate for cooling purposes. The metal lschicht 7 forms in a preferred embodiment of a heat sink and can on the opposite side of the adhesive layer 6 have a profile ization for increasing the surface, the most varied shape, especially in H inblick on shape, arrangement and depth of existing

Recesses may be formed.

As adhesives for producing the adhesive layer 6, it is possible to use different adhesives suitable for bonding aluminum dioxide, for example epoxy adhesives, acrylic adhesives or polyurethane adhesives. Adhesives or adhesives of low viscosity are preferably used in order to fill the porous surface of the produced anodized layer or insulation layer 5 made of aluminum oxide and thus to further increase the insulation resistance of the substrate 1.

The copper layer 3 has within the first composite layer 1 a layer thickness d 1 between 35 / vm and 2 mm and the aluminum layer 4 a layer thickness d2 between 1 0 μνη and 300 μνη, wherein the layer thickness d3 of the at least partially converted aluminum layer 4 hergestel Leten insulation layer 5 is between 5 μιη and 50 μιη. In one embodiment of the invention, the aluminum layer 4 may also be completely anodized, ie, the completely anodized aluminum layer 4 forms the insulating layer 5. The adhesive layer 6 preferably has a layer thickness d4 between 1 μνη and 20 on. The layer thickness d5 of the metal lschicht 7 is between 300 μνη and 50 mm.

The substrate 1 serves as printed circuit boards for electrical or electronic circuits or circuit modules, in particular for electronic power circuits. For this purpose, at least the copper layer 3 of the first composite layer 1 is structured by means of masking and etching technologies known per se into a plurality of metalization sections which form, for example, printed conductors, contact surfaces and / or terminal surfaces. The structuring of the copper layer 3 of the first is preferably carried out Composite layer 1 after the manufacture ment of the substrate. 1 Due to the very thin anodized or insulating layer 5 is preferably only one of

Metal lations of the substrate 1, namely the copper layer 3 of the first

Composite layer 2 structured in order to ensure sufficient stability of the substrate 1 sicherzustel len. In a corresponding stability enhancing intermediate layer, however, is also a structuring of both metal lations of the substrate 1,

For example, the metal lschicht 7 I like. The structuring of the copper layer 3 of the first composite layer 2 is preferably up to the anodized layer or

Insulation layer 5 made of aluminum oxide.

Fig. 2 shows an alternative embodiment of the substrate 1 according to Figure 1, in which instead of the metal layer 7, a second composite layer 2 'on the

Adhesive layer 6 is connected to the first composite layer 2. In the illustrated embodiment, the first and second composite layers 2, 2 'have a similar, preferably identical construction, i. the second composite layer 2 'also comprises a copper layer 3', an adjoining aluminum layer 4 ', which is at least partially converted into an insulating layer 5' of aluminum oxide or anodized layer by means of anodizing on its surface opposite the copper layer 3 '. The connected with each other

Insulating layers 5, 5 'are, for example, directly connected to one another via the adhesive layer 6. By providing two insulation layers 5, 5 ', the insulation strength of the substrate 1 increases further.

During production, firstly the first and second composite layers 2, 2 'are produced, preferably from the same roll-plated composite material layer, and then an adhesive layer 6 is applied to at least one of the insulation layers 5, 5', preferably both insulation layers 5, 5 ', the composite layers thus prepared 2, 2 'are then brought together and glued or laminated together. The adhesive or adhesive of the adhesive layer 6 is subsequently cured, for example by appropriate application of pressure and / or temperature.

Subsequently, at least one of the copper layers 3, 3 'by means of known masking and etching techniques for training several Metallization sections structured. After a final cleaning of the already

structured substrate 1 can still be performed an edge seal, but this is not mandatory. Also, a preparation of the substrates 1 according to the invention in the form of

Multiple substrates are possible, which are separated after the production to the desired "single" substrates 1. The singulation takes place in the

Inventive substrates 1, for example by means of mechanical

Machining operations such as sawing, cutting or punching or using a laser unit. Accordingly, the unstructured extends

Metal layer 7 different from the prior art preferably also up to the edge of the cut edge of the respective substrate. 1

FIG. 3 shows a further alternative embodiment variant of a substrate 1 according to the invention, in which a further aluminum layer 4 "is arranged to further increase the stress and breakdown strength between the first and second composite layers 2, 2 'according to the embodiment of FIG Top and bottom to produce an insulating layer 5 "of alumina are each anodized. Alternatively, only one alumina insulating layer 5 "may be provided, i.e., the additional aluminum layer 4" is completely anodized. The insulation layer or insulation layers 5 '' are connected to the insulation layers 5, 5 'of the first and second composite layers 2, 2' via an adhesive layer 6, 6. 'In a further alternative embodiment variant according to Fig. 4, between the first and second composite layers 2, 2 'of the substrate 1 according to FIG. 2, a third composite layer 2 "' consisting of a central copper layer 3" whose top and bottom is provided with an aluminum layer 4 ", 4" ', wherein the respective aluminum layer 4 ", 4" 'analogous to the aforementioned embodiments each have an insulating layer 5'. The connection of the insulation layers 5, 5 ', 5 "of the first to third composite layer 2, 2', 2" takes place in turn via one in each case

Adhesive layer 6, 6 '. Advantageously, the copper layer 3 "can also be used electrically and structured, for example, into a plurality of metallization sections be. It is understood that several central copper layers 3 "can be provided.

In order to improve the heat transfer properties of the substrate 1, in an alternative embodiment according to FIG. 5, a profiling is introduced into the respective aluminum layer 4, 4 'before the anodization process is carried out,

for example in the form of pyramidal or prismatic recesses. The introduction of the profiling in the respective aluminum layer 4, 4 'can be done for example by embossing by means of rolling or by wheels. As a result, the thermal resistance of the substrate 1 can be reduced again. Preferably, an aluminum layer 4, 4 'with an increased layer thickness d2 between 0.1 mm and 1 mm is used here.

Also, in an embodiment variant, not shown, copper layer 3, 3 'with greater layer thicknesses d1 of the first and / or second composite layer 2, 2' according to FIGS. 2 and 5 prior to the production of the adhesive connection 6, in particular after anodization of the aluminum layer 4, 4 'are already structured before

preferably by punching, laser cutting or water jet cutting, i. without

Use of a sophisticated masking and etching technology. This makes it possible to reduce the Isograbenbreiten between the structured copper sections.

In the method for producing such substrates 1 according to the invention, the composite layers 2, 2 ', 2 "are formed by roll-plating a copper foil with a

Aluminum foil or an aluminum foil, a copper foil and another

Aluminum foil produced, preferably in the form of a band. However, it is understood that the described composite layers 2, 2 ', 2 "can be manufactured as plate goods, so that the plate-rolled, but not yet anodized composite layers 2, 2', 2" can advantageously be either as a strip on a roll or in sheet form be provided for the further manufacturing process.

The subsequent anodization of the aluminum layer 4, 4 'of the prepared

Composite layer 2, 2 ', 2 "is preferably carried out in a continuous installation or in a corresponding immersion basin. 2 'connected by applying the adhesive layer 6, 6' either with each other or with the metal layer 7. Before or after complete curing of the

Adhesive layer 6, 6 'takes place a cutting of the tape or plate goods and subsequent drying. The dried individual layers or plates, which may each be formed as multiple substrates, are subsequently masked and etched by means of known masking and etching technologies and thereby a predetermined structuring of at least one of the copper layers 3, 3 'is carried out. Alternatively, in the case of copper layers 3, 3 'of increased layer thickness, the structuring of the

Copper layers 3, 3 'carried out by punching or cutting by means of a laser unit or a water jet unit. After a final cleaning, the substrates 1 can be separated, preferably using a laser unit or a mechanical separation method.

Under copper layer 3, 3 ', 3 "we also in the sense of the invention also a

Copper alloy layer understood.

In an alternative embodiment of the substrates 10 according to the invention according to FIGS. 6 and 7, the insulation strength of the substrate 10 is further increased by the fact that instead of the metal layer 7, a paper-ceramic layer 11 is used. For this purpose, the substrate 10 has a composite layer 12 with a metal layer 1 3 and at least one aluminum layer 14. The aluminum layer 14 of the

Composite layer 12 is therefore also at least partially anodized, so that an anodized layer 1 5 is formed, which in turn is connected via an adhesive layer 16 with the paper ceramic layer 1 1. The anodizing layer 15 serves here

especially as an adhesion promoter, to the inherently smooth surface of the

Aluminum layer 14 by the roughened anodized 1 5 to replace the high adhesive force of the adhesive bond between the paper-ceramic layer 1 1 and the

Composite layer 12 ensures. In this context, a paper-ceramic layer 1 1 is understood as meaning a paper structure enriched in papermaking with a sinterable ceramic powder, preferably alumina powder, from which a preceramic paper structure is produced. The proportion of the sinterable ceramic powder in the total volume of the preceramic paper structure is preferably between 80 and 90% by weight. The preceramic paper structure is subjected to a two-stage thermal conversion process and in the first stage from the preceramic

Paper structure ("Green ing") initially produces a "Braunl ing", in which the organic components of the preceramic paper structure, such as Zel material, starch and latex are oxidatively removed. Subsequently, in the second stage, the "browning" is fed to a sintering process, whereby a ceramic material, namely the paper ceramics with the typical material properties of a ceramic material is formed, such as a high bending and insulation strength

However, paper-ceramic layer 11 is compared to a conventional one

Ceramic layer lighter and before performing the thermal

Implementation process individually deformable. Also, that can be beneficial

Starting material of the paper-ceramic layer 1 1, and that the preceramic

Paper structure due to the deformability as Rol lenware stored and

be further processed. The paper-ceramic layer 1 1 used according to the invention has, for example, a layer thickness d6 of between 50 and 600 μm, preferably 80 μm and 1 50 μm, and has an E-modulus between 90 σ Pa and 1 50 σ Pa.

The structuring of the metal lschicht 1 3 again takes place by means of per se known masking and etching technologies, preferably after manufacture ment of

Adhesive bond with the paper-ceramic layer 1 1.

In a further embodiment, a composite layer 12 'is used, which in addition to the copper layer 1 3 and the aluminum layer 14 a thereto

Subsequently, aluminum-silicon layer 18, which is also manufactured by roll-plating, and that is preferably initially a composite of the

Aluminum layer 1 4 an adjoining aluminum-silicon layer 1 8 produced by roller cladding and this composite again with the copper layer 1 third

roll-bonded. The aluminum-silicon layer 1 8 of the composite layer 1 2 'is connected to the paper-ceramic layer 1 1 via a solder layer 1 9. An appropriately designed substrate 10 is schematically illustrated, for example, in FIG. 7. The soldering of the paper oxide layer 1 1 made of aluminum oxide is carried out under protective gas, for example N 2 or AR, and using the aluminum silicon eutectic. According to the invention, cracks are also poured out in the insulating layers 5, 5 'when a low-viscosity adhesive is used, for example, by the composite layer 2, 2' being heated accordingly, but below that

Curing temperature of the adhesive to selectively create cracks at vulnerabilities, in which the adhesive can then penetrate. Also, by using the appropriate process temperature of 120 ° C up to 1 60 ° C existing cracks are widened and can thus easily be filled with adhesive. The

Temperature increase can be done stepwise or continuously over a given period. Advantageously, in a step-like

Temperature increase evaporation of any glue contained in the adhesive

Binder. The curing temperatures of common adhesives are included

for example, over 180 ° C. To improve the conductivity of the adhesives used, these can also be used in one embodiment of the invention

Nanofibers be enriched.

Preferably, the composite layers 2, 2 'produced by roll cladding have a significantly thinner aluminum layer 4, 4', 4 "compared to the copper layers 3, 3 ', and the layer thickness d2 of the aluminum layer 4, 4', 4" is less than half the layer thickness d1 of the copper layers 3, 3 ', preferably even less than one third of the layer thickness d1 of the copper layers 3, 3'.

In particular, here a complete conversion of the aluminum layer 4, 4 ', 4 "by corresponding anodizing in the insulating layer 5, 5', 5" advantageous because contamination of the etchant by dissolving aluminum from the at least partially existing aluminum layer 4, 4 ', The layer thickness of the aluminum layer 4, 4 ', 4 "remaining after the conversion into the insulating layer 5, 5', 5" is thus preferably kept as low as possible.

Also, the adhesive bond between the different composite layers or layers can be carried out after applying the adhesive in the composite by means of lamination or rolling in order to keep the thickness d4 of the adhesive layer 6 low.

Furthermore, the substrates 1 can be subjected to a vacuum after the application of the adhesive to any gas influences present in the anodization layer or insulation layer 5 made of aluminum oxide, which causes an increase and thus deterioration of the

Insulation resistance contribute to be able to remove.

In a further embodiment variant, the respective adhesive layer 6, 6 ', 6 "has at least two different adhesives, which are preferably applied one behind the other in a layer-like manner

different viscosity are used, wherein the one adhesive with lower viscosity for filling defects such as cracks or pores in the respective anodizing layer 5, 5 ', 5 "and the further adhesive with higher viscosity for the preparation of the adhesive bond of the layer composite is provided.

For example, gluing with an epoxy adhesive and filling the imperfections with only pure epoxy, i. done without hardener. Advantageously, the epoxy can be processed at a higher temperature compared to the epoxy adhesive to reduce its viscosity. Also can excess

Filling material, in particular epoxy are removed, so that essentially remains only in the defects epoxide. The next step will be the

Epoxy adhesive applied. The hardener portion of the epoxy adhesive also diffuses into the pure, already processed epoxide in the filled defects and also hardens them with.

When anodizing rolled-laminated composite layers 25 comprising a copper layer or copper alloy layer 23 and an aluminum layer or

Aluminum alloy layer 24, it is imperative that both metals do not come into contact with the electrolyte 21 of an anodizing bath 20, otherwise a kind of short circuit is generated parallel to the anodizing surface of the aluminum layer or aluminum alloy layer 24 via the copper layer or copper alloy layer 23. This short-circuit prevents sufficient voltage from building up via the thin oxide layer (AI2O3), which is usually already present before the anodizing treatment. This resulting voltage penetrates locally the thin oxide layer (AI2O3) and leads to the oxidation of the underlying aluminum to alumina. FIG. 8 shows, by way of a schematic drawing, a corresponding eloxal bath 20 with a cathode 22 and the anode formed by the copper layer or copper alloy layer 23, against which a DC voltage U is applied. The inventors have recognized that the occurrence of such a short circuit can be counteracted by complete masking or covering of the surfaces of the copper layers 23 by a frame-shaped cover element, ie the contact of the electrolyte 21 with the copper layers 23 is effectively prevented, whereas that for the Anodizing required contact with the aluminum layer 24 is still given. The masking can be done in an alternative embodiment by applying a protective film or a protective lacquer or a combination thereof. Common to each of these methods is the sealing effect against the electrolyte 1 1.

In an alternative embodiment, a masking or covering of the electric field by auxiliary electrodes 26, for example metallic sheets or components, which may be provided with a corresponding coating and which is resistant to the chemical components of the Eloxalbades 20 used and the present electric fields. The auxiliary electrodes 26 are electrically connected to the anode, so that the Geleichspannung U or the resulting electric field between the auxiliary electrode 26 and the surface of the

Copper layer 23 of the composite layer 25 is zero. This is no

"Mechanical" sealing of the surfaces of the copper layers is required, provided that no chemical treatment of the copper layer 3. The "sealing" of the copper layer 23 thus takes place without contact.

In an advantageous embodiment, the distance x between the

Frame-like auxiliary electrode 25 and the aluminum layer or

Aluminum alloy layer 24 of the composite layer 25 received therein is greater than 0mm but less than 10mm, preferably between 0 and 1mm.

The invention has been described above by means of exemplary embodiments. It is understood that numerous changes and modifications are possible, without thereby departing from the invention underlying the idea of the invention. LIST OF REFERENCE NUMBERS

1 substrate

2 first composite layer

2 'second composite layer

2 "third composite layer

3, 3 ', 3 "copper layer

4, 4 ', 4 ", 4'" aluminum layer

5, 5 ', 5 "Eloxalschicht or insulation layer of alumina

6, 6 ', 6 "adhesive layer

7 metal layer

10 substrate

1 1 paper ceramic layer

12, 12 'composite layer

1 3 metal layer, in particular copper layer

14 aluminum layer

15 anodized or insulating layer of aluminum oxide 16 adhesive layer

18 aluminum-silicon layer

19 solder layer

20 eloxal bath

21 electrolyte

22 cathode

23 copper layer or copper alloy layer

24 aluminum layer or aluminum alloy layer

25 composite layer

26 auxiliary electrode

P profiling

d1 - d6 layer thicknesses

U DC voltage X distance

Claims

claims

1 . Substrate (1, 10) for electrical circuits comprising at least one first composite layer (2) produced by means of roll cladding, which differs according to the

Roll cladding at least one copper layer (3) and an adjoining aluminum layer (4), in which at least the surface of the aluminum layer (4) remote from the copper layer (3) is anodised to produce an anodization layer (5) of aluminum oxide, and in which the anodization or insulation layer (5) made of aluminum oxide is connected via at least one adhesive layer (6, 6 ') to a metal layer (7) or at least one second composite layer (2') or at least one paper ceramic layer (11).

2. Substrate according to claim 1, characterized in that the second

Composite layer (2 ') is constructed analogously to the first composite layer (2).

3. Substrate according to claim 1 or 2, characterized in that the second composite layer (2 ') an Eloxal- or insulating layer (5') and the Eloxal- or insulating layers (5, 5 ') of the first and second composite layer ( 2, 2 ') via which at least one adhesive layer (6) are interconnected.

4. Substrate according to claim 1 or 2, characterized in that the first and second composite layer (2, 2 ') via at least one further intermediate layer by means of an adhesive layer (6, 6') are interconnected.

5. A substrate according to claim 4, characterized in that the intermediate layer is formed by an aluminum layer (4 ") which is anodized to produce two opposite Eloxal- or insulating layers (5") of alumina at their opposite surface sides.

6. The substrate according to claim 5, characterized in that the intermediate layer is formed by a third composite layer (5 ") comprising an aluminum layer (4"), a copper layer (3 ") and a further aluminum layer (4"'), wherein each of the copper layer (3 ") facing away from the surface of the aluminum layers (4", 4 "') for producing two gegenüberl iegender anodization or insulation layers (5") are made of alumina anodized.

7. Substrate according to claim 5 or 6, characterized in that the Eloxalbzw. Insulating layers (5) of aluminum oxide of the first composite layer (5) via an adhesive layer (6) with the one anodization or insulating layers (5 ") of alumina of the intermediate layer and the anodization or

Insulation layers (5 ') of aluminum oxide of the second composite layer (5') via a further adhesive layer (6 ') with the other anodizing or

Insulation layers (5 ") made of aluminum oxide of the intermediate layer is connected.

8. Substrate according to one of the preceding claims, characterized in that the respective aluminum layer (4, 4 ', 4 ") over part of their

Layer thickness (d2) is anodized and / or that the layer thickness (d3) of the at least partially converted aluminum layer (4, 4 ', 4 ") hergestel-ended insulation layer (5, 5', 5") is between 5 vm and 50 jum ,

9. Substrate according to one of claims 1 to 8, characterized in that

at least one aluminum layer (4, 4 ', 4 ") of the substrate (1) is completely anodized and the aluminum layer (4) is completely in the anodized or

Insulating layer (5) is converted from Al uminiumoxid.

10. Substrate according to one of the preceding claims, characterized in that the copper layer (3, 3 ', 3 ") a layer thickness (d 1) between 35 μιτι and 2 mm, the aluminum layer (4, 4', 4") has a layer thickness (d2) between 1 0 μνη and 300 jum and the metal lschicht (7) has a layer thickness (d5) between 300 μνη and 50 mm.

1 1. Substrate according to one of the preceding claims, characterized in that at least one aluminum layer (4, 4 ', 4 ") has an introduced prior to the implementation of the anodizing process profiling (P), which includes, for example, a plurality of pyramid or prism-shaped recesses ,

12. Substrate according to one of the preceding claims, characterized in that the first and second composite layer (2, 2 ') are made by roll-plating a copper foil with at least one aluminum foil.

13. Substrate according to the preceding claims, characterized in that the adhesive layer (6, 6 ', 6 ") is made of an epoxy resin adhesive, acrylic adhesive or polyurethane adhesive and / or that for producing the adhesive layer (6, 6 ', 6 ") has a low viscosity.

14. Substrate according to the preceding claims, characterized in that at least one of the copper layers (3, 3 ') to form conductor tracks, contact and / or pads is structured in a plurality of metallization.

15. A method for producing a substrate (1, 10) for electrical circuits, wherein at least one first composite layer (2, 2 ') is produced from a copper foil and at least one aluminum foil by means of roll cladding, the at least one copper layer (3, 3'). and an adjoining one

Aluminum layer (4, 4 '), in which at least the copper layer (3, 3') facing away from the surface of the aluminum layer (4, 4 ') is anodized and thereby an anodic or insulating layer (5) is produced from aluminum oxide, and in which the generated anodization or insulation layer (5)

Alumina over at least one adhesive layer (6, 6 ') with a

Metal layer (7) or at least a second composite layer (2 ') or at least one paper ceramic layer (11) is glued.