Metal-ceramic substrate with contact region

Abstract

The invention relates to a metal-ceramic substrate and an electronic component including the same. The invention relates to a metal-ceramic substrate comprising: a) a ceramic body having a main plane of extension, b) a metal layer connected in a planar manner to the ceramic body, the metal layer having a structured region comprising (i) a solid material in some regions and (ii) a non-solid material in some regions, and c) a contact region arranged on the metal layer and comprising silver, characterized in that, in a cross-section running through the metal-ceramic substrate perpendicular to the main extension plane, the structured region has a geometry satisfying the following requirements: A (BCD solids) / A (BCD total) gt; a (BCD total) represents the total area of the triangle described by point B, point C and point D, and A (BCD solid) represents the area of the triangle described by point B, point C and point D, the area being occupied by the solid material.

Description

[0001] The present invention relates to a metal-ceramic substrate and an electronic component including the metal-ceramic substrate.

[0002] Metal-ceramic substrates play an important role in the field of power electronics. They are a key element when building electronic components and ensure that large amounts of heat are quickly dissipated during the operation of the components. Metal-ceramic substrates usually consist of a ceramic layer and a metal layer bonded to the ceramic layer.

[0003] Several methods for bonding metal layers to ceramic layers are known from the prior art. In the so-called DCB ("direct copper bonding") method, a copper compound (usually copper oxide) having a lower melting point than copper is provided on the surface of the 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 fired, the copper compound melts and wets the surface of the ceramic body, so that a stable integral bond is obtained 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) with a melting point of at least 700°C and an active metal. The role of the active metal is to react with the ceramic material, and thus promote the bonding of the ceramic material to the remaining solder, for forming a reaction layer, and the metal with 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% to 89% by weight of silver and copper, bismuth and active metals to bond copper foil to a ceramic body. With this method, copper foil can be stably attached to a ceramic body. Alternatively, a silver-free solder can be used to bond the metal foil to a ceramic body. These solders are based, for example, on high melting point metals (especially copper), low melting point metals (such as bismuth, indium or tin) and active metals (such as titanium). This technology is proposed, for example, in DE 102017114893A1. This technology essentially creates a new, separate class of compounds, since the base of the solder used is formed from another metal (copper instead of silver), which leads to changes in the material properties and creates adaptations to other solder compositions and improved joining conditions.

[0005] When constructing electronic components, metal-ceramic substrates are often equipped with chips. In order to equip the metal-ceramic substrate with a chip, it is often necessary to provide the area of ​​the metal-ceramic substrate to be equipped with the chip with a silver-containing contact area. By providing this silver-containing contact area, the chip can be more easily bonded to the metal-ceramic substrate using common methods such as sintering or welding. In order to create the contact area, the metal-ceramic substrate is often first treated with an etching solution in the area to form the desired structured portion. The contact area is then provided by partially applying a silver-containing coating to the surface of the structured metal-ceramic substrate.

[0006] Metal-ceramic substrates produced in this way are often exposed to high temperature variations during operation as parts of electronic components. While during interruptions in operation - depending on the environment - the temperature may be, for example, -20°C or lower, the temperature of the metal-ceramic substrate can easily rise to more than 150°C during operation. Metal-ceramic substrates are often exposed to these temperature differences. Due to the different thermal expansion coefficients of metal and ceramic, repeated temperature changes may cause the metal layer to fall off (peel off) 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 desired to further improve the thermal shock resistance of metal-ceramic substrates.

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

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

[0010] a) a ceramic body comprising a main extension plane,

[0011] b) a metal layer, the metal layer being extensively bonded to the ceramic body, the metal layer comprising a structured region comprising

[0012] (i) some solid material, and

[0013] (ii) Some non-solid materials

[0014] as well as

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

[0016] It is characterized in that

[0017] In a cross section through the metal-ceramic substrate perpendicular to the main extension plane, the structured region has a geometry that meets the following requirements:

[0018] A(BCD 固体 ) / A(BCD 总 )>70%,

[0019] in

[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 the solid material,

[0022] 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 a contour line that separates the solid material from the non-solid material;

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

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

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

[0028] 6. On the perpendicular line of the best fit line passing through point B, determine point D, at which point D,

[0029] The vertical line intersects the best fit line.

[0030] Furthermore, the present invention relates to an electronic component comprising such a metal-ceramic substrate and a chip.

[0031] The metal-ceramic substrate according to the invention comprises a ceramic body which comprises a main extension plane.

[0032] The ceramic body is preferably a body formed of ceramic. The body may have any geometric shape, but is preferably designed as a cube. The ceramic body includes boundary surfaces, including six boundary surfaces in the case of a cube. In this article, the main boundary surface preferably refers to the boundary surface with the largest surface area, which is widely bonded to the metal layer. The main boundary surface is preferably located in the main extension plane 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 the main boundary surface of the ceramic body or encapsulating the main boundary surface.

[0033] 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 aluminum oxide 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) unavoidable impurities. According to yet another very particularly preferred embodiment, the ceramic body is free of bismuth, gallium and zinc.

[0034] 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.

[0035] The metal-ceramic substrate according to the present invention comprises a metal layer which is extensively bonded to the ceramic body, wherein the metal layer has a structured region comprising (i) partly solid material and (ii) partly non-solid material.

[0036] The metal layer is preferably integrally 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) method. According to another preferred embodiment, the metal layer is bonded to the ceramic body via a brazing process. The brazing process may, for example, be an AMB (active metal brazing) method, 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 %). Therefore, the metal layer may also include a bonding layer in contact with the ceramic body. The bonding layer may be, for example, a welding layer (particularly a brazing layer) or a diffusion layer.

[0037] The metal layer is extensively bonded to the ceramic body. Accordingly, the metal layer is preferably extensively bonded to the main boundary surface of the ceramic body. 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. In addition, the metal layer is preferably structured. The structured portion is preferably understood to mean a recessed portion in the metal layer so as to separate the various parts of the metal layer from each other and thus to electrically insulate these parts. Such structured portions are often created using etching techniques.

[0038] The metal layer thus has a structured region. The structured region is understood to be a part of the metal layer that contains a structuring. The structuring is preferably a depression in the metal layer.

[0039] The metal layer also has a main metal surface on the upper side (preferably facing away from the main boundary surface of the ceramic body) parallel to the main boundary surface of the ceramic body. This main metal surface therefore contains the metal of the metal layer, which is interrupted by the depression in the structured area.

[0040] The structured region has regions comprising solid material and regions comprising non-solid material.

[0041] The region comprising solid material preferably contains at least one member of the group consisting of: (i) the metal of the metal layer (optionally including the bonding layer, if present, for example in the case of an AMB); (ii) the metal of the contact region (particularly silver); and (iii) the material of the ceramic body. Thus, the solid material preferably contains (i) the metal of the metal layer (optionally including the bonding layer); and optionally (ii) the metal of the contact region (particularly silver); and / or (iii) the material of the ceramic body.

[0042] According to a preferred embodiment, the structured area between the main metal surface of the ceramic body (except the contact area) and the main boundary surface does not contain the main metal of the contact area, in particular does not contain silver. According to another preferred embodiment, the solid material of the structured area between the main metal surface of the ceramic body (except the contact area) and the main boundary surface does not contain deposits of the main metal of the contact area (in particular silver). Therefore, according to a particularly preferred embodiment, the solid material of the structured area between the main metal surface of the ceramic body (except the contact area) and the main boundary surface does not have a layer made of the main metal of the contact area (in particular silver). The main metal of the contact area is preferably the metal with the highest weight proportion in the contact area.

[0043] The area containing the non-solid material preferably contains a gaseous material. Therefore, the non-solid material preferably comprises a gaseous material. The non-solid material is preferably a gaseous material that fills the recess in the metal layer. Such a gaseous material often comes from the ambient atmosphere. Preferably, the gaseous material therefore contains at least one element selected from the group consisting of nitrogen, oxygen and a rare gas. The gaseous material is very particularly preferably air.

[0044] According to a preferred embodiment, the depression extends from the main boundary surface of the ceramic body to the main metal surface in a direction perpendicular to the main boundary surface of the ceramic body. The depression preferably forms a channel, which is filled with non-solid material to at least 50% by volume, more preferably at least 80% by volume, even more preferably at least 90% by volume, particularly preferably at least 95% by volume and very particularly preferably at least 99% by volume, in particular completely filled with non-solid material.

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

[0046] According to a preferred embodiment, the metal layer is produced by bonding a copper foil (preferably a foil made of high-purity copper) integrally to the ceramic body. According to a preferred embodiment, the bonding can be carried out via a DCB (direct copper bonding) method or via a brazing method. The brazing process can be, for example, an AMB (active metal brazing) method, 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% by weight) or a silver-containing brazing alloy (based on the solid content of the brazing alloy, the silver content is, for example, at least 50% by weight). In this case, in addition to the copper derived from the copper foil, the metal layer can also contain a metal from the bonding layer, in particular a metal from a welding layer (e.g., a brazing layer) or a diffusion layer.

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

[0048] The metal-ceramic substrate according to the present invention has a silver-containing contact area arranged on the metal layer. The contact area is preferably used to promote the bonding of the semiconductor to the metal layer. The semiconductor is preferably bonded to the metal layer by sintering, welding or bonding. Because it is not easy to attach the semiconductor to the metal of the metal layer of the metal-ceramic substrate, it is preferred that the metal layer is 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, related to the weight of the silver alloy. Preferably, contact areas are provided at all positions on the metal layer of the metal-ceramic substrate, where the metal-ceramic substrate is later filled with semiconductors. The contact area can be formed on the metal layer of the metal-ceramic substrate using different techniques. For example, the contact area may be provided by deposition. The deposition can be, for example, physical deposition or chemical deposition. For example, vapor deposition can be considered as physical deposition. Preferred methods for vapor deposition are in particular electron beam deposition, laser beam deposition, arc discharge deposition or cathode sputtering. In chemical deposition, the contact area is preferably created by applying a composition containing silver or a silver precursor to the metal layer. For example, the silver-containing composition can be fired to create a sintered bond between the silver contained in the composition and the metal of the metal layer. For example, the composition containing the silver precursor can be treated to release the silver and adsorb the silver to the metal layer. Such treatment can be accomplished, for example, by contacting the silver precursor with the metal layer. Methods for depositing silver or silver compounds to create contact areas on the metal layer of the metal-ceramic substrate are known to those skilled in the art.

[0049] In a cross section through the metal-ceramic substrate perpendicular to the main extension plane, the structured region of the metal-ceramic substrate has a geometry that meets the following requirements:

[0050] A(BCD 固体 ) / A(BCD 总 )>70%,

[0051] in

[0052] A(BCD 总 ) is the total area of ​​the triangle described by points B, C, and D, and

[0053] A(BCD 固体 ) is the area of ​​the triangle described by points B, C, and D that is occupied by the solid material,

[0054] According to a preferred embodiment, the structured region of the metal-ceramic substrate has a geometry in a cross section through the metal-ceramic substrate perpendicular to the main extension plane, 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%.

[0055] According to another preferred embodiment, the structured region of the metal-ceramic substrate has a geometry in a cross section through the metal-ceramic substrate perpendicular to the main extension plane, wherein 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%.

[0056] In order to determine the triangle described by points B, C and D, a cross section of the structured region of the metal-ceramic substrate is observed. The cross section extends perpendicularly to the main extension plane of the ceramic body. Preferably, the cross section can be observed by cutting the metal-ceramic substrate perpendicularly to the main extension plane of the ceramic body and taking a picture of the cross section thus obtained using a scanning electron microscope.

[0057] Points B, C, and D of the triangle can be determined in the cross section as follows. For the purpose of illustration, reference is made by way of example. Figure 1 and Figure 2 .

[0058] Figure 1 A schematic diagram of a general metal-ceramic substrate is shown.

[0059] Figure 2 A portion of a cross section through a metal-ceramic substrate according to the invention is shown.

[0060] Figure 1The metal-ceramic substrate 1 shown in FIG. 1 comprises a ceramic body 10. A main extension plane 2 of the ceramic body 10 is indicated by reference numeral 2 (as a line). The ceramic body 10 comprises a main boundary surface 15. The metal-ceramic substrate 1 comprises a metal layer 20 which is extensively bonded to the main boundary surface 15 of the ceramic body 10. Figure 1 In an embodiment of the present invention, the metal-ceramic substrate 1 further comprises a further metal layer 200, which is extensively bonded to the ceramic body 10. On the metal layer 20 there is a contact region 8 containing silver. The metal layer 20 comprises a structured portion. 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 comprises the metal layer 20 and the recess 22. Therefore, the structured region 4 partially comprises a solid material 50 and a non-solid material (e.g. 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 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 metal layer 20 has a main metal surface 24 parallel to the main boundary surface 15 of the ceramic on the upper side facing away from the main boundary surface 15 of the ceramic. This main metal surface 24 comprises 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 15 of the ceramic to the main metal surface 24 in a direction perpendicular to the main boundary surface 15 of the ceramic and preferably forms a channel which is completely or mainly filled with a non-solid material.

[0061] exist Figure 2 In the portion of the cross section shown through the metal-ceramic substrate according to the invention, a portion of the structured region can be seen. The region of the ceramic body 10 that is extensively bonded to the region of the metal layer 20 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.

[0062] The determination of points B and C of the line BC in the cross section is preferably performed in a number of steps:

[0063] In a first step, a best fit line 30 is determined between the ceramic body 10 and the metal layer 20. For this purpose, the area of ​​the ceramic body 10 and the area of ​​the metal layer 20 are visually determined and the best fit line 30 is defined as the boundary between the ceramic body 10 and the metal layer 20 that can be observed in cross section.

[0064] In a second step, a 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 determined visually; this is often the material of the metal layer 20. The non-solid material is also determined visually. The non-solid material is often a gaseous material that is used to fill the structured portion as the recess 22 in the metal layer 20.

[0065] In a third step, a point A is determined on the perpendicular line to the best fit line 30 at a distance of 150 μm from the best fit line 30 , at which point A the perpendicular line to the best fit line 30 intersects the contour line 40 .

[0066] In the fourth step, a point B is determined on the perpendicular line to the best-fit line 30 at a distance of 80 μm from the best-fit line 30 , at which the perpendicular line to the best-fit line 30 intersects the contour line 40 .

[0067] In the fifth step, on the straight line passing through point A and point B, a point C is determined at which the straight line intersects the best fit line 30 .

[0068] In the sixth step, a point D is determined on the perpendicular line to the best fit line 30 passing through point B, at which the perpendicular line intersects the best fit line 30 .

[0069] The cutting of the metal-ceramic substrate perpendicularly to the main extension plane of the ceramic body and the recording of the cross-section thus obtained by optical microscopy (incident light / bright field) are preferably carried out as follows:

[0070] In a first step, a 100 mm thick plate having a diameter of 100 mm is first cut out from the metal-ceramic substrate to be inspected by sawing perpendicularly to the plane spanned by the main metal surface of the metal layer of the metal-ceramic substrate using a diamond saw blade at a low rotation speed and using a lubricant (Exakt). 2 Up to 400mm 2 A cubic sample blank with a rectangular base in the range of . The sample blank thus has a sample surface, which is supplied for investigation. Therefore, before sawing, this sample surface extends perpendicularly to the plane spanned by the main metal surface of the metal layer of the metal-ceramic substrate. Therefore, it has parts on the ceramic body and the metal layer (including the optional bonding layer). The sample blank is first embedded in a mold with a low shrinkage epoxy resin (Caldo-Fix, Struers), wherein the sample surface is oriented perpendicular to the mold wall. The epoxy resin is then cured at 75° C. in a drying cabinet. 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.

[0071] In a second step, an optical microscope (Leica, DM6000M, incident light / bright field) was used to identify structured areas in the metal layer in the analysis area at a magnification of 200x, which contained partly solid material and partly non-solid material. Solid material and non-solid material can be clearly distinguished in the structured area due to different colors.

[0072] Area A(BCD固体 ) and A(BCD 总 ) is preferably determined in a conventional manner, for example using image evaluation software (eg IMS Client, Imagic Corporation).

[0073] Preferably, the term "in a cross section" as used herein refers to a (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 run parallel to one another and are uniformly spaced apart from one another. Thus, in order to determine the ratio A(BCD) of the metal-ceramic substrate to be observed 固体 ) / A(BCD 总 ), preferably using the following procedure:

[0074] 1. Examining at least ten, particularly preferably ten different cross sections of the structured region;

[0075] 2. Determine the ratio A(BCD) for each of these cross sections. 固体 ) / A(BCD 总 );as well as

[0076] 3. The ratio A(BCD) of each of these cross sections 固体 ) / A(BCD 总 ) are averaged to obtain the ratio A(BCD) of the metal-ceramic substrate under observation. 固体 ) / A(BCD 总 ).

[0077] According to a preferred embodiment, the ratio A(BCD) is 100% in at least ten different cross-sections of at least one structured region of the metal layer, more preferably in no more than 20 different cross-sections of at least one structured region of the metal layer, and most preferably in ten different cross-sections of at least one structured region of the metal layer. 固体 ) / A(BCD 总 ) is not more than 10%, more preferably not more than 7%, particularly preferably not more than 5%, and very particularly preferably not more than 2%. The sample standard deviation SSD is determined using the following formula:

[0078]

[0079] in:

[0080] n = ratio A(BCD- 固体 ) / A(BCD- 总 ),

[0081] X i =Ratio A(BCD-固体 ) / A(BCD- 总 ), and

[0082] The average of the individual values ​​of .

[0083] Surprisingly, it was found that the metal-ceramic substrates according to the invention with this geometry have an increased 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 the proportion of solid material in the metal layer at the boundary with the surface of the ceramic body was significantly lower in metal-ceramic substrates from the prior art, provided that the metal-ceramic substrates had silver-containing contact regions arranged on the metal layer.

[0084] Not bound by explanation, this may be due to the fact that in the prior art, often first the produced metal-ceramic substrate is structured, and then silver-plated on the surface to create contact areas. Silver-plating is often carried out by immersing the structured metal-ceramic substrate in a bath containing a solution containing silver ions. Metal ions are electrochemically dissolved from the metal layer of the metal-ceramic substrate and replaced by silver ions. Within the scope of the present invention, it is observed that in this process, silver ions are mainly deposited on the surface of the metal-ceramic substrate, but the metal ions of the metal layer are mainly dissolved in the region near the ceramic body (this effect cannot be prevented by masking the structured portion, because due to the edge side structured portion in the metal layer, the masking is washed away by the solution containing silver ions). When the metal layer in the region adjacent to the ceramic body has been structured and therefore no longer homogeneous, this effect is particularly significant. This causes solid material (particularly the metal of the metal foil) to be removed from the metal foil in the region close to the ceramic body, and thus produces a weakness that makes the metal layer fall off from the ceramic body, which has an adverse effect on thermal shock resistance. However, according to the invention, a structured region is created which has a sufficient amount of solid material in the region close to the ceramic body, whereby detachment of the metal layer from the ceramic body can be prevented and an improvement in the thermal shock resistance can be achieved.

[0085] According to a preferred embodiment, the metal-ceramic substrate comprises an additional (second) metal layer which is extensively bonded to the ceramic body. The additional metal layer is preferably extensively bonded to a boundary surface facing away from the main boundary surface of the ceramic (and preferably extending parallel to the main boundary surface). The additional (second) metal layer may have the same properties as the (first) metal layer, or may differ from the (first) metal layer in its properties. For the properties of the additional (second) metal layer, reference is made to the above explanations.

[0086] The metal-ceramic substrate according to the invention can be used in particular in electronic applications, especially in the field of power electronics.

[0087] Therefore, the present invention also provides an electronic component having the above-mentioned metal-ceramic substrate.

[0088] According to a preferred embodiment, such an electronic module comprises a base plate. The base plate is preferably widely bonded to the metal layer of the metal-ceramic substrate. Alternatively, the metal layer of the metal-ceramic substrate can be designed as a heat sink. According to another preferred embodiment, the electronic component comprises at least one chip. The at least one chip is preferably widely bonded to a silver-containing contact area arranged on the metal layer. According to another preferred embodiment, the electronic component comprises: a metal-ceramic substrate, the metal-ceramic substrate comprising a first metal layer and a second metal layer (wherein the first metal layer is preferably opposite to the second metal layer); a base plate; and at least one chip, wherein the at least one chip is bonded to the first metal layer of the metal-ceramic substrate via a silver-containing contact area arranged on the metal layer, and the base plate is bonded to the second metal layer of the metal-ceramic substrate.

[0089] The metal-ceramic substrate according to the present invention can be obtained by different manufacturing processes.

[0090] According to a preferred embodiment, the method is a method for producing a metal-ceramic substrate provided with a structuring and a contact region containing silver, the method comprising the following steps:

[0091] a) providing a metal-ceramic substrate, the metal-ceramic substrate comprising:

[0092] a1) a ceramic body, and

[0093] a2) a metal layer, which is extensively bonded to the ceramic body,

[0094] b) applying a first mask to the metal layer,

[0095] c) depositing a silver-containing layer on unmasked areas of the metal layer to obtain contact areas comprising silver,

[0096] d) removing the first mask,

[0097] e) applying a second mask to the metal layer,

[0098] f) etching unmasked areas of the metal layer while maintaining the pattern, and

[0099] g) removing the second mask.

[0100] Therefore, in this method, preferably a metal-ceramic substrate is first provided. This metal-ceramic substrate has a ceramic body and a metal layer, which is widely bonded to the ceramic body. The metal-ceramic substrate can be a standard metal-ceramic substrate. The ceramic body and the metal layer can have the composition as described above for the metal-ceramic substrate. The metal layer can preferably be integrally bonded to the ceramic body, also as described above for the metal-ceramic substrate.

[0101] In this method, a first mask is preferably applied to the metal layer. The first mask is used to protect the masked area of ​​the metal layer from the deposition of the silver-containing layer in the subsequent steps. This ensures that the silver-containing layer is only deposited on the unmasked area of ​​the metal layer of the metal-ceramic substrate. Therefore, the mask is designed in such a way that no silver-containing layer is deposited on the masked area of ​​the metal layer of the metal-ceramic substrate. The type of mask is not further restricted. The mask can be, for example, a standard negative mask or a positive mask. The mask can be created, for example, by a foil (or dry film) or a liquid, which is optionally printed or sprayed on the surface of the metal-ceramic substrate in certain areas. For example, a standard resist can be used. These resists preferably contain a curable polymer (e.g., a photocurable polymer). According to a possible embodiment, a photosensitive film is applied to the metal layer of the metal-ceramic substrate, and then exposed to the area to be masked in order to obtain a first mask. The unexposed areas of the photosensitive film can then be removed in a conventional manner (e.g., using a sodium carbonate solution).

[0102] After applying the first mask, a silver-containing layer is preferably deposited on the unmasked areas of the metal layer to obtain contact areas containing silver. The silver-containing layer is preferably composed of silver or a silver alloy, particularly preferably a layer composed of silver. The silver-containing layer is preferably deposited in a conventional manner. The silver-containing layer can be deposited, for example, electrochemically, electrolessly or chemically. Preferably, chemical deposition is carried out in the following manner: a silver-containing solution is applied, wherein a charge exchange occurs between the metals, wherein the metal of the metal layer is partially dissolved and the 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 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.

[0103] Preferably, after depositing the silver-containing layer on the unmasked areas of the metal layer to obtain the contact areas containing silver, the first mask is removed. The first mask can be removed in a standard manner. For this purpose, the metal-ceramic substrate can be treated with an alkaline solution (e.g. 2.5% sodium hydroxide solution) to remove the first mask.

[0104] After removing the first mask, the second mask is preferably applied to the metal layer. The second mask is used to protect the masked area of ​​the metal layer of the metal-ceramic substrate from etching in subsequent steps. This ensures that only those unmasked and intended areas of the metal layer of the metal-ceramic substrate can be etched. Therefore, the mask is created in such a way that the masked area of ​​the metal layer does not etch. According to a preferred embodiment, the second mask is applied to the area of ​​the metal-ceramic substrate to which the first mask has not yet been applied. The type of mask is not further restricted. The mask can be, for example, a standard negative mask or a positive mask. The mask can be created, for example, by a foil (or dry film) or a liquid, which is optionally printed or sprayed onto the surface of the metal-ceramic substrate in certain areas. For example, a standard resist can be used. These resists preferably contain a curable polymer (e.g., a photocurable polymer). According to a possible embodiment, a photosensitive film is applied to the partially silvered surface of the metal-ceramic substrate, and then exposed to the area to be masked in order to obtain a second mask. The unexposed areas of the photosensitive film can then be removed in a conventional manner (e.g., using a sodium carbonate solution).

[0105] After the second mask has been applied to the metal layer, the unmasked areas of the metal layer are preferably etched to obtain the structured portion. Etching is preferably carried out in a standard professional manner. Therefore, etching is preferably carried out using a standard etching solution. According to a preferred embodiment, the etching solution is selected from the group consisting of FeCl3 etching solution and CuCl2 etching solution. If necessary, additional etching solutions can be used, for example to structure the unmasked areas of the bonding layer optionally included. According to a preferred embodiment, the additional etching solution can be selected from the group consisting of an etching solution containing hydrogen peroxide and an etching solution containing ammonium peroxydisulfate. For example, the additional etching solution can be an etching solution containing ammonium fluoride and fluoroboric acid (e.g. HBF4) and hydrogen peroxide and / or ammonium peroxydisulfate.

[0106] Preferably, after etching the unmasked areas of the metal layer while maintaining the structuring, the second mask is removed. The second mask can be removed in a standard manner. For this purpose, the metal-ceramic substrate can be treated with an alkaline solution (eg 2.5% sodium hydroxide solution) to remove the second mask.

[0107] The method described herein makes it possible to obtain a metal-ceramic substrate provided with structures and contact areas containing silver. By creating the silver-containing contact areas, the chip can be bonded to the metal-ceramic substrate more easily using common methods such as sintering or welding. The metal-ceramic substrate obtained in this way is characterized by a particularly high resistance to thermal shocks.

[0108] Exemplary embodiments

[0109] The invention is described in more detail below with the aid of exemplary embodiments, which, however, are not to be understood as restrictive. Example:

[0110] For the examples, a metal-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 on both sides to a copper layer with dimensions of 170 mm×132 mm×0.3 mm using the AMB (active metal brazing) method. This copper-ceramic substrate was first cleaned after production.

[0111] The photosensitive film was then applied to both copper layers of the copper-ceramic substrate using a hot roll laminator. The photosensitive film was exposed to 30 mJ / cm 2 , in order to cure the polymer contained in the photosensitive film and obtain a first mask. Subsequently, the unexposed areas of the photosensitive film are wet-chemically removed using a sodium carbonate solution (concentration = 10 g / l). After applying the first mask, the copper-ceramic substrate is cleaned by rinsing. Subsequently, the silver-containing contact areas are deposited on the unmasked areas of the copper layer of the copper-ceramic substrate. For this purpose, the copper-ceramic substrate provided with the first mask 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 areas, the copper-ceramic substrate is carefully rinsed with water to remove any residues. The first mask is then removed using a 2.5% sodium hydroxide solution in a stripping system.

[0112] Subsequently, a photosensitive film was applied to the two copper layers of the copper-ceramic substrate, each of which had a silver-containing contact area, using a hot roll laminator. The photosensitive film was exposed to 30 mJ / cm 2, so as to harden the polymer contained in the photosensitive film and obtain a second mask. Then use sodium carbonate solution (concentration = 10g / l) to wet-chemically remove the unexposed points of the photosensitive film. After applying the second mask, the copper-ceramic substrate is cleaned again by rinsing. Subsequently, the unmasked area of ​​the copper layer of the copper-ceramic substrate provided with the silver-containing contact area is etched in a wet-chemical manner. For this purpose, the copper-ceramic substrate is sprayed with a hydrochloric acid copper chloride solution (copper ion content = 160g / l) containing hydrogen peroxide in an etching system. Etching is performed at a temperature of 50°C and a spray pressure of 2.8 bar. By etching, material is removed from the unmasked area of ​​the copper layer of the copper-ceramic substrate. Then rinse the metal-ceramic substrate. Then, the unmasked area of ​​the bonding layer contained in the metal-ceramic substrate is also etched in a wet-chemical manner. For this purpose, the metal-ceramic substrate is sprayed with an etching solution containing ammonium fluoride, fluoroboric acid and hydrogen peroxide in an etching system again. Then rinse and dry the copper-ceramic substrate. The second mask was then removed using a 2.5% sodium hydroxide solution in a stripping system.

[0113] The resulting copper-ceramic substrate was laser cut into individual parts with dimensions (20.5 mm x 17.0 mm) and could then be used for further studies and production of electronic components.

[0114] Comparative Example:

[0115] A comparative example was prepared as in the example, the order of the steps being reversed: (i) depositing a silver-containing layer on unmasked areas of the copper layer to obtain contact areas containing silver, and (ii) etching unmasked areas of the copper layer to obtain the structuring.

[0116] For the comparative example, a metal-ceramic substrate similar to that in the embodiment was used, in which a ceramic body made of silicon nitride ceramic with a size of 177.8 mm×139 mm×0.32 mm was bonded on both sides with a copper layer with a size of 170 mm×132 mm×0.3 mm using the AMB (active metal brazing) process. This copper-ceramic substrate was first cleaned after production.

[0117] The photosensitive film was then applied to both copper layers of the copper-ceramic substrate using a hot roll laminator. The photosensitive film was exposed to 30 mJ / cm 2, so as to cure the polymer contained in the photosensitive film and obtain the first mask. Subsequently, the unexposed area of ​​the photosensitive film is removed by wet chemical method using sodium carbonate solution (concentration = 10g / l). After applying the first mask, the copper-ceramic substrate is cleaned by rinsing. Subsequently, the unmasked area of ​​the copper layer of the copper-ceramic substrate is etched by wet chemical method. For this purpose, the copper-ceramic substrate is sprayed with a hydrochloric acid copper chloride solution (copper ion content = 160g / l) containing hydrogen peroxide in an etching system. Etching is performed at a temperature of 50°C and a spray pressure of 2.8 bar. By etching, material is removed from the unmasked area of ​​the copper layer of the copper-ceramic substrate. Then rinse the metal-ceramic substrate. Then, the unmasked area of ​​the bonding layer contained in the metal-ceramic substrate is also etched by wet chemical method. For this purpose, the metal-ceramic substrate is sprayed with an etching solution containing ammonium fluoride, fluoroboric acid and hydrogen peroxide in the etching system again. Then rinse and dry the copper-ceramic substrate. Then remove the second mask using 2.5% sodium hydroxide solution in a stripping system.

[0118] A photosensitive film was then applied to both etched surfaces of the copper-ceramic substrate using a hot roll laminator. The photosensitive film was exposed to 30 mJ / cm 2 , in order to harden the polymer contained in the photosensitive film and obtain a second mask. The unexposed points of the photosensitive film are then wet-chemically removed using a sodium carbonate solution (concentration = 10 g / l). After applying the second mask, the copper-ceramic substrate is cleaned again by rinsing. Subsequently, the silver-containing contact areas are deposited on the unmasked areas of the copper layer of the copper-ceramic substrate. For this purpose, the copper-ceramic substrate provided with the second mask 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 areas, the copper-ceramic substrate is carefully rinsed with water to remove any residues. The second mask is then removed using a 2.5% sodium hydroxide solution in a stripping system.

[0119] The resulting copper-ceramic substrate was laser cut into individual parts with dimensions (20.5 mm x 17.0 mm) and could then be used for further studies and production of electronic components.

[0120] evaluate:

[0121] For the metal-ceramic substrates obtained in the examples and comparative examples, the ratio A (BCD 固体 ) / A(BCD 总). For this purpose, as described herein, the metal-ceramic substrate is cut perpendicularly to the main extension plane of the corresponding ceramic body, and an image of the cross section thus obtained is taken using an optical microscope. Points A, B, C and D are determined in the cross section. Then, the ratio A (BCD) of each of the metal-ceramic substrates is determined. 固体 ) / A(BCD 总 For this purpose, ten different cross sections of the structured region in the metal layer of the relevant metal-ceramic substrate are studied and the ratio A (BCD) is determined for each of these cross sections. 固体 ) / A(BCD 总 ), and calculate the ratio A(BCD) of each of these cross sections 固体 ) / A(BCD 总 ) to achieve the corresponding metal-ceramic substrate ratio A(BCD 固体 ) / A(BCD 总 ). In addition, the standard deviation SSD is determined.

[0122] Figure 3 shows an example of an optical microscope image of a cross section of a structured region of a metal-ceramic substrate according to an embodiment, and Figure 4 An example of an optical microscope image of a cross section of a structured region of a metal-ceramic substrate according to a comparative example is shown.

[0123] The results are shown in Table 1.

[0124] Table 1:

[0125] <![CDATA[A(BCD 固体 ) / A(BCD 总 )]]> Standard Deviation SSD Example 97.2％ 0.4％ Comparative Example 67.3％ 11.7％

[0126] Testing the Thermal Shock Resistance of Metal-Ceramic Substrates For this purpose, a thermal shock resistance test was performed.

[0127] Thermal shock resistance test:

[0128] In preparation for the thermal shock resistance test, ultrasonic microscopy (PVA Tepla SAM300) is first used to check whether the metal-ceramic substrate is in perfect condition. For this test, only such metal-ceramic substrates are used, which do not show delamination between the ceramic body and the metal layer or other deformations (e.g., cracks) that may cause the metal layer to be delaminated from the ceramic body. In order to test the thermal shock resistance, the metal-ceramic substrate is repeatedly exposed to cold liquid (temperature -65 ° C, Galden Do2TS) and hot liquid (temperature +150 ° C, Galden Do2TS) in a cycle chamber (ESPEC TSB-21 51) for a period of five minutes each. The delamination and other deformations of the metal-ceramic substrate are checked again by means of ultrasonic microscopy (PVA Tepla SAM300) every 1000 cycles. The test is terminated after 3000 cycles. The delamination and other deformations of the metal-ceramic substrate are then checked again by means of ultrasonic microscopy (PVA Tepla SAM300). The state of the respective metal-ceramic substrates after the thermal shock test was compared with the state of each metal-ceramic substrate before the thermal shock test in terms of delamination and other deformations. Delamination and other deformations (eg, cracks) are visible as white discoloration in ultrasound images.

[0129] The results are shown in Table 2.

[0130] Table 2:

[0131] Results of thermal shock resistance tests Example Very good: no visible delamination Comparative Example Poor: Significant delamination is visible at the corners of the metal-ceramic substrate

[0132] The results show that the metal-ceramic substrate according to the present invention is significantly superior to the metal-ceramic substrate of the comparative example in terms of thermal shock resistance.

[0133] List of reference numerals:

[0134] 1 Metal-ceramic substrate

[0135] 2 Main extension plane

[0136] 4 Structured Area

[0137] 8 Contact area

[0138] 10 Ceramic body

[0139] 15 Main boundary surface

[0140] 20 Metal Layer

[0141] 22 Depression

[0142] 24 Metal main surface

[0143] 40 Contour lines

[0144] 50 solid materials

[0145] 200 Additional Metal Layers

Claims

1. A metal-ceramic substrate, comprising: a) a ceramic body comprising a main extension plane, b) a metal layer, said metal layer being extensively bonded to said ceramic body, said metal layer comprising a structured region, said structured region comprising (i) some solid material, and (ii) Some non-solid materials as well as c) a silver-containing contact region arranged on the metal layer, It is characterized in that In a cross section through the metal-ceramic substrate perpendicular to the main extension plane, the structured region has a geometry that meets the following requirements: A(BCD 固体 ) / A(BCD 总 )>70%, in 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, said area being occupied by the solid material, Points B, C, and D are determined as follows:

1. Determine a best fit line between the ceramic body and the metal layer; 2. determining a contour line separating 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 a point A at which the perpendicular line of the best fit line intersects the contour line; 4. Determine a point B on the perpendicular line of the best fit line at a distance of 80 μm from the best fit line, at which point 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; 6. On the perpendicular line to the best fit line passing through point B, determine point D where the perpendicular line intersects the best fit 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 ceramics, silicon nitride ceramics, and aluminum oxide ceramics.

3. The metal-ceramic substrate according to claim 1 or 2, characterized in that: The metal layer includes 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 Meet the following requirements: 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 of at least ten different cross sections of the structured region of the metal layer A(BCD 固体 ) / A(BCD 总 )’s sample standard deviation SSD is no greater than 10%.

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

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