A metal-ceramic substrate having a contact area

Abstract

The present invention relates to a metal-ceramic substrate and an electronic component comprising 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) contains a solid material in some regions and (ii) contains a non-solid material in some regions; and c) a contact region containing silver disposed on the metal layer. In the metal-ceramic substrate, the structured region has a geometric shape that satisfies the following requirement in a cross-section perpendicular to the main extension plane and passing through the metal-ceramic substrate, that is A(BCD solid ) / A(BCD total )>70%, and has wherein A(BCD total ) represents the total area of the triangle drawn by points B, C and D, and A(BCD solid ) represents the area occupied by the solid material of the triangle drawn by points B, C and D, which is characterized in that.

Description

Technical Field

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

[0002] Metal-ceramic substrates play an important role in the field of power electronics. They are important elements when constructing electronic components and ensure the rapid dissipation of a large amount of heat during the operation of the 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. When the copper foil thus treated is applied to a ceramic body and the composite is fired, the copper compound melts, wets the surface of the ceramic body, and a stable integral bond is achieved 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 that contains a metal (usually silver) having 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 to the remaining solder of the ceramic material, forming a reaction layer, while the metal having 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 joining a copper foil to a ceramic body using a solder containing 50 to 89 wt% silver, as well as copper, bismuth and an active metal. 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 join the metal foil to the ceramic body. These solders are based, for example, on a high melting point metal (especially copper), a low melting point metal (such as bismuth, indium or tin), and an active metal (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 independent class of compounds, leads to a change in material properties, and results in compatibility with other solder components and changed joining conditions because the basis of the solder used is formed by a different metal (copper instead of silver).

[0005] When constructing an electronic component, a chip is usually mounted on a metal-ceramic substrate. In order 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 on which the chip is to be mounted. By providing a silver-containing contact area, the chip can be more easily joined to the metal-ceramic substrate using common methods 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 structuring. The contact area is then provided by partially applying a silver-containing coating to the surface of the structured metal-ceramic substrate.

[0006] The metal-ceramic substrate thus manufactured is usually exposed to large temperature changes during operation as part of an electronic component. During the interruption of operation, depending on the environment, the temperature can, for example, drop to -20°C or lower, 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 a decrease in performance. Therefore, high thermal shock resistance is an important criterion for the suitability of metal-ceramic substrates in electronics, especially in power electronics applications.

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

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

[0009] This object is achieved by the metal-ceramic substrate according to claim 1. Accordingly, the present invention relates to a metal-ceramic substrate comprising a) a ceramic body having a main extension plane, and b) a metal layer bonded over a wide area to the ceramic body, the metal layer comprising (i) partially containing a solid material, and (ii) partially containing a non-solid material, and having a structured region, and c) a contact region containing silver disposed on the metal layer, in the metal-ceramic substrate, the structured region has a geometric shape satisfying the following requirements in a cross-section passing through the metal-ceramic substrate perpendicular to the main extension plane, A(BCD solid ) / A(BCD total )>70% wherein A(BCD total ) is the total area of the triangle drawn by points B, point C and point D, A(BCD solid) is the area occupied by the solid material of the triangle drawn by points B, C, and D, Points B, C, and D 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 separating the solid material from the non-solid material is determined, 3. On the perpendicular line to the best fit line, at a distance of 150 μm from the best fit line, point A where the perpendicular line to the best fit line intersects the contour line is determined, 4. On the perpendicular line to the best fit line, at a distance of 80 μm from the best fit line, point B where the perpendicular line to the best fit line intersects the contour line is determined, 5. On the straight line passing through points A and B, point C where the straight line intersects the best fit line is determined, 6. On the perpendicular line passing through point B to the best fit line, point D where the perpendicular line intersects the best fit line is determined, A metal-ceramic substrate is provided, characterized in that.

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

[0011] The metal-ceramic substrate according to the present invention comprises a ceramic body having a main extension plane.

[0012] 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 boundary surfaces, and in the case of a rectangular parallelepiped, it has six boundary surfaces. The main boundary surface is preferably, in this specification, called the boundary surface having the largest surface area that is joined to the metal layer over a wide range. 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 that extends parallel to or surrounds the main boundary surface of the ceramic body.

[0013] 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", "zirconia-reinforced 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, and optionally (4) inevitable impurities. According to yet another very particularly preferred embodiment, the ceramic body does not contain bismuth, gallium, and zinc.

[0014] 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.

[0015] The metal-ceramic substrate according to the present invention comprises a metal layer joined over a wide range to the ceramic body, and the metal layer has a structured region that (i) partially contains a solid material and (ii) partially contains a non-solid material.

[0016] The metal layer is preferably integrally joined to the ceramic body. According to a preferred embodiment, the metal layer is joined to the ceramic body by a DCB (direct copper bonding) method. According to an even more preferred embodiment, the metal layer is joined to the ceramic body by a brazing process. The brazing process can be, for example, preferably an AMB (active metal brazing) method using a silver-free brazing alloy (the silver content is, for example, less than 1.0 weight percent based on the solid content of the brazing alloy) or a silver-containing brazing alloy (the silver content is, for example, at least 50 weight percent based on the solid content of the brazing alloy). Thus, the metal layer may comprise a joining layer in contact with the ceramic body. The joining layer can be, for example, a solder layer (especially a brazing layer) or a diffusion layer.

[0017] The metal layer is joined over a wide area to the ceramic body. Thus, the metal layer is preferably joined over a wide area to the main interface surface of the ceramic body. The metal layer is preferably not joined over the entire main interface surface of the ceramic body. In particular, the main interface surface of the ceramic body can be larger than the surface of the metal layer joined to the ceramic body. In these cases, the main interface 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 for separating the individual parts of the metal layer from each other and thus electrically insulating them. Such a structured part is usually made using etching techniques.

[0018] Thus, the metal layer has a structured region. The structured region is understood to be a part of the metal layer that includes the structured part. The structured part is preferably a recess in the metal layer.

[0019] The metal layer further has a main metal surface parallel to the main interface surface of the ceramic body on an upper surface (preferably on the side opposite to the main interface surface of the ceramic body). Thus, this main metal surface comprises the metal of the metal layer interrupted by the recesses of the structured region.

[0020] The structured region has a region containing a solid material and a region containing a non-solid material.

[0021] The region containing the solid material preferably includes at least one element from the group consisting of (i) the metal of the metal layer (optionally including a bonding 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. Thus, the solid material preferably includes (i) the metal of the metal layer (optionally including a bonding layer) and optionally (ii) the metal of the contact region (especially silver) and / or (iii) the material of the ceramic body.

[0022] According to a preferred embodiment, the structured region between the main metal surface (excluding the contact region) and the main interface of the ceramic body does not contain the main metal of the contact region, especially silver. According to a further preferred embodiment, the solid material in the structured region between the main metal surface (excluding the contact region) and the main interface of the ceramic body does not contain deposits 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 main metal surface (excluding the contact region) and the main interface of the ceramic body does not have a layer made 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 percentage in the contact region.

[0023] The region containing the non-solid material preferably contains a gaseous material. Thus, the non-solid material preferably contains a gaseous material. The non-solid material is preferably a gaseous material filling the recesses of the metal layer. This gaseous material usually originates from the ambient atmosphere. Thus, preferably, the gaseous material contains at least one element selected from the group consisting of nitrogen, oxygen, and noble gases. The gaseous material is particularly very preferably air.

[0024] 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 filled with a non-solid material up to at least 50 volume percent, more preferably up to at least 80 volume percent, still more preferably up to at least 90 volume percent, particularly preferably up to at least 95 volume percent, particularly very preferably up to at least 99 volume percent, and particularly completely.

[0025] The metal layer preferably contains at least one metal selected from the group consisting of copper, aluminum, and molybdenum. According to a particularly preferred embodiment, the metal layer contains at least one metal selected from the group consisting of copper and molybdenum. According to a particularly very preferred embodiment, the metal layer contains copper. According to a further preferred embodiment, the metal layer consists of copper and inevitable impurities. According to a further preferred embodiment, the proportion of copper is at least 60 weight percent, more preferably at least 65 weight percent, still more preferably at least 70 weight percent, particularly preferably at least 75 weight percent, based on the total weight of the metal layer (preferably including any bonding layer that may exist).

[0026] According to a preferred embodiment, the metal layer is produced by integrally bonding a copper foil (preferably a foil made of high-purity copper) to the ceramic body. According to a preferred embodiment, the bonding can be carried out by the DCB (Direct Copper Bonding) method or the brazing method. The brazing process can be, for example, preferably the AMB (Active Metal Brazing) method using a silver-free brazing alloy (the silver content is, for example, less than 1.0 weight percent based on the solid content of the brazing alloy) or a silver-containing brazing alloy (the silver content is, for example, at least 50 weight percent based on the solid content of the brazing alloy). In this case, the metal layer may also contain metals from the bonding layer, particularly metals from the solder layer (e.g., the brazing layer) or the diffusion layer, in addition to the copper derived from the copper foil.

[0027] 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.

[0028] The metal-ceramic substrate according to the present invention has a contact region containing silver disposed on the metal layer. The contact region preferably serves to facilitate the bonding of the semiconductor to the metal layer. The semiconductor is preferably bonded 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 region. The contact region is preferably made of silver or a silver-containing alloy. In the case of a silver-containing alloy, it contains at least 50 weight percent silver based on the weight of the silver alloy. Preferably, the contact region is provided at all positions on the metal layer of the metal-ceramic substrate where the semiconductor is to be mounted later. The contact region can be formed on the metal layer of the metal-ceramic substrate using various techniques. For example, the contact region can be provided by deposition. The deposition can be, for example, physical deposition or chemical deposition. For example, vapor growth is conceivable as physical deposition. Preferred methods of vapor growth are, in particular, electron beam deposition, laser beam deposition, arc discharge deposition or cathode sputtering. In chemical deposition, the contact region 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 region on the metal layer of the metal-ceramic substrate are known to those skilled in the art.

[0029] In a cross-section passing through the metal-ceramic substrate perpendicular to the main extension plane, the structured region of the metal-ceramic substrate has a geometric shape that satisfies the following requirements: A(BCD solid) / A(BCD total ) > 70% Wherein, A(BCD total ) is the total area of the triangle drawn by points B, C, and D, A(BCD solid ) is the area of the triangle drawn by points B, C, and D occupied by the solid material, According to a preferred embodiment, the structured region of the metal-ceramic substrate has a geometric shape that satisfies a ratio A(BCD solid ) / A(BCD total ) > 75%, more preferably > 80%, even more preferably > 85%, particularly preferably > 90%, and particularly very preferably > 95% in a cross-section passing through the metal-ceramic substrate perpendicular to the main extension plane.

[0030] According to a more preferred embodiment, the structured region of the metal-ceramic substrate has a geometric shape such that the ratio A(BCD solid ) / A(BCD total ) is in the range of 75 - 100%, particularly preferably in the range of 90 - 100%, and most preferably in the range of 95 - 99% in a cross-section passing through the metal-ceramic substrate perpendicular to the main extension plane.

[0031] To determine the triangle drawn by points B, C, and D, the cross-section of the structured region 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 photographing the obtained cross-section using a scanning electron microscope.

[0032] The points B, C, and D of the triangle can be determined in the cross-section as described below. For the sake of explanation, refer to FIGS. 1 and 2 as examples.

Brief Description of the Drawings

[0033]

Figure 1

Figure 2

[0034] The metal-ceramic substrate 1 shown in Figure 1 comprises 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 main boundary surface 15. The metal-ceramic substrate 1 comprises a metal layer 20 which is joined over a wide area to the main boundary surface 15 of the ceramic body 10. In the embodiment according to Figure 1, the metal-ceramic substrate 1 further comprises a further metal layer 200 which is joined over a wide area to the ceramic body 10. The metal layer 20 has a contact area 8 containing silver. The metal layer 20 comprises a structured part. This is formed by a recess 22 in the metal layer 20. The recess 22 contains a non-solid material. The structured area 4 comprises the metal layer 20 and the recess 22 in part. Thus, the structured area 4 contains in part a solid material 50 formed by the metal of the metal layer 20 and a non-solid material (for example a gaseous material) filling the recess 22. The gaseous 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 main metal surface 24 parallel to the main boundary surface 15 of the ceramic on the upper surface opposite the main boundary surface 15 of the ceramic. This main metal surface 24 contains the metal of the metal layer 20 interrupted by the recess 22 in the structured area. The recess 22 extends in a direction perpendicular to the main boundary surface 15 of the ceramic from the main boundary surface 15 of the ceramic to the main metal surface 24 and preferably forms a channel completely or mostly filled with a non-solid material.

[0035] In a part of a cross-section through the metal-ceramic substrate according to the invention shown in Figure 2, a part of the structured area can be seen. The area of the ceramic body 10 joined over a wide area to the area 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.

[0036] The determination of points B and C of line BC in the cross-section is preferably carried out in several steps.

[0037] In the first step, the best-fit line 30 between the ceramic body 10 and the metal layer 20 is determined. For this purpose, the regions of the ceramic body 10 and the metal layer 20 are visually determined, and the best-fit line 30 is defined as the boundary between the ceramic body 10 and the metal layer 20 that can be observed in cross-section.

[0038] 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 visually determined, which is usually the material of the metal layer 20. The non-solid material is also visually determined. The non-solid material is usually a gaseous material that fills the structured part as the recess 22 of the metal layer 20.

[0039] In the third step, on the perpendicular line to the best-fit line 30, at a distance of 150 μm from the best-fit line 30, a point A where the perpendicular line to the best-fit line 30 intersects the contour line 40 is determined.

[0040] In the fourth step, on the perpendicular line to the best-fit line 30, at a distance of 80 μm from the best-fit line 30, a point B where the perpendicular line to the best-fit line 30 intersects the contour line 40 is determined.

[0041] In the fifth step, on the straight line passing through points A and B, a point C where the straight line intersects the best-fit line 30 is determined.

[0042] In the sixth step, on the perpendicular line to the best-fit line 30 passing through point B, a point D where the perpendicular line intersects the best-fit line 30 is determined.

[0043] Preferably, the metal-ceramic substrate is cut perpendicular to the main extension plane of the ceramic body, and the cross-section thus obtained is recorded (incident light / bright field) using an optical microscope, as will be described later.

[0044] In the first step, first, from the metal-ceramic substrate to be inspected, 100 mm 2 ~400 mm 2A cuboid sample blank having a rectangular bottom surface within the range is cut out by sawing perpendicularly to the plane extending by the main 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 supplied for inspection. Thus, this sample surface extends perpendicularly to the plane extending by the main 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 optionally provided bonding layer). The sample blank is first embedded in a mold containing 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 cabinet. 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.

[0045] In the 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 by different colors in the structured region.

[0046] Area A(BCD solid ) and A(BCD total ) are preferably determined in a routine manner, for example, using image evaluation software (e.g., IMS Client, Imagic).

[0047] Preferably, the term "in cross-section" as used herein refers to the total cross-section (preferably representative), particularly preferably at least 10 cross-sections, particularly very preferably 20 or fewer cross-sections, particularly 10 cross-sections. The cross-sections preferably extend parallel to each other and are equally spaced from each other. Thus, for the observed metal-ceramic substrate, the ratio A(BCD solid) / A(BCD total ) is preferably determined using the following procedure. 1. At least 10, particularly preferably 10, different cross-sections of the structured region are inspected. 2. For each of these cross-sections, the ratio A(BCD solid ) / A(BCD total ) is determined. 3. The ratios A(BCD solid ) / A(BCD total ) for each of these cross-sections are averaged to obtain the ratio A(BCD solid ) / A(BCD total ) for the observed metal-ceramic substrate.

[0048] According to a preferred embodiment, the ratio A(BCD solid ) / A(BCD total ) over at least 10 different cross-sections of at least one structured region of the metal layer, more preferably over 20 or fewer different cross-sections of at least one structured region of the metal layer, most preferably over 10 different cross-sections of at least one structured region of the metal layer, has a sample standard deviation SSD of 10% or less, more preferably 7% or less, particularly preferably 5% or less, and very particularly preferably 2% or less. The sample standard deviation SSD is determined using the following formula.

[0049]

Number

[0050]

Number

[0051] Surprisingly, it has been found that the metal-ceramic substrate having a geometric shape according to the present invention has improved thermal shock resistance as compared to the metal-ceramic substrate 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, the proportion of solid material in the metal layer at the boundary with the surface of the ceramic body has been found to be significantly lower in the metal-ceramic substrates according to the prior art as long as they have a contact area containing silver disposed on the metal layer.

[0052] 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 silver ions. Within the scope of the present invention, it has been observed that in this process, the silver ions mainly deposit on the surface of the metal-ceramic substrate, while the metal ions of the metal layer mainly elute in the region near the ceramic body (due to the structured portion on the edge side of the metal layer, the masking is washed away by the solution containing silver ions, so the effect cannot be prevented by the masking of the structured portion). This effect is particularly pronounced when the metal layer in the region adjacent to the ceramic body has already been structured and is 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 thermal shock resistance.

[0053] According to a preferred embodiment, the metal-ceramic substrate comprises a further (second) metal layer that is joined over a wide area to the ceramic body. The further metal layer is preferably joined over a wide area to an interface (preferably extending parallel to the main interface) on the side opposite to the main interface 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.

[0054] The metal-ceramic substrate according to the present invention can be used, in particular, in applications in electronics, especially in the field of power electronics.

[0055] Therefore, the present invention also provides an electronic component having the above-described metal-ceramic substrate.

[0056] According to a preferred embodiment, such an electronic module comprises a base plate. The base plate is preferably joined over a wide area 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 joined over a wide area to a silver-containing contact area arranged 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 joined to the first metal layer of the metal-ceramic substrate via a silver-containing contact area arranged on the metal layer, and the base plate is joined to the second metal layer of the metal-ceramic substrate.

[0057] The metal-ceramic substrate according to the present invention can be obtained by various manufacturing processes.

[0058] 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, and the method comprises: a) providing a metal-ceramic substrate, wherein the metal-ceramic substrate comprises: a1) a ceramic body; and a2) a metal layer widely joined to the ceramic body, the step; b) applying a first masking to the metal layer; c) depositing a silver-containing layer on the unmasked area of the metal layer to obtain a contact area containing silver; d) removing the first masking; e) applying a second masking to the metal layer; f) etching the unmasked area of the metal layer while maintaining the pattern; g) removing the second masking; including.

[0059] Therefore, in this method, it is preferable to first provide a metal-ceramic substrate. This metal-ceramic substrate has a ceramic body and a metal layer widely joined 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 integrally joined to the ceramic body as described above with respect to the metal-ceramic substrate.

[0060] In the method, it is preferable to apply a first masking to the metal layer. The first masking serves to protect the masked areas of the metal layer from the deposition of the silver-containing layer in subsequent steps. This ensures 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 is not 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, foil (or dry film) or liquid, and optionally, printed or sprayed on specific 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 metal layer of the metal-ceramic substrate and then exposed in the areas to be masked to obtain the first masking. Then, the unexposed areas of the photosensitive film can be removed by conventional methods (e.g., using a sodium carbonate solution).

[0061] After the application of the first masking, it is preferable to deposit a silver-containing layer on the unmasked areas of the metal layer to obtain 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, without current, or chemically. Chemical deposition by applying a silver-containing solution involving charge exchange between metals is preferred, where 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 - 1.5 g / l, particularly preferably in the range of 0.6 - 1.4 g / l, and very particularly preferably in the range of 0.8 - 1.2 g / l.

[0062] Preferably, after depositing a silver-containing layer on the unmasked region of the metal layer to obtain a contact region containing silver, the first masking is removed. The first masking can be removed by standard methods. 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 masking.

[0063] After removing the first masking, it is preferable to apply a second masking to the metal layer. The second masking serves to protect the masked region of the metal layer of the metal-ceramic substrate from etching in subsequent steps. Thereby, it is ensured that only the unmasked and patterned regions of the metal layer of the metal-ceramic substrate are accessible for etching. Thus, the masking is made so that etching does not occur in the masked region of the metal layer. According to a preferred embodiment, the second masking is applied to the region of the metal-ceramic substrate where the first masking 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 foil (or dry film) or liquid, and optionally, printed or sprayed onto specific regions 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 surface of the metal-ceramic substrate partially covered with silver, and then exposed in the regions to be masked to obtain the second masking. Subsequently, the unexposed regions of the photosensitive film can be removed by conventional methods (e.g., using a sodium carbonate solution).

[0064] After applying the second masking to the metal layer, it is preferable to etch the unmasked regions of the metal layer to obtain a structured portion. The etching is preferably performed by a standard and skilled method. Thus, 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 FeCl3 etching solution and CuCl2 etching solution. If necessary, for example, an additional etching solution can be used to structure the unmasked regions of the optionally included bonding 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) as well as hydrogen peroxide and / or ammonium persulfate.

[0065] Preferably, after etching the unmasked regions of the metal layer while maintaining the structured portion, the second masking is removed. The second masking 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 second masking.

[0066] The method described herein enables the obtaining of a metal-ceramic substrate provided with a structured portion and a contact region containing silver. By creating a contact region containing silver, chips can be more easily bonded to the metal-ceramic substrate using common methods such as sintering or soldering. The metal-ceramic substrate thus obtained is characterized by particularly high resistance to thermal shock.

[0067] Exemplary Embodiments The present invention will be described in more detail below using exemplary embodiments, but should not be understood as limiting.

Examples

[0068] As an example, the AMB (active metal brazing) method was used to bond copper layers with dimensions of 170×132×0.3 mm to both sides of a ceramic body made of silicon nitride ceramic with dimensions of 177.8×139×0.32 mm, and a metal-ceramic substrate was used. This copper-ceramic substrate was first cleaned after production.

[0069] Next, a hot roll laminator was used to apply a photosensitive film to both copper layers of the copper-ceramic substrate. In order to cure the polymer contained in the photosensitive film to obtain the first masking, the photosensitive film was exposed at 30 mJ / cm 2 in each of the areas to be masked. After that, the unexposed areas of the photosensitive film were removed wet chemically using a sodium carbonate solution (concentration = 10 g / l). After applying the first masking, the copper-ceramic substrate was rinsed and cleaned. After that, 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 provided with the first masking 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. Next, in a stripping system, the first masking was removed using a 2.5% sodium hydroxide solution.

[0070] After that, a hot roll laminator was used to apply a photosensitive film to both copper layers of the copper-ceramic substrate each having a silver-containing contact area. In order to cure the polymer contained in the photosensitive film to obtain the second masking, the photosensitive film was exposed at 30 mJ / cm 2It was exposed. Next, using a sodium carbonate solution (concentration = 10 g / l), the unexposed areas of the photosensitive film were removed wet-chemically. After applying the second masking, the copper-ceramic substrate was rinsed and washed again. Thereafter, the unmasked areas of the copper layer of the copper-ceramic substrate provided with the silver-containing contact regions were etched wet-chemically. For this purpose, in an etching system, a copper 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 spraying pressure of 2.8 bar. By the etching, material was removed from the unmasked areas of the copper layer of the copper-ceramic substrate. Next, the metal-ceramic substrate was rinsed. Next, the unmasked areas of the bonding layer contained in the metal-ceramic substrate were also etched wet-chemically. For this purpose, in the etching system, an etching solution containing ammonium fluoride, fluoroboric acid and hydrogen peroxide was sprayed again onto the metal-ceramic substrate. Next, the copper-ceramic substrate was rinsed and dried. Next, in a stripping system, the second masking was removed using a 2.5% sodium hydroxide solution.

[0071] 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.

[0072] Comparative example: The comparative example was carried out in the same manner as the example, except that the order of (i) depositing a silver-containing layer on the unmasked areas of the copper layer to obtain a contact region containing silver and (ii) etching the unmasked areas of the copper layer to obtain a structured part was reversed.

[0073] For the comparative example, a metal-ceramic substrate similar to the example in which a copper layer having dimensions of 170 × 132 × 0.3 mm was bonded to both sides of a silicon nitride ceramic body having dimensions of 177.8 × 139 × 0.32 mm by an AMB (active metal brazing) process was used. This copper-ceramic substrate was first washed after production.

[0074] 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 the first masking, the photosensitive film was exposed at 30 mJ / cm 2 in each of the areas to be masked. Thereafter, the unexposed areas of the photosensitive film were removed wet chemically using a sodium carbonate solution (concentration = 10 g / l). After applying the first masking, the copper-ceramic substrate was rinsed and cleaned. Thereafter, the unmasked areas of the copper layer of the copper-ceramic substrate were etched wet chemically. 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. Next, the metal-ceramic substrate was rinsed. Next, the unmasked areas of the bonding layer contained in the metal-ceramic substrate were also etched wet chemically. 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. Next, the copper-ceramic substrate was rinsed and dried. Next, in a stripping system, the second masking was removed using a 2.5% sodium hydroxide solution.

[0075] 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 the second masking, the photosensitive film was exposed at 30 mJ / cm 2It was exposed. Then, using a sodium carbonate solution (concentration = 10 g / l), the unexposed areas of the photosensitive film were removed wet-chemically. After applying the second masking, the copper-ceramic substrate was rinsed and washed again. Thereafter, a silver-containing contact area was deposited on the unmasked area of the copper layer of the copper-ceramic substrate. For this purpose, the copper-ceramic substrate provided with the second masking 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. Then, in the stripping system, the second masking was removed using a 2.5% sodium hydroxide solution.

[0076] 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.

[0077] Evaluation: The ratio A(BCD solid ) / A(BCD total ) was determined for the metal-ceramic substrates obtained in the examples and comparative examples. For this purpose, as described in this specification, 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, C, and D were determined in the cross-section. Then, the ratio A(BCD solid ) / A(BCD 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 investigated, and the ratio A(BCD solid ) / A(BCD total ) was determined for each of these cross-sections, and the average value of the ratio A(BCD solid ) / A(BCD total ) was calculated for each of these cross-sections to obtain the ratio A(BCD solid ) / A(BCD total) was obtained. Further, the standard deviation SSD was determined.

[0078] FIG. 3 shows an example of an optical microscope image of a cross-section of the structured region of the metal-ceramic substrate according to the example, and FIG. 4 shows an example of an optical microscope image of a cross-section of the structured region of the metal-ceramic substrate according to the comparative example.

[0079] The results are shown in Table 1.

[0080] [Table 1]

[0081] The thermal shock resistance of the metal-ceramic substrate was tested. For this purpose, a thermal shock resistance test was conducted.

[0082] Thermal shock resistance test: In the preparation for 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 (e.g., 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 low-temperature liquid (temperature -65°C, Galden Do2TS) and a high-temperature liquid (temperature +150°C, Galden Do2TS) for 5 minutes each in a cycle chamber (ESPEC TSB-2151). An ultrasonic microscope (PVA Tepla SAM300) was used to recheck 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 reinspect 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 (e.g., cracks) appeared as white discoloration in the ultrasonic images.

[0083] The results are shown in Table 2.

[0084] [Table 2]

[0085] 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. [Explanation of Reference Signs]

[0086] 1 Metal-ceramic substrate 2 Main extension plane 4 Structured region 8 Contact region 10 Ceramic body 15 Main boundary surface 20 Metal layer 22 Recess 24 Metal main surface 40 Contour line 50 Solid material 200 Further metal layer

Claims

1. A metal-ceramic substrate, comprising: a) a ceramic body having a main extension plane; and b) a metal layer widely joined to the ceramic body, the metal layer comprising a structured region that: (i) partially contains a solid material; and (ii) partially contains a non-solid material; and c) a contact region containing silver disposed on the metal layer. In the metal-ceramic substrate, the structured region has a geometric shape that satisfies the following requirements in a cross-section perpendicular to the main extension plane and passing through the metal-ceramic substrate, A(BCD ｓｏｌｉｄ ) / A(BCD ｔｏｔａｌ )>70% wherein A(BCD ｔｏｔａｌ ) is the total area of the triangle depicted by points B, C, and D, A(BCD ｓｏｌｉｄ ) is the area of the triangle depicted by points B, C, and D that is occupied by the solid material, points B, C, and D 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. On the perpendicular to the best-fit line, at a distance of 150 μm from the best-fit line, point A where the perpendicular to the best-fit line intersects the contour line is determined; 4. On the perpendicular to the best-fit line, at a distance of 80 μm from the best-fit line, point B where the perpendicular to the best-fit line intersects the contour line is determined; 5. On the straight line passing through points A and B, point C where the straight line intersects the best-fit line is determined; 6. On the perpendicular passing through point B with respect to the best-fit line, point D where the perpendicular intersects the best-fit line is determined. 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 material.

6. Satisfying the following requirements, that is, A(BCD ｓｏｌｉｄ ) / A(BCD ｔｏｔａｌ ) > 95% 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 A(BCD ｓｏｌｉｄ ) / A(BCD ｔｏｔａｌ ) over at least 10 different cross-sections of the structured region of the metal layer is 10% or less, characterized in that the metal-ceramic substrate according to any one of claims 1 to 6.

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

Images