Metal-ceramic substrates and electronic components comprising metal-ceramic substrates

Abstract

This invention provides a metal-ceramic substrate with improved partial discharge resistance. [Solution] The present invention relates to a metal-ceramic substrate comprising (i) a ceramic body and (ii) a metal layer planarly bonded to the ceramic body, having at least one recess, through which the surface of the ceramic body is exposed, wherein the surface of the ceramic body exposed through the recess has an active metal content of 0.5 to 15% by weight.

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 attached to a ceramic body and the composite is heated, the copper compound melts, wetting the surface of the ceramic body and forming a stable cohesive 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, where a specific activated solder is used, which contains a metal (usually silver) with a melting point of at least 700°C and an activated metal. The role of the activated metal 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 the 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 weight percent silver, as well as copper, bismuth, and an activated metal. This method ensures that the copper foil is securely attached to the ceramic body. Alternatively, metal foil can be bonded to a ceramic body using activated solder that does not contain silver. These activated 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 activated 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 such an activated-soldered metal-ceramic substrate, the metal foil is typically first bonded to the ceramic material across its entire surface via activated solder. In the next step, the metal-ceramic substrate is structured to form contact areas for, for example, semiconductor components (such as chips). For structuring, the metal-ceramic substrate is typically first treated with a first etching solution, thereby removing the metal foil in several areas. After this, it is typically treated with a second etching solution to completely remove the remaining reaction layer containing the activated metal, thereby electrically insulating the individual contact areas from each other.

[0006] Metal-ceramic substrates manufactured in this manner are typically exposed to high voltages during operation as part of electronic components. At high voltages, the insulation between contact areas may not withstand the electrical load, increasing the risk of partial discharge. Therefore, to prevent this, it is necessary to ensure that the contact areas are adequately insulated from each other.

[0007] Therefore, it is desirable to further increase the partial discharge resistance of the metal-ceramic substrate.

[0008] Therefore, the present invention aims to provide a metal-ceramic substrate with improved partial discharge resistance.

[0009] This objective is achieved by the metal-ceramic substrate of claim 1. Therefore, the present invention relates to a metal-ceramic substrate, (i) Ceramic body and (ii) A metal layer bonded planarly to a ceramic body, the metal layer having at least one recess through which the surface of the ceramic body is exposed, The surface of the ceramic body exposed through the recess provides a metal-ceramic substrate having an active metal content of 0.5 to 15% by weight.

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

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

[0012] The metal-ceramic substrate according to the present invention includes a ceramic body.

[0013] The ceramic body is preferably a body formed from ceramic. The body can have any geometric shape, but is preferably designed as a rectangular parallelepiped. The ceramic body has interfaces, and in the case of a rectangular parallelepiped, it has six interfaces. The ceramic body preferably comprises primary interfaces. In this specification, primary interfaces preferably refer to interfaces that connect to a metal layer at their surface (particularly very preferably the interface having the maximum surface area). Particularly preferably, primary interfaces refer to interfaces that are planarly joined to a metal layer including at least one recess (particularly very preferably the interface having the maximum surface area). Primary interfaces preferably lie in or extend parallel to the primary extending plane of the ceramic body. Thus, the principal extending plane of the ceramic body is understood to preferably be a plane that extends parallel to or surrounds the primary interfaces of the ceramic body.

[0014] 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, silicon nitride ceramics, and aluminum oxide ceramics (such as ZTA ("zirconia toughened alumina") ceramics). In a particularly 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.

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

[0016] The metal-ceramic substrate according to the present invention includes a metal layer bonded planarly to a ceramic body, the metal layer includes at least one recess, and the surface of the ceramic body is exposed through the recess.

[0017] The metal layer preferably includes an interface. The metal layer preferably includes a primary interface. The primary interface is preferably referred herein to as the interface opposite to the ceramic body (particularly very preferably the interface having the largest surface area). The primary interface is preferably located in or extending parallel to the primary extending plane of the metal layer. Thus, the primary extending plane of the metal layer is understood to be preferably a plane that extends parallel to or surrounds the primary interface of the metal layer. The primary interface of the metal layer preferably extends parallel to the primary interface of the ceramic body, and particularly preferably spaced apart from it.

[0018] The metal layer preferably comprises at least one metal selected from the group consisting of copper and aluminum. In a particularly preferred embodiment, the metal layer comprises copper. In a further preferred embodiment, the metal layer comprises a reaction layer. The reaction layer preferably comprises an active metal. Preferably, the reaction layer is in contact with the ceramic body. Furthermore, it is preferable that the reaction layer is in contact with the rest of the metal layer. Therefore, it is preferable that the reaction layer is located between the ceramic body and the rest of the metal layer. In a preferred embodiment, the reaction layer has a higher active metal content than the rest of the metal layer. In a further preferred embodiment, the proportion of copper is at least 60% by weight, more preferably at least 65% by weight, even more preferably at least 70% by weight, and particularly preferably at least 75% by weight, based on the total weight of the metal layer.

[0019] The metal layer is preferably joined to the ceramic body in a planar manner. Preferably, the metal layer is material-bonded to the ceramic body. According to a preferred embodiment, the metal layer is joined to the ceramic body via an active soldering process. The active soldering process may be, for example, an AMB (active metal brazing) process. In the AMB process, the metal layer is joined to the ceramic body, preferably using active solder for material bonding. According to a preferred embodiment, the active solder comprises a metal M1 having a melting point of at least 700°C. Preferably, metal M1 is copper. According to a further preferred embodiment, the active solder comprises a metal M2 having a melting point of less than 700°C. Preferably, metal M2 is tin. According to an even more preferred embodiment, the active solder comprises a metal M3 selected from the group of active metals. Preferably, metal M3 is selected from the group consisting of hafnium, titanium, zirconium, niobium, tantalum, vanadium, and cerium. Particularly preferably, metal M3 is titanium. In a more preferred embodiment, the activated solder comprises a metal M4 selected from the group consisting of bismuth, gallium, zinc, indium, germanium, aluminum, and magnesium. In a preferred embodiment, the activated solder has a silver content of less than 1.0 wt% based on the solid content of the activated solder. In an alternative embodiment, the activated solder has a silver content of at least 50 wt% based on the solid content of the activated solder. In the activated soldering process, it is preferable that a reaction layer is formed as part of the metal layer, and the metal layer is material-bonded to the ceramic body via this reaction layer.

[0020] The metal layer is preferably bonded to the ceramic body in a planar manner. Therefore, the metal layer is preferably bonded planarly to the primary interface of the ceramic body. The metal layer is preferably not bonded to the entire primary interface of the ceramic body. In particular, the primary interface of the ceramic body can be larger than the surface of the metal layer bonded to the ceramic body. In these cases, the primary interface of the ceramic body protrudes.

[0021] 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.

[0022] The metal layer includes at least one recess, through which the surface of the ceramic body is exposed. Preferably, at least one recess electrically insulates separate regions of the metal layer from each other. The metal layer including at least one recess may also be referred to as a structured metal layer. Semiconductor components can be mounted on the structured metal layer. Preferably, at least one recess is formed by treating the metal layer with at least one etching solution and / or radiant energy.

[0023] A recess is preferably understood to mean a region of the metal layer obtained by removing material from the metal layer. Preferably, a recess is a region where no material of the metal layer is present and is located between adjacent regions of the metal layer (particularly preferably on the main extending surface of the metal layer). Therefore, it is preferable that a recess exists between two adjacent regions of the metal layer.

[0024] The surface of the ceramic body exposed through the recess preferably contains the material of the ceramic body. The surface of the ceramic body exposed through the recess contains an active metal. The active metal preferably originates from a reaction layer generated during the active soldering process. The active metal preferably exists as a reaction product with elements of the ceramic material. According to a preferred embodiment, the active metal exists as an active metal compound. The active metal compound is preferably selected from the group consisting of active metal nitrides, active metal silide, and active metal aluminide. The active metal compound is particularly preferably titanium nitride, titanium silide, or titanium aluminide. The active metal is preferably selected from the group consisting of hafnium, titanium, zirconium, niobium, vanadium, tantalum, cerium, and mixtures thereof. According to a particularly preferred embodiment, the active metal is titanium.

[0025] According to the present invention, the surface of the ceramic body exposed through the recess has an active metal content of 0.5 to 15% by weight. According to a preferred embodiment, the surface of the ceramic body exposed through the recess has a content of 0.6 to 14% by weight. The active metal content of the surface of the ceramic body exposed through the recess is preferably determined by scanning electron microscopy - energy dispersive X-ray spectroscopy (SEM-EDX).

[0026] Surprisingly, it has been found that when the surface of the ceramic body exposed through the recess has an active metal content of 0.5 to 15% by weight, the partial discharge resistance of the metal-ceramic substrate is significantly increased.

[0027] According to an even more preferred embodiment, the surface of the ceramic body exposed through at least one recess contains active metal islands. The term "active metal island" is preferably understood to mean a region having an accumulation of active metal that can be distinguished in an image obtained by scanning electron microscopy - energy dispersive X-ray spectroscopy (SEM-EDX) (preferably as described in the test method section).

[0028] According to yet another preferred embodiment, the active metal islands have an average area in the range of 5 to 65 μm 2 . The active metal islands particularly preferably have an average area in the range of 10 to 65 μm 2 and very particularly preferably have an average area in the range of 10 to 60 μm 2 .

[0029] According to yet another preferred embodiment, the active metal islands are spaced apart from each other by at least 2 μm on average.

[0030] The active metal islands are preferably spaced at least 2 μm apart on average, particularly preferably at least 3 μm apart, and very preferably at least 4 μm apart. The active metal islands are preferably spaced at less than 20 μm apart on average, particularly preferably less than 18 μm apart, and very preferably less than 15 μm apart. According to a preferred embodiment, the active metal islands are spaced at least 2 to 20 μm apart on average, particularly preferably 3 to 18 μm apart, and very preferably 4 to 15 μm apart.

[0031] Surprisingly, the active metal island (A) 5~65μm 2 It has the average area of ​​the range, and (B) On average, they are separated by at least 2 μm from each other. It was found that partial discharge resistance could be further improved.

[0032] In a preferred embodiment, the metal-ceramic substrate comprises a further (second) metal layer connected planar to the ceramic body. The further metal layer is preferably connected planar to an interface opposite to the primary interface of the ceramic (preferably extending parallel to the primary 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 with reference to the description of the (first) metal layer.

[0033] 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.

[0034] Therefore, the present invention also provides electronic components comprising a metal-ceramic substrate according to the present invention.

[0035] According to a preferred embodiment, the electronic component comprises a metal-ceramic substrate according to the present invention and at least one semiconductor component. The at least one semiconductor component is preferably bonded planarly to the (first) metal layer.

[0036] In a more preferred embodiment, the metal-ceramic substrate of the electronic component comprises a further (second) metal layer. The further (second) metal layer is preferably bonded to the ceramic body at its surface. In this case, the further metal layer is preferably bonded at its surface to the interface of the ceramic body opposite to the primary interface of the ceramic body (preferably extending parallel thereto).

[0037] In a more preferred embodiment, the electronic component includes a heat sink. This heat sink is preferably bonded planarly to a further (second) metal layer of the metal-ceramic substrate. Alternatively, the further (second) metal layer of the metal-ceramic substrate can be designed as a heat sink.

[0038] In a more preferred embodiment, the electronic component comprises a metal-ceramic substrate including a (first) metal layer and a further (second) metal layer (the further metal layer is preferably bonded planarly to the interface opposite to the primary interface of the ceramic body), a heat sink, and at least one semiconductor component, the at least one semiconductor component being bonded planarly to the first metal layer of the metal-ceramic substrate, and the heat sink being bonded planarly to the further (second) metal layer of the metal-ceramic substrate.

[0039] The metal-ceramic substrate according to the present invention can be obtained by various manufacturing processes.

[0040] The present invention also relates to a method for manufacturing a metal-ceramic substrate according to the present invention.

[0041] The method for manufacturing a metal-ceramic substrate 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 planarly to a ceramic body, b) A method comprising the step of forming at least one recess in a metal layer, wherein the surface of a ceramic body is exposed through the recess, and the surface of the ceramic body exposed through the recess has an active metal content of 0.5 to 15% by weight.

[0042] In step a), the metal-ceramic substrate is first provided.

[0043] This metal-ceramic substrate comprises a ceramic body and a metal layer bonded planarly to 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 material-bonded to the ceramic body as described above with respect to the metal-ceramic substrate. Material bonding is preferably carried out via an active soldering process, particularly an AMB process. Therefore, according to a preferred embodiment, the metal-ceramic substrate is a metal-ceramic substrate manufactured by an active soldering process, particularly an AMB process.

[0044] In step b), a recess is formed in the metal layer, and the surface of the ceramic body is exposed through the recess, and the surface of the ceramic body exposed through the recess has an active metal content of 0.5 to 15% by weight.

[0045] The recesses in the metal layer are preferably formed to separate individual parts of the metal layer from each other and thus electrically insulate them. Therefore, the recesses expose the surface of the ceramic body.

[0046] The recesses can be formed in principle by methods conventional in the art. Preferably, the recesses are formed by at least one removal process selected from the group consisting of etching, introduction of radiant energy, and mechanical removal (e.g., wet blasting, dry blasting, or milling). Particularly preferably, the recesses are formed by at least one removal process selected from the group consisting of etching and introduction of radiant energy.

[0047] According to a preferred embodiment, the recess is formed by etching.

[0048] For this purpose, it is preferable that an etching mask is first applied to the metal layer. The etching mask serves to protect the masked areas of the metal layer from etching in the etching step. This ensures that only the areas of the metal layer of the metal-ceramic substrate that are not masked and are intended to form recesses are accessible for etching. Thus, the etching mask is designed so that etching does not occur in the masked areas of the metal layer during the etching step. The type of etching mask is not limited. The etching mask can be, for example, a standard negative mask or a positive mask. A standard etching resist can be used to produce the etching mask. These etching resists preferably contain a curable polymer (e.g., a photocurable polymer) and can be applied to the metal layer as a film (e.g., as a dry film) or as a liquid (e.g., by printing or spraying). After application, the etching resist can be treated in an appropriate manner (e.g., cured by light irradiation) to obtain the etching mask. According to one possible embodiment, a photosensitive film is applied to the metal layer of the metal-ceramic substrate and then exposed to the areas to be masked in order to obtain the etching mask. Next, the unexposed areas of the photosensitive film can be removed using conventional methods (for example, using a sodium carbonate solution).

[0049] Etching is preferably performed in step b1 (etching) and step b2 (etching).

[0050] In step b1 (etching), the unmasked areas of the metal layer are preferably etched to obtain recesses. Etching is preferably carried out by a standard conventional 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 solution and CuCl2 etching solution.

[0051] After etching in step b1 (etching), for example, if the metal-ceramic substrate was manufactured according to the AMB process using activated solder, a reaction layer containing the activated metal may still be present on the ceramic body. In this case, the metal layer is usually removed down to the reaction layer by a conventional etching solution, and as a result, the surface beneath the ceramic body is not yet exposed, and other separated regions of the metal layer remain electrically bonded to each other through the remaining reaction layer.

[0052] Therefore, in step b2 (etching), it is preferable to further etch and partially remove the reaction layer that remained exposed in step b1 (etching).

[0053] Further etching is preferably carried out using a further (second) etching solution. The further etching solution can be selected from the group consisting of etching solutions containing hydrogen peroxide and etching solutions containing ammonium peroxodisulfate. For example, the further etching solution may be an etching solution containing ammonium fluoride and fluoroboric acid (e.g., HBF4) and hydrogen peroxide and / or ammonium persulfate.

[0054] After step b2 (etching), it is preferable to remove the etching mask. The etching mask can be removed by standard methods. For this purpose, the metal-ceramic substrate can be treated with an alkaline solution (e.g., a 2.5% sodium hydroxide solution).

[0055] In a more preferred embodiment, the recess is formed by a combination of etching and the introduction of radiant energy.

[0056] In step b1 (etching), the unmasked areas of the metal layer are preferably etched to obtain the recesses described above.

[0057] In step b2 (radiation), it is preferable to partially remove the reaction layer that remained and was exposed in step b1 (etching) by introducing radiant energy.

[0058] The radiated energy is preferably introduced using an ultrashort pulse laser (e.g., an IR picosecond or femtosecond laser). An ultrashort pulse laser is a laser capable of emitting laser pulses having pulse durations in the range of picoseconds ("picosecond laser") or femtoseconds ("femtosecond laser"). The pulsed laser beam of an ultrashort pulse laser includes, for example, laser pulses having pulse durations in the range of picoseconds ("picosecond laser") or femtoseconds ("femtosecond laser"). For example, the pulse duration is 1 fs to 100 ps (e.g., 1 to 100 ps or less than 1 to 1000 fs).

[0059] In this case, the etching mask can be removed by conventional methods, for example, as described above, either before or after step b2 (emission).

[0060] In a more preferred embodiment, the recess is formed by introducing radiant energy.

[0061] In step b (radiation), it is preferable to form a recess by partially removing the metal layer containing the reaction layer that contains the activated metal.

[0062] The radiant energy is preferably introduced using an ultrashort pulse laser (e.g., an IR picosecond or femtosecond laser) as described above. When the recess is formed by the introduction of radiant energy, the application of an etching mask can be omitted.

[0063] In step b), the parameters for forming a recess in the metal layer are preferably directly selected such that the surface of the ceramic body is exposed through the recess and the surface of the ceramic body exposed through the recess has an active metal content of 0.5 to 15% by weight. Similarly, the parameters for forming a recess in the metal layer are preferably such that the surface of the ceramic body exposed through at least one recess includes an active metal island and the active metal island is 5 to 65 μm 2 The average area is within the range and / or the active metal islands are directly selected such that they are spaced at least 2 μm apart from each other on average.

[0064] When recesses in the metal layer are formed by etching, in step b2 (etching), the concentration of the further (second) etching solution, the exposure time of the metal-ceramic substrate provided in step b1 (etching) to the further (second) etching solution, and the processing temperature and processing time, in particular, determine the active metal content of the surface of the ceramic body exposed through the recesses, as well as the presence and characteristics of active metal islands. The parameters necessary to set the values ​​according to the present invention can be determined, for example, by a simple series of tests varying the concentration of the further (second) etching solution, the exposure time to the further (second) etching solution, and the processing temperature and processing time.

[0065] When recesses in the metal layer are formed by introducing radiant energy in step b (radiation) or step b2 (radiation), the total fluence of the preferably used ultrashort pulse laser determines, in particular, the active metal content of the ceramic surface exposed through the recesses, as well as the presence and characteristics of active metal islands. The laser parameters necessary to set the values ​​according to the present invention can be determined, for example, by a simple series of tests that vary the laser fluence.

[0066] According to the method of the present invention, a metal-ceramic substrate with high partial discharge resistance can be obtained.

[0067] The present invention will be described below with reference to the drawings, but this should not be understood as a limitation. [Brief explanation of the drawing]

[0068] [Figure 1] A side view of the metal-ceramic substrate according to the present invention is shown (not to scale).

[0069] The metal-ceramic substrate 1 shown in Figure 1 comprises a ceramic body 10 (having a main extending surface 12) and a metal layer 20. The metal layer 20 is planarly bonded to the primary interface of the ceramic body 10. In the embodiment shown in Figure 1, the metal-ceramic substrate 1 further comprises a further metal layer 200 planarly bonded to the ceramic body 10. The metal layer 20 includes a reaction layer 24 and the rest of the metal layer 26. The reaction layer 24 preferably contains an active metal and is in contact with the ceramic body 10. Furthermore, the reaction layer 24 is in contact with the rest of the metal layer 26. The metal layer 20 includes a recess 22 that exposes the surface of the ceramic body 10. The surface of the ceramic body 10 exposed through the recess 22 has an active metal content of 0.5 to 15% by weight. The active metal preferably exists in the form of an active metal island 28. The active metal island 28 is 5 to 65 μm 2 They have an average area within the range and are spaced at least 2 μm apart from each other on average.

[0070] Test method 1. Determination of the active metal content on the surface of the ceramic body exposed through the recess. The active metal content on the surface of the ceramic body exposed through the recess is preferably determined by scanning electron microscopy-energy-dispersive X-ray spectroscopy (SEM-EDX).

[0071] In SEM-EDX, a focused primary electron beam is guided (scanned) point by point across the sample surface. Backscattered and secondary electrons are detected by detectors within the SEM chamber, and the number of electrons per pixel yields a grayscale microscopic image of the sample surface. Furthermore, the primary electron beam excites the sample to emit characteristic X-ray radiation, and the elements in the sample and their weight percentages can be determined by analyzing the energy spectrum using the EDX detector.

[0072] A scanning electron microscope (e.g., Gemini Ultra 55, ZEISS Ltd) equipped with a silicon drift EDX detector (e.g., Ultimax 100, Oxford Instruments) and analytical software (e.g., AZtec, Oxford Instruments) is preferably used for the test. To prepare for the test, the sample surface is first coated with a very thin (several nm thick) layer of carbon (e.g., using an SCD 005 sputter coater with a CEA 035 carbon evaporation feed, BalTec AG). The sample is then placed in the sample chamber and the chamber is placed under vacuum. Subsequently, the sample is inspected by SEM-EDX. The following settings are preferably used: Magnification: 100x, 500x, 1,000x. Acceleration voltage = 15kV. A separate EDX spectrum is recorded for each measured point on the sample surface. All recorded EDX spectra are processed by the analytical software to determine the quantitative chemical composition for each point. This allows for the quantitative determination of the average content of elements (e.g., active metals) on the sample surface. The elemental content is determined by both atomic and weight percentages, with the total amount being 100%. The analysis is preferably performed at a magnification of 100x.

[0073] 2. Determination of area and distance between active metal islands Active metal islands are preferably determined by scanning electron microscopy-energy-dispersive X-ray spectroscopy (SEM-EDX) as described above (under "Determination of Active Metal Content on the Surface of Ceramic Bodies Exposed Through Recesses"). In the image obtained by SEM-EDX, active metal islands are identified as distinguishable regions having accumulations of active metals. The analysis software creates an electron microscope image (EDX mapping) using the data obtained by SEM-EDX. EDX mapping is used to represent the spatial distribution of selected elements (e.g., active metal islands) on the sample surface. The area and distance between active metal islands are preferably evaluated by the software ImageJ(1.53c). For this purpose, active metal islands are preferably enclosed by contour lines. The surface area of ​​the relevant region enclosed by contour lines is then output by the software. The shortest distance between two adjacent active metal islands is then determined in each case by drawing straight lines connecting the two contour lines. The length of each straight line is also output by the software.

[0074] In total, it is preferable that at least three SEM-EDX measurements are evaluated per sample. Preferably, all active metal islands visible in the image are evaluated as described above. The average area of ​​the active metal islands and the average distance between active metal islands are preferably determined as the arithmetic mean of all active metal islands visible in the image.

[0075] Exemplary Embodiments The present invention will be described in more detail below using exemplary embodiments, but this should not be understood as limiting.

[0076] 1.Manufacturing To manufacture the metal-ceramic substrates of Examples 1-5 and Comparative Examples 1 and 2, a copper-ceramic substrate was used in each case, in which a ceramic body made of silicon nitride ceramic having dimensions of 177.8 × 139 × 0.32 mm was bonded on both sides to a copper layer having dimensions of 170 × 132 × 0.3 mm by an AMB (activated metal brazing) process. Each copper-ceramic substrate had a titanium-containing reaction layer, which was due to the use of titanium-containing activated solder in the manufacture of the copper-ceramic substrate.

[0077] These copper-ceramic substrates were first cleaned after manufacturing. Then, a photosensitive film was applied to both copper layers of the copper-ceramic substrates using a hot roll laminator. To cure the polymer contained in the photosensitive film and obtain an etching mask, 30 mJ / cm² of the photosensitive film was applied to each area to be masked. 2 The surface was exposed. Next, the unexposed areas of the photosensitive film were chemically removed using a sodium carbonate solution (concentration = 10 g / l). After applying an etching mask, the copper-ceramic substrate was rinsed and cleaned. Subsequently, 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 copper-ceramic substrate was rinsed.

[0078] Subsequently, the unmasked areas of the titanium-containing reaction layer in the copper-ceramic substrate were also wet chemically etched. For this purpose, in an etching system, an etching solution containing ammonium fluoride, fluoroboric acid and hydrogen peroxide was sprayed again onto the copper-ceramic substrate. The contact time with the etching solution was varied for each copper-ceramic substrate in order to obtain the measured titanium residues in Table 1. Thereafter, the copper-ceramic substrates were rinsed and dried. Then, in a stripping system, the etching mask was removed using a 2.5% sodium hydroxide solution.

[0079] The copper-ceramic substrates thus produced each had a large copper contact area of 200 mm 2 in area and a small copper contact area of 20 mm 2 in area on the front surface of the ceramic body, and the copper contact areas were separated from each other by recesses with a width of 1.2 mm. The distance between the copper contact areas and the outer edge of the ceramic body was 0.8 mm (as a periphery) in each case. The back surface of the ceramic body was coated with copper over its entire surface, and the distance between the copper coating and the outer edge of the ceramic body was 0.8 mm (as a periphery) in each case.

[0080] 2. Characteristics of the copper-ceramic substrate For the produced copper-ceramic substrates, in accordance with the above test procedure, the titanium content of the surface of the ceramic body exposed through the recesses was determined by scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDX). Titanium islands were also identified in the electron microscope images, and the area and distance between the titanium islands were examined in accordance with the above test procedure. The results are shown in Table 1.

[0081]

Table 1

[0082] 3. Evaluation The partial discharge resistance (contact area / contact area and top / bottom) of the copper-ceramic substrates obtained in Examples 1-5 and Comparative Examples 1 and 2 was investigated.

[0083] For this purpose, the copper-ceramic substrate was fixed to an insulating frame that completely enclosed the top and bottom surfaces at its edges, thus insulating the top surface from the bottom surface of the copper-ceramic substrate. A central recess in the insulating frame allowed the individual contact areas on the top and bottom surfaces of the copper-ceramic substrate to be brought into contact by spring contacts. Subsequently, the copper-ceramic substrate, thus in contact, was placed in a plastic container filled with insulating liquid (Galden HS 240) so that the individual contact areas were completely covered by the insulating liquid. The spring contacts protruding from the insulating liquid were connected to a measurement and analysis system MPD 600 (OMICRON Electronics). Partial discharge was measured at different operating voltages of 3.6kV (50Hz) (instead of 2.4kV) according to the IEC 61287 standard. (The AC voltage was increased to 3.6kV within 10 seconds and applied for 60 seconds. The indicated partial discharge values ​​were confirmed by averaging over the last 10 seconds.)

[0084] To measure partial discharge between the top and bottom surfaces (upper / lower) of the copper-ceramic substrate, an operating voltage was applied to all contact areas on the front surface, while the metal coating on the back surface was set to GND potential.

[0085] To determine partial discharge between copper contact regions (contact region / contact region), the operating voltage was applied to the larger copper contact region, while the smaller copper contact region was set to GND potential along with the back metal coating to prevent the back metal coating from charging.

[0086] The results are shown in Table 2.

[0087] [Table 2]

[0088] The results show that the copper-ceramic substrates according to the present invention in Examples 1 to 5 are clearly superior to the copper-ceramic substrates of Comparative Examples 1 and 2 in terms of partial discharge resistance.

[0089] Reference Code List 1. Metal-ceramic substrate 10 Ceramic body 12 Main extending surface of the ceramic body 20 metal layer 22 recess 24 Reaction layer 26 Remaining metal layer 28 Active Metal Islands 200 Further metal layer

Claims

1. A metal-ceramic substrate, (i) Ceramic body and (ii) A metal-ceramic substrate comprising a metal layer joined planarly to the ceramic body, having at least one recess, through which the surface of the ceramic body is exposed, A metal-ceramic body characterized in that the surface of the ceramic body exposed through the recess has an active metal content of 0.5 to 15% by weight.

2. The surface of the ceramic body exposed through the at least one recess includes an active metal island, the active metal island having the following characteristics: (A) The active metal island is 5 to 65 μm ２ It has an average area within the range, and (B) The active metal islands are spaced apart from each other by at least one of the above conditions, as described in claim 1.

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

4. The metal-ceramic substrate according to claim 1, characterized in that the metal layer contains copper.

5. The metal-ceramic substrate according to claim 1, characterized in that the active metal is selected from the group consisting of hafnium, titanium, zirconium, niobium, vanadium, tantalum, and cerium.

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

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