Metal-ceramic substrate and method for producing the same

Abstract

The invention relates to a metal-ceramic substrate (1) as a carrier for electrical components, in particular in the form of a printed circuit board, comprising a ceramic element (20) and one or more metal layers (10, 20), the one or more metal layers (10) and the ceramic element (30) extending along a main extension plane (HSE) and arranged on top of one another along a stacking direction (S) extending perpendicularly to the main extension plane (HSE), in which in the produced metal-ceramic substrate (1) a bonding layer (12) is formed between the one or more metal layers (10, 20) and the ceramic element (30), the adhesion-promoting layer of the bonding layer (12) having a surface resistance of more than 5 Ω / sq, preferably more than 10 Ω / sq, particularly preferably more than 20 Ω / sq, and in which vias (15) are formed in the ceramic element (30).

Description

[Technical field]

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

[0002] Carrier substrates for electrical components, for example in the form of metal-ceramic substrates, are well known from the prior art, for example as printed circuit boards or circuit boards, for example from US Pat. No. 5,399,633, US Pat. No. 5,499,663 and US Pat. No. 5,599,703. Typically, connection areas for electrical components and conductor paths are arranged on one component side of the metal-ceramic substrate, which can be interconnected to form an electrical circuit. Essential components of a metal-ceramic substrate are an insulating layer, which is preferably made of ceramic, and a component metallization or a component metallization bonded to the insulating layer. Ceramic insulating layers have been shown to be particularly advantageous in power electronics due to their relatively high insulating strength. By structuring the component metallization, conductor paths and / or connection areas for electrical components can be realized.

[0003] Additionally, it is common practice to provide interconnects that can join component metallization and backside metallization or metal interlayers together on a metal-ceramic substrate to enable electrical contact. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] DE 102013104739 [Patent Document 2] German Patent No. 19927046 [Patent Document 3] DE 102009033029 Summary of the Invention [Problem to be solved by the invention]

[0005] The object of the present invention is to improve the metal-ceramic substrates with interconnects known from the prior art, in particular with regard to the costs required for the production of the interconnects. [Means for solving the problem]

[0006] The invention achieves the object by means of metal-ceramic substrates according to claim 1 and a method for producing them according to claim 9. Further advantageous embodiments are evident from the dependent claims, the description and the drawings.

[0007] According to a first aspect of the invention, there is provided a metal-ceramic substrate as a carrier for electrical components, in particular in the form of a printed circuit board, comprising: -Ceramic elements; one or more metal layers, said one or more metal layers and said ceramic element being arranged on top of one another along a stacking direction extending along a main extension plane and perpendicular to said main extension plane, the metal-ceramic substrate thus produced has a bonding layer formed between the one or more metal layers and the ceramic element; A metal-ceramic substrate is provided in which the bonding agent layer of the bonding layer has a sheet resistance greater than 5 Ω / sq, more preferably greater than 10 Ω / sq, and most preferably greater than 20 Ω / sq, and interconnects are formed to the ceramic elements.

[0008] In contrast to the metal-ceramic substrates provided in the prior art, the metal-ceramic substrate according to the invention has a relatively high sheet resistance. This is due to the specific manufacturing process in which bonding of one or more metal layers to the ceramic element is utilized, in particular by the use of a separate, relatively thin active metal layer. The one or more metal layers can be component metallization, backside metallization and / or intermediate metallization of the metal-ceramic substrate. It has been shown that using the selected manufacturing process it is advantageously possible to realize the interconnection simultaneously with the bonding between the one or more metal layers and the ceramic element, so that no additional time-consuming work steps are required. The manufacturing process is reflected in the metal-ceramic substrate produced by the sheet resistance produced.

[0009] The interconnect is preferably embedded in or at least partially fills a recess in the ceramic element. The recess preferably extends from a top surface of the ceramic element to a bottom surface of the ceramic element, the component metallization being bonded to the top surface of the ceramic element and the backside metallization being bonded to the bottom surface of the ceramic element. Preferably, the bonding layer is also formed in or extends into the recess of the ceramic element. In the finished state, the interconnect is formed in the recess.

[0010] During the bonding process, the active metal layer used becomes the bonding layer or part of the bonding layer. Together with other parameters such as the thickness of the bonding layer, the purity of the applied active metal layer and / or the roughness of the ceramic element, this contributes to the correspondingly formed sheet resistance. To determine the sheet resistance, one or more metal layers and, if necessary, the solder base layer are first removed from the manufactured carrier substrate, for example by etching. Then, by means of a four-point measurement, the sheet resistance of the top or bottom surface of the carrier substrate from which the one or more metal layers and the solder base layer are released is measured. In particular, the sheet resistance of a material sample is understood as its resistance relative to a square surface area. It is customary to characterize the surface resistance by the unit Ω / sq (square). The physical unit of sheet resistance is Ω (ohm).

[0011] Preferably, the carrier substrate is provided as a printed circuit board in the manufactured state, in which one or more metal layers are structured, which are bonded to the ceramic elements. For example, for this purpose, structuring, for example by laser cutting, etching and / or mechanical processing, is also carried out after the bonding process, whereby conductor paths and / or connections for electric or electronic components are realized. Preferably, a further metal layer, in particular a backside metallization and / or a heat sink, is provided on the ceramic elements opposite the metal layer on the manufactured metal-ceramic substrate. The backside metallization preferably serves to counteract deflections, and the heat sink serves to effectively dissipate the heat released during operation by the electric or electronic components bonded to the printed circuit board or metal-ceramic substrate.

[0012] 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, are considered as materials for one or more metal layers and / or further metal layers or interconnects in the metal-ceramic substrate. Furthermore, preferably, one or more metal layers on the produced metal-ceramic substrate are surface modified, in particular as component metallization. The surface modification can be, for example, sealing with noble metals, in particular silver and / or gold, or (electroless) nickel or ENIG ("electroless nickel immersion gold"), or edge encapsulation on the metallization to suppress crack formation or expansion.

[0013] Preferably, the thickness of the bonding layer, in particular the bonding agent layer, measured in the stacking direction and averaged over a number of measurement points in a given area or in a number of areas extending parallel to the main extension plane, has a value of less than 20 μm, more preferably less than 10 μm, most preferably less than 6 μm. When the term "several areas" is used, it is meant in particular that one or more metal layers are subdivided into areas of as equal size as possible and one or more values ​​for thickness, more preferably several measurements, are recorded in each of these areas that subdivide one or more metal layers. The thicknesses thus determined at different points are arithmetically averaged.

[0014] In particular, the interconnect comprises a bonding layer and / or a further bonding layer, the bonding agent layer of the further bonding layer having a sheet resistance of more than 5 Ω / sq, more preferably more than 10 Ω / sq, most preferably more than 20 Ω / sq. In other words: preferably, the bonding layer with a relatively high sheet resistance extends inside the recess, thereby forming at least a part of the interconnect and / or the bonding layer is used to bond the metal for forming the interconnect. For example, if a different solder-based material is used to form the interconnect, a further bonding layer different from the bonding layer may be formed. Particularly advantageously, the active metal may be deposited on the top or bottom surface of the ceramic element and on the side of the recess in a common process step. In other words, no additional bonding agent needs to be applied. Preferably, the bonding agent layer for forming the bond between one or more metal layers and the ceramic element extends into the recess to form the interconnect.

[0015] Preferably, in a cross-sectional view extending parallel to the main extension plane, the recesses in the interconnects and / or the ceramic elements have a cross-section with a shape that deviates from a circular shape. It has been found that by adapting the geometry accordingly, it is advantageously possible to influence the thermal shock resistance of the substrate, especially in the region of the recesses or the interconnects. In particular, the tendency to crack formation can be reduced here. The region of the interconnects is stressed in terms of thermomechanical stresses when heat is generated on the component side during operation. A suitable geometry can contribute to a local relief. It is conceivable that star-shaped, dot-shaped, labyrinth-shaped, arc-shaped, polygonal, elliptical or other cross-sections can be used to influence the thermal shock resistance. Preferably, the interconnect region comprises a web-like subsection formed by the ceramic element. In particular, it has been shown to be particularly advantageous to form rounded corner regions in the interconnects, for example in the form of elongated holes recessed into the ceramic element. The recesses can be realized in the ceramic element by punching or removing subregions in the shaped body (i.e. before the ceramic element has hardened). However, it is also conceivable to remove subregions of the (sintered) ceramic element again, for example by mechanical, chemical and / or optical processes, for example by laser treatment, etching or milling processes.

[0016] It is also conceivable to form an arrangement of several interconnects in their parallel circuit, in other words, several interconnects replacing previous large area interconnects. For this purpose, corresponding arrangements are formed, for example, with an area of ​​40 interconnects / cm. 2 More preferably at least 90 interconnects / cm 2 or more, most preferably 140 interconnects / cm 2is formed. This arrangement is particularly advantageous in terms of reliability, since cracks due to thermal stresses can only propagate to the next interconnect. In this way, the reliability of the interconnect area can also be increased, since for example the failure of a single interconnect does not render the requirements for operating the metal-ceramic substrate no longer adequate.

[0017] The arrangement of the interconnects can follow a geometric specification or can be formed randomly on the ceramic element in subsections of the ceramic element. In other words, a regular or irregular arrangement can be provided. In particular, the arrangement of the interconnects forms a convex hull, i.e. a subset that includes the smallest convex set that includes the initial set. For example, the convex hull is repeated several times on the metal-ceramic substrate. However, it is also possible that there is only a single convex hull. The area enclosed by the convex envelope is determined by the arrangement of the recesses within the convex envelope, and in particular by the smallest area of ​​a shape that includes all the interconnects of the arrangement. Furthermore, the arrangement can preferably be designed in such a way that it can affect the thermomechanical fatigue resistance of the entire substrate, i.e. the metal-ceramic substrate. Preferably, the arrangement of the interconnects is formed such that it is possible to have a size of less than 4 mm. 2 More than 9mm is more preferable 2 More than 16mm, most preferably 2 It occupies an area of ​​more than 100 mm, especially in the form of a convex envelope.

[0018] Furthermore, the recesses in the ceramic elements have side surfaces that at least partially or completely surround the interconnects, the side surfaces being along a direction extending parallel to the stacking direction (S) and at least partially curved and / or inclined with respect to the stacking direction. This therefore relates to the side surfaces within the ceramic element and not to the top and bottom surfaces of the ceramic element that in any case face the component and / or the backside metallization or to the surrounding outer surfaces of the ceramic element. These side surfaces can be curved or may form an angle of, for example, more than 5°, more preferably more than 10° and most preferably more than 20° with respect to the stacking direction. In particular, the angle has a value between 0° and 45°, more preferably between 2° and 30° and most preferably between 5° and 15°. This simplifies the pressing in of the component metallization and the backside metallization, in particular as part of the bonding process using hot isostatic pressing. In addition to this, the correspondingly inclined course simplifies the application of the active metal and / or solder-based material by gas physical volume, since it provides easy access to the side surfaces.

[0019] Preferably, the recess is only partially filled, the ratio of the first volume of the recess filled with the conductive material to the second volume limited by the entire recess having a value between 0.05 and 0.8, more preferably between 0.055 and 0.5, most preferably between 0.05 and 0.20. It has been found that it is even possible to ensure an interconnection with a relatively low filling that meets the operational requirements of the metal-ceramic substrate. In particular, it is possible to form the interconnection only by the active metal layer, which in the bonding process becomes the bonding layer, and the solder base layer. In this case, the ratio of the first volume to the second volume is preferably less than 0.3, more preferably less than 0.2, most preferably less than 0.15. Furthermore, preferably, the interconnection in the produced metal-ceramic substrate has a porosity whose proportion to the total volume of the interconnection, i.e. the sum of the volumes of the individual pores, has a value of less than 0.3, more preferably less than 0.1, most preferably less than 0.01. For example, the percentage of porosity relative to the total volume of the interconnect has a value of 0-0.2, more preferably 0-0.05, most preferably 0-0.02. In particular, porosity refers to the percentage of pores in the molten phase before wetting the inside of the recess. A relatively low porosity allows for a more uniform electrical conductivity and improved bonding to the inside of the recess. If a solder base layer is provided in addition to the active metal layer to form the bonding layer, the solder base layer preferably comprises an Ag or Cu alloy. As a result, a solder base material with a low resistivity is used in the joining process, thus resulting in a low resistance in the manufactured interconnect.

[0020] It is also conceivable that the interconnects have a different material composition than the bonding layer between the component metallization and / or the backside metallization. For example, different solder base materials can be used for the interconnection and bonding of the metal layers. For this purpose, the ceramic element provided with recesses is immersed in a molten metal, for example Cu, In and / or Al. Preferably, the electrical resistance of an interconnect or of several interconnects, preferably connected in parallel, has a value of 10 μΩ to 10 mΩ, more preferably 100 μΩ to 2 mΩ, most preferably 250 μΩ to 1 mΩ. Furthermore, preferably, the area-normalized electrical conductivity of the interconnect or of a matrix of multiple interconnects or of an arrangement of interconnects associated with a convex envelope is >50 kS / cm 2 , more preferably >150 kS / cm 2 , most preferably >300 kS / cm 2 has a value of

[0021] Preferably, the conductor material of the interconnect is formed by a metal layer, in particular at least partially molded into the recess. This occurs in particular during the manufacture of the interconnect as part of hot isostatic pressing, where the component metallization and / or backside metallization is pressed into the recess by high pressure. In this case, a bump is formed on the outside of the component metallization and / or backside metallization, in particular on the surface side opposite the ceramic element. The recess in the ceramic element is preferably filled completely. Due to the large conductor cross-section, a relatively low electrical resistance can be realized for the interconnect. In addition to this, the interconnect is formed by the component metallization or backside metallization, which has a low resistivity due to its material and purity.

[0022] In particular, the interconnect is formed as a through-hole metallization covering the side surface (SF) of the recess, the inner diameter of which has a value between 0.1 mm and 2 mm, more preferably between 0.2 mm and 1 mm, most preferably between 0.3 mm and 0.6 mm. This provides a relatively large free volume for the interconnect. Preferably, the interconnect is formed by a bonding layer and / or a further bonding layer, in particular only by a bonding layer and / or a further bonding layer.

[0023] Preferably, the ratio of the area of ​​the side surface defining the recess covered by the conductive material to the total area of ​​the side surface defining the recess has a value of more than 0.8, more preferably more than 0.9, most preferably more than 0.95. Thus, a conductive layer is formed, especially inside the recess (e.g. by a bonding layer also provided for bonding the metal layer to the ceramic element), which contributes to the interconnect forming the conductive bond between the top and bottom surfaces of the ceramic element. For example, the interconnect provides in the center an empty volume surrounded by the inner coating of the recess for forming the interconnect.

[0024] A further object of the invention is a method for producing a metal-ceramic substrate according to the invention, whereby the advantages and properties of the metal-ceramic substrate can be transferred to the method for producing the same, and vice versa. In particular, the interconnect is produced simultaneously with the bonding of the component metallization and / or the backside metallization to the ceramic element. Preferably, the bonding of the ceramic element to the component metallization and / or the backside metallization is performed as part of hot isostatic pressing and / or using a solder system with a separate active metal layer. In particular, the interconnect is produced without a separate metal element filling the recess in the produced state. In other words, only the metal layer bonded to the top and / or bottom surface of the ceramic element is used when producing the interconnect.

[0025] In particular, the ceramic element is provided with recesses in which interconnections are realized, preferably simultaneously or overlapping in time with the bonding of one or more metal layers to the ceramic element, the active metal layer having an active metal content of more than 15% by weight, more preferably more than 40% by weight, most preferably more than 70% by weight.

[0026] To form the active metal layer, the active metal is preferably applied by gas-physical or chemical methods, such as, for example, PVD, CVD or PECVD methods. Galvanic, electroless and / or thermal application or application by cold gas spraying are also conceivable.

[0027] Preferably, the sides of the recess are at least partially covered by the active metal layer, which advantageously allows to provide a bonding or active metal layer that is as uniform as possible and relatively thin, and a corresponding bonding layer having a sheet resistance of more than 5 Ω / sq, more preferably more than 10 Ω / sq, most preferably more than 20 Ω / sq is produced as part of the bonding process.

[0028] for example, - providing a solder layer, in particular in the form of one or more solder or brazing foils, - coating the ceramic element, in particular the inside of the recesses of the ceramic element, and / or the one or more metal layers and / or the one or more solder layers, with one or more active metal layers, - arranging one or more solder layers between the ceramic element and the one or more metal layers along a stacking direction to form a solder system comprising one or more solder layers and one or more active metal layers, the solder material of the one or more solder layers preferably not comprising a melting point lowering material or a phosphorus-free material; - bonding one or more metal layers to one or more ceramic layers via a soldering system by an active soldering process.

[0029] In particular, a multilayer soldering system is provided, which consists of one or more soldering layers, preferably free of elements that reduce the melting point, preferably free of phosphorus, and one or more active metal layers. The separation of one or more active metal layers and one or more solder layers has proven to be particularly advantageous, especially when the solder layer is a foil, since a relatively thin solder layer can be realized as a result. Due to the brittle intermetallic phases or high modulus of elasticity and high yield strength of common active metals and their intermetallic phases, which would otherwise prevent the formation of a solder paste or solder layer, a relatively large solder layer thickness needs to be realized for active metal-containing solder materials, thus limiting the minimum layer thickness resulting from the manufacture of active metal-containing solder materials. It is therefore not the minimum thickness required for the joining process that determines the minimum solder layer thickness for active metal-containing solder layers, but rather the minimum layer thickness of the solder layer that can be technically realized that determines the minimum solder layer thickness of the solder layer. As a result, this thicker active metal-containing solder layer is more expensive than a thinner layer. By phosphorus-free, the skilled artisan understands, in particular, that the percentage of phosphorus in the solder layer is less than 150 ppm, less than 100 ppm, and most preferably less than 50 ppm.

[0030] 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 furthermore conceivable that the solder material for forming the solder layer is deposited on the active metal layer and / or on the one or more metal layers by physical vapor deposition and / or chemical vapor deposition and / or electroplating, which advantageously makes it possible to achieve a relatively thin solder layer in the soldering system, in particular with a uniform distribution.

[0031] For example, in the manufacture of metal-ceramic substrates, particularly metal-ceramic substrates, - 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 bonding the metal layer to the ceramic element by hot isostatic pressing. An active metal layer or a contact layer comprising an active metal is at least partially disposed between the metal layer and the ceramic element to support bonding of the metal layer to the ceramic element to form a metal-ceramic substrate. Preferably, the active metal layer or the contact layer comprising an active metal is also formed inside the recess. The container is preferably formed as a metal container from the metal layer and / or the further metal layer. Alternatively, it is also conceivable to use a glass container.

[0032] In hot isostatic pressing, bonding is provided, in particular by heating under pressure, and the first and / or second metal layers of the metal container, in particular the subsequent metal layers of the metal-ceramic substrate and any eutectic layers occurring therein, do not transition to a molten phase.Heat isostatic pressing therefore requires lower temperatures than direct metal bonding methods, in particular the DCB method.

[0033] Compared to the bonding of metal layers to ceramic layers with solder materials, where temperatures below the melting temperature of one or more metal layers are usually used, the present procedure advantageously allows the solder-based material to be dispensed with and only requires active metal. The use or utilization of pressure during hot isostatic pressing is also shown to be advantageous, since air inclusions or cavities between the first and / or second metal layers on the one hand and the ceramic element on the other hand can therefore be reduced and the frequency of voids forming in the formed or produced metal-ceramic substrate can therefore be reduced or even avoided. This has an advantageous effect on the quality of the bond between the metal layer of the metal container or the first and / or second metal layers and the ceramic element. In addition to this, it is advantageously possible to simplify the "second etching" and avoid solder residues and silver migration.

[0034] It is also contemplated that additional solder material may be introduced between the ceramic element and the one or more metal layers during hot isostatic pressing, and the melting temperature of the additional solder material may be lower than the temperature at which the hot isostatic pressing is performed, i.e., lower than the melting temperature of the one or more metal layers.

[0035] Preferably, during hot isostatic pressing, the metal container is subjected to a gas pressure of 10 MPa to 200 MPa (100 to 2000 bar), more preferably 15 MPa to 120 MPa (150 to 1200 bar), most preferably 30 MPa to 100 MPa (300 to 1000 bar) and a treatment temperature of 300°C up to the melting temperature of the one or more metal layers, in particular to a temperature below the melting temperature. It has therefore been found advantageously possible to bond the metal layer, i.e. the first metal layer and / or the second metal layer of the metal container, to the ceramic element without the necessary temperatures of direct metal bonding methods, e.g. DCB or DAB methods, and / or without the solder base material used in active soldering. In addition to this, the use or application of a corresponding gas pressure makes it possible to produce a metal-ceramic substrate that is as void-free as possible, i.e. without gas inclusions between the metal layer and the ceramic element. In particular, the process parameters mentioned in DE 2013113734 A1 are used, to which explicit reference is made in this specification.

[0036] Further advantages and features emerge from the following description of preferred embodiments of the subject matter according to the invention, with reference to the attached drawings, in which: The individual features of the individual embodiments can be combined with one another within the scope of the invention. [Brief description of the drawings]

[0037] [Figure 1] FIG. 1 shows a metal-ceramic substrate with interconnects according to the prior art. [Diagram 2] 1 is a cross-sectional view of a metal-ceramic substrate according to a first exemplary embodiment of the present invention. [Diagram 3]FIG. 4 is a cross-sectional view of a metal-ceramic substrate according to a second exemplary embodiment of the present invention. [Figure 4A] FIG. 2 shows a cross-sectional area of ​​a recess in a ceramic element. [Figure 4B] FIG. 2 shows a cross-sectional area of ​​a recess in a ceramic element. [Figure 4C] FIG. 2 shows a cross-sectional area of ​​a recess in a ceramic element. [Figure 4D] FIG. 2 shows a cross-sectional area of ​​a recess in a ceramic element. [Figure 4E] FIG. 2 shows a cross-sectional area of ​​a recess in a ceramic element. [Figure 5A] FIG. 2 shows a side view of a recess in a ceramic element. [Figure 5B] FIG. 2 shows a side view of a recess in a ceramic element. [Figure 5C] FIG. 2 shows a side view of a recess in a ceramic element. [Figure 5D] FIG. 2 shows a side view of a recess in a ceramic element. [Figure 5E] FIG. 2 shows a side view of a recess in a ceramic element. [Figure 5F] FIG. 2 shows a side view of a recess in a ceramic element. [Figure 5G] FIG. 2 shows a side view of a recess in a ceramic element. [Figure 6A] FIG. 1 shows an arrangement of interconnects. [Figure 6B] FIG. 1 shows an arrangement of interconnects. [Figure 6C] FIG. 1 shows an arrangement of interconnects. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0038] FIG. 1 shows a schematic representation of a metal-ceramic substrate 1 according to the prior art. Such a metal-ceramic substrate 1 is preferably a carrier for an electrical component. In particular, the metal-ceramic substrate 1 comprises a ceramic element 30 and a component metallization 10, which extend along a main extension plane HSE. The component metallization 10 is bonded to the ceramic element 30, the component metallization 10 and the ceramic element 30 being arranged on top of each other in a stacking direction S perpendicular to the main extension plane HSE. In particular, the component metallization 10 comprises a plurality of metal parts, for example a first metal part 11 and a second metal part 12, which are arranged next to each other, for example electrically insulated from each other, along a direction extending parallel to the main extension plane HSE.

[0039] In particular, in the prior art it is common to first bond the component metallization 10 to the ceramic element 30, in particular by a direct metal bonding process and / or an active soldering process or an AMB process and / or an ADB process and / or hot isostatic pressing. A bonding process of this kind is a high-temperature process in which the arrangement consisting of the ceramic element 30 and the component metallization 10 is exposed to elevated temperatures, in particular temperatures above 500° C. After the bonding process, a structuring is carried out, for example by an etching process, in order to realize electrically insulated metal parts, in particular the first metal part 11 and the second metal part 12, which can be used as conductor paths and / or connection areas for electrical circuits, so-called pads.

[0040] On the side of the ceramic element 30 opposite the component metallization 10, a backside metallization 20 is preferably bonded, which backside metallization 20 is in particular bonded to the ceramic element 30 simultaneously, i.e. in a common working step, as the component metallization 10. Alternatively, the component metallization 10 and the backside metallization are bonded sequentially. Such a backside metallization 20 serves in particular to compensate for thermomechanical stresses in the metal-ceramic substrate 1 caused by different thermomechanical expansion coefficients of the component metallization 10 and the ceramic element 30.

[0041] In this connection, the component metallization 10 comprises at least a first metal portion 11 and a second metal portion 12. The first metal portion 11 and the second metal portion 12 are separated from one another after structuring so as to form corresponding conductor paths and / or connection areas electrically insulated from one another. For this purpose, for example by chemical and / or mechanical and / or optical methods, a structuring is embedded in the component metallization 10, and recesses in the component metallization 10 required for the structuring extend at least up to the ceramic element 30 so as to provide the required electrical insulation. Such insulation is formed in particular in the form of trenches in the component metallization 10, also colloquially known as insulating trenches.

[0042] The backside metallization 20 and the component metallization 10 have essentially equal thicknesses to provide the desired symmetry between the component side and the backside of the metal-ceramic substrate 1 and thus allow them to mutually compensate for corresponding thermomechanical stresses occurring in the metal-ceramic substrate 1. The thicknesses are measured along a direction following the stacking direction S.

[0043] In such metal-ceramic substrates 1, it is also common to provide the ceramic element 30 with interconnects 15, for example so that the component metallization 10 can be in electrical contact with the backside metallization 20. The backside metallization 20 can then also be used, for example, to conduct current, in particular to compensate for any parasitic inductive effects. Typically, for this purpose, a recess is formed in the ceramic element 30, for example by means of laser light or drilling, in which recess a cylindrical part, preferably of metal, is embedded, which is bonded to the side surface SF of the ceramic element 30 in the region of the recess embedded in the ceramic element 30.

[0044] In contrast to the prior art, in this case the formation of the interconnects 15 is linked to a specific manufacturing process in which the component metallization 10 or the backside metallization 20 is bonded to the ceramic element 30. In particular, bonding processes are used in which a bonding layer 12 with a sheet resistance of more than 5 Ω / sq, more preferably more than 15 Ω / sq, most preferably more than 20 Ω / sq, is formed between the component metallization 10 or backside metallization 20 on the one hand and the ceramic element 30 on the other hand. For example, these are bonding methods in which a separate active metal layer is placed between the component metallization 10 or backside metallization 20 and the ceramic element 30. By hot isostatic pressing or with a solder-based material used in addition to the separate active metal layer, it is possible to carry out a bonding process that leads to the desired sheet resistance, provided that the surface roughness value of the ceramic element and / or the purity of the active metal layer are suitable. It has been found that the use of such methods means in particular that the insertion of costly metal parts and the usually multi-stage bonding process is no longer necessary to achieve an interconnect 15 that meets the requirements necessary for operation, i.e. that provides adequate electrical resistance and sufficient thermal shock resistance.

[0045] FIG. 2 shows, in a schematic and exemplary manner, a metal-ceramic substrate 1 with an interconnection 15 according to an embodiment of the present invention. In particular, this is an embodiment in which a bonding layer 12 is generated between the component metallization 10 or backside metallization 20 and the ceramic element 30 by providing the ceramic element 30 with an active metal layer 13 and arranging a solder-based layer 14 between the component metallization 10 or backside metallization 20 to be bonded and the active metal layer 13. The active metal layer 13 preferably has more than 15 weight percent, more preferably more than 20 weight percent, most preferably more than 60 weight percent active metal and is therefore not to be understood as a solder layer containing active metal. Most preferably, the active metal layer 13 is deposited on the ceramic element 30 by a gas physical deposition process, in particular also on the side surfaces SF limiting the recess of the ceramic element 30. This makes it possible to achieve an active metal layer 13 that is as uniformly distributed as possible and applied relatively thinly, in particular also in the region of the side surfaces 15 of the recess. The solder base layer 14 can also be deposited on the active metal layer by a gas physical deposition process, and / or by a dipping process, and / or by a screen printing process, and / or by another deposition process. It is also conceivable that the active metal layer 13 and / or the solder base layer 14 are applied as a foil or provided as such. In particular, it has been found that the corresponding bonding process achieves interconnects 15 whose recesses have a relatively large free volume.

[0046] In particular, it has been found that these methods make it possible to achieve interconnects 15 having a first volume filled by conductive material relative to a second volume of the entire recess of less than 0.4, more preferably less than 0.3, and most preferably less than 0.2. In this way, it is advantageously possible to achieve sufficient interconnects 15 that meet the requirements for forming interconnects 15 that meet operating conditions.

[0047] FIG. 3 shows a metal-ceramic substrate 1 with an interconnection 15 according to a further embodiment of the invention. In particular, the interconnection 15 shown here is the result of the formation of a bonding process of a component metallization 10 and / or a backside metallization 20 to a ceramic element 30 by hot isostatic pressing. For this purpose, an active metal layer 13 is placed between the component metallization 10 or backside metallization 20 to be bonded and the ceramic element 30. The hot isostatic pressing, in particular the pressure applied and acting on the metal-ceramic substrate 1, then presses a part of the component metallization 10 or backside metallization 20 into the recess formed, in particular so that the component metallization 10 and the backside metallization 20 are in contact with each other. This creates an electrical contact between the component metallization 10 and the backside metallization 20. Here again, no additional work steps need to be incorporated to achieve the interconnection 15. The formed metal-ceramic substrate 1 has a recess-like depression formed on the outer surface side of the component metallization 10 or backside metallization 20, which can be used to easily locate, for example, the interconnect 15 in the fabricated metal-ceramic substrate 1. For example, such a depression or depression can also be used to identify the location of the metal-ceramic substrate 1 as part of the manufacturing process. After all, this is a visually recognizable feature on the outside of the metal-ceramic substrate 1.

[0048] 4a to 4e show embodiments of the shape of recesses, which can be recessed in the ceramic element 20, in which the interconnects 15 are realized. In particular, these are cross-sectional shapes formed along a plane extending parallel to the main extension surface. In addition to the usual circular cross-section, as shown for example in FIG. 4a, it is also conceivable to incorporate, for example, star courses for the recesses in the ceramic element 20 (see FIG. 4b). Primarily, as shown in FIG. 4c, any polygonal embodiment of the cross-section is also conceivable. These include square, rectangular, hexagonal and triangular cross-sections. FIG. 4d shows in particular that rounded shapes are possible, for example, side faces SF in the recesses that meet at an angle are avoided. In particular, the adaptation of the geometry of the interconnects 15 shows to be advantageous for thermal shock resistance, since a relief of the resulting thermomechanical stresses can be prevented in this way. It is also conceivable that the recesses are formed as a system of several geometric shapes. For example, FIG. 4e shows the formation of a recess complex in which several arc-shaped parts or arc-section parts are arranged in a labyrinth-like manner with respect to one another. Preferably, at least the first and second arcuate portions are offset from one another by an angle between 80° and 120°, preferably about 90°. For example, it is envisioned that the corresponding recess complex provides a rod-like connecting element formed within the recess complex.

[0049] Furthermore, it is conceivable that the geometry of the recess is not completely filled with the metal or conductor material for forming the interconnect 15. For example, it is conceivable that the conductor material in the recess for forming the interconnect 15 has a different cross-sectional geometry than the recess has in a plane extending parallel to the main extension surface HSE.

[0050] FIG. 5a shows the shape or course of the side SF of the recess in the ceramic element 30. In FIG. 5a, the recess is essentially cylindrical, thus forming a side SF that extends essentially perpendicular to the main extension plane HSE or parallel to the stacking direction S. In FIG. 5b, an embodiment is provided in which the side SF is rounded. The side SF can be concave or convex. It is also conceivable that the recess provides both convex and concave side SF. For example, the design with a convex ridge shown in FIG. 5b shows to be particularly advantageous for the creation of interconnects during hot isostatic pressing, since it makes it easier to press the component metallization 10 into the recess during the pressing process.

[0051] In principle, however, any curved geometry of the side SF of the recess is also conceivable, as shown, for example, in FIG. 5d. Conical or frustoconical designs, such as those shown in FIG. 5e, are most preferably used for forming, in particular during hot isostatic pressing. In particular, forming into a simple frustoconical course leads to the metallization on the open side being pushed further into the recess than the metal layer on the opposite side during hot isostatic pressing, which results in or induces an asymmetry with respect to the proportion of metallization provided by the component metallization or the backside metallization for the interconnect. In contrast, in FIG. 5g, two frustoconical courses, i.e. a double frustoconical course, are provided, which in particular allows the metal to be pushed equally from both sides into the recess for forming the interconnect 15. In FIG. 5f, an example embodiment is shown in which the side SF is aligned such that the smallest diameter of the recess, measured in a plane extending parallel to the main extension plane, is formed on the top and bottom faces of the ceramic element 30.

[0052] 6a to 6c show an arrangement of interconnects 15. In particular, it is conceivable to realise, instead of the interconnects 15, an arrangement of a relatively large number of small recesses with correspondingly embedded interconnects 15. In particular, it is conceivable to realise an arrangement of a relatively large number of small recesses with correspondingly embedded interconnects 15. 2 More preferably, 90 recesses / cm 2More than 140 recesses / cm, most preferably 140 recesses / cm 2 It is envisaged that a wide variety of configurations may be provided for such an arrangement. The example shown in Figure 6a is essentially a rectangular arrangement. The triangles shown in Figure 6b form a square surface. The slots shown in Figure 6c together form a triangular surface as an arrangement. [Explanation of symbols]

[0053] 1 Metal-ceramic substrate 10 Component Metallization 12 Bonding Layer 13 Active metal layer 14 Solder base layer 15 Interconnection 20 Backside Metallization 30 Ceramic Elements science fiction aspect S Stacking direction HSE main extension plane

Claims

1. A metal-ceramic substrate (1) as a carrier for electrical components, in particular in the form of a printed circuit board, A ceramic element (30); one or more metal layers (10, 20), said one or more metal layers (10) and said ceramic element (30) extend along a main plane of extension (HSE) and are arranged on top of each other along a stacking direction (S) extending perpendicular to said main plane of extension (HSE); In the produced metal-ceramic substrate (1), a bonding layer (12) is formed between the one or more metal layers (10, 20) and the ceramic element (30); the bonding agent layer of the bonding layer (12) has a sheet resistance of greater than 5 Ω / sq, more preferably greater than 10 Ω / sq, and most preferably greater than 20 Ω / sq; A metal-ceramic substrate (1) in which interconnects (15) are formed on said ceramic element (30).

2. 2. The metal-ceramic substrate (1) of claim 1, wherein the interconnect (15) comprises one or both of the bonding layer (12) and a further bonding layer (12), the bonding agent layer of the further bonding layer having a sheet resistance of more than 5 Ω / sq, more preferably more than 10 Ω / sq, most preferably more than 20 Ω / sq.

3. 3. The metal-ceramic substrate (1) according to claim 1 or 2, wherein in a cross-sectional view extending parallel to the main plane of extension (HSE), one or both of the interconnects (15) and the recesses in the ceramic element (30) have a cross-section whose shape deviates from circular.

4. The metal-ceramic substrate (1) according to any one of claims 1 to 3, wherein the arrangement of the plurality of interconnects (15) is formed to be a parallel circuit of the plurality of interconnects (15).

5. The metal-ceramic substrate (1) according to any one of claims 1 to 4, wherein the recess in the ceramic element (30) provided for the interconnect (15) has a side surface (SF) which at least partially surrounds the interconnect (15), the side surface (SF) being along a direction extending parallel to the stacking direction (S), at least partially curved, or inclined with respect to the stacking direction (S), or one or more of these.

6. 6. The metal-ceramic substrate (1) according to any one of the preceding claims, wherein the recess is only partially filled and the ratio of a first volume filled with conductive material to a second volume limited by the recess has a value between 0.05 and 0.8, more preferably between 0.05 and 0.50, most preferably between 0.05 and 0.

2.

7. A metal-ceramic substrate (1) according to any one of claims 1 to 6, wherein the conductive material of the interconnect (15) is formed at least in part, preferably more than halfway, by the one or more metal layers (10, 20), in particular at least in part, molded into the recess.

8. The metal-ceramic substrate (1) according to any one of claims 1 to 7, wherein the interconnects (15) are formed as through-hole metallizations covering the side surfaces (SF) of the recesses, the inner diameter of the through-hole metallizations having a value between 0.1 mm and 2 mm, more preferably between 0.2 mm and 1 mm, most preferably between 0.3 mm and 0.6 mm.

9. A method for manufacturing a metal-ceramic substrate (1) according to any one of the preceding claims.

10. The method according to claim 9 , wherein the side surface (SF) of the recess is at least partially covered by an active metal layer.

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