Metal-ceramic substrate with contact region

Abstract

The invention relates to a metal-ceramic substrate and an electronic component including the same. The present invention relates to a metal-ceramic substrate comprising: a) a ceramic body comprising a main boundary surface, b) a metal layer comprising a main boundary surface, where the metal layer is bonded to the ceramic body on the surface, and where the metal layer comprises a structured region comprising (i) a solid material in the region and (ii) a non-solid material in the region, and c) a silver-containing contact region arranged on the metal layer, characterized in that, in a cross-section running through the metal-ceramic substrate perpendicular to the main boundary surface of the ceramic body, the structured region has a geometry in which the following requirements are met: A (BCD solids) / A (BCD total) gt; a (BCD total) is the total area of the triangle described by point B, point C and point D, and A (BCD solid) is the area of the triangle described by point B, point C and point D, the area being occupied by the solid material. The solid material has an increased silver content in a region adjacent to the upper half of the contour line.

Description

Technical Field

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

[0002] Metal-ceramic substrates play an important role in the field of power electronics. They are key components in the construction of electronic components and ensure rapid dissipation of a large amount of heat during the operation of the components. Metal-ceramic substrates generally 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, a copper compound (usually copper oxide) having a melting point lower than that of copper is provided on the surface of a copper foil by reacting copper with a reactive gas (usually oxygen). When the copper foil treated in this way is applied to a ceramic body and the composite material is heated, the copper compound melts and wets the surface of the ceramic body, so that a stable adhesive bond is achieved between the copper foil and the ceramic body. This method is described, for example, in US 3744120 A or DE 2319854 C2.

[0004] In an alternative method, a metal foil can be bonded to a ceramic body at a temperature of about 650 °C to 1000 °C, wherein a special solder is used, which contains a metal (usually silver) having a melting point of at least 700 °C and a reactive metal. The role of the reactive metal is to react with the ceramic material and thus promote the bonding of the ceramic material to the remaining solder to form a reaction layer, while the metal having a melting point of at least 700 °C is used to bond the reaction layer to the metal foil. For example, JP4812985 B2 proposes to use a solder containing 50 wt% to 89 wt% of silver and copper, bismuth and a reactive metal to bond a copper foil to a ceramic body. With this method, the copper foil can be stably attached to the ceramic body. Alternatively, a silver-free solder can be used to bond the metal foil to the ceramic body. These solders are, for example, based on a high melting point metal (especially copper), a low melting point metal (such as bismuth, indium or tin) and a reactive metal (such as titanium). This technique is proposed, for example, in DE 102017114893A1. This technique basically produces a new and independent class of compounds, since the base material of the solder used is formed of another metal (copper instead of silver), which results in a change in the material properties and leads to adaptation with respect to other solder components and modified bonding conditions.

[0005] When constructing electronic components, metal-ceramic substrates are often equipped with chips. To equip the metal-ceramic substrate with chips, it is often necessary to provide a silver-containing contact area in the area of the metal-ceramic substrate to be equipped with chips. By providing this silver-containing contact area, the chips can be more easily connected to the metal-ceramic substrate using common processes such as sintering or soldering. To create the contact area, the metal-ceramic substrate is often first treated in the area with an etching solution to form the desired structuring. Then the contact area is provided by applying a silver-containing coating to the surface of the structured metal-ceramic substrate in the area.

[0006] The metal-ceramic substrates produced in this way are often exposed to high temperature variations during operation as parts of electronic components. While the temperature can be, for example, -20 °C or lower during operation interruptions (depending on the environment), the temperature of the metal-ceramic substrate can easily rise above 150 °C during operation. The metal-ceramic substrates are frequently exposed to these temperature differences. Due to the different thermal expansion coefficients of the metal and the ceramic, repeated temperature variations can cause the metal layer to peel off (delaminate) from the ceramic body, which can lead to a loss of performance. Therefore, high thermal shock resistance is a key criterion for the suitability of metal-ceramic substrates in electronics, especially in power electronics applications.

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

[0008] Accordingly, an object of the present invention is to provide a metal-ceramic substrate having improved thermal shock resistance.

[0009] This object is achieved by a metal-ceramic substrate according to claim 1. Accordingly, the present invention provides a metal-ceramic substrate comprising:

[0010] a) a ceramic body, which comprises a main boundary surface,

[0011] b) a metal layer, which comprises a main boundary surface, wherein the metal layer is bonded to the ceramic body on this surface, and wherein the metal layer comprises a structured area, which comprises

[0012] (i) a solid material in the area, and

[0013] (ii) a non-solid material in the area

[0014] and

[0015] c) a silver-containing contact area arranged on the metal layer,

[0016] wherein

[0017] In a cross-section of the metal-ceramic substrate that penetrates the main boundary surface of the ceramic body perpendicularly, the structured region has a geometry that meets the following requirements:

[0018] A(BCD 固体 ) / A(BCD 总 ) > 70%,

[0019] where

[0020] A(BCD 总 ) is the total area of the triangle described by points B, C, and D, and

[0021] A(BCD 固体 ) is the area of the triangle described by points B, C, and D that is occupied by solid material,

[0022] where points B, C, and D are determined as follows:

[0023] 1. Determine the best-fit line between the ceramic body and the metal layer;

[0024] 2. Determine the contour line that separates the solid material from the non-solid material;

[0025] 3. On the perpendicular line to the best-fit line, at a distance of 150 μm from the best-fit line, determine point A where the perpendicular line to the best-fit line intersects the contour line;

[0026] 4. On the perpendicular line to the best-fit line, at a distance of 80 μm from the best-fit line, determine point B where the perpendicular line to the best-fit line intersects the contour line;

[0027] 5. On the line passing through points A and B, determine point C where the line intersects the best-fit line; and

[0028] 6. On the perpendicular line to the best-fit line passing through point B, determine point D where

[0029] the perpendicular line intersects the best-fit line; and

[0030] where the contour line extends from the main boundary surface of the metal layer to the main boundary surface of the ceramic body, where the contour line includes an upper half and a lower half, where the upper half of the contour line extends from the main boundary surface of the metal layer towards the main boundary surface of the ceramic body, and the lower half of the contour line extends from the main boundary surface of the ceramic body towards the main boundary surface of the metal layer, and where the solid material in the region adjacent to the upper half of the contour line has a higher silver content than the solid material in the region adjacent to the lower half of the contour line.

[0031] Furthermore, the present invention relates to an electronic component which comprises such a metal-ceramic substrate.

[0032] The metal-ceramic substrate according to the present invention comprises a ceramic body which comprises a main boundary surface.

[0033] The ceramic body is preferably a body formed of ceramic. The body can have any geometric shape, but is preferably designed as a cube. The ceramic body comprises boundary surfaces, six boundary surfaces in the case of a cube. Herein, the main boundary surface preferably refers to the boundary surface on which a metal layer is bonded (very particularly preferably the boundary surface having the largest area). The main boundary surface is particularly preferably the boundary surface on which a metal layer comprising a structured region is bonded (very particularly preferably the boundary surface having the largest area), and very particularly preferably the boundary surface on which a metal layer having a silver-containing contact region arranged thereon is bonded (in particular the boundary surface having the largest area). The main boundary surface preferably lies in the main extension plane of the ceramic body or extends parallel to the main extension plane. Therefore, the main extension plane of the ceramic body is preferably understood as a plane extending parallel to or enclosing the main boundary surface of the ceramic body.

[0034] 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 another 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 alumina ceramics (such as ZTA ("zirconia toughened alumina") ceramics). According to another very particularly preferred embodiment, the ceramic body consists of: (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 the second main group of the periodic table, (3c) zirconium, (3d) copper, (3e) molybdenum and (3f) silicon; and optionally (4) inevitable impurities. According to yet another very particularly preferred embodiment, the ceramic body does not contain bismuth, gallium and zinc.

[0035] The ceramic body preferably has a thickness in the range of 0.05 mm to 10 mm, more preferably in the range of 0.1 mm to 5 mm, and particularly preferably in the range of 0.15 mm to 3 mm.

[0036] The metal-ceramic substrate according to the invention comprises a metal layer which comprises a main boundary surface, wherein the metal layer is bonded to the ceramic body on this surface, and wherein the metal layer comprises a structured region which comprises (i) solid material in the region and (ii) non-solid material in the region.

[0037] The metal layer comprises a boundary surface. The metal layer comprises a main boundary surface. Herein, the main boundary surface preferably refers to the boundary surface facing away from the ceramic body (very particularly preferably the boundary surface having the largest area). Thus, the main boundary surface preferably refers to the boundary surface on which the silver-containing contact region is arranged (very particularly preferably the boundary surface having the largest area). The main boundary surface preferably lies in the main extension plane of the metal layer or extends parallel to this main extension plane. Thus, the main extension plane of the metal layer is preferably understood as a plane extending parallel to the main boundary surface of the metal layer or enclosing the main boundary surface. The main boundary surface of the metal layer preferably extends parallel to the main boundary surface of the ceramic body and is particularly preferably spaced apart therefrom.

[0038] The metal layer is preferably adhesively bonded to the ceramic body. According to a preferred embodiment, the metal layer is bonded to the ceramic body via a DCB (direct copper bonding) process. According to another preferred embodiment, the metal layer is bonded to the ceramic body via a soldering process. The soldering process can be, for example, an AMB (active metal soldering) process, preferably using a silver-free soldering alloy (based on the solid content of the soldering alloy, the silver content is, for example, less than 1.0 wt%) or a silver-containing soldering alloy (based on the solid content of the soldering alloy, the silver content is, for example, at least 50 wt%). Thus, the metal layer can also comprise a bonding layer in contact with the ceramic body. The bonding layer can be, for example, a welding layer (in particular a soldering layer) or a diffusion layer.

[0039] The metal layer is bonded to the ceramic body on the surface. Accordingly, the metal layer is preferably bonded to the main boundary surface of the ceramic body on the surface. The metal layer is preferably not bonded to the entire main boundary surface of the ceramic body. In particular, it can be provided that the main boundary surface of the ceramic body is 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. Furthermore, the metal layer is preferably structured. The structuring is preferably understood to mean a recess in the metal layer in order to separate the individual parts of the metal layer from one another and thus to electrically insulate these parts. Such structuring is often created using etching techniques.

[0040] Accordingly, the metal layer comprises a structured region. The structured region is understood as the part of the metal layer containing the structuring. The structuring is preferably a recess in the metal layer. Thus, the main boundary surface of the metal layer comprises the metal of the metal layer, which is interrupted by the recess in the structured region.

[0041] The structured region includes a region containing a solid material and a region containing a non-solid material.

[0042] The region containing the solid material preferably contains (i) the metal of the metal layer (optionally including a bonding layer if present) and (ii) the metal of the contact region, especially silver.

[0043] The region containing the non-solid material preferably contains a gaseous material. Thus, the non-solid material preferably includes a gaseous material. The non-solid material is preferably a gaseous material that fills the recesses in the metal layer. Such a gaseous material often comes from the ambient atmosphere. Preferably, the gaseous material thus contains at least one element selected from the group consisting of nitrogen, oxygen, and noble gases. The gaseous material is very particularly preferably a gas mixture, especially air.

[0044] According to a preferred embodiment, the recesses extend from the main boundary surface of the ceramic body to the main boundary surface of the metal layer in a direction perpendicular to the main boundary surface of the ceramic body. The recesses preferably form channels that are filled with the non-solid material to at least 50 vol%, more preferably at least 80 vol%, even more preferably at least 90 vol%, particularly preferably at least 95 vol%, and very particularly preferably at least 99 vol%, especially completely filled with the non-solid material.

[0045] The metal layer preferably contains at least one metal selected from the group consisting of copper, aluminum, and molybdenum. According to a particularly preferred embodiment, the metal layer contains at least one metal selected from the group consisting of copper and molybdenum. According to a very particularly preferred embodiment, the metal layer contains copper. According to another preferred embodiment, the metal layer consists of copper and inevitable impurities. According to another preferred embodiment, based on the total weight of the metal layer (preferably including any bonding layer that may be present), the proportion of copper is at least 60 wt%, more preferably at least 65 wt%, even more preferably at least 70 wt%, and particularly preferably at least 75 wt%.

[0046] According to a preferred embodiment, the metal layer is produced by adhesively bonding a copper foil (preferably a foil made of high-purity copper) to the ceramic body. According to a preferred embodiment, the bonding can be carried out via a DCB (direct copper bonding) process or via a brazing process. The brazing process can be, for example, an AMB (active metal brazing) process, preferably using a silver-free brazing alloy (based on the solid content of the brazing alloy, the silver content is, for example, less than 1.0 wt%) or a silver-containing brazing alloy (based on the solid content of the brazing alloy, the silver content is, for example, at least 50 wt%). In this case, in addition to the copper from the copper foil, the metal layer can also contain metals from the bonding layer, especially metals from the welding layer (such as the brazing layer) or the diffusion layer.

[0047] The metal layer preferably has a thickness in the range from 0.01 mm to 10 mm, particularly preferably in the range from 0.03 mm to 5 mm, and very particularly preferably in the range from 0.05 mm to 3 mm.

[0048] The metal-ceramic substrate according to the invention comprises a silver-containing contact region arranged on the metal layer. This contact region preferably serves to facilitate the connection of the chip to the metal layer. The chip is preferably bonded to the metal layer by sintering, soldering or adhesive bonding. Since it is particularly difficult to attach the chip to the metal of the metal layer of the metal-ceramic substrate, the metal layer is preferably provided with a contact region. This contact region is preferably made of silver or a silver-containing alloy. In the case of a silver-containing alloy, the silver-containing alloy contains at least 50% by weight of silver, based on the weight of the silver alloy. Preferably, the contact region is provided at all positions on the metal layer of the metal-ceramic substrate where the metal-ceramic substrate is later to be filled with chips. The contact region can be formed on the metal layer of the metal-ceramic substrate using different techniques. For example, the contact region can be provided by deposition of a silver-containing layer. The deposition of the silver-containing layer is preferably carried out chemically (e.g. electrochemically) or physically. The chemical deposition of the silver-containing layer can be carried out, for example, electrochemically or electrolessly. The electroless chemical deposition of the silver-containing layer is preferably carried out by applying a silver-containing solution in which a charge exchange takes place between the metals, where a part of the metal of the metal layer dissolves while silver in the solution is deposited. 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, and particularly preferably a nitric acid solution of silver nitrate. The physical deposition of the silver-containing layer can be carried out, for example, by vapor deposition. Preferred methods for vapor deposition are in particular electron beam deposition, laser beam deposition, arc discharge deposition or cathodic sputtering.

[0049] The structured region of the metal layer of the metal-ceramic substrate has the geometry described herein. The geometry of the structured region is determined in a cross-section through the metal-ceramic substrate perpendicular to the main boundary surface of the ceramic body.

[0050] The structured region of the metal-ceramic substrate has, in a cross-section through the metal-ceramic substrate perpendicular to the main boundary surface of the ceramic body, a geometry that meets the following requirements:

[0051] A(BCD 固体 ) / A(BCD 总 ) > 70%,

[0052] where

[0053] A(BCD 总 ) is the total area of the triangle described by points B, point C and point D, and

[0054] A(BCD 固体 ) is the area of the triangle described by points B, C, and D, which area is occupied by the solid material,

[0055] According to a preferred embodiment, the structured region of the metal-ceramic substrate has a geometry in a cross-section that penetrates the metal-ceramic substrate perpendicular to the main boundary surface of the ceramic body, and which satisfies the ratio A(BCD 固体 ) / A(BCD 总 ) > 75%, more preferably > 80%, even more preferably > 85%, particularly preferably > 90% and very particularly preferably > 95%.

[0056] According to another preferred embodiment, the structured region of the metal-ceramic substrate has a geometry in a cross-section that penetrates the metal-ceramic substrate perpendicular to the main boundary surface of the ceramic body, and which satisfies the ratio A(BCD 固体 ) / A(BCD 总 ) is in the range of 75% to 100%, particularly preferably in the range of 90% to 100%, and most preferably in the range of 95% to 99%.

[0057] To determine the triangle described by points B, C, and D, the cross-section of the structured region of the metal layer of the metal-ceramic substrate is observed. This cross-section extends perpendicular to the main boundary surface of the ceramic body. Preferably, the cross-section can be observed by cutting the metal-ceramic substrate perpendicular to the main boundary surface of the ceramic body and obtaining a picture of the resulting cross-section using a scanning electron microscope.

[0058] The points B, C, and D of the triangle can be determined in the cross-section as described below. For illustrative purposes, by way of example, reference is made to Figure 1 and Figure 2 . Description of the Drawings

[0059] Figure 1 Shows a schematic diagram of a general metal-ceramic substrate.

[0060] Figure 2 Schematically shows a metal-ceramic substrate according to the invention having a structured region, wherein the solid material in the region adjacent to the upper half of the contour line has a higher silver content than the solid material in the region adjacent to the lower half of the contour line.

[0061] Figure 3 Shows a part of a cross-section through the metal-ceramic substrate according to the invention.

[0062] Figure 4An example of an optical micrograph of a cross-section of a structured area detail of a copper layer of a copper-ceramic substrate according to Example 1 is shown.

[0063] Figure 5 An example of an optical micrograph of a cross-section of a structured area detail of a copper layer of a copper-ceramic substrate according to Comparative Example 1 is shown. Detailed Description

[0064] Figure 1 The metal-ceramic substrate 1 shown in includes a ceramic body 10. The ceramic body 10 includes a main boundary surface 15. The metal-ceramic substrate 1 includes a metal layer 20. The metal layer 20 includes a main boundary surface 24 parallel to the main boundary surface 15 of the ceramic body 10 on the upper side facing away from the main boundary surface 15 of the ceramic body 10. The metal layer 20 is adhesively bonded to the main boundary surface 15 of the ceramic body 10 on the surface. In accordance with Figure 1 In the embodiment of, the metal-ceramic substrate 1 further includes an additional metal layer 200, which is adhesively bonded to the ceramic body 10 on the surface. There is a contact area 8 containing silver on the metal layer 20. The metal layer 20 includes a structure. This is formed by a recess 22 in the metal layer 20. The recess 22 contains a non-solid material. The structured area 4 includes the metal of the metal layer 20 and the recess 22 in the area. Therefore, the structured area 4 contains a solid material 50 and a non-solid material (such as a gaseous material) in the area. The solid material is formed by the metal of the metal layer 20, and the non-solid material fills the recess 22. The gaseous material is often ambient air. The solid material 50 is separated from the non-solid material of the recess 22 by a contour line 40. The main boundary surface 24 of the metal layer 20 contains the metal of the metal layer 20, and this metal layer is interrupted by the recess 22 in the structured area. The recess 22 extends from the main boundary surface 24 of the metal layer 20 to the main boundary surface 15 of the ceramic body 10 in a direction perpendicular to the main boundary surface 15 of the ceramic body 10 and preferably forms a channel that is completely or mainly filled with a non-solid material.

[0065] Figure 2 The metal-ceramic substrate shown in has the same basic structure as the Figure 1 The metal-ceramic substrate shown in. The contour line 40 includes an upper half and a lower half. The upper half of the contour line 40 extends from the main boundary surface 24 of the metal layer 20 in the direction of the main boundary surface 15 of the ceramic body 10. The lower half of the contour line 40 extends from the main boundary surface 15 of the ceramic body 10 in the direction of the main boundary surface 24 of the metal layer 20. The solid material 50 contains silver 60 in the area adjacent to the upper half of the contour line 40. In the area adjacent to the lower half of the contour line 40, the solid material does not contain or contains less silver 60.

[0066] In Figure 3In this part of the cross-section through the metal-ceramic substrate according to the invention, a part of the structured area can be seen. The area of the ceramic body 10 bonded to the metal layer 20 on the surface is shown. The contour line 40 separates the solid material 50 from the non-solid material in the recess 22 of the metal layer 20.

[0067] The determination of points B and C of line BC in the cross-section is preferably carried out in multiple steps:

[0068] In the first step, the best-fit line 30 between the ceramic body 10 and the metal layer 20 is determined. For this purpose, the areas of the ceramic body 10 and 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 observable in the cross-section.

[0069] In the second step, the contour line 40 is determined, which separates the solid material 50 from the non-solid material in the recess 22. The solid material 50 is optically determined; this is often the material of the metal layer 20. The non-solid material is also visually determined. The non-solid material is often a gaseous material used to fill the structured part as the recess 22 in the metal layer 20.

[0070] In the third step, on the perpendicular line to the best-fit line 30, at a distance of 150 μm from the best-fit line 30, point A is determined, at which the perpendicular line to the best-fit line 30 intersects the contour line 40.

[0071] In the fourth step, on the perpendicular line to the best-fit line 30, at a distance of 80 μm from the best-fit line 30, point B is determined, at which the perpendicular line to the best-fit line 30 intersects the contour line 40.

[0072] In the fifth step, on the straight line passing through points A and B, point C is determined, at which the straight line intersects the best-fit line 30.

[0073] In the sixth step, on the perpendicular line to the best-fit line 30 passing through point B, point D is determined, at which the perpendicular line intersects the best-fit line 30.

[0074] Cutting the metal-ceramic substrate perpendicular to the main boundary surface of the ceramic body and recording the cross-section thus obtained by an optical microscope (incident light / bright field) is preferably carried out as follows:

[0075] In the first step, by using a diamond saw blade at a low rotational speed and using a lubricant (Exakt), sawing is carried out perpendicular to the plane spanned by the main boundary surface of the ceramic body of the metal-ceramic substrate, and first a piece with a size between 100 mm 2 to 400 mm2 A cubic sample blank with a rectangular base within the specified range. The sample blank correspondingly includes a sample surface that is to be studied. Thus, before sawing, this sample surface extends perpendicular to the plane spanned by the main boundary surface of the ceramic body of the metal-ceramic substrate. Therefore, it includes portions on the ceramic body and the metal layer (including an optionally provided bonding layer). First, the sample blank is embedded in a mold with a low-shrinkage epoxy resin (Caldo-Fix, Struers), where the sample surface is oriented perpendicular to the mold wall. Then, the epoxy resin is cured in a drying cabinet at 75 °C. After curing, the sample surface of the sample blank is mechanically polished using an automatic polishing device (Tegrapole, Struers) to obtain a roughness of 1 μm or less.

[0076] In the second step, an optical microscope (Leica, DM6000M, incident light / bright field) is used to identify, at a magnification of 200x in the analysis area, structured areas in the metal layer that include solid material in the area and non-solid material in the area. The solid material and the non-solid material can be clearly distinguished in the structured area due to different colors.

[0077] Area A(BCD 固体 ) and A(BCD 总 ) are preferably determined in a conventional manner, for example, using image evaluation software (such as IMS Client, Imagic).

[0078] Preferably, the term "in cross-section" as used herein refers to the (preferably representative) total cross-section, particularly preferably at least ten cross-sections, very particularly preferably not more than 20 cross-sections, and especially ten cross-sections. These cross-sections preferably extend parallel to each other and are evenly spaced apart from each other.

[0079] Here, in order to determine the ratio A(BCD 固体 ) / A(BCD 总 ) of the metal-ceramic substrate to be observed, the following procedure is preferably used:

[0080] 1. Examine at least ten, particularly preferably ten different cross-sections of the structured area;

[0081] 2. Determine the ratio A(BCD 固体 ) / A(BCD 总 ) for each of these cross-sections;

[0082] And

[0083] 3. For the ratio A(BCD 固体 ) / A(BCD总 ) Take the average to obtain the ratio A(BCD of the metal-ceramic substrate under observation 固体 ) / A(BCD 总 ).

[0084] According to a preferred embodiment, on at least ten different cross-sections of at least one structured region of the metal layer, more preferably on no more than 20 different cross-sections of at least one structured region of the metal layer, and most preferably on ten different cross-sections of at least one structured region of the metal layer, the ratio A(BCD 固体 ) / A(BCD 总 ) has a sample standard deviation SSD of no more than 10%, more preferably no more than 7%, particularly preferably no more than 5%, and very particularly preferably no more than 2%. The sample standard deviation SSD is determined using the following formula:

[0085]

[0086] Where:

[0087] n = the number of individual values of the ratio A(BCD - 固体 ) / A(BCD - 总 ),

[0088] X i = an individual value of the ratio A(BCD - 固体 ) / A(BCD - 总 ), and

[0089] is the average of the individual values.

[0090] According to the present invention, in a cross-section of the metal-ceramic substrate that penetrates perpendicularly to the main boundary surface of the ceramic body, the structured region has a geometry where the contour line extends from the main boundary surface of the metal layer to the main boundary surface of the ceramic body, where the contour line includes an upper half and a lower half, where the upper half of the contour line extends from the main boundary surface of the metal layer towards the main boundary surface of the ceramic body, and the lower half of the contour line extends from the main boundary surface of the ceramic body towards the main boundary surface of the metal layer, and where the solid material in the region adjacent to the upper half of the contour line has a higher silver content than the solid material in the region adjacent to the lower half of the contour line.

[0091] Therefore, according to the present invention, the contour line extends from the main boundary surface of the metal layer to the main boundary surface of the ceramic body. The contour line preferably does not extend along the main boundary surface of the ceramic and does not extend along the main boundary surface of the metal layer. Therefore, the contour line preferably extends in a region that does not include the main boundary surface of the ceramic and the main boundary surface of the metal layer.

[0092] The contour line includes an upper half and a lower half. The upper half of the contour line extends from the main boundary surface of the metal layer in the direction of the main boundary surface of the ceramic body. The lower half of the contour line extends from the main boundary surface of the ceramic in the direction of the main boundary surface of the metal layer.

[0093] 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 solid material in the region adjacent to the lower half of the contour line. According to a preferred embodiment, the ratio of the silver content in the solid material in the region adjacent to the lower half of the contour line to the silver content in the solid material in the region adjacent to the upper 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.

[0094] The region of the solid material adjacent to the contour line preferably has a width in the range from 0.3 μm to 1.0 μm, particularly preferably in the range from 0.5 μm to 0.6 μm and very particularly preferably a width of 0.5 μm. The contour line thus preferably delineates the contour of the solid material, wherein the composition of the solid material (including the silver content) is preferably determined using the method described above in the region defined by (i) the main boundary surface of the metal layer, (ii) the main boundary surface of the ceramic body, (iii) the contour line and (iv) a parallel displacement of the contour line in the direction of the solid material by 0.3 μm to 1.0 μm, particularly preferably by 0.5 μm to 0.6 μm and very particularly preferably by 0.5 μm. The contour line preferably divides into an upper half and a lower half midway between the main boundary surface of the metal layer and the main boundary surface of the ceramic body, wherein the upper half of the contour line extends from the main boundary surface of the metal layer in the direction of the main boundary surface of the ceramic body and the lower half of the contour line extends from the main boundary surface of the ceramic body in the direction of the main boundary surface of the metal layer. Thus, the region of the solid material to be measured consists of an upper half located on the upper half of the contour line and a lower half located on the lower half of the contour line.

[0095] The silver content of the solid material in the region adjacent to the upper half of the contour line and the silver content of the solid material in the region adjacent to 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).

[0096] In SEM-EDX, a focused primary electron beam is guided (scanned) point by point over the sample surface. Scattered electrons are detected using a detector, where the number of electrons per pixel results in a microscopic image of the sample surface displayed in grayscale. In addition, the primary electron beam excites the sample to emit characteristic X-ray radiation, where the elements in the sample and their weight ratios can be determined by analyzing the energy spectrum using an EDX detector.

[0097] For inspection, for example, a scanning electron microscope (JSM-6060 SEM, JEOL Ltd) with a silicon drift EDX detector (NORAN, Thermo Scientific Inc) and analysis software (Pathfinder Mountaineer EDS System, version 2.8, for example, Thermo Scientific Inc) is used. For the scanning electron microscope, the following settings can be used: magnification: 200 times, acceleration voltage = 10 kV, working distance = 10 mm, spot size (50 - 60) (adjusted to achieve 25% + / - 5% of the dead time of the EDX detector). The following settings of the EDX detector can be used to detect the EDX spectrum: live time = 30 s, rate = automatic, low energy cut-off = 100 keV, high energy cut-off = automatic (depending on the SEM acceleration voltage). Depending on the selected magnification and the thickness of the metal layer, multiple SEM-EDX measurements may be required to image the entire structured area.

[0098] In the region adjacent to the upper half of the contour line and in the region adjacent to the lower half of the contour line, the silver content is measured at at least five and particularly preferably ten representative positions within each region. The silver content is preferably understood as the arithmetic mean of the corresponding individual measured values.

[0099] Surprisingly, it has been found that the metal-ceramic substrate having this geometry according to the invention has improved thermal shock resistance compared to metal-ceramic substrates from the prior art. These metal-ceramic substrates contain a high proportion of solid material in the metal layer at the boundary with the surface of the ceramic body. In contrast, it has been found that as long as the metal-ceramic substrates from the prior art include silver-containing contact areas arranged on the metal layer, the proportion of solid material in the metal layer at the boundary with the surface of the ceramic body in these metal-ceramic substrates is significantly lower.

[0100] Not being bound by explanations, this may be due to the fact that in the prior art, it is often the case that the produced metal-ceramic substrate is first structured and then silver-plated on the surface to create contact areas. However, the already structured areas of the surface of the metal-ceramic substrate are only inadequately masked during silver plating. For this purpose, the areas of the surface of the structured metal-ceramic substrate that are not coated with silver are often masked first before silver plating. A film (e.g., a dry film) is often used for masking. The film spans the structured portion of the metal-ceramic substrate such that the structured portion is covered with the film but not fully lined, especially not in the area close to the ceramic body. The subsequent silver plating is often accomplished by dipping the structured and masked metal-ceramic substrate into a bath containing a silver-ion-containing solution. The silver-ion-containing solution can wash under the masking film such that it comes into direct contact with the underlying structured portion. During the silver plating process, metal ions are electrochemically dissolved from the metal layer of the metal-ceramic substrate in the area of the structured portion and are 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 areas at a spatial distance close to the ceramic body. Thus, silver is typically deposited directly on the surface of the structured portion, while metal ions are preferably released from the area close to the ceramic body (at a distance of approximately up to 50 μm from the surface of the ceramic body), such that as the contact time with the silver-ion-containing solution progresses, the area of the structured portion close to the ceramic body is gradually removed. This results in the removal of solid material (especially the metal of the metal foil) from the metal foil in the area close to the ceramic body, and thereby creates weak points where the metal layer detaches from the ceramic body, which has an adverse effect on the thermal shock resistance. Thus, the removal of solid material in the structured portion may be due to the lack of lining of the structured portion with the masking film. However, according to the present invention, a structured area is created that contains a sufficient amount of solid material in the area close to the ceramic body, whereby detachment of the metal layer from the ceramic body can be prevented and an improvement in thermal shock resistance can be achieved.

[0101] The solid material contains silver in the area adjacent to the upper half of the contour line. The reason for this is that, according to one embodiment, the masking is applied by a printing process before silver plating. Since the structured portion of the metal-ceramic substrate often has a curved geometry, the structured portion is (almost) completely covered by the masking in the area close to the ceramic body, which improves the thermal shock resistance. In contrast, the area of the structured portion remote from the ceramic body is often not completely masked and thus this area is at least partially coated with silver in the subsequent silver plating step.

[0102] According to a preferred embodiment, the metal-ceramic substrate comprises a further (second) metal layer which is adhesively bonded to the ceramic body on its surface. The further metal layer is preferably adhesively bonded on its surface to a boundary surface which faces away from the main boundary surface of the ceramic body (and preferably extends parallel to the main boundary surface). The further (second) metal layer may have the same properties as the (first) metal layer or may differ from the (first) metal layer in terms of its properties. For the properties of the further (second) metal layer, reference is made to the explanations given above for the (first) metal layer.

[0103] The metal-ceramic substrate according to the invention can be used in particular for electronic applications, especially in the field of power electronics.

[0104] Accordingly, the invention also provides an electronic component which comprises a metal-ceramic substrate according to the invention.

[0105] According to a preferred embodiment, the electronic component comprises a metal-ceramic substrate according to the invention and at least one chip. The at least one chip is preferably adhesively bonded on its surface to a silver-containing contact area which is arranged on the (first) metal layer. Accordingly, the electronic component preferably comprises a chip which is in contact with the (first) metal layer of the metal-ceramic substrate via the silver-containing contact area.

[0106] According to another preferred embodiment, the metal-ceramic substrate of the electronic component comprises a further (second) metal layer. The further (second) metal layer is preferably adhesively bonded to the ceramic body on its surface. In this case, the further metal layer is preferably adhesively bonded on its surface to a boundary surface of the ceramic body which faces away from the main boundary surface of the ceramic body (and preferably extends parallel to the main boundary surface).

[0107] According to another preferred embodiment, the electronic component comprises a substrate. The substrate is preferably adhesively bonded on its surface to the further (second) metal layer of the metal-ceramic substrate. Alternatively, the further (second) metal layer of the metal-ceramic substrate can be formed as a heat sink.

[0108] According to another preferred embodiment, the electronic component comprises: a metal-ceramic substrate which comprises a (first) metal layer and a further (second) metal layer (wherein the further metal layer is preferably adhesively bonded on its surface to a boundary surface which faces away from the main boundary surface of the ceramic body); a substrate and at least one chip, wherein the at least one chip is adhesively bonded on its surface to the first metal layer of the metal-ceramic substrate via a silver-containing contact area arranged on the metal layer, and the substrate is adhesively bonded on its surface to the further (second) metal layer of the metal-ceramic substrate.

[0109] The metal-ceramic substrate according to the invention can be obtained by different manufacturing processes.

[0110] According to a preferred embodiment, the method is a method for producing a metal-ceramic substrate provided with a structured portion and a silver-containing contact area, the method comprising the following steps:

[0111] a) providing a metal-ceramic substrate comprising:

[0112] a1) a ceramic body, and

[0113] a2) a metal layer adhesively bonded to the ceramic body on its surface,

[0114] b) structuring the metal layer,

[0115] c) applying a mask to the structured metal layer by applying a liquid medium containing a masking agent to the structured metal layer in areas and curing the masking agent,

[0116] d) depositing a silver-containing layer on the unmasked areas of the structured metal layer to obtain a silver-containing contact area, and

[0117] e) removing the mask.

[0118] Thus, in step a), preferably the metal-ceramic substrate is provided first.

[0119] This metal-ceramic substrate comprises a ceramic body and a metal layer adhesively bonded to the ceramic body on its surface. The metal-ceramic substrate may be a standard metal-ceramic substrate. The ceramic body and the metal layer may have the compositions as described above with respect to the metal-ceramic substrate. The metal layer may preferably be adhesively bonded to the ceramic body, also as described above with respect to the metal-ceramic substrate.

[0120] In step b), preferably the metal layer is structured first.

[0121] The structured part is preferably understood to mean a recess in the metal layer in order to separate the individual parts of the metal layer from each other and thus to electrically insulate these parts. Thus, the structured part preferably exposes an area of the ceramic body. Such structured parts are often created using etching techniques. For example, an etching mask can first be applied to the metal layer. The etching mask is used to protect the masked areas of the metal layer of the metal-ceramic substrate from etching during the etching step. This ensures that only those unmasked areas of the metal layer of the metal-ceramic substrate that are intended for structuring can be etched. Thus, the etching mask is created in such a way that the masked areas of the metal layer do not undergo etching during the etching step. There is no further limitation on the type of etching mask. The etching mask can be, for example, a standard negative mask or a positive mask. Standard resists can be used to produce the etching mask. These resists preferably contain a curable polymer (such as a photocurable polymer) and can be applied to the metal layer, for example as a film (such as a dry film) or as a liquid (such as by printing or spraying). After application, the resist can be processed in a suitable manner (such as by curing through light irradiation) to obtain the etching mask. According to a possible embodiment, a photosensitive film is applied to the metal layer of the metal-ceramic substrate and then exposed at the areas to be masked in order to obtain the etching mask. Then the unexposed areas of the photosensitive film can be removed in a conventional manner (such as using a sodium carbonate solution). After the etching mask has been applied to the metal layer, the unmasked areas of the metal layer are preferably etched to obtain the structured part. The etching is preferably carried out in a standard professional manner. Thus, a standard etching solution is preferably used for etching. According to a preferred embodiment, the etching solution is selected from the group consisting of FeCl3 etching solution and CuCl2 etching solution. If necessary, additional etching solutions can be used, for example to structure the unmasked areas of an optionally included bonding layer. According to a preferred embodiment, the additional etching solution can be selected from the group consisting of etching solutions containing hydrogen peroxide and etching solutions containing ammonium persulfate. For example, the additional etching solution can be an etching solution containing ammonium fluoride and fluoboric acid (such as HBF4) as well as hydrogen peroxide and / or ammonium persulfate.

[0122] Preferably, after etching the unmasked areas of the metal layer while maintaining the structured part, the etching mask is removed. The etching mask can be removed in a standard manner. For this purpose, the metal-ceramic substrate can be treated with an alkaline solution (such as a 2.5% sodium hydroxide solution) to remove the etching mask.

[0123] In step c), masking is preferably applied to the structured metal layer by applying a liquid medium containing a masking agent to the structured metal layer in the area and curing the masking agent.

[0124] The masking serves to protect the masked areas of the metal layer during step d) from the deposition of the silver-containing layer. This ensures that the silver-containing layer is only deposited on the unmasked areas of the metal layer of the metal-ceramic substrate. Thus, the masking is designed in such a way that the silver-containing layer cannot be deposited on the masked areas of the metal layer of the metal-ceramic substrate.

[0125] According to a preferred embodiment, the structured metal layer to which the masking is applied further comprises structured areas, particularly preferably the structured areas between the main boundary surface of the metal layer and the main boundary surface of the ceramic. Thus, in particular, the areas of the metal layer in the vicinity of the ceramic body are also provided with masking in order to protect these areas from being dissolved during the deposition of the silver-containing layer in step d), in particular when in contact with a solution containing silver ions.

[0126] To apply the masking, a liquid medium containing a masking agent is applied to the structured metal layer in the areas and the masking agent is cured.

[0127] The liquid medium is preferably a medium that is liquid at room temperature and standard pressure. The liquid medium is preferably a medium containing a polar solvent, particularly preferably water. According to a preferred embodiment, the liquid medium is selected from the group consisting of solutions and suspensions.

[0128] The liquid medium contains a masking agent. The masking agent is preferably designed to be curable. The masking agent is not further limited. According to a preferred embodiment, the masking agent is curable, particularly preferably UV-curable. The UV-curable masking agent preferably comprises at least one compound selected from the group consisting of monomers and oligomers. According to a particularly preferred embodiment, the UV-curable masking agent comprises at least one compound selected from the group consisting of acrylates, epoxy resins and unsaturated polyester resins. The liquid medium preferably further contains a photoinitiator. The photoinitiator can be, for example, a compound that decomposes upon absorption of UV light and forms a reactive substance capable of initiating the polymerization and curing of the UV-curable masking agent. In addition, the liquid medium can contain other components such as colorants and additives.

[0129] The liquid medium containing the masking agent is applied to the structured metal layer in the areas. For this purpose, the liquid medium is preferably applied to the areas of the structured metal layer that will be masked and protected from the deposition of the silver-containing layer in step d).

[0130] 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.

[0131] After applying the liquid medium, the masking agent contained therein is preferably cured. 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 contained in the liquid medium (especially monomers or oligomers) polymerizes.

[0132] According to a preferred embodiment, applying the mask to the structured metal layer includes an additional masking step. The additional masking step means applying a masking agent. According to another preferred embodiment, applying the mask to the structured metal layer does not include a subtractive masking step. The subtractive masking step is understood to mean, for example, in the additional masking step, especially before depositing a silver-containing layer on the unmasked area of the structured metal layer according to step d) to obtain a silver-containing contact area, partially removing the applied and cured masking agent. According to this preferred embodiment, the liquid medium containing the masking agent is only applied to the area of the structured metal layer and (if appropriate) the area of the ceramic body exposed by the recesses in the metal layer forming the structure, and the silver-containing layer is not deposited on these areas in step d). In a conventional masking method, the masking agent (preferably as a layer) is applied to the structured metal layer in the additional masking step, especially on the entire surface, where the cured masking agent is removed in the subsequent subtractive masking step in the area of the structured metal layer (on which the silver-containing layer is deposited in the subsequent step). According to this preferred embodiment, by omitting the subtractive masking step, a particularly simple method for producing a metal-ceramic substrate provided with a structure and a silver-containing contact area is advantageously provided.

[0133] According to a preferred embodiment, in step c), a mask is also applied to the area of the ceramic body exposed by the recesses in the metal layer forming the structure by applying a liquid medium containing a masking agent to the area of the ceramic body, especially to the area of the ceramic body exposed by the recesses in the metal layer forming the structure, and curing the masking agent. Applying the mask to the exposed area of the ceramic body can be advantageous in order to protect the exposed area of the ceramic body from the deposition of the silver-containing layer in step d).

[0134] Applying the mask to the structured metal layer and applying the mask to the area of the ceramic body exposed by the recesses in the metal layer forming the structure can be carried out simultaneously or sequentially.

[0135] To apply the mask to the area of the ceramic body exposed by the recesses in the metal layer forming the structure, the liquid medium as described above for applying the mask to the structured metal layer and the application as described above for applying the mask to the structured metal layer can be used.

[0136] In step d), a silver-containing layer is preferably deposited on the unmasked area of the structured metal layer to obtain a silver-containing contact area.

[0137] The silver-containing layer is preferably a layer composed of silver or a silver-containing alloy, and particularly preferably a layer composed of silver. The deposition of the silver-containing layer is preferably carried out chemically (e.g., electrochemically) or physically. The chemical deposition of the silver-containing layer can be carried out, for example, electrochemically or electrolessly. The electroless chemical deposition of the silver-containing layer is preferably carried out by applying a silver-containing solution, in which a charge exchange occurs between the metals, where a part of the metal of the metal layer dissolves while silver in the solution is deposited. According to a preferred embodiment, the silver-containing solution contains a silver salt, and particularly preferably contains silver nitrate. According to a particularly preferred embodiment, the silver-containing solution is an acidic solution of silver nitrate, and particularly preferably a nitric acid solution of silver nitrate. The concentration of silver in the nitric acid solution can be, for example, in the range of 0.5 g / l to 1.5 g / l, particularly preferably in the range of 0.6 g / l to 1.4 g / l, and very particularly preferably in the range of 0.8 g / l to 1.2 g / l. The physical deposition of the silver-containing layer can be carried out, for example, by vapor deposition. Preferred methods for vapor deposition are in particular electron beam deposition, laser beam deposition, arc discharge deposition or cathodic sputtering.

[0138] In step e), the masking is preferably removed.

[0139] The masking can be removed in a standard manner. For this purpose, the masking can be exposed to, for example, an alkaline solution (e.g., 2.5% sodium hydroxide solution). After removing the masking, the metal-ceramic substrate includes at least one silver-containing contact area, where the surface of the metal layer that is not provided with the silver-containing contact area is freely accessible.

[0140] The method described herein makes it possible to obtain a metal-ceramic substrate provided with structures and silver-containing contact areas. By creating the silver-containing contact areas, chips can be more easily connected to the metal-ceramic substrate using common processes such as sintering or welding. The metal-ceramic substrate obtained in this way is characterized by particularly high thermal shock resistance.

[0141] Exemplary embodiments

[0142] The present invention will be described in more detail below with the aid of exemplary embodiments, which, however, should not be construed as restrictive.

[0143] Example 1:

[0144] Example 1a – Preparation of a structured metal-ceramic substrate:

[0145] For Example 1, a copper-ceramic substrate was used, in which a ceramic body made of silicon nitride ceramic with dimensions of 177.8 mm × 139 mm × 0.32 mm was bonded to copper layers with dimensions of 170 mm × 132 mm × 0.3 mm on both sides using the AMB (active metal brazing) process. This copper-ceramic substrate was first cleaned after production.

[0146] Then, a photosensitive film was applied to the two copper layers of the copper-ceramic substrate using a hot roll laminator. The photosensitive film was exposed to 30 mJ / cm 2 in each of the areas to be masked, so as to cure the polymer contained in the photosensitive film and obtain an etching mask. Subsequently, the unexposed areas of the photosensitive film were removed in a wet chemical manner using a sodium carbonate solution (concentration = 10 g / l). After applying the etching mask, the copper-ceramic substrate was cleaned by rinsing. Subsequently, the unmasked areas of the copper layers of the copper-ceramic substrate were etched in a wet chemical manner. For this purpose, the copper-ceramic substrate was sprayed in an etching system with a copper chloride solution containing hydrochloric acid and hydrogen peroxide (copper ion content = 160 g / l). The etching was carried out at a temperature of 50 °C and a spraying pressure of 2.8 bar. By etching, the material was removed from the unmasked areas of the copper layers of the copper-ceramic substrate. Then the copper-ceramic substrate was rinsed. Then, the unmasked areas of the bonding layer contained in the copper-ceramic substrate were also etched in a wet chemical manner. For this purpose, the copper-ceramic substrate was again sprayed in an etching system with an etching solution containing ammonium fluoride, fluoboric acid and hydrogen peroxide. Then the copper-ceramic substrate was rinsed and dried. Then, the etching mask was removed using a 2.5% sodium hydroxide solution in a stripping system.

[0147] Example 1b – Preparation of a structured metal-ceramic substrate with a silver-containing contact area:

[0148] The structured copper-ceramic substrate prepared in Example 1a was provided with silver-containing contact areas. For this purpose, a mask was first applied to the structured copper layer (including the structured area) of the copper-ceramic substrate and the areas of the ceramic body exposed through the depressions in the copper layer forming the structured part (the exposed areas of the ceramic body). For this purpose, the structured copper-ceramic substrate was positioned in an inkjet printer (MicroCraft C4K7861T, Sense Advanced Technology GmbH) to apply a mask to the structured copper layer (including the structured area) and the exposed areas of the ceramic body. The areas of the structured copper layer to be kept silver-free and the exposed areas of the ceramic body in the structured area were printed with a liquid medium containing a masking agent (DiPaMAT resist ER02). Then the masking agent was cured using UV radiation (LED 390 nm, 500 mJ / cm 2 )). Thus, the areas of the structured copper layer to be kept silver-free and the exposed areas of the ceramic body were covered with a 30-μm-thick mask.

[0149] Subsequently, a silver-containing contact area is deposited on the unmasked area of the copper layer of the copper-ceramic substrate. For this purpose, the masked copper-ceramic substrate is first pretreated with a first solution containing hydrogen peroxide and sulfuric acid and then contacted with a nitric acid / silver nitrate solution (silver content = 1.0 g / l). After depositing the silver-containing contact area, the copper-ceramic substrate is carefully rinsed with water to remove any residues. Then, the mask is removed using a 2.5% sodium hydroxide solution in a stripping system.

[0150] The resulting copper-ceramic substrate is laser cut into individual parts having dimensions (20.5 mm × 17.0 mm) and can then be used for further research and production of electronic components.

[0151] Comparative Example 1:

[0152] Comparative Example 1a - Preparation of a structured metal-ceramic substrate:

[0153] In Comparative Example 1a, a structured copper-ceramic substrate is prepared similar to Example 1a.

[0154] Comparative Example 1b – Preparation of a structured metal-ceramic substrate with a silver-containing contact area:

[0155] The structured copper-ceramic substrate prepared in Comparative Example 1a is provided with a silver-containing contact area. For this purpose, a mask is first applied to the structured copper layer of the copper-ceramic substrate. For this purpose, a photosensitive film is applied to the two etched surfaces of the structured copper-ceramic substrate using a hot roll laminator. The photosensitive film is exposed to 30 mJ / cm 2 in each of the areas to be masked in order to cure the polymer contained in the photosensitive film and obtain a mask. Then, the unexposed points of the photosensitive film are removed in a wet chemical manner using a sodium carbonate solution (concentration = 10 g / l). After applying the mask, the copper-ceramic substrate is cleaned again by rinsing. Subsequently, a silver-containing contact area is deposited on the unmasked area of the copper layer of the copper-ceramic substrate. For this purpose, the masked copper-ceramic substrate is first pretreated with a first solution containing hydrogen peroxide and sulfuric acid and then contacted with a nitric acid / silver nitrate solution (silver content = 1.0 g / l). After depositing the silver-containing contact area, the copper-ceramic substrate is carefully rinsed with water to remove any residues. Then, the mask is removed using a 2.5% sodium hydroxide solution in a stripping system.

[0156] The resulting copper-ceramic substrate is laser cut into individual parts having dimensions (20.5 mm × 17.0 mm) and can then be used for further research and production of electronic components.

[0157] Evaluation:

[0158] For the copper-ceramic substrates obtained in Example 1 and Comparative Example 1, the ratio A(BCD 固体 ) / A(BCD 总 ) was determined. For this purpose, as described herein, the copper-ceramic substrates were cut perpendicular to the main boundary surface of the corresponding ceramic body, and images of the cross-sections thus obtained were taken using an optical microscope. Points A, B, C, and D were determined in the cross-section. Then, the ratio A(BCD 固体 ) / A(BCD 总 ) of each copper-ceramic substrate in the copper-ceramic substrates was determined. For this purpose, ten different cross-sections of the structured regions in the copper layer of the corresponding copper-ceramic substrates were studied, the ratio A(BCD 固体 ) / A(BCD 总 ) of each of these cross-sections was determined, and the average value of the ratio A(BCD 固体 ) / A(BCD 总 ) of each of these cross-sections was calculated to arrive at the ratio A(BCD 固体 ) / A(BCD 总 ) of the corresponding copper-ceramic substrate. In addition, the standard deviation SSD was determined.

[0159] Similarly, for the copper-ceramic substrates obtained in Example 1 and Comparative Example 1, the silver content in the region adjacent to the upper half of the contour line and the silver content in the region adjacent to the lower half of the contour line were determined by energy-dispersive X-ray spectroscopy (EDX) combined with a scanning electron microscope (SEM) (SEM-EDX) as described above.

[0160] Figure 4 An example of an optical micrograph of a cross-section showing details of the structured region of the copper layer of a copper-ceramic substrate according to Example 1 is shown, while Figure 5 An example of an optical micrograph of a cross-section showing details of the structured region of the copper layer of a copper-ceramic substrate according to Comparative Example 1 is shown.

[0161] The results are shown in Table 1.

[0162] Table 1:

[0163] <![CDATA[A(BCD 固体 ) / A(BCD 总 )]]> Standard deviation SSD Silver content (upper half) Silver content (lower half) Example 1 97.9％ 0.4％ 83 wt% 1 wt% Comparative Example 1 67.3％ 11.7％ 76 wt% 81 wt%

[0164] The thermal shock resistance of the copper-ceramic substrates was tested. For this purpose, a thermal shock resistance test was carried out.

[0165] Thermal shock resistance test:

[0166] In the preparation for the thermal shock resistance test, first, an ultrasonic microscope (PVA Tepla SAM300) is used to check whether the copper-ceramic substrate is in perfect condition. For this test, only such copper metal-ceramic substrates are used that do not show delamination between the ceramic body and the copper layer or other deformations (e.g., cracks) that could cause delamination of the copper layer from the ceramic body. To test the thermal shock resistance, the copper-ceramic substrate is repeatedly exposed in a cycling chamber (ESPEC TSB-21 51) to a cold liquid (temperature -65 °C, Galden Do2TS) and a hot liquid (temperature +150 °C, Galden Do2TS) for respective time periods of five minutes each. Every 1000 cycles, the copper-ceramic substrate is again checked for delamination and other deformations by means of an ultrasonic microscope (PVA Tepla SAM300). The test is terminated after 3000 cycles. Then, the copper-ceramic substrate is again checked for delamination and other deformations by means of an ultrasonic microscope (PVA Tepla SAM300). The state of the corresponding copper-ceramic substrate after the thermal shock resistance test is compared with the state of the copper-ceramic substrate before the thermal shock resistance test in terms of delamination and other deformations. Delamination and other deformations (e.g., cracks) are visible as white discolorations in the ultrasonic images.

[0167] The results are shown in Table 2.

[0168] Table 2:

[0169] Results of the thermal shock resistance test Example 1 Very good: No visible delamination Comparative Example 1 Poor: Significant delamination is visible at the corners of the copper-ceramic substrate

[0170] The results show that the metal-ceramic substrate according to the present invention is significantly superior to the metal-ceramic substrate of Comparative Example 1 in terms of thermal shock resistance.

[0171] List of reference numerals:

[0172] 1 Metal-ceramic substrate

[0173] 4 Structured area

[0174] 8 Contact area

[0175] 10 Ceramic body

[0176] 15 Main boundary surface of the ceramic body

[0177] 20 Metal layer

[0178] 22 Depression

[0179] 24 Main boundary surface of the metal layer

[0180] 40 Contour line

[0181] 50 Solid material

[0182] 60 silver

[0183] 200 additional metal layers

Claims

1. A metal-ceramic substrate, the metal-ceramic substrate comprising: a) A ceramic body, the ceramic body comprising a main boundary surface, b) A metal layer, the metal layer comprising a main boundary surface, wherein the metal layer is bonded to the ceramic body on the surface, and wherein the metal layer comprises a structured region, the structured region comprising (i) Solid material in the region, and (ii) Non-solid material in the region And c) A silver-containing contact region disposed on the metal layer, Characterized in that In a cross-section of the metal-ceramic substrate penetrating the main boundary surface of the ceramic body perpendicularly, the structured region has a geometry that meets the following requirements: A(BCD 固体 ) / A(BCD 总 )>70%, Where A(BCD 总 ) is the total area of the triangle described by points B, C, and D, and A(BCD 固体 ) is the area of the triangle described by points B, C, and D, the area occupied by the solid material, Where points B, C, and D are determined as follows:

1. Determine the best-fit line between the ceramic body and the metal layer; 2. Determine the contour line that separates the solid material from the non-solid material; 3. On the perpendicular line of the best-fit line, at a distance of 150 μm from the best-fit line, determine point A, at which the perpendicular line of the best-fit line intersects the contour line; 4. On the perpendicular line of the best-fit line, at a distance of 80 μm from the best-fit line, determine point B, at which the perpendicular line of the best-fit line intersects the contour line; 5. On the straight line passing through point A and point B, determine point C, at which the straight line intersects the best-fit line; and 6. On the perpendicular line of the best-fit line passing through point B, determine point D, at which the perpendicular line intersects the best-fit line; and wherein the contour line extends from the main boundary surface of the metal layer to the main boundary surface of the ceramic body, wherein the contour line includes an upper half and a lower half, wherein the upper half of the contour line extends from the main boundary surface of the metal layer towards the main boundary surface of the ceramic body, and the lower half of the contour line extends from the main boundary surface of the ceramic body towards the main boundary surface of the metal layer, and wherein the solid material in the region adjacent to the upper half of the contour line has a higher silver content than the solid material in the region adjacent to the lower half of the contour line.

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

3. The metal-ceramic substrate according to claim 1 or claim 2, characterized in that, The metal layer contains copper.

4. The metal-ceramic substrate according to any one of the preceding claims, characterized in that The solid material contains the metal of the metal layer.

5. The metal-ceramic substrate according to any one of the preceding claims, characterized in that, The non-solid material contains gaseous materials.

6. The metal-ceramic substrate according to any one of the preceding claims, characterized in that, The following requirements are met: A(BCD 固体 ) / A(BCD 总 ) > 95%.

7. The metal-ceramic substrate according to any one of the preceding claims, characterized in that The ratio on at least ten different cross-sections of the structured region of the metal layer A(BCD 固体 ) / A(BCD 总 ) has a sample standard deviation SSD of no more than 10%.

8. The metal-ceramic substrate according to any one of the preceding claims, characterized in that, of the silver content in the solid material in the region adjacent to the lower half of the contour line and the silver content in the solid material in the region adjacent to the upper half of the contour line is less than 0.

8.

9. An electronic component, the electronic component comprising a metal-ceramic substrate according to any one of the preceding claims.

Images