Method for producing an active metal ceramic substrate

Abstract

A method for manufacturing an active metal ceramic substrate comprises: applying a first solder paste, prepared by mixing a first metal solder material and a first organic medium, to a ceramic substrate and drying the first solder paste to form a first sub-solder layer (S120); applying a second solder paste, prepared by mixing a second metal solder material and a second organic medium, to the first sub-solder layer and drying the second solder paste to form a second sub-solder layer (S130); and depositing a conductive metal layer on the second sub-solder layer (S140) to thereby form the active metal ceramic substrate. The first metal solder material comprises a first active metal. The second metal solder material comprises a metal tin and a metal copper, and selectively comprises a second active metal.The first metal solder material and the second metal solder material do not contain metal silver.

Description

Cross-reference to related patent application

[0001] This application claims priority to Taiwanese patent application No. 113104571, filed on February 6, 2024. The entire contents of the above-identified application are incorporated herein by reference.

[0002] Some references, which may include patents, patent applications, and various publications, may be cited and discussed in the description of this disclosure. Citation and / or discussion of such references is provided only to explain the description of the present disclosure and is not an acknowledgment that such reference is "prior art" to the disclosure described herein. All references cited and discussed in this description are incorporated herein by reference in their entireties and to the same extent as if each reference were individually incorporated. Area of Revelation

[0003] The present disclosure relates to a method for manufacturing a metal-ceramic substrate, and more particularly to a method for manufacturing an active metal-ceramic substrate. Background of the Revelation

[0004] With the promotion of energy-saving and carbon-reduction regulations in various countries, the global electric vehicle (EV) market is currently flourishing. In recent years, as major automakers have successfully introduced 800-volt high-voltage vehicle products, demand for silicon carbide (SiC) ceramic substrate materials has grown rapidly.

[0005] However, for power devices based on silicon carbide (SiC) ceramic substrate materials, requirements for voltage, frequency, and operating temperature are continually increasing. Therefore, the ceramic substrate materials also need to be improved in terms of heat dissipation and reliability.

[0006] In the prior art, conventional direct-bonded copper (DBC) ceramic substrates are fabricated by eutectic bonding, and there is no bonding material between a copper layer and a ceramic substrate. However, during high-temperature operation, large thermal stress is often generated due to the difference in thermal expansion coefficients between the copper layer and the ceramic substrate (e.g., Al2O3 or AlN), causing the copper layer to peel off from a surface of the ceramic substrate. Therefore, conventional direct-bonded copper (DBC) ceramic substrates can no longer meet packaging requirements of high temperature, high power, high heat dissipation, and high reliability.

[0007] Currently, traditional direct-bonding copper (DBC) ceramic substrates are gradually being replaced by active metal brazing (AMB) substrate materials. Active metal elements (e.g., Ti, Zr, Ta, Nb, V, or Hf) in active metal brazing substrate materials can wet a side surface of a ceramic substrate, thereby brazing an ultra-thick copper film onto the ceramic substrate at high temperatures. A brazing layer formed between the ultra-thick copper film and the ceramic substrate by the active metal brazing process exhibits high bond strength.

[0008] Of the conventional active metal brazing paste materials, a silver-copper-titanium (Ag-Cu-Ti) metal composite material is generally used. In the aforementioned silver-copper-titanium metal composite material, the silver content usually exceeds 50 wt% (weight percentage concentration) and can even exceed 70 wt%.

[0009] The brazing temperature of conventional active metal brazing paste materials using silver-copper-titanium (Ag-Cu-Ti) metal composite materials is typically greater than 900°C (e.g., 915°C). Since the brazing layer formed from conventional active metal brazing paste materials contains a large amount of silver (i.e., a precious metal), the material and manufacturing costs of the active metal brazing ceramic substrates remain high. Furthermore, the problem of electromigration caused by silver (Ag) residues after an etching process has long been a challenge that needs to be addressed. Summary of Revelation

[0010] In response to the above-referenced technical deficiencies, the present disclosure provides a method for manufacturing an active metal ceramic substrate.

[0011] In order to solve the above-mentioned problems, one of the technical aspects employed by the present disclosure is to provide a method for manufacturing an active metal ceramic substrate.The method includes: applying a first solder paste, prepared by mixing a first metal solder material and a first organic medium, to a side surface of a ceramic substrate and drying the first solder paste to form a first sub-solder layer; applying a second solder paste, prepared by mixing a second metal solder material and a second organic medium, to a side surface of the first sub-solder layer facing away from the ceramic substrate and drying the second solder paste to form a second sub-solder layer; and depositing a conductive metal layer on a side surface of the second sub-solder layer facing away from the first sub-solder layer, thereby forming the active metal-ceramic substrate. The first metal solder material includes a first active metal and does not include silver (Ag).The thickness of the first sub-solder layer is between 1 micrometer and 10 micrometers. The second metal solder material comprises a metal tin (Sn) and a metal copper (Cu) and selectively comprises a second active metal. The second metal solder material does not comprise a metal silver (Ag). The thickness of the second sub-solder layer is between 6 micrometers and 24 micrometers.

[0012] Therefore, in the method for manufacturing the active metal ceramic substrate provided by the present disclosure, due to “applying a first solder paste to a side surface of a ceramic substrate and drying the first solder paste to form a first sub-solder layer, wherein the first solder paste is prepared by mixing a first metal solder material and a first organic medium, the first metal solder material includes a first active metal and no metal silver (Ag), and a thickness of the first sub-solder layer is between 1 micrometer and 10 micrometers” and “applying a second solder paste to a side surface of the first sub-solder layer facing away from the ceramic substrate and drying the second solder paste to form a second sub-solder layer,wherein the second solder paste is prepared by mixing a second metal solder material and a second organic medium, the second metal solder material comprises a metal tin (Sn) and a metal copper (Cu) and selectively comprises a second active metal, the second metal solder material does not comprise the metal silver (Ag), and a thickness of the second sub-solder layer is between 6 micrometers and 24 micrometers," a metal solder layer of the active metal-ceramic substrate does not use the metal silver (Ag).,

[0013] By configuring the first sub-solder layer and the second sub-solder layer in the aforementioned metal solder layer, the metal solder layer can improve the bonding strength between the ceramic substrate and the conductive metal layer. It is worth noting that since the metal solder layer does not contain silver (Ag), the electromigration problem caused by silver residues in the prior art can be effectively avoided, and manufacturing costs can be reduced.

[0014] Finally, by etching a circuit pattern on the ceramic substrate by exposure and development, the active metal ceramic substrate of the present disclosure can be used in a high-performance module for power conversion, an electric vehicle, and a charging system.

[0015] 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 legends, although variations and modifications may be effected therefrom without departing from the spirit and scope of the novel concepts of the disclosure. Brief description of the drawings

[0016] The described embodiments can be better understood by reference to the following description and the accompanying drawings, in which: Fig. 1 is a flowchart of a method for manufacturing an active metal ceramic substrate according to an embodiment of the present disclosure; Fig. 2A to 2E are schematic views showing the method for manufacturing the active metal ceramic substrate according to the embodiment of the present disclosure; and Fig.3 is a schematic view showing two metal solder layers formed on both sides of the active metal ceramic substrate, respectively, according to the embodiment of the present disclosure. Detailed description of the exemplary embodiments

[0017] The present disclosure is described in more detail in the following examples, which are intended as illustrative only, since numerous modifications and variations thereof will be apparent to those skilled in the art. Like numerals in the drawings indicate like components throughout the views. As used in the description herein and throughout the following claims, unless the context clearly requires otherwise, the meaning of "a," "an," and "the" includes a plural reference, and the meaning of "in" includes "in" and "on." Titles or subtitles may be used herein for the convenience of a reader, which is not intended to affect the scope of the present disclosure.

[0018] The terms used herein generally have their ordinary meanings in the art. In the event of a conflict, this document, including all definitions given herein, shall control. The same thing can be expressed more than one way. Alternative language and synonyms may be used for any terms discussed herein, and no particular significance is intended to be attached to whether a term is elaborated upon or discussed herein. Citation of one or more synonyms does not preclude the use of other synonyms. The use of examples in this description, including example terms, is illustrative only and in no way limits the scope and meaning of the present disclosure or any exemplified term. Likewise, the present disclosure is not limited to the various embodiments provided herein.Enumerative terms such as "first," "second," or "third" may be used to describe various components, signals, or the like, only to distinguish one component / signal from another, and are neither intended nor should be considered to place any significant limitations on the components, signals, or the like. [Method for producing an active metal ceramic substrate]

[0019] As in Fig. 1 and Fig. 2A to Fig. 2E, an embodiment of the present disclosure provides a method for manufacturing an active metal ceramic substrate, comprising a step S110, a step S120, a step S130, a step S140, and a step S150.

[0020] As in Fig. 1 and Fig.2A, step S110 includes: providing a ceramic substrate 1. The ceramic substrate 1 may be at least one of a silicon nitride (SiN) ceramic substrate, a silicon carbide (SiC) ceramic substrate, an aluminum nitride (AlN) ceramic substrate, and an aluminum oxide (Al2O3) ceramic substrate.

[0021] In the present embodiment, the ceramic substrate 1 is preferably a silicon nitride (SiN) ceramic substrate. Furthermore, a thickness T1 of the ceramic substrate 1 is between 100 micrometers and 1000 micrometers.

[0022] As in Fig. 1 and Fig.2B, step S120 includes applying a first solder paste to a side surface of the ceramic substrate 1 and drying the first solder paste at a high temperature to remove a substantial amount of an organic solvent in the first solder paste, so that the first solder paste is formed into a first sub-solder layer 2a.

[0023] The first solder paste is prepared by mixing a first metal solder material and a first organic medium. The first metal solder material comprises a first active metal and is preferably formed solely by the first active metal. Furthermore, the first solder paste does not comprise the metal silver (Ag).

[0024] In some embodiments, the first active metal can be selected from the group consisting of: titanium (Ti), zirconium (Zr), tantalum (Ta), niobium (Nb), vanadium (V), hafnium (Hf), and a metal hydride of any of the aforementioned metals. For example, the metal hydride can be selected from the group consisting of: titanium hydride (TiH2), zirconium hydride (ZrH2), tantalum hydride (TaH2), niobium hydride (NbH), vanadium hydride (VH2), and hafnium hydride (H2Hf2). Preferably, the first active metal is at least one of titanium (Ti) and titanium hydride (TiH2).

[0025] In the present embodiment, the first active metal in the form of metal powder(s) is finely dispersed in the first organic medium to thereby prepare the first solder paste.

[0026] Furthermore, the first organic medium comprises a paste-forming agent, a thixotropic agent and an organic solvent.

[0027] In the first organic medium, a weight ratio of the paste-forming agent, the thixotropic agent, and the organic solvent is 20 to 30 : 1 to 5 : 50 to 70.

[0028] 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 carboxylmethylcellulose. Preferably, the paste-forming agent is ethylcellulose.

[0029] The thixotropic agent can be selected from the group consisting of: polyamide wax, hydrogenated castor oil, and polyurea. The thixotropic agent is preferably polyamide wax.

[0030] The organic solvent can be selected from the group consisting of: ethylene glycol butyl ether acetate, diethylene glycol, triethanolamine, butyl cellosolve, tert-butanol, N,N-dimethylformamide, terpineol, and nonylphenol polyethylene glycol ether. The organic solvent is preferably terpineol or ethylene glycol butyl ether acetate.

[0031] Specifically, in the first solder paste, a weight ratio of the first metal solder material and the first organic medium is 70:30 to 95:5, and preferably, it is 80:20 to 90:10.

[0032] Preferably, the first solder paste is designed to have a viscosity between 50 mPa s and 300 mPa s (at a room temperature of 25°C) so that the first solder paste can be easily applied to the ceramic substrate 1 and mold formation can be easily achieved.

[0033] In one embodiment of the present disclosure, the first solder paste may be applied to the side surface of the ceramic substrate 1 by screen printing, and may be dried at a high temperature between 90°C and 110°C for 5 minutes to 15 minutes so that most of the organic solvent in the first solder paste is evaporated, and the first sub-solder layer 2a can be formed. A thickness T21 of the first sub-solder layer 2a is between 1 micrometer and 10 micrometers, and is preferably between 1 micrometer and 6 micrometers.

[0034] As in Fig. 1 and Fig.2C, step S130 includes applying a second solder paste to a side surface of the first sub-solder layer 2a facing away from the ceramic substrate 1, and drying the second solder paste at a high temperature to remove a substantial amount of an organic solvent in the second solder paste, so that the second solder paste is formed into a second sub-solder layer 2b.

[0035] The second solder paste is prepared by mixing a second metal solder material and a second organic medium. The second metal solder material comprises a metal tin (Sn), a metal copper (Cu), and selectively comprises a second active metal.

[0036] Preferably, the second metal solder material is composed of the metal tin (Sn), the metal copper (Cu) and the second active metal, and the second solder paste does not contain the metal silver (Ag).

[0037] In the second metal solder material, a weight ratio of the metal tin (Sn), the metal copper (Cu), and the second active metal is 20 to 50:40 to 70:0.5 to 10, and is preferably 32.5 to 42.5:52.5 to 62.5:2 to 8. For example, the weight ratio of the metal tin (Sn), the metal copper (Cu), and the second active metal is 37.5:57.5:5, but the present disclosure is not limited thereto.

[0038] In some embodiments, the second active metal can be selected from the group consisting of: titanium (Ti), zirconium (Zr), tantalum (Ta), niobium (Nb), vanadium (V), hafnium (Hf), and a metal hydride of any of the aforementioned metals. For example, the metal hydride can be selected from the group consisting of: titanium hydride (TiH2), zirconium hydride (ZrH2), tantalum hydride (TaH2), niobium hydride (NbH), vanadium hydride (VH2), and hafnium hydride (H2Hf2). Preferably, the second active metal is at least one of titanium (Ti) and titanium hydride (TiH2).

[0039] In the present embodiment, the metal tin (Sn), the metal copper (Cu) and the second active metal in the form of metal powders are finely dispersed in the second organic medium to prepare the second solder paste.

[0040] Specifically, the second organic medium includes a paste-forming agent, a thixotropic agent, and an organic solvent. In the second organic medium, the weight ratio of the paste-forming agent, the thixotropic agent, and the organic solvent is 20 to 30:1 to 5:50 to 70. The material types of the paste-forming agent, the thixotropic agent, and the organic solvent are similar to those of the first organic medium in the first solder paste and will not be repeated here.

[0041] More specifically, in the second solder paste, a weight ratio of the second metal solder material and the second organic medium is 70:30 to 95:5, and is preferably 80:20 to 90:10.

[0042] Preferably, the second solder paste is designed to have a viscosity between 50 mPa s and 300 mPa s (at a room temperature of 25°C) so that the second solder paste can be easily applied to the first sub-solder layer 2a and molding can be easily achieved.

[0043] In one embodiment of the present disclosure, the second solder paste may be applied by screen printing to the side surface of the first sub-solder layer 2a and may be dried at a high temperature between 90°C and 110°C for 5 minutes to 15 minutes so that most of the organic solvent in the second solder paste is evaporated and the second sub-solder layer 2b can be formed.

[0044] A thickness T22 of the second under-solder layer 2b is between 6 micrometers and 24 micrometers, and is preferably between 18 micrometers and 24 micrometers.

[0045] Preferably, the thickness T22 of the second sub-solder layer 2b is greater than the thickness T21 of the first sub-solder layer 2a. A thickness ratio (ie, T22 / T21) between the thickness T22 of the second sub-solder layer 2b and the thickness T21 of the first sub-solder layer 2a ranges from 1.5 to 5, preferably ranges from 2 to 4, and more preferably ranges from 2.5 to 3.5.

[0046] A metal solder layer 2 is formed together from the first sub-solder layer 2a and the second sub-solder layer 2b.

[0047] In the metal solder layer 2, based on a total weight of the first metal solder material and the second metal solder material being 100 wt% (that is, a total weight of the metal tin, the metal copper, the first active metal, and the second active metal being 100 wt%), a proportion of the metal tin ranges from 35 wt% to 70 wt%, a proportion of the metal copper ranges from 20 wt% to 65 wt%, and a total proportion of the first active metal and the second active metal ranges from 1 wt% to 20 wt%.

[0048] It is worth noting that in the embodiment of the present disclosure, the metal solder layer 2 does not include metal silver (Ag).

[0049] As in Fig.2D, step S140 includes depositing a conductive metal layer 3 on a side surface of the second sub-solder layer 2b opposite from the first sub-solder layer 2a, so that the conductive metal layer 3 can be bonded to the ceramic substrate 1 through the metal solder layer 2 formed by the first sub-solder layer 2a and the second sub-solder layer 2b, and an active metal ceramic substrate E can be formed.

[0050] The conductive metal layer 3 may be a metal copper foil, a metal aluminum foil, or a copper-aluminum alloy foil. In the present embodiment, the conductive metal layer 3 is preferably the metal copper foil. Furthermore, a thickness T3 of the conductive metal layer 3 may be, for example, between 50 micrometers and 1200 micrometers, but the present disclosure is not limited thereto.

[0051] Step S150 includes: performing a high-temperature vacuum sintering process to firmly solder the conductive metal layer 3 to the ceramic substrate 1 through the metal solder layer 2 formed by the first sub-solder layer 2a and the second sub-solder layer 2b.

[0052] An operating temperature of the high-temperature vacuum sintering process is between 600°C and 900°C and is preferably between 700°C and 900°C.

[0053] It is worth noting that in the above-mentioned high-temperature vacuum sintering process, the active metal (e.g., Ti) in the first sub-solder layer 2a can wet a surface of the ceramic substrate 1, and the active metal can react with a ceramic material (e.g., SiN) to form composites such as titanium nitride (TiN), titanium silicide (titanium silicon oxide) (TiSi), or titanium disilicate (TiSi2). In this way, the bonding strength between the conductive metal layer 3 and the ceramic substrate 1 can be improved.

[0054] In addition, when the high-temperature vacuum sintering process is performed, the metal tin (Sn) and the metal copper (Cu) in the second sub-solder layer 2b can be melted into a liquid state and react with each other, so that the conductive metal layer 3 and the ceramic substrate 1 have a good bonding strength.

[0055] For example, when the operating temperature of the high-temperature vacuum sintering process is greater than 600°C, the metal tin may first react with the metal copper to form a Cu3Sn alloy. Further, the Cu3Sn alloy may react with more of the metal tin to form a Cu6Sn5 alloy. Accordingly, the second sub-solder layer 2b can be bonded more tightly to the conductive metal layer 3, thus improving the bonding strength between the conductive metal layer 3 and the ceramic substrate 1.

[0056] According to the above configuration, the metal solder layer 2 can improve the bonding strength between the ceramic substrate 1 and the conductive metal layer 3.

[0057] It is worth mentioning that since the metal solder layer 2 does not include metal silver (Ag), a problem of electromigration caused by silver residues existing in the prior art can be effectively prevented and the manufacturing cost can be reduced.

[0058] Furthermore, in the present embodiment, the first under-solder layer 2a, the second under-solder layer 2b, and the conductive metal layer 3 are sequentially deposited on only one side surface of the ceramic substrate 1. However, the present disclosure is not limited thereto. For example, as shown in Fig.3, in another embodiment of the present disclosure, another first sub-solder layer 2a', another second sub-solder layer 2b', and another conductive metal layer 3' may also be sequentially deposited on another side surface of the ceramic substrate 1. In this way, an active metal ceramic substrate E' having the metal solder layer 2 deposited on each of both side surfaces of the ceramic substrate 1 can be formed. [Experimental data and test results]

[0059] Below, a detailed description is provided with reference to an exemplary example 1. However, the present disclosure is not limited thereto.

[0060] A provision method of Exemplary Example 1 includes: applying, according to the conditions shown in Table 1, a first solder paste comprising a first metal solder material and a first organic medium to a side surface of a ceramic substrate, and drying the first solder paste at a high temperature to form a first sub-solder layer. The first metal solder material is titanium (Ti) powder (i.e., an active metal), and a thickness of the first sub-solder layer is 6 micrometers. Furthermore, the ceramic substrate is a silicon nitride ceramic substrate. Then, a second solder paste comprising a second metal solder material and a second organic medium is applied to the first sub-solder layer and dried at a high temperature to form a second sub-solder layer.The second metal solder material includes tin (Sn) powder, copper (Cu) powder, and titanium (Ti) powder at a weight ratio of 37.5:57.5:5, and the thickness of the second sub-solder layer is 18 micrometers. In each of the first solder paste and the second solder paste, the weight ratio between the metal solder material and the organic medium is 80:20. In the organic medium, a paste-forming agent is ethyl cellulose, an organic solvent is ethylene glycol butyl ether acetate, and a thixotropic agent is polyamide wax. The weight ratio of the paste-forming agent, the organic solvent, and the thixotropic agent is 25:60:15. The first solder paste and the second solder paste do not contain any metal silver. Thereafter, a metal copper foil is further applied on the second under-solder layer to form an active metal ceramic substrate.In Exemplary Example 1, the active metal ceramic substrate is further subjected to high-temperature vacuum sintering at a brazing temperature of 855°C. Then, a temperature of the active metal ceramic substrate is lowered to room temperature, and a tensile test is performed on the active metal ceramic substrate.

[0061] The tensile force test is used to measure the tensile force between a metal copper foil and a ceramic substrate according to JIS-C-6481. The measurement temperature is 25°C. If the tensile force is greater than 100 N / cm, the bonding strength is judged to be good. If the tensile force falls within a range of 50 N / cm to 100 N / cm, the bonding strength is judged to be normal. If the tensile force is less than 50 N / cm, the bonding strength is judged to be poor. [Table 1] Objects first under-solder layer Metal composition Weight ratio (%) Thickness (µm) exemplary Ti 100 6 Example 1 (Continued from Table 1) Objects second under-solder layer Soldering temperature (°C) Tensile force (N / cm) Metal composition Weight ratio (%) Thickness (µm) exemplary example 1 Sn-Cu-Ti 37.5 : 57.5 : 5 18 855 106

[0062] From the test results shown in Table 1, the active metal ceramic substrate of Exemplary Example 1 has a tensile force of 106 N / cm and has good tensile strength.

[0063] It is worth mentioning that the active metal ceramic substrate of the above-mentioned exemplary example 1 can still exhibit good tensile strength even when the metal solder layer does not include metal silver, which is a breakthrough from the limitation of using the metal silver in an active metal layer in the prior art. [Advantageous effects of the embodiment]

[0064] Due to “applying a first solder paste to a side surface of a ceramic substrate and drying the first solder paste to form a first sub-solder layer, wherein the first solder paste is prepared by mixing a first metal solder material and a first organic medium, the first metal solder material comprises a first active metal and no metal silver (Ag), and a thickness of the first sub-solder layer is between 1 micrometer and 10 micrometers” and “applying a second solder paste to a side surface of the first sub-solder layer facing away from the ceramic substrate and drying the second solder paste to form a second sub-solder layer, wherein the second solder paste is prepared by mixing a second metal solder material and a second organic medium,the second metal solder material comprises a metal tin (Sn) and a metal copper (Cu) and selectively comprises a second active metal, the second metal solder material does not comprise a metal silver (Ag), and a thickness of the second sub-solder layer is between 6 micrometers and 24 micrometers." Finally, in the method for manufacturing the active metal ceramic substrate provided by the present disclosure, the metal solder layer of the active metal ceramic substrate does not require the use of the metal silver (Ag).

[0065] By configuring the first sub-solder layer and the second sub-solder layer in the aforementioned metal solder layer, the metal solder layer can improve the bonding strength between the ceramic substrate and the conductive metal layer. It is worth noting that since the metal solder layer does not contain silver (Ag), the problem of electromigration caused by silver residues, which exists in the prior art, can be effectively prevented, and manufacturing costs can be reduced.

[0066] Finally, by etching a circuit pattern on the ceramic substrate by exposure and development, the active metal ceramic substrate of the present disclosure can be used in a high-performance module for power conversion, an electric vehicle, and a charging system.

[0067] 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 disclosed. Many modifications and variations are possible in light of the above teachings.

[0068] The embodiments were chosen and described to explain the principles of the disclosure and their practical application, to enable others skilled in the art to utilize the disclosure and various embodiments, and with various modifications as are suited to the particular use contemplated. Alternative embodiments will become apparent to those skilled in the art to whom this disclosure is directed without departing from its spirit and scope.

[0069] In summary, a method for manufacturing an active metal ceramic substrate comprises: applying a first solder paste, prepared by mixing a first metal solder material and a first organic medium, to a ceramic substrate and drying the first solder paste to form a first sub-solder layer; applying a second solder paste, prepared by mixing a second metal solder material and a second organic medium, to the first sub-solder layer and drying the second solder paste to form a second sub-solder layer; and depositing a conductive metal layer on the second sub-solder layer to thereby form the active metal ceramic substrate. The first metal solder material comprises a first active metal. The second metal solder material comprises a metal tin and a metal copper and selectively comprises a second active metal.The first metal solder material and the second metal solder material do not contain metal silver. List of reference symbols E, E' active metal ceramic substrate 1 ceramic substrate 2 metal solder layer 2a, 2a' first under-solder layer 2b, 2b' second under-solder layer 3, 3' conductive metal layer T1, T21, T22, T3 thickness

Claims

[1] A method for producing an active metal ceramic substrate (E), comprising: Applying a first solder paste, prepared by mixing a first metal solder material and a first organic medium, to a side surface of a ceramic substrate (1) and drying the first solder paste to form a first sub-solder layer (2a) (S120); wherein the first metal solder material comprises a first active metal and does not comprise silver (Ag); wherein a thickness of the first sub-solder layer is between 1 micrometer and 10 micrometers; Applying a second solder paste, prepared by mixing a second metal solder material and a second organic medium, to a side surface of the first sub-solder layer (2a) facing away from the ceramic substrate (1), and drying the second solder paste to form a second sub-solder layer (2b) (S130); wherein the second metal solder material comprises a metal tin (Sn) and a metal copper (Cu) and selectively comprises a second active metal, and the second metal solder material does not comprise a metal silver (Ag); wherein a thickness of the second sub-solder layer is between 6 micrometers and 24 micrometers; and Applying a conductive metal layer (3) to a side surface of the second under-solder layer (2b) facing away from the first under-solder layer (2a) so as to form the active metal ceramic substrate (E) (S140). [2] The method according to claim 1, further comprising: performing a high-temperature vacuum sintering process to solder (S150) the conductive metal layer (3) to the ceramic substrate (1) through the first under-solder layer (2a) and the second under-solder layer (2b). [3] The method according to claim 2, wherein an operating temperature of the high-temperature vacuum sintering process is between 600°C and 900°C. [4] The method according to any one of claims 1 to 3, wherein the thickness of the second sub-solder layer (2b) is greater than the thickness of the first sub-solder layer (2a) and a thickness ratio between the second sub-solder layer (2b) and the first sub-solder layer (2a) ranges from 1.5 to 5. [5] A method according to any one of claims 1 to 4, wherein the thickness of the first sub-solder layer (2a) is between 1 micrometer and 6 micrometers and the thickness of the second sub-solder layer (2b) is between 18 micrometers and 24 micrometers. [6] The method according to any one of claims 1 to 5, wherein the first active metal is selected from the group consisting of titanium (Ti), zirconium (Zr), tantalum (Ta), niobium (Nb), vanadium (V), hafnium (Hf), titanium hydride (TiH2), zirconium hydride (ZrH2), tantalum hydride (TaH2), niobium hydride (NbH), vanadium hydride (VH2) and hafnium hydride (H2Hf2), and the second active metal is selected from the group consisting of titanium (Ti), zirconium (Zr), tantalum (Ta), niobium (Nb), vanadium (V), hafnium (Hf), titanium hydride (TiH2), zirconium hydride (ZrH2), tantalum hydride (TaH2), niobium hydride (NbH), vanadium hydride (VH2) and hafnium hydride (H2Hf2). [7] A method according to any one of claims 1 to 6, wherein the first solder paste has a viscosity between 50 mPa s and 300 mPa s and the second solder paste has a viscosity between 50 mPa s and 300 mPa s. [8] The method according to any one of claims 1 to 7, wherein in the first solder paste, the first metal solder material is formed only by the active metal, the first organic medium comprises a paste forming agent, a thixotropic agent and an organic solvent, and a weight ratio of the paste forming agent, the thixotropic agent and the organic solvent is 20 to 30 : 1 to 5 : 50 to 70. [9] The method according to any one of claims 1 to 8, wherein in the second solder paste, the second metal solder material is formed by the metal tin (Sn), the metal copper (Cu), and the second active metal, and a weight ratio of the metal tin (Sn), the metal copper (Cu), and the second active metal is 20 to 50 : 40 to 70 : 0.5 to 10; wherein the second organic medium comprises a paste-forming agent, a thixotropic agent, and an organic solvent, and a weight ratio of the paste-forming agent, the thixotropic agent, and the organic solvent is 20 to 30 : 1 to 5 : 50 to 70. [10] The method according to claim 9, wherein in the second metal solder material, the weight ratio of the metal tin (Sn), the metal copper (Cu) and the second active metal is 32.5 to 42.5 : 52.5 to 62.5 : 2 to 8.

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