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 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 portion of a solid material and (ii) a portion of a non-solid material; and c) a contact region arranged on the metal layer and comprising silver, the structured region having a geometry in a cross-section penetrating the metal-ceramic substrate perpendicular to the main extension plane, satisfying the following requirements: 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 solids) represents the length of the line between point B and point C intersecting the solid material.

Description

[0001] The present invention relates to a metal-ceramic substrate, an electronic component comprising the metal-ceramic substrate and a method for producing the metal-ceramic substrate.

[0002] Metal-ceramic substrates play an important role in the field of power electronics. They are key elements when building electronic components and ensure that large amounts of heat are quickly dissipated during 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 a metal layer to a ceramic layer are known from the prior art. In the so-called DCB ("direct copper bonding") method, a copper compound (usually copper oxide) having a melting point lower than that of copper is provided on the surface of a copper foil by reacting copper with a reactive gas (usually oxygen). When the copper foil treated in this way is applied to a ceramic body and the composite material is heated, the copper compound melts and wets the surface of the ceramic body, so that a stable adhesive bond is created 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, using a special solder containing a metal (usually silver) with a melting point of at least 700°C and an active metal. The role of the active metal is to react with the ceramic material and thus promote the bonding of the ceramic material to the remaining solder, thereby forming a reaction layer, and a 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 bond a copper foil to a ceramic body using a solder containing 50% to 89% by weight of silver and copper, bismuth and an active metal. In this way, it is possible to reliably attach the copper foil to the ceramic body. Alternatively, a silver-free solder can be used to connect the metal foil to the ceramic body. These solders are based, for example, on high melting point metals (particularly 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] In the construction of electronic components, metal-ceramic substrates are usually equipped with chips. In order to equip the metal-ceramic substrate with a chip, it is usually 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 connected to the metal-ceramic substrate using common processes such as sintering or welding. In order to create the contact area, the metal-ceramic substrate is usually first treated with an etching solution in some areas to form the desired structured portion. The contact area is then provided by applying a silver-containing coating to some areas of the surface of the structured metal-ceramic substrate.

[0006] Metal-ceramic substrates produced in this way are often exposed to large temperature changes during operation as parts of electronic components. Although the temperature during interruptions in operation may be, for example, -20°C or lower, depending on the environment, 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 performance losses. Therefore, high thermal shock resistance is a key criterion for the suitability of metal-ceramic substrates in electronics, especially 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, which comprises:

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

[0011] b) a metal layer, which is connected to the ceramic body in a planar manner, the metal layer comprising a structured region, the structured region comprising:

[0012] (i) some solid material, and

[0013] (ii) some non-solid materials,

[0014] as well as

[0015] c) a contact region, which contains silver and is 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] S(BC 固体 ) / S(BC 总 )>60%

[0019] in:

[0020] S(BC 总 ) represents the total length of the line between points B and C, and

[0021] S(BC 固体 ) represents the length of the line between points B and C that intersects the solid material,

[0022] Points B and C 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 separating the solid material from the non-solid material;

[0025] 3. Determine a point A on the perpendicular line of the best fit line at a distance of 150 μm from the best fit line, at which point the perpendicular line of the best fit line intersects the contour line;

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

[0027] 5. Determine point C on the straight line passing through points A and B where the straight line intersects the best fit line.

[0028] Furthermore, the present invention relates to an electronic component comprising such a metal-ceramic substrate and a chip.

[0029] Furthermore, the invention relates to a method for producing a metal-ceramic substrate.

[0030] The metal-ceramic substrate according to the invention comprises a ceramic body having a main extension plane.

[0031] 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 includes boundary surfaces-in the case of a cube, six boundary surfaces. In this document, the main boundary surface preferably refers to the boundary surface with the largest surface area connected to the metal layer in a planar manner. 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.

[0032] 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.

[0033] 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, particularly preferably in the range of 0.15 mm to 3 mm.

[0034] The metal-ceramic substrate according to the invention comprises a metal layer which is connected in a planar manner to the ceramic body, the metal layer comprising a structured region which contains (i) partly solid material and (ii) partly non-solid material.

[0035] The metal layer is preferably connected to the ceramic body by material bonding. According to a preferred embodiment, the metal layer is connected 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 brazing process. The brazing 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 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 weight %) is used. Therefore, the metal layer can also include a connecting layer in contact with the ceramic body. The connecting layer can be, for example, a welding layer (particularly a brazing layer) or a diffusion layer.

[0036] The metal layer is connected to the ceramic body in a planar manner. Accordingly, the metal layer is preferably connected to the main boundary surface of the ceramic body in a planar manner. 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. In addition, the metal layer is preferably structured. The structured portion is preferably understood to mean a recessed portion in the metal layer, which separates the various parts of the metal layer from each other and thereby electrically insulates these parts. Such a structured portion is often created by etching technology.

[0037] Accordingly, the metal layer comprises a structured region. The structured region is a part of the metal layer that contains a structured portion. The structured portion is preferably a recess in the metal layer.

[0038] The metal layer further comprises 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 thus contains the metal of the metal layer, which is interrupted by the depression in the structured region.

[0039] The structured region has regions comprising solid material and regions comprising non-solid material.

[0040] The region comprising solid material preferably contains at least one member of the group consisting of: (i) a metal of the metal layer (optionally including a connecting layer, if present, for example in the case of an AMB); (ii) a metal of the contact region (particularly silver); and (iii) a material of the ceramic body. For this reason, the solid material preferably contains (i) a metal of the metal layer (optionally including a connecting layer); and optionally (ii) a metal of the contact region (particularly silver); and / or (iii) a material of the ceramic body.

[0041] 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 have a deposition 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 include a layer consisting 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.

[0042] The region containing the non-solid material preferably contains a gaseous material. For this reason, 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. Most preferably, the gaseous material is air.

[0043] According to a preferred embodiment, the recess 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 recess 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 most preferably at least 99% by volume, in particular completely filled with the non-solid material.

[0044] The metal layer preferably comprises at least one metal selected from the group consisting of copper, aluminum and molybdenum. According to another particularly preferred embodiment, the metal layer comprises at least one metal selected from the group consisting of copper and molybdenum. According to a particularly preferred embodiment, the metal layer comprises copper. According to another very 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, based on the total weight of the metal layer (preferably including any connecting layer that may be present).

[0045] According to a preferred embodiment, the metal layer is produced by connecting 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 soldering process. The soldering process can be, for example, an AMB (active metal brazing) process, wherein preferably a silver-free soldering alloy (based on the solid content of the soldering alloy, the silver content is, for example, less than 1.0% by weight) or a silver-containing soldering alloy (based on the solid content of the soldering 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 the metal of the connecting layer, in particular the metal of the welding layer (e.g. soldering layer) or the diffusion layer.

[0046] The thickness of the metal layer is preferably 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.

[0047] The metal-ceramic substrate according to the present invention comprises a contact region, which contains silver and is arranged on the metal layer. The contact region is preferably used to promote the connection of the semiconductor to the metal layer. The semiconductor is preferably connected 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, the metal layer is preferably provided with a contact region. The contact region is preferably made of silver or a silver-containing alloy. In the case of a silver-containing alloy, the silver-containing alloy contains at least 50% by weight of silver based on the weight of the silver alloy. Preferably, contact regions are provided at all positions on the metal layer of the metal-ceramic substrate, where the metal-ceramic substrate is to be filled with semiconductors later. The contact region can be formed on the metal layer of the metal-ceramic substrate by means of different techniques. For example, the contact region may be provided by deposition. The deposition may be physical deposition or chemical deposition. For example, vapor deposition can be considered as a physical deposition method. Preferred methods for vapor deposition are particularly electron beam deposition, laser beam deposition, arc discharge deposition or cathode sputtering. In the case of chemical deposition, the contact region 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 allow the silver to be adsorbed into the metal layer. Such treatment can be carried out, for example, by contacting the silver precursor with the metal layer. Methods for depositing silver or silver compounds to produce contact areas on the metal layer of the metal-ceramic substrate are known to those skilled in the art.

[0048] The structured region of the metal layer has a geometry in a cross section through the metal-ceramic substrate perpendicular to the main extension plane, wherein the following requirements are met:

[0049] S(BC 固体 ) / S(BC 总 )>60%

[0050] in:

[0051] S(BC Total) represents the total length of the line between point B and point C, and

[0052] S(BC 固体 ) represents the length of the line between points B and C that intersects the solid material.

[0053] According to a preferred embodiment, the structured region of the metal layer has a geometry in a cross section through the metal-ceramic substrate perpendicular to the main extension plane, wherein the ratio S(BC 固体 ) / S(BC 总 )>70%, more preferably>80%, even more preferably>85%, particularly preferably>90% and most preferably>95%.

[0054] According to another preferred embodiment, the structured region of the metal layer has a geometry in a cross section through the metal-ceramic substrate perpendicular to the main extension plane, wherein 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 most preferably in the range of 80% to 99%.

[0055] In order to determine point B and point C, a cross section of the structured region of the metal layer 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 capturing an image of the cross section thus obtained by an optical microscope.

[0056] Point B and point C of line BC may be determined in the cross section as follows.

[0057] For illustrative purposes, refer to Figure 1 and Figure 2 As an example.

[0058] Figure 1 A metal-ceramic substrate of this type is shown schematically.

[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 comprises a ceramic body 10. A main extension plane 2 of the ceramic body 10 is indicated with reference symbol 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 connected in a planar manner 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 another metal layer 200, which is connected to the ceramic body 10 in a planar manner. There is a contact area 8 containing silver on the metal layer 20. The metal layer 20 has a structured portion. This is formed by a recessed portion 22 in the metal layer 20. The recessed portion 22 contains a non-solid material. The structured region 4 includes the metal layer 20 and the recessed portion 22 in some areas. Therefore, the structured region 4 includes a part of solid material 50 and a part of non-solid material (e.g., gas phase material), the part of solid material is formed by the metal of the metal layer 20, and the part of non-solid material fills the recessed portion 22. The gas phase material is often ambient air. The solid material 50 is separated from the non-solid material of the recessed portion 22 by a contour line 40. The metal layer 20 includes 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 contains the metal of the metal layer 20, and the metal layer is interrupted by the recessed portion 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 section of the cross section through the metal-ceramic substrate according to the invention shown, a part of the structured region can be seen. The region of the ceramic body 10 that is connected in a planar manner 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 optically determined and the best fit line 30 is defined as the boundary between the ceramic body 10 and the metal layer 20 that can be observed in cross section.

[0064] In a second step, a contour line 40 is determined, which separates the solid material 50 from the non-solid material of the depression 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 gas phase material, which is used to fill the structured portion—as the depression 22 in the metal layer 20.

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

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

[0068] The section through the metal-ceramic substrate perpendicular to the main extension plane of the ceramic body and the capture of the cross section obtained therefrom by means of an optical microscope (incident light / bright field) is preferably carried out as follows:

[0069] In a first step, a 100 mm diameter section is first cut out of the metal-ceramic substrate to be inspected by sawing perpendicularly to the plane formed 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 Company). 2 Up to 400mm 2 Cubic sample blanks with a rectangular base in the range of . The sample blanks accordingly include a sample surface, which is supplied for investigation. Therefore, before sawing, this sample surface extends perpendicular to the plane formed by the main metal surface of the metal layer of the metal-ceramic substrate. Therefore, it has parts on the ceramic body and on the metal layer (including the optional connecting layer). The sample blank is first embedded in a casting 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 oven. 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.

[0070] In the second step, an optical microscope (Leica, DM6000M, incident light / bright field) was used to identify the structured area 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 their different colors.

[0071] The length of the line S(BC 总 ) and S(BC 固体) is preferably determined in a standard manner, for example using image analysis software (eg IMSClient, Imagic Corporation).

[0072] Preferably, the term "in a cross section" as used herein refers to a (preferably representative) total cross section, more preferably at least ten cross sections, most preferably not more than 20 cross sections, and in particular ten cross sections. These cross sections preferably extend parallel to each other and are evenly spaced apart from each other. In order to determine the ratio S(BC) of the metal-ceramic substrate under consideration 固体 ) / S(BC 总 ), preferably using the following procedure:

[0073] 1. Examining at least ten, particularly preferably ten different cross sections of the structured region;

[0074] 2. Determine for each of these cross sections the ratio S(BC 固体 ) / S(BC 总 );and

[0075] 3. The ratio S(BC) of each of these cross sections 固体 ) / S(BC 总 ) are averaged to obtain the ratio S(BC 固体 ) / S(BC 总 ).

[0076] According to a preferred embodiment, in at least ten different cross-sections of the structured region of the metal layer, more preferably in no more than 20 different cross-sections of the structured region of the metal layer, and most preferably in ten different cross-sections of the structured region of the metal layer, the ratio S(BC 固体 ) / S(BC 总 ) is not more than 10%, more preferably not more than 7%, particularly preferably not more than 5%, and most preferably not more than 3%. The sample standard deviation SSD is determined using the following formula:

[0077]

[0078] in:

[0079] n = ratio S(BC 固体 ) / S(BC 总 ),

[0080] X i = ratio S(BC 固体 ) / S(BC 总 ), and

[0081] The average of the individual values ​​of .

[0082] Surprisingly, it was found that the metal-ceramic substrate according to the invention with this geometry has 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, as long as they had silver-containing contact regions arranged on the metal layer.

[0083] Without being bound by explanation, this may be due to the fact that in the prior art, the metal-ceramic substrate produced is often first 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. The 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, the 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 area near the ceramic body (this effect cannot be prevented by masking the structured portion, because the structured portion is on the edge of the metal layer, so the masking is washed away by the solution containing silver ions). When the metal layer in the area adjacent to the ceramic body has been structured and is 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 area close to the ceramic body, and thus produces a weakness that causes the metal layer to 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.

[0084] According to a preferred embodiment, the metal-ceramic substrate comprises an additional (second) metal layer, which is connected to the ceramic body in a planar manner. The additional metal layer is preferably connected to the boundary surface of the main boundary surface (and preferably extends parallel to the main boundary surface) away from the ceramic in a planar manner. The additional (second) metal layer can have the same properties as the (first) metal layer, or can be different from the (first) metal layer in its properties. For the properties of the additional (second) metal layer, refer to the above explanation.

[0085] The metal-ceramic substrate according to the invention can be used in particular in electronic applications, especially in the field of power electronics.

[0086] Therefore, the present invention also provides an electronic component, which includes the above metal-ceramic substrate.

[0087] According to a preferred embodiment, such an electronic component comprises a substrate plate. The substrate plate is preferably bonded to the metal layer of the metal-ceramic substrate in a planar manner. 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 connected in a planar manner to a contact area containing silver 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 substrate plate; and at least one chip, wherein the at least one chip is connected to the first metal layer of the metal-ceramic substrate via a contact area containing silver arranged on the metal layer, and the substrate plate is connected to the second metal layer of the metal-ceramic substrate.

[0088] The metal-ceramic substrate according to the present invention can be obtained by different manufacturing processes.

[0089] 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:

[0090] a) providing a metal-ceramic substrate, the metal-ceramic substrate comprising:

[0091] a1) a ceramic body, and

[0092] a2) a metal layer, which is connected to the ceramic body in a planar manner,

[0093] b) applying a first mask to the metal layer,

[0094] c) depositing a silver-containing layer on unmasked areas of the structured metal layer, thereby producing contact areas containing silver,

[0095] d) removing the first mask,

[0096] e) applying a second mask to the metal layer,

[0097] f) etching unmasked areas of the metal layer to obtain a structured portion, and

[0098] g) removing the second mask.

[0099] Therefore, in this method, preferably a metal-ceramic substrate is first provided. This metal-ceramic substrate comprises a ceramic body and a metal layer connected to the ceramic body in a planar manner. 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 bonded to the ceramic body materially, also as described above for the metal-ceramic substrate.

[0100] 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 masking is designed in a certain way so that the silver-containing layer cannot be deposited on the masked area of ​​the metal layer of the metal-ceramic substrate. The type of masking is not further restricted. The masking can be, for example, a standard negative mask or a positive mask. The masking can be created, for example, by a film (or dry film) or a liquid, which is optionally printed or sprayed on the surface of the metal-ceramic substrate in some 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 the photosensitive film is exposed in the area to be masked to obtain a first mask. The unexposed area of ​​the photosensitive film can then be removed in a conventional manner (e.g., using a sodium carbonate solution).

[0101] After applying the first mask, the silver-containing layer is preferably deposited on the unmasked areas of the metal layer, thereby producing 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 charge exchange occurs between the metals, whereby the metal of the metal layer is partially dissolved, and at the same time 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 most preferably in the range of 0.8 g / l to 1.2 g / l.

[0102] 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.

[0103] After the first mask has been removed, the second mask is preferably applied to the metal layer. The second mask is used to protect the masked areas of the metal layer of the metal-ceramic substrate from etching in subsequent steps. This ensures that only those unmasked and structured areas of the metal layer of the metal-ceramic substrate can be etched. Therefore, the masking is designed in a certain way so that the masked areas of the metal layer are not etched. 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 masking is not further restricted. The masking can be, for example, a standard negative mask or a positive mask. The masking can be created, for example, by a film (or dry film) or a liquid, which is optionally printed or sprayed onto the surface of the metal-ceramic substrate in some 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 the photosensitive film is exposed in the area to be masked to obtain a second mask. The unexposed areas of the photosensitive film may then be removed in conventional manner (eg using a sodium carbonate solution).

[0104] 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 conventional manner. Therefore, it is preferably etched 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 connecting 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.

[0105] Preferably, the second mask is removed after the unmasked areas of the metal layer have been etched to produce the structured portion. 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) in order to remove the second mask.

[0106] The method presented herein makes it possible to obtain a metal-ceramic substrate provided with a structured portion and a contact area containing silver. By creating a silver-containing contact area, the chip can be connected 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 a particularly high resistance to thermal shocks.

[0107] Exemplary embodiments

[0108] The present invention is described in more detail below by means of illustrative embodiments, which, however, should not be understood as limiting. Example:

[0109] For this embodiment, a metal-ceramic substrate 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 connected on both sides to 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.

[0110] The photosensitive film was then applied to the two copper layers of the copper-ceramic substrate by means of a hot roll laminator. The photosensitive film was exposed to 30 mJ / cm in each of the areas to be masked. 2 , in order to harden the polymer contained in the photosensitive film and obtain a first mask. The unexposed areas of the photosensitive film are then chemically removed using a sodium carbonate solution (concentration = 10 g / l). After applying the first mask, the copper-ceramic substrate is cleaned by rinsing. After this, 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 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.

[0111] Next, a photosensitive film was applied to the two copper layers of the copper-ceramic substrate, each of which had a silver-containing contact area, by means of a hot roll laminator. The photosensitive film was exposed to 30 mJ / cm 2, so that the polymer contained in the photosensitive film is hardened and a second mask is obtained. Then the unexposed area of ​​the photosensitive film is chemically removed using a sodium carbonate solution (concentration = 10g / l). After applying the second mask, the copper-ceramic substrate is cleaned again by rinsing. Then the unmasked area of ​​the copper layer of the copper-ceramic substrate provided with the silver-containing contact area is chemically etched. For this purpose, the copper-ceramic substrate is sprayed with a hydrochloric acid-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 the metal-ceramic substrate is rinsed. Subsequently, the unmasked area of ​​the connecting layer contained in the metal-ceramic substrate is also chemically etched. 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 the copper-ceramic substrate is rinsed and dried. Then a 2.5% sodium hydroxide solution is used in a stripping system to remove the second mask.

[0112] The resulting copper-ceramic substrate was laser cut into individual parts with dimensions (20.5 mm x 17.0 mm), which could then be used for further research and production of electronic components.

[0113] Comparative Example :

[0114] The comparative example was prepared as in the example, but the order of the steps was 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.

[0115] 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 connected on both sides to a copper layer with a size of 170 mm×132 mm×0.3 mm via the AMB (active metal brazing) process. This copper-ceramic substrate was first cleaned after production.

[0116] The photosensitive film was then applied to the two copper layers of the copper-ceramic substrate by means of a hot roll laminator. The photosensitive film was exposed to 30 mJ / cm in each of the areas to be masked. 2, so that the polymer contained in the photosensitive film is hardened and the first mask is obtained. Then the unexposed area of ​​the photosensitive film is chemically removed using a sodium carbonate solution (concentration = 10g / l). After applying the first mask, the copper-ceramic substrate is cleaned by rinsing. Next, the unmasked area of ​​the copper layer of the copper-ceramic substrate is chemically etched. For this purpose, the copper-ceramic substrate is sprayed with a hydrochloric acid-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 the metal-ceramic substrate is rinsed. Subsequently, the unmasked area of ​​the connecting layer contained in the metal-ceramic substrate is also chemically etched. 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 the copper-ceramic substrate is rinsed and dried. Then a 2.5% sodium hydroxide solution is used in a stripping system to remove the first mask.

[0117] 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 areas of the photosensitive film are then 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. After this, 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 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.

[0118] The resulting copper-ceramic substrate was laser cut into individual parts with dimensions (20.5 mm x 17.0 mm), which could then be used for further research and production of electronic components.

[0119] evaluate :

[0120] For the metal-ceramic substrates obtained in the examples and comparative examples, the ratio S(BC 固体 ) / S(BC 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. Point A, point B and point C are determined in the cross section. The ratio S(BC) of each of the metal-ceramic substrates is then determined. 固体 ) / S(BC 总 For this purpose, ten different cross sections of the structured region in the metal layer of the relevant metal-ceramic substrate are examined and the ratio S(BC 固体 ) / S(BC 总 ), and calculate the ratio S(BC) of each of these cross sections 固体 ) / S(BC 总 ) in order to achieve the ratio S(BC) of the relevant metal-ceramic substrate 固体 ) / S(BC 总 ). In addition, the standard deviation SSD is determined.

[0121] 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.

[0122] The results are shown in Table 1.

[0123] Table 1 :

[0124] <![CDATA[S(BC 固体 ) / S(BC 总 )]]> Standard Deviation SSD Example 99.3％ 0.4％ Comparative Example 58.4％ 12.7％

[0125] The thermal shock resistance of metal-ceramic substrates was investigated. For this purpose, a thermal shock resistance test was performed.

[0126] Thermal shock resistance test :

[0127] 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 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 circulation chamber (ESPEC TSB-21 51) for a period of five minutes in each case. 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.

[0128] The results are shown in Table 2.

[0129] Table 2 :

[0130] Results of thermal shock resistance tests Example Very good: no visible delamination. Comparative Example Poor: Delamination is visible at the corners of the metal-ceramic substrate.

[0131] 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.

[0132] List of reference numbers :

[0133] 1 Metal-ceramic substrate

[0134] 2 Main extension plane

[0135] 4 Structured Area

[0136] 8 Contact area

[0137] 10 Ceramic body

[0138] 15 Main boundary surface

[0139] 20 Metal Layer

[0140] 22 Depression

[0141] 24 Main metal surface

[0142] 40 Contour lines

[0143] 50 solid materials

[0144] 200 Additional metal layer

Claims

1. A metal-ceramic substrate, comprising: a) a ceramic body having a main extension plane, b) a metal layer, which is connected to the ceramic body in a planar manner, the metal layer comprising a structured region, the structured region comprising: (i) some solid material, and (ii) some non-solid materials, as well as c) A contact region, which contains silver and is arranged on the metal layer, 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: S(BC 固体 ) / S(BC 总 )>60% in: S(BC 总 ) represents the total length of the line between points B and C, and S(BC 固体 ) represents the length of the line between points B and C that intersects the solid material, where points B and C are determined as follows:

1. Determine a best fit line between the ceramic body and the metal layer; 2. Determine a contour line that separates the solid material from the non-solid material; 3. Determine a point A on the perpendicular line of the best fit line at a distance of 150 μm from the best fit line, at which point 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; as well as 5. Determine point C on the straight line passing through points A and B where the straight 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 gas phase material.

6. The metal-ceramic substrate according to any one of the preceding claims, characterized in that Meet the following requirements: 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 ratio of at least ten different cross sections of the structured region of the metal layer S(BC 固体 ) / S(BC 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.

9. A method for producing a metal-ceramic substrate provided with a structuring and a contact region containing silver, the method comprising the following steps: a) providing a metal-ceramic substrate, the metal-ceramic substrate comprising: a1) a ceramic body, and a2) a metal layer, which is connected to the ceramic body in a planar manner, b) applying a first mask to the metal layer, c) depositing a silver-containing layer on unmasked areas of the structured metal layer, thereby producing contact areas containing silver, d) removing the first mask, e) applying a second mask to the metal layer, f) etching unmasked areas of the metal layer to obtain a structured portion, and g) removing the second mask.

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