METHOD FOR MANUFACTURING METAL CERAMIC SUBSTRATE, SOLDER SYSTEM, AND METAL CERAMIC SUBSTRATE MANUFACTURED BY THE METHOD

Abstract

To provide a method for producing a metal-ceramic substrate, a solder system, and a metal-ceramic substrate produced using the method.SOLUTION: A method for producing a metal-ceramic substrate 1 includes the steps of: providing a ceramic layer 10, a metal layer 20 and a solder layer 30; coating the ceramic layer 10 and / or the metal layer 20 and / or the solder layer 30 with an active metal layer 40; arranging the solder layer 30 between the ceramic layer 10 and the metal layer 20 along a stacking direction S to form a solder system 35; and bonding the metal layer 20 to the ceramic layer 10 via the solder system 35. A first thickness D1 of the active metal layer 40 is between 150 nm and 750 nm, and a ratio of the first thickness D1 of the active metal layer 40 to a second thickness D2 of the solder layer 30 is between 0.003 and 0.5.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for manufacturing a metal-ceramic substrate, a soldering system for that method, and a metal-ceramic substrate realized by that method. [Background technology]

[0002] Metal-ceramic substrates are known in the prior art, for example as printed circuit boards or circuit boards, from, for example, US Pat. No. 5,529,499, US Pat. No. 5,529,499, and US Pat. No. 5,529,499. Connection areas for electrical components and conductor tracks are usually arranged on the component side of the metal-ceramic substrate, allowing the electrical components and conductor tracks to be interconnected to form an electrical circuit. Essential components of a metal-ceramic substrate are an insulating layer, preferably made of ceramic, and one or more metal layers bonded to the insulating layer. Due to their relatively high dielectric strength, ceramic insulating layers have proven particularly effective in power electronics. Conductive tracks and / or connection areas for electrical components can be realized by structuring the metal layer.

[0003] To provide such metal-ceramic substrates, a permanent bond between the metal layer and the ceramic layer is required. In addition to the so-called direct bonding processes, i.e. DCB or DAB processes, it is known from the prior art to bond the metal layer to the ceramic layer by means of a solder material.

[0004] The active solder process for joining a metal layer or foil, in particular a copper layer or foil, to a ceramic material is understood to be a process particularly used for producing metal-ceramic substrates, in which a brazing alloy containing an active metal in addition to the main components, such as copper, silver, and / or gold, is used to bond a metal foil, such as a copper foil, to a ceramic substrate, such as an aluminum nitride ceramic, at temperatures between about 650°C and 1000°C. The active metal, e.g., one or more of Hf, Ti, Zr, Nb, and Ce, establishes a bond between the brazing alloy and the ceramic by chemical reaction, while the bond between the brazing alloy and the metal is a braze bond.

[0005] For example, Patent Documents 4 and 5 disclose methods for manufacturing power module substrates using active solder materials. In particular, they disclose that the bonding of copper foil to a ceramic layer is performed by a multi-layer solder system. This multi-layer system is composed of a layer of titanium foil and a layer of a phosphorus-containing solder filler material. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] German Patent Application Publication No. 102013104739 [Patent Document 2] German Patent Invention No. 19927046 [Patent Document 3] German Patent Application Publication No. 102009033029 [Patent Document 4] European Patent Application Publication No. 3041042 [Patent Document 5] International Publication No. 2017 / 126653 Summary of the Invention [Problem to be solved by the invention]

[0007] In view of this prior art, the object of the present invention is to achieve the joining of a metal layer to a ceramic layer by using a solder system that is improved compared to the prior art, in particular with regard to the solder layer, the joining of the metal layer to the ceramic layer, and the joining process during active soldering. [Means for solving the problem]

[0008] The object is achieved by a method for producing a metal-ceramic substrate according to claims 1 and 5, a soldering system for said method according to claim 13, and a metal-ceramic substrate produced by said method according to claim 14. Further advantages and properties of the invention are given by the dependent claims together with the description and the accompanying drawings.

[0009] According to a first aspect of the present invention, there is provided a method of manufacturing a metal ceramic substrate, the method comprising: providing one or more ceramic layers, one or more metal layers, and one or more solder layers, particularly in the form of one or more solder foils; coating one or more ceramic layers and / or one or more metal layers and / or one or more solder layers with one or more active metal layers; disposing one or more solder layers between one or more ceramic layers and one or more metal layers along a stacking direction to form a solder system comprising one or more solder layers and one or more active metal layers; and joining the one or more metal layers to the one or more ceramic layers via a solder system by an active solder process.

[0010] Compared to known processes for producing metal-ceramic substrates, the present invention provides a multilayer solder system comprising one or more solder layers, preferably free of elements that lower the melting point, and one or more active metal layers. The separation of the one or more active metal layers from the one or more solder layers has been found to be particularly advantageous, since it allows for a relatively thin solder layer, especially when the solder layer is a foil. Otherwise, a relatively large solder layer thickness would be required for solder materials containing active metals due to brittle intermetallic phases that hinder the transformation of the solder paste and thus the solder layer, and the minimum layer thickness is therefore limited by the manufacturing characteristics of the solder material containing active metals. Therefore, for solder layers containing active metals, the minimum solder layer thickness is determined not by the minimum thickness required for the joining process, but by the minimum technically feasible solder layer thickness. As a result, thicker solder layers containing active metals are more expensive than thinner layers.

[0011] By separating the active metal from one or more solder layers, the thickness of the one or more solder layers can be advantageously reduced. As a result, it is possible to save material in the solder system or one or more solder layers. Such active metal-free solder layers are also particularly advantageous in that they can be rolled to a thickness of less than 10 μm, preferably less than 7 μm. A further advantage is that etching of patterns on the manufactured metal-ceramic substrate is simplified, especially because the second thickness of the solder system or one or more solder layers is reduced. Furthermore, bonding of the metal layer to the ceramic layer can be facilitated in manufacturing operations.

[0012] In particular, the use of a separate active metal layer is also possible if the solder layer does not contain elements that lower the melting point and / or does not contain phosphorus. This allows for more flexibility in the selection of the material for the solder layer(s) used in each case and also allows for the use of established processing parameters for active solder processing. Furthermore, it is advantageously possible to avoid adding corresponding melting point-lowering elements before forming one or more solder layers. In particular, those skilled in the art will understand one or more solder layers that do not contain melting point-lowering elements to be layers that contain less than 3 wt. %, preferably less than 2 wt. %, and more preferably less than 1 wt. % of these melting point-lowering elements. Examples of these melting point-lowering elements include phosphorus and zinc. The use of a phosphorus-free soldering material advantageously allows for the separation of the active metal layer from the solder layer, for example, even for solder layers that do not contain phosphorus and therefore contain melting point-lowering materials whose integration into the solder layer does not lead to the significant melting point reduction known for phosphorus. For example, it is a material that reduces the melting point of the solder layer by less than 100°C, preferably less than 80°C, and more preferably less than 50°C.

[0013] Furthermore, it is preferred that the one or more solder layers are free of active metals. In particular, those skilled in the art will understand that free of active metals means that the solder layer contains less than 5% by weight, preferably less than 3% by weight, and more preferably less than 1.5% by weight of active metals. Examples of active metals include titanium (Ti), zirconium (Zr), hafnium (Hf), chromium (Cr), niobium (Nb), cerium (Ce), and vanadium (V). It is particularly preferred that the one or more solder layers are provided as foils. This allows for the easiest possible handling of the foil when placing it between one or more ceramic layers and one or more metal layers, especially in the serial production of metal-ceramic substrates.

[0014] For example, it is conceivable that one or more solder layers are pre-applied on or together with the metal layer. For example, one or more solder layers are applied on one side of one or more metal layers used to manufacture the metal-ceramic substrate. In this case, the one or more metal layers serve as a support for the one or more solder layers. However, it is also conceivable that one or more solder layers are applied to a film, such as a plastic film forming a support. Furthermore, it is conceivable that one or more solder layers are applied to one or more metal layers, and that one or more additional metal layers, preferably with a different particle size distribution or different average particle size, are provided on the side opposite the one or more metal layers carrying the one or more solder layers. In particular, the particle sizes, especially their average particle sizes, of the one or more metal layers and the one or more additional metal layers are different from each other, so that two metallized layers are formed on the top of the ceramic during the joining process. It is particularly preferred that the metal layer with the smaller average particle size is located on the outside, and the metal layer with the larger average particle size faces the solder system or ceramic layer.

[0015] In particular, it is advantageous that one or more active metal layers can be selectively disposed on one or more ceramic layers and / or one or more metal layers and / or one or more solder layers. It is preferable that one or more active metal layers are disposed on two or more of the layers. Preferably, one or more active metal layers are disposed on the surfaces of one or more ceramic layers and / or one or more metal layers that face one or more solders in the arrangement or metal-ceramic substrate. It is particularly preferable that one or more active metal layers are disposed on one or more solder layers. In this case, a solder system can be provided that includes one or more solder layers with one or more active metal layers, and the solder system can be easily disposed between one or more ceramic layers and one or more metal layers for an active soldering process. In this case, the joining process is an active soldering process performed at a processing temperature of between 600°C and 1000°C, preferably between 700°C and 950°C.

[0016] Preferably, the solder material of one or more solder layers is a silver-based or copper-based solder material. In silver-based solder materials, silver is the major component, i.e., the component that accounts for the largest proportion by weight, while in copper-based solder materials, copper is the major component. Examples of silver-based solder materials include AgCu, particularly AgCu28, AgCuIn, AgCuSn, and AgCuGa. Examples of copper-based solder materials include CuCuSn, CuIn, CuGa, CuInSn, CuInMn, and CuGaSn. NiCrMn can also be used as a solder material. In particular, it is preferred that the solder layer is silver-free, i.e., that the solder layer contains less than 3 wt. % silver, preferably less than 2 wt. % silver, and more preferably less than 1 wt. This advantageously saves silver, since the silver content of the resulting metal-ceramic substrate can lead to migration of silver ions within the solder system.

[0017] Preferably, the solder layer or the solder material of the solder layer contains multiple components and / or does not contain silver. In other words, the solder material is not composed of a single chemical element. In particular, the solder layer does not contain only silver. Preferably, the solder layer contains two or more different components or elements. This advantageously allows further optimization of the bonding behavior, for example, with respect to adhesive strength and thermal shock resistance. For example, it is not necessary to use a pure silver layer, whose silver ion migration and etching behavior would adversely affect the manufactured metal-ceramic substrate. Other examples of materials for forming the solder layer as a brazing material include CuNi and CuNiMn, especially for solder application temperatures up to 1050°C. Furthermore, pure silver is also conceivable.

[0018] Possible materials for the one or more metal layers include copper, aluminum, molybdenum, and / or their alloys and laminates, as well as powder metallurgy composites such as CuW, CuMo, CuAl, AlCu, and / or CuCu, particularly copper sandwich structures having a first copper layer and a second copper layer, where the grain size of the first copper layer is different from that of the second copper layer. Furthermore, it is preferred that one or more metal layers are surface-modified. Possible surface modifications include, for example, sealing with noble metals, especially silver and / or gold, or ENIG (electroless nickel-displacement gold plating), or edge encapsulation of the first or second metal layer to prevent crack formation or expansion.

[0019] Preferably, one or more ceramic layers comprise Al2O3, Si3N4, AlN, HPSX ceramic (i.e., ceramic with an Al2O3 matrix containing x percent of ZrO2, e.g., Al2O3 with 9% ZrO2=HPS9 or Al2O3 with 25% ZrO2=HPS25), SiC, BeO, MgO, high-density MgO (greater than 90% of theoretical density), TSZ (tetragonal stabilized zirconium oxide), or ZTA as ceramic materials. Here, the insulating layer may be designed as a composite or hybrid ceramic, in which multiple ceramic layers with different material compositions are arranged one on top of the other and bonded to form the insulating layer, in order to combine various desired properties. To achieve the lowest possible thermal resistance, it is preferable to use a high-thermal-conductivity ceramic.

[0020] According to a preferred embodiment, the one or more active metal layers are deposited by a vapor deposition process, in particular by PVD (physical vapor deposition) or by CVD (chemical vapor deposition). This manufacturing process makes it possible to provide relatively thin active metal layers that are deposited as uniformly as possible. In particular, the deposition can be controlled as much as possible, so that the deposited one or more active metal layers have a thickness that is as constant as possible over the deposition area. For example, for the vapor deposition process, thermal evaporation, electron beam evaporation, laser beam evaporation, arc evaporation or molecular beam epitaxy, sputtering such as ion beam assisted deposition, ion plating, and / or ICB techniques can be used.

[0021] Advantageously, the first thickness of the one or more active metal layers is between 100 nm and 1000 nm, preferably between 150 nm and 750 nm, and more preferably between 200 nm and 500 nm. Such a thin active metal layer advantageously prevents a decrease in the thermal conductivity and mechanical strength of the metal-ceramic substrate, especially at the interface between the one or more ceramic layers and the one or more metal layers. It is more preferable for the layer thickness to match the intended holding time. For example, for long holding times, e.g., more than 10 days, it is advantageous to use a layer thickness between 750 and 1000 nm, especially in the case of titanium as the active metal layer. For short holding times, a first thickness of 150 nm to 350 nm may be used.

[0022] Active soldering is performed at 10 -2 less than 1 mbar (1 Pa), preferably less than 10 -3 mbar(10 -1 Pa), more preferably less than 10 -4 mbar(10 -2 It is preferable to carry out the process at pressures below 1000 kPa (1000 kPa) and / or using process gases. For example, active soldering is carried out in a high vacuum or a microvacuum with very low oxygen and argon partial pressures below 1 mbar (100 Pa). Alternatively, it is conceivable to work at atmospheric pressure under argon or, in general, noble gases. Since no organic binders are used here, it is possible to reduce the process time by up to half.

[0023] Furthermore, the second thickness of the one or more solder layers preferably has a value between 1 μm and 100 μm, preferably between 1.5 μm and 50 μm, more preferably between 2 μm and 20 μm or less than 10 μm. This is particularly the second thickness before the joining process, i.e., the active soldering process. It is particularly preferred that the one or more solder layers be further reduced, for example by rolling, to a thickness of less than 10 μm, preferably less than 7 μm, and more preferably less than 5 μm, before the joining process. In this way, the layer thickness of the solder material or one or more solder layers can be advantageously further reduced. Furthermore, it is preferred that the one or more solder layers be reduced in thickness by rolling before being disposed between the one or more ceramic layers and the one or more metal layers. In this way, it is possible to achieve a thinner one or more solder layers before being reduced to the final layer thickness intended for the joining process in a further solder layer process, for example by rolling.

[0024] The ratio of the first thickness of the active metal layer to the second thickness of the solder layer is between 0.003 and 0.5, preferably between 0.015 and 0.2, and more preferably between 0.03 and 0.14, i.e., the second thickness of the solder layer is significantly greater than the first thickness of the active metal layer.

[0025] Furthermore, the active metal layer(s) are preferably covered by one or more protective layers, which advantageously prevent oxidation of the active metal layer(s). For example, copper (Cu), nickel (Ni), indium (In), silver (Ag), chromium (Cr), or titanium nitride (TiN) can be used as the protective layer for the active metal layer(s). In this case, the thickness of the protective layer(s) is at least 100 nm. It is particularly preferred that the thickness of the protective layer(s), i.e., the third thickness, is adapted to the holding time, i.e., the time elapsed between the placement of the active metal layer(s) and the actual joining process in the active soldering process. In this way, the permanent retention of the components (one or more metal layers and / or one or more active metal layers and / or one or more solder layers) covered with the active metal layer(s) can be advantageously ensured without oxidation of the active metal layer(s) prior to the joining process. For example, the layer thickness of the one or more protective layers, i.e. the third thickness, is between 100 nm or 50 nm and 1000 nm, preferably between 150 nm and 750 nm, more preferably between 250 nm and 500 nm.

[0026] Furthermore, it is preferred that the ratio of the third thickness of the one or more protective layers to the first thickness of the one or more active metal layers, measured in the stacking direction, has a value between 0.5 and 1, preferably between 0.7 and 0.9, and more preferably between 0.75 and 0.85.

[0027] Furthermore, the one or more active metal layers preferably have a composition that varies along the stacking direction. In this way, premature oxidation of the active metal layer is also advantageously prevented by increasing the amount of intervening elements, such as nitrogen, oxygen, or carbon, particularly as the distance from the surface (one or more metal layers, one or more ceramic layers, or one or more solder layers) on which the active metal is applied increases. Furthermore, to extend the holding time of a component with one or more active metal layers, i.e., one or more metal layers, one or more ceramic layers, and / or one or more solder layers, the one or more active metal layers are covered with one or more additional solder layers. In this case, the thickness of the one or more additional solder layers is at least 0.1 times, preferably 0.05 times, and more preferably 0.01 times, thinner than the second thickness of the one or more solder layers. Advantageously, the solder system forms a sandwich structure in which the one or more active metal layers are enveloped or surrounded by one or more solder layers and one or more additional solder layers.

[0028] Preferably, the one or more solder layers and / or one or more active metal layers are rolled so that the first thickness of the active metal layer after rolling and / or pressing is less than 1000 nm, preferably less than 750 nm, and more preferably less than 500 nm. In this way, compared to alternative methods using electroplating or vapor deposition, it is advantageously possible to achieve a first thickness of the active metal layer, particularly less than 1000 nm, when the solder layer and the active metal layer are rolled together. In this process, the layer thicknesses of the active metal layer and the solder layer, i.e., the first and second thicknesses, are rolled and / or pressed together. For this purpose, the solder layer and the active metal layer, for example, in the form of a thick solder foil, are initially joined, for example, by an upstream or initial rolling process to reduce the layer thickness. Here, the initial layer thickness of the active metal layer and the initial layer thickness of the solder foil are preferably in the same proportion to each other as the first and second thicknesses in the manufactured solder system having an active metal layer of the first thickness and a solder layer of the second thickness. In subsequent rolling passes, particularly multiple passes, the active metal layer and solder layer are rolled to their respective thicknesses, with each pass depositing a thinner active metal layer on a relatively thin solder layer, and this solder system can then be used to bond the metal layer to the ceramic layer in an active solder process.

[0029] It is particularly preferred that a further active metal layer is provided and the solder layer is disposed between the active metal layer and the further active metal layer, so that the interface between the solder layer and one or more metal layers can also be affected by the active metal of the active metal layer.

[0030] Furthermore, it is preferred that the ceramic layer is coated with an active metal layer, and that one or more metal layers are coated with a solder layer. It is particularly preferred if the metal layer or layers have a layer thickness of more than 1 mm, preferably more than 1.3 mm, particularly preferably more than 1.5 mm, which provides a relatively thick metal layer or layers, which supports rapid dissipation of thermal energy and allows heat diffusion on the component side.

[0031] A further aspect of the invention is a solder system of the method according to the invention, which comprises one or more solder layers, in particular in the form of a solder foil, and one or more active metal layers. All advantages and specifications described for the method for manufacturing a metal-ceramic substrate apply equally to the solder system.

[0032] Another aspect is a metal ceramic substrate produced by a method comprising: providing one or more ceramic layers, one or more metal layers, and one or more solder layers, particularly in the form of one or more solder foils; coating one or more ceramic layers and / or one or more metal layers and / or one or more solder layers with one or more active metal layers; disposing one or more solder layers between one or more ceramic layers and one or more metal layers along a stacking direction to form a solder system comprising one or more solder layers and one or more active metal layers, wherein the solder material of the one or more solder layers preferably does not contain a material that reduces the melting point; and joining one or more metal layers to one or more ceramic layers via a solder system by an active soldering process. All advantages and features described for the method for manufacturing a metal-ceramic substrate apply equally to the metal-ceramic substrate.

[0033] Further advantages and features will become apparent from the following description of preferred embodiments of the subject matter of the present invention, with reference to the accompanying drawings, in which: The individual features of the individual embodiments can therefore be combined within the scope of the present invention. [Brief explanation of the drawings]

[0034] [Figure 1] 1 is a schematic diagram of a method for manufacturing a metal-ceramic substrate according to a first preferred embodiment of the present invention; [Figure 2] FIG. 2 is a schematic diagram of a method for manufacturing a metal-ceramic substrate according to a second preferred embodiment of the present invention. [Figure 3]FIG. 4 is a schematic diagram of a method for manufacturing a metal-ceramic substrate according to a third preferred embodiment of the present invention. [Figure 4] FIG. 4 is a schematic diagram of a method for manufacturing a metal-ceramic substrate according to a fourth preferred embodiment of the present invention. [Figure 5] FIG. 5 is a schematic diagram of a method for manufacturing a metal-ceramic substrate according to a fifth preferred embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0035] FIG. 1 shows an outline of a method for manufacturing a metal-ceramic substrate 1 according to a first preferred embodiment of the present invention. Such a metal-ceramic substrate 1 is preferably used as a support for electronic or electrical components that can be connected to the metal-ceramic substrate 1. An example of a manufactured metal-ceramic substrate 1 is shown schematically in the upper left of FIG. 1. The essential components of such a metal-ceramic substrate 1 include one or more ceramic layers 10 extending along a main extension plane HSE and one or more metal layers 20 bonded to the one or more ceramic layers 10. The one or more ceramic layers 10 are formed of one or more materials, including ceramic. Here, the one or more metal layers 20 and the one or more ceramic layers 10 are arranged one above the other along a stacking direction S that extends perpendicular to the main extension plane HSE and are bonded to each other in the manufactured state, at least in certain areas, through a material bond by a solder system 35. The one or more metal layers 20 of the manufactured metal-ceramic substrate 1 are then preferably structured to form conductor tracks or connection areas of electrical components. For example, this patterning is etched into the one or more metal layers 20. However, a permanent bond, in particular a material bond, must be established beforehand between the one or more metal layers 20 and the one or more ceramic layers 10 .

[0036] In the exemplary embodiment of FIG. 1 , this permanent, particularly materially bonded, connection is achieved by an active solder process. For this purpose, a solder system 35 is disposed between one or more ceramic layers 10 and one or more metal layers 20. The solder system 35 enables a material bond between the ceramic layer 10 and the metal layer 20 to be achieved in the completed metal-ceramic substrate 1. In particular, the solder system 35 has multiple layers. In addition to one or more solder layers 30, the solder system 35 also includes one or more active metal layers 40. In particular, the one or more solder layers 30 do not contain an active metal, i.e., they are free of an active metal. Instead, the active metal is disposed in a separate layer as the active metal layer 40 in the solder system 35. This separation in the solder system 35, in which an active metal-free soldering material is provided on one solder layer 30 and an active metal-encased active metal layer 40 is provided on the other, advantageously allows for the implementation of solder layers 30 that are as thin as possible. Otherwise, it may be necessary to have a larger minimum layer thickness for one or more solder layers 30, particularly in the form of a solder foil, that is limited not by the minimum thickness required for the joining process, but by the manufacturing operations of the one or more solder layers 30.

[0037] By separating the one or more active metal layers 40 from the one or more solder layers 30, correspondingly thinner solder foils can be produced, since in this case brittle intermetallic phases do not interfere with the transformation. In particular, this advantageously makes it possible to provide solder layers 30, in particular in the form of solder foils, that achieve rollability of the one or more solder layers 30 to thicknesses of less than 10 μm, preferably less than 8 μm, and more preferably less than 6 μm. In the illustrated exemplary embodiment, the one or more active metal layers 40 are arranged on the one or more ceramic layers 10, for example by sputtering or CVD, and have a first thickness D1 having a value between 100 nm and 1000 nm, preferably between 150 nm and 750 nm, and more preferably between 200 nm and 500 nm.

[0038] This thin active metal layer 40 can prevent the degradation of thermal conductivity and mechanical strength that would otherwise be expected when using a thicker active metal layer 40. This characteristic is particularly true for the layer thickness, i.e., the first thickness D1, between 200 nm and 500 nm. Here, before the active soldering process is performed, one or more solder layers 30, in particular one or more solder foils, are arranged as separate layers between the one or more active metal layers 40 and the one or more metal layers 20. For example, to achieve the thinnest possible solder layer 30, one or more solder foils can be arranged on the one or more active metal layers 40 and plated to a second thickness of less than 10 μm, preferably less than 7 μm, by a rolling process. The use of a relatively thin one or more solder layers 30 accelerates the joining process on the one hand and advantageously reduces material consumption when performing the joining between the one or more ceramic layers 10 and the one or more metal layers 20 on the other hand. In this case, the one or more ceramic layers 10 and the one or more metal layers 20 are arranged one above the other along the stacking direction S. A solder system 35 having one or more solder layers 30 and one or more active metal layers 40 is disposed between one or more metal layers 20 and one or more ceramic layers 10 along the stacking direction S. In particular, the one or more solder layers 30 are not only free of active metals, but also free of elements that lower the melting point, such as phosphorus or zinc. Those skilled in the art will understand that "substantially free of low-melting-point elements" means, in particular, that the amount of such elements in the solder layer is less than 3 wt %, preferably less than 2 wt %, and more preferably less than 1 wt %. For example, the one or more solder layers 30 are preferably free of solder materials containing phosphorus or zinc to prevent a decrease in melting temperature. Surprisingly, for such solder materials free of elements that lower the melting point, bonding via one or more separate active element layers 40 is also possible. This allows the use of relatively thin one or more solder layers 30 for such solder materials used at typical processing temperatures for active soldering. Therefore, typical process parameters commonly used in active soldering can be used, and relatively thin one or more solder layers 30 can be achieved.

[0039] FIG. 2 illustrates a schematic diagram of a method for manufacturing a metal-ceramic substrate 1 according to a second exemplary embodiment of the present invention. The exemplary embodiment of FIG. 2 differs substantially from the exemplary embodiment of FIG. 1 only in that, in addition to the one or more active metal layers 40, one or more protective layers 41 are disposed. Specifically, the one or more protective layers 41 extending along the main extension surface HSE cover the active metal layers 40. The use of such one or more protective layers 41 advantageously prevents oxidation on or outside the one or more active metal layers 40 before the actual joining process, i.e., the active soldering process, is performed. Preferably, such one or more protective layers 41 have a third thickness D3 with a minimum thickness of at least 100 nm. Preferably, the third thickness D3 of the one or more protective layers is between 100 nm and 1000 nm, preferably between 150 nm and 750 nm, and more preferably between 200 nm and 500 nm. Furthermore, the one or more protective layers 41 preferably partially or completely cover the one or more active metal layers 40 and are preferably arranged between the one or more active metal layers 40 and the one or more solder layers 30 when viewed in the stacking direction S. Preferably, the third thickness D3 is adapted to the expected period from the deposition of the active metal layers (40) and the protective layer (41) until bonding by the active soldering process occurs. In this way, the intended holding time can be advantageously adjusted, particularly by the third thickness D3 of the protective layer 41, so that the one or more active metal layers 40 do not oxidize before bonding. Preferably, the third thickness D3 of the one or more protective layers 41 approximately corresponds to the first thickness D1 of the active metal layer 40.

[0040] Furthermore, the one or more solder layers 30 have a second thickness D2 having a value between 0.1 and 100 μm, preferably between 0.5 and 50 μm, and more preferably between 0.2 and 20 μm. This is particularly true of the second thickness D2 before applying the one or more solder layers 30 or before disposing on the one or more metal layers 20 or one or more active metal layers 40. In particular, after applying or disposing on the one or more metal layers 20, the second thickness D2 of the one or more solder layers 30 is further reduced by further rolling. After disposing on the one or more metal layers 20, the one or more ceramic layers 10, and the solder system 35 disposed between the one or more metal layers 20 and the one or more ceramic layers 10, the joining is carried out at a temperature between 700°C and 900°C. The soldering process is carried out at a pressure of 10 mbar (10 3 Preferably, the joining process, i.e. the active soldering process, is carried out at a pressure of less than 1000 kJ / cm² (Pa). It is also conceivable that the joining process, i.e. the active soldering process, is carried out using a process gas or in a working atmosphere which contains, for example, argon or more generally one or more noble gases.

[0041] 3 shows a schematic diagram of a method for manufacturing a metal-ceramic substrate 1 according to a third exemplary embodiment of the present invention. Essentially, this embodiment differs from the embodiment of FIG. 2 in that one or more active metal layers 40 are attached to one or more solder layers 30 before being disposed between one or more metal layers 20 and one or more ceramic layers 10. In other words, here, the bonding of one or more active metal layers 40 to one or more solder layers 30 is performed by sputtering prior to the disposition between one or more ceramic layers 10 and one or more metal layers 20. In particular, here, one or more protective layers 41 partially or preferably completely cover one or more active metal layers 40, particularly on one side, to prevent initial oxidation of the one or more active metal layers 40.

[0042] FIG. 4 shows a schematic diagram of a method for manufacturing a metal-ceramic substrate 1 according to a fourth exemplary embodiment of the present invention. In contrast to the embodiments of FIGS. 2 and 3, in the exemplary embodiment of FIG. 4, one or more active metal layers 40 are bonded to one or more metal layers 20 before the active soldering process. In this case, the one or more active metal layers 40 are arranged, in particular, on the side of the one or more metal layers 20 that faces the solder layer 30 in the bonding process. For example, the one or more active metal layers 40 may be arranged over the entire area of ​​the one or more metal layers 20 by a CVD process or sputtering, i.e., generally by a vapor deposition process. After arranging the one or more metal layers 20, to which the one or more active metal layers 40 are attached, the one or more ceramic layers 10, and the one or more solder layers 30, the bonding process is carried out by the active soldering process.

[0043] Figure 5 shows a schematic of a method for manufacturing a metal-ceramic substrate 1 according to a fifth exemplary embodiment of the present invention. Herein, the exemplary embodiment of Figure 5 differs from the embodiment of Figure 2 only in that both the front and back sides of one or more ceramic layers 10 are respectively bonded to one or more metal layers 20 via corresponding solder systems 35. Preferably, the solder system 35 includes one or more solder layers 30, one or more active metal layers 40, and one or more protective layers 41. [Explanation of symbols]

[0044] 1 Metal ceramic substrate 10 ceramic layer 20 metal layer 30 solder layer 35 Soldering System 40 Active metal layer 41 Protective layer S Stacking direction HSE main extension surface D1 First thickness D2 Second thickness D3 Third thickness

Claims

1. A method for manufacturing a metal ceramic substrate (1), comprising the steps of: providing one or more ceramic layers (10), one or more metal layers (20), and one or more solder layers (30) in the form of one or more solder foils; coating one or more of said ceramic layers (10) and / or one or more of said metal layers (20) and / or one or more of said solder layers (30) with one or more active metal layers (40); forming a solder system (35) comprising one or more solder layers (30) and one or more active metal layers (40) by disposing one or more solder layers (30) between one or more ceramic layers (10) and one or more metal layers (20) along a stacking direction (S); and joining one or more of the metal layers (20) to one or more of the ceramic layers (10) via the solder system (35) by an active solder process; One or more of the metal layers (20) of the produced metal-ceramic substrate (1) are structured to form conductor tracks or connection areas of electrical components, the solder material of the one or more solder layers (30) is a silver-based or copper-based solder material; the solder material of the solder layer (30) is AgCuIn, AgCuGa, CuIn, CuGa, CuInSn, or CuGaSn; the first thickness (D1) of the one or more active metal layers (40) is between 150 nm and 750 nm; a ratio of the first thickness (D1) of the active metal layer (40) to the second thickness (D2) of the solder layer (30) is between 0.003 and 0.5; The method wherein one or more of said active metal layers (40) are deposited by a vapor deposition process.

2. The method of claim 1, wherein the solder material of the solder layer (30) is CuIn, CuGa, CuInSn, or CuGaSn.

3. 3. The method according to claim 1, wherein the first thickness (D1) of the one or more active metal layers (40) has a value between 200 nm and 500 nm.

4. The active soldering process is －２ carried out at a pressure of less than 1000 mbar (1 Pa) and / or using a process gas, 4. The method of any one of claims 1 to 3, wherein one or more of the active metal layers (40) are deposited by the vapor deposition process and by galvanic current.

5. A method for manufacturing a metal ceramic substrate (1), comprising the steps of: providing one or more ceramic layers (10), one or more metal layers (20), and one or more solder layers (30) in the form of one or more solder foils; coating one or more of the ceramic layers (10) and / or one or more of the metal layers (20) and / or one or more of the solder layers (30) with one or more active metal layers (40), the active metal layers being disposed between the solder layers and the ceramic layers; forming a solder system (35) comprising one or more solder layers (30) and one or more active metal layers (40) by disposing one or more solder layers (30) between one or more ceramic layers (10) and one or more metal layers (20) along a stacking direction (S); and joining one or more of the metal layers (20) to one or more of the ceramic layers (10) via the solder system (35) by an active solder process; the solder material of the one or more solder layers (30) is a silver-based or copper-based solder material; the solder material of the solder layer (30) is AgCuIn, AgCuGa, CuIn, CuGa, CuInSn, or CuGaSn; the first thickness (D1) of the one or more active metal layers (40) is between 150 nm and 750 nm; a ratio of the first thickness (D1) of the active metal layer (40) to the second thickness (D2) of the solder layer (30) is between 0.003 and 0.5; The method wherein one or more of said active metal layers (40) are deposited by a vapor deposition process.

6. 6. The method according to claim 1, wherein the ratio of the first thickness (D1) of the active metal layer (40) to the second thickness (D2) of the solder layer (30) has a value between 0.015 and 0.

2.

7. 7. The method according to any one of claims 1 to 6, wherein one or more of the active metal layers (40) vary in composition along the stacking direction (S).

8. 8. The method according to claim 1, wherein the one or more solder layers (30) and the one or more active metal layers (40) are rolled as the solder system (35) so that the first thickness (D1) of the active metal layer (40) after rolling has a value of less than 750 nm.

9. 9. The method according to any one of the preceding claims, wherein a further active metal layer is provided, and the solder layer (30) is arranged between the active metal layer (40) and the further active metal layer.

10. 10. The method of any one of claims 1 to 9, wherein the ceramic layer (10) is coated with the active metal layer (40) and one or more of the metal layers (20) are coated with the solder layer (30).

11. 11. The method according to any one of the preceding claims, wherein one or more of the metal layers (20) have a layer thickness greater than 1 mm.

12. The one or more active metal layers (40) are covered by one or more protective layers (41); 12. The method according to any one of the preceding claims, wherein the protective layer (41) is made of copper, nickel, indium, silver, chromium, or titanium nitride.

13. A solder system (35) formed between one or more ceramic layers (10) and one or more metal layers (20) in a metal-ceramic substrate (1), comprising: The solder system (35) comprises one or more solder layers (30) in the form of one or more solder foils and one or more active metal layers (40); one or more of said ceramic layers (10) and / or one or more of said metal layers (20) and / or one or more of said solder layers (30) are coated with one or more active metal layers (40); one or more of the metal layers (20) are joined to one or more of the ceramic layers (10) via the solder system (35); the solder material of the one or more solder layers (30) is a silver-based or copper-based solder material; the solder material of the solder layer (30) is AgCuIn, AgCuGa, CuIn, CuGa, CuInSn, or CuGaSn; the first thickness (D1) of the one or more active metal layers (40) is between 150 nm and 750 nm; a ratio of the first thickness (D1) of the active metal layer (40) to the second thickness (D2) of the solder layer (30) is between 0.003 and 0.5; The solder system (35) wherein one or more of the active metal layers (40) are vapor deposited layers.

14. A metal ceramic substrate (1), one or more ceramic layers (10), one or more metal layers (20), and one or more solder layers (30) in the form of one or more solder foils; one or more of said ceramic layers (10) and / or one or more of said metal layers (20) and / or one or more of said solder layers (30) are coated with one or more active metal layers (40); One or more solder layers (30) are disposed between one or more of the ceramic layers (10) and one or more of the metal layers (20) along a stacking direction (S), forming a solder system (35) including one or more of the solder layers and one or more of the active metal layers (40); one or more of the metal layers (20) are joined to one or more of the ceramic layers (10) via the solder system (35); the solder material of the one or more solder layers (30) is a silver-based or copper-based solder material; the solder material of the solder layer (30) is AgCuIn, AgCuGa, CuIn, CuGa, CuInSn, or CuGaSn; the first thickness (D1) of the one or more active metal layers (40) is between 150 nm and 750 nm; a ratio of the first thickness (D1) of the active metal layer (40) to the second thickness (D2) of the solder layer (30) is between 0.003 and 0.5; The metal-ceramic substrate (1) wherein one or more of said active metal layers (40) are vapor-deposited layers.

15. The one or more active metal layers (40) are covered by one or more protective layers (41); 15. The metal-ceramic substrate (1) according to claim 14, wherein the protective layer (41) is made of copper, nickel, indium, silver, chromium, or titanium nitride.

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