Metal-ceramic substrate with contact region

Abstract

To further enhance the thermal shock resistance of a metal-ceramic substrate.SOLUTION: A metal-ceramic substrate 1 comprises: a ceramic body 10 having a main boundary surface 15; a metal layer 20 having a main boundary surface 24, where the metal layer is surface-bonded to the ceramic body, and where the metal layer has a structuring region 4 that comprises solid material 50 and non-solid material; and a contact region 8 arranged on the metal layer, the contact region comprising silver. In a cross-section passing through the metal-ceramic substrate perpendicular to the main boundary surface of the ceramic body, the structuring region has a geometry which satisfies the following requirement: A(BCDsolid) / A(BCDtotal)>70%, where A(BCDtotal) represents the total area of the triangle defined by points B, C and D, and A(BCDsolid) represents the area of the triangle defined by the points B, C and D that is occupied by the solid material. The solid material, in the region adjacent to the upper half of a contour line 40, has an increased silver content.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to metal-ceramic substrates and electronic components comprising metal-ceramic substrates.

[0002] Metal-ceramic substrates play an important role in the field of power electronics. They are a key element when constructing electronic components, ensuring the rapid dissipation of large amounts of heat during their operation. Metal-ceramic substrates typically consist of a ceramic layer and a metal layer bonded to the ceramic layer.

[0003] Several methods for bonding a metal layer to a ceramic layer are known from the prior art. In the so-called DCB ("direct copper bonding") method, copper is reacted with a reactive gas (usually oxygen) to provide the surface of a copper foil with a copper compound (usually copper oxide) that has a lower melting point than copper. When the copper foil treated in this way is applied to a ceramic body and the composite is heated, the copper compound melts and wets the surface of the ceramic body so that a stable cohesive bond is achieved between the copper foil and the ceramic body. This method is described, for example, in U.S. Pat. No. 3,744,120 (A) or German Patent No. 2,319,854 (C2).

[0004] In an alternative method, metal foils can be bonded to ceramic bodies at temperatures of approximately 650-1000°C. A specific solder is used, containing a metal (usually silver) with a melting point of at least 700°C and an active metal. The role of the active metal is to react with the ceramic material, thus facilitating bonding of the ceramic material to the remaining solder and forming a reaction layer, while the metal with a melting point of at least 700°C serves to bond the reaction layer to the metal foil. For example, Patent No. 4812985 (B2) proposes bonding copper foil to a ceramic body using a solder containing 50-89 weight percent silver, copper, bismuth, and an active metal. This method allows for secure attachment of the copper foil to the ceramic body. Alternatively, silver-free solders can be used to bond metal foils to the ceramic body. These solders are based, for example, on a high-melting-point metal (especially copper), a low-melting-point metal (such as bismuth, indium, or tin), and an active metal (such as titanium). Such a technique is proposed, for example, in DE 102017114893 A1, which essentially results in a new and independent class of compounds, since the basis of the solder used is formed by another metal (copper instead of silver), leading to changes in the material properties and adaptation with regard to other solder constituents and modified joining conditions.

[0005] When constructing electronic components, chips are typically mounted on metal-ceramic substrates. Mounting a chip on a metal-ceramic substrate typically requires providing silver-containing contact areas in the areas of the metal-ceramic substrate where the chip will be mounted. Providing silver-containing contact areas allows the chip to be more easily connected to the metal-ceramic substrate using common processes such as sintering or soldering. To create the contact areas, the metal-ceramic substrate is typically first treated in some areas with an etching solution to form the desired structuring. Then, in some areas, the contact areas are provided by applying a silver-containing coating to the surface of the structured metal-ceramic substrate.

[0006] Metal-ceramic substrates manufactured in this way are typically exposed to large temperature changes during operation as part of electronic components. During interruptions, temperatures can drop to, for example, -20°C or below, depending on the environment, while the temperature of the metal-ceramic substrate can easily rise to over 150°C during operation. Metal-ceramic substrates are regularly exposed to these temperature differences. Due to the different thermal expansion coefficients of metal and ceramic, repeated temperature changes can cause the metal layer to peel off (delaminate) from the ceramic body, resulting in performance degradation. Therefore, high thermal shock resistance is an important criterion for the suitability of metal-ceramic substrates for electronics applications, especially power electronics applications.

[0007] Therefore, it is desirable to further improve the thermal shock resistance of metal-ceramic substrates.

[0008] It is therefore an object of the present invention to provide a metal-ceramic substrate with improved resistance to thermal shock.

[0009] This object is achieved by a metal-ceramic substrate according to claim 1. The invention therefore relates to a metal-ceramic substrate, a) a ceramic body having a primary boundary surface; b) a metal layer having a major interface, the metal layer being bonded to the ceramic body at a surface thereof, the metal layer comprising: (i) solid materials in some areas and (ii) a metal layer including a structured region including a non-solid material in some regions; c) a contact region comprising silver disposed on the metal layer; the structured region has a geometric shape that, in a cross section through the metal-ceramic substrate perpendicular to the major interface of the ceramic body, satisfies the following requirements: A(BCD solid ) / A(BCD total )>70%, During the ceremony, A(BCD total ) is the total area of the triangle described by points B, C, and D, A(BCDsolid ) is the area of the triangle described by points B, C, and D that is occupied by the solid material, Points B, C and D are determined as follows: 1. A line of best fit between the ceramic body and the metal layer is determined; 2. A contour line separating solid material from non-solid material is determined; 3. A point A is determined on the perpendicular to the best fit line where the perpendicular to the best fit line intersects with the contour line at a distance of 150 μm from the best fit line; 4. A point B is determined on the perpendicular to the best fit line where the perpendicular to the best fit line intersects with the contour line at a distance of 80 μm from the best fit line; 5. On the line passing through points A and B, point C is determined where the line intersects with the line of best fit; 6. On the perpendicular line passing through point B to the line of best fit, point D is determined where the perpendicular line intersects the line of best fit; A metal-ceramic substrate is provided, wherein a contour line extends from a major boundary surface of the metal layer to a major boundary surface of the ceramic body, the contour line having an upper half and a lower half, the upper half of the contour line extending from the major boundary surface of the metal layer toward the major boundary surface of the ceramic body, and the lower half of the contour line extending from the major boundary surface of the ceramic body toward the major boundary surface of the metal layer, and wherein the solid material in the region adjacent the upper half of the contour line has a higher silver content than the region adjacent the lower half of the contour line.

[0010] Furthermore, the present invention relates to electronic components comprising such metal-ceramic substrates.

[0011] A metal-ceramic substrate according to the present invention comprises a ceramic body having a major interface.

[0012] The ceramic body is preferably a body made of ceramic. The body can have any geometric shape, but is preferably designed as a rectangular parallelepiped. The ceramic body has boundary surfaces, and in the case of a rectangular parallelepiped, has six boundary surfaces. The main boundary surface is preferably referred to herein as the boundary surface (particularly very preferably the boundary surface with the largest area) that is bonded to the metal layer at the surface. The main boundary surface is particularly preferably the boundary surface (particularly very preferably the boundary surface with the largest area) that is bonded to the metal layer with the structured region at the surface, and particularly very preferably the boundary surface (particularly the boundary surface with the largest area) that is bonded to the metal layer at the surface where the silver-containing contact region is located. The main boundary surface is preferably located in the main extension plane of the ceramic body or extends parallel to it. The main extension plane of the ceramic body is therefore preferably understood to be a plane that extends parallel to or surrounds the main boundary surface of the ceramic body.

[0013] The ceramic of the ceramic body is preferably an insulating ceramic. According to a preferred embodiment, the ceramic is selected from the group consisting of oxide ceramics, nitride ceramics, and carbide ceramics. According to a further preferred embodiment, the ceramic is selected from the group consisting of metal oxide ceramics, silicon oxide ceramics, metal nitride ceramics, silicon nitride ceramics, boron nitride ceramics, and boron carbide ceramics. According to a particularly preferred embodiment, the ceramic is selected from the group consisting of aluminum nitride ceramics, silver nitride ceramics, and aluminum oxide ceramics (such as ZTA ("zirconia toughened alumina") ceramics). According to yet another very particularly preferred embodiment, the ceramic body comprises (1) at least one element selected from the group consisting of silicon and aluminum, (2) at least one element selected from the group consisting of oxygen and nitrogen, optionally (3) at least one element selected from the group consisting of (3a) rare earth metals, (3b) metals of Group 2 of the Periodic Table of the Elements, (3c) zirconium, (3d) copper, (3e) molybdenum, and (3f) silicon, and optionally (4) unavoidable impurities. According to yet another very particularly preferred embodiment, the ceramic body is free of bismuth, gallium, and zinc.

[0014] The ceramic body preferably has a thickness in the range of 0.05 to 10 mm, more preferably in the range of 0.1 to 5 mm, and particularly preferably in the range of 0.15 to 3 mm.

[0015] A metal-ceramic substrate according to the present invention comprises a metal layer having a major interface, the metal layer being bonded at a surface to a ceramic body, the metal layer comprising structured regions comprising (i) solid material in some regions and (ii) non-solid material in some regions.

[0016] The metal layer has a boundary surface. The metal layer has a main boundary surface. The main boundary surface is preferably referred to herein as the boundary surface (particularly and very preferably the boundary surface with the largest area) that is located opposite the ceramic body. The main boundary surface is therefore preferably referred to as the boundary surface (particularly and very preferably the boundary surface with the largest area) where the silver-containing contact area is located. The main boundary surface is preferably located in the main extension plane of the metal layer or extends parallel to it. The main extension plane of the metal layer is therefore preferably understood to be a plane that extends parallel to or surrounds the main boundary surface of the metal layer. The main boundary surface of the metal layer preferably extends parallel to the main boundary surface of the ceramic body, and particularly preferably is spaced apart from it.

[0017] The metal layer is preferably intimately bonded to the ceramic body. According to a preferred embodiment, the metal layer is bonded to the ceramic body by a DCB (direct copper bonding) process. According to a further preferred embodiment, the metal layer is bonded to the ceramic body by a brazing process. The brazing process can be, for example, an AMB (active metal brazing) process, preferably using a silver-free brazing alloy (the silver content is, for example, less than 1.0 weight percent, based on the solid content of the brazing alloy) or a silver-containing brazing alloy (the silver content is, for example, at least 50 weight percent, based on the solid content of the brazing alloy). Thus, the metal layer may comprise a bonding layer in contact with the ceramic body. The bonding layer can be, for example, a solder layer (particularly a brazing layer) or a diffusion layer.

[0018] The metal layer is bonded to the ceramic body at the surface. Therefore, the metal layer is preferably bonded to the main boundary surface of the ceramic body at the surface. The metal layer is preferably not bonded to the entire main boundary surface of the ceramic body. In particular, the main boundary surface of the ceramic body can be larger than the surface of the metal layer bonded to the ceramic body. In these cases, the main boundary surface of the ceramic body protrudes. In addition, the metal layer is preferably structured. Structured portions are preferably understood to mean recesses in the metal layer that separate individual parts of the metal layer from each other and thus electrically insulate them. Such structured portions are usually made using etching techniques.

[0019] The metal layer thus comprises a structured region. A structured region is understood to be a part of the metal layer that comprises a structure. The structure is preferably a recess in the metal layer. The main boundary surface of the metal layer therefore comprises the metal of the metal layer interrupted by the recess in the structured region.

[0020] The structured region comprises regions containing solid material and regions containing non-solid material.

[0021] The region comprising the solid material preferably contains (i) the metal of the metal layer (optionally including the bonding layer, if present) and (ii) the metal of the contact region (particularly silver).

[0022] The region containing the non-solid material preferably contains a gaseous material. Therefore, the non-solid material preferably contains a gaseous material. The non-solid material is preferably a gaseous material that fills the recesses of the metal layer. This gaseous material is usually derived from the ambient atmosphere. Therefore, the gaseous material preferably contains at least one element selected from the group consisting of nitrogen, oxygen, and rare gases. The gaseous material is particularly preferably a mixed gas, in particular air.

[0023] According to a preferred embodiment, the recesses extend in a direction perpendicular to the major boundary surface of the ceramic body from the major boundary surface of the ceramic body to the major boundary surface of the metal layer, and the recesses form channels that are preferably filled with the non-solid material to at least 50 volume percent, more preferably at least 80 volume percent, even more preferably at least 90 volume percent, particularly preferably at least 95 volume percent, very particularly preferably at least 99 volume percent, and especially completely.

[0024] The metal layer preferably comprises at least one metal selected from the group consisting of copper, aluminum, and molybdenum. According to a particularly preferred embodiment, the metal layer comprises at least one metal selected from the group consisting of copper and molybdenum. According to a very particularly preferred embodiment, the metal layer comprises copper. According to a further preferred embodiment, the metal layer consists of copper and unavoidable impurities. According to a further preferred embodiment, the proportion of copper is at least 60 weight percent, more preferably at least 65 weight percent, even more preferably at least 70 weight percent, and particularly preferably at least 75 weight percent, based on the total weight of the metal layer (preferably including any bonding layer that may be present).

[0025] According to a preferred embodiment, the metal layer is produced by tightly bonding a copper foil (preferably a high-purity copper foil) to the ceramic body. According to a preferred embodiment, the bonding can be performed by a DCB (direct copper bonding) process or a brazing process. The brazing process can be, for example, an AMB (active metal brazing) process, preferably using a silver-free brazing alloy (the silver content is, for example, less than 1.0 weight percent based on the solid content of the brazing alloy) or a silver-containing brazing alloy (the silver content is, for example, at least 50 weight percent based on the solid content of the brazing alloy). In this case, the metal layer may contain, in addition to copper from the copper foil, metal from the bonding layer, in particular metal from the solder layer (e.g., brazing layer) or diffusion layer.

[0026] The metal layer preferably has a thickness in the range of 0.01 to 10 mm, particularly preferably in the range of 0.03 to 5 mm, very particularly preferably in the range of 0.05 to 3 mm.

[0027] The metal-ceramic substrate according to the present invention includes a contact area containing silver disposed on the metal layer. The contact area preferably serves to facilitate connection of a chip to the metal layer. The chip is preferably bonded to the metal layer by sintering, soldering, or adhesive bonding. In particular, since attaching a chip to the metal of the metal layer of the metal-ceramic substrate is not easily possible, the metal layer is preferably provided with a contact area. The contact area is preferably made of silver or a silver-containing alloy. In the case of a silver-containing alloy, it contains at least 50 weight percent silver, based on the weight of the silver alloy. Preferably, the contact area is provided in the metal layer of the metal-ceramic substrate at all positions where a chip will later be mounted on the metal-ceramic substrate. The contact area can be formed on the metal layer of the metal-ceramic substrate using various techniques. For example, the contact area can be provided by depositing a silver-containing layer. The deposition of the silver-containing layer is preferably performed chemically (e.g., electrochemically) or physically. The chemical deposition of the silver-containing layer can be performed, for example, galvanically or without the use of electric current. Chemical deposition of the silver-containing layer without electric current is preferred by applying a silver-containing solution with charge exchange between the metals, in which the metal of the metal layer partially dissolves while the silver in the solution deposits. According to a preferred embodiment, the silver-containing solution contains a silver salt, particularly preferably silver nitrate. According to a particularly preferred embodiment, the silver-containing solution is an acidic solution of silver nitrate, particularly preferably a nitric acid solution of silver nitrate. Physical deposition of the silver-containing layer can be carried out, for example, by vapor deposition. Preferred methods of vapor deposition are, in particular, electron beam deposition, laser beam deposition, arc discharge deposition, or cathode sputtering.

[0028] The structured regions of the metal layer of the metal-ceramic substrate have the geometries described herein, where the geometries of the structured regions are determined in a cross section through the metal-ceramic substrate perpendicular to the major interface of the ceramic body.

[0029] The structured region of the metal-ceramic substrate has a geometric shape that, in a cross section through the metal-ceramic substrate perpendicular to the major interface of the ceramic body, satisfies the following requirements: A(BCD solid ) / A(BCD total )>70%, During the ceremony, A(BCD total ) is the total area of the triangle described by points B, C, and D, A(BCD solid ) is the area of the triangle described by points B, C, and D occupied by the solid material. According to a preferred embodiment, the structured region of the metal-ceramic substrate has a cross section through the metal-ceramic substrate perpendicular to the main interface of the ceramic body, such that the ratio A(BCD solid ) / A(BCD total ) >75%, more preferably >80%, even more preferably >85%, particularly preferably >90%, very particularly preferably >95%.

[0030] According to a further preferred embodiment, the structured region of the metal-ceramic substrate has a ratio A(BCD solid ) / A(BCD total ) is preferably in the range of 75 to 100%, more preferably in the range of 90 to 100%, and most preferably in the range of 95 to 99%.

[0031] To determine the triangle described by points B, C, and D, a cross section of the structured region of the metal layer of the metal-ceramic substrate is observed. The cross section extends perpendicular to the main boundary plane of the ceramic body. Preferably, the cross section is observed by cutting the metal-ceramic substrate perpendicular to the main boundary plane of the ceramic body and photographing the cross section thus obtained using a scanning electron microscope.

[0032] Points B, C and D of the triangle can be determined in cross section as described below. For illustrative purposes, refer to Figures 1 and 2 as an example. [Brief explanation of the drawings]

[0033] [Figure 1] FIG. 1 shows a schematic diagram of a typical metal-ceramic substrate. [Figure 2] FIG. 2 shows diagrammatically a metal-ceramic substrate according to the invention having a structured region in which the solid material in the region adjacent to the upper half of the contour line has a higher silver content than in the region adjacent to the lower half of the contour line. [Figure 3] FIG. 3 shows a portion of a cross section through a metal-ceramic substrate according to the present invention. [Figure 4] FIG. 4 shows an example of an optical microscope image of a cross section of a detail of a structured area of the copper layer of a copper-ceramic substrate according to Example 1. [Figure 5] FIG. 5 shows an example of an optical microscope image of a cross section of a detail of a structured area of the copper layer of a copper-ceramic substrate according to Comparative Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0034] The metal-ceramic substrate 1 shown in FIG. 1 comprises a ceramic body 10. The ceramic body 10 has a major interface 15. The metal-ceramic substrate 1 comprises a metal layer 20. The metal layer 20 has a major interface 24 parallel to the major interface 15 of the ceramic body 10 on the top surface opposite the major interface 15 of the ceramic body 10. The metal layer 20 is bonded to the major interface 15 of the ceramic body 10 at its surface. In the embodiment according to FIG. 1, the metal-ceramic substrate 1 further comprises a further metal layer 200 bonded to the ceramic body 10 at its surface. The metal layer 20 has contact areas 8 comprising silver. The metal layer 20 comprises a structuring portion, which is formed by recesses 22 in the metal layer 20. The recesses 22 contain a non-solid material. The structured area 4 comprises the metal of the metal layer 20 and the recesses 22 in some areas. Thus, in some areas, structured region 4 includes a solid material 50 formed by the metal of metal layer 20 and a non-solid material (e.g., a gaseous material) filling recesses 22. The gaseous material is typically ambient air. Solid material 50 is separated from the non-solid material of recesses 22 by contour lines 40. Major interfaces 24 of metal layer 20 include the metal of metal layer 20 interrupted by recesses 22 in the structured region. Recesses 22 extend from major interfaces 24 of metal layer 20 to major interfaces 15 of ceramic body 10 in a direction perpendicular to major interfaces 15 of ceramic body 10, preferably forming channels that are completely or mostly filled with the non-solid material.

[0035] The metal-ceramic substrate shown in Figure 2 has the same basic structure as the metal-ceramic substrate shown in Figure 1. A contour line 40 has an upper half and a lower half. The upper half of contour line 40 extends from the major interface 24 of metal layer 20 toward the major interface 15 of ceramic body 10. The lower half of contour line 40 extends from the major interface 15 of ceramic body 10 toward the major interface 24 of metal layer 20. Solid material 50 includes silver 60 in the region adjacent to the upper half of contour line 40. In the region adjacent to the lower half of contour line 40, the solid material includes no or less silver 60.

[0036] In a portion of a cross section through a metal-ceramic substrate according to the invention shown in Figure 3, a portion of the structured region is visible. The region of the ceramic body 10 that is bonded at its surface to a region of the metal layer 20 is shown. A contour line 40 separates the non-solid material of the recess 22 in the metal layer 20 from the solid material 50.

[0037] The determination of points B and C of line BC in the cross section is preferably done in several steps.

[0038] In a first step, a best fit line 30 is determined between the ceramic body 10 and the metal layer 20. For this purpose, an area of the ceramic body 10 and an area of the metal layer 20 are optically determined, and the best fit line 30 is defined as the boundary between the ceramic body 10 and the metal layer 20 that can be observed in cross section.

[0039] In a second step, a contour line 40 is determined that separates the solid material 50 from the non-solid material of the recess 22. The solid material 50 is determined optically and is typically the material of the metal layer 20. The non-solid material is also determined visually. The non-solid material is typically a gaseous material that fills the structuring of the metal layer 20 as recess 22.

[0040] In a third step, a point A on the perpendicular to the best fit line 30 at a distance of 150 μm from the best fit line 30 where the perpendicular to the best fit line 30 intersects with the contour line 40 is determined.

[0041] In a fourth step, a point B on the perpendicular to the best fit line 30 at a distance of 80 μm from the best fit line 30 where the perpendicular to the best fit line 30 intersects with the contour line 40 is determined.

[0042] In the fifth step, a point C on the line passing through points A and B where the line intersects with the line of best fit 30 is determined.

[0043] In a sixth step, on the perpendicular line passing through point B to the best fit line 30, point D where the perpendicular line intersects with the best fit line 30 is determined.

[0044] Cutting the metal-ceramic substrate perpendicular to the main interface of the ceramic body and recording the cross section thus obtained by optical microscopy (incident light / bright field) is preferably carried out as described below.

[0045] In the first step, a 100 mm sample is first taken from the metal-ceramic substrate to be inspected. 2 ~400mm 2 A rectangular sample blank with a rectangular base was cut out by sawing perpendicular to the plane defined by the main interface of the ceramic body of the metal-ceramic substrate using a diamond saw blade and lubricant (Exakt) at a low rotational speed. The sample blank thus had a sample surface to be investigated. This sample surface therefore extended perpendicular to the plane defined by the main interface of the ceramic body of the metal-ceramic substrate before sawing. It therefore comprised a portion of the ceramic body and a portion of the metal layer (including the optional bonding layer). The sample blank was first embedded in a mold containing low-shrinkage epoxy resin (Caldo-Fix, Struers), with the sample surface oriented perpendicular to the mold wall. The epoxy resin was then cured at 75°C in a drying cabinet. After curing, the sample surface of the sample blank was mechanically polished with an automatic polishing machine (Tegrapole, Struers) to achieve a roughness of 1 μm or less.

[0046] In a second step, structured regions, comprising solid material in some areas and non-solid material in some areas, are identified in the metal layer using an optical microscope (Leica, DM6000M, incident light / bright field) at 200x magnification in the analysis zone. The solid and non-solid materials can be clearly distinguished in the structured regions by their different colors.

[0047] Area A(BCD solid ) and A(BCD total) is preferably determined in a routine manner, for example using image evaluation software (eg IMS Client, Imagic).

[0048] Preferably, the term "in cross sections" as used herein refers to a (preferably representative) total number of cross sections, particularly preferably at least 10 cross sections, very particularly preferably not more than 20 cross sections, in particular 10 cross sections. The cross sections preferably extend parallel to one another and are evenly spaced from one another.

[0049] Here, the ratio A(BCD) for the observed metal-ceramic substrate is solid ) / A(BCD total To determine , the following procedure is preferably used: 1. At least 10, particularly preferably 10, different cross sections of the structured area are examined. 2. The ratio A(BCD) for each of these sections solid ) / A(BCD total ) is required. 3. The ratio A(BCD) for each of these sections solid ) / A(BCD total ) and the ratio A(BCD) for the observed metal-ceramic substrates solid ) / A(BCD total ) is obtained.

[0050] According to a preferred embodiment, the ratio A(BCD) is greater than or equal to 10 different cross sections of the at least one structured area of the metal layer, more preferably less than or equal to 20 different cross sections of the at least one structured area of the metal layer, and most preferably less than or equal to 10 different cross sections of the at least one structured area of the metal layer. solid ) / A(BCD total The sample standard deviation (SSD) of the sample (SSD) is 10% or less, more preferably 7% or less, particularly preferably 5% or less, and very particularly preferably 2% or less. The sample standard deviation (SSD) is calculated using the following formula:

[0051]

number

[0052]

number

[0053] According to the invention, in a cross section through the metal-ceramic substrate perpendicular to the major boundaries of the ceramic body, the structured region has a geometric shape in which a contour line extends from the major boundaries of the metal layer to the major boundaries of the ceramic body, the contour line having an upper half and a lower half, the upper half of the contour line extending from the major boundaries of the metal layer toward the major boundaries of the ceramic body, and the lower half of the contour line extending from the major boundaries of the ceramic body toward the major boundaries of the metal layer, and the solid material in the region adjacent the upper half of the contour line has a higher silver content than the region adjacent the lower half of the contour line.

[0054] Thus, in accordance with the present invention, the contour line extends from the major boundary surface of the metal layer to the major boundary surface of the ceramic body. The contour line preferably does not extend along the major boundary surface of the ceramic, and does not extend along the major boundary surface of the metal layer. Thus, the contour line preferably extends over an area that does not include the major boundary surface of the ceramic or the major boundary surface of the metal layer.

[0055] The contour line has an upper half and a lower half, the upper half of the contour line extending from the major boundary surface of the metal layer toward the major boundary surface of the ceramic body, and the lower half of the contour line extending from the major boundary surface of the ceramic toward the major boundary surface of the metal layer.

[0056] According to the invention, the solid material in the region adjacent to the upper half of the contour line has a higher silver content than the region adjacent to the lower half of the contour line. According to a preferred embodiment, the ratio of the silver content of the solid material in the region adjacent to the upper half of the contour line to the silver content of the solid material in the region adjacent to the lower half of the contour line is less than 0.8, more preferably less than 0.5, even more preferably less than 0.3, particularly preferably less than 0.1, and very particularly preferably less than 0.05.

[0057] The region of the solid material bordered by the contour line preferably has a width in the range of 0.3 to 1.0 μm, particularly preferably in the range of 0.5 to 0.6 μm, and very particularly preferably 0.5 μm. Thus, the contour line preferably represents the outline of the solid material, and the composition of the solid material (including the silver content) is preferably determined using the method described above in a region bounded by (i) the major boundary surface of the metal layer, (ii) the major boundary surface of the ceramic body, (iii) the contour line, and (iv) a translation of the contour line toward the solid material of 0.3 to 1.0 μm, particularly preferably 0.5 to 0.6 μm, and very particularly preferably 0.5 μm. The contour line is preferably divided into upper and lower halves midway between the major boundary surface of the metal layer and the major boundary surface of the ceramic body, with the upper half of the contour line extending from the major boundary surface of the metal layer toward the major boundary surface of the ceramic body, and the lower half of the contour line extending from the major boundary surface of the ceramic body toward the major boundary surface of the metal layer. The area of the solid material being measured therefore consists of an upper half located above the contour line and a lower half located below the contour line.

[0058] The silver content of the solid material in the region adjacent the upper half of the contour line and the silver content of the solid material in the region adjacent the lower half of the contour line are preferably determined by energy dispersive X-ray spectroscopy (EDX) in combination with a scanning electron microscope (SEM) (SEM-EDX).

[0059] In SEM-EDX, a focused primary electron beam is guided (screened) point-by-point over the sample surface. The scattered electrons are detected using a detector, and the number of electrons per pixel results in a grayscale microscopic image of the sample surface. Furthermore, the primary electron beam excites the sample to emit characteristic X-ray radiation, and the elements and their weight percentages in the sample can be determined by analyzing the energy spectrum using an EDX detector.

[0060] For the examination, a scanning electron microscope (JSM-6060 SEM, JEOL Ltd) equipped with a silicon drift EDX detector (NORAN, Thermo Scientific Inc.) and analysis software (Pathfinder Mountaineer EDS System, e.g., version 2.8, Thermo Scientific Inc.) can be used. For scanning electron microscopy, the following settings can be used: magnification: 200x, acceleration voltage: 10 kV, working distance: 10 mm, spot size: 50-60 (adjusted to reach 25% + / - 5% of the EDX detector dead time). EDX spectra can be detected using the following settings of the EDX detector: live time: 30 s, speed: automatic, low energy cutoff: 100 keV, high energy cutoff: automatic (per SEM acceleration voltage). Depending on the selected magnification and the thickness of the metal layer, several SEM-EDX measurements may be required to image the entire structured area.

[0061] The silver content is measured in an area adjacent to the upper half of the contour line and in an area adjacent to the lower half of the contour line at at least five, and particularly preferably ten, representative positions within each area, and the silver content is preferably understood to be the arithmetic mean value of each individual measurement.

[0062] Surprisingly, it has been found that metal-ceramic substrates having a geometry according to the present invention have improved thermal shock resistance compared to prior art metal-ceramic substrates. These metal-ceramic substrates contain a high percentage of solid material within the metal layer at the interface with the surface of the ceramic body. In contrast, it has been found that the percentage of solid material within the metal layer at the interface with the surface of the ceramic body is significantly lower in prior art metal-ceramic substrates, provided they have a contact area comprising silver disposed on the metal layer.

[0063] Without being bound by any explanation, this may be due to the fact that in the prior art, manufactured metal-ceramic substrates are typically first structured and then silver-plated on the surface to create contact areas, but the already structured areas of the metal-ceramic substrate surface are only insufficiently masked during silver plating. For this purpose, areas of the structured metal-ceramic substrate surface that will not be coated with silver are typically first masked before silver plating. A film (e.g., a dry film) is typically used for masking. This film spans the structured areas of the metal-ceramic substrate, so that the structured areas are covered but not completely lined, especially in areas close to the ceramic body. Subsequent silver plating is typically performed by immersing the structured and masked metal-ceramic substrate in a bath containing a solution containing silver ions. The silver-ion-containing solution can wash under the masking film, so that it comes into direct contact with the underlying structured areas. During the silver plating process, metal ions are electrochemically dissolved from the metal layer of the metal-ceramic substrate in the structured area and replaced by silver ions. It has been shown that the dissolution of metal ions from the metal layer and the deposition of silver ions occur in spatially separated regions near the ceramic body. Therefore, while silver is often deposited directly on the surface of the structured area, metal ions are preferably released from regions closer to the ceramic body (up to a distance of about 50 μm from the ceramic body surface). As a result, the regions of the structured area closer to the ceramic body are gradually removed over time with the silver ion-containing solution. This results in the removal of solid material, particularly the metal of the metal foil, from the metal foil in the region closer to the ceramic body, thus creating a weak point for peeling of the metal layer from the ceramic body, which adversely affects thermal shock resistance. Therefore, the removal of solid material in the structured area can be attributed to the lack of lining of the structured area with a masking film. However, according to the present invention, a structured area containing a sufficient amount of solid material in the region closer to the ceramic body can be created, thereby preventing peeling of the metal layer from the ceramic body and achieving improved thermal shock resistance.

[0064] The solid material contains silver in the region adjacent to the upper half of the contour line. This is because, according to one embodiment, a masking is applied by a printing process before silver plating. Since the structure of the metal-ceramic substrate usually has a curved geometry, the structure is (almost) completely covered with the masking in the region close to the ceramic body, improving thermal shock resistance. In contrast, regions of the structure further away from the ceramic body are usually not completely masked and are therefore at least partially coated with silver in the subsequent silver plating step.

[0065] According to a preferred embodiment, the metal-ceramic substrate comprises a further (second) metal layer bonded to the ceramic body at its surface. The further metal layer is preferably bonded to the ceramic body at its surface on the side opposite (preferably extending parallel to) the main boundary surface. The further (second) metal layer may be of the same nature as the (first) metal layer or may differ in nature from the (first) metal layer. For the nature of the further (second) metal layer, reference is made to the above explanation for the (first) metal layer.

[0066] The metal-ceramic substrate according to the invention can be used in particular for applications in electronics, especially in the field of power electronics.

[0067] The present invention therefore also provides an electronic component comprising a metal-ceramic substrate according to the present invention.

[0068] According to a preferred embodiment, an electronic component comprises a metal-ceramic substrate according to the invention and at least one chip. The at least one chip is preferably bonded at the surface to a contact area comprising silver arranged on the (first) metal layer. Thus, the electronic component preferably comprises a chip in contact with the (first) metal layer of the metal-ceramic substrate via the contact area comprising silver.

[0069] According to a further preferred embodiment, the metal-ceramic substrate of the electronic component comprises a further (second) metal layer, which is preferably bonded to the ceramic body at its surface, preferably at a boundary surface of the ceramic body opposite to (preferably extending parallel to) the main boundary surface of the ceramic body.

[0070] According to a further preferred embodiment, the electronic component comprises a base plate, which is preferably bonded at its surface to the further (second) metal layer of the metal-ceramic substrate, which may alternatively be formed as a heat sink.

[0071] According to a further preferred embodiment, the electronic component comprises a metal-ceramic substrate comprising a (first) metal layer and a further (second) metal layer (the further metal layer is preferably bonded at its surface to the interface opposite the main interface of the ceramic body), a base plate and at least one chip, wherein the at least one chip is bonded at its surface to the first metal layer of the metal-ceramic substrate via a contact area comprising silver arranged on the metal layer, and the base plate is bonded at its surface to the further (second) metal layer of the metal-ceramic substrate.

[0072] The metal-ceramic substrate according to the invention can be obtained by various manufacturing processes.

[0073] According to a preferred embodiment, the method is a method for manufacturing a metal-ceramic substrate provided with a structuring and a contact area comprising silver, said method comprising the steps of: a) providing a metal-ceramic substrate, the metal-ceramic substrate comprising: a1) a ceramic body; a2) a metal layer bonded to the ceramic body at a surface thereof; b) structuring the metal layer; c) applying a mask to the structured metal layer by applying a liquid medium containing a masking agent to some areas of the structured metal layer and allowing the masking agent to solidify; d) depositing a silver-containing layer on the unmasked areas of the structured metal layer to obtain contact areas comprising silver; e) removing the masking; Includes.

[0074] Therefore, in step a), it is preferred to first provide a metal-ceramic substrate.

[0075] The metal-ceramic substrate comprises a ceramic body and a metal layer bonded to the ceramic body at a surface thereof. The metal-ceramic substrate can be a standard metal-ceramic substrate. The ceramic body and metal layer can have compositions as described above for the metal-ceramic substrate. The metal layer can preferably be intimately bonded to the ceramic body as described above for the metal-ceramic substrate.

[0076] In step b), the metal layer is preferably structured first.

[0077] The structuring is preferably understood to mean recesses in the metal layer that separate individual parts of the metal layer from one another and thus electrically insulate them. The structuring thus preferably exposes regions of the ceramic body. Such structuring is usually produced using etching techniques. For example, an etching mask can first be applied to the metal layer. The etching mask serves to protect the masked areas of the metal layer of the metal-ceramic substrate from etching in the etching step. This ensures that only the unmasked areas of the metal layer of the metal-ceramic substrate that are intended to be structured are accessible for etching. The etching mask is therefore produced so that etching of the masked areas of the metal layer does not occur in the etching step. The type of etching mask is not further limited. The etching mask can be, for example, a standard negative or positive mask. Standard etching resists can be used to produce the etching mask. These etch resists preferably contain a curable polymer (e.g., a photocurable polymer) and can be applied to the metal layer, for example, as a film (e.g., as a dry film) or as a liquid (e.g., by printing or spraying). After application, the etch resist can be treated in a suitable manner (for example, cured by irradiation with light) to obtain an etching mask. According to one possible embodiment, a photosensitive film is applied to the metal layer of the metal-ceramic substrate and then exposed in the areas to be masked to obtain an etching mask. The unexposed areas of the photosensitive film can then be removed in a conventional manner (for example, with a sodium carbonate solution). After applying the etching mask to the metal layer, it is preferable to etch the unmasked areas of the metal layer to obtain a structuring. Etching is preferably carried out using standard, skilled methods. Therefore, etching is preferably carried out using a standard etching solution. According to a preferred embodiment, the etching solution is selected from the group consisting of FeCl3 etching solution and CuCl2 etching solution.If necessary, for example, to structure the unmasked areas of the optionally included bonding layer, an additional etching solution can be used. According to a preferred embodiment, the additional etching solution can be selected from the group consisting of an etching solution containing hydrogen peroxide and an etching solution containing ammonium persulfate. For example, the additional etching solution can be an etching solution containing ammonium fluoride and fluoroboric acid (e.g., HBF) and hydrogen peroxide and / or ammonium persulfate.

[0078] Preferably, after etching the unmasked areas of the metal layer while preserving the structuring, the etching mask is removed. The etching mask can be removed by standard methods. For this purpose, the metal-ceramic substrate can be treated with an alkaline solution (e.g., 2.5% sodium hydroxide solution) to remove the etching mask.

[0079] In step c), a mask is preferably applied to the structured metal layer by applying a liquid medium containing a masking agent to some areas of the structured metal layer and allowing the masking agent to solidify.

[0080] The masking serves to protect the masked areas of the metal layer from the deposition of the silver-containing layer in step d), thereby ensuring that the silver-containing layer is deposited only on the unmasked areas of the metal layer of the metal-ceramic substrate. Thus, the masking is designed so that the silver-containing layer cannot be deposited on the masked areas of the metal layer of the metal-ceramic substrate.

[0081] According to a preferred embodiment, the structured metal layer to which the masking is applied also comprises structured regions, particularly preferably structured regions between the main boundaries of the metal layer and the main boundaries of the ceramic body, and therefore, in particular, the regions of the metal layer in the vicinity of the ceramic body are also provided with a masking to protect them from dissolution during deposition of the silver-containing layer, in particular when they come into contact with the silver-ion-containing solution in step d).

[0082] To apply the masking, a liquid medium containing a masking agent is applied to some areas of the structured metal layer and the masking agent is allowed to solidify.

[0083] The liquid medium is preferably a medium that is liquid at room temperature and normal pressure. The liquid medium is preferably a medium that contains a polar solvent, particularly preferably water. According to a preferred embodiment, the liquid medium is selected from the group consisting of a solution and a suspension.

[0084] The liquid medium contains a masking agent. The masking agent is preferably designed to be solidifiable. The masking agent is not further limited. According to a preferred embodiment, the masking agent is curable, particularly UV-curable. The UV-curable masking agent preferably contains at least one compound selected from the group consisting of monomers and oligomers. According to a particularly preferred embodiment, the UV-curable masking agent contains at least one compound selected from the group consisting of acrylates, epoxies, and unsaturated polyester resins. The liquid medium preferably further contains a photoinitiator. The photoinitiator may be, for example, a compound that decomposes upon absorbing UV light to form reactive species that can initiate polymerization and curing of the UV-curable masking agent. In addition, the liquid medium may contain other components such as colorants, additives, etc.

[0085] The liquid medium containing the masking agent is applied to some areas of the structured metal layer, for this purpose the liquid medium is preferably applied to areas of the structured metal layer that are masked and protected from the deposition of the silver-containing layer in step d).

[0086] The liquid medium is preferably applied to the structured metal layer by printing, spraying or painting. According to a particularly preferred embodiment, the liquid medium is applied by printing using an inkjet process.

[0087] After applying the liquid medium, the masking agent contained therein is preferably solidified.For this purpose, the masking agent is preferably cured.Curing can be achieved, for example, by irradiating the liquid medium with UV light so that the masking agent (particularly the monomer or oligomer) contained therein is polymerized.

[0088] According to a preferred embodiment, applying a mask to the structured metal layer comprises an additive masking step. The additive masking step refers to the application of a masking agent. According to a further preferred embodiment, applying a mask to the structured metal layer does not comprise a subtractive masking step. The subtractive masking step is understood to mean, in particular, the partial removal of a masking agent applied, for example, in an additive masking step, before depositing a silver-containing layer on the unmasked areas of the structured metal layer in step d) to obtain silver-containing contact areas. According to this preferred embodiment, the liquid medium containing the masking agent is applied only to areas of the structured metal layer on which a silver-containing layer will not be deposited in step d) and, if appropriate, to areas of the ceramic body exposed by recesses in the metal layer that form the structuring. In conventional masking methods, the masking agent is applied to the structured metal layer, preferably as a layer, especially over the entire surface, in an additive masking step, and in a subsequent subtractive masking step, the solidified masking agent is removed in areas of the structured metal layer on which a silver-containing layer will be deposited in the subsequent step. By omitting the subtractive masking step, this preferred embodiment advantageously provides a particularly simple method for producing a metal-ceramic substrate provided with a structuring and a contact area comprising silver.

[0089] According to a preferred embodiment, in step c), a liquid medium comprising a masking agent is applied to the regions of the ceramic body, in particular to the regions of the ceramic body exposed by the recesses of the metal layer forming the structure, and the masking agent is allowed to solidify, thereby also applying a mask to the regions of the ceramic body exposed by the recesses of the metal layer forming the structure. Applying a mask to the exposed regions of the ceramic body can be advantageous in order to protect the exposed regions of the ceramic body from the deposition of a silver-containing layer in step d).

[0090] The application of the mask to the structured metal layer and to the areas of the ceramic body exposed by the recesses in the metal layer forming the structuring can be carried out simultaneously or sequentially.

[0091] To apply the masking to the areas of the ceramic body exposed by the recesses in the metal layer forming the structured portion, a liquid medium as described above for applying the masking to the structured metal layer and an application as described above for applying the masking to the structured metal layer can be used.

[0092] In step d), a silver-containing layer is preferably deposited on the unmasked areas of the structured metal layer to obtain contact areas comprising silver.

[0093] The silver-containing layer is preferably a layer made of silver or a silver alloy, and particularly preferably a layer made of silver. The deposition of the silver-containing layer is preferably carried out chemically (e.g., electrochemically) or physically. Chemical deposition of the silver-containing layer can be carried out, for example, galvanically or without the use of electric current. Chemical deposition of the silver-containing layer without the use of electric current is preferred, by applying a silver-containing solution with charge exchange between the metals, in which the metal of the metal layer partially dissolves while the silver in the solution deposits. According to a preferred embodiment, the silver-containing solution contains a silver salt, particularly preferably silver nitrate. According to a particularly preferred embodiment, the silver-containing solution is an acidic solution of silver nitrate, particularly preferably a nitric acid solution of silver nitrate. The silver concentration in the nitric acid solution can be, for example, in the range of 0.5 to 1.5 g / L, particularly preferably in the range of 0.6 to 1.4 g / L, and very particularly preferably in the range of 0.8 to 1.2 g / L. Physical deposition of the silver-containing layer can be carried out, for example, by vapor deposition. Preferred methods of vapor deposition are, in particular, electron beam deposition, laser beam deposition, arc discharge deposition, or cathode sputtering.

[0094] In step e) the masking is preferably removed.

[0095] The masking can be removed by standard methods. For this purpose, the masking can be exposed to an alkaline solution (e.g., 2.5% sodium hydroxide solution). After removing the masking, the metal-ceramic substrate comprises at least one silver-containing contact area, and the surface of the metal layer that is not provided with the silver-containing contact area is freely accessible.

[0096] The method described herein makes it possible to obtain a structure and a metal-ceramic substrate provided with contact areas containing silver. By creating contact areas containing silver, chips can be more easily connected to the metal-ceramic substrate using common processes such as sintering or soldering. The metal-ceramic substrate thus obtained is characterized by a particularly high resistance to thermal shock.

[0097] Illustrative Embodiments The invention is explained in more detail below using exemplary embodiments, which should not be understood as limiting.

[0098] Example 1: Example 1a - Preparation of structured metal-ceramic substrate: As Example 1, a copper-ceramic substrate was used, in which a ceramic body made of silicon nitride ceramic and having dimensions of 177.8 × 139 × 0.32 mm was bonded to both sides of the ceramic body using an AMB (active metal brazing) process, and the copper-ceramic substrate was first cleaned after production.

[0099] A photosensitive film was then applied to both copper layers of the copper-ceramic substrate using a hot roll laminator. The photosensitive film was then irradiated with 30 mJ / cm2 in each of the masked areas to cure the polymer contained in the photosensitive film and obtain an etching mask. 2 The copper-ceramic substrate was exposed to light with a fluorine-containing solution (fluorine ion content = 160 g / L). The unexposed areas of the photosensitive film were then wet-chemically removed using a sodium carbonate solution (concentration = 10 g / L). After applying the etching mask, the copper-ceramic substrate was rinsed and cleaned. The unmasked areas of the copper layer of the copper-ceramic substrate were then wet-chemically etched. For this purpose, a copper chloride solution (copper ion content = 160 g / L) containing hydrogen peroxide was sprayed onto the copper-ceramic substrate in an etching system. The etching was carried out at a temperature of 50 °C and a spray pressure of 2.8 bar. The etching removed material from the unmasked areas of the copper layer of the copper-ceramic substrate. The copper-ceramic substrate was then rinsed. The unmasked areas of the bonding layer included in the copper-ceramic substrate were then wet-chemically etched as well. For this purpose, an etching solution containing ammonium fluoride, fluoroboric acid, and hydrogen peroxide was sprayed onto the copper-ceramic substrate again in an etching system. The copper-ceramic substrate was then rinsed and dried. The etching mask was then removed using a 2.5% sodium hydroxide solution in a stripping system.

[0100] Example 1b - Preparation of a structured metal-ceramic substrate with a contact area comprising silver: The structured copper-ceramic substrate prepared in Example 1a was provided with contact areas containing silver. For this purpose, a mask was first applied to the structured copper layer of the copper-ceramic substrate (including the structured areas) and to the areas of the ceramic body exposed by the recesses in the copper layer forming the structure (exposed areas of the ceramic body). For this purpose, the structured copper-ceramic substrate was placed in an inkjet printer (MicroCraft C4K7861T, Sense Advanced Technology GmbH) to apply a mask to the structured copper layer (including the structured areas) and the exposed areas of the ceramic body. A liquid medium containing a masking agent (DiPaMAT Etch Resist ER02) was printed onto the silver-free areas of the structured copper layer and the exposed areas of the ceramic body in the structured areas. Then, UV radiation (LED 390 nm, 500 mJ / cm ) was applied. 2 The masking agent was then cured using a masking agent. The silver-free areas of the structured copper layer and the exposed areas of the ceramic body were thus covered with a 30 μm thick masking.

[0101] Thereafter, a silver-containing contact area was deposited on the unmasked area of the copper layer of the copper-ceramic substrate. For this purpose, the copper-ceramic substrate provided with the masking was first pretreated with a first solution containing hydrogen peroxide and sulfuric acid, and then contacted with a silver nitrate solution (silver content = 1.0 g / L). After deposition of the silver-containing contact area, the copper-ceramic substrate was carefully rinsed with water to remove any residue. The masking was then removed using a 2.5% sodium hydroxide solution in a stripping system.

[0102] The resulting copper-ceramic substrate was laser cut into individual parts with dimensions (20.5 x 17.0 mm) which could then be used for further investigation and for the fabrication of electronic components.

[0103] Comparative Example 1: Comparative Example 1a - Preparation of structured metal-ceramic substrate: In Comparative Example 1a, a structured copper-ceramic substrate was prepared similarly to Example 1a.

[0104] Comparative Example 1b - Preparation of a structured metal-ceramic substrate with a contact area containing silver: The structured copper-ceramic substrate prepared in Comparative Example 1a was provided with contact areas containing silver. For this purpose, a mask was first applied to the structured copper layer of the copper-ceramic substrate. For this purpose, a photosensitive film was applied to both etched sides of the structured copper-ceramic substrate using a hot roll laminator. In order to harden the polymer contained in the photosensitive film and obtain the masking, the photosensitive film was applied to each of the masked areas with 30 mJ / cm2. 2 The copper-ceramic substrate was exposed to light with a 1000 W exposure. The unexposed areas of the photosensitive film were then wet-chemically removed using a sodium carbonate solution (concentration = 10 g / L). After applying the masking, the copper-ceramic substrate was rinsed and cleaned again. Silver-containing contact areas were then deposited on the unmasked areas of the copper layer of the copper-ceramic substrate. For this purpose, the copper-ceramic substrate provided with the masking was first pretreated with a first solution containing hydrogen peroxide and sulfuric acid, and then contacted with a silver nitrate solution (silver content = 1.0 g / L). After depositing the silver-containing contact areas, the copper-ceramic substrate was carefully rinsed with water to remove any residues. The masking was then removed in a stripping system using a 2.5% sodium hydroxide solution.

[0105] The resulting copper-ceramic substrate was laser cut into individual parts with dimensions (20.5 x 17.0 mm) which could then be used for further investigation and for the fabrication of electronic components.

[0106] evaluation: The ratio A(BCD) for the copper-ceramic substrates obtained in Example 1 and Comparative Example 1 solid ) / A(BCD total) was determined. For this purpose, as described herein, the copper-ceramic substrates were cut perpendicular to the main boundary surface of each ceramic body, and images of the cross sections thus obtained were taken using an optical microscope. Points A, B, C, and D were determined on the cross sections. The ratio A (BCD) for each of the copper-ceramic substrates was then calculated. solid ) / A(BCD total For this purpose, ten different cross sections of the structured area in the copper layer of the corresponding copper-ceramic substrate were investigated, and the ratio A(BCD) for each of these cross sections was determined. solid ) / A(BCD total ) and calculate the ratio A(BCD solid ) / A(BCD total ) to obtain the ratio A(BCD) for the corresponding copper-ceramic substrate. solid ) / A(BCD total ) was obtained. Furthermore, the standard deviation SSD was calculated.

[0107] Similarly, for the copper-ceramic substrates obtained in Example 1 and Comparative Example 1, the silver content of the region adjacent to the upper half of the contour line and the region adjacent to the lower half of the contour line was determined by energy dispersive X-ray spectroscopy (EDX) combined with scanning electron microscopy (SEM) (SEM-EDX) as described above.

[0108] FIG. 4 shows an example of an optical microscope image of a cross section of a detail of a structured region of the copper layer of a copper-ceramic substrate according to Example 1, and FIG. 5 shows an example of an optical microscope image of a cross section of a detail of a structured region of the copper layer of a copper-ceramic substrate according to Comparative Example 1.

[0109] The results are shown in Table 1.

[0110] [Table 1]

[0111] The thermal shock resistance of the copper-ceramic substrate was tested. For this purpose, a thermal shock resistance test was carried out.

[0112] Thermal shock resistance test: In preparation for the thermal shock resistance test, we first used an ultrasonic microscope (PVA Tepla SAM300) to confirm the integrity of the copper-ceramic substrate. Only copper metal-ceramic substrates that showed no delamination between the ceramic body and the copper layer or other deformations (e.g., cracks) that could result in delamination of the copper layer from the ceramic body were used for the test. To test thermal shock resistance, the copper-ceramic substrates were repeatedly exposed to cold liquid (temperature -65°C, Galden Do2TS) and hot liquid (temperature +150°C, Galden Do2TS) for 5 minutes each in a cycle chamber (ESPEC TSB-2151). The copper-ceramic substrates were rechecked for delamination and other deformations every 1000 cycles using the ultrasonic microscope (PVA Tepla SAM300). The test was terminated after 3000 cycles. The copper-ceramic substrates were then re-examined for delamination and other deformations using the ultrasonic microscope (PVA Tepla SAM300). The state of each copper-ceramic substrate after the thermal shock resistance test was compared with the state of the copper-ceramic substrate before the thermal shock resistance test for delamination and other deformations. Delamination and other deformations (e.g., cracks) were visible as white discolorations in the ultrasound images.

[0113] The results are shown in Table 2.

[0114] [Table 2]

[0115] The results show that the metal-ceramic substrate according to the present invention is clearly superior to the metal-ceramic substrate of Comparative Example 1 in terms of thermal shock resistance.

[0116] Reference Code List 1 Metal-ceramic substrate 4 Structured area 8 Contact area 10 ceramic body 15 Main boundary surface of ceramic body 20 metal layer 22 recess 24 Main interface of metal layer 40 Contour Lines 50 solid materials 60 Silver 200 More Metal Layers

Claims

1. A metal-ceramic substrate, a) a ceramic body having a major boundary surface; b) a metal layer having a major interface, the metal layer being bonded to the ceramic body at a surface thereof, the metal layer comprising: (i) solid materials in some regions and (ii) a metal layer including structured regions including a non-solid material in some regions; c) a contact region comprising silver disposed on the metal layer, the structured region has a geometric shape that, in a cross section through the metal-ceramic substrate perpendicular to the major interface of the ceramic body, satisfies the following requirements: A(BCD ｓｏｌｉｄ ) / A(BCD ｔｏｔａｌ )>70%、 During the ceremony, A (BCD ｔｏｔａｌ ) is the total area of the triangle described by points B, C, and D, A (BCD ｓｏｌｉｄ ) is the area of the triangle described by points B, C, and D occupied by the solid material; Points B, C and D are determined as follows:

1. A line of best fit between the ceramic body and the metal layer is determined; 2. A contour line separating the solid material from the non-solid material is determined; 3. A point A is determined on a line perpendicular to the best fit line at a distance of 150 μm from the line of best fit where the line perpendicular to the line of best fit intersects the contour line; 4. A point B is determined on the perpendicular to the best fit line where the perpendicular to the best fit line intersects with the contour line at a distance of 80 μm from the best fit line; 5. A point C is determined on the line passing through points A and B where the line intersects the best fit line; 6. A point D is determined on a perpendicular line passing through point B to the best fit line where the perpendicular line intersects the best fit line; a contour line extending from the major boundary surface of the metal layer to the major boundary surface of the ceramic body, the contour line having an upper half and a lower half, the upper half of the contour line extending from the major boundary surface of the metal layer toward the major boundary surface of the ceramic body, and the lower half of the contour line extending from the major boundary surface of the ceramic body toward the major boundary surface of the metal layer, and the solid material in a region adjacent the upper half of the contour line has a higher silver content than a region adjacent the lower half of the contour line.

2. 2. The metal-ceramic substrate of claim 1, wherein the ceramic of the ceramic body is selected from the group consisting of aluminum nitride ceramic, silicon nitride ceramic, and aluminum oxide ceramic.

3. The metal-ceramic substrate of claim 1, wherein the metal layer comprises copper.

4. 2. The metal-ceramic substrate of claim 1, wherein the solid material comprises the metal of the metal layer.

5. The metal-ceramic substrate of claim 1, wherein the non-solid material comprises a gaseous material.

6. Meet the following requirements: A(BCD ｓｏｌｉｄ ) / A(BCD ｔｏｔａｌ )>95% 2. The metal-ceramic substrate according to claim 1, wherein:

7. The ratio A(BCD ｓｏｌｉｄ ) / A (BCD ｔｏｔａｌ 2. The metal-ceramic substrate of claim 1, wherein the sample standard deviation SSD of the surface roughness (SSD) is 10% or less.

8. 2. The metal-ceramic substrate of claim 1, wherein a ratio of a silver content of the solid material in a region adjacent the lower half of the contour line to a silver content of the solid material in a region adjacent the upper half of the contour line is less than 0.

8.

9. An electronic component comprising the metal-ceramic substrate according to claim 1.

Images