Method for manufacturing metal-ceramic substrate, welding system and metal-ceramic substrate manufactured by using the method

Abstract

A method for producing a metal-ceramic substrate (1), the method comprising: providing at least one ceramic layer (10), at least one metal layer (20) and at least one solder layer (30), the solder layer being in particular in the form of at least one solder foil, coating at least one ceramic layer (10) and / or at least one metal layer (20) and / or at least one solder layer (30) with at least one active metal layer (40), arranging at least one solder layer (30) between at least one ceramic layer (10) and at least one metal layer (20) along a stacking direction (S) to form a soldering system (35), the soldering system comprising at least one solder layer and at least one active metal layer (40), wherein the soldering material of at least one solder layer (30) is free of materials which lower the melting point, and bonding at least one metal layer (20) to at least one ceramic layer (10) via the soldering system (35) by means of an active solder method.

Description

Technical Field

[0001] The invention relates to a method for producing a metal-ceramic substrate, a welding system for this method, and a metal-ceramic substrate produced in this way. Background Art

[0002] Metal-ceramic substrates, for example as printed circuit boards or circuit boards, are well known from the prior art, for example from DE 10 2013 104 739 A1, DE 19 927 046 B4, and DE 10 2009 033 029 A1. Typically, connection areas for electrical components and conductor tracks are provided on the component side of the metal-ceramic substrate, where the electrical components and conductor tracks can be interconnected to form a circuit. The essential components of a metal-ceramic substrate are an insulating layer, preferably made of ceramic, and at least one metal layer bonded to the insulating layer. Due to their relatively high dielectric strength, insulating layers made of ceramic have proven particularly advantageous in power electronics. By structuring the metal layer, conductor tracks and / or connection areas for the electrical components can then be implemented.

[0003] A prerequisite for providing such a metal-ceramic substrate is that the metal layer is permanently bonded to the ceramic layer. In addition to so-called direct bonding methods, ie DCB or DAB methods, bonding a metal layer to a ceramic layer via a solder material is known from the prior art.

[0004] The following method is understood to be an active solder method, for example, for connecting metal layers or metal foils, particularly copper layers or copper foils, to ceramic materials. This method is specifically designed for producing metal-ceramic substrates. Here, a connection is established between a metal foil, such as a copper foil, and a ceramic substrate, such as an aluminum nitride ceramic, at temperatures between approximately 650°C and 1000°C using a brazing material. The brazing material contains an active metal in addition to main components such as copper, silver, and / or gold. The active metal, for example, at least one element from the group Hf, Ti, Zr, Nb, and Ce, chemically reacts to form a connection between the brazing material and the ceramic, while the connection between the brazing material and the metal forms a metallic brazing connection.

[0005] For example, EP 3 041 042 A1 and WO 2017 / 126653 A1 disclose methods for producing power module substrates using active solder materials. Specifically, they propose bonding a copper foil to a ceramic layer via a multilayer solder system. The multilayer system consists of a layer of titanium foil and a layer of a phosphorus-containing solder filler material. Summary of the Invention

[0006] Based on this prior art, the object of the present invention is to achieve bonding of a metal layer to a ceramic layer using an improved welding system compared to the prior art, in particular with regard to the welding layer connecting the metal layer and the bonding process during active welding.

[0007] This object is achieved by the method according to the invention for producing a metal-ceramic substrate, the welding system according to the invention for this method, and the metal-ceramic substrate according to the invention produced in this method. Further advantages and characteristics can be seen from the description and the drawings.

[0008] According to a first aspect of the present invention, a method for manufacturing a metal-ceramic substrate is provided, the method comprising:

[0009] - providing at least one ceramic layer, at least one metal layer and at least one solder layer, in particular in the form of at least one solder foil or brazing material foil,

[0010] - coating of at least one ceramic layer and / or at least one metal layer and / or at least one solder layer with at least one active metal layer,

[0011] - at least one welding layer is arranged between at least one ceramic layer and at least one metal layer in the stacking direction to form a welding system, the welding system comprising at least one welding layer and at least one active metal layer, wherein the welding material of the at least one welding layer is preferably free of melting point lowering materials and / or free of phosphorus, and

[0012] Bonding the at least one metal layer to the at least one ceramic layer via a soldering system by means of an active solder method.

[0013] Compared to methods known from the prior art for producing metal-ceramic substrates, the present invention proposes a multilayer soldering system consisting of at least one solder layer, preferably free of melting-point-lowering elements, and at least one active metal layer. The separation of the at least one active metal layer and the at least one solder layer has proven particularly advantageous, as it allows for relatively thin solder layers, particularly when the solder layer is a foil. In other cases, with active metal-containing solder materials, relatively large solder layer thicknesses are necessary due to brittle intermetallic phases that hinder deformation of the solder paste or solder layer. Consequently, the minimum layer thickness is limited by the production characteristics of the active metal-containing solder material. Accordingly, with active metal-containing solder layers, the minimum solder layer thickness is not determined by the minimum thickness required for the joining method, but rather by the minimum technically achievable solder layer thickness. Consequently, thicker active metal-containing solder layers are more expensive than thinner layers.

[0014] By separating the active metal from the at least one solder layer, the solder layer thickness of the at least one solder layer can be advantageously reduced. This allows for material savings in the solder system or the at least one solder layer. It has proven particularly advantageous that such a solder layer free of active metal can also be rolled to a thickness of less than 10 μm, preferably less than 7 μm. Another advantage is that etching of the structured portion of the finished metal-ceramic substrate is simplified, particularly because the second thickness of the solder system or the at least one solder layer is reduced. Furthermore, bonding of the metal layer to the ceramic layer can be accelerated during production.

[0015] In particular, it has been shown that using a separate active metal layer is feasible if the solder layer is free of melting point-lowering elements and / or phosphorus. This provides greater flexibility in selecting the material to be used for the at least one solder layer, and allows the use of established process parameters for the active solder method. Furthermore, the addition of the corresponding melting point-lowering element in the preparatory phase for forming the at least one solder layer can advantageously be omitted. In particular, those skilled in the art understand at least one solder layer free of melting point-lowering elements to mean a layer containing less than 3% by weight, preferably less than 2% by weight, and particularly preferably less than 1% by weight of the melting point-lowering element. Examples of such melting point-lowering elements are phosphorus and zinc. For example, using a phosphorus-free solder material allows for an advantageous separation of the active metal layer and the solder layer, even for solder layers that are free of phosphorus but still contain a melting point-lowering material. The integration of this melting point-lowering material into the solder layer again results in a lowering of the melting point that is not as significant as that known for phosphorus. For example, this refers to a melting point-lowering material that lowers the melting point of the solder layer by less than 100°C, preferably less than 80°C, and particularly preferably less than 50°C.

[0016] Furthermore, it is preferably provided that at least one solder layer is free of active metals. In particular, a person skilled in the art understands free of active metals to mean that the solder layer contains less than 5% by weight, preferably less than 3% by weight, and particularly preferably less than 1.5% by weight of active metals. Examples of active metals are titanium (Ti), zirconium (Zr), hafnium (Hf), chromium (Cr), niobium (Nb), cerium (Ce), and vanadium (V). It is particularly preferred that at least one solder layer be provided as a foil. This allows for the simplest possible handling of the foil when it is positioned between at least one ceramic layer and at least one metal layer, particularly in the mass production of metal-ceramic substrates.

[0017] For example, it is also conceivable to already provide at least one solder layer comprising a metal layer or at least one metal layer. For example, the at least one solder layer is applied to one side of the at least one metal layer used to produce the metal-ceramic substrate. In this case, the at least one metal layer serves as a carrier for the at least one solder layer. However, it is also conceivable to provide the at least one solder layer on a foil forming a carrier, such as a plastic foil. Furthermore, it is conceivable to provide the at least one solder layer on the at least one metal layer and to apply at least one further metal layer, preferably having a different particle size distribution or a different average particle size, on the side of the at least one metal layer, preferably supporting the at least one solder layer, facing away from the solder layer. In particular, it is provided that the particle sizes, in particular the average particle sizes, of the at least one metal layer and the at least one further metal layer differ from one another, so that during the bonding method, a two-layer metallization layer is formed on the upper side of the ceramic. It is particularly preferred that the metal layer having the smaller average particle size is located on the outside, while the metal layer having the larger average particle size faces the solder system or ceramic layer.

[0018] It has proven particularly advantageous if at least one active metal layer can be selectively applied to at least one ceramic layer and / or at least one metal layer and / or at least one solder layer. Preferably, the at least one active metal layer is applied to at least two of the aforementioned layers. Preferably, the at least one active metal layer is disposed on the side of the at least one ceramic layer or the at least one metal layer that, in the disposed state or in the metal-ceramic substrate, faces the at least one solder layer. It is particularly preferred that the at least one active metal layer be applied to the at least one solder layer. In this case, a soldering system consisting of at least one solder layer and at least one active metal layer can be provided, which can be easily applied between the at least one ceramic layer and the at least one metal layer using an active solder method. The bonding method is an active solder method carried out at a process temperature between 600°C and 1000°C, preferably between 700°C and 950°C.

[0019] Preferably, the solder material of at least one solder layer is a silver- or copper-based solder material. In silver-based solder materials, silver is the main component, i.e., the component with the highest weight percentage, while in copper-based solder materials, copper is the main component. Examples of silver-based solder materials are AgCu, in particular AgCu28, AgCu1n, AgCuSn, and AgCuGa. Examples of copper-based solder materials are copper, CuSn, Cu1n, CuGa, Cu1nSn, Cu1nMn, and CuGaSn. Using NiCrMn as the solder material is also conceivable. In particular, it is preferably provided that the solder layer is free of silver, i.e., the solder layer contains less than 3% silver by weight, preferably less than 2% silver by weight, and particularly preferably less than 1% silver by weight. This advantageously saves silver, which otherwise could cause silver migration in the resulting metal-ceramic substrate.

[0020] It is preferably proposed that the solder layer or the solder material of the solder layer comprises multiple components and / or is free of silver. In other words, the solder material does not consist of a single chemical element. In particular, it is proposed that the solder layer does not consist solely of silver. It is preferably proposed that the solder layer comprises at least two different components or constituents. This advantageously makes it possible to further optimize the bonding behavior, for example in terms of adhesion strength and resistance to temperature changes. For example, regardless of the use of a pure silver layer, the silver migration and etching behavior of the pure silver layer have an adverse effect on the manufactured metal-ceramic substrate. Other examples of materials forming the solder layer as solder material are: CuNi and CuNiMn, in particular up to the operating temperature of the solder of 1050°C. Pure silver is also conceivable.

[0021] Conceivable materials for the at least one metal layer include copper, aluminum, molybdenum, and / or their alloys, as well as laminates and powder metallurgy composites such as CuW, CuMo, CuAl, AlCu, and / or CuCu, in particular a copper sandwich structure having a first copper layer and a second copper layer, wherein the grain size in the first copper layer differs from that in the second copper layer. Furthermore, it is preferably provided that the at least one metal layer is surface-modified. Conceivable surface modifications include, for example, seals with precious metals, in particular silver and / or gold, or electroless nickel immersion gold (ENIG), or edge encapsulation of the first or second metallization layer to suppress crack formation or propagation.

[0022] Preferably, at least one ceramic layer comprises Al2O3, Si3N4, AlN, HPSX ceramic (i.e., a ceramic with an Al2O3 matrix containing x percentage of ZrO2, for example, Al2O3 with 9% ZrO2 = HPS9, or Al2O3 with 25% ZrO2 = HPS25), SiC, BeO, MgO, high-density MgO (>90% of theoretical density), TSZ (tetragonal stabilized zirconium oxide), or ZTA as the ceramic material. It is also conceivable for the insulating layer to be designed as a composite or hybrid ceramic, wherein, to combine different desired properties, multiple ceramic layers, each differing in their material composition, are arranged one above the other and joined to form the insulating layer. Highly thermally conductive ceramics are preferably used to minimize thermal resistance.

[0023] According to a preferred embodiment, the at least one active metal layer is applied by means of a vapor deposition method, in particular a physical vapor deposition method (PVD), or by means of chemical vapor deposition (CVD). This production method makes it possible to provide a similarly thin active metal layer that is applied as uniformly as possible. In particular, the most controlled application possible is possible, so that the at least one applied active metal layer has a thickness that is as constant as possible on the coating surface. For example, vapor deposition methods such as 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 technology can be used.

[0024] Advantageously, the first thickness of the at least one active metal layer has a value between 100 nm and 1000 nm, preferably between 150 nm and 750 nm, and particularly preferably between 200 nm and 500 nm. Such a thin active metal layer advantageously prevents a reduction in thermal conductivity and a reduction in the mechanical strength of the metal-ceramic substrate, particularly at the interface between the at least one ceramic layer and the at least one metal layer. The layer thickness is particularly preferably coordinated with the expected storage time. For example, for long storage times, such as storage times of more than 10 days, it has proven advantageous, particularly for titanium as the active metal layer, to use a layer thickness between 750 nm and 1000 nm. For shorter storage times, it is feasible to use a first thickness of 150 nm to 350 nm.

[0025] Preferably, the active solder method is less than 10 -2 mbar, preferably less than 10 -3 mbar, and particularly preferably less than 10 -4The active soldering process is carried out under a pressure of 100 mbar and / or with process gases. For example, the active soldering process is carried out under a high vacuum or fine vacuum with very low oxygen and an argon partial pressure of less than 1 mbar. Alternatively, it is also conceivable to work under an argon atmosphere or generally a noble gas atmosphere. Since no organic binder is used, it is possible to cut the process time in half.

[0026] It is also preferred that the second thickness of the at least one solder layer has a value between 1 μm and 100 μm, preferably between 1.5 μm and 50 μm, and particularly preferably between 2 μm and 20 μm, or even less than 10 μm. This relates particularly to the second thickness before the bonding process, i.e., the active solder method. It is particularly preferred that the at least one solder layer is further reduced before the bonding process, for example by rolling to a thickness of less than 10 μm, preferably less than 7 μm, and particularly preferably less than 5 μm. This advantageously enables the layer thickness of the solder material or at least one solder layer to be further reduced. It is also preferred that the at least one solder layer is reduced in thickness by roll-coating before being arranged between the at least one ceramic layer and the at least one metal layer. This allows the thinner solder layer to be achieved even before the at least one solder layer is reduced (for example by rolling) in a further soldering step to the final layer thickness intended for the bonding process.

[0027] In particular, it is proposed that the ratio of the first thickness of the active metal layer to the second thickness of the solder layer adopts a value between 0.003 and 0.5, preferably between 0.015 and 0.2, and particularly preferably between 0.03 and 0.14. In other words, the second thickness of the solder layer is significantly greater than the first thickness of the active metal layer.

[0028] Furthermore, it is preferably provided that the at least one active metal layer is covered by at least one protective layer. The at least one protective layer advantageously prevents oxidation of the at least one active metal layer. 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 at least one active metal layer. The thickness of the at least one protective layer is at least 100 nm. It is particularly preferably provided that the thickness of the at least one protective layer, i.e., the third thickness, is adapted to the storage time, i.e., the time elapsed between application of the at least one active metal layer and the actual bonding process during the active soldering process. This advantageously ensures that the component covered by the at least one active metal layer (whether the at least one metal layer and / or the at least one active metal layer and / or the at least one solder layer) can be stored permanently without the at least one active metal layer being oxidized even in the preparatory phase of the bonding process. For example, the layer thickness of the at least one protective layer, ie the third thickness, is between 100 nm or 50 nm and 1000 nm, preferably between 150 nm and 750 nm and particularly preferably between 250 nm and 500 nm.

[0029] Furthermore, it is preferably provided that the ratio of the third thickness of the at least one protective layer to the first thickness of the at least one active metal layer, measured in the stacking direction, assumes a value between 0.5 and 1, preferably between 0.7 and 0.9, and particularly preferably between 0.75 and 0.85.

[0030] Furthermore, it is preferably provided that the composition of at least one active metal layer changes in the stacking direction. This also advantageously prevents premature oxidation of the active metal layer, in particular by increasing the proportion of embedded elements such as nitrogen, oxygen, or carbon with increasing distance from the surface coated with the active metal (whether the at least one metal layer, the at least one ceramic layer, or the at least one ceramic layer). It is also conceivable that, to extend the storage life of a component or member provided with at least one active metal layer, the at least one active metal layer, whether the at least one metal layer, the at least one ceramic layer, and / or the at least one weld layer, is covered by at least one further weld layer. The thickness of the at least one further weld layer is at least thinner than the second thickness of the at least one weld layer by a factor of 0.1, preferably 0.05, and particularly preferably 0.01. The weld system advantageously forms a sandwich structure, wherein the at least one active metal layer is enclosed or surrounded by the at least one weld layer and the at least one further weld layer.

[0031] It is preferably provided that at least one weld layer and / or at least one active metal layer are rolled, preferably such that the first thickness of the active metal layer after rolling and / or pressing has a value of less than 1000 nm, preferably less than 750 nm, and particularly preferably less than 500 nm. It is therefore advantageously possible to achieve a first thickness of the active metal layer, in particular less than 1000 nm, by rolling the weld layer and the active metal layer together, as an alternative to coating by means of an electroplating method or a vapor deposition method. The layer thicknesses of the weld layer and the active metal layer, i.e., the first thickness and the second thickness, are rolled and / or pressed together. To this end, the weld layer, for example, in the form of a thick weld foil, and the active metal layer are first joined together, for example, by means of upstream rolling or a first rolling process to reduce the layer thickness. It is preferably provided that the ratio of the initial layer thickness of the active metal layer and the initial layer thickness of the weld foil to one another is the same as the ratio of the first thickness and the second thickness to one another in a completed weld system comprising an active metal layer of the first thickness and a weld layer of the second thickness. By subsequent rolling, in particular multiple rolling passes, the active metal layer and the solder layer are reduced in their respective thicknesses with each rolling pass, so that a relatively thin solder layer is obtained, on which a thinner active metal layer is arranged. This solder system can then be used to bond the metal layer to the ceramic layer during the active solder method.

[0032] It is particularly preferred that a further active metal layer is provided, wherein the solder layer is arranged between the active metal layer and the further active metal layer. Thus, the interface between the solder layer and the at least one metal layer can also be influenced by the active metal of the active metal layer.

[0033] Furthermore, it is preferably provided that the ceramic layer is coated with an active metal layer and that at least one metal layer is coated with a solder layer.

[0034] It is particularly preferred that the at least one metal layer has a layer thickness of greater than 1 mm, preferably greater than 1.3 mm, and particularly preferably greater than 1.5 mm. This results in at least one relatively thick metal layer that supports rapid dissipation of thermal energy and already achieves heat diffusion at the component side.

[0035] Another subject matter of the present invention is a welding system for the method according to the invention, wherein the welding system comprises at least one welding layer, in particular in the form of a welding foil, and at least one active metal layer. All advantages and features described for the method for producing a metal-ceramic substrate apply analogously to the welding system.

[0036] Another subject matter is a metal-ceramic substrate produced by a method comprising providing at least one ceramic layer, at least one metal layer and at least one solder layer, in particular in the form of at least one solder foil,

[0037] - coating of at least one ceramic layer and / or at least one metal layer and / or at least one solder layer with at least one active metal layer,

[0038] - at least one welding layer is arranged between at least one ceramic layer and at least one metal layer in the stacking direction to form a welding system, the welding system comprising at least one welding layer and at least one active metal layer, wherein the welding material of the at least one welding layer preferably does not contain a material that lowers the melting point, and

[0039] Bonding the at least one metal layer to the at least one ceramic layer via a soldering system by means of an active solder method. All advantages and features described for the method for producing a metal-ceramic substrate apply analogously to the metal-ceramic substrate. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Further advantages and features will be apparent from the following description of preferred embodiments of the subject matter of the invention with reference to the accompanying drawings. Within the scope of the invention, individual features of the individual embodiments can be combined with one another.

[0041] The accompanying drawings show:

[0042] Figure 1 Schematically illustrating a method for producing a metal-ceramic substrate according to a first preferred embodiment of the present invention,

[0043] Figure 2 Schematically illustrating a method for producing a metal-ceramic substrate according to a second preferred embodiment of the present invention,

[0044] Figure 3 Schematically illustrating a method for producing a metal-ceramic substrate according to a third preferred embodiment of the present invention,

[0045] Figure 4 Schematically shows a method for producing a metal-ceramic substrate according to a fourth preferred embodiment of the present invention, and

[0046] Figure 5 A method for producing a metal-ceramic substrate according to a fifth preferred embodiment of the present invention is schematically shown. DETAILED DESCRIPTION

[0047] exist Figure 1Schematically depicts a method for producing a metal-ceramic substrate 1 according to a first preferred embodiment of the present invention. The metal-ceramic substrate 1 is preferably used as a carrier for electronic or electrical components that can be bonded to the metal-ceramic substrate 1. An example of a finished metal-ceramic substrate 1 is schematically depicted in the upper left corner. The essential components of such a metal-ceramic substrate 1 are at least one ceramic layer 10 extending along a main plane of extension HSE and at least one metal layer 20 bonded to the at least one ceramic layer 10. The at least one ceramic layer 10 is made of at least one material comprising ceramic. The at least one metal layer 20 and the at least one ceramic layer 10 are arranged one above the other along a stacking direction S extending perpendicularly to the main plane of extension HSE and, in the finished state, are materially bonded to one another at least in regions via a welding system 35. Preferably, the at least one metal layer 20 in the finished metal-ceramic substrate 1 is then structured to form conductor tracks or bonding points for the electrical component. For example, the structuring is etched into the at least one metal layer 20. However, a permanent bond, in particular a material-bonding bond, must be formed beforehand between the at least one metal layer 20 and the at least one ceramic layer 10 .

[0048] exist Figure 1 In the exemplary embodiment, this durable, particularly cohesive bond is achieved by means of an active solder method. To this end, a soldering system 35 is provided between at least one ceramic layer 10 and at least one metal layer 20, via which a cohesive bond between the ceramic layer 10 and the metal layer 20 is ensured in the finished metal-ceramic substrate 1. It is particularly provided that the soldering system 35 is multi-layered. In addition to at least one soldering layer 30, the soldering system 35 also includes at least one active metal layer 40. It is particularly provided that at least one soldering layer 30 is free of active metal, i.e., contains no active metal. Alternatively, the active metal is provided as a separate layer in the soldering system 35 as the active metal layer 40. It has been found that this separation in the soldering system 35, wherein a solder material free of active metal is provided in the soldering layer 30 on one side and an active metal layer 40 containing active metal is provided on the other side, advantageously allows for the creation of a soldering layer 30 that is as thin as possible. In other cases, for the at least one welding layer 30 , in particular in the form of a welding foil, a greater minimum layer thickness must be tolerated, which is limited by the production process of the at least one welding layer 30 and not by the minimum thickness required for the joining process.

[0049] By separating the at least one active metal layer 40 and the at least one solder layer 30, a correspondingly thinner solder foil can be produced, since there are no brittle intermetallic phases that hinder deformation. In particular, this advantageously allows for providing a solder layer 30 that ensures that the at least one solder layer 30, in particular in the form of a solder foil, can be rolled to a thickness of less than 10 μm, preferably less than 8 μm, and particularly preferably less than 6 μm. In the illustrated embodiment, the at least one active metal layer 40 is applied to the at least one ceramic layer 10, for example, by means of spraying or CVD, and has a first thickness D1 having a value between 100 nm and 1000 nm, preferably between 150 nm and 750 nm, and particularly preferably between 200 nm and 500 nm.

[0050] Such a thin active metal layer 40 prevents the reduction in thermal conductivity and mechanical strength that would otherwise be expected with thicker active metal layers 40. This is particularly true for layer thicknesses, or first thickness D1, between 200 nm and 500 nm. It is proposed that at least one solder layer 30, particularly as at least one solder foil, be disposed as a separate layer between the at least one active metal layer 40 and the at least one metal layer 20 before the active solder process is performed. For example, it is conceivable to apply the at least one solder foil to the at least one active metal layer 40 and, in a rolling step, to a second thickness of less than 10 μm, preferably less than 7 μm, in order to ensure that the at least one solder layer 30 is as thin as possible. The use of a relatively thin at least one solder layer 30 accelerates the bonding process and, moreover, advantageously reduces material requirements when establishing the connection between the at least one ceramic layer 10 and the at least one metal layer 20. The at least one ceramic layer 10 and the at least one metal layer 20 are disposed one above the other in a stacking direction S, with the soldering system 35 comprising the at least one solder layer 30 and the at least one active metal layer 40 disposed between the at least one metal layer 20 and the at least one ceramic layer 10 in the stacking direction S. In particular, it is proposed that the at least one solder layer 30 be free of both active metals and melting point-lowering elements, such as phosphorus or zinc. A person skilled in the art understands "free of melting point-lowering elements" to mean that their proportion in the solder layer is less than 3% by weight, preferably less than 2% by weight, and particularly preferably less than 1% by weight. For example, the at least one solder layer 30 dispenses with solder materials containing phosphorus or zinc to prevent a reduction in the melting temperature. Surprisingly, bonding via the at least one active metal layer 40 alone is possible even with solder materials that do not contain melting point-lowering elements. This allows the use of a relatively thin at least one solder layer 30 for solder materials used at typical process temperatures in active solder methods. Accordingly, typical process parameters typically used in active solder methods can be used, allowing the creation of a relatively thin at least one solder layer 30.

[0051] exist Figure 2 Schematically shows a method for producing a metal-ceramic substrate 1 according to a second exemplary embodiment of the present invention. In particular, Figure 2 Examples and Figure 1The embodiment of FIG. 4 differs essentially only in that, in addition to the at least one active metal layer 40, at least one protective layer 41 is provided. The at least one protective layer 41, which extends in the main extension plane HSE, in particular covers the active metal layer 40. The use of this at least one protective layer 41 advantageously prevents oxidation on the at least one active metal layer 40 or on the outer side of the at least one active metal layer 40 before the actual bonding process, i.e., the active solder method, is performed. Preferably, this at least one protective layer 41 has a third thickness D3 with a minimum thickness of at least 100 nm. Preferably, the third thickness D3 of the at least one protective layer is between 100 nm and 1000 nm, preferably between 150 nm and 750 nm, and particularly preferably between 200 nm and 500 nm. Furthermore, it is preferably provided that the at least one protective layer 41 partially or preferably completely covers the at least one active element layer 40 and is disposed between the at least one active metal layer 40 and the at least one solder layer 30, as viewed in the stacking direction S. Preferably, the third thickness D3 is adapted to the expected duration from the deposition of the active metal layer (40) and the protective layer (41) until bonding by means of the active solder method. Thus, the required storage time can be advantageously achieved, in particular by the third thickness D3 of the protective layer 41, in order to ensure that the at least one active metal layer 40 does not undergo oxidation before bonding. It is preferably provided that the third thickness D3 of the at least one protective layer 41 substantially corresponds to the first thickness D1 of the active metal layer 40.

[0052] Furthermore, it is proposed that the at least one solder layer 30 has a second thickness D2 having a value between 0.1 μm and 100 μm, preferably between 0.5 μm and 50 μm, and particularly preferably between 0.2 μm and 20 μm. This relates particularly to the second thickness D2 before the at least one solder layer 30 is placed or arranged on the at least one metal layer 20 or the at least one active metal layer 40. It is particularly proposed that after the at least one metal layer 20 is applied or arranged, the second thickness D2 of the at least one solder layer 30 is further reduced by further rolling. After the at least one metal layer 20, the at least one ceramic layer 10, and the solder system 35 arranged between the at least one metal layer 20 and the at least one ceramic layer 10 are provided, bonding is performed at a temperature between 700° C. and 900° C. The soldering method is preferably performed at a pressure of less than 10 mbar. It is also conceivable that the bonding method, i.e., the active solder method, is performed using a process gas or in a working atmosphere, for example, including argon or generally one or more noble gases.

[0053] exist Figure 3 Schematically shows a method for manufacturing a metal-ceramic substrate 1 according to a third exemplary embodiment of the present invention. Figure 2The difference between the exemplary embodiments in FIG. 4 is essentially that the at least one active metal layer 40 is bonded to the at least one solder layer 30 before being arranged between the at least one metal layer 20 and the at least one ceramic layer 10. In other words, the bonding of the at least one active metal layer 40 to the at least one solder layer 30 by means of spraying takes place before the at least one ceramic layer 10 and the at least one metal layer 20 are arranged. In particular, it is provided that the at least one protective layer 41 also partially or preferably completely covers the at least one active metal layer 40, in particular on one side, in order to prevent premature oxidation of the at least one active metal layer 40.

[0054] exist Figure 4 Schematically shows a method for manufacturing a metal-ceramic substrate 1 according to a fourth embodiment of the present invention. Figure 2 and Figure 3 In contrast to the embodiment in Figure 4 In an embodiment of the present invention, it is provided that at least one active metal layer 40 is bonded to at least one metal layer 20 before the active soldering method. In this case, the at least one active metal layer 40 is particularly arranged on the side of the at least one metal layer 20 that faces the solder layer 30 during the bonding process. For example, the at least one active metal layer 40 can be applied to the at least one metal layer 20 over its entire surface by means of a CVD method or by spraying, that is, typically by means of a vapor deposition method. After the at least one metal layer 20 with the at least one active metal layer 40 attached thereto and the at least one ceramic layer 10 and the at least one solder layer 30 are provided, the bonding method is carried out by means of the active soldering method.

[0055] exist Figure 5 Schematically shows a method for producing a metal-ceramic substrate 1 according to a fifth preferred embodiment of the present invention. Here, Figure 5 Examples and Figure 2 The difference between the embodiments in FIG. 1 is that the front side and the back side of at least one ceramic layer 10 are respectively connected to at least one metal layer 20 via corresponding welding systems 35, wherein the welding system 35 preferably includes at least one welding layer 30, at least one active metal layer 40 and at least one protective layer 41.

[0056] Reference Signs List

[0057] 1 Metal-ceramic substrate

[0058] 10 Ceramic layer

[0059] 20 metal layers

[0060] 30 welding layers

[0061] 35 Welding System

[0062] 40 Active metal layer

[0063] 41 protective layer

[0064] S Stacking direction

[0065] HSE Main Extension Plane

[0066] D1 first thickness

[0067] D2 Second thickness

[0068] D3 third thickness

Claims

1. A method for manufacturing a metal-ceramic substrate (1), the method comprising: - providing at least one ceramic layer (10), at least one metal layer (20) and at least one solder layer (30), - coating the at least one ceramic layer (10) and / or the at least one metal layer (20) and / or the at least one solder layer (30) with at least one active metal layer (40), - arranging the at least one welding layer (30) between the at least one ceramic layer (10) and the at least one metal layer (20) along the stacking direction (S) to form a welding system (35), the welding system comprising the at least one welding layer and the at least one active metal layer (40), and - bonding the at least one metal layer (20) to the at least one ceramic layer (10) via the soldering system (35) by means of an active solder method, wherein the at least one metal layer (20) in the produced metal-ceramic substrate (1) is structured to form conductor tracks or bonding sites for electrical components, wherein the first thickness (D1) of the at least one active metal layer (40) has a value between 100 nm and 1000 nm, wherein a ratio of a first thickness (D1) of the active metal layer (40) to a second thickness (D2) of the welding layer (30) is between 0.003 and 0.5, The material of the welding layer is AgCuIn, AgCuGa, CuIn, CuGa, CuInSn, CuInMb, CuGaSn, CuNi, CuNiMn and / or NiCrMn, wherein at least one active metal layer is covered by at least one protective layer, wherein copper (Cu), nickel (Ni), indium (In), silver (Ag), chromium (Cr) or titanium nitride (TiN) is used as the protective layer for the at least one active metal layer, wherein the solder material of the at least one solder layer (30) is free of phosphorus and free of materials that lower the melting point, and The at least one active metal layer (40) is applied by means of a vapor deposition method. The method according to claim 1 , wherein the at least one welding layer is in the form of at least one welding foil.

3. The method according to claim 1 or 2, wherein the solder layer (30) comprises a plurality of components and / or is free of silver.

4. The method according to claim 1 or 2, wherein the first thickness (D1) of the at least one active metal layer (40) has a value between 150 nm and 750 nm.

5. Method according to claim 4, wherein the first thickness (D1) of the at least one active metal layer (40) has a value between 200 nm and 500 nm.

6. The method according to claim 1 or 2, wherein -The active solder method is less than 10 -2 mbar, and / or The active solder method is performed using a process gas.

7. The method according to claim 6, The active solder method is less than 10 -3 mbar pressure.

8. The method according to claim 6, The active solder method is less than 10 -4 mbar pressure.

9. Method according to claim 1 or 2, wherein the second thickness (D2) of the at least one solder layer (30) has a value between 1 μm and 100 μm.

10. Method according to claim 9, wherein the second thickness (D2) of the at least one solder layer (30) has a value between 1.5 μm and 50 μm.

11. Method according to claim 9, wherein the second thickness (D2) of the at least one solder layer (30) has a value between 2 μm and 20 μm.

12. A method for manufacturing a metal-ceramic substrate (1), the method comprising: - providing at least one ceramic layer (10), at least one metal layer (20) and at least one solder layer (30), - coating the at least one ceramic layer (10) and / or the at least one metal layer (20) and / or the at least one solder layer (30) with at least one active metal layer (40), wherein the active metal layer is arranged between the solder layer and the ceramic layer, - arranging the at least one welding layer (30) between the at least one ceramic layer (10) and the at least one metal layer (20) along the stacking direction (S) to form a welding system (35), the welding system comprising the at least one welding layer and the at least one active metal layer (40), and - bonding the at least one metal layer (20) to the at least one ceramic layer (10) via the soldering system (35) by means of an active solder method, wherein the first thickness (D1) of the at least one active metal layer (40) has a value between 100 nm and 1000 nm, wherein a ratio of a first thickness (D1) of the active metal layer (40) to a second thickness (D2) of the welding layer (30) is between 0.003 and 0.5, The material of the welding layer is AgCuIn, AgCuGa, CuIn, CuGa, CuInSn, CuInMb, CuGaSn, CuNi, CuNiMn and / or NiCrMn, wherein at least one active metal layer is covered by at least one protective layer, wherein copper (Cu), nickel (Ni), indium (In), silver (Ag), chromium (Cr) or titanium nitride (TiN) is used as the protective layer for the at least one active metal layer, wherein the solder material of the at least one solder layer (30) is free of phosphorus and free of materials that lower the melting point, and The at least one active metal layer (40) is applied by means of a vapor deposition method.

13. The method according to claim 12, wherein the at least one welding layer is in the form of at least one welding foil.

14. The method according to claim 12 or 13, wherein a ratio of a first thickness (D1) of the active metal layer (40) to a second thickness (D2) of the welding layer (30) is between 0.015 and 0.

2.

15. The method of claim 14, wherein a ratio of a first thickness (D1) of the active metal layer (40) to a second thickness (D2) of the solder layer (30) is between 0.03 and 0.

14.

16. The method according to claim 12 or 13, wherein the composition of the at least one active metal layer (40) changes along the stacking direction (S).

17. The method according to claim 12 or 13, wherein the at least one weld layer (30) and / or the at least one active metal layer (40) are rolled.

18. The method according to claim 17, wherein the at least one welding layer (30) and / or the at least one active metal layer (40) are rolled as a welding system (35).

19. The method according to claim 17, wherein the at least one welding layer (30) and / or the at least one active metal layer (40) are rolled as a welding system (35) so that after the rolling, the first thickness (D1) of the active metal layer (40) has a value of less than 1000 nm.

20. The method according to claim 17, wherein the at least one welding layer (30) and / or the at least one active metal layer (40) are rolled as a welding system (35) so that after the rolling, the first thickness (D1) of the active metal layer (40) has a value of less than 750 nm.

21. The method according to claim 17, wherein the at least one welding layer (30) and / or the at least one active metal layer (40) are rolled as a welding system (35) so that after the rolling, the first thickness (D1) of the active metal layer (40) has a value of less than 500 nm.

22. The method according to claim 12 or 13, wherein a further active metal layer is provided, wherein the solder layer (30) is arranged between the active metal layer (40) and the further active metal layer.

23. The method according to claim 12 or 13, wherein the ceramic layer (10) is coated with the active metal layer (40) and the at least one metal layer (20) is coated with the solder layer (30).

24. The method according to claim 12 or 13, wherein the at least one metal layer (20) has a layer thickness of more than 1 mm.

25. The method according to claim 24, wherein the at least one metal layer (20) has a layer thickness of greater than 1.3 mm.

26. The method according to claim 24, wherein the at least one metal layer (20) has a layer thickness of greater than 1.5 mm.

27. A welding system (35) for use in the method according to any one of the preceding claims, wherein the welding system (35) comprises at least one welding layer (30) and at least one active metal layer (40).

28. The welding system (35) according to claim 27, wherein the at least one welding layer is in the form of at least one welding foil.

29. A metal-ceramic substrate (1) manufactured by a method comprising: - providing at least one ceramic layer (10), at least one metal layer (20) and at least one solder layer (30), - coating the at least one ceramic layer (10), the at least one metal layer (20) and / or the at least one solder layer (30) with at least one active metal layer (40), - arranging the at least one welding layer (30) between the at least one ceramic layer (10) and the at least one metal layer (20) along the stacking direction (S) to form a welding system (35), the welding system comprising the at least one welding layer and the at least one active metal layer (40), and - bonding the at least one metal layer (20) to the at least one ceramic layer (10) via the soldering system (35) by means of an active solder method, wherein the first thickness (D1) of the at least one active metal layer (40) has a value between 100 nm and 1000 nm, wherein a ratio of a first thickness (D1) of the active metal layer (40) to a second thickness (D2) of the welding layer (30) is between 0.003 and 0.5, The material of the welding layer is AgCuIn, AgCuGa, CuIn, CuGa, CuInSn, CuInMb, CuGaSn, CuNi, CuNiMn and / or NiCrMn, wherein at least one active metal layer is covered by at least one protective layer, wherein copper (Cu), nickel (Ni), indium (In), silver (Ag), chromium (Cr) or titanium nitride (TiN) is used as the protective layer for the at least one active metal layer, wherein the solder material of the at least one solder layer (30) is free of phosphorus and free of materials that lower the melting point, and The at least one active metal layer (40) is applied by means of a vapor deposition method.

30. The metal-ceramic substrate (1) according to claim 29, wherein the at least one solder layer is in the form of at least one solder foil.

Images