Metal-ceramic substrate with contact region

Abstract

The invention relates to a metal-ceramic substrate, to an electronic component comprising a metal-ceramic substrate, and to a method for producing a metal-ceramic substrate. The 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 connected on its surface to the ceramic body, and where the metal layer comprises a structured region comprising (i) a partial solid material and (ii) a partial non-solid material, and c) a contact region comprising (i) a partial solid material and (ii) a partial non-solid material, the contact region comprises silver, arranged on the metal layer, where the structured region has a geometry in a cross-section penetrating the metal-ceramic substrate perpendicular to the main boundary surface of the ceramic body, where the following requirements are satisfied: S (BC solids) / S (BC total) gt; s (BC total) represents the total length of the line between point B and point C, and S (BC solid) represents the length of the line between point B and point C that intersects 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 a metal-ceramic substrate, an electronic component including the metal-ceramic substrate, and a method for producing the metal-ceramic substrate. Background Art

[0002] Metal-ceramic substrates play an important role in the field of power electronics. They are key components when constructing electronic components and ensure rapid dissipation of a large amount of heat during operation of the components. 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, a copper compound having a melting point lower than that of copper (usually copper oxide) 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 having a melting point of at least 700 °C (usually silver) 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 using 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 reliably joined to the ceramic body. Alternatively, a silver-free solder can be used to connect the metal foil to the ceramic body. These solders are, for example, based on high melting point metals (especially copper), low melting point metals (such as bismuth, indium, or tin), and reactive metals (such as titanium). This technique is proposed, for example, in DE 102017114893 A1. This technique basically produces a new class of independent compounds because the base material of the solder used is formed of another metal (copper instead of silver), which causes changes in the material properties and creates adapted and improved bonding conditions for the other solder components.

[0005] In the construction of electronic components, metal-ceramic substrates are usually equipped with chips. To equip the metal-ceramic substrate with chips, it is generally 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 certain areas with an etching solution in order to form the desired structuring. The contact area is then provided by partially applying a silver-containing coating to the surface of the structured metal-ceramic substrate.

[0006] The metal-ceramic substrates produced in this way are often exposed to high temperature variations during operation as parts of electronic components. While during operation interruptions - depending on the environment - the temperature can be, for example, -20 °C or lower, 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 results in 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 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 ceramic body comprises a main boundary surface,

[0011] b) a metal layer, which metal layer comprises a main boundary surface, wherein the metal layer is connected to the ceramic body on its surface, and wherein the metal layer comprises a structured region, which structured region

[0012] contains

[0013] (i) a part of solid material, and

[0014] (ii) a part of non-solid material,

[0015] and

[0016] c) a contact area, which contact area contains silver and is arranged on the metal layer,

[0017] wherein

[0018] In a cross-section of the metal-ceramic substrate that penetrates the metal-ceramic substrate perpendicular to the main boundary surface of the ceramic body,

[0019] the structured region has a geometry that meets the following requirements:

[0020] S(BC 固体 ) / S(BC 总 ) > 60%

[0021] where:

[0022] S(BC 总 ) represents the total length of the line between point B and point C, and

[0023] S(BC 固体 ) represents the length of the line between point B and point C that intersects the solid material,

[0024] where point B and point C are determined as follows:

[0025] 1. Determine the best-fit line between the ceramic body and the metal layer;

[0026] 2. Determine the contour line that separates the solid material from the non-solid material;

[0027] 3. Determine point A at a distance of 150 μm from the best-fit line on the perpendicular to the best-fit line, where the perpendicular to the best-fit line intersects the contour line at point A;

[0028] 4. Determine point B at a distance of 80 μm from the best-fit line on the perpendicular to the best-fit line, where the perpendicular to the best-fit line intersects the contour line at point B; and

[0029] 5. Determine point C on the line passing through point A and point B, where the line intersects the best-fit line at point C; 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 has 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

[0031] 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.

[0032] Furthermore, the present invention relates to an electronic component that includes such a metal-ceramic substrate.

[0033] Furthermore, the present invention relates to a method for producing a metal-ceramic substrate.

[0034] The metal-ceramic substrate according to the present invention comprises a ceramic body, which comprises a main boundary surface.

[0035] 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. In the present document, the main boundary surface preferably refers to the boundary surface to which the metal layer is connected on its surface (very particularly preferably the boundary surface having the largest surface area). The main boundary surface is very particularly preferably the boundary surface to which the metal layer comprising a structured region is connected on its surface (very particularly preferably the boundary surface having the largest surface area), and very particularly preferably the boundary surface to which the metal layer on which a silver-containing contact region is arranged is connected on its surface (in particular the boundary surface having the largest surface area). The main boundary surface preferably lies in the main extension plane of the ceramic body or extends parallel to this main extension plane. Thus, the main extension plane of the ceramic body is preferably understood as a plane that extends parallel to the main boundary surface of the ceramic body or encloses the main boundary surface.

[0036] 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.

[0037] 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.

[0038] The metal-ceramic substrate according to the invention comprises a metal layer which comprises a main boundary surface, wherein the metal layer is connected to the ceramic body on its surface, and wherein the metal layer comprises a structured region which contains (i) a part of solid material and (ii) a part of non-solid material.

[0039] 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 surface area). Accordingly, the main boundary surface preferably refers to the boundary surface on which the contact region containing silver is arranged (very particularly preferably the boundary surface having the largest surface area). The main boundary surface preferably lies in the main extension plane of the metal layer or extends parallel to the main extension plane. Accordingly, 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.

[0040] The metal layer is preferably bonded to the ceramic body as a whole. 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 connected to the ceramic body via a soldering process. The soldering process can be, for example, an AMB (active metal brazing) process, wherein preferably 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%) is used. Accordingly, the metal layer may also comprise a bonding layer in contact with the ceramic body. The bonding layer can be, for example, a welding layer (especially a brazing layer) or a diffusion layer.

[0041] The metal layer is connected to the ceramic body on its surface. Correspondingly, the metal layer is preferably connected to the main boundary surface of the ceramic body on its surface. The metal layer is preferably not connected 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 connected 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 recesses in the metal layer which separate the individual parts of the metal layer from one another and thereby electrically insulate these parts. Such structuring is often created using etching techniques.

[0042] Correspondingly, the metal layer comprises a structured region. The structured region is the part of the metal layer containing the structuring. The structuring is preferably a recess in the metal layer. Accordingly, the main boundary surface of the metal layer contains the metal of the metal layer, which is interrupted by the recesses in the structured region.

[0043] The structured region includes a region containing a solid material and a region containing a non-solid material.

[0044] 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.

[0045] 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. Most preferably, the gaseous material is a gas mixture, especially air.

[0046] 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.

[0047] The metal layer preferably contains at least one metal selected from the group consisting of copper, aluminum, and molybdenum. According to another 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%.

[0048] According to a preferred embodiment, the metal layer is produced by bonding a copper foil (preferably a foil made of high-purity copper) to the ceramic body. According to a preferred embodiment, the connection 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, in which preferably 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%) is used. In this case, in addition to the copper from the copper foil, the metal layer can also contain the metal of the bonding layer, especially the metal of the welding layer (such as the brazing layer) or the diffusion layer.

[0049] 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.

[0050] The metal-ceramic substrate according to the invention comprises a contact area which contains silver and is arranged on the metal layer. The contact area is preferably used to facilitate the connection of the chip to the metal layer. The chip is preferably connected to the metal layer by sintering, soldering or bonding. Since it is particularly difficult to attach the metal of the chip to the metal layer of the metal-ceramic substrate, 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, the silver-containing alloy contains at least 50% by weight of silver, based on the weight of the silver alloy. Preferably, the contact area is provided at all positions on the metal layer of the metal-ceramic substrate where the metal-ceramic substrate is later to be equipped with a chip. The contact area can be formed on the metal layer of the metal-ceramic substrate using different techniques. For example, the contact area can be provided by depositing 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. Preferably, the chemical deposition of the silver-containing layer is carried out electrolessly by applying a silver-containing solution in which a charge exchange takes place between the metals, where 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 is 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.

[0051] The structured area of the metal layer of the metal-ceramic substrate has the geometry described herein. The geometry of the structured area is determined in a cross-section through the metal-ceramic substrate perpendicular to the main boundary surface of the ceramic body.

[0052] In a cross-section through the metal-ceramic substrate perpendicular to the main boundary surface of the ceramic body, the structured area of the metal layer has a geometry in which the following requirements are met:

[0053] S(BC 固体 ) / S(BC 总 )>60%

[0054] where:

[0055] S(BC 总 ) represents the total length of the line between point B and point C, and

[0056] S(BC 固体 ) represents the length of the line intersecting the solid material between point B and point C.

[0057] According to a preferred embodiment, the structured region of the metal layer in a cross-section perpendicular to the main boundary surface of the ceramic body and passing through the metal-ceramic substrate has a geometry, where the ratio S(BC 固体 ) / S(BC 总 ) > 70%, more preferably > 80%, even more preferably > 85%, particularly preferably > 90% and very particularly preferably > 95%.

[0058] According to another preferred embodiment, the structured region of the metal layer in a cross-section perpendicular to the main boundary surface of the ceramic body and passing through the metal-ceramic substrate has a geometry, where the ratio S(BC 固体 ) / S(BC 总 ) is in the range of 70% to 100%, particularly preferably in the range of 80% to 100% and very particularly preferably in the range of 80% to 99%.

[0059] To determine points B and C, a 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 capturing an image of the resulting cross-section by an optical microscope.

[0060] Points B and C of line BC can be determined in the cross-section as described below.

[0061] For illustrative purposes, reference is made to Figure 1 and Figure 2 as examples. Description of the Drawings

[0062] Figure 1 A schematic diagram of this type of metal-ceramic substrate is shown.

[0063] Figure 2 A metal-ceramic substrate according to the invention with a structured region is schematically shown, 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.

[0064] Figure 3 A part of a cross-section through the metal-ceramic substrate according to the invention is shown.

[0065] Figure 4 An example of an optical micrograph of a part of a cross-section of the structured region of the copper layer of a copper-ceramic substrate according to Example 1 is shown.

[0066] Figure 5 Shows an example of an optical micrograph of a cross-section of a structured region of the copper layer of a copper-ceramic substrate according to Comparative Example 1. Detailed Description

[0067] 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 connected to the main boundary surface 15 of the ceramic body 10 on its surface. In accordance with Figure 1 In an embodiment of, the metal-ceramic substrate 1 further includes an additional metal layer 200 that is connected to the ceramic body 10 on its 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 region 4 partially includes the metal of the metal layer 20 and the recess 22. Accordingly, the structured region 4 partially contains a solid material 50 and a non-solid material (such as a gaseous material), the solid material being formed by the metal of the metal layer 20 and the non-solid material filling the recess 22. The gaseous material tends to be 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, which is interrupted by the recess 22 in the structured region. 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.

[0068] 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 has 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 towards 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 towards the main boundary surface 24 of the metal layer 20. The solid material 50 contains silver 60 in the region adjacent to the upper half of the contour line 40. In the region adjacent to the lower half of the contour line 40, the solid material contains no or less silver 60.

[0069] In Figure 3In the portion of the cross-section through the metal-ceramic substrate according to the present invention shown, a part of the structured region can be seen. The region of the ceramic body 10 where it is connected to the metal layer 20 on its surface is shown. The contour line 40 separates the solid material 50 from the non-solid material of the recess 22 in the metal layer 20.

[0070] The determination of points B and C of line BC in the cross-section is preferably carried out in a plurality of steps:

[0071] In a first step, the best-fit line 30 between the ceramic body 10 and the metal layer 20 is determined. For this purpose, the regions 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.

[0072] In a second step, the contour line 40 is determined, which separates the solid material 50 from the non-solid material of 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 optically determined. The non-solid material is often a gaseous material that is used to fill the structured part - as the recess 22 in the metal layer 20.

[0073] In a third step, point A is determined at a distance of 150 μm from the best-fit line 30 on the perpendicular to the best-fit line 30, at which point the perpendicular to the best-fit line 30 intersects the contour line 40.

[0074] In a fourth step, point B is determined at a distance of 80 μm from the best-fit line 30 on the perpendicular to the best-fit line 30, at which point the perpendicular to the best-fit line 30 intersects the contour line 40.

[0075] In a fifth step, point C is determined on the straight line passing through points A and B, at which point the straight line intersects the best-fit line 30.

[0076] The cross-section of the metal-ceramic substrate perpendicular to the main boundary surface of the ceramic body and the capture of the image of the cross-section thus obtained by an optical microscope (incident light / bright field) are preferably carried out as follows:

[0077] In a 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 formed by the main boundary surface of the ceramic body of the metal-ceramic substrate, and first a piece including between 100 mm 2 up to 400 mm 2A cubic sample blank with a rectangular base within the range. The sample blank accordingly includes a sample surface, which is supplied for research. Thus, before sawing, the sample surface extends perpendicular to the plane formed by the main boundary surface of the ceramic body of the metal-ceramic substrate. Therefore, it includes parts on the ceramic body and on the metal layer (including an optionally present 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 oven at 75 °C. After curing, the sample surface of the sample blank is mechanically polished with an automatic polishing device (Tegrapole, Struers) to obtain a roughness of 1 μm or less.

[0078] In a second step, a structured region containing a part of solid material and a part of non-solid material is identified in the metal layer at a magnification of 200x in the analysis region using an optical microscope (Leica, DM6000M, incident light / bright field). The solid material and the non-solid material can be clearly distinguished in the structured region due to different colors.

[0079] The length S(BC 总 ) and S(BC 固体 ) are preferably determined in a standard manner, for example, using image analysis software (such as IMS Client, Imagic).

[0080] Preferably, as used herein, the term "in cross-section" 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 in particular ten cross-sections. The cross-sections preferably extend parallel to each other and are evenly spaced from each other.

[0081] To determine the ratio S(BC 固体 ) / S(BC 总 ) of the observed metal-ceramic substrate, the following procedure is preferably used:

[0082] 1. Examine at least ten, particularly preferably ten, different cross-sections of the structured region;

[0083] 2. Determine the ratio S(BC 固体 ) / S(BC 总 ) for each of these cross-sections; and

[0084] 3. Average the ratio S(BC 固体 ) / S(BC 总 ) for each of these cross-sections to obtain the ratio S(BC 固体) / S(BC 总 )。

[0085] According to a preferred embodiment, on at least ten different cross-sections of the structured region of the metal layer, more preferably on no more than 20 different cross-sections of the structured region of the metal layer, and very particularly preferably on ten different cross-sections of the structured region of the metal layer, the ratio S(BC 固体 ) / S(BC 总 ) has a sample standard deviation SSD of not more than 10%, more preferably not more than 7%, particularly preferably not more than 5%, and very particularly preferably not more than 3%. The sample standard deviation SSD is determined using the following formula:

[0086]

[0087] where:

[0088] n = the number of individual values of the ratio S(BC 固体 ) / S(BC 总 ),

[0089] X i = a single value of the ratio S(BC 固体 ) / S(BC 总 ), and

[0090] is the average value of the individual values.

[0091] According to the invention, in a cross-section through the metal-ceramic substrate perpendicular to the main boundary surface of the ceramic body, the structured region has a geometry in which 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 has 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.

[0092] Thus, according to the 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. Thus, 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.

[0093] The contour line has an upper half and a lower half. 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. The lower half of the contour line extends from the main boundary surface of the ceramic towards the main boundary surface of the metal layer.

[0094] According to the present 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.

[0095] 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 by the above method 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 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. Thus, the region of the solid material to be measured consists of an upper half adjacent to the upper half of the contour line and a lower half adjacent to the lower half of the contour line.

[0096] 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).

[0097] In SEM-EDX, a focused primary electron beam is scanned point by point (scanned) 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, wherein the elements in the sample and their weight ratios can be determined by analyzing the energy spectrum using an EDX detector.

[0098] 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) was used. For the scanning electron microscope, the following settings can be used: magnification: 200x, acceleration voltage = 10 kV, working distance = 10 mm, spot size (50 - 60) (set to achieve a dwell time at the EDX detector of 25% + / - 5%). The following settings of the EDX detector can be used to capture the EDX spectrum: real time = 30 s, rate = automatic, low energy cut-off = 100 keV, high energy cut-off = automatic (per SEM acceleration voltage). Depending on the magnification selected and the thickness of the metal layer, multiple SEM-EDX measurements may be required to image the entire structured area.

[0099] 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.

[0100] Surprisingly, it was 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 have a high proportion of solid material in the metal layer at the boundary with the surface of the ceramic body. In contrast, it was found that if the metal-ceramic substrates from the prior art include a silver-containing contact area 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.

[0101] Not bound by explanations, this may be due to the fact that in the prior art, the produced metal-ceramic substrate is often first structured and then silver-plated on the surface to create contact areas; however, the already structured areas on the surface of the metal-ceramic substrate are only insufficiently masked during silver plating. For this purpose, the areas on the surface of the structured metal-ceramic substrate that are not coated with silver are often first masked 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 carried out by immersing the structured and masked metal-ceramic substrate in a bath containing a solution with silver ions. The solution containing silver ions 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 spatially separated areas close to the ceramic body. Therefore, the deposition of silver usually occurs 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 about at most 50 μm from the surface of the ceramic body), such that as the contact time with the solution containing silver ions progresses, the surface 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 a weakness that causes the metal layer to peel off from the ceramic body, which has an adverse effect on the thermal shock resistance. Therefore, 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 the peeling off of the metal layer from the ceramic body can be prevented and an improvement in the thermal shock resistance can be achieved.

[0102] 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, a mask 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 with the mask in the area close to the ceramic body, which improves the thermal shock resistance. In contrast, the area of the structured portion far from the ceramic body is often not completely masked, such that this area is at least partially coated with silver in the subsequent silver plating step.

[0103] According to a preferred embodiment, the metal-ceramic substrate comprises a further (second) metal layer which is connected on its surface to the ceramic body. This further metal layer is preferably connected on its surface to a boundary surface which faces away from the main boundary surface of the ceramic body (and preferably extends parallel to this main boundary surface). The further (second) metal layer can have the same properties as the (first) metal layer or can 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 with regard to the (first) metal layer.

[0104] The metal-ceramic substrate according to the invention can be used in particular for electronic applications, especially in the field of power electronics.

[0105] Accordingly, the invention also provides an electronic component which comprises a metal-ceramic substrate according to the invention.

[0106] 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 connected on its surface to a silver-containing contact area 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 a silver-containing contact area.

[0107] According to another preferred embodiment, the metal-ceramic substrate of the electronic component comprises a further (second) metal layer. This further (second) metal layer is preferably connected on its surface to the ceramic body. In this case, the further metal layer is preferably connected 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 this main boundary surface).

[0108] According to another preferred embodiment, the electronic component comprises a substrate. The substrate is preferably connected 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 designed as a heat sink.

[0109] 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 this further metal layer is preferably connected 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 connected on its surface to the first metal layer of the metal-ceramic substrate via a silver-containing contact area arranged on this metal layer, and the substrate is connected on its surface to the further (second) metal layer of the metal-ceramic substrate.

[0110] The metal-ceramic substrate according to the invention can be obtained by different manufacturing processes.

[0111] The present invention also provides a method for producing a metal-ceramic substrate provided with a structured portion and a contact area containing silver.

[0112] The method for producing a metal-ceramic substrate provided with a structured portion and a contact area containing silver comprises the following steps:

[0113] a) providing a metal-ceramic substrate comprising:

[0114] a1) a ceramic body, and

[0115] a2) a metal layer which is connected to the ceramic body on its surface,

[0116] b) structuring the metal layer,

[0117] c) applying a mask to the structured metal layer by applying a liquid medium containing a masking agent to the structured metal layer in certain areas and curing the masking agent,

[0118] d) depositing a silver-containing layer on the unmasked areas of the structured metal layer to obtain a contact area containing silver, and

[0119] e) removing the mask.

[0120] In step a), a metal-ceramic substrate is first provided.

[0121] The metal-ceramic substrate comprises a ceramic body and a metal layer which is connected to the ceramic body on its surface. The metal-ceramic substrate can be a standard metal-ceramic substrate. The ceramic body and the metal layer can have the compositions as described above with respect to the metal-ceramic substrate. The metal layer can preferably be integrally bonded to the ceramic body, also as described above with respect to the metal-ceramic substrate.

[0122] In step b), the metal layer is structured.

[0123] The structured part is preferably understood to mean recesses in the metal layer that separate the various parts of the metal layer from each other and thus electrically insulate these parts. Accordingly, the structured part preferably exposes regions of the ceramic body. Such structured parts are often created using etching techniques. For example, an etching mask may first be applied to the metal layer. The etching mask is used to protect the masked regions of the metal layer from etching during the etching step. This ensures that only those unmasked regions of the metal layer of the metal-ceramic substrate that are intended for structuring can be etched. Accordingly, the etching mask is designed in such a way that the masked regions of the metal layer are not etched during the etching step. No further limitation is placed on the type of etching mask. The etching mask may be, for example, a standard negative mask or a positive mask. Standard resists may be used to produce the etching mask. These resists preferably contain curable polymers (such as photocurable polymers) and may 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 may be processed in a suitable manner (such as by curing with light irradiation) to obtain the etching mask. According to one possible embodiment, a photosensitive film is applied to the metal layer of the metal-ceramic substrate and then exposed to the regions to be masked in order to obtain the etching mask. The unexposed regions of the photosensitive film may then be removed in a conventional manner (such as using a sodium carbonate solution).

[0124] After the etching mask has been applied to the metal layer, the unmasked regions of the metal layer are preferably etched to obtain the structured part. The etching is preferably carried out in a standard conventional manner. Accordingly, a standard etching solution is preferably used for the etching. According to a preferred embodiment, the etching solution is selected from the group consisting of FeCl3 etching solution and CuCl2 etching solution. If desired, additional etching solutions may be used, for example, to structure the unmasked regions of an optionally included bonding layer. According to a preferred embodiment, the additional etching solution may be selected from the group consisting of etching solutions containing hydrogen peroxide and etching solutions containing ammonium persulfate. For example, the additional etching solution may be an etching solution containing ammonium fluoride and fluoboric acid (such as HBF4) as well as hydrogen peroxide and / or ammonium persulfate.

[0125] Preferably, after the unmasked regions of the metal layer have been etched to obtain the structured part, the etching mask is removed. The etching mask may be removed in a standard manner. For this purpose, the metal-ceramic substrate may be treated, for example, with an alkaline solution (such as a 2.5% sodium hydroxide solution) to remove the etching mask.

[0126] In step c), a mask is applied to the structured metal layer by applying a liquid medium containing a masking agent to certain regions of the structured metal layer and curing the masking agent.

[0127] The mask is used to protect the masked areas of the metal layer from the deposition of the silver-containing layer in step d). This ensures that the silver-containing layer is deposited only on the unmasked areas of the metal layer of the metal-ceramic substrate. Thus, the mask 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.

[0128] According to a preferred embodiment, the structured metal layer to which the mask is applied further includes 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 near the ceramic body are also provided with a mask in order to protect these areas from being dissolved during the deposition of the silver-containing layer in step d), especially when in contact with a solution containing silver ions.

[0129] To apply the mask, a liquid medium containing a masking agent is applied to the structured metal layer in certain areas and the masking agent is cured.

[0130] 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.

[0131] 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 curable by UV. The UV-curable masking agent preferably includes at least one compound selected from the group consisting of monomers and oligomers. According to a particularly preferred embodiment, the UV-curable masking agent includes 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 reactive substances 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.

[0132] The liquid medium containing the masking agent is applied to the structured metal layer in certain 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).

[0133] 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.

[0134] After applying the liquid medium, the masking agent contained therein is preferably cured. For this purpose, the masking agent is preferably cured. The curing can be achieved, for example, by irradiating the liquid medium with UV light so that the masking agent contained in the liquid medium (in particular monomers or oligomers) polymerizes.

[0135] 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, particularly before depositing a silver-containing layer on the unmasked areas of the structured metal layer in accordance with step d) to obtain silver-containing contact areas, 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 areas of the structured metal layer and (if appropriate) the areas 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 is applied to the structured metal layer in the additional masking step, preferably as a layer, particularly over the entire surface, where the cured masking agent is removed in the subsequent subtractive masking step in the areas of the structured metal layer (on which the silver-containing layer is deposited in a 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 silver-containing contact areas is advantageously provided.

[0136] According to a preferred embodiment, in step c), the mask is also applied to the areas 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 these areas and curing the masking agent. Applying the mask to the exposed areas of the ceramic body can be advantageous in order to protect the exposed areas of the ceramic body from the deposition of the silver-containing layer in step d).

[0137] Applying the mask to the structured metal layer and applying the mask to the areas of the ceramic body exposed by the recesses in the metal layer forming the structure can be carried out simultaneously or sequentially.

[0138] In order to apply the mask to the areas 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.

[0139] In step d), a silver-containing layer is deposited on the unmasked areas of the structured metal layer to obtain silver-containing contact areas.

[0140] The silver-containing layer is preferably 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. Preferably, the chemical deposition of the silver-containing layer is carried out electrolessly by applying a silver-containing solution in which a charge exchange occurs between metals, where a part of the metal of the metal layer dissolves, and at the same time 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 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.

[0141] In step e), the mask is removed.

[0142] The mask can be removed in a standard manner. For this purpose, the mask can be exposed to an alkaline solution (e.g., 2.5% sodium hydroxide solution). After removing the mask, 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.

[0143] The method shown herein makes it possible to obtain a metal-ceramic substrate provided with a structure and a silver-containing contact area. By creating the silver-containing contact area, it is possible to bond the chip to the metal-ceramic substrate more easily using common processes such as sintering or welding. The metal-ceramic substrate obtained in this way is characterized by particularly high thermal shock resistance.

[0144] Exemplary embodiments

[0145] The present invention will be described in more detail below with the aid of exemplary embodiments, which, however, should not be construed as restrictive.

[0146] Example 1 :

[0147] Example 1a - Preparation of a structured metal-ceramic substrate :

[0148] For Example 1, a metal-ceramic substrate was used. In this metal-ceramic substrate, 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.

[0149] 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 masked area to be masked, so as to harden the polymer contained in the photosensitive film and obtain an etching mask. Subsequently, the unexposed area of the photosensitive film was 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 area of the copper layer of the copper-ceramic substrate was etched in a wet chemical manner. For this purpose, the copper-ceramic substrate was sprayed in an etching system with a hydrochloric acid / copper chloride solution containing 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 area of the copper layer of the copper-ceramic substrate. Then the copper-ceramic substrate was rinsed. Then, the unmasked area of the bonding layer contained in the copper-ceramic substrate was also etched in a wet chemical manner. For this purpose, the copper-ceramic substrate was again sprayed in the 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.

[0150] Example 1b - Preparation of a structured metal-ceramic substrate with a contact area containing silver :

[0151] The structured copper-ceramic substrate prepared in Example 1a was provided with a contact area containing silver. For this purpose, a mask was first applied to the structured copper layer (including the structured area) of the copper-ceramic substrate and the area of the ceramic body exposed through the recesses in the copper layer forming the structured part (the exposed area 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 the mask to the structured copper layer (including the structured area) and the exposed area of the ceramic body. The areas of the structured copper layer to be kept silver-free and the exposed area of the ceramic body 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 area of the ceramic body were covered with a 30-μm-thick mask.

[0152] Subsequently, the silver-containing contact region is deposited on the unmasked region 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 region, the copper-ceramic substrate is carefully rinsed with water to remove any residues. Then, a 2.5% sodium hydroxide solution is used in a stripping system to remove the mask.

[0153] The resulting copper-ceramic substrate is laser cut into individual parts with dimensions (20.5 mm × 17.0 mm) and can then be used for further research and production of electronic components.

[0154] Comparative Example 1 :

[0155] Comparative Example 1a - Preparation of a structured metal-ceramic substrate :

[0156] In Comparative Example 1a, a structured copper-ceramic substrate is prepared similar to Example 1a.

[0157] Comparative Example 1b - Preparation of a structured metal-ceramic substrate with a contact area containing silver :

[0158] The structured copper-ceramic substrate prepared in Comparative Example 1a is provided with a contact region containing silver. For this purpose, a mask is first applied to the structured copper layer (including the structured region) of the copper-ceramic substrate and the region of the ceramic body exposed through the recesses in the copper layer forming the structured portion (the exposed region of the ceramic body). 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 regions to be masked so that the polymer contained in the photosensitive film hardens and a mask is obtained. Then, a sodium carbonate solution (concentration = 10 g / l) is used to wet-chemically remove the unexposed regions of the photosensitive film. After applying the mask, the copper-ceramic substrate is cleaned again by rinsing. Subsequently, the silver-containing contact region is deposited on the unmasked region 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 region, the copper-ceramic substrate is carefully rinsed with water to remove any residues. Then, a 2.5% sodium hydroxide solution is used in a stripping system to remove the mask.

[0159] The resulting copper-ceramic substrate is laser cut into individual parts with dimensions (20.5 mm × 17.0 mm) and can then be used for further research and production of electronic components.

[0160] Evaluation :

[0161] For the copper-ceramic substrates obtained in Example 1 and Comparative Example 1, the ratio S(BC 固体 ) / S(BC 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 captured by optical microscopy. Points A, B, and C were determined in the cross-section. Then, the ratio S(BC 固体 ) / S(BC 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 examined, the ratio S(BC 固体 ) / S(BC 总 ) of each of these cross-sections was determined, and the average value of the ratio S(BC 固体 ) / S(BC 总 ) of each of these cross-sections was calculated in order to arrive at the ratio S(BC 固体 ) / S(BC 总 ) of the corresponding copper-ceramic substrate. In addition, the standard deviation SSD was determined.

[0162] 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.

[0163] Figure 4 An example of an optical micrograph of a cross-section of a part 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 of a part of the structured region of the copper layer of a copper-ceramic substrate according to Comparative Example 1 is shown.

[0164] The results are shown in Table 1.

[0165] Table 1 :

[0166] <![CDATA[S(BC 固体 ) / S(BC 总 )]]> Standard deviation SSD Silver content, upper half Silver content, lower half Example 98.1％ 0.6％ 85 wt% 1 wt% Comparative Example 58.4％ 12.7％ 76 wt% 81 wt%

[0167] The thermal shock resistance of the copper-ceramic substrates was tested. For this purpose, a thermal shock resistance test was conducted.

[0168] Thermal shock resistance test :

[0169] In preparation for the thermal shock resistance test, an ultrasonic microscope (PVA Tepla SAM300) is first used to check whether the copper-ceramic substrate is in perfect condition. For this test, only such copper-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 substrates are 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. After every 1000 cycles, the copper-ceramic substrates are again checked for delamination and other deformations with the aid of an ultrasonic microscope (PVA Tepla SAM300). The test is terminated after 3000 cycles. Then the copper-ceramic substrates are again checked for delamination and other deformations with the aid of an ultrasonic microscope (PVA Tepla SAM300). The state of the respective copper-ceramic substrates after the thermal shock resistance test is compared with the state of the copper-ceramic substrates before the thermal shock resistance test with respect to delamination and other deformations. Delamination and other deformations (e.g., cracks) are visible as white discolorations in the ultrasonic images.

[0170] The results are shown in Table 2.

[0171] Table 2 :

[0172]

[0173]

[0174] The results show that the metal-ceramic substrates according to the invention are significantly superior to the metal-ceramic substrates of Comparative Example 1 with respect to thermal shock resistance.

[0175] List of reference numerals :

[0176] 1 Metal-ceramic substrate

[0177] 4 Structured area

[0178] 8 Contact area

[0179] 10 Ceramic body

[0180] 15 Main boundary surface of the ceramic body

[0181] 20 Metal layer

[0182] 22 Depression

[0183] 24 Main boundary surface of the metal layer

[0184] 40 Contour line

[0185] 50 Solid material

[0186] 60 Silver

[0187] 200 Additional metal layer

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 connected to the ceramic body on its surface, and wherein the metal layer comprises a structured region, the structured region comprising (i) A part of solid material, and (ii) A part of non-solid material, And c) A contact area, the contact area containing silver, disposed on the metal layer, characterized in that, In a cross-section of the metal-ceramic substrate that penetrates the metal-ceramic substrate perpendicular to the main boundary surface of the ceramic body, the structured region has a geometric shape, wherein the following requirements are met: S(BC 固体 ) / S(BC 总 ) > 60%, Wherein: S(BC 总 ) represents the total length of the line between point B and point C, and S(BC 固体 ) represents the length of the line between point B and point C that intersects the solid material, wherein point B and point C 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. Determine point A at a distance of 150 μm from the best - fit line on the perpendicular line to the best - fit line, where the perpendicular line to the best - fit line intersects the contour line at point A; 4. Determine point B at a distance of 80 μm from the best - fit line on the perpendicular line to the best - fit line, where the perpendicular line to the best - fit line intersects the contour line at point B; And 5. Determine point C on the straight line passing through point A and point B, where the straight line intersects the best - fit line at point C; 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 has 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, characterized in that, The ceramic of the ceramic body is selected from the group consisting of aluminum nitride ceramic, silicon nitride ceramic, and alumina ceramic.

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 a gaseous material.

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

7. The metal-ceramic substrate according to any one of the preceding claims, characterized in that, The sample standard deviation SSD of the ratio S(BC 固体 ) / S(BC 总 ) on at least ten different cross-sections of the structured region of the metal layer is not greater than 10%.

8. The metal-ceramic substrate according to any one of the preceding claims, characterized in that, 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.

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

10. A method for producing a metal - ceramic substrate provided with a structured portion and a silver - containing contact region, the method comprising the following steps: a) Provide a metal - ceramic substrate, the metal - ceramic substrate comprising: a1) A ceramic body, and a2) A metal layer, the metal layer being connected to the ceramic body on its surface, b) Structure the metal layer, c) Apply a mask to the structured metal layer by applying a liquid medium containing a masking agent to certain regions of the structured metal layer and curing the masking agent, d) Deposit a silver - containing layer on the unmasked regions of the structured metal layer to obtain a silver - containing contact region, and e) Remove the mask.

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