DE102013104739A1 - Metal-ceramic substrate and method for producing a metal-ceramic substrate - Google Patents

Abstract

The invention relates to a metal-ceramic substrate and an associated method for its production, which has at least one ceramic layer (2) which is coated on at least one surface side (2.1) with at least one metallization (3) with a layer thickness (D) of at least 0 , 1 mm is provided, the metallization (3) being structured in such a way that in the outer edge region (3 ') of the structured metallization (3), in order to form conductor tracks and / or contact or connection surfaces (5, 5a, 5b) A metallization section (3a, 3b) with a reduced layer thickness (DR) extending at least in sections along the outer edge region (3 ') is produced. The metallization section (3a, 3b) of reduced layer thickness is particularly advantageously provided with a layer of a filler material (6).

Description

The invention relates to a metal-ceramic substrate according to the preamble of patent claim 1 and to a method for producing a metal-ceramic substrate according to the preamble of patent claim 15.

Metal-ceramic substrates in the form of printed circuit boards consisting of a ceramic layer and at least one metallization connected to a surface side of the ceramic layer and structured to form printed conductors, contacts, contact surfaces or connection surfaces are known in various designs. Such metal-ceramic substrates are used, for example, for the construction of power semiconductor modules.

• – Oxidieren einer Kupferfolie derart, dass sich eine gleichmäßige Kupferoxidschicht ergibt;
• – Auflegen des Kupferfolie mit der gleichmäßige Kupferoxidschicht auf die Keramikschicht;
• – Erhitzen des Verbundes auf eine Prozesstemperatur zwischen etwa 1025 bis 1083°C, beispielsweise auf ca. 1071°C;
• – Abkühlen auf Raumtemperatur.

For joining metallization-forming metal foils or metal layers with each other or with a ceramic substrate or a ceramic layer, the so-called "DCB method"("direct copper bonding") is also known. Here, metal layers, preferably copper layers or foils are connected to each other and / or with a ceramic layer, using metal or copper sheets or metal or copper foils, on their surface sides of a layer or a coating ("reflow layer") a chemical compound of the metal and a reactive gas, preferably oxygen. In this example, in the US-PS 37 44 120 or in the DE-PS 23 19 854 described method, this layer or coating ("reflow layer") forms a eutectic having a melting temperature below the melting temperature of the metal (eg copper), so that by placing the metal or copper foil on the ceramic layer and by heating all the layers are joined together can, by melting the metal layer or copper layer substantially only in the region of the Aufschmelzschicht or oxide layer. Such a DCB method then has, for example, the following method steps:

• - Oxidizing a copper foil such that a uniform copper oxide layer results;
• - placing the copper foil with the uniform copper oxide layer on the ceramic layer;
• - Heating the composite to a process temperature between about 1025 to 1083 ° C, for example, to about 1071 ° C;
• - Cool to room temperature.

Furthermore, from the publications DE 22 13 115 and EP-A-153 618 the so-called active soldering method for joining metallization-forming metal layers or metal foils, in particular also of copper layers or copper foils with a ceramic material or a ceramic layer. In this method, which is also used specifically for the production of metal-ceramic substrates, at a temperature between about 800-1000 ° C, a connection between a metal foil, such as copper foil, and a ceramic substrate, such as an aluminum nitride ceramic, under Use of a brazing alloy, which also contains an active metal in addition to a main component such as copper, silver and / or gold. This active metal, which is, for example, at least one element of the group Hf, Ti, Zr, Nb, Ce, establishes a bond between the braze and the ceramic by a chemical reaction, while the bond between the braze and the metal forms a metallic braze joint is.

Also known are methods for bonding an aluminum layer to a ceramic layer under the name "Direct Aluminum Bonding" ("DAB method"). In principle, adhesive bonds or adhesive techniques using plastic adhesives, for example using epoxy resin-based adhesives, can also be used for such a bonding of two layers, in particular also fiber-reinforced adhesives. Also known in particular is the use of special adhesives containing carbon fibers and / or carbon nanofibers and / or carbon nanotubes, and / or adhesives, with which a thermal and / or good electrical conductive adhesive bond is possible. Said connection technologies can, of course, also be used in combination when providing a plurality of metal layers on both the lower and the upper side of the ceramic layer.

It is known that such metal-ceramic substrates are subject to high thermal cycling in many applications, in which, for example, temperature changes between -40 ° C and + 125 ° C may occur. Due to the different coefficients of thermal expansion of the ceramic layer and the metallization or metal layer arise at the transition between these layers in temperature fluctuations considerable mechanical compressive or tensile stresses whose gradient in the ceramic material at the edge of the metal layer is particularly large and leads to cracks in the surface of the ceramic layer ,

It is also known that the gradient of the tensile and compressive stresses can be reduced by structuring the metallization or metal layer, which is already often predetermined by the layout required for the circuit.

To avoid such cracking and increase the thermal shock resistance of the metal-ceramic substrate different measures are already known. For example, is from the DE 40 04 844 C1 Already a method for producing a patterned copper metallization of a metal-ceramic substrate known in which by appropriate etching techniques, a structured metallization is created, which is locally weakened at their edges to reduce the gradient of the tensile and compressive stresses. The teachings taught here include in their generally held form also previously known embodiments of printed conductors, contact surfaces or the like. Structured metallizations as well as edge attenuation, as inevitably obtained in the etching of structures of metallizations and can not be avoided.

Based on the above-mentioned prior art, the present invention seeks to show a metal-ceramic substrate and associated method for producing a metal-ceramic substrate, which has an improved thermal shock resistance. The object is achieved by a metal-ceramic substrate or a method for its production according to the claims 1 and 15, respectively.

The essential aspect of the metal-ceramic substrate according to the invention is to be seen in that the layer thickness-reduced metallization section is provided with a layer of a filling material. A particularly advantageous improvement in the thermal shock resistance is achieved by the coating according to the invention of the layer thickness-reduced edge region of the structured metallization. The filling material used is preferably compatible with various metallization processes, for example nickel bath, gold bath, silver bath and also acid and alkali resistant. Finally, the filler also has a heat resistance greater than 350 ° C.

In a first embodiment of the metal-ceramic substrate according to the invention, the coating-reduced metallization section is particularly advantageously formed by a step-like outer edge section of the metallization, which is preferably coated with the filler material over its full area. The reduced layer thickness of the metallization section and the layer thickness of the filler material in total approximately correspond to the layer thickness of the metallization, i. The result is a flush transition between the top metallization and top of the layer of filler. Also, the layer of filler material may extend over the outer edge portion into the subsequent etched portion of the ceramic layer.

In a second embodiment variant of the metal-ceramic substrate according to the invention, the layer thickness-reduced metallization section is formed by a recess which preferably has a trough-like cross section in the outer edge region of the metallization. Advantageously, the etching of such a recess having a trough-like cross-section results in a recess edge which effectively prevents edge-side outflow of the filling material into the region of the ceramic layer being etched free. Preferably, the trough-like recess is completely filled with the filling material.

In a further advantageous embodiment variant, the metal-ceramic substrate according to the invention is designed such that the layer thickness-reduced metallization section is produced by corresponding masking and etching of the metallization and / or by a mechanical surface treatment, in particular milling and / or
that the outer edge region includes a central metallization region, which forms a contact or bonding surface for connection of an electrical component, and / or
that the filler material is made of a plastic material with a ceramic component and / or a graphitized carbon component, wherein as plastic material, for example, polyimide, polyamides, epoxide or polyetheretherketone and as a ceramic component, for example, silicon nitride, aluminum nitride, alumina or glass are provided, and / or
that the thermal expansion coefficient of the filling material is smaller than the thermal expansion coefficient of the metallization, and / or
in that the ceramic layer is made of oxide, nitride or carbide ceramics such as aluminum oxide or aluminum nitride or silicon nitride or silicon carbide or aluminum oxide with zirconium oxide, and / or
that the further surface side of the ceramic layer is provided with at least one further metallization, wherein the aforementioned features may in turn be provided individually or in any desired combination.

The invention further provides a method for producing a metal-ceramic substrate comprising at least one ceramic layer which is provided on at least one surface side with at least one metallization having a layer thickness of at least 0.1 mm, in which for the formation of conductor tracks and / or Contact or pads the metallization is structured such that in the outer edge region of the patterned metallization is at least partially along the outer edge region extending Metallisierungsabschnitt with reduced thickness is generated. According to the invention, the layer thickness-reduced metallization section is coated with a filling material. Advantageously, the inventive method is technically easy to implement, so that for the production of no appreciable additional effort is required according to the invention metal-ceramic substrates.

In an advantageous embodiment variant of the method according to the invention, an etching resist layer is applied to the metallization, specifically where the metallization with the existing layer thickness is to remain. Subsequently, the metallization provided with the etching resist layer for producing the layer thickness reduced metallization section is applied with an etching solution until openings of a predetermined depth in the areas of the metallization released by the etching resist layer are etched free. The etching resist layer is removed again from the metallization and the etched-out recesses are filled with the filling material, preferably completely. Finally, at least partially on the metallization and on the layer of the filling material, a further Ätzresistschicht is applied, namely, where the metallization and the layer of the filler material to form one or more pads remain and the released from the further Ätzresistschicht areas of the metallization subjected to an etching solution and completely removed to the ceramic layer.

The expressions "approximately", "substantially" or "approximately" in the context of the invention mean 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.

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

1 a simplified sectional view through a first embodiment of a metal-ceramic substrate according to the invention,

2 a simplified sectional view through a second embodiment of a metal-ceramic substrate according to the invention,

3 5 is a simplified sectional view through a third embodiment of a metal-ceramic substrate according to the invention,

4 a simplified plan view of the metal-ceramic substrate according to 1 .

5 a simplified plan view of the metal-ceramic substrate according to 2 .

6 a simplified sectional view through a metal-ceramic substrate comprising a full surface applied to a ceramic layer metallization,

7 the metal-ceramic substrate according to 6 after application of an etching resist layer,

8th the metal-ceramic substrate according to 7 with the applied Ätzresistschicht and after the etching away of recesses in the metallization,

9 the metal-ceramic substrate according to 8th after removing the etch resist layer,

10 the metal-ceramic substrate according to 9 after application of a further etching resist layer,

11 the metal-ceramic substrate according to 10 after removing the marginal metallization by means of etching,

12 the metal-ceramic substrate according to 11 after removing the further etching resist layer,

13 the metal-ceramic substrate according to 7 after introducing channel or web-like recesses into the metallization,

14 the metal-ceramic substrate according to 13 after introducing a peripheral stepped recess into the metallization by means of etching,

15 the metal-ceramic substrate according to 14 after filling the etched areas with the filling material and then removing the further etching resist layer,

16 the metal-ceramic substrate according to 7 after introducing channel or web-like recesses into the metallization,

17 the metal-ceramic substrate according to 13 after introducing an edge-stepped recess in the metallization by means of etching and removing the edge metallization sections and

18 the metal-ceramic substrate according to 17 after filling the stepped edge region and a part of the subsequent surface of the Ceramic layer with the filling material and subsequent removal of the further Ätzresistschicht.

1 shows in a simplified schematic representation of a section through an embodiment variant of a metal-ceramic substrate according to the invention 1 comprising at least one ceramic layer 2 with two opposite surface sides, a first and second surface side 2.1 . 2.2 ,

2 and 3 also show schematic sectional views of further embodiments and 4 shows a plan view of the first surface side 2.1 the metal-ceramic substrate according to the invention 1 according to 1 and 5 a plan view of the first surface side 2.1 the metal-ceramic substrate according to the invention 1 according to 2 ,

The first surface side 2.1 is in the present embodiment with at least one metallization 3 provided, which is preferably formed or made by a film or layer of copper or a copper alloy and which directly and flat on the ceramic layer 2 is applied. In one embodiment of the invention, that of the first surface side 2.1 opposite second surface side 2.2 with another metallization 4 provided, which are preferably also formed or made by a foil or layer of copper or a copper alloy and / or aluminum or an aluminum alloy. Preferably, the metallizations 3 . 4 a layer thickness D of at least 0.1 mm, preferably between 0.3 mm and 0.8 mm, and when realized in aluminum or an aluminum alloy, a layer thickness D between 0.1 mm and 25 mm, preferably between 0, 3 mm and 3.0 mm.

The metallizations 3 . 4 Of copper or a copper alloy are preferably directly using the DCB method described above surface with the first and second surface side 2.1 . 2.2 the ceramic layer 2 connected. The ceramic layer 2 Here, for example, from an oxide, nitride or carbide ceramics such as alumina (Al2O3) or aluminum nitride (AlN) or silicon nitride (Si3N4) or silicon carbide (SiC) or alumina with zirconia (Al2O3 + ZrO2) and has a layer thickness, for example between 0 , 1 mm and 1.0 mm, preferably between 0.2 mm and 0.7 mm.

In the present embodiment, the one with the first surface side 2.1 areal connected metallization 3 for forming at least one connection region or a connection surface 5 for at least one electronic component, in particular semiconductor component 7 structured formed. The structuring of the metallization 3 Preferably, by appropriate masking and subsequent etching of a full surface on the ceramic layer 2 applied still unstructured metallization (see 6 ), wherein the structuring is already at least partially predetermined due to the layout required for the circuit. The metallization 3 Thus, it can also be further structured for the formation of printed conductors, contacts and / or further fastening regions.

In the present embodiment, the basic idea of the invention is based on, for example, a rectangularly structured metallization 3 for forming a connection surface 5 explains in more detail which completely of etched areas 2 ' the ceramic layer 2 is surrounded. It is understood that based on this basic idea, a plurality of different structuring of the metallization 3 a metal-ceramic substrate 1 can be produced, which are also supported by the inventive concept.

As already well known in case of temperature fluctuations in the etched areas 2 ' the ceramic layer 2 Tensile stresses on, while those with the structured metallization 3 connected areas of the ceramic layer 2 are under compressive stress.

This may be due to the gradient of the tensile and compressive stresses at the transition between the structured metallization 3 to the non-metallized areas 2 ' the ceramic layer 2 of the metal-ceramic substrate 1 cracking in the ceramic layer 2 come.

To reduce these mechanical stresses in the ceramic layer 2 and thus improving the thermal shock resistance indicates the patterned metallization 3 an outer edge area 3 ' which has a preferably central metallization region 3 '' for surface connection of the electronic component 7 surrounds, which is structured such that in the outer edge region 3 ' the structured metallization 3 at least partially along the outer edge region 3 ' extending metallization section 3a . 3b with reduced layer thickness DR arises. According to the invention, this layer thickness reduced metallization section 3a . 3b with a layer of a filler 6 Mistake. In this case, the portion of the structured metallization removed due to the layer thickness reduction becomes 3 through the layer of filler, so to speak 6 "Filled up", whereby an increase in thermal shock resistance is achieved.

In 1 is, for example, a first embodiment of the metal-ceramic substrate according to the invention 1 illustrated, according to the layer thickness reduced metallization section by a stepped outer edge portion 3a the metallization 3 is formed, ie, the layer thickness D of the patterned metallization 3 is in the area of the outer edge area 3 ' reduced so that a step-like edge portion 3a arises, ie a stepped transition S from the central metallization section 3 '' in the outer edge area 3 ' , Both the width B and the reduced layer thickness DR are dependent on the external dimensions and the layer thickness D of the metallization 3 However, for reasons of electrical conductivity, the reduced layer thickness DR is half the layer thickness D of the metallization 3 should not fall below. For example, at a layer thickness D of the metallization 3 of about 0.3 mm, the step-like edge portion 3a a width B between 0.2 mm and 0.3 mm and a reduced layer thickness DR between 0.1 mm and 0.15 mm.

Alternatively or additionally, the layer thickness reduced metallization section may also be formed by a plurality of recesses of different shape and size.

The recesses may be formed by oval, slot-shaped, karo or diamond-shaped depressions and / or by a meandering, stampmark edge-shaped or sawtooth-shaped edge profile of the layer thickness-reduced metallization section. Due to the recesses is an increase in the strength of the connection between the filler material 6 and the metallization 3 possible.

The step-like edge section 3a is preferably such with the filler material 6 Coats that a nearly flush transition between the central metallization region 3 '' the structured metallization 3 and the surface of the layer of the filler 6 arises. Also, the surface of the filler material can 6 above the level of the central metallization area 3 '' the structured metallization 3 stand out.

In a second embodiment of the metal-ceramic substrate according to the invention 1 according to 2 is the layer thickness reduced metallization section by a trough-like cross-section having recess 3b in the outer edge area 3 ' the metallization 3 formed by appropriately masking and etching the top of the metallization 3 is produced. This trough-like recess 3b is preferably complete with the filler material 6 filled, so preferably one with the top of the metallization 3 flush closure of the trough-like recess 3b through the layer of filler material 6 given is. The trough-like recess 3b extends along the outer edge region 3 ' the structured metallization 3 , wherein the layer thickness D of the metallization 3 in the central metallization area 3 '' having, preferably circumferential recessed edge 3b ' arises. Furthermore, the trough-like recess 3b at layer thickness D of 0.3 mm of the metallization 3 For example, a width B 'between 0.2 mm and 0.3 mm and a depth T between 0.1 mm and 0.15 mm.

As filler 6 preferably uses a plastic material, preferably epoxy resins with a proportion of a ceramic material or graphitized carbon application. For example, polyimide or polyamides can be used as the plastic material and silicon nitride, aluminum nitride, aluminum oxide or glass as the ceramic material, namely ALN, Si ₃ N ₄ , SiC, AL ₂ O ₃ . The thermal expansion coefficient or coefficient of thermal expansion of the filling material 6 is preferably smaller than the thermal expansion coefficient or thermal expansion coefficient of the metallization 3 selected. Furthermore, the filler material 6 For example, a relative permittivity or dielectric constant between 2.5 and 6.5, preferably between 3.2 and 4.0.

In a third embodiment of the metal-ceramic substrate according to the invention 1 according to 3 is the layer thickness reduced metallization again in the form of a stepped outer edge portion 3a the structured metallization 3 analogous to 1 educated. Here, however, different from the first embodiment, the layer of the filler extends 6 over the outer edge area 3 ' the metallization 3 in the etched area 2 ' the ceramic layer 2 ie the transition area between the outer edge section 3a the structured metallization 3 and the etched area 2 ' the ceramic layer 2 is complete with the filler 6 sealed or filled. In this embodiment, a part of the layer of the filler material 6 both with the structured metallization 3 as well as with the ceramic layer 2 connected areally.

Furthermore, the subject matter of the invention is a method for producing a metal-ceramic substrate described above 1 whose essential procedural steps in the 5 to 15 are shown by way of example.

In 6 is an example of a cross section through a metal-ceramic substrate 1 shown, which consists essentially of a ceramic layer 2 and one with the first surface side 2a the ceramic layer 2 Fully connected and still unstructured metallization 3 consists. The connection of metallization 3 , which is preferably made of copper or a copper alloy, with the ceramic layer 2 takes place via the DCB method described above. It is understood that also a metallization 3 may be provided of aluminum or an aluminum alloy, which via a direct aluminum bonding method with the ceramic layer 2 is connected flat. Likewise, further connection methods described at the outset, such as an active soldering method or a suitable adhesive method, can be used. In 6 is merely an example only a first metallization 3 intended. Other metallizations 4 have been omitted for clarity.

According to 7 is in a first step on the still unstructured metallization 3 an etch resist layer 8th applied, where the metallization 3 made of copper or a copper alloy with layer thickness D should remain. The etch resist layer 8th is generated by means of per se known techniques. For example, by applying a photoresist layer with appropriate masking of the surface of the metallization 3 , then exposing and curing the photoresist layer.

In 7 are already by means of dashed lines those, not from the Ätzresistschicht 8th covered areas of metallization 3 indicated which are to be removed by etching in the subsequent second process step. For this purpose, in the second process step with the Ätzresistschicht 8th provided metallization 3 subjected to an etchant, and for a predetermined period of time. The time is dependent on etchant and dimensioned such that recesses 9 desired depth T from the metallization 3 be etched. 8th shows this with the etch resist layer 8th provided metal-ceramic substrate 1 after performing the etching step and the recesses exposed by the etching 9 ,

In a subsequent third process step, the etching resist layer is now 8th from the surface of the metallization 3 removed, using known per se solvents. In the present embodiment, the metal-ceramic substrate 1 as long as applied to the etchant until the recess 9 with the desired depth T in the metallization 3 is introduced, wherein the reduced layer thickness DR in the region of the recess 9 at least half of the original layer thickness D of the metallization 3 is. Finally, the thus processed metal-ceramic substrate 1 subjected to another surface cleaning.

In a fourth method step, the etched recesses 9 in the metallization 3 with the filler 6 filled and thereby formed a layer which the recesses 9 preferably completely filled. For applying the filling material 6 For example, a screen printing or blob printing process is suitable. Also, excess filler can be removed by means of a doctor blade. Possibly. the printing process is repeated several times to obtain a homogeneous filling of the recesses 9 to obtain. After curing of the filling material 6 can be a mechanical surface treatment of the metallization 3 and the filled recesses 9 be made. 9 shows the metal-ceramic substrate 1 after filling the recesses 9 and the curing of the filling material or the insulating layer 6 , In the present embodiment according to 9 forms that of the layer of filler 6 surrounded surface of the metallization 3 the central metallization area 3 '' the structured metallization 3 out.

According to a fifth process step is on the metallization 3 and the layer of the filler material 6 another Ätzresistschicht 10 applied, where the central metallization area 3 '' forming part of the metallization 3 made of copper or a copper alloy and the layer of the filler material 6 should remain. The further etching resist layer 10 is again generated by means of per se known techniques. 10 shows the metal-ceramic substrate 1 with the further etching resist layer 10 ,

Subsequently, in a sixth method step according to 11 not through the further etching resist layer 10 covered area of metallization 3 removed by etching, all the way to the ceramic layer 2 and thereby the etched portions of the ceramic layer 2 educated. In the present embodiment, therefore, only the one with the further etching resist layer remains 10 Covered connection area 5 ,

Finally, according to a seventh method step 12 the further etching resist layer 10 removed by an appropriate solvent and the remaining stepped formed metallization 3 with applied layer of the filler 6 forms the connection surface according to the invention 5 out. This creates in the outer edge area 3 ' the metallization 3 a step-like transition to the etched portion of the ceramic layer 2 ,

In an alternative embodiment of the method according to the invention according to the 13 to 15 In a second method step, the process with the etching resist layer 8th provided metallization 3 subjected to an etchant and a channel or web-like recess 11 from the metallization 3 etched, which preferably over the complete layer thickness of the metallization 3 ie to the ceramic layer 2 extends. The channel or web-like recess 11 has, for example, a width of 0.3 mm to 2 mm.

Subsequently, the Ätzresistschicht 8th at least partially removed. Alternatively, this can also be completely removed and reapplied, so that according to 14 the opposite and through the channel or web-like recess 11 separated edge portions of the metallization 3 not covered on the edge. In a further process step, the uncovered part of the metallization 3 subjected to an etchant, in such a way that only a part of the metallization 3 is removed and a stepped edge of the metallization 3 arises.

In the next process step, both the step-like edge of the metallization 3 as well as the channel or web-like recess 11 between the etched portions of the metallization 3 filled with the filling material and thereby one over the channel or web-like recess 11 and the insulation layer 6 educated.

Finally, in turn, the Ätzresistschicht 10 removed by an appropriate solvent and the remaining stepped metallization formed 3 with applied insulation layer 6 now forms several connection surfaces 5 . 5a . 5b out.

The generation of the trough-like recess 3b takes place analogously to the described method steps by appropriate masking and subsequent controlled etching.

Alternatively, the step-like edge portion 3a or the trough-like recess 3b also be produced by a mechanical surface processing method, such as milling.

In a further alternative embodiment of the method according to the invention according to the 16 to 18 In a second method step, the process with the etching resist layer 8th provided metallization 3 subjected to an etchant and a channel or web-like recess 11 from the metallization 3 etched, which preferably over the complete layer thickness of the metallization 3 ie to the ceramic layer 2 extends. Subsequently, to produce a stepped edge portion 3a the etch resist layer 8th at least in the at the channel or web-like recess 11 removed adjacent edge areas and applied again with an etchant. Alternatively, this can also be completely removed and a new further Ätzresistschicht 10 be applied, so that in 16 dashed lines indicated areas edge portions of the metallization 3 can be etched away. For this purpose, in a further process step, the uncovered part of the metallization 3 subjected to an etchant, in such a way that only a part of the metallization 3 is removed and a step-shaped edge portion 3a the metallization 3 arises and in a preferred embodiment, the subsequent edge portion of the ceramic layer 2 completely from the metallization 3 is free.

In the next process step, both the step-like edge portion 3a the metallization 3 as well as a part of the immediately adjacent surface of the ceramic layer 2 filled with the filling material and thereby one over the edge portion 3a on the surface of the ceramic layer extending insulating layer 6 educated. Finally, in turn, the Ätzresistschicht 10 removed by an appropriate solvent and the remaining stepped metallization formed 3 with applied insulation layer 6 now forms at least one connection surface 5 out.

In an advantageous embodiment, the metallizations 3 . 4 at least partially provided with a metallic surface layer, for example a surface layer of nickel, gold, silver or a nickel, gold and silver alloys. The layer thickness of the surface layer is for example between 0.1 micrometer and 10 micrometers. Such a metallic surface layer is preferably after the application of the metallizations 3 . 4 on the ceramic layer 2 applied. The application of the surface layer takes place in a suitable method, for example galvanically and / or by chemical deposition and / or by spraying.

In an embodiment not shown in the figures can between the pad 5 and the filler 6 one the connection surface 5 At least partially surrounding Lötstopstruktur is provided, which is for example also made of the filler. This is on the surface of the metallization 3 applied, for example by means of a screen printing process. Alternatively, the solder-stop structure may be formed by a glass-containing paste which is baked into the metallization and, in the baked state, a metallization formed from copper or a copper alloy 3 has a small coefficient of expansion.

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

Metal-ceramic substrate

2

ceramic layer

2 '

etched areas

2.1

first surface side

2.2

second surface side

3

structured metallization

3 '

outer edge area

3 ''

central metallization area

3a

Metallization section or step-like edge section

3b

Metallization section or trough-like recess

3b '

recess edge

4

further metallization

5

terminal area

6

filling material

7

Semiconductor device

8th

etching resist

9

recesses

10

further etching resist layer

11

channel or web-like recess

S

Transition area

D

layer thickness

DR

reduced layer thickness

B

Width of the step-like edge section

B '

Width of the recess

T

Depth of the recess

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]
• DE 2319854 [0003]
• DE 2213115 [0004]
• EP 153618 A [0004]
• DE 4004844 C1 [0008]

Claims (21)

Metal-ceramic substrate comprising at least one ceramic layer ( 2 ), which on at least one surface side ( 2.1 ) with at least one metallization ( 3 ) is provided with a layer thickness (D) of at least 0.1 mm, which is used for the formation of printed conductors and / or contact or terminal surfaces ( 5 . 5a . 5b ) is structured such that in the outer edge region ( 3 ' ) of the structured metallization ( 3 ) at least partially along the outer edge region ( 3 ' ) extending metallization section ( 3a . 3b ) with reduced layer thickness (DR), characterized in that the layer thickness-reduced metallization section (FIG. 3a . 3b ) with a layer of a filling material ( 6 ) is provided. Metal-ceramic substrate according to claim 1, characterized in that the layer thickness-reduced metallization section is formed by a stepped outer edge section (FIG. 3a ) of the metallization ( 3 ) and / or formed by a plurality of recesses. Metal-ceramic substrate according to claim 2, characterized in that the layer of the filling material ( 6 ) over the outer edge portion ( 3a ) in the subsequent etched area ( 2 ' ) of the ceramic layer ( 2 ). Metal-ceramic substrate according to claim 1, characterized in that the layer thickness-reduced metallization section by a preferably having a trough-like cross-section recess ( 3b ) in the outer edge region ( 3 ' ) of the metallization ( 3 ) is formed. Metal-ceramic substrate according to claim 4, characterized in that the preferably trough-like recess ( 3b ) with the filling material ( 6 ) is completely filled. Metal-ceramic substrate according to one of claims 1 to 5, characterized in that the layer thickness-reduced metallization section ( 3a . 3b ) by appropriate masking and etching of the metallization ( 3 ) and / or generated by a mechanical surface treatment, in particular milling. Metal-ceramic substrate according to one of claims 1 to 3, characterized in that the layer of the filler material ( 6 ) is approximately flush with the top of the structured metallization ( 3 ) is trained. Metal-ceramic substrate according to one of claims 1 to 7, characterized in that the outer edge region ( 3 ' ) a central metallization region ( 3 '' ), which has a contact or bonding surface for connecting an electrical component ( 7 ). Metal-ceramic substrate according to one of claims 1 to 8, characterized in that the filling material ( 6 ) is made of a plastic material having a ceramic portion and / or graphitized carbon content. Metal-ceramic substrate according to claim 9, characterized in that as a plastic material polyimide, polyamides, epoxies or polyetheretherketone and as a ceramic component silicon nitride, aluminum nitride, alumina or glass is provided. Metal-ceramic substrate according to one of claims 1 to 10, characterized in that the thermal expansion coefficient of the filling material ( 6 ) smaller than the thermal expansion coefficient of the metallization ( 3 ). Metal-ceramic substrate according to one of claims 1 to 11, characterized in that the ceramic layer ( 2 ) is made of oxide, nitride or carbide ceramics such as aluminum oxide or aluminum nitride or silicon nitride or silicon carbide or aluminum oxide with zirconium oxide. Metal-ceramic substrate according to one of claims 1 to 10, characterized in that the further surface side ( 2.2 ) of the ceramic layer ( 2 ) with at least one further metallization ( 4 ) is provided. Metal-ceramic substrate according to one of claims 1 to 13, characterized in that the metallizations ( 3 . 4 ) by means of a "direct copper bonding" method with the ceramic layer ( 2 ) are connected. Method for producing a metal-ceramic substrate ( 2 ) comprising at least one ceramic layer ( 2 ), which on at least one surface side ( 2.1 ) with at least one metallization ( 3 ) is provided with a layer thickness (D) of at least 0.1 mm, in which the formation of printed conductors and / or contact or pad surfaces ( 5 . 5a . 5b ) the metallization ( 3 ) is structured such that in the outer edge region ( 3 ' ) of the structured metallization ( 3 ) at least partially along the outer edge region ( 3 ' ) extending metallization section ( 3a . 3b ) is produced with reduced layer thickness (DR), characterized in that the layer thickness reduced metallization section (DR) 3a . 3b ) with a filling material ( 6 ) is coated. Method according to claim 15, characterized in that the metallization ( 3 ) an etching resist layer ( 8th ) is applied, namely where the metallization ( 3 ) should remain with the existing layer thickness (D). A method according to claim 16, characterized in that the with the Ätzresistschicht ( 8th ) provided metallization ( 3 ) for producing the layer thickness-reduced metallization section ( 3a . 3b ) is applied to an etching solution until recesses ( 9 ) of a predetermined depth (T) in the etch resist layer (FIG. 8th ) released areas of the metallization ( 3 ) are etched free. A method according to claim 17, characterized in that the Ätzresistschicht ( 8th ) of the metallization ( 3 ) is removed again. Method according to claim 17 or 18, characterized in that the etched recesses ( 9 ) with the filling material ( 6 ) are filled. A method according to claim 19, characterized in that at least partially on the metallization ( 3 ) and on the layer of the filling material ( 6 ) a further etching resist layer ( 10 ) is applied, where the metallization ( 3 ) for forming one or more connection surfaces ( 5 . 5a . 5b ) remain. A method according to claim 20, characterized in that that of the further Ätzresistschicht ( 10 ) released areas of the metallization ( 3 ) are exposed to an etching solution and completely up to the ceramic layer ( 2 ) are removed.

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