A metal-ceramic substrate having a contact area

Abstract

The present invention relates to a metal-ceramic substrate, an electronic component comprising the metal-ceramic substrate, and a method for manufacturing the metal-ceramic substrate. The metal-ceramic substrate comprises: a) a ceramic body having a main extension plane; b) a metal layer planar-connected to the ceramic body, the metal layer having a structured region that (i) partially contains a solid material and (ii) partially contains a non-solid material; and c) a contact region disposed on the metal layer and containing silver. The structured region has a geometric shape that satisfies the following requirements in a cross-section passing through the metal-ceramic substrate perpendicular to the main extension plane, that is, S(BC solid ) / S(BC total )>60%, where S(BC total ) represents the total length of the line between point B and point C, and S(BC solid ) represents the length of the line between point B and point C that intersects the solid material.

Description

Technical Field

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

[0002] Metal-ceramic substrates play an important role in the field of power electronics. They are important elements when constructing electronic components and ensure the rapid dissipation of a large amount of heat during the operation of such components. Metal-ceramic substrates typically consist of a ceramic layer and a metal layer joined to the ceramic layer.

[0003] Several methods for joining a metal layer to a ceramic layer are known from the prior art. In the so-called DCB (“direct copper bonding”) method, copper is reacted with a reactive gas (usually oxygen) to provide a copper compound (usually copper oxide) having a melting point lower than that of copper on the surface of a copper foil. The copper foil thus treated is attached to a ceramic body, and when the composite is heated, the copper compound melts, wets the surface of the ceramic body, and a stable agglomeration bond is created between the copper foil and the ceramic body. This method is described, for example, in U.S. Patent No. 3,744,120 (A) or German Patent No. 2,319,854 (C2).

[0004] In an alternative method, the metal foil can be joined to the ceramic body at a temperature of about 650 to 1000 °C, where 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 facilitate the joining of the remaining solder to the ceramic material, forming a reaction layer. On the other hand, the metal with a melting point of at least 700 °C serves to join the reaction layer to the metal foil. For example, Patent No. 4812985 (B2) proposes using a solder containing 50 to 89% by weight of silver, as well as copper, bismuth, and an active metal to join a copper foil to a ceramic body. In this way, it is possible to securely 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 metals (especially copper), low-melting metals (such as bismuth, indium, or tin), and active metals (such as titanium). Such a technique is proposed, for example, in German Patent Application Publication No. 102017114893 (A1). This technology basically results in a new class of independent compounds because the basis of the solder used is formed by another metal (copper instead of silver), leading to changes in material properties and compatibility with other solder components and modified joining conditions.

[0005] In the configuration of an electronic component, a chip is usually mounted on a metal-ceramic substrate. To mount a chip on a metal-ceramic substrate, it is usually necessary to provide a silver-containing contact area in the area of the metal-ceramic substrate where the chip is to be mounted. By providing a silver-containing contact area, the chip can be more easily connected to the metal-ceramic substrate using common processes such as sintering or soldering. To create the contact area, the metal-ceramic substrate is usually first treated with an etching solution in several areas to form the desired structured parts. Then, the contact area is provided by applying a silver-containing coating to some areas of the surface of the structured metal-ceramic substrate.

[0006] The metal-ceramic substrate thus manufactured is usually exposed to large temperature changes during operation as part of an electronic component. The temperature can, for example, drop to -20°C or lower during operation interruption depending on the environment, but the temperature of the metal-ceramic substrate can easily rise above 150°C during operation. The metal-ceramic substrate is regularly exposed to these temperature differences. Since the thermal expansion coefficients of the metal and the ceramic are different, repeated temperature changes may cause the metal layer to peel off (be stripped) from the ceramic body, resulting in performance degradation. Therefore, high thermal shock resistance is an important criterion for the compatibility of metal-ceramic substrates in electronics applications, especially in power electronics.

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

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

[0009] This object is achieved by the metal-ceramic substrate according to claim 1. Accordingly, the present invention provides a metal-ceramic substrate comprising a) a ceramic body having a main extension plane, b) a metal layer planar-connected to the ceramic body, (i) partially containing a solid material, (ii) a metal layer provided with a structured region that partially contains a non-solid material, c) a contact region containing silver and disposed on the metal layer, in the metal-ceramic substrate, In a cross-section passing through the metal-ceramic substrate perpendicular to the main extension plane, the structured region satisfies the following requirements, namely, S(BC solid ) / S(BC total )>60% and has a geometric shape that satisfies the formula, where S(BC total ) represents the total length of the line between point B and point C, S(BC solid) represents the length of the line between point B and point C that intersects the solid material, point B and point C are determined as follows, that is, 1. The best-fit line between the ceramic body and the metal layer is determined, 2. The contour line that separates the solid material from the non-solid material is determined, 3. Point A where the perpendicular to the best-fit line intersects the contour line is determined at a distance of 150 μm from the best-fit line on the perpendicular to the best-fit line, 4. Point B where the perpendicular to the best-fit line intersects the contour line is determined at a distance of 80 μm from the best-fit line on the perpendicular to the best-fit line, 5. A metal-ceramic substrate is provided, characterized in that point C where the straight line passing through point A and point B intersects the best-fit line is determined.

[0010] Furthermore, the present invention relates to an electronic component comprising such a metal-ceramic substrate and a chip.

[0011] In addition, the present invention relates to a method for manufacturing a metal-ceramic substrate.

[0012] The metal-ceramic substrate according to the present invention comprises a ceramic body having a main extension plane.

[0013] The ceramic body is preferably a body formed from ceramic. The body can have any geometric shape, but is preferably designed as a rectangular parallelepiped. The ceramic body has a boundary surface, and in the case of a rectangular parallelepiped, it has six boundary surfaces. The primary boundary surface in this specification preferably refers to the boundary surface having the largest surface area that is planar-connected to the metal layer. The primary boundary surface is preferably located in the main extension plane or extends parallel to the main extension plane. Therefore, it is understood that the main extension plane of the ceramic body preferably extends parallel to or surrounds the primary boundary surface of the ceramic body.

[0014] The ceramic of the ceramic body is preferably an insulating ceramic. According to a preferred embodiment, the ceramic is selected from the group consisting of oxide ceramics, nitride ceramics, and carbide ceramics. According to a more 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 an even more particularly highly 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) (3a) rare earth metals, (3b) metals of Group 2 elements of the periodic table of elements, (3c) zirconium, (3d) copper, (3e) molybdenum, and (3f) silicon, at least one element selected from the group consisting of, and optionally (4) inevitable impurities. According to yet another very particularly preferred embodiment, the ceramic body does not contain bismuth, gallium, and zinc.

[0015] The ceramic body preferably has a thickness in the range of 0.05 to 10 mm, more preferably in the range of 0.1 to 5 mm, and particularly preferably in the range of 0.15 to 3 mm.

[0016] The metal-ceramic substrate according to the present invention comprises a metal layer planar-connected to the ceramic body, and the metal layer comprises a structured region that (i) partially contains a solid material and (ii) partially contains a non-solid material.

[0017] 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 by a DCB (Direct Copper Bonding) process. According to a further preferred embodiment, the metal layer is connected to the ceramic body by a soldering process. The soldering process can be, for example, an AMB (Active Metal Brazing) process, and preferably, a silver-free soldering alloy (the silver content is, for example, less than 1.0 weight percent based on the solid content of the soldering alloy) or a silver-containing soldering alloy (the silver content is, for example, at least 50 weight percent based on the solid content of the soldering alloy) is used. Thus, the metal layer may include a connection layer that contacts the ceramic body. The connection layer can be, for example, a solder layer (especially a brazing layer) or a diffusion layer.

[0018] The metal layer is connected to the ceramic body in a planar manner. Thus, the metal layer is preferably connected to the primary boundary surface of the ceramic body in a planar manner. The metal layer is preferably not connected to the entire primary boundary surface of the ceramic body. In particular, the primary boundary surface of the ceramic body can be larger than the surface of the metal layer connected to the ceramic body. In these cases, the primary boundary surface of the ceramic body protrudes. In addition, the metal layer is preferably structured. The structured part preferably means a recess in the metal layer that separates the individual parts of the metal layer from each other and thus electrically insulates them. Such a structured part is usually made by etching techniques.

[0019] Thus, the metal layer comprises a structured region. The structured region is a part of the metal layer that includes the structured part. The structured part is preferably a recess in the metal layer.

[0020] The metal layer further has a primary metal surface parallel to the primary boundary surface of the ceramic body on the upper surface (preferably on the side opposite to the primary boundary surface of the ceramic body). Thus, this primary metal surface includes the metal of the metal layer interrupted by the recesses of the structured region.

[0021] The structured region has a region containing a solid material and a region containing a non-solid material.

[0022] The region containing the solid material preferably contains at least one element from the group consisting of (i) the metal of the metal layer (including optionally a connection layer if present, e.g., in the case of AMB), (ii) the metal of the contact region (especially silver), and (iii) the material of the ceramic body. For this reason, the solid material preferably contains (i) the metal of the metal layer (including optionally a connection layer) and optionally (ii) the metal of the contact region (especially silver) and / or (iii) the material of the ceramic body.

[0023] According to a preferred embodiment, the structured region between the primary metal surface (excluding the contact region) and the primary interface of the ceramic body does not contain the main metal of the contact region, especially does not contain silver. According to a more preferred embodiment, the solid material in the structured region between the primary metal surface (excluding the contact region) and the primary interface of the ceramic body has no deposition of the main metal of the contact region, especially silver. Thus, according to a particularly preferred embodiment, the solid material in the structured region between the primary metal surface (excluding the contact region) and the primary interface of the ceramic body does not have a layer consisting of the main metal of the contact region, especially silver. The main metal of the contact region is preferably the metal having the highest weight ratio in the contact region.

[0024] The region containing the non-solid material preferably contains a gas-phase material. For this reason, the non-solid material preferably contains a gas-phase material. The non-solid material is preferably a gas-phase material filling the recesses of the metal layer. This gas-phase material usually originates from the ambient atmosphere. Thus, preferably, the gas-phase material contains at least one element selected from the group consisting of nitrogen, oxygen, and noble gases. Most preferably, the gas-phase material is air.

[0025] In a preferred embodiment, the recess extends from the primary interface surface of the ceramic body to the primary metal surface in a direction perpendicular to the primary interface surface of the ceramic body. The recess preferably forms a channel filled with a non-solid material up to at least 50% by volume, more preferably up to at least 80% by volume, even more preferably up to at least 90% by volume, particularly preferably up to at least 95% by volume, most preferably up to at least 99% by volume, and especially completely.

[0026] The metal layer preferably contains at least one metal selected from the group consisting of copper, aluminum, and molybdenum. According to a more preferred embodiment, the metal layer contains at least one metal selected from the group consisting of copper and molybdenum. According to a particularly preferred embodiment, the metal layer contains copper. According to an even more preferred embodiment, the metal layer consists of copper and inevitable impurities. According to a more 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, particularly preferably at least 75% by weight, based on the total weight of the metal layer (preferably including any connection layer that may be present).

[0027] 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 by a DCB (Direct Copper Bonding) process or a soldering process. The soldering process can be, for example, an AMB (Active Metal Brazing) process, and preferably, a solder alloy containing no silver (the silver content is, for example, less than 1.0% by weight based on the solid content of the solder alloy) or a silver-containing solder alloy (the silver content is, for example, at least 50% by weight based on the solid content of the solder alloy) is used. In this case, the metal layer may also contain, in addition to the copper derived from the copper foil, the metal of the connection layer, particularly the metal of the solder layer (for example, the brazing layer) or the diffusion layer.

[0028] The metal layer preferably has a thickness in the range of 0.01 to 10 mm, particularly preferably in the range of 0.03 to 5 mm, and very particularly preferably in the range of 0.05 to 3 mm.

[0029] The metal-ceramic substrate according to the present invention contains silver and has a contact area disposed on the metal layer. The contact area preferably serves to facilitate the connection of the semiconductor to the metal layer. The semiconductor is preferably connected to the metal layer by sintering, soldering or adhesion. In particular, since 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 area. The contact area is preferably made of silver or a silver-containing alloy. In the case of a silver-containing alloy, it contains at least 50% by weight of silver based on the weight of the silver alloy. Preferably, the contact area is provided at all positions on the metal layer of the metal-ceramic substrate where the semiconductor is to be mounted later. The contact area can be formed on the metal layer of the metal-ceramic substrate using various techniques. For example, it is possible to provide the contact area by deposition. The deposition can be physical deposition or chemical deposition. For example, vapor growth is considered as a physical deposition method. Preferred methods of vapor growth are, in particular, electron beam deposition, laser beam deposition, arc discharge deposition or cathode sputtering. In the case of chemical deposition, the contact area is preferably made by applying a composition containing silver or a silver precursor to the metal layer. For example, the composition containing silver can be fired to form 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 may be subjected to a treatment that releases silver and enables the adsorption of silver to the metal layer. This treatment can be carried out, for example, by bringing the silver precursor into contact with the metal layer. Methods for depositing silver or a silver compound to form a contact area on the metal layer of the metal-ceramic substrate are known to those skilled in the art.

[0030] The structured area of the metal layer has a geometric shape in a cross-section passing through the metal-ceramic substrate perpendicular to the main extension plane and satisfies the following requirements. S(BC solid ) / S(BC total )>60% In the formula, S(BC total ) represents the total length of the line between point B and point C, S(BC solid ) represents the length of the line between point B and point C that intersects the solid material.

[0031] According to a preferred embodiment, in a cross-section passing through the metal-ceramic substrate perpendicular to the main extension plane, the structured region of the metal layer has a geometric shape such that the ratio S(BC solid ) / S(BC total ) is > 70%, more preferably > 80%, still more preferably > 85%, particularly preferably > 90%, and most preferably > 95%.

[0032] According to a more preferred embodiment, in a cross-section passing through the metal-ceramic substrate perpendicular to the main extension plane, the structured region of the metal layer has a geometric shape such that the ratio S(BC solid ) / S(BC total ) is in the range of 70 - 100%, particularly preferably in the range of 80 - 100%, and most preferably in the range of 80 - 99%.

[0033] To determine points B and C, a cross-section of the structured region of the metal layer of the metal-ceramic substrate is observed. The cross-section extends perpendicular to the main extension plane of the ceramic body. Preferably, the observation of the cross-section can be performed by cutting the metal-ceramic substrate perpendicular to the main extension plane of the ceramic body and capturing an image of the thus obtained cross-section with an optical microscope.

[0034] Points B and C of line BC can be determined in the cross-section as described later.

[0035] For the sake of explanation, reference is made to FIGS. 1 and 2 as examples.

[0036] FIG. 1 schematically shows this type of metal-ceramic substrate.

[0037] FIG. 2 shows a part of a cross-section passing through the metal-ceramic substrate according to the present invention.

[0038] The metal-ceramic substrate 1 shown in FIG. 1 includes a ceramic body 10. The main extension plane 2 of the ceramic body 10 is indicated (as a line) by reference numeral 2. The ceramic body 10 has a primary boundary surface 15. The metal-ceramic substrate 1 includes a metal layer 20 that is planar-connected to the primary boundary surface 15 of the ceramic body 10. In the embodiment according to FIG. 1, the metal-ceramic substrate 1 further includes a further metal layer 200 that is planar-connected to the ceramic body 10. The metal layer 20 has a contact region 8 containing silver. The metal layer 20 has a structured portion. This is formed by the recess 22 of the metal layer 20. The recess 22 contains a non-solid material. The structured region 4 includes the metal layer 20 and the recess 22 in several regions. Accordingly, the structured region 4 partially includes a solid material 50 formed by the metal of the metal layer 20 and partially includes a non-solid material (e.g., a gas-phase material) filling the recess 22. The gas-phase material is usually 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 primary metal surface 24 parallel to the primary boundary surface 15 of the ceramic on the upper surface opposite to the primary boundary surface 15 of the ceramic. This primary metal surface 24 includes the metal of the metal layer 20 interrupted by the recess 22 in the structured region. The recess 22 extends in a direction perpendicular to the primary boundary surface 15 of the ceramic from the primary boundary surface 15 of the ceramic to the primary metal surface 24, and preferably forms a channel that is completely or mostly filled with a non-solid material.

[0039] In a part of a cross-section through the metal-ceramic substrate according to the invention shown in FIG. 2, a part of the structured region can be seen. A region of the ceramic body 10 that is planar-connected to the region of the metal layer 20 is shown. The contour line 40 separates the non-solid material and the solid material 50 of the recess 22 of the metal layer 20.

[0040] The determination of points B and C of line BC in the cross-section is preferably performed in a plurality of steps.

[0041] In the first step, an optimum fit line 30 between the ceramic body 10 and the metal layer 20 is determined. For this purpose, the regions of the ceramic body 10 and the metal layer 20 are optically determined, and the optimum 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.

[0042] In the second step, a contour line 40 that separates the solid material 50 from the non-solid material in the recess 22 is determined. The solid material 50 is optically determined, which is usually the material of the metal layer 20. The non-solid material is also optically determined. The non-solid material is usually a vapor-phase material that fills the structured part as the recess 22 of the metal layer 20.

[0043] In the third step, a point A where a perpendicular line to the optimum fit line 30 intersects the contour line 40 is determined on the perpendicular line to the optimum fit line 30 at a distance of 150 μm from the optimum fit line 30.

[0044] In the fourth step, a point B where a perpendicular line to the optimum fit line 30 intersects the contour line 40 is determined on the perpendicular line to the optimum fit line 30 at a distance of 80 μm from the optimum fit line 30.

[0045] In the fifth step, on the straight line passing through point A and point B, a point C where the straight line intersects the optimum fit line 30 is determined.

[0046] A cross-section passing through the metal-ceramic substrate perpendicular to the main extension plane of the ceramic body, and the capture (incident light / bright field) of the cross-section thus obtained using an optical microscope are preferably performed as described later.

[0047] In the first step, first, from the metal-ceramic substrate to be inspected, 100 mm 2 ~ maximum 400 mm 2A cuboid sample blank having a rectangular base within the range is cut out by sawing perpendicularly to the plane formed by the primary metal surface of the metal layer of the metal-ceramic substrate using a diamond saw blade at a low rotational speed and a lubricant (Exakt). Thus, the sample blank has a sample surface to be subjected to inspection. Thus, this sample surface extends perpendicularly to the plane formed by the primary metal surface of the metal layer of the metal-ceramic substrate before sawing. Thus, it has a part of the ceramic body and a part of the metal layer (including an optional connecting layer). The sample blank is first embedded in a mold using a low-shrinkage epoxy resin (Caldo-Fix, Struers), and the sample surface is oriented perpendicularly to the mold wall. Then, the epoxy resin is 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 achieve a roughness of 1 μm or less.

[0048] In a second step, the structured region of the metal layer is identified in the analysis zone at a magnification of 200 times using an optical microscope (Leica, DM6000M, incident light / bright field), and this region partially contains solid material and partially contains non-solid material. The solid material and the non-solid material can be clearly distinguished in the structured region by their different colors.

[0049] Line S(BC total ) and S(BC solid ) are preferably determined in a standard manner, for example, using image analysis software (such as IMS Client, Imagic).

[0050] Preferably, the term "in cross-section" as used herein refers to the total cross-section (preferably representative), more preferably at least 10 cross-sections, most preferably 20 or fewer cross-sections, especially 10 cross-sections. The cross-sections preferably extend parallel to each other and are equally spaced from each other. The ratio S(BC solid) / S(BC total To determine , preferably the following procedure is used. 1. At least 10, particularly preferably 10, different cross-sections of the structured region are inspected. For each of these cross-sections, the ratio S(BC solid ) / S(BC total ) is determined. For each of these cross-sections, the ratio S(BC solid ) / S(BC total ) is averaged to obtain the ratio S(BC solid ) / S(BC total ) for the observed metal-ceramic substrate.

[0051] According to a preferred embodiment, the sample standard deviation SSD of the ratio S(BC solid ) / S(BC total ) over at least 10 different cross-sections of the structured region of the metal layer, more preferably over 20 or fewer different cross-sections of the structured region of the metal layer, most preferably over 10 different cross-sections of the structured region of the metal layer, is 10% or less, more preferably 7% or less, particularly preferably 5% or less, most preferably 3% or less. The sample standard deviation SSD is determined using the following formula.

[0052]

Number

[0053]

Number

[0054] Surprisingly, it has been found that the metal-ceramic substrates having the geometric shape according to the present invention have improved thermal shock resistance as compared with the metal-ceramic substrates according to 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 has been found that the proportion of solid material in the metal layer at the boundary with the surface of the ceramic body is significantly lower in the metal-ceramic substrates according to the prior art as long as they have a contact area containing silver disposed in the metal layer.

[0055] Without being bound by theory, this may be due to the fact that in the prior art, the manufactured metal-ceramic substrates are usually first structured and then silver-plated on the surface to create a contact area. Silver plating is typically performed by immersing the structured metal-ceramic substrate in a bath containing a solution of silver ions. The metal ions are electrochemically dissolved from the metal layer of the metal-ceramic substrate and replaced by the silver ions. Within the scope of the present invention, it has been observed that in this process, the silver ions are mainly deposited on the surface of the metal-ceramic substrate, while the metal ions of the metal layer are mainly eluted in the region near the ceramic body (the masking for structuring the edge of the metal layer is washed away by the solution containing silver ions, so the effect cannot be prevented by the masking of the structured part). This effect is particularly pronounced when the metal layer in the region adjacent to the ceramic body is already structured and thus no longer homogeneous. This results in the removal of solid material, particularly the metal of the metal foil, from the metal foil in the region close to the ceramic body, thus creating a weakness for the peeling of the metal layer from the ceramic body, which has an adverse effect on the thermal shock resistance. However, according to the present invention, a structured region having a sufficient amount of solid material is created in the region close to the ceramic body, thereby preventing the peeling of the metal layer from the ceramic body and achieving an improvement in the thermal shock resistance.

[0056] According to a preferred embodiment, the metal-ceramic substrate comprises a further (second) metal layer that is planar-connected to the ceramic body. The further metal layer is preferably planar-connected to a boundary surface (preferably extending parallel to the primary boundary surface) on the side opposite to the primary boundary surface of the ceramic. The further (second) metal layer may have the same properties as the (first) metal layer, or its properties may be different from those of the (first) metal layer. For the properties of the further (second) metal layer, reference is made to the above description.

[0057] The metal-ceramic substrate according to the present invention can be used particularly in applications in electronics, especially in the field of power electronics.

[0058] Therefore, the present invention also provides an electronic component comprising the above-described metal-ceramic substrate.

[0059] According to a preferred embodiment, such an electronic component comprises a base plate. The base plate is preferably planar-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 a further preferred embodiment, the electronic component comprises at least one chip. The at least one chip is preferably planar-connected to a contact region containing silver disposed on the metal layer. According to a further preferred embodiment, the electronic component comprises a metal-ceramic substrate having a first metal layer and a second metal layer (the first metal layer is preferably on the side opposite to the second metal layer), a base plate, and at least one chip, and the at least one chip is connected to the first metal layer of the metal-ceramic substrate via a contact region containing silver disposed on the metal layer, and the base plate is connected to the second metal layer of the metal-ceramic substrate.

[0060] The metal-ceramic substrate according to the present invention can be obtained by various manufacturing processes.

[0061] According to a preferred embodiment, the method is a method for manufacturing a metal-ceramic substrate provided with a structuring part and a contact area containing silver, wherein a) providing a metal-ceramic substrate, wherein the metal-ceramic substrate comprises a1) a ceramic body, and a2) a metal layer planar-connected to the ceramic body, and b) applying a first mask to the metal layer; and c) depositing a silver-containing layer on the unmasked areas of the structured metal layer to generate a contact area containing silver; and d) removing the first mask; and e) applying a second mask to the metal layer; and f) etching the unmasked areas of the metal layer to thereby obtain a structuring part; and g) removing the second mask.

[0062] Thus, in this method, it is preferable to first provide a metal-ceramic substrate. This metal-ceramic substrate comprises a ceramic body and a metal layer planar-connected to the ceramic body. The metal-ceramic substrate can be a standard metal-ceramic substrate. The ceramic body and the metal layer may have a composition as described above with respect to the metal-ceramic substrate. The metal layer can preferably be materially joined to the ceramic body as described above with respect to the metal-ceramic substrate.

[0063] In the method, it is preferable to apply a first mask to the metal layer. The first mask serves to protect the masked area of the metal layer from the deposition of the silver-containing layer in subsequent steps. Thereby, it is ensured that the silver-containing layer is deposited only on the unmasked areas of the metal layer of the metal-ceramic substrate. Therefore, the masking is designed such that the silver-containing layer cannot be deposited on the masked areas of the metal layer of the metal-ceramic substrate. The type of masking is not further limited. The masking can be, for example, a standard negative mask or positive mask. The masking can be made of, for example, a film (or dry film) or a liquid, and optionally, printed or sprayed on some areas of the surface of the metal-ceramic substrate. For example, a standard etching resist can be used. These etching resists preferably contain a curable polymer (for example, a photocurable polymer). According to one possible embodiment, a photosensitive film is applied to the metal layer of the metal-ceramic substrate, and then exposed in the masked areas to obtain the first mask. Then, the unexposed areas of the photosensitive film can be removed by a conventional method (for example, using a sodium carbonate solution).

[0064] After the application of the first mask, it is preferable to deposit a silver-containing layer on the unmasked areas of the metal layer to generate a contact area containing silver. The silver-containing layer is preferably a layer made of silver or a silver alloy, and particularly preferably a layer made of silver. The silver-containing layer is preferably deposited by a conventional method. The silver-containing layer can be deposited, for example, electrochemically, electrolessly, or chemically. Chemical deposition by applying a silver-containing solution involving charge exchange between metals is preferred, whereby the metal of the metal layer is partially dissolved while silver in the solution is deposited. According to a preferred embodiment, the silver-containing solution contains a silver salt, particularly preferably silver nitrate. According to a 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 to 1.5 g / l, particularly preferably in the range of 0.6 to 1.4 g / l, and most preferably in the range of 0.8 to 1.2 g / l.

[0065] Preferably, after depositing a silver-containing layer on the unmasked area of the metal layer to obtain a contact area containing silver, the first mask is removed. The first mask can be removed by a standard method. 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.

[0066] After removing the first mask, it is preferable to apply a second mask to the metal layer. The second mask serves to protect the masked area of the metal layer of the metal-ceramic substrate from etching in subsequent steps. Thereby, it is ensured that the metal layer of the metal-ceramic substrate can be accessed only in the areas that are not masked and are intended to be structured for etching. Therefore, the masking is designed such that etching does not occur in the masked areas of the metal layer. According to a preferred embodiment, the second mask is applied to the area of the metal-ceramic substrate where the first mask has not yet been applied. The type of masking is not further limited. The masking can be, for example, a standard negative mask or positive mask. The masking can be made, for example, of a film (or dry film) or a liquid, and optionally, printed or sprayed on some areas of the surface of the metal-ceramic substrate. For example, standard etching resists can be used. These etching resists preferably contain a curable polymer (e.g., a photocurable polymer). According to one possible embodiment, a photosensitive film is applied to the partially silver-plated surface of the metal-ceramic substrate and then exposed in the areas to be masked to obtain the second mask. Then, the unexposed areas of the photosensitive film can be removed by a conventional method (e.g., using a sodium carbonate solution).

[0067] After applying the second mask to the metal layer, it is preferable to etch the unmasked areas of the metal layer to obtain a structured portion. The etching is preferably performed by standard conventional methods. Accordingly, the etching is preferably performed using a standard etching solution. According to a preferred embodiment, the etching solution is selected from the group consisting of an FeCl3 etching solution and a CuCl2 etching solution. If necessary, for example, an additional etching solution can be used to structure the unmasked areas of an optionally included connection layer. According to a preferred embodiment, the further etching solution can be selected from the group consisting of an etching solution containing hydrogen peroxide and an etching solution containing ammonium persulfate. For example, the further etching solution may be an etching solution containing ammonium fluoride and fluoroboric acid (e.g., HBF4) and hydrogen peroxide and / or ammonium persulfate.

[0068] Preferably, after etching the unmasked areas of the metal layer to generate a structured portion, the second mask is removed. The second mask can be removed by standard methods. For this purpose, the metal-ceramic substrate can be treated with an alkaline solution (e.g., a 2.5% sodium hydroxide solution) to remove the second mask.

[0069] The method described herein makes it possible to obtain a metal-ceramic substrate provided with a structured portion and a contact area containing silver. By creating a contact area containing silver, chips can be more easily connected to the metal-ceramic substrate using common processes such as sintering or soldering. The metal-ceramic substrate thus obtained is characterized by particularly high thermal shock resistance.

[0070] Exemplary Embodiment The present invention will be described in more detail below using exemplary embodiments, but should not be understood as limiting.

Example

[0071] As an example, a metal-ceramic substrate was used in which both sides of a silicon nitride ceramic body having dimensions of 177.8×139×0.32 mm were connected to copper layers having dimensions of 170×132×0.3 mm using an AMB (active metal brazing) process. This copper-ceramic substrate was first cleaned after manufacturing.

[0072] Next, a photosensitive film was applied to both copper layers of the copper-ceramic substrate using a hot roll laminator. In order to cure the polymer contained in the photosensitive film to obtain a first mask, the photosensitive film was exposed at 30 mJ / cm 2 in each of the areas to be masked. Then, a sodium carbonate solution (concentration = 10 g / l) was used to chemically remove the unexposed areas of the photosensitive film. After applying the first mask, the copper-ceramic substrate was rinsed and cleaned. Thereafter, a silver-containing contact area was deposited on the unmasked areas of the copper layer of the copper-ceramic substrate. For this purpose, the copper-ceramic substrate having the first mask was 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 the deposition of the silver-containing contact area, the copper-ceramic substrate was carefully rinsed with water to remove the residue. Then, in a stripping system, the first mask was removed using a 2.5% sodium hydroxide solution.

[0073] Next, a photosensitive film was applied to both copper layers of the copper-ceramic substrate, each having a silver-containing contact area, using a hot roll laminator. In order to cure the polymer contained in the photosensitive film to obtain a second mask, the photosensitive film was exposed at 30 mJ / cm 2It was exposed. Subsequently, the unexposed areas of the photosensitive film were chemically removed using a sodium carbonate solution (concentration = 10 g / l). After applying the second mask, the copper-ceramic substrate was rinsed and washed again. Subsequently, the unmasked areas of the copper layer of the copper-ceramic substrate provided with the silver-containing contact areas were chemically etched. For this purpose, in an etching system, a hydrochloric acid cupric chloride solution containing hydrogen peroxide (copper ion content = 160 g / l) was sprayed onto the copper-ceramic substrate. The etching was carried out at a temperature of 50 °C and a spray pressure of 2.8 bar. By etching, the material was removed from the unmasked areas of the copper layer of the copper-ceramic substrate. Subsequently, the metal-ceramic substrate was rinsed. Subsequently, the unmasked areas of the connection layer contained in the metal-ceramic substrate were also chemically etched. For this purpose, in the etching system, an etching solution containing ammonium fluoride, fluoboric acid and hydrogen peroxide was sprayed again onto the metal-ceramic substrate. Subsequently, the copper-ceramic substrate was rinsed and dried. Subsequently, in a stripping system, the second mask was removed using a 2.5% sodium hydroxide solution.

[0074] The obtained copper-ceramic substrate was laser cut into individual parts having dimensions (20.5 × 17.0 mm) and could then be used for further investigation and the production of electronic components.

[0075] Comparative Example The comparative example was carried out in the same manner as the example, but the order of (i) depositing a silver-containing layer on the unmasked areas of the copper layer to obtain a contact area containing silver and (ii) etching the unmasked areas of the copper layer to obtain a structured part was reversed.

[0076] For the comparative example, a metal-ceramic substrate similar to that of the example, in which both sides of a silicon nitride ceramic body having dimensions of 177.8 × 139 × 0.32 mm were connected to a copper layer having dimensions of 170 × 132 × 0.3 mm by an AMB (active metal brazing) process, was used. This copper-ceramic substrate was first washed after production.

[0077] Next, a hot roll laminator was used to apply a photosensitive film to both copper layers of the copper-ceramic substrate. To cure the polymer contained in the photosensitive film to obtain a first mask, the photosensitive film was exposed at 30 mJ / cm 2 in each of the masked areas. Then, a sodium carbonate solution (concentration = 10 g / l) was used to chemically remove the unexposed areas of the photosensitive film. After applying the first mask, the copper-ceramic substrate was rinsed and cleaned. Next, the unmasked areas of the copper layer of the copper-ceramic substrate were chemically etched. For this purpose, in an etching system, a cupric chloride solution containing hydrogen peroxide (copper ion content = 160 g / l) was sprayed onto the copper-ceramic substrate. The etching was carried out at a temperature of 50 °C and a spray pressure of 2.8 bar. By etching, material was removed from the unmasked areas of the copper layer of the copper-ceramic substrate. Then, the metal-ceramic substrate was rinsed. Next, the unmasked areas of the connection layer contained in the metal-ceramic substrate were also chemically etched. For this purpose, in an etching system, an etching solution containing ammonium fluoride, fluoroboric acid, and hydrogen peroxide was sprayed again onto the metal-ceramic substrate. Then, the copper-ceramic substrate was rinsed and dried. Next, in a stripping system, the first mask was removed using a 2.5% sodium hydroxide solution.

[0078] Next, a hot roll laminator was used to apply a photosensitive film to both etched sides of the copper-ceramic substrate. To cure the polymer contained in the photosensitive film to obtain a second mask, the photosensitive film was exposed at 30 mJ / cm 2It was exposed. Next, the unexposed areas of the photosensitive film were chemically removed using a sodium carbonate solution (concentration = 10 g / l). After applying the second mask, the copper-ceramic substrate was rinsed and washed again. Thereafter, a silver-containing contact area was 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 was 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 the deposition of the silver-containing contact area, the copper-ceramic substrate was carefully rinsed with water to remove the residues. Next, in the stripping system, the second mask was removed using a 2.5% sodium hydroxide solution.

[0079] The obtained copper-ceramic substrate was laser cut into individual parts having dimensions (20.5×17.0 mm), and then could be used for further investigation and the manufacture of electronic components.

[0080] Evaluation: The ratio S(BC solid ) / S(BC total ) was determined for the metal-ceramic substrates obtained in the examples and comparative examples. For this purpose, as described herein, the metal-ceramic substrates were cut perpendicular to the main extension plane of each ceramic body, and images of the cross-sections thus obtained were taken using an optical microscope. Points A, B, and C were determined in the cross-section. Next, the ratio S(BC solid ) / S(BC total ) was determined for each of the metal-ceramic substrates. For this purpose, 10 different cross-sections of the structured areas in the metal layer of the relevant metal-ceramic substrates were examined, and for each of these cross-sections, the ratio S(BC solid ) / S(BC total ) was determined to obtain the ratio S(BC solid ) / S(BC total ) for each of these cross-sections. The average value of the ratio S(BC solid ) / S(BC total ) was calculated for each of these cross-sections. Furthermore, the standard deviation SSD was determined.

[0081] 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 shows 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.

[0082] The results are shown in Table 1.

[0083] [Table 1]

[0084] The thermal shock resistance of the metal-ceramic substrate was examined. For this purpose, a thermal shock resistance test was conducted.

[0085] Thermal shock resistance test: In the preparation of the thermal shock resistance test, first, an ultrasonic microscope (PVA Tepla SAM300) was used to confirm whether the metal-ceramic substrate was in a complete state. Only metal-ceramic substrates that did not show delamination between the ceramic body and the metal layer, or other deformations (such as cracks) that could cause delamination of the metal layer from the ceramic body, were used for the test. To test the thermal shock resistance, the metal-ceramic substrate was repeatedly exposed to a cold liquid (temperature -65°C, Galden Do2TS) and a hot liquid (temperature +150°C, Galden Do2TS) in a cycle chamber (ESPEC TSB-2151) for 5 minutes each. An ultrasonic microscope (PVA Tepla SAM300) was used to reconfirm the delamination and other deformations of the metal-ceramic substrate every 1000 cycles. The test was terminated after 3000 cycles. Then, an ultrasonic microscope (PVA Tepla SAM300) was used to reexamine the delamination and other deformations of the metal-ceramic substrate. The state of each metal-ceramic substrate after the thermal shock resistance test was compared with the state of the metal-ceramic substrate before the thermal shock resistance test with respect to delamination and other deformations. Delamination and other deformations (such as cracks) appeared as white discoloration in the ultrasonic images.

[0086] The results are shown in Table 2.

[0087]

Table 2

[0088] The results show that, with respect to thermal shock resistance, the metal-ceramic substrate according to the present invention is clearly superior to the metal-ceramic substrate of the comparative example.

Brief Description of the Drawings

[0089]

Figure 1

Figure 2

Figure 3

Figure 4

Description of the Reference Numerals

[0090] 1 Metal-ceramic substrate 2 Main extension plane 4 Structured region 8 Contact region 10 Ceramic body 15 Primary interface 20 Metal layer 22 Recess 24 Primary metal surface 40 Contour line 50 Solid material 200 Additional metal layer

Claims

1. A metal-ceramic substrate, comprising: a) a ceramic body having a major extension plane; and b) a metal layer planar-connected to the ceramic body, the metal layer comprising: (i) partially containing a solid material; and (ii) a structured region partially containing a non-solid material; and c) a contact region containing silver and disposed on the metal layer, wherein in a cross-section passing through the metal-ceramic substrate perpendicular to the major extension plane, the structured region has a geometric shape satisfying the following requirements, i.e., wherein points B and C are determined as follows, i.e., S(BC ｓｏｌｉｄ ) / S(BC ｔｏｔａｌ ) > 60% having a geometric shape satisfying the following formula, wherein S(BC ｔｏｔａｌ ) represents the total length of the line between point B and point C, S(BC ｓｏｌｉｄ ) represents the length of the line between point B and point C that intersects the solid material, points B and C are determined as follows:

1. The best-fit line between the ceramic body and the metal layer is determined; 2. The contour line separating the solid material from the non-solid material is determined; 3. Point A, at which a perpendicular to the best-fit line intersects the contour line, is determined on the perpendicular to the best-fit line at a distance of 150 μm from the best-fit line; 4. Point B, at which a perpendicular to the best-fit line intersects the contour line, is determined on the perpendicular to the best-fit line at a distance of 80 μm from the best-fit line; 5. Point C, at which the straight line passing through points A and B intersects the best-fit line, is determined on the straight line passing through points A and B. A metal-ceramic substrate characterized by the above.

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

3. The metal-ceramic substrate according to claim 1 or 2, wherein the metal layer contains copper.

4. The metal-ceramic substrate according to any one of claims 1 to 3, wherein the solid material contains the metal of the metal layer.

5. The metal-ceramic substrate according to any one of claims 1 to 4, wherein the non-solid material contains a gaseous-phase material.

6. Satisfying the following requirements, i.e., S(BC ｓｏｌｉｄ ) / S(BC ｔｏｔａｌ ) > 95% wherein. A metal-ceramic substrate according to any one of claims 1 to 5, characterized by the above.

7. The sample standard deviation SSD of the ratio S(BC ｓｏｌｉｄ ) / S(BC ｔｏｔａｌ ) over at least 10 different cross-sections of the structured region of the metal layer is 10% or less, and the metal-ceramic substrate according to any one of claims 1 to 6 is characterized thereby.

8. An electronic component comprising the metal-ceramic substrate according to any one of claims 1 to 7.

9. A method for manufacturing a metal-ceramic substrate provided with a structured portion and a contact region containing silver, the method comprising: a) providing a metal-ceramic substrate, wherein the metal-ceramic substrate is a1) a ceramic body, and a2) a metal layer planar-connected to the ceramic body, comprising a step; b) applying a first mask to the metal layer; c) depositing a silver-containing layer in the unmasked region of the structured metal layer to generate a contact region containing silver; d) removing the first mask; e) applying a second mask to the metal layer; f) etching the unmasked region of the metal layer to thereby obtain a structured portion; g) removing the second mask; A method comprising.

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