Metal-ceramic substrate with double solder layers and method for its production

Abstract

A metal-ceramic substrate with dual solder layers and a method for manufacturing the same are provided. The metal-ceramic substrate comprises a ceramic substrate layer (1), a conductive metal layer (3), and an active metal layer (2) disposed between the ceramic substrate layer (1) and the conductive metal layer (3). The active metal layer (2) comprises a first solder layer (21) formed from a solder of the first active metal and an organic dispersion medium, and a second solder layer (22) formed from a solder of the second active metal and another organic dispersion medium. The solder of the first active metal contains silver, copper, and a first active metal. Based on the total weight of the solder of the first active metal being 100 wt. %, the silver content is in the range of 10 wt. % to 60 wt. %. The solder of the second active metal contains copper and a second active metal, but no silver.

Description

[0001] Some references, which may include patents, patent applications, and various publications, may be cited and discussed in the description of this disclosure. The citation and / or discussion of such references is merely intended to clarify the description of the present disclosure and does not constitute an admission that such reference is "prior art" to the disclosure described herein. All references cited and discussed in this specification are incorporated into this specification in their entirety and to the same extent as if each reference were individually incorporated by reference.

[0002] The present disclosure relates to a metal-ceramic substrate having double solder layers and a method for producing the same, more particularly to a metal-ceramic substrate having double solder layers and a good joining strength and a method for producing the same.

[0003] The promotion of energy conservation and carbon reduction measures in various countries has led to a strong upswing in the global electric vehicle market. In recent years, a variety of high-voltage (800 volt) vehicle products have been successfully launched, leading to increasing demand for silicon carbide (SiC) ceramic substrates.

[0004] However, as the voltage, frequency, and operating temperature requirements of power components of silicon carbide (SiC) ceramic substrate materials continue to increase, the ceramic substrates must also have better heat dissipation and reliability.

[0005] A widely used direct bonded copper (DBC) ceramic substrate is typically manufactured by eutectic bonding. There is no bonding agent between a copper layer and the ceramic substrate. However, during high-temperature operation, due to the different thermal expansion coefficients of the copper layer and the ceramic substrate (such as Al), 2 O 3(AlN) generates large thermal stress, causing the copper layer to peel off from one surface of the ceramic substrate. Therefore, the conventional direct-bonded copper-ceramic substrate can no longer meet the requirements of high temperature, high performance, high heat dissipation, and high reliability.

[0006] Currently, the use of active brazing alloy (AMB) substrate materials is gradually being replaced by the use of direct bonded copper-ceramic substrate materials as the main substrate material.

[0007] Active solder substrate materials typically contain silver. The silver content in active solder substrate materials often exceeds 50 wt% and can even reach 70 wt%. However, due to the high silver content, the material cost of active solder ceramic substrates is high, and the problem of electromigration by silver atoms in a solder layer can occur.

[0008] Therefore, how to reduce the amount of silver in the solder layer by adjusting the materials and structure of the active solder ceramic substrate to overcome the above problems has become one of the most important issues facing the industry.

[0009] In response to the above-mentioned technical deficiencies, the present disclosure provides a metal-ceramic substrate having dual solder layers and a method for manufacturing the same.

[0010] To solve the above-mentioned problems, one of the technical aspects of the present disclosure is to provide a metal-ceramic substrate having dual solder layers. The metal-ceramic substrate includes a ceramic substrate layer, an active metal layer, and a conductive metal layer. The active metal layer is interposed between the ceramic substrate layer and the conductive metal layer. The active metal layer includes a first solder layer and a second solder layer. The first solder layer is formed from a first active metal solder and an organic dispersion medium. The first active metal solder contains silver, copper, and a first active metal. Based on the total weight of the first active metal solder being 100 wt%, the silver content ranges from 10 wt% to 60 wt%.The second solder layer is formed from a second active metal solder and another organic dispersion medium. The second active metal solder contains copper and a second active metal, but no silver.

[0011] To solve the above-mentioned problems, another of the technical aspects of the present disclosure is to provide a method for manufacturing a metal-ceramic substrate with dual solder layers. The method includes: applying a first active metal solder paste to a ceramic substrate, thereby forming a first solder layer on the ceramic substrate; applying a second active metal solder paste to the first solder layer, thereby forming a second solder layer on the first solder layer; and disposing a conductive metal layer on the second solder layer and implementing an active soldering process to obtain a metal-ceramic substrate with dual solder layers. The first active metal solder paste comprises a first active metal solder and an organic dispersion medium. The first active metal solder contains silver, copper, and a first active metal.Based on the total weight of the first active metal solder of 100 wt%, the silver content ranges from 10 wt% to 60 wt%. The second active metal solder paste comprises a second active metal solder and another organic dispersion medium. The second active metal solder contains copper and a second active metal, but no silver.

[0012] Therefore, in the metal-ceramic substrate having the double solder layers and the method for producing the same provided by the present disclosure, due to “the first active metal solder containing silver, copper, and a first active metal,” “based on the total weight of the first active metal solder of 100 wt%, the amount of silver is in the range of 10 wt% to 60 wt%,” and “the second active metal solder containing copper and a second active metal but not silver,” a bonding force between the ceramic substrate layer and the conductive metal layer can be improved.

[0013] These and other aspects of the present disclosure will become apparent from the following description of the embodiment taken in conjunction with the following drawings and their captions, although variations and modifications may be made therein without departing from the spirit and scope of the novel concepts of the disclosure.

[0014] The described embodiments can be better understood with reference to the following description and the accompanying drawings. Fig. 1 is a schematic side view of a metal-ceramic substrate with double solder layers according to the present disclosure, and Fig. 2 is a schematic side view of another metal-ceramic substrate with dual solder layers according to the present disclosure.

[0015] The present disclosure is described in more detail in the following examples, which are given for illustrative purposes only, since numerous modifications and variations therein will be apparent to those skilled in the art. Like numerals in the drawings indicate like components throughout the several views. As used herein in the specification and in the following claims, the meaning of "a" and "the" includes plural references unless the context clearly dictates otherwise, and the meaning of "in" includes "in" and "on." For the convenience of the reader, titles or subtitles may be used herein, but these do not affect the scope of the present disclosure.

[0016] The terms used herein generally have the meaning commonly used in the art. In the event of a conflict, this document, including all definitions contained herein, shall control. The same may be expressed in multiple ways. Alternative expressions and synonyms may be used for all terms discussed herein, and it is not particularly important whether a term is further explained or discussed herein. The inclusion of one or more synonyms does not preclude the use of other synonyms. The use of examples anywhere in this specification, including examples of any term, is for illustrative purposes only and in no way limits the scope and meaning of the present disclosure or any exemplary term. Likewise, the present disclosure is not limited to the various embodiments given herein.Numerals such as "first," "second," or "third" may be used to describe various components, signals, or the like, solely to distinguish one component / signal from another, and these numerals are neither intended nor designed to impose any substantial limitations on the components, signals, or the like.

[0017] To solve the problem of a copper layer peeling off a ceramic substrate due to differences in thermal expansion coefficients in a directly bonded copper-ceramic substrate, the present disclosure provides a metal-ceramic substrate with dual solder layers. In the metal-ceramic substrate, the use of a solder paste of the first active metal and a solder paste of the second active metal enables a good bonding force between the copper layer and the ceramic substrate. Therefore, the metal-ceramic substrate can be used in certain package structures that operate at high temperatures and high power and require high reliability. According to the present disclosure, the bonding force between the copper layer and the ceramic substrate is quantified as the tensile strength of the metal-ceramic substrate for clarity.

[0018] In Fig.1, the metal-ceramic substrate with the dual solder layers according to the present disclosure includes a ceramic substrate layer 1, an active metal layer 2, and a conductive metal layer 3. The active metal layer 2 is disposed between the ceramic substrate layer 1 and the conductive metal layer 3 to combine the ceramic substrate layer 1 and the conductive metal layer 3.

[0019] The active metal layer 2 comprises a first solder layer 21 and a second solder layer 22. The first solder layer 21 contacts the ceramic substrate layer 1. The second solder layer 22 contacts the conductive metal layer 3.

[0020] In Fig.1, the active metal layer 2 and the conductive metal layer 3 are arranged only on one side of the ceramic substrate layer 1, but the present disclosure is not limited thereto. The active metal layer 2 and the conductive metal layer 3 may be arranged on both sides of the ceramic substrate layer 1 (as in Fig. 2).

[0021] In Fig. 2, the metal-ceramic substrate with the double solder layers can have a symmetrical structure. The first solder layers 21, 21', the second solder layers 22, 22', and the conductive metal layers 3, 3' are each arranged on two opposite sides of the ceramic substrate layer 1. Accordingly, the metal-ceramic substrate can be used to manufacture a package structure with double conductive layers. [Ceramic substrate layer]

[0022] The ceramic substrate layer 1 may be a ceramic substrate made of silicon nitride (SiN), silicon carbide (SiC), aluminum nitride (AIN) or aluminum oxide (Al 2 O 3 ). The ceramic substrate layer 1 is preferably a ceramic substrate containing silicon, and more preferably a ceramic substrate made of silicon nitride (SiN). The thickness of the ceramic substrate layer 1 may be between 100 µm and 1000 µm, but the present disclosure is not limited thereto. [Active metal layer]

[0023] The active metal layer 2 can improve the bonding strength between the ceramic substrate layer 1 and the conductive metal layer 3. If the active metal layer 2 is too thin, the bonding strength between the ceramic substrate layer 1 and the conductive metal layer 3 decreases. If the active metal layer 2 is too thick, the material cost of the active metal layer 2 may be too high, which is not advantageous for mass production.

[0024] The thickness of the active metal layer 2 may be greater than or equal to 6 µm. Preferably, the thickness of the active metal layer 2 may be between 10 µm and 30 µm, for example, 12 µm, 14 µm, 16 µm, 18 µm, 20 µm, 22 µm, 24 µm, 26 µm, or 28 µm. More preferably, the thickness of the active metal layer 2 may be between 18 µm and 24 µm.

[0025] In addition, the thickness ratio between the first solder layer 21 and the second solder layer 22 in the active metal layer 2 may be 1:1 to 1:2 to achieve the expected effect with low material cost, but the present disclosure is not limited thereto. [First solder layer]

[0026] The first solder layer 21 is formed from a solder of the first active metal and an organic dispersion medium.

[0027] The first active metal solder contains silver (Ag), copper (Cu), and a first active metal. The silver content (Ag) is greater than the copper content (Cu), and the copper content (Cu) is greater than the first active metal content.

[0028] Based on the total weight of the first active metal solder of 100 wt%, the silver content ranges from 10 wt% to 60 wt%. Because the silver content in the first active metal solder is lower than in conventional technology, the material cost of the metal-ceramic substrate with the dual solder layers can be reduced, and the probability of silver electromigration can also be reduced.

[0029] In particular, based on the total weight of the first active metal solder of 100 wt%, the silver content may be in the range of 15 wt%, 20 wt%, 25 wt%, 30 wt%, 35 wt%, 40 wt%, 45 wt%, 50 wt% or 55 wt%.

[0030] During a vacuum sintering process, silver atoms of the first solder layer 21 may partially diffuse into an interface between the first solder layer 21 and the second solder layer 22 and form an alloy with metal atoms of the second solder layer 22. Therefore, the first solder layer 21 and the second solder layer 22 may have good bonding strength. For example, the silver of the first solder layer 21 and the copper of the second solder layer 22 may form a silver-copper alloy.

[0031] According to an exemplary embodiment, based on the total weight of the solder of the first active metal of 100 wt.%, the copper content is in the range of 30 wt.% to 80 wt.% and the content of the first active metal is in the range of 1 wt.% to 10 wt.%.

[0032] In particular, the copper content can be 35 wt%, 40 wt%, 45 wt%, 50 wt%, 55 wt%, 60 wt%, 65 wt%, 70 wt% or 75 wt%.

[0033] In particular, the proportion of the first active metal may be 2 wt%, 4 wt%, 6 wt%, or 8 wt%. Preferably, based on the total weight of the first active metal solder of 100 wt%, the proportion of the first active metal is in the range of 2 wt% to 4 wt%.

[0034] Note that the melting point of the first active metal is low, so the first active metal is melted in advance during the vacuum sintering process. The molten first active metal can be filled into small openings of the ceramic substrate layer 1 or the second solder layer 22 and even react with the ceramic substrate layer 1 or the second solder layer 22. On the other hand, the first active metal can also reduce the electrical impedance of the first solder layer 21.

[0035] The first active metal can in particular be selected from the group consisting of titanium (Ti), zirconium (Zr), tantalum (Ta), niobium (Nb), vanadium (V) and hafnium (Hf).

[0036] During the vacuum sintering process, the first active metal of the first solder layer 21 may partially diffuse into an interface between the first solder layer 21 and the ceramic substrate layer 1, forming a metal silicide containing silicon atoms of the ceramic substrate layer 1 or a metal nitride containing nitrogen atoms of the ceramic substrate layer 1. Similarly, the first active metal of the first solder layer 21 may also partially diffuse into the interface between the first solder layer 21 and the second solder layer 22 to form an alloy. Therefore, the ceramic substrate layer 1 and the conductive metal layer 3 can exhibit good bonding strength.

[0037] According to an exemplary embodiment, the first active metal is titanium. During the vacuum sintering process, titanium diffuses into the ceramic substrate layer 1 to form titanium silicide (TiSi), silicon nitride (TiN), or titanium disilicide (TiSi2 2 ) with silicon atoms or nitrogen atoms. Furthermore, titanium atoms may also diffuse into the second solder layer 22 and form a titanium-copper alloy with copper atoms of the second solder layer 22, but the present disclosure is not limited thereto. [Second solder layer]

[0038] The second solder layer 22 is formed from a solder of the second active metal and another organic dispersion medium. The second solder layer 22 is arranged between the first solder layer 21 and the conductive metal layer 3 to prevent electromigration of silver from the first solder layer 21 to the conductive metal layer 3.

[0039] The second active metal solder contains copper (Cu) and a second active metal, but no silver (Ag). The copper (Cu) content is higher than the second active metal content, and the copper (Cu) content is not higher than 95 wt%.

[0040] In particular, the copper content can be 5 wt%, 10 wt%, 15 wt%, 20 wt%, 25 wt%, 30 wt%, 35 wt%, 40 wt%, 45 wt%, 50 wt%, 55 wt%, 60 wt%, 65 wt%, 70 wt%, 75 wt%, 80 wt%, 85 wt% or 90 wt%.

[0041] During the vacuum sintering process, the copper atoms of the second solder layer 22 can partially diffuse into the interface between the first solder layer 21 and the second solder layer 22 to form an alloy with metal atoms of the first solder layer 21. Therefore, the first solder layer 21 and the second solder layer 22 can have good bonding strength. For example, the copper of the second solder layer 22 and the silver of the first solder layer 21 can form a silver-copper alloy.

[0042] According to an exemplary embodiment, based on the total weight of the solder of the second active metal of 100 wt.%, the proportion of the second active metal is in the range of 1 wt.% to 10 wt.%.

[0043] In particular, the proportion of the second active metal can be 2 wt%, 4 wt%, 6 wt%, or 8 wt%. Preferably, the proportion of the second active metal can range from 2 wt% to 4 wt%.

[0044] Note that the melting point of the second active metal is low, so the second active metal is melted in advance during the vacuum sintering process. The molten second active metal can be filled into small openings of the first solder layer 21 or the conductive metal layer 3 and even react with the first solder layer 21 or the conductive metal layer 3. On the other hand, the second active metal can also reduce the electrical impedance of the second solder layer 22.

[0045] The second active metal can in particular be selected from the group consisting of titanium (Ti), zirconium (Zr), tantalum (Ta), niobium (Nb), vanadium (V) and hafnium (Hf).

[0046] During the vacuum sintering process, the second active metal of the second solder layer 22 can partially diffuse into the interface between the first solder layer 21 and the second solder layer 22 and forms an alloy with the metal atoms of the first solder layer 21. The second active metal of the second solder layer 22 can also partially diffuse into an interface between the second solder layer 22 and the conductive metal layer 3 and forms an alloy with metal atoms of the conductive metal layer 3. Accordingly, the ceramic substrate layer 1 and the conductive metal layer 3 can have a good bonding strength.

[0047] According to an exemplary embodiment, the second active metal is titanium. During the vacuum sintering process, the titanium atoms diffuse into the first solder layer 21 to form a titanium-copper alloy with the copper atoms of the first solder layer 21. Furthermore, the titanium atoms may also diffuse into the conductive metal layer 3 and form a titanium-copper alloy with copper atoms of the conductive metal layer 3, but the present disclosure is not limited thereto. [Conductive metal layer]

[0048] The conductive metal layer 3 can be arranged on the ceramic substrate layer 1 over the active metal layer 2. In particular, the conductive metal layer 3 can be a copper foil, an aluminum foil, or a copper-aluminum alloy foil. According to an exemplary embodiment, the conductive metal layer 3 is a copper foil.

[0049] The thickness of the conductive metal layer 3 may be between 50 µm and 1200 µm. Preferably, the thickness of the conductive metal layer 3 may be between 200 µm and 800 µm, but the present disclosure is not limited thereto. [Method for producing a metal-ceramic substrate with double solder layers]

[0050] In step S1, the first active metal solder paste is prepared. The first active metal solder paste is used to form the first solder layer 21. The first active metal solder paste includes the first active metal solder and the organic dispersion medium mentioned above.

[0051] The first active metal solder contains silver, copper, and the first active metal mentioned above. According to an exemplary embodiment, the first active metal solder is a combination of a silver powder, a copper powder, and a first active metal powder. According to another embodiment, the first active metal solder may contain a silver-copper alloy powder and the first active metal powder, and may further selectively contain at least one of silver powder and copper powder.

[0052] As mentioned above, based on the total weight of the first active metal solder of 100 wt%, the silver content ranges from 10 wt% to 60 wt%. The weight ratio of silver to copper is greater than 1. The weight ratio of copper to the first active metal is greater than 1.

[0053] The organic dispersion medium can help disperse the first active metal solder and solidify the first active metal solder paste to form the first solder layer 21. Specifically, the organic dispersion medium contains a paste-forming agent, an organic solvent, and a thixotropic agent. Based on the total weight of the organic dispersion medium of 100 wt%, the proportion of the paste-forming agent is in the range of 20 wt% to 30 wt%, the proportion of the organic solvent is in the range of 50 wt% to 70 wt%, and the proportion of the thixotropic agent is in the range of 1 wt% to 5 wt%.

[0054] For example, the paste-forming agent can be selected from the group consisting of silicone oil, white oil, polyvinyl alcohol, acrylic resin, nitrocellulose, ethylcellulose, dimethyl phthalate, and carboxymethylcellulose. Preferably, the paste-forming agent is ethylcellulose,

[0055] The organic solvent can be selected from the group consisting of ethylene glycol butyl ether acetate, diethylene glycol, triethanolamine, butyl cellosolve (ethylene glycol monobutyl ether), tert-butyl alcohol, N,N-dimethylformamide, terpineol, and nonylphenol polyglycol ether. Preferably, the organic solvent can be terpineol or ethylene glycol butyl ether acetate.

[0056] The thixotropic solvent can be selected from the group consisting of polyamide wax, hydrogenated castor oil, and polyurea. Preferably, the thixotropic agent is polyamide wax.

[0057] The first active solder and the organic dispersion medium are mixed in a weight ratio of 70% to 95%: 5% to 30% to form the first active metal solder paste with a viscosity of 50 mPa s to 300 mPa s. Preferably, the weight ratio of the first active metal solder to the organic dispersion medium is 75% to 90%: 10% to 25%.

[0058] However, the present disclosure is not limited to the above-mentioned examples, and as long as the first active metal solder and the organic solvent can be processed into a first active metal solder paste having a suitable viscosity to be applied to the ceramic substrate layer 1 and form the first solder layer 21, such a method or configuration for achieving this purpose is considered to be within the spirit and scope of the present disclosure.

[0059] In step S2, the first active metal solder paste may be applied to the ceramic substrate layer 1 by screen printing and dried at a temperature of 90°C to 110°C for 5 minutes to 15 minutes. In this way, most of the organic solvent in the first active metal solder paste evaporates, forming the first solder layer 21.

[0060] In step S3, the second active metal solder paste is prepared. The second active metal solder paste is used to form the second solder layer 22. The second active metal solder paste includes the second active metal solder and the organic dispersion medium mentioned above.

[0061] The second active metal solder contains copper and the second active metal mentioned above. According to an exemplary embodiment, the second active metal solder is a combination of a copper powder and a second active metal powder. As mentioned above, the copper content in the second active metal solder is at least 85 wt% and is higher than the content of the second active metal powder in the second active metal solder (based on the total weight of the second active metal solder being 100 wt%).

[0062] The organic dispersion medium can help disperse the second active metal solder and solidify the second active metal solder paste to form the second solder layer 22. The organic dispersion medium specifically contains the above-mentioned paste-forming agent, the organic solvent, and the thixotropic agent and is therefore not listed again here.

[0063] The second active solder and the organic dispersion medium are mixed in a weight ratio of 70% to 95%: 5% to 30% to form the second active metal solder paste with a viscosity of 50 mPa s to 300 mPa s. Preferably, the weight ratio of the second active metal solder to the organic dispersion medium is 75% to 90%: 10% to 25%.

[0064] However, the present disclosure is not limited to the above-mentioned examples, and as long as the second active metal solder and the organic solvent can be processed into a second active metal solder paste having a suitable viscosity to be applied to the first solder layer 21 and form the second solder layer 22, such a method or configuration for achieving this purpose is considered to be within the spirit and scope of the present disclosure.

[0065] In step S4, the second active metal solder paste may be applied to the first solder layer 21 by screen printing and dried at a temperature of 90°C to 110°C for 5 minutes to 15 minutes. In this way, most of the organic solvent in the second active metal solder paste evaporates, forming the second solder layer 22.

[0066] In step S5, the conductive metal layer 3 is disposed on the second solder layer 22, after which an active soldering process is implemented to fix the conductive metal layer 3 on the ceramic substrate layer 1.

[0067] The active brazing process includes a first heat treatment step and a second heat treatment step, which can be implemented in a vacuum environment. The processing temperature of the first heat treatment step is not higher than 500°C. The processing temperature of the second heat treatment step is between 900°C and 1100°C (i.e., the active brazing temperature). The processing temperature of the second heat treatment step is higher than the processing temperature of the first heat treatment step.

[0068] Specifically, the processing temperature in the first heat treatment step is between 300°C and 500°C, and the processing time is between 30 minutes and 60 minutes. The processing temperature in the second heat treatment step is between 900°C and 960°C, and the processing time is between 60 minutes and 240 minutes. Additionally, the temperature rise rates of the aforementioned heat treatment steps may be between 5°C / min and 30°C / min, and the temperature decrease rates of the aforementioned heat treatment steps may be between 2°C / min and 30°C / min.

[0069] During the active soldering process, the organic dispersion medium is partially evaporated. A surface of the ceramic substrate layer 1 is wetted by the first active metal, and the ceramic substrate layer 1 reacts with the first active metal to increase the bonding force between the active metal layer 2 and the ceramic substrate layer 1. Furthermore, at the interface between the active metal layer 2 and the conductive metal layer 3, the second active metal and the metal atoms of the conductive metal layer 3 undergo a micrometer-scale eutectic reaction, forming a strong eutectic structure. This firmly bonds the active metal layer 2 and the conductive metal layer 3. [Tests 1 to 6]

[0070] In order to compare the influences of the active soldering temperature and the components of the first solder layer 21 and the second solder layer 22 on the tensile strength of the metal-ceramic substrate, the metal-ceramic substrates from Test 1 to Test 6 are manufactured in the above-mentioned steps S1 to S5.

[0071] In the metal-ceramic substrates of Test 1 to Test 6, the ceramic substrate layer 1 is a silicon nitride ceramic substrate, the thickness of the first active metal layer 21 is 12 µm, the thickness of the second active metal layer 22 is 12 µm, and the conductive metal layer 3 is a copper layer.

[0072] During the preparation of the first active metal solder paste, ethyl cellulose is used as the paste-forming agent, ethylene glycol butyl acetate is used as the organic solvent, and polyamide wax is used as the thixotropic agent. Based on the total weight of the organic dispersion medium of 100 wt%, the proportion of the paste-forming agent is 25 wt%, the proportion of the organic solvent is 60 wt%, and the proportion of the thixotropic agent is 2.5 wt%.

[0073] During the preparation of the second active metal solder paste, ethyl cellulose is used as the paste-forming agent, ethylene glycol butyl acetate is used as the organic solvent, and polyamide wax is used as the thixotropic agent. Based on the total weight of the organic dispersion medium of 100 wt%, the proportion of the paste-forming agent is 25 wt%, the proportion of the organic solvent is 60 wt%, and the proportion of the thixotropic agent is 2.5 wt%.

[0074] The specific components of the first solder layer 21 and the second solder layer 22, as well as the specific active soldering temperature, are listed in Table 1. The tensile strength of the metal-ceramic substrate is measured at 25 °C according to JIS-C-6481, and the results are listed in Table 1. Table 1 Components of the first solder layer Components of the second solder layer Active soldering temperature Tensile strength Test 1 Copper-titanium Silver-copper-titanium 915 °C N / A Test 2 Silver-copper-titanium Copper-titanium 915 °C > 200 N / cm Test 3 Copper-titanium Silver-copper-titanium 950 °C < 50 N / cm Test 4 Silver-copper-titanium Copper-titanium 950 °C > 200 N / cm Test 5 Silver-copper-titanium Silver-copper-titanium 915 °C 100 to 200 N / cm Test 6 Silver-copper-titanium Silver-copper-titanium 950°C 100 to 200 N / cm

[0075] According to the results listed in Table 1, the tensile strength of the metal-ceramic substrate with the double solder layers can be higher than 200 N / cm when the silver content in the first solder layer 21 is in the range of 10 wt% to 60 wt% and the second solder layer 22 does not contain silver. Even at low active soldering temperatures (between 900 °C and 960 °C), the metal-ceramic substrate with the double solder layers can exhibit the expected tensile strength. [Advantageous effects of the embodiment]

[0076] In summary, in the metal-ceramic substrate having the double solder layers and the method for producing the same provided by the present disclosure, due to “the first active metal solder containing silver, copper, and a first active metal,” “based on the total weight of the first active metal solder of 100 wt%, the amount of silver is in the range of 10 wt% to 60 wt%,” and “the second active metal solder containing copper and a second active metal but no silver,” a bonding force between the ceramic substrate layer and the conductive metal layer can be improved.

[0077] The foregoing description of the exemplary embodiments of the disclosure has been presented for purposes of illustration and description only and is not intended to be exhaustive or to limit the disclosure to the precise forms. Many modifications and variations are possible in light of the above teachings.

[0078] The embodiments were chosen and described in order to explain the principles of the disclosure and its practical application, thereby enabling others skilled in the art to utilize the disclosure and various embodiments with various modifications as are suited to the particular use contemplated. Alternative embodiments will become apparent to those skilled in the art to which the present disclosure belongs without departing from its spirit and scope. List of reference symbols 1 ceramic substrate layer 2, 2' active metal layer 21, 21' first solder layer 22, 22' second solder layer 3, 3' conductive metal layer

Claims

[1] Metal-ceramic substrate with double solder layers, comprising: • a ceramic substrate layer (1), • an active metal layer (2) comprising: ▪ a first solder layer (21) formed from a first active metal solder and an organic dispersion medium, wherein the first active metal solder contains silver, copper and a first active metal, wherein, based on the total weight of the first active metal solder of 100 wt.%, the silver content is in the range of 10 wt.% to 60 wt.%, and ▪ a second solder layer (22) formed from a solder of the second active metal and a further organic dispersion medium, wherein the solder of the second active metal contains copper and a second active metal, but no silver, and • a conductive metal layer (3), • wherein the layer (2) of the active metal is arranged between the ceramic substrate layer (1) and the conductive metal layer (3), the first solder layer (21) contacts the ceramic substrate layer (1) and the second solder layer (22) contacts the conductive metal layer (3). [2] The metal-ceramic substrate of claim 1, wherein the weight ratio of silver to copper in the solder of the first active metal is greater than 1. [3] The metal-ceramic substrate according to claim 1 or 2, wherein, based on the total weight of the solder of the first active metal of 100 wt%, the proportion of the first active metal is in the range of 2 wt% to 4 wt%. [4] The metal-ceramic substrate according to any one of claims 1 to 3, wherein the copper content is at most 95 wt% based on the total weight of the second active metal solder of 100 wt%. [5] Metal-ceramic substrate according to one of claims 1 to 4, wherein the thickness ratio between the first solder layer (21) and the second solder layer (22) is 1:1 to 1:

2. [6] A metal-ceramic substrate according to any one of claims 1 to 5, wherein silver atoms of the first solder layer (21) partially diffuse into an interface between the first solder layer (21) and the second solder layer (22) and form a silver-copper alloy. [7] The metal-ceramic substrate according to any one of claims 1 to 6, wherein the first active metal of the first solder layer (21) partially diffuses into an interface between the first solder layer (21) and the ceramic substrate layer (1) and forms an alloy. [8] The metal-ceramic substrate according to any one of claims 1 to 7, wherein the second active metal of the second solder layer (22) partially diffuses into an interface between the second solder layer (22) and the first solder layer (21) and forms an alloy. [9] The metal-ceramic substrate according to any one of claims 1 to 8, wherein the second active metal of the second solder layer (22) partially diffuses into an interface between the second solder layer (22) and the conductive metal layer (3) and forms an alloy. [10] A method for producing a metal-ceramic substrate with double solder layers, comprising: • Applying a first active metal solder paste to a ceramic substrate to thereby form a first solder layer (21) on the ceramic substrate, wherein the first active metal solder paste comprises a first active metal solder and an organic dispersion medium, and the first active metal solder comprises silver, copper, and a first active metal, wherein, based on the total weight of the first active metal solder of 100 wt.%, the silver content is in the range of 10 wt.% to 60 wt.%, • Applying a solder paste of the second active metal to the first solder layer (21) to form a second solder layer (22) on the first solder layer (21), wherein the solder paste of the second active metal comprises a solder of the second active metal and a further organic dispersion medium, wherein the solder of the second active metal contains copper and a second active metal, but no silver, and • Arranging a conductive metal layer (3) on the second solder layer (22) and implementing an active soldering process to obtain the metal-ceramic substrate with the double solder layers.

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