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 comprising a metal-ceramic substrate.

[0002] Metal-ceramic substrates play a crucial role in the field of power electronics. They are essential elements in constructing electronic components, ensuring the rapid dissipation of large amounts of heat during the operation of these components. Metal-ceramic substrates typically consist of a ceramic layer and a metal layer bonded to the ceramic layer.

[0003] Several methods for bonding a metal layer to a ceramic layer are known from the prior art. In the so-called DCB ("direct copper bonding") method, copper is reacted with a reactive gas (usually oxygen) to form a copper compound (usually copper oxide) with a lower melting point than copper on the surface of the copper foil. When the copper foil thus treated is applied to a ceramic body and the composite is fired, the copper compound melts, wetting the surface of the ceramic body and achieving a stable, integral bond 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] Alternatively, metal foil can be bonded to a ceramic body at a temperature of approximately 650-1000°C, using a specific solder containing a metal (usually silver) with a melting point of at least 700°C and an active metal. The active metal's role is to react with the ceramic material, thus facilitating the bonding of the ceramic material to the rest of the solder and forming a reaction layer, while the metal with a melting point of at least 700°C helps to bond this reaction layer to the metal foil. For example, Japanese Patent No. 4812985(B2) proposes bonding copper foil to a ceramic body using a solder containing 50-89% by weight of silver, as well as copper, bismuth, and an active metal. This method ensures secure attachment of the copper foil to the ceramic body. Alternatively, metal foil can be bonded to a ceramic body using silver-free solder. 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 techniques are proposed, for example, in German Patent Application Publication No. 102017114893(A1). This technique essentially results in a new, independent class of compounds because the base of the solder used is formed by a different metal (copper instead of silver), leading to changes in material properties and adaptation to other solder components and modified bonding conditions.

[0005] When constructing electronic components, chips are typically mounted on a metal-ceramic substrate. To mount chips on a metal-ceramic substrate, it is usually necessary to provide silver-containing contact areas in the region of the substrate where the chip will be mounted. By providing silver-containing contact areas, the chip can be more easily bonded to the metal-ceramic substrate using common methods such as sintering or soldering. To create the contact areas, the metal-ceramic substrate is usually first treated with an etching solution in several areas to form the desired structured regions. Then, the contact areas are provided by partially applying a silver-containing coating to the surface of the structured metal-ceramic substrate.

[0006] Metal-ceramic substrates manufactured in this manner are typically subjected to large temperature fluctuations during operation as part of electronic components. During periods of interruption, depending on the environment, temperatures can drop to, for example, below -20°C, while the temperature of the metal-ceramic substrate can easily rise to over 150°C during operation. The metal-ceramic substrate is regularly exposed to these temperature differences. Due to the different coefficients of thermal expansion of metals and ceramics, repeated temperature changes can cause the metal layer to delaminate (exfoliate) from the ceramic body, potentially degrading performance. Therefore, high thermal shock resistance is a crucial criterion for the suitability of metal-ceramic substrates in electronics, particularly power electronics applications.

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

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

[0009] This objective is achieved by the metal-ceramic substrate of claim 1. Therefore, the present invention relates to a metal-ceramic substrate, a) A ceramic body having a main extended plane, b) A metal layer bonded over a wide area to a ceramic body, (i) Partially containing solid material, (ii) A metal layer having a structured region that partially contains a non-solid material, c) A metal-ceramic substrate comprising a contact region containing silver disposed in a metal layer, 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: A(BCD solid ) / A(BCD total )>70% During the ceremony, A(BCD total ) is the total area of ​​the triangle drawn by points B, C, and D. A(BCD solid) is the area occupied by the solid material in the triangle drawn by points B, C and D, Points B, C and D are determined as follows, that is, 1. A best fit line between the ceramic body and the metal layer is determined, 2. A 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 is determined at which the perpendicular to the best fit line intersects the contour line, 4. On the perpendicular to the best fit line, at a distance of 80 µm from the best fit line, point B is determined at which the perpendicular to the best fit line intersects the contour line, 5. On the straight line passing through points A and B, point C is determined at which the straight line intersects the best fit line, 6. On the perpendicular passing through point B to the best fit line, point D is determined at which the perpendicular intersects the best fit line, A metal-ceramic substrate characterized by the above is provided.

[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 of 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 herein referred to as the boundary surface having the largest surface area that is extensively bonded to the metal layer. The main boundary surface is preferably located in the main extension plane or extends parallel to the main extension plane. Accordingly, the main extension plane of the ceramic body is understood to be preferably a plane extending parallel to the main boundary surface of the ceramic body or a plane surrounding the same.

[0013] The ceramic material 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 further 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). In yet another very preferred embodiment, the ceramic body comprises (1) at least one element selected from the group consisting of silicon and aluminum, (2) at least one element selected from the group consisting of oxygen and nitrogen, optionally (3) at least one element selected from the group consisting of (3a) rare earth metals, (3b) metals of group 2 elements of the periodic table, (3c) zirconium, (3d) copper, (3e) molybdenum, and (3f) silicon, and optionally (4) unavoidable impurities. In yet another very 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 bonded over a wide area of ​​a ceramic body, wherein the metal layer has structured regions that (i) partially contain a solid material and (ii) partially contain a non-solid material.

[0016] The metal layer is preferably integrally bonded to the ceramic body. In a preferred embodiment, the metal layer is bonded to the ceramic body by a DCB (direct copper bonding) method. In a further preferred embodiment, the metal layer is bonded to the ceramic body by a brazing process. The brazing process can be, for example, an AMB (active metal brazing) method using, preferably, a silver-free brazing alloy (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 (silver content is, for example, at least 50 weight percent based on the solid content of the brazing alloy). Thus, the metal layer may have a bonding layer in contact with the ceramic body. The bonding layer can be, for example, a solder layer (particularly a brazing layer) or a diffusion layer.

[0017] The metal layer is bonded to the ceramic body over a wide area. Therefore, the metal layer is preferably bonded over a wide area of ​​the main interface of the ceramic body. The metal layer is preferably not bonded to the entire main interface of the ceramic body. In particular, the main interface of the ceramic body can be larger than the surface of the metal layer bonded to it. In these cases, the main interface of the ceramic body protrudes. In addition, the metal layer is preferably structured. Structured areas are understood to mean recesses in the metal layer, preferably for separating individual parts of the metal layer from each other and thus electrically insulating them. Such structured areas are usually created using etching techniques.

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

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

[0020] The structured region comprises a region containing solid materials and a region containing non-solid materials.

[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 the bonding layer, if present, e.g., AMB), (ii) the metal of the contact region (particularly silver), and (iii) the material of the ceramic body. Therefore, the solid material preferably includes (i) the metal of the metal layer (optionally including the bonding layer) and optionally (ii) the metal of the contact region (particularly silver) and / or (iii) the material of the ceramic body.

[0022] In a preferred embodiment, the structured region between the main metal surface (excluding the contact area) and the main interface of the ceramic body does not contain the main metal of the contact area, particularly silver. In a further preferred embodiment, the solid material of the structured region between the main metal surface (excluding the contact area) and the main interface of the ceramic body does not contain deposits of the main metal of the contact area, particularly silver. Therefore, in a particularly preferred embodiment, the solid material of the structured region between the main metal surface (excluding the contact area) and the main interface of the ceramic body does not have a layer made of the main metal of the contact area, particularly silver. The main metal of the contact area is preferably the metal having the highest weight percentage in the contact area.

[0023] Regions containing non-solid materials preferably contain gaseous materials. Therefore, non-solid materials preferably contain gaseous materials. The non-solid material is preferably a gaseous material that fills the recesses in the metal layer. This gaseous material usually originates from the ambient atmosphere. Therefore, 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 interface of the ceramic body to the main metal surface in a direction perpendicular to the main interface of the ceramic body. The recess forms a channel which is preferably filled with a non-solid material to at least 50 volume percent, more preferably at least 80 volume percent, even more preferably at least 90 volume percent, particularly preferably at least 95 volume percent, particularly very preferably at least 99 volume percent, and especially completely.

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

[0026] In a preferred embodiment, the metal layer is produced by integrally bonding a copper foil (preferably a high-purity copper foil) to a ceramic body. In a preferred embodiment, the bonding can be carried out by DCB (direct copper bonding) or brazing. The brazing process may be, for example, an AMB (active metal brazing) method using a silver-free brazing alloy (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 (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 include, in addition to copper derived from the copper foil, metal from the bonding layer, particularly metal from the solder layer (e.g., the brazing layer) or the diffusion layer.

[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 most preferably in the range of 0.05 to 3 mm.

[0028] The metal-ceramic substrate according to the present invention has contact regions containing silver disposed on a metal layer. The contact regions preferably serve to facilitate the bonding of a semiconductor to the metal layer. The semiconductor is preferably bonded to the metal layer by sintering, soldering, or bonding. In particular, since the attachment of the semiconductor to the metal of the metal layer of the metal-ceramic substrate is not easily possible, the metal layer is preferably provided with contact regions. The contact regions are 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 relative to the weight of the silver alloy. Preferably, contact regions are provided on the metal layer of the metal-ceramic substrate at all locations where a semiconductor will be later mounted on the metal-ceramic substrate. The contact regions can be formed on the metal layer of the metal-ceramic substrate using various techniques. For example, contact regions can be provided by deposition. Deposition can be, for example, physical deposition or chemical deposition. For example, vapor deposition can be considered as physical deposition. Preferred methods of vapor deposition are, in particular, electron beam deposition, laser beam deposition, arc discharge deposition, or cathode sputtering. In chemical deposition, contact areas are preferably created by applying a composition containing silver or a silver precursor to a metal layer. For example, a silver-containing composition can be calcined to create a sintered bond between the silver contained in the composition and the metal of the metal layer. For example, a composition containing a silver precursor may be subjected to a treatment that releases silver and allows for the adsorption of silver onto 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 silver compounds to create contact areas on a metal layer of a 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 that is occupied by the solid material, According to a preferred embodiment, in a cross-section of the structured region of the metal-ceramic substrate passing through the metal-ceramic substrate perpendicularly to the main extension plane, the ratio A(BCD solid ) / A(BCD total )>75%, more preferably >80%, still more preferably >85%, particularly preferably >90%, and very particularly preferably >95%.

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

[0031] In order to determine the triangle drawn by points B, C and D, a cross-section of the structured region of the metal-ceramic substrate is observed. The cross-section extends perpendicularly to the main extension plane of the ceramic body. Preferably, the observation of the cross-section can be performed by cutting the metal-ceramic substrate perpendicularly to the main extension plane of the ceramic body, and photographing the cross-section thus obtained using a scanning electron microscope.

[0032] Points B, C and D of the triangle can be determined in the cross-section as described below. For explanation, reference is made to FIGS. 1 and 2 as examples. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] [Figure 1] FIG. 1 shows a schematic diagram of a general metal-ceramic substrate. [Figure 2] Figure 2 shows a portion of the cross-section through the metal-ceramic substrate according to the present invention.

[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 interface 15. The metal-ceramic substrate 1 comprises a metal layer 20 bonded over a wide area to the main interface 15 of the ceramic body 10. In the embodiment shown in Figure 1, the metal-ceramic substrate 1 further comprises a further metal layer 200 bonded over a wide area to the ceramic body 10. The metal layer 20 has a contact region 8 containing silver. The metal layer 20 comprises a structured region, which is formed by recesses 22 in the metal layer 20. The recesses 22 contain a non-solid material. The structured region 4 partially comprises the metal layer 20 and the recesses 22. Thus, the structured region 4 partially comprises a solid material 50 formed by the metal of the metal layer 20 and a non-solid material (e.g., a gaseous material) filling the recesses 22. The gaseous material is typically ambient air. The solid material 50 is separated from the non-solid material of the recess 22 by the contour line 40. The metal layer 20 has a main metal surface 24 parallel to the main ceramic interface 15 on its upper surface opposite to the main ceramic interface 15. This main metal surface 24 contains the metal of the metal layer 20 which is interrupted by the recess 22 in the structured region. The recess 22 extends from the main ceramic interface 15 to the main metal surface 24 in a direction perpendicular to the main ceramic interface 15 and preferably forms a channel that is completely or largely filled with the non-solid material.

[0035] In a portion of the cross-section passing through the metal-ceramic substrate according to the present invention shown in Figure 2, a portion of the structured region can be seen. The region of the ceramic body 10 that is bonded over a wide area 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.

[0036] The determination of points B and C on 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 is determined that separates the solid material 50 from the non-solid material of the recess 22. The solid material 50 is determined visually, and this is typically the material of the metal layer 20. The non-solid material is also determined visually. The non-solid material is typically a gaseous material that fills the structured portion as the recess 22 of the metal layer 20.

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

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

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

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

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

[0044] In the first step, first, from the metal-ceramic substrate to be inspected, 100 mm 2 ~400mm 2A rectangular sample blank with a rectangular base is cut out by sawing perpendicular to the plane extending from the main metal surface of the metal layer of the metal-ceramic substrate using a low-speed diamond saw blade and lubricant (Exakt). Thus, the sample blank has a sample surface supplied for inspection. Therefore, this sample surface extends perpendicular to the plane extending from the main metal surface of the metal layer of the metal-ceramic substrate before sawing. Thus, it has a portion of the ceramic body and a portion of the metal layer (including an optionally provided bonding layer). The sample blank is first embedded in a mold containing low-shrinkage epoxy resin (Caldo-Fix, Struers), with the sample surface oriented perpendicular to the mold wall. The epoxy resin is then cured at 75°C in a drying rack. After curing, the sample surface of the sample blank is mechanically polished in an automated polishing machine (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 200x magnification using an optical microscope (Leica, DM6000M, incident light / brightfield), and this region partially contains solid material and partially contains non-solid material. The solid and non-solid materials can be clearly distinguished by the different colors in the structured region.

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

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

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

[0049]

number

[0050]

number

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

[0052] While not bound by the explanation, this may be due to the fact that, in the prior art, manufactured metal-ceramic substrates are typically first structured and then silver-plated on the surface to create contact areas. Silver plating is usually performed by immersing the structured metal-ceramic substrate in a bath containing a solution containing silver ions. Metal ions are electrochemically dissolved from the metal layer of the metal-ceramic substrate and replaced by silver ions. Within the scope of the present invention, in this process, it has been observed that silver ions mainly deposit on the surface of the metal-ceramic substrate, but metal ions from the metal layer mainly dissolve into areas near the ceramic body (an effect that cannot be prevented by masking of the structured portion, as the masking is washed away by the silver ion-containing solution due to the structured portion at the edge of the metal layer). This effect is particularly pronounced when the metal layer in areas adjacent to the ceramic body is already structured and therefore no longer homogeneous. This results in the removal of solid material from the metal foil, especially the metal of the metal foil, in areas close to the ceramic body, thus creating a weak point for peeling of the metal layer from the ceramic body, which adversely affects 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 metal layer from peeling off from the ceramic body and achieving improved thermal shock resistance.

[0053] In a preferred embodiment, the metal-ceramic substrate comprises a further (second) metal layer bonded over a wide area of ​​the ceramic body. The further metal layer is preferably bonded over a wide area of ​​the interface opposite to the main interface of the ceramic (preferably extending parallel to the main interface). The further (second) metal layer may have the same properties as the (first) metal layer, or its properties may differ from those of the (first) metal layer. The properties of the further (second) metal layer are described above.

[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 electronic components having the metal-ceramic substrate described above.

[0056] According to a preferred embodiment, such an electronic module comprises a base plate, which is preferably extensively bonded to a metal layer of a 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, which is preferably extensively bonded to a contact area 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 preferably on the opposite side of the second metal layer), a base plate, and at least one chip, wherein at least one chip is bonded to the first metal layer of the metal-ceramic substrate via a contact area containing silver disposed on the metal layer, and the base plate is bonded 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 for manufacturing a metal-ceramic substrate having a structured portion and a contact area containing silver, the method is a) A step of providing a metal-ceramic substrate, wherein the metal-ceramic substrate is a1) Ceramic body and, a2) A step comprising a metal layer bonded over a wide area to a ceramic body, b) The step of applying a first masking to the metal layer, c) A step of depositing a silver-containing layer in an unmasked area of ​​the metal layer to obtain a contact area containing silver, d) The step of removing the first masking, e) The step of applying a second mask to the metal layer, f) A step of etching the unmasked areas of the metal layer while maintaining the pattern, g) The step of removing the second masking, Includes.

[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 bonded over a wide area of ​​the ceramic body. The metal-ceramic substrate can be a standard metal-ceramic substrate. The ceramic body and the metal layer may have the compositions described above with respect to the metal-ceramic substrate. The metal layer can preferably be bonded integrally to the ceramic body as described above with respect to the metal-ceramic substrate.

[0060] In this 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 in the unmasked areas of the metal layer of the metal-ceramic substrate. Therefore, the masking is designed so that the silver-containing layer is not deposited in 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 a positive mask. The masking can be made, for example, by foil (or dry film) or liquid and optionally printed or sprayed onto a specific area 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 (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 area to be masked in order to obtain the first masking. Next, the unexposed areas of the photosensitive film can be removed using conventional methods (for example, using a sodium carbonate solution).

[0061] After the first masking is applied, it is preferable to deposit a silver-containing layer in the unmasked areas of the metal layer to obtain a silver-containing contact area. The silver-containing layer is preferably made of silver or a silver alloy, and is particularly preferably made of silver. The silver-containing layer is preferably deposited by conventional methods. The silver-containing layer can be deposited, for example, electrochemically, without current, or chemically. Chemical deposition by applying a silver-containing solution with charge exchange between metals is preferred, where the metal in the metal layer partially dissolves while the silver in the solution is deposited. According to a preferred embodiment, the silver-containing solution contains a silver salt, particularly preferably silver nitrate. According to a preferred embodiment, the silver-containing solution is an acidic solution of silver nitrate, and is 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 particularly very preferably in the range of 0.8 to 1.2 g / l.

[0062] Preferably, a silver-containing layer is deposited in an unmasked area of ​​the metal layer to obtain a silver-containing contact area, after which 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., a 2.5% sodium hydroxide solution) to remove the first masking.

[0063] It is preferable to apply a second masking to the metal layer after removing the first masking. The second masking serves to protect the masked areas of the metal layer of the metal-ceramic substrate from etching in subsequent steps. This ensures that only the unmasked and intended-to-pattern areas of the metal layer of the metal-ceramic substrate are accessible for etching. Thus, the masking is designed to prevent etching from occurring in the masked areas of the metal layer. According to a preferred embodiment, the second masking is applied to areas of the metal-ceramic substrate to which 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 a positive mask. The masking can be made, for example, by foil (or dry film) or liquid and optionally printed or sprayed onto 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 a partially silver-covered surface of a metal-ceramic substrate and then exposed in the area to be masked in order to obtain a second mask. The unexposed areas of the photosensitive film can then be removed by conventional methods (e.g., using a sodium carbonate solution).

[0064] After applying a second masking to the metal layer, it is preferable to etch the unmasked areas of the metal layer to obtain the structured areas. Etching is preferably carried out by a standard, skilled method. Therefore, etching is preferably carried out using a standard etching solution. According to a preferred embodiment, the etching solution is selected from the group consisting of FeCl3 etching solutions and CuCl2 etching solutions. If necessary, additional etching solutions can be used, for example, to structure the unmasked areas of the optionally included bonding layer. According to a preferred embodiment, further etching solutions can be selected from the group consisting of etching solutions containing hydrogen peroxide and etching solutions containing ammonium persulfate. For example, further etching solutions may be etching solutions containing ammonium fluoride and fluoroboric acid (e.g., HBF4) and hydrogen peroxide and / or ammonium persulfate.

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

[0066] The method described herein makes it possible to obtain a metal-ceramic substrate having a structured portion and a contact area containing silver. By creating a contact area 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, a metal-ceramic substrate was used in which a copper layer measuring 170 × 132 × 0.3 mm was bonded to both sides of a silicon nitride ceramic body measuring 177.8 × 139 × 0.32 mm using the AMB (Active Metal Brazing) method. This copper-ceramic substrate was first cleaned after manufacturing.

[0069] Next, a photosensitive film was applied to both the copper layers of the copper-ceramic substrate using a hot roll laminator. To cure the polymer contained in the photosensitive film and obtain the first masking, a photosensitive film of 30 mJ / cm² was applied to each of the areas to be masked. 2 The substrate was exposed to light. After this, the unexposed areas of the photosensitive film were wet chemically removed using a sodium carbonate solution (concentration = 10 g / l). After applying the first masking, the copper-ceramic substrate was rinsed and washed. Subsequently, 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 first masking was first pre-treated 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 any residue. Then, the first masking was removed using a 2.5% sodium hydroxide solution in a peeling system.

[0070] Subsequently, 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. To cure the polymer contained in the photosensitive film and obtain a second mask, the photosensitive film was treated with 30 mJ / cm² of photosensitive film in each of the areas to be masked. 2The substrate was exposed to light. Then, the unexposed areas of the photosensitive film were wet-chemically removed using a sodium carbonate solution (concentration = 10 g / l). After applying the second masking, the copper-ceramic substrate was rinsed and washed again. After this, the unmasked areas of the copper layer of the copper-ceramic substrate, where the silver-containing contact area was provided, were wet-chemically etched. For this purpose, a copper hydrochloride solution containing hydrogen peroxide (copper ion content = 160 g / l) was sprayed onto the copper-ceramic substrate in an etching system. Etching was performed at a temperature of 50°C and a spray pressure of 2.8 bar. Etching removed material 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 bonding layer contained in the metal-ceramic substrate were also wet-chemically etched. For this purpose, an etching solution containing ammonium fluoride, fluoroboric acid, and hydrogen peroxide was sprayed onto the metal-ceramic substrate again in an etching system. Then, the copper-ceramic substrate was rinsed and dried. Next, in the peeling system, the second masking layer was removed using a 2.5% sodium hydroxide solution.

[0071] The obtained copper-ceramic substrate could be laser-cut into individual parts with dimensions (20.5 × 17.0 mm), which could then be used for further investigation and the manufacture of electronic components.

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

[0073] For a comparative example, a metal-ceramic substrate similar to that in the example was used, in which a copper layer measuring 170 × 132 × 0.3 mm was bonded to both sides of a silicon nitride ceramic body measuring 177.8 × 139 × 0.32 mm using an AMB (Active Metal Brazing) process. This copper-ceramic substrate was first cleaned after manufacturing.

[0074] Next, a photosensitive film was applied to both the copper layers of the copper-ceramic substrate using a hot roll laminator. To cure the polymer contained in the photosensitive film and obtain the first masking, a photosensitive film of 30 mJ / cm² was applied to each of the areas to be masked. 2 The substrate was exposed to light. After this, the unexposed areas of the photosensitive film were wet chemically removed using a sodium carbonate solution (concentration = 10 g / l). After applying the first masking, the copper-ceramic substrate was rinsed and cleaned. Then, the unmasked areas of the copper layer of the copper-ceramic substrate were wet chemically etched. For this purpose, a copper hydrochloride solution containing hydrogen peroxide (copper ion content = 160 g / l) was sprayed onto the copper-ceramic substrate in an etching system. Etching was performed at a temperature of 50°C and a spray pressure of 2.8 bar. Etching removed material from the unmasked areas of the copper layer of the copper-ceramic substrate. Next, the metal-ceramic substrate was rinsed. Then, the unmasked areas of the bonding layer contained in the metal-ceramic substrate were also wet chemically etched. For this purpose, an etching solution containing ammonium fluoride, fluoroboric acid, and hydrogen peroxide was sprayed onto the metal-ceramic substrate again in an etching system. Next, the copper-ceramic substrate was rinsed and dried. Next, in the peeling system, the second masking layer was removed using a 2.5% sodium hydroxide solution.

[0075] Next, a photosensitive film was applied to both etched surfaces of the copper-ceramic substrate using a hot roll laminator. To cure the polymer contained in the photosensitive film and obtain a second mask, the photosensitive film was treated with 30 mJ / cm² of lamination in each area to be masked. 2The substrate was exposed to light. Then, the unexposed areas of the photosensitive film were wet-chemically removed using a sodium carbonate solution (concentration = 10 g / l). After applying the second masking, the copper-ceramic substrate was rinsed and washed again. After this, 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 masking was first pre-treated 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 any residue. Then, the second masking was removed using a 2.5% sodium hydroxide solution in a peeling system.

[0076] The obtained copper-ceramic substrate could be laser-cut into individual parts with dimensions (20.5 × 17.0 mm), which could then be used for further investigation and the manufacture of electronic components.

[0077] evaluation: The ratio A(BCD) of the metal-ceramic substrates obtained in the examples and comparative examples. solid ) / A(BCD total The ratio A(BCD) was determined. 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 resulting cross-sections were taken using an optical microscope. Points A, B, C, and D were determined in the cross-sections. Then, the ratio A(BCD) for each of the metal-ceramic substrates was determined. solid ) / A(BCD total To this end, we investigated 10 different cross-sections of the structured region in the metal layer of the relevant metal-ceramic substrate, and determined the ratio A(BCD) for each of these cross-sections. solid ) / A(BCD total ) and calculate the ratio A(BCD) for each of these cross-sections. solid ) / A(BCD total Calculate the average value of the corresponding metal-ceramic substrate and the ratio A(BCD) for that substrate. solid ) / A(BCD totalWe obtained [result]. Furthermore, we calculated the standard deviation SSD.

[0078] Figure 3 shows an example of an optical microscope image of a cross-section of the structured region of a metal-ceramic substrate according to the example, and Figure 4 shows an example of an optical microscope image of a cross-section of the structured region of a 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 metal-ceramic substrates was tested. For this purpose, thermal shock resistance tests were conducted.

[0082] Thermal shock resistance test: In preparation for the thermal shock resistance test, the metal-ceramic substrate was first checked for its integrity using an ultrasonic microscope (PVA Tepla SAM300). Only metal-ceramic substrates that did not exhibit delamination between the ceramic body and the metal layer, or other deformations (e.g., cracks) that could lead to delamination of the metal layer from the ceramic body, were used for the test. To test 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). Delamination and other deformations of the metal-ceramic substrate were re-examined every 1000 cycles using an ultrasonic microscope (PVA Tepla SAM300). The test was terminated after 3000 cycles. Subsequently, delamination and other deformations of the metal-ceramic substrate were re-examined using an ultrasonic microscope (PVA Tepla SAM300). The condition of each metal-ceramic substrate after the thermal shock resistance test was compared with the condition of the metal-ceramic substrate before the thermal shock resistance test to assess delamination and other deformations. Delamination and other deformations (e.g., cracks) appeared as white discoloration in the ultrasound images.

[0083] The results are shown in Table 2.

[0084] [Table 2]

[0085] The results show that, in terms of 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 symbols]

[0086] 1. Metal-ceramic substrate 2 Main extension plane 4 Structured area 8 Contact area 10 Ceramic body 15 Main interface 20 metal layer 22 recess 24 Metal main surface 40 Outline 50 solid materials 200 Further metal layer

Claims

1. A metal-ceramic substrate, a) A ceramic body having a main interface, b) A metal layer bonded over a wide area of ​​the ceramic body, A structured region including a recess, comprising a metal layer having the structured region which (i) partially contains a solid material and (ii) partially contains a non-solid material, c) A metal-ceramic substrate comprising a contact region containing silver disposed on the metal layer, The main interface is the interface having the largest surface area that is joined to the metal layer. 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 interface: A(BCD ｓｏｌｉｄ ) / A(BCD ｔｏｔａｌ )>70% During the ceremony, 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 that is occupied by the solid material. Points B, C, and D are determined as follows, that is, 1. The best fit line, defined as the boundary between the ceramic body and the metal layer observed in the cross-section, is determined.

2. The contour line separating the solid material from the non-solid material is determined.

3. Point A is determined where the perpendicular to the best-fit line intersects the contour line at a distance of 150 μm from the best-fit line.

4. A point B is determined on the perpendicular line to the best-fit line, at a distance of 80 μm from the best-fit line, where the perpendicular line to the best-fit line intersects the contour line.

5. A point C is determined on a straight line passing through points A and B, where the straight line intersects the best-fitting line.

6. A point D is determined on the perpendicular line passing through point B to the best-fit line, where the perpendicular line intersects the best-fit line. The ceramic material of the aforementioned ceramic body is selected from the group consisting of aluminum nitride ceramic, silicon nitride ceramic, and aluminum oxide ceramic. The aforementioned metal layer contains copper. A metal-ceramic substrate characterized by the following features.

2. The metal-ceramic substrate according to claim 1, characterized in that the solid material contains the metal of the metal layer.

3. The metal-ceramic substrate according to claim 1, characterized in that the non-solid material contains a gaseous material.

4. The following requirements must be met, i.e., A(BCD ｓｏｌｉｄ ) / A(BCD ｔｏｔａｌ )>95% The metal-ceramic substrate according to claim 1, characterized in that it is the same as described above.

5. An electronic component comprising a metal-ceramic substrate as described in claim 1.

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