Metal-ceramic substrate and method for manufacturing a metal-ceramic substrate

Abstract

To reduce the tendency of metal-ceramic substrates to warp and provide substrates that are as flat as possible. [Solution] A metal-ceramic substrate 1 provided as a printed circuit board for mounting electrical components, comprising a component metallization portion 10 and a back surface metallization portion 20, and a ceramic element 30 disposed between the component metallization portion 10 and the back surface metallization portion 20 along the stacking direction, wherein the component metallization portion 10 includes a first metal section 11 and a second metal section 12, the first metal section 11 and the second metal section 12 being separated from each other by an insulating section 15, and the back surface metallization portion 20 having a material weakening portion 25, in particular a material recess disposed at least partially coincide with the insulating section 15 when viewed in the stacking direction.

Description

Technical Field

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

Background Art

[0002] For example, a carrier substrate for electrical components in the form of a metal ceramic substrate is well known from the prior art as, for example, a printed circuit board or a circuit board from Patent Documents 1 to 3. Typically, connection areas for electrical components and conductor paths are arranged on one component side of the metal ceramic substrate, where the electrical components and conductor paths can be interconnected to form an electrical circuit. The essential components of the metal ceramic substrate are more preferably an insulating layer made of ceramic, and a component metallization part, or a component metallization part joined to the insulating layer. Insulating layers made of ceramic have proven to be particularly advantageous in power electronics due to their relatively high insulation strength. By structuring the component metallization part, conductor paths and / or connection areas for electrical components can be created.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Patent Document 3

[0004] Based on prior art, the present invention aims to improve metal-ceramic substrates to further reduce their tendency to warp and to provide metal-ceramic substrates that are as flat as possible. [Means for solving the problem]

[0005] The present invention achieves this objective by using a metal-ceramic substrate manufactured by the method described in claim 1 and the method described in claim 10. According to the first aspect, a metal-ceramic substrate is provided which is provided or intended to be a printed circuit board for mounting electrical components, and this substrate is The metallization section of the component and the metallization section on the back surface, It comprises a ceramic element arranged along the stacking direction between the component metallization portion and the back surface metallization portion, The component metallization section includes a first metal section and a second metal section, the first metal section and the second metal section being separated from each other by an insulating section. The metallized portion on the back surface has material weakening portions, particularly material recesses that are positioned in the lamination direction and coincide with the insulating section.

[0006] In contrast to metal-ceramic substrates known from the prior art, the back surface metallization portion has a material weakening portion, which is specified to be positioned to coincide with or extend over the insulating section or multiple insulating sections on the component side. This advantageously improves the symmetry of the material distribution on the component side and the opposite back surface. As a result, the thermomechanical stresses generated on the component side and the back surface cancel each other out, thus reducing the overall bending tendency of the substrate. This means that the tendency to bend can be further reduced, and a metal-ceramic substrate that is as flat as possible can be provided. For this purpose, preferably, the first thickness of the component metallization portion substantially corresponds to the second thickness of the back surface metallization portion.

[0007] Coincident placement means that a spatial overlap with the insulating section is established, particularly when the material weakening area is virtually projected along the lamination direction or in a direction parallel to the lamination direction. In this case, this virtual spatial overlap occurs over more than 50%, more preferably more than 75%, and most preferably more than 90% of the extent of the material weakening area in the back surface metallization area. The center of the material weakening area's extent can be positioned essentially coincident with the center of the insulating section's extent, or it can be offset laterally, i.e., perpendicular to the lamination direction.

[0008] Furthermore, preferably, the ceramic element is specified to have a third thickness measured along the lamination direction. Particularly preferably, the third thickness is specified to be less than 700 μm, more preferably less than 400 μm, and most preferably less than 330 μm. The symmetry between the material weakening portion in the back surface metallization portion and the insulating section in the component metallization portion has been found to be particularly advantageous for relatively thin insulating layers or ceramic elements, because these ceramic elements are particularly bendable and susceptible to damage. For example, the third thickness of the ceramic element may be less than or even thinner than the first thickness of the component metallization portion and the second thickness of the back surface metallization portion, or the sum of the first and second thicknesses.

[0009] Furthermore, it is preferably specified that the introduction of structuring and / or material weakening is carried out after the metallization portion and / or back surface metallization portion is bonded to the ceramic element.

[0010] In particular, metal-ceramic substrates are used as printed circuit boards. On these substrates, metallization areas, i.e., component metallization areas, are formed on the component side, and this component side has several electrically insulated metallization sections due to its structure. These metallization sections form, for example, connection areas, pads, or conductor paths on the printed circuit board.

[0011] Preferably, the ceramic element may be made from Al2O3, Si3N4, AlN, HPSX ceramics (i.e., ceramics having an Al2O3 matrix containing x percent ZrO2, e.g., Al2O3=HPS9 with 9% ZrO2 or Al2O3=HPS25 with 25% ZrO2), SiC, BeO, MgO, high-density MgO (>90% of theoretical density), or TSZ (tetragonal stabilized zirconium oxide). Alternatively, the ceramic element may be formed as a compound ceramic or hybrid ceramic, in which case several ceramic layers, each with a different material composition, are placed on top of each other and joined together to form an insulating element in order to combine various desired properties.

[0012] Copper, aluminum, molybdenum, tungsten, and / or alloys thereof such as CuZr, AlSi, AlMgSi, and others, as well as laminates such as CuW, CuMo, CuAl, and / or AlCu, or metal matrix composites (MMCs) such as CuW, CuMo, and AlSiC, are considered materials for the component metallization portion and / or back surface metallization portion. Preferably, the component metallization portion corresponds to or differs from the back surface metallization portion with respect to its material. Furthermore, preferably, the component metallization portion and / or back surface metallization portion on the manufactured metal ceramic substrate is specified to be surface modified, particularly as the component metallization portion. Surface modification may include, for example, sealing with precious metals, especially silver and / or gold, or (electroless) nickel or ENIG ("electroless nickel immersion gold"), or crack formation or swelling. One method to suppress tension is edge encapsulation on the metallized portion. For example, the metal in the metallized portion of a component is different from the metal in the metallized portion on the back surface.

[0013] The bonding of the metal layer, i.e., the metallized portion of the component and / or the metallized portion on the back surface, to the ceramic element can be carried out, for example, by the DCB method, AMB method, diffusion bonding, particularly ADB, and / or hot isostatic pressing method.

[0014] Those skilled in the art will understand that the "DCB method" (direct copper bonding technique) or the "DAB method" (direct aluminum bonding technique) is a method used, for example, to bond metal layers or sheets (e.g., copper sheets or copper foils or aluminum sheets or aluminum foils) to each other and / or to ceramics or ceramic layers, that is, using metal sheets, copper sheets, metal foils or copper foils having a layer or coating (molten layer) on their surface side. For example, in the method described in U.S. Patent No. 3,744,120 or German Patent No. 2,319,854, the layer or coating (molten layer) forms a eutectic having a melting temperature lower than the smelting temperature of the metal (e.g., copper), and as a result, by placing the foil on a ceramic and heating all the layers, they can be bonded to each other by essentially smelting the metal or copper only in the region of the molten layer or oxide layer.

[0015] Preferably, the ceramic layer and the metal layer are joined by a direct metal bonding process, a hot isotropic pressing process, a soldering process and / or a diffusion bonding process. In particular, the DCB method then proceeds to, for example, the following method steps, namely, • Oxidizing the copper foil so that a uniform copper oxide layer is formed, • Placing copper foil on a ceramic layer, • Heating the composite material to a process temperature of approximately 1025-1083°C, for example, approximately 1071°C, It includes cooling to room temperature.

[0016] For example, an active soldering process for joining a metal layer or metal foil, particularly a copper layer or copper foil, to a ceramic material should be understood as a method also used particularly in the manufacture of metal-ceramic substrates. Using a hard solder containing an active metal in addition to a main component such as copper, silver and / or gold, it is manufactured at a temperature of about 600 to 1000 °C between a metal foil, for example a copper foil, and a ceramic substrate, for example an aluminum nitride ceramic. This active metal, which is at least one element from the group of Hf, Ti, Zr, Nb, Ce, causes a bond to occur between the solder and the ceramic by a chemical reaction, and the bond between the solder and the metal is a brazed connection. Alternatively, a thick film process can also be considered for joining.

[0017] Preferably, the ADB (Active Diffusion Bonding) method is provided as a diffusion bonding method. This is for example the following steps, namely, providing a ceramic element and a metal layer, and providing a hermetic container surrounding the ceramic element, the container preferably being formed from the metal layer or including the metal layer, and forming a metal-ceramic substrate by joining the metal layer to the ceramic element by a hot isostatic pressing method, including An active metal layer or a contact layer containing an active metal is arranged at least in the section between the metal layer and the ceramic element to assist the joining of the metal layer to the ceramic element to form a metal-ceramic substrate. The container is preferably formed as a metal container from the metal layer and / or a further metal layer. Alternatively, using a glass container can also be considered.

[0018] In the hot isostatic pressing method, the joining is provided particularly by heating under pressure, and the metal layer of the metal container, particularly the subsequent metal layer of the metal-ceramic substrate and any eutectic layer occurring therein, do not transition to the molten phase. Therefore, the hot isostatic pressing method requires a lower temperature than the direct metal bonding method, particularly the DCB method.

[0019] Compared to the joining of a metal layer to a ceramic layer with a solder material where a temperature below the melting temperature of at least one metal layer is typically used, this procedure advantageously eliminates the need for a solder base material and only requires an active metal. The use or utilization of pressure during hot isostatic pressing can reduce the inclusion of air or voids between one metal layer and the other ceramic element, and thus can also reduce or even avoid the formation of voids at their frequency in the formed or manufactured metal-ceramic substrate, which has also been found to be advantageous. This has a beneficial effect on the quality of the joint between the metal layer of the metal container and the ceramic element. Even more advantageously, "second etching" can be simplified and solder residues and silver migration can be avoided.

[0020] The contact layer containing an active metal layer contains more than 15 weight percent of the active metal. The hot isostatic pressing method is known, for example, from European Patent No. 3080055, the content of which is expressly incorporated herein by reference with respect to the hot isostatic pressing method.

[0021] Furthermore, the material weakening part is more preferably formed as a domed recess. One opening of these domed recesses in the backside metallization part can face the ceramic element and / or face away from the ceramic element. It is also conceivable that a material section having a material different from the material of the backside metallization part is provided in the backside metallization part as the material weakening part. For example, each recess in the backside metallization part can be filled with a corresponding filling material whose coefficient of expansion does not significantly contribute to the formation or support / reinforcement of thermomechanical stress. Such a filling material enhances stability without impairing the desired thermomechanical symmetry between the component side and the backside.

[0022] The recess can also have a circular, diamond-shaped, square, rectangular, or polygonal cross-section in a direction parallel to the main extension plane. In particular, it should be noted that the coordinated arrangement relates to the arrangement of material weakening areas. In contrast, for example, it is not necessary to provide a back surface material weakening area for each sub-region of the insulating section on the component side. In other words, the first total area occupied by the insulating section in the component metallization area is greater than the second total area occupied by the material weakening areas in the back surface metallization area. Preferably, the ratio of the second area to the first area is defined as having a value of 0.6 to 0.9, more preferably 0.7 to 0.9, and most preferably 0.75 to 0.9. Here, further material weakening areas are not preferably considered, and are realized in addition to material weakening areas embedded in the back surface metallization area in conjunction with the insulating section.

[0023] In particular, the insulating section in the component metallization portion extends along a first course, and in particular, extends uninterrupted, while on the opposite side, multiple material weakening portions are formed that are separated from each other in a coincident arrangement in the back surface metallization portion. Furthermore, the material weakening portions on the outer surface of the back surface metallization portion are defined to face away from the ceramic element and have a first spread of less than 1.0 mm, more preferably less than 0.8 mm, and most preferably less than 0.7 mm. Furthermore, it is defined that two adjacent material weakening portions are preferably arranged at a first distance of less than 600 μm, more preferably less than 400 μm, and most preferably less than 250 μm from each other. Furthermore, the first distance and / or first spread may differ for some material weakening portions. Alternatively, for example, the first spread or first distance between two adjacent material weakening portions in the back surface metallization portion may be the same.

[0024] Preferably, the insulating sections in the component metallization portion follow a first course in a plane running parallel to the main extension plane, and one or more material weakening portions in the back surface metallization portion follow a second course in a plane extending parallel to the main extension plane, with the second course coinciding with the first course in the stacking direction, and in particular, the second course is specified to coincide with the first course by more than 50%, more preferably more than 70%, most preferably more than 90%, or completely with its total length. Thus, the material weakening portions and insulating sections are not only coincident with each other in a cross-section running perpendicular to the main extension plane, but also coincide with each other with respect to their first and second courses extending in a plane running parallel to the main extension plane. Individualized or partial sections in the back surface metallization portion may be omitted with respect to their coincident arrangement with respect to the insulating section or multiple insulating sections. In other words, as long as there is a material weakening area in the back surface metallization area, it is preferably always positioned in conjunction with an insulating section, but it is not necessarily required that the material weakening area in the back surface metallization area coincide with the insulating section. If necessary, this can prevent the back surface metallization area in this metallic region from being excessively weakened by the closely spaced insulating section.

[0025] The first course and / or the second course may have straight or curved sections arranged at an angle or offset from each other. More preferably, the second course of the material weakening portion or a plurality of material weakening portions is defined as being formed by a series of material weakening portions, for example, a row of holes or a series of dome-shaped recesses, and / or along the second course, the back surface metallization portion has a stabilization region between the two material weakening portions. In particular, a row of holes is formed by a series of adjacent dome-shaped recesses. Between two adjacent dome-shaped recesses, the back surface metallization portion may have a partial section having a second thickness, or a residual metallization portion larger than the residual metallization portion between the recess and the ceramic element may be provided. As a result, the stability of the metallic ceramic substrate is maintained despite the improved symmetry. Preferably, the first distance between two adjacent material weakening portions is defined as less than 600 μm, less than 400 μm, and most preferably less than 250 μm. In particular, the recesses are specified to be manufactured by chemical methods, e.g., etching; mechanical methods, e.g., milling; or optical methods, e.g., laser light, especially laser pulses. The use of laser light, in particular, allows for the formation of the narrowest and most precisely positioned material weakening areas, especially recesses. The stabilization areas are preferably characterized by the fact that the material weakening areas are not very prominent. For example, the depth of the recesses in the stabilization areas is smaller, or in some areas, there are no recesses at all in the stabilization areas.

[0026] Preferably, in addition to material weakening portions that are positioned coincidentally with the insulating section, further material weakening portions are provided embedded in the back surface metallization portion in the peripheral region of the back surface metallization portion. In contrast to the material weakening portions, the further material weakening portions are defined as not having or not having a coincidentally positioned insulating section on the opposite side when viewed in the lamination direction.

[0027] For example, preferably, the further material weakening portion is specified to be located in the peripheral region of the back surface metallization portion that protrudes from the component metallization portion in a direction parallel to the main extension plane. In this case, the component metallization portion is smaller than the back surface metallization portion, particularly in terms of its extent along the main extension plane. The further material weakening portion can form a row of holes or as a flat side surface, i.e., at a particularly small inclination angle, which is, for example, at least a multiple of 2, more preferably at least a multiple of 3, and most preferably at least a multiple of 5, than the corresponding inclination angle on the component side. The different extents of the component metallization portion and the back surface metallization portion ensure sufficient distance from the outer edge of the ceramic element on the component side to prevent electrical flashover, and the section of the back surface metallization portion protruding from the component metallization portion improves the stability of the metallic ceramic substrate in the peripheral region.

[0028] This means of further material weakening can achieve further improvements in the metal-ceramic substrate, which can counteract the flexibility of the metal-ceramic substrate and, in particular, further improve thermal shock resistance. The further edge-side material weakening can also be designed as a curved sidewall profile having at least one intermediate maximum value. Furthermore, preferably, the first extent of the further material weakening is defined to be smaller than the first extent of the material weakening. If the material weakening and the further material weakening each have different extents, preferably, their respective average values ​​are defined to be considered. Furthermore, the peripheral region is defined to be understood as a metallization portion or a partial section of the back surface metallization portion that extends from the outer periphery of the back surface metallization portion and occupies less than 10%, more preferably less than 5%, and most preferably less than 2% of the total area of ​​the back surface metallization portion. Furthermore, the further material weakening is defined to surround, and in particular completely surround, the region having the material weakening portion.

[0029] Furthermore, it is more preferable that the material weakening portion in the form of a recess runs to or extends to the ceramic element. This achieves high symmetry between the component side and the back surface. Alternatively, a residual metallization portion may be formed in the region of the material weakening portion, and as a result, this residual metallization portion can contribute to improving the overall stability of the metal-ceramic substrate. This is particularly advantageous when using a very thin insulating layer or ceramic element, otherwise the insulating layer or ceramic element is more prone to fracture. For example, measured in the lamination direction, the residual metallization portion has a fourth thickness, where the ratio of the fourth thickness to the second thickness is defined as less than 0.5, more preferably less than 0.4, and most preferably less than 0.2.

[0030] In particular, if the material weakening area formed as a recess extends to the ceramic element, it is conceivable that a residual metallization area may be formed between the further material weakening area formed as a recess and the ceramic element. This allows the material weakening area to be distinguished from further material weakening areas, for example, in the peripheral region.

[0031] Preferably, the first width of the insulating section is determined by the distance between the first and second metal sections, measured along a first direction perpendicular to the first course, and the ratio of the second width of the material weakening portion, measured along the first direction, to the first width is specified to be between 0.1 and 2, more preferably between 0.5 and 1.5, and most preferably between 0.75 and 0.9. In particular, it has been shown that if the material weakening portion on the back surface metallization portion does not extend across the entire second width of the insulating section, a sufficient degree of symmetry with respect to the thermodynamic spread on the component side and the back surface can already be established. As a result, the stability of the metal-ceramic substrate can be maintained, and there is no risk of fracture points occurring in the metal-ceramic substrate due to the small amount of material on the back surface.

[0032] Preferably, the ratio of sections where the first course and the second course do not run coincidentally with each other when viewed in the stacking direction to sections where the first course and the second course run coincidentally with each other when viewed in the stacking direction is defined as having a value of less than 1, more preferably less than 0.5, and most preferably less than 0.2. The overall symmetry on the front and back surfaces of the metal-ceramic component can be improved as the proportion of coincidentally placed material weakening areas increases, and thus the overall bendability of the correspondingly designed metal-ceramic substrate is found to be further improved or reduced.

[0033] Preferably, a heat sink is bonded to the back surface metallization portion. In particular, the material weakening portion is defined as being embedded in the back surface metallization portion, for example, in the form of a recess. Therefore, the material weakening portion embedded in the back surface metallization portion is not a recess embedded in a heat sink that is bonded to the back surface metallization portion and is provided in particular to dissipate heat generated during the operation of a specific metal ceramic substrate into a cooling fluid.

[0034] In particular, per unit length along the first course and / or second course, the insulating section has a first volume, and the material weakening portion in the back surface metallization portion has a second volume, where the first and second volumes are defined to be substantially equal in terms of their absolute size and different in terms of their geometric shape. In this way, on the one hand, the symmetry between the recess in the part metallization portion and the recess in the back surface metallization portion can be maintained as much as possible, and at the same time, measures can be taken to enhance stability in the area in which the insulating section or material weakening portion is embedded. In this context, those skilled in the art will preferably understand that “substantially equal” volumes are volumes that do not deviate from each other by more than 10%, more preferably more than 5%, and most preferably more than 2.5% of their average values. The first and second volumes may differ, for example, in terms of their depth, their width, and / or their length. Thus, in order to ensure that the volumes of the recesses in the part metallization portion and the back surface metallization portion are essentially the same, for example, different widths or diameters can be used correspondingly for recesses of different depths on the part side and the back surface.

[0035] According to another object of the present invention, a metal-ceramic substrate is provided which is provided as a printed circuit board for mounting electrical components, and the metal-ceramic substrate is The metallization section of the component and the metallization section on the back surface, It comprises a ceramic element arranged along the stacking direction between the component metallization portion and the back surface metallization portion, The component metallization section includes a first metal section and a second metal section, the first metal section and the second metal section being separated from each other by an insulating section and / or a connection area for electrical components provided on the first metal section. The back surface metallization area has material weakening areas, in particular, material recesses that are positioned to at least partially coincide with the connection areas when viewed in the lamination direction. All advantages and properties described for metal-ceramic substrates having material weakening areas positioned coincide with the insulating sections can be similarly applied to advantages and properties or specifications described for metal-ceramic substrates having material weakening areas coincide with the connection areas, and vice versa. In particular, metal-ceramic substrates having both material recesses that coincide with the insulating sections and (further) material recesses that coincide with the connection areas can be considered.

[0036] Preferably, the connection region is characterized by a corresponding planar extent, which is wider than the conductor path in the main extension plane and therefore distinctly different from the conductor path. The material weakening portion may extend across the entire region adjacent to the connection region. Alternatively, only a partial section of the back surface metallization portion adjacent to the connection region may have material weakening portions in some areas, for example, adjacent to the edge sections of the connection region. Preferably, the material weakening portion adjacent to the connection region is arranged in a two-dimensional pattern.

[0037] A further object of the present invention is a method for manufacturing a metal-ceramic substrate, in particular a metal-ceramic substrate according to the present invention, the method being The component is provided with a metallization section, a back surface metallization section, and a ceramic element. The metallization portion of the component and the metallization portion of the back surface are joined to a ceramic element, wherein the ceramic element is arranged between the metallization portion of the component and the metallization portion of the back surface along the lamination direction, By implementing an insulating section, the component metallization section is structured, This includes realizing a material weakening area in the back surface metallization area, wherein the material weakening area is positioned in the lamination direction, coinciding with the insulating section.

[0038] All the advantages, properties, and specifications described for metal-ceramic substrates can be similarly applied to this method, and vice versa. [Brief explanation of the drawing]

[0039] Further advantages and features are derived from the following description of preferred embodiments of the object of the present invention, with reference to the accompanying drawings. Thereafter, the individual features of the individual embodiments can be combined with one another within the scope of the present invention.

[0040] The following is shown. [Figure 1] A conventional metal-ceramic substrate. [Figure 2] A cross-sectional view of a metal-ceramic substrate according to a first exemplary embodiment of the present invention. [Figure 3] A cross-sectional view of a metal-ceramic substrate according to a second exemplary embodiment of the present invention. [Figure 4] A metal-ceramic substrate according to a third exemplary embodiment of the present invention. [Figure 5] Two different material weakening areas in the metallization section on the back surface. [Figure 6] A fourth embodiment of the present invention shows the metallization portion (bottom), the back surface metallization portion (top), and a side view (center) of a metal ceramic substrate. [Figure 7] A comparison between a recess forming an insulating section and a recess forming a material weakening section for a metal-ceramic substrate, according to a fifth exemplary embodiment of the present invention. [Modes for carrying out the invention]

[0041] Figure 1 schematically shows a conventional metal-ceramic substrate 1. Such a metal-ceramic substrate 1 is preferably a carrier for electrical components. In particular, the metal-ceramic substrate 1 has a ceramic element 30 and a component metallization portion 10, and the ceramic element 30 and the component metallization portion 10 are defined to extend along a main extension plane HSE. The component metallization portion 10 is bonded to the ceramic element 30, and the component metallization portion 10 and the ceramic element 30 are arranged on top of each other in a stacking direction S perpendicular to the main extension plane HSE. In particular, the component metallization portion 10 has a plurality of metal sections, for example a first metal section 11, a second metal section 12, and a second third metal section 13, and these metal sections are defined to be arranged adjacent to each other and electrically insulated from each other along a direction running parallel to the main extension plane HSE.

[0042] In particular, in the prior art, it is common to first bond the component metallization portion 10 to the ceramic element 30 by a direct metal bonding process and / or an active soldering process or an AMB process and / or an ADB process and / or a hot isostatic pressing method. Such bonding processes are high-temperature processes, in which the arrangement of the ceramic element 30 and the component metallization portion 10 is exposed to elevated temperatures, particularly temperatures exceeding 500°C. After the bonding process, structuring is performed, for example, by an etching process, to realize electrically insulated metal sections, particularly the first metal section 11 and the second metal section 12, and these metal sections can be used as conductor paths and / or connection areas, so-called pads, for electrical circuits.

[0043] Preferably, a back surface metallization portion 20 is joined to the side of the ceramic element 30 opposite to the component metallization portion 10, and the back surface metallization portion 20 is joined to the ceramic element 30 at the same time as the component metallization portion 10, i.e., in a common work step. Alternatively, the component metallization portion 10 and the back surface metallization portion are joined to each other. Such a back surface metallization portion 20 serves to compensate for the thermomechanical stress in the metal-ceramic substrate 1 caused by the different thermomechanical expansion coefficients of the component metallization portion 10 and the ceramic element 30.

[0044] In this context, the component metallization section 10 is defined to have at least a first metal section 11, a second metal section 12, and / or a third metal section 13. After structuring, the first metal section 11, the second metal section 12, and / or the third metal section 23 are separated from each other by insulating sections 15 to form corresponding conductive paths and / or connection areas that are electrically insulated from each other. For this purpose, the structuring is embedded in the component metallization section 10, for example, by chemical and / or mechanical and / or optical methods, and the recesses in the component metallization section 10 required for structuring extend to at least a ceramic element 30 to provide the necessary electrical insulation. Such insulating sections 15 are formed in the component metallization section 10 in particular in the form of trenches, and are colloquially known as insulating trenches. The corresponding first course VE1 of the trench-shaped insulating section 15 follows a specific pattern depending on the application of the metal-ceramic substrate 1 provided as a printed circuit board. In particular, the first course of the insulating section 15 for a series of manufactured metal-ceramic substrates 1 is specified to be set individually for the corresponding application.

[0045] To provide the desired symmetry between the component side BS and the back side RS of the metal-ceramic substrate 1, and thus enable the corresponding thermomechanical stresses arising in the metal-ceramic substrate 1 to be compensated for by each other, the back side metallization portion 20 and the component metallization portion 10 are specified to have substantially equivalent thicknesses. The thickness is measured along the direction of the lamination direction S.

[0046] Figure 2 shows a metallic ceramic substrate 1 according to a first exemplary embodiment of the present invention. To reduce the warpability of the metallic ceramic substrate 1, a material weakening portion 25 is embedded in the back surface metallization portion 20, in addition to the insulating section 15 in the component metallization portion 10. In the embodiment shown in Figure 2, the material weakening portion 25 is a recess in the back surface metallization portion 20, the recess extends particularly to the ceramic element 20, resulting in complete insulation of a partial section of the back surface metallization portion 30. In particular, the material weakening portion 25 is specified to be positioned substantially coincide with the insulating section 15 when viewed in the lamination direction S. This is advantageous as it further improves the symmetry between the component side BS and the back surface RD, and thus further reduces the warpability of the metallic ceramic substrate 1. Furthermore, the component metallization portion 10 has a first thickness D1 and the back surface metallization portion 20 has a second thickness D2, the first thickness D1 and the second thickness D2 are substantially equal. In this context, “substantially” is understood to mean that the deviation between the first thickness D1 and the second thickness D2 is less than 10%, more preferably less than 5%, and most preferably less than 2.5% of the average value of the first thickness D1 and / or the second thickness D2.

[0047] Furthermore, the ceramic element 30 is specified to have a third thickness D3. Preferably, the third thickness D3 is specified to have a value of less than 700 μm, more preferably less than 400 μm, and most preferably less than 330 μm. Thus, these are relatively thin insulating layers or ceramic elements 30, and correspondingly more flexible. Thus, the improved symmetry brought about by additionally including coincidentally placed material weakening portions 25 is advantageously possible in resisting bending in such a metal-ceramic substrate 1 in which a relatively thin insulating layer, i.e., a relatively thin ceramic element 30, is used.

[0048] Furthermore, the insulating section is defined to have a first width B1, and the material weakening portion 25 is defined to have a second width B2. Preferably, the second width B2 is defined to be smaller than the first width B1. In particular, the ratio of the second width B2 to the first width B1 may be 0.1 to 2.0, more preferably 0.5 to 1.5, and most preferably 0.75 to 0.5. In the example of the embodiment shown in Figure 2, the side surface of the back surface metallization portion 20 in the region of the material weakening portion 25 formed as a recess runs substantially perpendicular to the main extension plane HSE. However, here, particularly when the material weakening portion 25 embedded in the back surface metallization portion 20 is realized by an etching process, it is preferable that the formed side surface is curved or inclined.

[0049] The first width of the insulating section 15 is determined in particular by the minimum distance between two opposing metal sections 11, 12, and 13 at the point of measurement of the insulating section 15. The first direction R1 in which the first width B1 is determined lies within the main extension plane HSE and is in particular perpendicular to the direction in which the insulating section 15 extends according to a first course VE1 in the main extension plane HSE. This first course VE1 is predetermined by a corresponding pattern provided on each metal-ceramic substrate 1. The magnitude of the second width B2 is preferably determined at the same position on the back surface RS along the same first direction R1.

[0050] Furthermore, “coincidence” should be understood to mean that a spatial overlap of more than 50%, preferably more than 75%, and more preferably more than 95%, can be determined along a virtual projection of the extent of the material weakening portion 25 onto the extent of the insulating section 15 parallel to the lamination direction S. The centers of the extent of the material weakening portion 25 and the centers of the insulating section 15 may be located above each other in the lamination direction, or may be offset laterally from each other along a direction running perpendicular to the first course VE1 or perpendicular to the second course VE2, particularly in the main extension plane HSE.

[0051] Figure 3 shows a cross-sectional view through a metal-ceramic substrate 1 according to a second exemplary embodiment of the present invention. The embodiment of Figure 3 differs in essence from the embodiment of Figure 2 only in that, in the embodiment of Figure 3, the material weakening portion 25 formed as a recess does not extend to the ceramic element 30. In particular, a residual metallization portion 40 is provided in the region of the material weakening portion 25. This residual metallization portion 40 has a fourth thickness D4 that is smaller than the second thickness D2. Preferably, the ratio of the fourth thickness D4 to the second thickness D2 is less than 0.5, more preferably less than 0.25, and most preferably less than 0.1. This embodiment has the advantage that the residual metallization portion 40 can be used to contribute to the stability of the ceramic element 30, while simultaneously considering the symmetry of the component side BS and the back surface RS. To compensate for the presence of the residual metallization portion 40, the second thickness D2 may be smaller than the first thickness D1. Furthermore, in another embodiment, the material weakening portion 25 provided as a recess in the metal-ceramic substrate 1 may partially extend to the ceramic portion 30, with the other section having a residual metallization portion 40. In other words, the metal-ceramic substrate 1 includes a material weakening portion 25 formed as a recess, a part of which extends to the ceramic element 30, and a part of which has a residual metallization portion 40.

[0052] Furthermore, in an example of another embodiment, the fourth thickness D4 may differ and vary for different material weakening sections 25, and in particular, may be adapted to the degree of thermomechanical stress expected for each layout / pattern of the insulating section 15 or each planned first course VE1.

[0053] Figure 4 shows a side view (center), a top view (top) of the back surface RS, and a top view (bottom) of the component side BS of a metal-ceramic substrate 1 according to a third exemplary embodiment of the present invention. In particular, the material weakening portion 25 in the back surface metallization portion 20 is defined to be formed as a row of holes or as a series of material weakening portions 25. Such a row of holes has been found to be particularly advantageous because the metallization portions held between the individual holes enhance the stability of the metal-ceramic substrate 1 and at the same time improve the symmetry of the material recesses on the component side BS and back surface RS of the metal-ceramic substrate 1. Preferably, the row of holes is a series of circular and / or dome-shaped recesses. The embodiment of the recess shown in the cross-sectional view extends to the ceramic element 30 (left), and the recess terminates at the back surface metallization portion (right), i.e., a residual metallization portion 40 is provided between the recess and the ceramic element 30.

[0054] Furthermore, the rows or series of holes in the material weakening section 25 are defined to follow a second course VE2, which in particular coincides with a first course VE1 provided by an insulating section 15 on the part side BS or in the part metallization section 10. The first course VE1 and the second course VE2 in the main extension plane HSE may each have subsections angled relative to each other, and / or curved subsections joining, for example, straight subsections to each other. It is also conceivable that the first course VE1 and / or the second course VE2 have branches.

[0055] Furthermore, preferably, the first distance AB1 between two adjacent recesses or material weakening portions 25 is defined as being less than 600 μm, more preferably less than 400 μm, and most preferably less than 250 μm. In particular, the first distance AB1 between two material weakening portions is defined as being greater than the first spread E1.

[0056] It is also possible that the recesses, arranged as a row of holes, are in contact with each other or integrated with each other, and are not separated from each other by metal sections extending to the outside of the back surface metallization area.

[0057] Furthermore, it is more preferable that, in addition to the material weakening portion 25, a further material weakening portion 26 is provided, which is formed in the peripheral region of the back surface metallization portion 20. In particular, the further material weakening portion 26 is formed as a series of further material weakening portions 26, particularly as a row of holes, and this series of further material weakening portions 26 extends in a frame-like manner along the peripheral region of the back surface metallization portion 20 or the metal ceramic substrate 1. In particular, the course of the further material weakening portion 26 is defined to be located outside the region in which the material weakening portion 25 is formed, which is arranged to coincide with the first course VE1 or the arrangement of the insulating section 15 on the component side BS. Furthermore, the further material weakening portion 26, particularly formed as a further recess, is defined to have a first extent E1 smaller than the first extent E1 of the material weakening portion 25, on the outside of the back surface metallization portion 20 facing away from the ceramic element 30. Furthermore, the ratio of the first spread E1 of the further material weakening portion 26 to the first spread E1 of the material weakening portion 25 is less than 0.7, less than 0.6, and most preferably less than 0.5. Preferably, the first spread E1 of the further material weakening portion 26 is less than 1.2 mm, more preferably less than 0.9 mm, and most preferably less than 0.7 mm. Furthermore, more preferably, the first distance AB1 between two adjacent further material weakening portions 26 is specified to be smaller than the distance between two material weakening portions 25. The distance between the material weakening portions 25 or between the further material weakening portions 26 is determined here from center to center of each recess. Furthermore, preferably, the peripheral region is understood to be the region extending from the outer periphery toward the center of the back surface metallization portion 20, and the extent of the peripheral region is specified to be limited to a maximum of 10%, particularly a maximum of 5%, and more preferably a maximum of 2% of the entire extent of the back surface metallization portion 20.

[0058] Figure 5 shows cross-sectional views through two different forms of the material weakening portion 25. In particular, the dome-shaped recess is defined to have a first spread E1 on the outside of the back surface metallization portion 20 facing away from the ceramic element 30. Preferably, the first spread E1 is defined to be substantially identical for all material weakening portions 25, in particular for all dome-shaped recesses. It is also possible that the sizes of the first spread E1 of different dome-shaped recesses positioned in conjunction with the insulating section 15 differ from one another.

[0059] Preferably, the first extent E1 of the material weakening portion 25, particularly the dome-shaped recess, is defined as being less than 1.5 mm, more preferably less than 1.0 mm, and most preferably less than 0.75 mm. If the dome-shaped recess extends to the ceramic element 30, preferably, the second extent E2 of the material weakening portion 25 on the outside of the back surface metallization portion 20 facing the ceramic element 30 is defined as being less than 1.3 mm, more preferably less than 0.8 mm, and most preferably less than 0.6 mm. In particular, the ratio of the second extent E2 to the first extent E1 has a value of 0.6 to 0.95, more preferably 0.7 to 0.9, and most preferably 0.75 to 0.85.

[0060] Figure 6 shows the component metallization section 10 (bottom), the back surface metallization section 20 (top), and a side view (center) of the metal-ceramic substrate 1 according to a fourth exemplary embodiment. The embodiment in Figure 6 differs from the embodiment in Figure 4 in that the first course VE1 and the second course VE2, which coincide with each other and are located in the central region of the component metallization section 10 or the back surface metallization section 20, respectively, have several subsections angled toward each other. This is necessary to realize a desired pattern for forming a conductor path or connection pad. In particular, the following figure shows the first course VE1, along which the insulating section 15 extends in a plane running parallel to the main extension plane HSE. In the selected top view, it can be seen that the ceramic element 30 protrudes from the component metallization section 10 in a direction parallel to the main extension plane HSE in order to form a pullback.

[0061] Essentially, in the embodiment of Figure 6, the back surface metallization portion 20 is defined to provide a material weakening portion 25 that is aligned with the first course VE1 of the insulating section 15 on the component metallization portion 10, and a further material weakening portion 26 that is located in the peripheral region of the back surface metallization portion 20. It can be seen that the further material weakening portion 26 in the peripheral region is not aligned with the entire insulating section 15.

[0062] In the embodiment shown in Figure 6, the ceramic element 30 is further defined to protrude less from the back surface metallization portion 20 than from the component metallization portion 10 in a direction parallel to the main extension plane HSE. As a result, the probability of flashover on the component side BS decreases as the distance to the end of the ceramic element 30 increases, and on the back surface RS, the stabilization of the metallic ceramic substrate 1 is supported by the peripheral region of the back surface metallization portion 20. In particular, the further material weakening portion 26 is defined to be located in the peripheral region of the back surface metallization portion 20, in a region of the back surface metallization portion 20 that protrudes from the component metallization portion 10 in a direction parallel to the main extension plane HSE. In the side view, it can be seen that the back surface metallization portion 20 has a larger spread on the main extension plane HSE than the component metallization portion 10 and protrudes from the component metallization portion 10 in a direction parallel to the main extension plane HSE.

[0063] Furthermore, although the second course VE2 of the material weakening section 25 is positioned to perfectly coincide with the insulating section 15, the second course VE2 may include a partial section in which the material weakening section 25 is omitted (not shown). Therefore, the first course VE1 does not perfectly coincide with the second course VE2 because the first course VE1 has a sub-region on the back surface metallization section 20 in which the material weakening section 25 is not provided. This is particularly useful for regions in which a high-density insulating trench or insulating section 15 is provided, thereby allowing the introduction of the corresponding material weakening section 25 on the back surface RS to lead to the corresponding destabilization of the metallic ceramic substrate 1.

[0064] Figure 7 schematically shows a comparison between the recesses assigned to the insulating section 15 and the recesses assigned to the material weakening portions 25 of the metal-ceramic substrate 1. In other words, the central region of Figure 7 shows top views of the component side BS and the back side RS, respectively, and thus reveals several material weakening portions 25 in the form of dome-shaped recesses that form, for example, a series of second surfaces A2 of the same size overall in the top view of the back side RS, and a first surface A1 for the recesses of the insulating section 15.

[0065] Here, cross-sectional views are also shown passing through the component metallization section (top) and the back surface metallization section (bottom) along the similarly inserted cutting line AA. The recess assigned to the insulating section 15 on the component side BS has a first depth T1, and the material weakening section 25 formed as a dome-shaped recess has a second depth T2. To achieve the greatest possible symmetry, it is specified that, with respect to a fixed unit length LE, the first volume V1 of one or more recesses for forming the insulating section 15 corresponds in size to the second volume V2 occupied per unit length LE by the recesses or multiple recesses in the back surface metallization section 10 in the region of the back surface metallization section 20 facing the insulating section 15. The unit length LE is preferably formed by a first distance AB1 between two adjacent material weakening sections 25 and / or extends over 1 cm, more preferably 2 cm, and most preferably 2.5 cm. In particular, it is specified that the shapes of the first volume V1 and the second volume V2 are different despite having the same volume size. For example, the insulating section 15 is formed by a continuous recess, while the material weakening section 25 on the back surface RS is formed on a dome-shaped recess. As a result, for example, a second depth T2 does not correspond to the first depth T1, and the length of the recess associated with the insulating section 15, measured along a first course VE1 and / or a second course VE2, does not correspond to the corresponding length of the material weakening section 25. If the recess in the material weakening section 25 extends to the ceramic element 30, more preferably, for example, a first area A1 per unit length LE is defined to substantially correspond to a total second area A2 on the back surface RS, because the diameter of the recess on the back surface RS is increasing. To consider different forms of the material weakening section 25 with respect to the recess for forming the insulating section 15, the diameter of the dome-shaped recess, i.e., the second width B2, can be selected to be larger than, for example, the corresponding first width B1 of the associated insulating section 15. This has proven advantageous, in particular, as more material is retained on the back surface RS, and therefore the overall stability of the metal-ceramic substrate 1 is improved, especially in the region of the insulating section 15. However, at the same time, a decrease in symmetry that could bend the metal-ceramic substrate 1, especially during operation, is avoided.

[0066] Furthermore, it is possible to set the first volume V1 and / or the second volume V2 such that the first volume V1 and the second volume V2 are essentially corresponding to each other, by the corresponding first depth T1 and / or second depth T2.

[0067] In this context, a person skilled in the art will understand that “substantially” means that a deviation of less than 10%, more preferably less than 5%, and most preferably less than 2.5% of the mean of the quantity or value being compared is expected. [Explanation of symbols]

[0068] 1...metal ceramic substrate, 10...component metallization area, 11...first metal section, 12...second metal section, 13...third metal section, 15...insulating section, 20...backside metallization area, 25...material weakening area, 26...further material weakening area, 30...ceramic element, 40...residual metallization area, S...lamination direction, BS...component side, RS...backside, HSE...main extension surface, R1...first direction, B1...first width, B2...second width, D1...first thickness, D2...second thickness, D3...third thickness, D4...fourth thickness, V1...first volume, V2...second volume, VE1...first course, VE2...second course, AB1...first distance, T1...first depth, T2...second depth, E1...first spread, E2...second spread.

Claims

1. A metal-ceramic substrate (1) provided as a printed circuit board for mounting electrical components, The component metallization section (10) and the back surface metallization section (20), The component comprises a ceramic element (30) arranged along the stacking direction (S) between the metallization portion (10) and the back surface metallization portion (20), The component metallization section (10) includes a first metal section (11) and a second metal section (12), the first metal section (11) and the second metal section (12) being separated from each other by an insulating section (15). In a metal-ceramic substrate (1), the back surface metallization portion (20) has a material weakening portion (25), and the material weakening portion (25) has a material recess that, when viewed in the stacking direction (S), is at least partially coincident with the insulating section (15), Multiple separated material weakening portions (25) are formed, two adjacent material weakening portions (25) are arranged at a first distance of less than 600 μm from each other, the first total area of ​​the component metallization portion occupied by the insulating section is greater than the second total area of ​​the back surface metallization portion occupied by the material weakening portions, and the ratio of the second total area to the first total area is 0.6 to 0.

9. The ceramic element (30) has a third thickness measured along the stacking direction (S), and the third thickness is less than 330 μm, in the metal-ceramic substrate (1).

2. The metal ceramic substrate (1) according to claim 1, wherein the material weakening portion (25) is formed as a dome-shaped recess.

3. The metal-ceramic substrate (1) according to claim 1 or 2, wherein the insulating section (15) in the component metallization section (10) follows a first course (VE1) in a plane extending parallel to the main extension surface (HSE), and the material weakening section (25) or a plurality of material weakening sections (25) in the back surface metallization section (20) follows a second course (VE2) in a plane extending parallel to the main extension surface (HSE), preferably the second course (VE2) is arranged to coincide with the first course (VE1) in the stacking direction (S).

4. The metal-ceramic substrate (1) according to claim 3, wherein the second course (VE2) of the material weakening portion (25) or the plurality of material weakening portions (25) is formed by a series of material weakening portions (25) in the form of rows of holes and / or has a stabilization region along the second course (VE2) between two material weakening portions (25).

5. A further material weakening portion (26) is provided, the further material weakening portion (26) is formed on the back surface metallization portion (20) in the peripheral region of the back surface metallization portion (20), and the further material weakening portion (26) is formed on the back surface metallization portion (20) independently of the insulating section (15), the metal ceramic substrate (1) according to claim 1 or 2.

6. The metal-ceramic substrate (1) according to claim 1 or 2, wherein the material weakening portion (25) formed as a recess in the back surface metallization portion (20) extends to the ceramic element (30).

7. The metal-ceramic substrate (1) according to claim 5, wherein the residual metallization portion (40) is formed between the material weakening portion (25) formed as a recess and the ceramic element (30).

8. The metal ceramic substrate (1) according to claim 3, wherein the ratio of sections in which the first course (VE1) and the second course (VE2) do not run coincidentally with each other when viewed in the stacking direction (S) to sections in which the first course (VE1) and the second course (VE2) run coincidentally with each other when viewed in the stacking direction (S) is less than 1, more preferably less than 0.5, and most preferably less than 0.

2.

9. A metal-ceramic substrate (1) according to claim 3, wherein per unit length (LE) along the first course (VE1) and / or the second course (VE2), the insulating section (15) has a first volume (V1), and the material weakening portion (25) or the plurality of material weakening portions in the back surface metallization portion (20) has a second volume (V2), and the first volume (V1) and the second volume (V2) are substantially equal in terms of their absolute size but different in terms of their geometric shape.

10. A metal-ceramic substrate (1) provided as a printed circuit board for mounting electrical components, The component metallization section (10) and the back surface metallization section (20), The component comprises a ceramic element (30) arranged along the stacking direction (S) between the metallization portion (10) and the back surface metallization portion (20), The component metallization section (10) has a first metal section (11) and a second metal section (12), the first metal section (11) and the second metal section (12) are separated from each other by an insulating section (15), and a connection area for electrical components is provided on the first metal section. The metal-ceramic substrate (1) has a material weakening portion (25) in the form of a material recess that is at least partially coincided with the connection region when viewed in the stacking direction (S), the back surface metallization portion (20) Multiple separated material weakening portions (25) are formed, and the back surface metallization portion has both a material recess that coincides with the insulating section and a material recess that coincides with the connection region. The ceramic element (30) has a third thickness measured along the stacking direction (S), and the third thickness is less than 330 μm, in the metal-ceramic substrate (1).

11. A method for manufacturing a metal ceramic substrate (1) according to claim 1 or 2, The component is provided with a metallization section (10), a back surface metallization section (20), and a ceramic element (30). The process involves joining the component metallization portion (10) and the back surface metallization portion (20) to the ceramic element (30), wherein the ceramic element (30) is arranged between the component metallization portion (10) and the back surface metallization portion (20) along the stacking direction (S), The component metallization section (10) is structured by realizing the insulating section (15), The material weakening portion (25) is realized in the back surface metallization portion (20), wherein the material weakening portion (25) is positioned to coincide with the connection region of the insulating section (15) and / or the first metal section when viewed in the lamination direction (S), Methods that include...

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