Support substrate and method for producing a support substrate

Abstract

The invention relates to a support substrate (1), in particular a metal-ceramic substrate, as a support for electric components in the form of a printed circuit board, comprising: - at least one metal layer (10) and - an insulation element (30), in particular a ceramic element, a glass element, a glass-ceramic element, and / or a high temperature-resistant plastic element, wherein the at least one metal layer (10) and the insulation element (30) extend along a main extension plane (HSE) and are arranged one over the other along a stacking direction (S) which runs perpendicularly to the main extension plane (HSE). A binding layer (12) is formed between the at least one metal layer (10) and the insulation element (30) in the completed support substrate (1), and a contact layer (13) of the binding layer (12) - comprises preferably a titanium-nitrogen compound and / or a titanium-silicon compound and - has a first thickness, which is measured in the stacking direction (S) and which is averaged over a plurality of measurement points within one or more specified surfaces (F) that run / runs parallel to the main extension plane (HSE), said thickness equaling less than 900 nm, preferably less than 700 nm, preferably less than 500 nm.

Description

[0001] Carrier substrate and method for producing a carrier substrate

[0002] The present invention relates to a carrier substrate and a method for producing a carrier substrate.

[0003] Carrier substrates, such as metal-ceramic substrates, are well known as printed circuit boards or circuit boards 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 pads for electrical components and conductor tracks are arranged on one component side of the metal-ceramic substrate or the carrier substrate, wherein the electrical components and the conductor tracks can be interconnected to form electrical circuits. Key components of the metal-ceramic substrates are an insulating layer, preferably made of a ceramic, and at least one metal layer bonded to the insulating layer. Due to their comparatively high insulation strengths, insulating layers made of ceramic have proven particularly advantageous in power electronics.By structuring the metal layer, conductor tracks and / or connection surfaces for the electrical components can then be realized.

[0004] A prerequisite for the successful provision of a metal-ceramic substrate is a permanent bond between the metal layer and the ceramic layer. In addition to a so-called direct metal bonding process, i.e., a DCB or DAB process, it is known from the state of the art to bond the metal layer to the ceramic layer using a solder material (AMB process).

[0005] An active soldering process, e.g. for joining metal layers or metal foils, in particular copper layers or copper foils, to ceramic material, is understood here to be a process that is specifically used to produce metal-ceramic substrates. In this process, a bond is created between a metal foil, e.g. a copper foil, and a ceramic substrate, e.g. an aluminum nitride ceramic, at a temperature of approximately 650-1000°C using a brazing alloy that, in addition to a main component such as copper, silver, and / or gold, also contains an active metal. This active metal, which is, for example, at least one element from the group consisting of Hf, Ti, Zr, Nb, and Ce, creates a bond between the solder and the ceramic through a chemical reaction, while the bond between the solder and the metal is a metallic brazing alloy.

[0006] Furthermore, a process is known, for example, from DE 10 2013 113 734 B4 and from JP 4-325 470, in which a metal layer is bonded to a ceramic layer by means of hot isostatic pressing to form a metal-ceramic substrate. Hot isostatic pressing is also used for post-treatment to reduce the number of voids formed during bonding using a soldering process or a direct metal bonding process.

[0007] Based on the prior art, the present invention has for its object to provide a carrier substrate, in particular a metal-ceramic substrate, which is further improved compared to the known carrier substrates, in particular with regard to the thermal performance of the carrier substrate.

[0008] The present invention solves this problem with a carrier substrate according to claim 1 and a method for producing a carrier substrate according to claim 7. Further embodiments can be found in the dependent claims and the description.

[0009] According to a first aspect of the present invention, a carrier substrate, in particular a metal-ceramic substrate, is provided as a carrier for electrical components in the form of a printed circuit board, comprising:

[0010] - at least one metal layer and

[0011] - an insulation element, in particular a ceramic element, a glass element, a glass-ceramic element and / or a high-temperature-resistant plastic element, wherein the at least one metal layer and the insulation element extend along a main extension plane and are arranged one above the other along a stacking direction running perpendicular to the main extension plane, wherein a bonding layer is formed between the at least one metal layer and the insulation element in the manufactured carrier substrate, and wherein a contact layer of the bonding layer preferably comprises a titanium-nitrogen compound and a titanium-silicon compound and has a first thickness measured in the stacking direction, averaged over several measuring points within one or more predetermined areas which run or run parallel to the main extension plane, which is less than 900 nm, preferably less than 700 nm and preferably less than 500 nm or even less than 350 nm.

[0012] Compared to the carrier substrates known from the prior art, the carrier substrate according to the invention proves to be particularly advantageous because the reduced contact layer improves the thermal conductivity of the system, which is composed of the insulation element and the bonding layer. Otherwise, the contact layer proves to be a thermal resistor, which becomes more influential as the thickness increases. It has been found that by significantly reducing the contact layer thickness, it is advantageously possible to significantly improve the thermal conductivity of the entire system. These are preferably titanium nitride and / or titanium silicon compounds in various stoichiometric compounds, which are formed in the contact layer. They are in particular the result of the use of an active metal layer made of titanium oran active metal layer comprising titanium, which bonds with components of the insulating element during a bonding process. The resulting bonds during the bonding process form the contact layer. It has been found that by specifically adjusting the active metal layer, it is possible to achieve the required thicknesses for the contact layer. Furthermore, it is conceivable that, in addition to the contact layer, the bonding layer also comprises a solder base material layer, which is preferably arranged between the active metal layer and the metallization of the metal layer. For example, this could be a silver-copper solder bond. Alternatively, it is also conceivable to use a silver-free solder base material layer.

[0013] The solder base material layer is preferably characterized in that the proportion of active metal in the solder base material layer is less than 5 wt.%, preferably less than 3 wt.%, and particularly preferably less than 1.5 wt.%. Particularly preferably, the solder base material layer is substantially free of an active metal.

[0014] The carrier substrate is preferably provided as a printed circuit board in which, in the manufactured state, the at least one metal layer which is connected to the insulation element is structured. For example, it is provided for this purpose that after the connection step, structuring is also carried out, for example by lasering, etching and / or mechanical processing, with which conductor tracks and / or connections for electrical or electronic components are created. It is preferably provided that on a manufactured metal-ceramic substrate, on the ceramic element, on the side opposite the metal layer, a further metal layer, in particular a back-side metallization and / or a cooling element, is provided. The back-side metallization preferably serves to counteract bending and the cooling element serves to effectively dissipate heat which is generated during operation of electrical or electronic components.electronic components that are connected to the circuit board or the metal-ceramic substrate.

[0015] Conceivable materials for the at least one metal layer and / or the at least one further metal layer in the metal-ceramic substrate or insulation element include copper, aluminum, molybdenum, tungsten, nickel, and / or their alloys, such as CuZr, AlSi, or AlMgSi, as well as laminates such as CuW, CuMo, CuAl, and / or AlCu, or MMC (metal matrix composite), such as CuW, CuM, or AlSiC. Furthermore, it is preferably provided that the at least one metal layer on the manufactured metal-ceramic substrate is surface-modified, in particular as component metallization. A possible surface modification could, for example, be a sealing with a precious metal, in particular silver and / or gold, or (electroless) nickel or EN IG ("electroless nickel immersion gold"), or edge encapsulation on the metallization to suppress crack formation or crack widening.

[0016] The insulating element is particularly preferably a nitride-containing and / or silicon-containing ceramic element. The ceramic element preferably comprises Al2O3, SiSn4, AlN, an HPSX ceramic (i.e., a ceramic with an Al2O3 matrix comprising an x-percent proportion of ZrO2, for example Al2O3 with 9% ZrO2 = HPS9 or Al2O3 with 25% ZrO2 = HPS25), SiC, BeO, MgO, high-density MgO (> 90% of the theoretical density), TSZ (tetragonally stabilized zirconium oxide) as the material for the ceramic. It is also conceivable for the ceramic element to be designed as a composite or hybrid ceramic, in which, in order to combine various desired properties, several ceramic layers, each differing in terms of their material composition, are arranged one above the other and joined together to form an insulating element. The bonding layer is preferably flat, in particular without interruption, i.e.continuous, formed between the at least one metal layer and the ceramic element.

[0017] It is preferably provided that a second thickness of the bonding layer measured in the stacking direction, determined over a plurality of measuring points within one or more of the predetermined areas which run or run parallel to the main extent, assumes a value which is less than 20 pm, preferably less than 10 pm and particularly preferably less than 6 pm. This also makes it possible to produce bonding layers which are significantly thinner than the bonding layers usually used. This also simplifies detachment of the bonding layer in those regions in which, after the metal layer has been bonded to the insulation element, areas have to be removed again in order to structure the metal layer. Irrespective of this, the thermal resistance emanating from the entire bonding layer is also reduced if the second thickness is reduced.

[0018] Furthermore, it is provided that the carrier substrate comprises at least one further metal layer, which is bonded to the insulation element on a side opposite the at least one metal layer, wherein in the manufactured carrier substrate a further bonding layer is formed between the at least one further metal layer and the insulation element, wherein a third thickness of the bonding layer and the further bonding layer, measured in the stacking direction and summed up over several measuring points within the area which runs parallel to the main extension plane, assumes a value which is less than 40 pm, preferably less than 12 pm mm and particularly preferably less than 12 pm

[0019] It is particularly preferred if the bonding layer is essentially pore-free. This can be achieved, in particular, by exerting additional pressure on the bonding layer during the bonding process. As a result, the bonding layer is essentially pore-free, which also has a positive effect on the thermal conductivity of the system, in particular on the thermal conductivity of the bonding layer.

[0020] Preferably, the bonding layer is free of a solder base material. In particular, it is preferred if the bonding layer is formed or consists exclusively of the contact layer. As a result, the thermal resistance of the entire bonding layer is limited to the comparatively thin contact layer. This also proves particularly advantageous for the thermal conductivity of the entire system comprising the insulation element, bonding layer, and at least one metal layer.

[0021] Preferably, the contact layer also comprises silver; this silver is, for example, the result of diffusion from the solder base material layer. Preferably, the thermal conductivity of the carrier substrate is greater than 60 W / mK, preferably greater than 70 W / mK, and particularly preferably greater than 90 W / mK.

[0022] Preferably, the ratio of the first thickness to the second thickness assumes a value that is less than 0.1, preferably less than 0.08, and particularly less than 0.05. This results in a comparatively thin contact layer, particularly in relation to the total thickness of the bonding layer, which also has a beneficial effect on the thermal conductivity of the entire system.

[0023] A further subject of the present invention is a method for producing a carrier substrate, in particular a metal-ceramic substrate, according to the present invention, comprising:

[0024] Providing at least one metal layer and one insulating element, in particular a ceramic element, a glass element, a glass-ceramic element and / or a high-temperature-resistant plastic element, wherein the at least one metal layer and the insulating element extend along a main extension plane,

[0025] - arranging the at least one metal layer and the insulation element one above the other in a stacking direction running perpendicular to the main extension plane, wherein an active metal layer is arranged between the at least one metal layer and the insulation element and

[0026] - Bonding the at least one metal layer to the insulating element via the active metal layer to form a bonding layer between the at least one metal layer and the insulating element.

[0027] All advantages and properties described for the carrier substrate can be transferred or analogously transferred to the process and vice versa. Preferably, the active metal layer is realized by chemical or electrochemical deposition and / or gas-physical vapor deposition (PVD) of an active metal. The active metal layer can be formed on the insulation element, the solder base material, and / or the at least one metal layer. Alternatively or additionally, it is conceivable for the active metal layer to be provided as a separate foil or as a foil that is provided in combination with the solder base material layer and / or a solder foil and / or with the at least one metal layer.

[0028] In particular, the use of a separately applied active metal layer makes it possible to make it comparatively thin, thereby achieving the claimed comparatively thin thicknesses of the bonding layer, particularly averaged over various thickness values ​​within the specified area(s). Examples of active metals are titanium (Ti), zirconium (Zr), hafnium (Hf), chromium (Cr), niobium (Nb), cerium (Ce), tantalum (Ta), magnesium (Mg), lanthanum (La), and vanadium (V). It should be noted that the metals La, Ce, Ca, and Mg are easily oxidized or can oxidize completely. Furthermore, it should be noted that the elements Cr, Mo, and W are not classic active metals, but are suitable as a contact layer between SiSn4 and the at least one metal layer or the solder system or solder material, since they do not form intermetallic phases with the at least one metal layer, for example, copper, and do not exhibit edge solubility.It has been found that the separately applied active metal layer allows the comparatively thin contact layers to be precisely adjusted in a process-safe and comparatively simple manner.

[0029] In particular, the active metal layer has a proportion of active metal which is greater than 15 wt. %, particularly preferably greater than 20 wt. % and particularly preferably greater than 50 wt. %.

[0030] In particular, the solder base material is a metal-based base material, preferably a silver-based or copper-based base material. In a silver-based base material, silver is the main component, i.e., the component with the highest proportion by weight, whereas in a copper-based base material, copper is the main component. Examples of a silver-based base material are AgCu, in particular AgCu28, AgCuln, AgCuSn, and AgCuGa. Examples of a copper-based base material are copper CuSn, CuAg, Culn, CuGa, CulnSn, CuInMn, and CuGaSn. It is also conceivable to use a solder base material based on NiCrMn or SnCu.

[0031] Preferably, the active metal layer contains a proportion of non-metallic impurities of less than 0.1 wt. %, preferably less than 0.05 wt. %, and particularly preferably less than 0.01 wt. %. By minimizing impurities, it is advantageously possible to make the layer thickness smaller, since in the event of contamination, only a portion of the active metal present can contribute to bonding the at least one metal layer to the insulating element, while the remainder of the active metal is bound by the impurities. By ensuring a comparatively low proportion of impurities, a more effective bond is achieved, which allows the proportion of active metal to be reduced, which in turn allows the bonding layer to be made thinner.

[0032] Preferably, the thermal resistance of the carrier substrate is adjusted via the first thickness. This allows the thermal resistance of the metal-ceramic substrate to be specifically adapted to the requirements of the respective application.

[0033] Furthermore, it is preferably provided that physical and / or chemical vapor deposition or electrochemical deposition is carried out in such a way that a density of the active metal applied to the insulation element is achieved which is greater than 90% of a theoretical density of the active metal, preferably greater than 95% of the theoretical density and particularly preferably greater than 99% of the theoretical density. The theoretical density of the active metal is understood by those skilled in the art to mean in particular the density which can be found in a data sheet for the active metal without artificial cavities or pores being introduced into the active metal. In particular, the comparatively high densities prevent oxygen, nitrogen and / or carbon from being present in the active metal layer during binding, which in turn could lead to undesired binding of the active metal as an impurity.Accordingly, the increased density in the active metal layer increases the proportion that can be effectively used for the connection between the at least one metal layer and the ceramic element, which in turn leads to the active metal layer itself being able to be made thinner. Preferably, an active metal layer is used whose thickness is between 10 nm and 1000 nm, preferably between 50 nm and 750 nm, particularly preferably between 100 and 500 nm. Furthermore, it is preferably provided that the active metal is applied to the insulation element and / or the solder base material, which is preferably also in the form of a foil, by means of physical and / or chemical vapor deposition.For example, it is also conceivable that the active metal is rolled down to the desired thickness together with the solder material in order to form a comparatively thin bonding layer between the at least one metal layer and the insulation element.

[0034] Preferably, a solder foil is used that is smaller than 20 pm, preferably smaller than 12 pm, and particularly preferably smaller than 8 pm. For example, the thickness of the solder layer assumes a value between 2 and 20 pm or between 2 and 5 pm, preferably between 8 and 15 pm, and particularly preferably between 5 and 10 pm. Furthermore, it is conceivable that the solder base material is provided as a foil, as a paste, as a layer formed by physical and / or chemical deposition, and / or as a galvanically formed layer.

[0035] Furthermore, it is preferably provided that a roughness R aa surface of the insulation element is at least partially smaller than 1.0 pm, preferably smaller than 0.7 pm and particularly preferably smaller than 0.5 pm. By reducing the roughness on the surface of the insulation element, it is advantageously possible to avoid air pockets or hollow areas in which oxygen can accumulate, which in turn would be detrimental to the effective use of the active metal for bonding the at least one metal layer to the insulation element in the sense of contamination. In particular, a mean roughness is assumed. The mean roughness value, represented by the symbol R a , indicates the average distance of a measuring point on the surface from a center line. The center line intersects the actual profile within a reference distance such that the sum of the profile deviations in a plane parallel to the center line is distributed over the length of the reference distance.

[0036] It is also conceivable that the roughness R aa surface of the insulation element is at least partially greater than 1.0 pm, preferably between 0.4 pm and 1.5 pm and particularly preferably between 0.75 and 1.25 pm. In particular, it has been found that with increasing roughness the sheet resistance also increases. Furthermore, it has been found that it is possible to design the outermost edge of the at least one metal layer, in particular on the side facing the insulation element, in such a way that it is less prone to fraying. While it is common for a frayed outermost edge to form in the methods known from the prior art, it is possible to suppress this fraying.The side length of the at least one metal layer in the edge region is preferably determined as the extension between an upper edge of the at least one metal layer on the side facing away from the insulation element and a lower edge that delimits the metal layer on the side facing the insulation element at the outermost circumference. A material bonding agent, such as a solder material or its residues, is assigned to the lower edge of the at least one metal layer. When structuring the at least one metal layer, it is common practice in the prior art for the lower edge not to run in a straight line along a circumferential direction around a metal section created by the structuring, resulting in a fringe-like shape.This results in the length of the at least one metal layer between the upper edge and the lower edge, measured in a direction parallel to the main extension plane, varying along the circumferential direction. This corresponds to the fringe formation at the outermost periphery of the at least one metal layer. The lengths of the outermost edge, measured between the upper edge and the lower edge of the at least one metal layer, are stochastically distributed.

[0037] It has been found that it is possible to limit this variation in the length of the outermost edge of the at least one metal layer. In particular, it is provided that a standard deviation of a length of the outermost edge region of the at least one metal layer, measured between an upper and lower edge of the at least one metal layer in a direction running parallel to the main extension plane, assumes a value of less than 0.4, preferably less than 0.2, and particularly preferably less than 0.1. Due to the lower scatter with regard to the length of the at least one metal layer in the edge region, it is advantageously possible to realize adjacent metal sections closer to one another, taking into account any manufacturing tolerances. This supports the formation of circuit boards that are as compact as possible.

[0038] Furthermore, it is preferably provided that the at least one metal layer and / or the at least one further metal layer is bonded to the insulation element by means of an active soldering process and / or hot isostatic pressing. For example, it is provided that a method for producing a metal-ceramic substrate is provided, comprising:

[0039] - Providing a soldering layer, in particular in the form of at least one soldering foil or brazing foil,

[0040] - coating the insulation element and / or the at least one metal layer and / or the at least one solder layer with at least one active metal layer,

[0041] - Arranging the at least one solder layer between the insulation element and the at least one metal layer along a stacking direction to form a solder system comprising the at least one solder layer and the at least one active metal layer, wherein a solder material of the at least one solder layer is preferably free of a melting point-lowering material or of a phosphorus-free material, and

[0042] - Bonding the at least one metal layer to the at least one ceramic layer via the soldering system by means of an active soldering process.

[0043] In particular, a multi-layer soldering system is provided comprising at least one solder layer, preferably free of melting point-lowering elements, particularly preferably a phosphorus-free solder layer, and at least one active metal layer. The separation of the at least one active metal layer and the at least one solder layer proves to be particularly advantageous because it allows for the realization of comparatively thin solder layers, especially when the solder layer is a foil. For solder materials containing active metals, comparatively large solder layer thicknesses are otherwise required due to the brittle intermetallic phases or the high modulus of elasticity and high yield strength of the common active metals and their intermetallic

[0044] Phases that hinder the forming of the solder paste or solder layer are realized, whereby the minimum layer thickness is limited by the manufacturing properties of the active metal-containing solder material. Accordingly, for solder layers containing active metals, it is not the minimum thickness required for the joining process that determines the minimum solder layer thickness, but rather the technically feasible minimum layer thickness of the solder layer. As a result, this thicker, active metal-containing solder layer is more expensive than thin layers. The term phosphorus-free is understood by those skilled in the art to mean, in particular, that the proportion of phosphorus in the solder layer is less than 150 ppm, less than 100 ppm, and particularly preferably less than 50 ppm. The solder layer, in particular the phosphorus-free solder layer, preferably comprises several materials in addition to the pure metal. For example, indium is a component of the solder material used in the solder layer.

[0045] Furthermore, it is conceivable that the solder material for forming the solder layer is applied to the active metal layer and / or the at least one metal layer by physical and / or chemical vapor deposition and / or galvanically. This advantageously makes it possible to realize comparatively thin solder layers in the soldering system, particularly with a homogeneous distribution.

[0046] For example, in the production of the carrier substrate, in particular the metal-ceramic substrate, further steps are provided, comprising:

[0047] - Providing a ceramic element and a metal layer,

[0048] - providing a gas-tight container enclosing the ceramic element, wherein the container is preferably formed from the metal layer or comprises the metal layer,

[0049] - Forming the metal-ceramic substrate by bonding the metal layer to the ceramic element by means of hot isostatic pressing, wherein, to form the metal-ceramic substrate, an active metal layer or a contact layer comprising an active metal is arranged at least partially between the metal layer and the ceramic element to support the bonding of the metal layer to the ceramic element. The container is preferably formed as a metal container made of a metal layer and / or another metal layer. Alternatively, it is also conceivable to use a glass container.

[0050] In hot isostatic pressing, it is particularly intended that bonding occurs by heating under pressure, during which the first and / or second metal layer of the metal container, in particular the subsequent metal layer of the metal-ceramic substrate and any eutectic layer present there, does not enter the melting phase. Accordingly, lower temperatures are required for hot isostatic pressing than for a direct metal bonding process, in particular a DGB process.

[0051] In comparison to the bonding of a metal layer to a ceramic layer by means of a solder material, which usually requires temperatures below the melting temperature of the at least one metal layer, the present procedure advantageously makes it possible to dispense with a solder base material and only requires an active metal. The use or utilization of pressure during hot isostatic pressing also proves advantageous because it can reduce air inclusions or cavities between the first metal layer and / or the second metal layer on the one hand and the ceramic element on the other, whereby the frequency of formation of shrinkage cavities in the formed or manufactured metal-ceramic substrate can be reduced or even avoided. This has a beneficial effect on the quality of the bond between the metal layer or the first and / or second metal layer of the metal container and the ceramic element.In addition, it is advantageously possible to simplify the “second etching” and avoid solder residues and silver migration.

[0052] It is also conceivable that during hot isostatic pressing an additional solder material is introduced between the ceramic element and the at least one metal layer, wherein a melting temperature of the additional solder material can be lower than the temperature at which the hot isostatic pressing is carried out, ie lower than the melting temperature of the at least one metal layer.

[0053] It is preferably provided that during hot isostatic pressing, the metal container is exposed in a heating and pressure device to a gas pressure between 100 and 2000 bar, preferably between 150 and 1200 bar and particularly preferably between 300 and 1000 bar and a process temperature of 300°C up to a melting temperature of the at least one metal layer, in particular up to a temperature below the melting temperature. It has advantageously been found that it is thus possible to bond a metal layer, i.e. a first and / or second metal layer of the metal container, to the ceramic element without the required temperatures of a direct metal bonding process, for example a DCB or a DAB process, and / or without a solder base material that is used in active soldering. In addition, the use or application of an appropriate gas pressure allows the possibility of producing a process that is as void-free as possible, i.e.to produce a metal-ceramic substrate without gas inclusions between the metal layer and the ceramic element. In particular, process parameters mentioned in DE 2013 113 734 A1 are used, and are hereby explicitly incorporated by reference. Further advantages and properties will become apparent from the following description of preferred embodiments of the subject matter according to the invention with reference to the attached figures. They show:

[0054] Fig. 1 : Carrier substrate 1 according to a first exemplary embodiment of the present invention;

[0055] Fig. 2: schematic and real representation of bonding layers and

[0056] Fig. 3: Measuring arrangement for determining the thermal conductivity

[0057] Figure 1 shows a carrier substrate 1 according to a first exemplary embodiment of the present invention. Such carrier substrates 1, in particular in the form of a metal-ceramic substrate, preferably serve as carriers or printed circuit boards for electronic or electrical components that can be bonded to the at least one metal layer 10 of the carrier substrate 1 on its component side. It is preferably provided that the at least one metal layer 10 is structured in order to form corresponding conductor tracks and / or connection surfaces, i.e., in the manufactured carrier substrate 1, the at least one metal layer 10 comprises a plurality of metal sections that are electrically insulated from one another.The at least one metal layer 10, which extends essentially along a main extension plane HSE, and an insulation element 30 extending along the main extension plane HSE are arranged one above the other along a stacking direction S running perpendicular to the main extension plane HSE and are preferably joined or connected to one another via a bonding layer 12. Preferably, the carrier substrate 1 comprises, in addition to the at least one metal layer 10, at least one further metal layer 20, which, viewed in the stacking direction S, is arranged on the side of the insulation element 30 opposite the at least one metal layer 10 and is bonded to the insulation element 30 via a further bonding layer 12'.

[0058] The at least one further metal layer 20 serves as a backside metallization, which counteracts a bending of the carrier substrate 1, in particular the metal-ceramic substrate, and / or as a heat sink, which is designed to dissipate heat input caused by electrical or electronic components on the metal-ceramic substrate 1.

[0059] In particular, in the exemplary embodiment shown in Figure 1, it is provided that the bonding layer 12 comprises a contact layer 13. Thus, the bonding layers 12 are preferably composed at least, and in particular exclusively, of the contact layer 13 and a solder base material layer 17. The solder base material layer 17 is, for example, derived from a solder base material and differs, for example, from the material composition in the at least one metal layer 10. For example, the solder base material in the solder base material layer 17 is a silver-copper mixture. The contact layer 13 preferably comprises a titanium-nitrogen compound and / or a titanium-silicon compound. For example, this is titanium nitride or a titanium-silicon compound with different stoichiometric compositions.

[0060] In particular, it is provided that the contact layer 13 has a first thickness D1 in a direction measured parallel to the stacking direction S. This first thickness D1 is preferably less than 900 nm, more preferably less than 700 nm, and particularly preferably less than 500 nm. It has been found that with such thin contact layers 13, it is possible to significantly reduce the thermal resistance emanating from this contact layer 13, in particular compared to the contact layers 13 that arise as part of a conventional connection to the insulation element 30, in particular a ceramic element, and which are significantly larger than 1,000 nm and typically in the range of 1,500 nm.

[0061] In the embodiment illustrated in Figure 1, the at least one further metal layer 20 is also bonded to the insulation element 30, in particular to the silicon nitride ceramic, via a bonding layer 12. This bonding layer 12 is also composed of a contact layer 13 and a solder base material layer 17, wherein the contact layer 13 comprises titanium-nitrogen compounds and / or titanium-silicon compounds and has a first thickness D1 that is less than 900 nm. However, it is also conceivable that the contact layer 13 for the rear-side metallization or the at least one further metal layer 20 is dimensioned differently than that for the component metallization or the at least one metal layer 10.It is further conceivable that the ratio between the first thickness D1 and a second thickness D2 in the bonding layer 12 is different for the at least one metal layer 10 and the at least one further metal layer 20. However, it proves advantageous if the contact layers 13 for component metallization and backside metallization are both smaller than 900 nm, preferably smaller than 700 nm, and particularly preferably smaller than 500 nm, since the heat generated at the component metallization must be transported to the underside of the backside metallization in order to be dissipated via a cooling element. Therefore, the formation of equally thin contact layers 13 for the component metallization and backside metallization proves advantageous for the entire carrier substrate 1.

[0062] Furthermore, it is preferably provided that a ratio of the first thickness D1 to the second thickness D2 assumes a value that is less than 0.1, preferably less than 0.08, and particularly preferably less than 0.05. The contact layer 13 is thus significantly thinner than the solder base material layer 17.

[0063] Furthermore, it is conceivable that the contact layer 13 comprises silver. This is silver that has diffused from the solder base material into the contact layer 13 during the bonding process. Furthermore, the titanium-nitrogen and titanium-silicon compounds are results of the bonding process, in which an active metal layer, in particular a separate active metal layer, is used during the bonding process and the active metal, in particular titanium, reacts with components of the insulation element 30, in particular in the case of nitride ceramics, in particular silicon nitride, to create the titanium-nitrogen and / or the titanium-silicon compounds.

[0064] Figure 2 shows various bonding layers 12 in detail. On the left-hand side, a system is shown that visualizes a bonding layer 12 composed of a comparatively thin contact layer 13 and a solder base material layer 17. The section is limited to the component metallization, i.e. the at least one metal layer 10, and the insulation element 30, as well as the bonding layer 12 located therebetween. While the upper illustration shows a schematic representation of the individual layers, the lower half of the image shows a microscopic image of a real bonding layer 12. In the middle, a system is shown in which the bonding layer 12 is produced according to a conventional method. Here, the contact layer 13 assumes a first thickness D1 of approximately 1,500 nm.The solder base material layer 17 is also thicker than the solder base material layer 17 in the embodiment on the left. The right side shows a system in which the at least one Meta II layer 10 is bonded to the insulation element 30 exclusively via a contact layer 13, wherein the contact layer 13 is formed exclusively from titanium. This contact layer 13 is larger than the bonding layer 12 in the two embodiments in the middle and on the left.

[0065] Figure 3 shows how the thermal conductivity is measured for a system composed of the bonding layers 12, the insulation element 30, as well as the at least one metal layer 10 and the at least one further metal layer 20.

[0066] Based on the knowledge of the thermal conductivity of the at least one metal layer 10 and the at least one further metal layer 20, it is possible to specify a thermal conductivity for the system comprising bonding layers 12 and insulation element. It has been found that when using a contact layer 13 that comprises a titanium-nitrogen compound and / or titanium-silicon compound and that has a first thickness D1 that is less than 900 nm, preferably less than 700 nm, and particularly preferably less than 500 nm, a significant improvement in thermal conductivity can be achieved, in particular by up to 10%.

[0067] For this purpose, measurements were carried out in which two different silicon nitride ceramics were used as insulation elements. The two insulation elements came from different suppliers. While in one carrier substrate 1, a contact layer 13 was realized for each silicon nitride ceramic from the different suppliers, which had a first thickness D1 of less than 900 nm, a carrier substrate 1 was created for comparison in which the contact layer 13 for the same silicon nitride ceramics from the different suppliers was larger and assumed values ​​of around 1,500 nm, for example. The measurements showed that for the contact layers 13 with a first thickness D1 greater than 1,000 nm, the conductivities were between 60 and 66 mm 2 / s, while the conductivities for the thinner contact layers 13, especially thinner layers with first thicknesses D1 less than 900 nm, were between 72 and 78 mm 2 / s. 0.8 mm thick copper layers were used as the first and second metal layers, respectively. It can thus be seen that with the correspondingly thin contact layers 13, it is advantageously possible to significantly increase the thermal conductivity or reduce the thermal resistance. List of reference symbols:

[0068] 1 carrier substrate

[0069] 10 metal layer

[0070] 12 binding layer

[0071] 13 Contact layer

[0072] 17 Solder base material layer

[0073] 20 additional metal layers

[0074] D1 first thickness

[0075] D2 second thickness

[0076] HSE main extension level

[0077] S Stacking direction

Claims

Claims 1. Carrier substrate (1), in particular a metal-ceramic substrate, as a carrier for electrical components in the form of a printed circuit board, comprising: - at least one metal layer (10) and - an insulation element (30), in particular a ceramic element, a glass element, a glass-ceramic element and / or a high-temperature-resistant plastic element, wherein the at least one metal layer (10) and the insulation element (30) extend along a main extension plane (HSE) and are arranged one above the other along a stacking direction (S) running perpendicular to the main extension plane (HSE), wherein a bonding layer (12) is formed between the at least one metal layer (10) and the insulation element (30) in the manufactured carrier substrate (1), and wherein a contact layer (13) of the bonding layer (12) has a first thickness (D1) measured in the stacking direction (S), averaged over a plurality of measuring points within one or more predetermined areas (F) which run or run parallel to the main extension plane (HSE), which is less than 900 nm, preferably less than 700 nm and preferably less than 500 nm or even less than 350 nm.

2. Carrier substrate according to claim 1, wherein the contact layer (13) comprises a titanium-nitrogen compound.

3. Carrier substrate (1) according to one of the preceding claims, wherein the contact layer (13) comprises a titanium-silicon compound.

4. Carrier substrate (1) according to one of the preceding claims, wherein titanium-nitrogen compounds and titanium-silicon compounds are formed in different stoichiometric compounds.

5. Carrier substrate (1) according to one of the preceding claims, wherein in addition to the contact layer (13), the bonding layer (12) comprises a solder base material layer, which is preferably arranged between the active metal layer (15) and the metallization of the metal layer (10).

6. Carrier substrate (1) according to one of the preceding claims, wherein a second thickness (D2) of the bonding layer (12) measured in the stacking direction (S), averaged over several measuring points within one or more predetermined areas (F) which run or run parallel to the main extension plane (HSE), assumes a value which is less than 20 pm, preferably less than 10 pm and particularly preferably less than 6 pm.

7. Carrier substrate (1) according to one of the preceding claims, wherein a ratio of the first thickness (D1) to the second thickness (D2) assumes a value which is less than 0.1, preferably less than 0.08 and particularly less than 0.

05.

8. Carrier substrate (1) according to one of the preceding claims, wherein the contact layer (13) comprises silver.

9. Carrier substrate (1) according to one of the preceding claims, wherein the thermal conductivity of the carrier substrate (1) is greater than 60 W / mK, preferably greater than 70 W / mK and particularly preferably greater than 90 W / mK.

10. A method for producing a carrier substrate (1), in particular a metal-ceramic substrate, according to one of the preceding claims, comprising: - Providing at least one metal layer (10) and one insulating element (30), in particular a ceramic element (30), a glass element, a glass-ceramic element and / or a high-temperature-resistant plastic element, wherein the at least one metal layer (10) and the insulating element (30) extend along a main extension plane (HSE), - arranging the at least one metal layer (10) and the insulation element (30) one above the other in a stacking direction (S) running perpendicular to the main extension plane (HSE), wherein an active metal layer (15) is arranged between the at least one metal layer (10) and the insulation element (30), and - Bonding the at least one metal layer (10) to the insulation element (30) via the active metal layer (15) to form a bonding layer (12) between the at least one metal layer (10) and the insulation element (30).

11. Method according to one of the preceding claims, wherein the thermal resistance of the carrier substrate (1) is adjusted via the first thickness (D1).

12. The method according to claim 10 or 11, wherein a proportion of impurities in the arranged active metal layer (15) is less than 5 wt.%, preferably less than 3 wt.% and particularly preferably less than 1.5 wt.%.

13. The method according to any one of claims 8 to 12, wherein a proportion of impurities of non-metallic impurities in the arranged active metal layer (15) is less than 0.1 wt.%, preferably less than 0.05 wt.% and particularly preferably less than 0.01 wt.%.

14. The method according to any one of claims 10 to 13, wherein a proportion of active metal in the contact layer (13) comprising an active metal is greater than 15% by weight, preferably greater than 20% by weight and particularly preferably greater than 25% by weight. 15 Method according to one of claims 9 to 14, wherein a multi-layer soldering system is provided comprising at least one soldering layer, preferably free of melting point lowering elements, particularly preferably a phosphorus-free soldering layer, and at least one active metal layer.

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