Metal ceramic substrate and method of manufacturing the same

Abstract

A metal ceramic substrate usable as a printed circuit board, comprising a ceramic element and at least one component metallization bonded to the ceramic element, the at least one component metallization being structured to form conductor paths, the ceramic element comprising magnesium oxide, the proportion of magnesium oxide being greater than 60% by weight, preferably greater than 80% by weight, more preferably greater than 95% by weight.

Description

[Technical Field]

[0001] The present invention relates to a metal-ceramic substrate and a method for manufacturing the same. [Background technology]

[0002] Metal-ceramic substrates are well known in the prior art as printed circuit boards or circuit boards (see, for example, U.S. Pat. Nos. 5,629,999, 5,729,963, 5,729,973, and 5,729,973). Typically, connection areas for electrical components and conductor paths are arranged on the metal-ceramic substrate or on one component side of the metal-ceramic substrate, where the electrical components and conductor paths can be interconnected to form an electrical circuit. 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 to be particularly advantageous in power electronics. The conductor paths and / or connection areas of the electrical components can then be realized by structuring the metal layer.

[0003] Based on the prior art, the object of the present invention is to provide a metal-ceramic substrate which is further improved over known metal-ceramic substrates, in particular with regard to the thermal shock resistance of the bond between the metal layer and the ceramic element as well as the dissipation of heat when heat is generated on the component side of the metal-ceramic substrate during operation. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] German Patent Application Publication No. 102013104739 [Patent Document 2] German Patent No. 19927046 [Patent Document 3] German Patent Application Publication No. 102009033029 Summary of the Invention

[0005] The present invention solves this object by a metal-ceramic substrate according to claim 1 and a method for manufacturing a metal-ceramic substrate according to claim 11. Further embodiments are described in the dependent claims and in the present description.

[0006] According to a first aspect of the present invention, there is provided a metal-ceramic substrate usable as a printed circuit board, the metal-ceramic substrate comprising: Ceramic elements; and at least one component metallization bonded to the ceramic element, At least one component metallization is structured to form conductor paths, and the ceramic element comprises magnesium oxide, the proportion of magnesium oxide being greater than 60% by weight, preferably greater than 80% by weight, and more preferably greater than 95% by weight.

[0007] Compared to metal-ceramic substrates known from the prior art, the present metal-ceramic substrate uses a ceramic element with a relatively high magnesium oxide content. In particular, the ceramic element is essentially composed exclusively of magnesium oxide. By "composed exclusively of magnesium oxide," those skilled in the art understand a magnesium oxide content, particularly having a value of 95% to 100% by weight. Surprisingly, it has been shown that magnesium oxide can be used to provide a ceramic element with a relatively high thermal conductivity, which positively influences the thermal shock resistance of the formed metal-ceramic substrate. This significantly improves the bonding process of at least one metal layer to the ceramic element and the service life of the metal-ceramic substrate. In particular, the following is provided: at least one metal layer is bonded to the ceramic element, and after the bonding process, conductor paths and / or connection areas are formed as part of the structuring, so that the metal-ceramic substrate can be used as a printed circuit board. The bonded and structured at least one metal layer then forms the component metallization. In particular, the thermal expansion coefficient of magnesium oxide is typically 11×10, which is relatively close to that of copper, so that the difference in thermal expansion coefficients is as small as possible when bonding a copper metal layer to the ceramic element, in particular. 6 1 / K~13×106 It has been shown that the thermal conductivity has a value of 1 / K. This has a positive effect on thermal shock resistance and reduces the formation of thermodynamic stress during temperature changes. This significantly improves the service life of metal-ceramic substrates, especially when used as printed circuit boards. Furthermore, it is preferred that the thermal conductivity has a value greater than 30 W / mK, more preferably 40 to 59 W / mK, and even more preferably 55 to 59 W / mK.

[0008] Furthermore, magnesium oxide has been found to be a relatively inexpensive alternative to aluminum oxide or HPS ceramics while at the same time having a relatively high thermal conductivity. It is preferably provided that the component metallization has a first thickness, and that the backside metallization, which is bonded to the ceramic element on the side opposite the component metallization, has a second thickness. The ceramic element has a third thickness. Preferably, the third thickness has a value between 100 μm and 1000 μm, and the second and / or first thicknesses have values ​​between 200 μm and 800 μm. It is further preferably provided that the second and first thicknesses correspond to each other to compensate for any deviations during the bonding process of the at least one metal layer to the ceramic element. It is also conceivable that the third thickness is smaller than the first and / or second thicknesses.

[0009] It is preferred that the ceramic element containing magnesium oxide be doped with an additional material. In particular, the additional material is selected so as not to impair the thermal conductivity, in particular so that the deviation of the thermal conductivity is less than 50%, preferably less than 25%, and more preferably less than 20% of the thermal conductivity of magnesium oxide. It is preferred that the proportion of the additional material in the ceramic element is less than 10% by weight, in particular less than 5% by weight, and more preferably less than 3% by weight. This is advantageous because the doping can affect the properties of the magnesium oxide, in particular make it possible to further improve them. For example, the additional material can increase the density or strength, thereby further increasing the mechanical stability of the ceramic element. This in turn allows, for example, the ceramic element to be designed thinner.

[0010] Additional materials that contribute to spinel formation, such as Al2O3, and / or reinforcement, such as ZrO2, are contemplated. The ability to bond to copper is preferably improved by additional materials such as copper or a mixture of copper and Al2O3. Due to their grain size and associated strength, CaO and Y2O3 are also preferred additional materials. The use of ZrO2 has been found to be particularly advantageous for the material structure, as this leads to transformation strengthening.

[0011] Magnesium oxide is 3-4g / cm 3 value, preferably 3.1 to 3.8 g / cm 3 and more preferably 3.35 to 3.58 g / cm 3 Preferably, the magnesium oxide has a density having a value of 0.05 wt %, where 0.05 wt % is the density present in the formed metal-ceramic substrate. This provides a relatively dense magnesium oxide having advantageously high thermal conductivity.

[0012] It is preferably provided that the ceramic element comprises a coating (in particular a ceramic coating, preferably an aluminum oxide coating) arranged between the ceramic element and the component metallization. This has been found to be particularly advantageous during the bonding process, since the realized ceramic coating acts as an additional bonding agent and helps to solidify the surface, in particular via spinel (magnesium aluminum oxide) formation.

[0013] The material of the at least one metal layer or component metallization in the metal-ceramic substrate may be 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 MMCs (metal matrix composites), such as CuW, CuM, or AlSiC. It is further advantageously provided that the at least one metal layer on the metal-ceramic substrate, especially formed as a component metallization, is surface-modified. Examples of surface modifications include sealing with noble metals (especially silver); and / or gold, or (electroless) nickel, or ENIG (electroless nickel immersion gold), or edge encapsulation on the metallization to prevent crack formation or propagation.

[0014] According to a preferred embodiment of the present invention, it is provided that in the formed metal ceramic substrate, a bonding layer is formed between the component metallization and the ceramic element, and the adhesive layer of the bonding layer has a sheet resistance greater than 0.5 Ω / □, preferably greater than 1 Ω / □, more preferably greater than 2 Ω / □ or even greater than 15 Ω / □.

[0015] The sheet resistance is directly related to the proportion of active metal in the bonding agent layer, which is crucial for bonding at least one metal layer to the ceramic element. The sheet resistance increases with decreasing active metal content in the bonding layer. Therefore, a correspondingly high sheet resistance corresponds to a low active metal content in the bonding agent layer.

[0016] The sheet resistance does not depend on a single parameter, but can be influenced by the interaction of several parameters. For example, the purity of the active metal, the thickness of the bonding layer, and / or the surface roughness of the ceramic element also contribute to determining the sheet resistance. In particular, a high sheet resistance can be achieved only through the interaction of at least two parameters.

[0017] It has been shown that an increased proportion of active metal promotes the formation of brittle intermetallic phases, which is therefore detrimental to the pull-off strength of the metal layer on the insulating layer. In other words, the claimed sheet resistance describes such a bonding layer, whose pull-off strength is improved or increased due to the reduced formation of brittle intermetallic phases. By specifically adjusting the sheet resistance as claimed, particularly strong bonding of at least one metal layer to the ceramic element can be achieved. Such increased bonding strength has a beneficial effect on the service life of the metal-ceramic substrate. To determine the sheet resistance, it is provided that the metal layer and, if necessary, the solder-based layer are removed from the formed metal-ceramic substrate, for example, by etching. The sheet resistance is then measured by a four-point measurement on the outer or bottom side of the metal-ceramic substrate freed from the at least one metal layer and the solder-based layer. In particular, the sheet resistance of a material sample is understood to be its resistance per square surface area. It is customary to specify the surface resistance in Ω / □ (square). The physical unit of sheet resistance is the ohm. It is preferably provided that the thickness of the bonding layer measured in the stacking direction, averaged over multiple measurement points in a given area or in multiple areas running parallel to the main extension plane, has a value of less than 0.20 mm, preferably less than 10 μm, and more preferably less than 20 μm. When multiple areas are referred to, this means in particular that the at least one metal layer is divided into areas of as equal size as possible and that at least one value of thickness (preferably several measurements) is recorded in each of these areas dividing the at least one metal layer. The thicknesses determined in this way at various locations are arithmetically averaged.

[0018] In comparison with metal-ceramic substrates known from the prior art, a relatively thin bonding layer is thus formed between at least one metal layer and the ceramic element. The following is provided: To determine the relative thickness of the bonding layer, the measured thickness is averaged over multiple measurement points located within a predetermined or defined area or areas. This advantageously takes into account the fact that ceramic elements are typically subject to waviness (i.e., the ceramic element is somewhat corrugated). In particular, those skilled in the art will understand that waviness is a modulation of the generally flat course of the ceramic element that can be seen over a few millimeters or centimeters along a direction running parallel to the main extension plane. This distinguishes such waviness from the surface roughness of the ceramic element, which is typically additionally present on the ceramic element. By including such waviness of the ceramic element (which is usually unavoidable) in the thickness determination, it is taken into account that the bonding layer may vary due to waviness, which may be greater, in particular, in the valley areas of the ceramic element than in the peak areas of the ceramic element.

[0019] Preferably, the proportion of active metal in the active metal-containing bonding agent layer is greater than 25% by weight, preferably greater than 20% by weight, more preferably greater than 15% by weight. Preferably, the bonding layer is formed flatly, without any discontinuities (i.e., continuously) between the at least one metal layer and the ceramic element. It is preferably provided that the ratio of the area where no bonding layer is formed between the at least one metal layer and the ceramic element to the area where a bonding layer is formed between the at least one bonding layer and the ceramic element is less than 0.05 mm, preferably less than 0.02 mm, and even more preferably less than 0.007 mm. Those skilled in the art will particularly understand that "for forming this ratio, areas where there is no metal in the at least one metal layer due to structuring are not taken into account."

[0020] In particular, it is provided that the component metallization is joined by a direct bonding method, or hot isostatic pressing, in which, unlike active soldering processes, the structure is not or only slightly weakened, resulting in a mechanically stable metal-ceramic substrate.

[0021] It is also conceivable for the component metallization to have a thickness of more than 0.4 mm, preferably more than 1.0 mm, and even more preferably more than 1.5 mm, which has the advantage of ensuring sufficient mechanical stability even if the joining process weakens the structure.

[0022] The ceramic element preferably has a thickness of more than 200 μm, preferably more than 300 μm, and even more preferably more than 400 μm, which, in particular in combination with a relatively thick metal layer, makes it possible to provide a mechanically particularly stable metal-ceramic substrate that can be used in many application areas.

[0023] Another subject of the invention is a method for producing a metal-ceramic substrate according to the invention. In particular, there is provided a method for manufacturing a metal-ceramic substrate, in particular a metal-ceramic substrate according to one of the preceding claims, which can be used as a printed circuit board, said method comprising the steps of: providing a ceramic element comprising magnesium oxide and a metal layer; Bonding the metal layer to the ceramic element; and structuring the metal layer to form a component metallization. All advantages and properties described with respect to the metal-ceramic substrate apply equally to the method for manufacturing a metal-ceramic substrate according to the invention (and vice versa). In particular, the method includes providing a ceramic element with an inherent surface roughness and / or forming a surface profile on the exterior of the ceramic element.

[0024] It is further preferably provided that the at least one metal layer and / or the at least one further metal layer is joined to the ceramic element by an active soldering process and / or hot isostatic pressing and / or a DCB process.

[0025] For example, a method for manufacturing a metal ceramic substrate is provided, the method comprising: providing a solder layer, in particular in the form of at least one solder foil or brazing foil; coating the ceramic element and / or at least one metal layer and / or at least one solder layer with at least one active metal layer; - arranging at least one solder layer between the ceramic element and the at least one metal layer along the stacking direction to form a solder system comprising at least one solder layer and at least one active metal layer, the solder material of the at least one solder layer preferably being a material that does not contain a melting point lowering material or that does not contain phosphorus; - joining at least one metal layer to at least one ceramic layer via a solder system by an active soldering process.

[0026] In particular, a multilayer soldering system is provided that includes at least one solder layer (preferably a solder layer that does not contain elements that lower the melting point, and more preferably a solder layer that does not contain phosphorus) and at least one active metal layer. It has been found that the separation of the at least one active metal layer from the at least one solder layer is particularly advantageous (especially if the solder layer is a foil) because it allows a relatively thin solder layer to be formed. For active metal-containing solder materials, a relatively large solder layer thickness would otherwise be necessary due to the brittle intermetallic phases or high elastic modulus and high yield strength of common active metals and their intermetallic phases, which prevent deformation of the solder paste or solder layer and thus limit the minimum layer thickness due to the manufacturing characteristics of solder materials containing active metals. Therefore, 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 thickness of the solder layer, which determines the minimum solder layer thickness. This makes thicker solder layers containing active metals more expensive than thinner layers. The term "phosphorus-free" will be understood by those skilled in the art to particularly mean that the phosphorus content in the solder layer is less than 1000 ppm, preferably less than 500 ppm, and more preferably less than 200 ppm.

[0027] Preferably, the solder layer (especially the phosphorus-free solder layer) contains some material in addition to the pure metal, for example indium is a component of the solder material used in the solder layer. It is also conceivable that the solder material for forming the solder layer is deposited on the active metal layer and / or at least one metal layer by physical and / or chemical vapor deposition and / or electroplating. This advantageously makes it possible to form a relatively thin solder layer in the solder system (in particular with a homogeneous distribution).

[0028] For example, in the manufacture of metal ceramic substrates, in particular metal ceramic substrates, further steps are provided which include: providing a ceramic element and a metal layer; providing an airtight container surrounding the ceramic element, the container preferably being formed from or including a metal layer; Forming a metal-ceramic substrate by joining a metal layer to a ceramic element by hot isostatic pressing, wherein an active metal layer or a contact layer containing an active metal is disposed in at least some sections between the metal layer and the ceramic element to assist in joining the metal layer to the ceramic element to form the metal-ceramic substrate. The container is preferably formed as a metal container from the metal layer and / or another metal layer. Alternatively, a glass container may be used.

[0029] It is specifically provided that in hot isostatic pressing, "the bonding occurs by heating under pressure such that the first and / or second metal layers of the metal container (especially the subsequent metal layer of the metal-ceramic substrate and any eutectic layer formed thereon) do not proceed into a molten phase." Similarly, hot isostatic pressing requires lower temperatures than direct metal bonding methods (especially the DCB method).

[0030] Compared to joining metal layers to ceramic layers using a solder material (which typically involves temperatures below the melting temperature of at least one metal layer), this method has the advantage that no solder substrate is required and only an active metal is needed. The use of pressure in hot isostatic pressing has also been found to be advantageous, since it reduces air pockets or voids between the first and / or second metal layers on the one hand and the ceramic element on the other, thereby reducing or even preventing the occurrence of porosity in the metal-ceramic substrate being formed or produced. This has a beneficial effect on the quality of the bond between the metal layer or first and / or second metal layers of the metal container and the ceramic element. Additionally, it is advantageously possible to simplify the "second etch" and avoid solder residues and silver migration.

[0031] It is also possible that during hot isostatic pressing, additional solder material is introduced between the ceramic element and the at least one metal layer, the melting temperature of the additional solder material being lower than the temperature at which the hot isostatic pressing is carried out (i.e., lower than the melting temperature of the at least one metal layer).

[0032] Preferably, during hot isostatic pressing, the metal container is exposed in a heating / pressure device to a gas pressure of 10 to 200 MPa (100 to 2000 bar), preferably 15 to 120 MPa (150 to 1200 bar), and more preferably 30 to 100 MPa (300 to 1000 bar), and a processing temperature of 300°C to the smelting temperature of at least one metal layer (particularly a temperature below the smelting temperature). It has thus been shown to be advantageous to bond a metal layer (i.e., the first and / or second metal layer of the metal container) to a ceramic element without the temperatures required for direct metal bonding methods (e.g., DCB or DAB methods) and / or without the solder substrate used in active soldering. In addition, the use or utilization of an appropriate gas pressure makes it possible to produce a metal-ceramic substrate with as few voids as possible (i.e., no gas inclusions between the metal layer and the ceramic element). In particular, the process parameters described in DE 2013113734 A1 are used, to which explicit reference is made herein.

[0033] It is preferably provided that the metal layers are bonded via an active metal layer. In particular, this is a separate active metal layer, the proportion of which is preferably greater than 15% by weight, very preferably greater than 35% by weight, and even more preferably greater than 80% by weight. Therefore, this is not an active metal-containing solder layer, but rather a bonding or adhesive layer that uses only active metal to achieve bonding between the metal layer and the ceramic element. Alternatively, it is desirable for the active metal layer to be applied as a separate layer in addition to the solder substrate, where the active metal layer and the solder substrate form a solder layer system. In particular, it has been found to be advantageous if the active metal layer is applied and / or used as an active metal foil.

[0034] It is further advantageously provided that this is done under pressure (especially in the context of hot isostatic pressing), so that the density of the magnesium oxide content in the ceramic element is also advantageously increased. For example, it is possible to increase the theoretical density of the magnesium oxide by 20%. The density values ​​of the magnesium oxide are compared before and after hot isostatic pressing. In other words, the binding process also advantageously forms high-density magnesium oxide.

[0035] It is preferably provided that at least one metal layer is bonded by hot isostatic pressing, where in particular the density within the ceramic element is increased by bonding. Alternatively, it is conceivable that at least one metal layer is bonded by a direct bonding method, in which case, for example, the additional ceramic coating preferably surrounds the magnesium-encapsulated ceramic element as bonding agent by more than 75 wt.%, more preferably by more than 85 wt.%, and most preferably by more than 95 wt.%, or even completely.

[0036] Ceramic coatings made of aluminum oxide are particularly advantageous in this regard. Further advantages and features will become apparent from the following description of preferred embodiments of the present invention, which is given with reference to the accompanying drawings. [Brief explanation of the drawings]

[0037] [Figure 1] 1 is a metal-ceramic substrate according to a first exemplary embodiment of the present invention. [Figure 2] 2 is a metal ceramic substrate according to a second exemplary embodiment of the present invention. [Figure 3] 10 is a metal ceramic substrate according to a third exemplary embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0038] 1 shows a metal-ceramic substrate 1 according to a first exemplary embodiment of the present invention. Such a metal-ceramic substrate 1 can suitably serve as a carrier of electronic or electrical components or as a printed circuit board (at least one metal layer of the metal-ceramic substrate 1 can be bonded to the component side to form a component metallization 10). The component metallization 10 is preferably provided to include several metal sections that are structured to form corresponding conductor paths and / or connection areas (not shown) (i.e., in the manufactured metal-ceramic substrate 1) and are electrically insulated from one another. The component metallization 10, which extends essentially along the main extension plane HSE, and the ceramic elements 30, which also extend along the main extension plane HSE, are arranged on top of one another along a stacking direction S running perpendicular to the main extension plane HSE and are preferably linked or connected to one another via a bonding layer 12. Preferably, the metal ceramic substrate 1 includes at least one backside metallization 20 in addition to the component metallization 10, which is arranged on the side of the ceramic element 30 opposite the component metallization 10 in the stacking direction S and is bonded to the ceramic element 30 via another bonding layer 12'.

[0039] At least one further metal layer 20 acts as a backside metallization 20 to compensate for deflection of the metal-ceramic substrate 1 (particularly of the metal / ceramic element 1) and / or as a heat sink designed to dissipate heat input generated by electrical or electronic components on the metal-ceramic substrate 1.

[0040] In particular, the metal-ceramic substrate 1 has a bonding layer 12 arranged between the at least one metal layer 10 and the ceramic element 30. It has been shown to be advantageous if the thickness of the bonding layer 12, measured in the stacking direction S, is relatively small. In addition, it has been found to be advantageous if a relatively small thickness of the bonding layer 12 between the at least one metal layer 10 and the ceramic element 30 is provided for an etching process for structuring the at least one metal layer 10. For example, narrower isolation trenches (i.e. the distance between the individual metal sections of the at least one metal layer 10) can be realized.

[0041] Additionally, it has been found that forming a thinner bonding layer 12 is advantageous in that it also further reduces the number of possible defects in the bonding layer 12 caused by material imperfections in any solder material used.

[0042] In the example shown in FIG. 1 , the bonding layer 12 is in particular a bonding agent layer 13 containing an active metal. In this case, after bonding, the bonding agent layer 13 is preferably formed from a material composition containing a compound of the ceramic element, on the one hand, and the active metal, on the other hand. Because these are very brittle bonds, it is advantageous for the adhesive strength of the at least one metal layer 10 on the ceramic element 30 if this bonding agent layer 13 is as thin as possible. For example, the bonding agent layer 13 can form the bonding layer 12 if, for example, an active metal layer (in particular, an active metal foil) is arranged for the bonding process between the ceramic element 30 and the metal layer 10, and the bonding process occurs via hot isostatic pressing. However, the bonding agent layer 13 can also be formed by, for example, an active metal layer (in particular, an active metal foil) arranged between the ceramic element 30 and the solder-based layer to form a bond between the metal layer 10 and the ceramic element 30 via a system consisting of the active metal layer and the solder-based layer. In this case, the bonding agent layer 13 forms part of the bonding layer 12.

[0043] The active metal layer preferably has an active metal content of greater than 15 wt. %, preferably greater than 35 wt. %, and even more preferably greater than 80 wt. Therefore, it is not an active metal-containing solder layer used to join at least one metal layer. It is further preferred that only one active metal layer be disposed between the ceramic element 30 and the at least one metal layer when the joining process occurs.

[0044] In other words, for example, a solder-based layer additionally arranged between the ceramic element and the at least one metal layer can be dispensed with if a soldering process is performed to form the component metallization 10. In particular, it is provided that after bonding of the at least one metal layer to form the component metallization 10, this at least one metal layer is structured (i.e., insulating trenches are introduced) to electrically separate the individual metal sections of the component metallization 10 from one another.

[0045] It has been found that the use of magnesium oxide as the ceramic element 30 is particularly advantageous. The magnesium oxide content is preferably greater than 60% by weight, more preferably greater than 80% by weight, and even more preferably greater than 95% by weight. As a result, it is advantageous to use a relatively inexpensive ceramic element with a relatively high thermal conductivity. In addition, the coefficient of thermal expansion is comparable to that of copper. This has a positive effect on thermal shock resistance, since thermal stresses are less pronounced than in conventional ceramic materials.

[0046] Alternatively, it is conceivable that the bonding of at least one metal layer to the ceramic element is effected via an active solder (i.e. by means of a solder layer comprising an active metal), in which case, for example, the active metal content in the solder layer has a value of less than 15% by weight.

[0047] It is further preferably provided that the bonding of at least one metal layer to the ceramic element 30 consisting of or comprising magnesium oxide is carried out under pressure, provided that an active metal layer (preferably only one active metal layer) is disposed between the ceramic element 30 and the at least one metal layer (i.e., provided that there is no solder material or solder substrate in the intermediate region between the ceramic element and the at least one metal layer). By applying pressure when bonding the metal layer to the ceramic element 30, it is also advantageous to increase the density of the magnesium oxide, for example, to a value greater than 75 TD, preferably greater than 85 TD, and even more preferably greater than 95 TD. The term TD refers in particular to the theoretical density (i.e., the smallest or densest theoretically possible packing of individual molecules in the solid of the ceramic element).

[0048] It is further preferably provided that the component metallization has a first thickness D1, the backside metallization has a second thickness D2, and the ceramic element has a third thickness. The first thickness D1, the second thickness D2, and the third thickness D3 are measured parallel to the stacking direction S. It is preferably provided that the first thickness D1 essentially corresponds to the second thickness D2 to thereby create the desired symmetry that compensates for warping during manufacturing of the metal substrate. This is not absolutely necessary, for example, if bonding occurs as part of the pressing process, since the pressing process itself compensates for warping. However, in conventional soldering processes, it has been found to be particularly advantageous if the first thickness D1 and the second thickness D2 are essentially equal to each other. Preferably, the third thickness D3 has a value between 50 μm and 2 mm, more preferably between 100 μm and 1000 μm, and even more preferably between 200 μm and 800 μm. The first thickness D1 and / or the second thickness D2 preferably have a value of 100 μm to 1000 μm, more preferably 200 μm to 800 μm, and most preferably 300 μm to 700 μm. Furthermore, it is most preferably provided that the third thickness D3 is greater than the first thickness D1 and / or the second thickness D2. It is also conceivable that the third thickness D3 is smaller than the first thickness D1 and / or the second thickness D2.

[0049] Magnesium oxide is preferably 3 g / cm 3 ~4g / cm 3 , preferably 3.15 to 3.7 g / cm 3 , and more preferably 3.3 to 3.56 g / cm 3 Most preferably, the magnesium oxide in the ceramic element 30 has a proportion of 95 to 100%, which is advantageous in taking advantage of the high thermal conductivity of the single crystal.

[0050] It is further preferably provided that the density of the magnesium oxide is increased by at least 20% by pressing. 2 shows a second embodiment of a metal-ceramic substrate 1 according to the invention. In the embodiment shown here, the ceramic element 30 is surrounded (in particular completely surrounded) by a ceramic coating (made for example of aluminum oxide Al2O3). This coating 30 serves the purpose of improving or simplifying the bonding of at least one metal layer to the insulator. In particular, it makes use of the fact that the surface can be solidified by spinel formation, thus also allowing DCB bonding (i.e. direct bonding).

[0051] 3 shows a third embodiment of a metal-ceramic substrate 1 according to the invention. In the embodiment shown here, it is provided that at least one metal layer and / or at least one further metal layer is bonded to a ceramic element 30 by a direct bonding method (in particular directly bonded to a ceramic element 30 essentially comprising magnesium oxide). In particular, the same material specifications apply to magnesium oxide in all the embodiments shown here. It is most preferably provided that doped magnesium oxide is used or provided as the ceramic element 30.

[0052] For example, additional or accompanying materials are used as dopants whose proportion in the ceramic element is less than 10% by weight, preferably less than 8% by weight, and more preferably less than 5% by weight. In particular, the accompanying materials used for doping are selected so as to have as little effect as possible on the thermal conductivity. That is, the accompanying materials used for doping cause a change in the thermal conductivity of the ceramic element that is less than 5%, preferably less than 2.5%, and more preferably less than 1% of the thermal conductivity measured in a pure magnesium oxide ceramic element having a comparable density. [Explanation of symbols]

[0053] 1 Metal ceramic substrate 10 Component Metallization 12 Bonding layer 12' additional bonding layer 13 Adhesive layer 20 Backside Metallization 30 ceramic elements 31 Coating S Stacking direction D1 First thickness D2 Second thickness D3 Third thickness

Claims

1. A metal ceramic substrate (1) that can be used as a printed circuit board, a ceramic element (30); At least one component metallization (10) bonded to said ceramic element (30); wherein the at least one component metallization (10) is structured to form conductor paths; The metal-ceramic substrate (1), wherein the ceramic element (30) comprises magnesium oxide, the proportion of magnesium oxide in the ceramic element being greater than 60% by weight, preferably greater than 80% by weight, more preferably greater than 95% by weight.

2. 2. The metal-ceramic substrate (1) of claim 1, wherein the ceramic element (30) comprising magnesium oxide is doped with an accompanying material.

3. 3. The metal-ceramic substrate (1) according to claim 2, wherein the accompanying material is selected so as not to impair the thermal conductivity, in particular so as to have a deviation of the thermal conductivity of less than 50%, preferably less than 25%, more preferably less than 20% of the thermal conductivity of magnesium oxide.

4. The auxiliary material is ZrO ２ 4. The metal-ceramic substrate (1) according to claim 2 or 3,

5. The magnesium oxide is 3 to 4 g / cm ３ value, preferably 3.1 to 3.8 g / cm ３ and more preferably 3.35 to 3.58 g / cm ３ 5. The metal-ceramic substrate (1) according to any one of claims 1 to 4, having a density with a value of

6. The ceramic element (30) is provided with a coating (31), preferably Al ２ O ３ 6. The metal-ceramic substrate (1) according to any one of claims 1 to 5, comprising a coating comprising:

7. A metal ceramic substrate (1) according to any one of claims 1 to 6, wherein in the manufactured metal ceramic substrate, a bonding layer (12) is formed between the component metallization (10) and the ceramic element (12), and the bonding agent layer (13) of the bonding layer (12) has a sheet resistance greater than 0.5 Ω / □, preferably greater than 1 Ω / □, more preferably greater than 2 Ω / □, or greater than 10 Ω / □.

8. The metal-ceramic substrate (1) according to any one of claims 1 to 7, wherein the component metallization (10) is bonded by a direct bonding method.

9. 9. The metal-ceramic substrate (1) according to any one of the preceding claims, wherein the component metallization (10) has a thickness of more than 0.4 mm, preferably more than 1.0 mm, more preferably more than 1.5 mm.

10. The metal-ceramic substrate (1) according to any one of the preceding claims, wherein the ceramic element (12) has a thickness of more than 200 μm, preferably more than 300 μm, more preferably more than 400 μm.

11. A method for producing a metal-ceramic substrate (1) that can be used as a printed circuit board, in particular a metal-ceramic substrate (1) according to any one of claims 1 to 10, comprising the steps of: providing a ceramic element (30) comprising magnesium oxide and a metal layer; bonding the metal layer to the ceramic element (30); structuring the metal layer to form the component metallization (10); A method comprising:

12. The method of claim 11 , wherein the metal layers are bonded via an active metal layer.

13. 13. The method of claim 11 or 12, wherein the at least one metal layer is bonded by hot isostatic pressing.

14. 14. The method of any one of claims 11 to 13, wherein the density of the ceramic element (30) is increased by the bonding.

15. The method of claim 11 , wherein the metal layer is bonded by a direct bonding method.

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