Active metal brazing substrate and manufacturing method thereof

Abstract

The invention discloses an active metal brazing substrate and a manufacturing method thereof. The active metal brazing substrate comprises a ceramic substrate layer, an active metal layer and a conductive metal layer. The active metal layer is arranged between the ceramic substrate layer and the conductive metal layer. The active metal layer is formed by an active metal solder and an organic dispersion medium, the active metal solder comprises metal silver, metal copper and active metal, and the content of the metal silver is 10-60 weight percent based on the total weight of the active metal solder being 100 weight percent. The tensile strength of the active metal brazing substrate is 165 N / cm to 270 N / cm.

Description

Technical Field

[0001] The present application relates to the field of active metal brazing, and in particular to an active metal brazing substrate with good bonding strength and a manufacturing method thereof. Background Art

[0002] Driven by the energy-saving and carbon-reduction policies of various countries, the global electric vehicle market is booming. As major car manufacturers have launched 800-volt high-voltage models in recent years, the demand for silicon carbide (SiC) ceramic substrate materials has grown rapidly.

[0003] However, as the voltage, frequency and operating temperature requirements of power components made of silicon carbide (SiC) ceramic substrate materials continue to increase, the ceramic substrate materials also need to have better heat dissipation capabilities and reliability.

[0004] The widely used direct-bonding-copper (DBC) ceramic substrate is made by eutectic bonding, and there is no bonding material between the copper layer and the ceramic substrate. However, during high-temperature operation, the copper layer and the ceramic substrate (such as Al 2 O 3 The thermal expansion coefficients of the copper and AlN substrates are different, which results in large thermal stress, causing the copper layer to peel off from the surface of the ceramic substrate. Therefore, the traditional direct copper-clad ceramic substrate has been unable to meet the packaging requirements of high temperature, high power, high heat dissipation, and high reliability.

[0005] Currently, the mainstream substrate materials are gradually shifting from direct copper-clad ceramic substrates to active metal brazing (AMB) substrate materials.

[0006] Common active metal brazing substrate materials usually contain metallic silver. The silver content in active metal brazing substrate materials is usually more than 50% (weight percentage concentration), and even up to 70%. However, the high content of silver leads to high material costs for active metal brazing ceramic substrates, and there is a concern that the silver in the solder layer will electromigrate.

[0007] Therefore, how to reduce the silver content in the solder layer by improving the composition and structural design to overcome the above-mentioned defects has become one of the important issues that this business wants to solve. Summary of the invention

[0008] The technical problem to be solved by the present application is to provide an active metal brazing substrate and a manufacturing method thereof in view of the deficiencies in the prior art.

[0009] In order to solve the above technical problems, one of the technical solutions adopted in the present application is to provide an active metal brazing substrate. The active metal brazing substrate includes a ceramic substrate layer, an active metal layer and a conductive metal layer. The active metal layer is arranged between the ceramic substrate layer and the conductive metal layer. The active metal layer is formed by an active metal solder and an organic dispersion medium, and the active metal solder includes metallic silver, metallic copper and active metal, and the total weight of the active metal solder is 100 weight percent, and the content of metallic silver is 10 weight percent to 60 weight percent. The tensile strength of the active metal brazing substrate is 165N / cm to 270N / cm.

[0010] In order to solve the above technical problems, another technical solution adopted by the present application is to provide a method for manufacturing an active metal brazing substrate. The method for manufacturing the active metal brazing substrate comprises: coating an active metal solder paste on a ceramic substrate to form an active metal layer on the ceramic substrate; and arranging a conductive metal layer on the active metal layer, performing a brazing process to obtain the active metal brazing substrate. The active metal solder paste comprises an active metal solder and an organic dispersion medium, the active metal solder comprises metallic silver, metallic copper and active metal, the total weight of the active metal solder being 100 weight percent, and the content of metallic silver being 10 weight percent to 60 weight percent. The tensile strength of the active metal brazing substrate is 165N / cm to 270N / cm.

[0011] One of the beneficial effects of the present application is that the active metal brazing substrate and the manufacturing method thereof provided in the present application can enhance the bonding strength between the ceramic substrate layer and the conductive metal layer through the technical scheme of "the active metal solder includes metallic silver, metallic copper and active metal" and "the total weight of the active metal solder is 100 weight percent, and the content of metallic silver is 10 weight percent to 60 weight percent".

[0012] To further understand the features and technical contents of the present application, please refer to the following detailed description and drawings of the present application. However, the drawings provided are only for reference and illustration and are not intended to limit the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 It is a schematic side view of the active metal brazing substrate of the present application.

[0014] Figure 2 FIG. 1 is a schematic side view of an active metal brazing substrate according to another embodiment of the present application. DETAILED DESCRIPTION

[0015] The following is an explanation of the implementation methods of the "active metal brazing substrate and its manufacturing method" disclosed in the present application through specific examples. Those skilled in the art can understand the advantages and effects of the present application from the contents disclosed in this specification. The present application can be implemented or applied through other different specific embodiments, and the details in this specification can also be modified and changed in various ways based on different viewpoints and applications without departing from the concept of the present application. In addition, the drawings of the present application are only simple schematic illustrations and are not depicted according to actual dimensions. It is stated in advance. The following implementation methods will further explain the relevant technical contents of the present application in detail, but the disclosed contents are not intended to limit the scope of protection of the present application. In addition, the term "or" used in this article may include any one or more combinations of the associated listed items depending on the actual situation.

[0016] In order to overcome the problem that the copper layer of the traditional direct copper-clad ceramic substrate is easily peeled off from the ceramic substrate due to the difference in thermal expansion coefficient, the present application provides an active metal brazing substrate. In the active metal brazing substrate, the use of active metal solder paste enables good bonding between the copper layer and the ceramic substrate. Therefore, the active metal brazing substrate can be applied to some packaging structures with high temperature, high power and high reliability requirements. In the specification, for the convenience of comparison, the bonding force between the copper layer and the ceramic substrate is quantified as the tensile strength of the active metal brazing substrate.

[0017] See also Figure 1 As shown, the active metal brazing substrate of the present application comprises: 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 achieve the effect of combining the ceramic substrate layer 1 and the conductive metal layer 3.

[0018] exist Figure 1 In the embodiment, the ceramic substrate layer 1 is provided with the active metal layer 2 and the conductive metal layer 3 on only one side, but the active metal brazing substrate of the present application is not limited thereto. The ceramic substrate layer 1 may also be provided with the active metal layer 2 and the conductive metal layer 3 on both opposite sides. Figure 2 shown.

[0019] See also Figure 2 As shown, the active metal brazing substrate may have a symmetrical structure, with active metal layers 2, 2' and conductive metal layers 3, 3' respectively disposed on opposite sides of the ceramic substrate layer 1. Thus, the active metal brazing substrate may be used to manufacture a packaging structure with a double-sided conductive layer.

[0020] The ceramic substrate layer 1 may be a silicon nitride (SiN) ceramic substrate, a silicon carbide (SiC) ceramic substrate, an aluminum nitride (AlN) ceramic substrate or an aluminum oxide (Al 2 O 3) a ceramic substrate, preferably a silicon-containing ceramic substrate, more preferably a silicon nitride ceramic substrate. In addition, the thickness of the ceramic substrate layer 1 can be 100 microns to 1000 microns, but the present application is not limited thereto.

[0021] Active metal layer

[0022] The active metal layer 2 is formed by an active metal solder and an organic dispersion medium.

[0023] The active metal solder includes metal silver (Ag), metal copper (Cu) and active metal.

[0024] Taking the total weight of the active metal solder as 100 weight percent, the content of metallic silver is 10 weight percent to 60 weight percent. It can be seen that the silver content in the active metal solder of the present application is relatively low, so the material cost of the active metal brazing substrate can be reduced, and the probability of electromigration of metallic silver can also be reduced.

[0025] Specifically, the content of metallic silver may be 15 weight percent, 20 weight percent, 25 weight percent, 30 weight percent, 35 weight percent, 40 weight percent, 45 weight percent, 50 weight percent or 55 weight percent.

[0026] In some embodiments, the content of metallic silver is 30 weight percent to 50 weight percent. In other embodiments, the content of metallic silver is 10 weight percent to 20 weight percent. When the content of metallic silver changes, the content of metallic copper and active metal and the brazing temperature need to be adjusted accordingly to maintain good bonding between the ceramic substrate layer 1 and the conductive metal layer 3.

[0027] During the vacuum sintering process, metallic silver may diffuse into the conductive metal layer 3 and react with copper atoms in the conductive metal layer 3 at the interface between the active metal layer 2 and the conductive metal layer 3 to form a silver-copper alloy.

[0028] In an exemplary embodiment, the total weight of the active metal solder is 100 weight percent, the content of metal copper is 30 weight percent to 80 weight percent, and the content of the active metal is 1 weight percent to 10 weight percent.

[0029] Specifically, the content of metallic copper may be 35 weight percent, 40 weight percent, 45 weight percent, 50 weight percent, 55 weight percent, 60 weight percent, 65 weight percent, 70 weight percent or 75 weight percent.

[0030] Specifically, the content of the active metal can be 2 weight percent, 4 weight percent, 6 weight percent or 8 weight percent. Preferably, the total weight of the active metal solder is 100 weight percent, and the content of the active metal is 2 weight percent to 4 weight percent.

[0031] It is worth mentioning that the active metal has a low melting point and will preferentially form a molten state during the vacuum sintering process, so it can help fill the defects in the ceramic substrate layer 1 or the conductive metal layer 3, and even react with the ceramic substrate layer 1. On the other hand, the addition of the active metal can also reduce the electrical impedance of the active metal layer 2.

[0032] Specifically, the active metal is selected from the group consisting of metal titanium (Ti), metal zirconium (Zr), metal tantalum (Ta), metal niobium (Nb), metal vanadium (V) and metal hafnium (Hf).

[0033] During the vacuum sintering process, a portion of the active metal can diffuse to the interface between the active metal layer 2 and the ceramic substrate layer 1, and form metal silicide or metal nitride with silicon atoms or nitrogen atoms in the ceramic substrate layer 1. Similarly, a portion of the active metal can also diffuse to the interface between the active metal layer 2 and the conductive metal layer 3 to react and form an alloy. In this way, the ceramic substrate layer 1 and the conductive metal layer 3 can have a good bonding effect.

[0034] In a preferred embodiment, the active metal is titanium. For example, during the vacuum sintering process, after the titanium diffuses into the ceramic substrate layer 1, it can form titanium silicide (TiSi) or silicon nitride (TiN) or titanium disilicide (TiSi 2 In addition, after the metal titanium diffuses into the conductive metal layer 3, it can form a titanium-copper alloy with the copper atoms in the conductive metal layer 3, but the present application is not limited thereto.

[0035] In addition, when the thickness of the active metal layer 2 is too thin, the bonding force between the ceramic substrate layer 1 and the conductive metal layer 3 will decrease; when the thickness of the active metal layer 2 is too thick, the material cost of the active metal layer 2 is too high, which is not conducive to mass production. Therefore, the thickness of the active metal layer 2 is greater than or equal to 6 microns, and the thickness of the active metal layer 2 is 10 microns to 30 microns. For example, the thickness of the active metal layer 2 can be 12 microns, 14 microns, 16 microns, 18 microns, 20 microns, 22 microns, 24 microns, 26 microns or 28 microns. Preferably, the thickness of the active metal layer 2 is 18 microns to 24 microns.

[0036] Conductive metal layer

[0037] The conductive metal layer 3 is disposed on the ceramic substrate layer 1 through the active metal layer 2. Specifically, the conductive metal layer 3 can be a metal copper foil, a metal aluminum foil or a copper-aluminum alloy foil. In a preferred embodiment, the conductive metal layer 3 is preferably a metal copper foil.

[0038] In addition, the thickness of the conductive metal layer 3 may be 50 micrometers to 1200 micrometers. Preferably, the thickness of the conductive metal layer 3 may be 200 micrometers to 800 micrometers, but the present application is not limited thereto.

[0039] Method for manufacturing active metal brazing substrate

[0040] In step S1 , an active metal solder paste is prepared first. The active metal solder paste is used to form the active metal layer 2 mentioned above.

[0041] The active metal solder paste contains the active metal solder and an organic dispersion medium.

[0042] The active metal solder includes the aforementioned metallic silver, metallic copper and active metal. In some embodiments, the active metal solder is a combination of metallic silver powder, metallic copper powder and active metal powder. In other embodiments, the active metal solder may also be a combination of at least one of metallic silver powder, metallic copper powder and silver-copper alloy powder and active metal powder.

[0043] As mentioned above, the metallic silver content in the active metal solder is 10 weight percent to 60 weight percent (based on the total weight of the active metal solder being 100 weight percent).

[0044] The organic dispersion medium can help disperse the active metal solder and help the active metal solder paste to be shaped to form the active metal layer 2. Specifically, the organic dispersion medium includes a paste-forming agent, an organic solvent and a thixotropic agent. With the total weight of the organic dispersion medium being 100 weight percent, the content of the paste-forming agent is 20 weight percent to 30 weight percent, the content of the organic solvent is 50 weight percent to 70 weight percent, and the content of the thixotropic agent is 1 weight percent to 5 weight percent.

[0045] For example, the paste-forming agent may be selected from the group consisting of silicone oil, white oil, polyvinyl alcohol, acrylic resin, nitrocellulose, ethyl cellulose, dimethyl phthalate and carboxymethyl cellulose. Preferably, the paste-forming agent is ethyl cellulose.

[0046] The organic solvent may be selected from the group consisting of ethylene glycol butyl ether acetate, diethylene glycol, triethanolamine, butyl cellosolve, tert-butyl alcohol, N,N-dimethylformamide, terpineol and nonylphenol polyglycol ether. Preferably, the organic solvent is terpineol or ethylene glycol butyl ether acetate.

[0047] The thixotropic agent may be selected from the group consisting of polyamide wax, hydrogenated castor oil and polyurea. Preferably, the thixotropic agent is polyamide wax.

[0048] The active metal solder and the organic dispersion medium are mixed in a weight ratio of 70% to 95%: 5% to 30% to form an active metal solder paste having a viscosity of 50 mPa·s to 300 mPa·s. Preferably, the weight ratio of the active metal solder to the organic dispersion medium is 75% to 90%: 10% to 25%.

[0049] However, the present application is not limited to the above-mentioned implementation mode. As long as the active solder powder and the organic component can be mixed into an active solder paste with a viscosity suitable for coating on the ceramic substrate layer 1 to facilitate the formation of the active metal layer 2, it complies with the protection spirit of the present application and falls within the protection scope of the present application.

[0050] In step S2 , the active metal solder paste can be coated on the ceramic substrate layer 1 by screen printing, and dried at a temperature of 90° C. to 110° C. for 5 to 15 minutes to volatilize most of the organic solvent in the active metal solder paste, thereby forming an active metal layer 2 .

[0051] In step S3 , the conductive metal layer 3 is disposed on the active metal layer 2 , and a brazing process is performed to fix the conductive metal layer 3 on the ceramic substrate layer 1 .

[0052] The brazing process includes a first stage heat treatment process and a second stage heat treatment process, which can be performed in a vacuum environment. The temperature condition of the first stage heat treatment process is not greater than 500°C, and the temperature condition of the second stage heat treatment process is 900°C to 1100°C (i.e., the brazing temperature range), and the temperature of the second stage heat treatment process is higher than the temperature of the first stage heat treatment process.

[0053] More specifically, the temperature condition of the first stage heat treatment process is between 300°C and 500°C, and the treatment time is between 30 minutes and 60 minutes. The temperature condition of the second stage heat treatment process is between 900°C and 1100°C, and the treatment time is between 60 minutes and 240 minutes. In addition, the heating rate of the above heat treatment process can be, for example, 5°C / min to 30°C / min. The cooling rate after the vacuum high temperature sintering is completed can be, for example, 2°C / min to 30°C / min.

[0054] It is worth noting that the brazing temperature in the brazing procedure is adjusted according to the difference in the silver content in the active metal layer 2 so that the active metal brazing substrate has good tensile strength. Specifically, when the content of metallic silver in the active metal solder is 30 weight percent to 50 weight percent, the brazing temperature in the brazing procedure can be 900° C. to 950° C. When the content of metallic silver in the active metal solder is 10 weight percent to 20 weight percent, the brazing temperature in the brazing procedure can be 1000° C. to 1100° C.

[0055] During the brazing process, part of the organic dispersion medium will vaporize, and the active metal will wet the surface of the ceramic substrate layer 1 and react with the ceramic substrate layer 1 to enhance the bonding strength between the active metal layer 2 and the ceramic substrate layer 1. In addition, the metal components of the active metal and the conductive metal layer 3 undergo a micron-scale eutectic reaction at the interface to form a strong eutectic structure, so that the active metal layer 2 can be tightly bonded to the conductive metal layer 3.

[0056] Test cases 1 to 10

[0057] In order to compare the effects of the silver content in the active metal layer 2, the brazing temperature and the thickness of the active metal layer 2 on the tensile strength of the active metal brazing substrate, metal brazing substrates of Test Examples 1 to 10 were prepared according to the above steps S1 to S3.

[0058] In the metal brazing substrates of test examples 1 to 10, the ceramic substrate layer 1 is a silicon nitride ceramic substrate, the active metal layer 2 includes metal silver, metal copper and metal titanium, and the conductive metal layer 3 is a copper metal layer.

[0059] When preparing active metal solder paste, ethyl cellulose is used as a paste-forming agent, ethylene glycol butyl ether acetate is used as an organic solvent, and polyamide wax is used as a thixotropic agent. Taking the total weight of the organic dispersion medium as 100 weight percent, the organic dispersion medium includes 20 weight percent to 30 weight percent of the paste-forming agent, 50 weight percent to 70 weight percent of the organic solvent, and 1 weight percent to 5 weight percent of the thixotropic agent.

[0060] The specific content of metallic silver in the active metal solder paste (active metal layer 2), the brazing temperature in the brazing process, and the thickness of the active metal layer 2 formed after the brazing process are listed in Table 1. In addition, the tensile strength of the active metal brazed substrate was measured at a temperature of 25°C according to JIS-C-6481 standard, and the results are listed in Table 1.

[0061] Table 1

[0062]

[0063] According to the results in Table 1, when the silver content in the active metal layer is 10 weight percent to 60 weight percent, the tensile strength of the active metal brazing substrate can be 165 N / cm to 270 N / cm. According to Test Examples 1 to 4, when the silver content in the active metal layer is 20 weight percent to 50 weight percent, the tensile strength of the active metal brazing substrate can be 180 N / cm to 270 N / cm.

[0064] Even if the thickness of the active metal layer is reduced to 18 micrometers, the tensile strength of the active metal brazing substrate can still have a similar effect. According to Test Examples 5 to 7, when the silver content in the active metal layer is 20 weight percent to 50 weight percent, the active metal brazing substrate can still have a tensile strength of 180 N / cm to 270 N / cm.

[0065] According to experiments, when the brazing temperature is increased, the tensile strength of the active metal brazing substrate is greatly improved. According to test examples 8 to 9, when the brazing temperature is increased to 1015°C, even if the silver content in the active metal layer is only 10 weight percent to 20 weight percent, the active metal brazing substrate can still have a tensile strength of 140N / cm to 250N / cm.

[0066] According to the above results, by adjusting the silver content in the active metal and the brazing temperature, the active metal brazing substrate of the present application can have good tensile strength and can be applied to some packaging structures with high temperature, high power and high reliability requirements.

[0067] Advantageous Effects of Embodiments

[0068] One of the beneficial effects of the present application is that the active metal brazing substrate and the manufacturing method thereof provided in the present application can enhance the bonding strength between the ceramic substrate layer and the conductive metal layer through the technical scheme of "the active metal solder includes metallic silver, metallic copper and active metal" and "the total weight of the active metal solder is 100 weight percent, and the content of metallic silver is 10 weight percent to 60 weight percent".

[0069] The contents disclosed above are only preferred feasible embodiments of the present application, and are not intended to limit the protection scope of the claims of the present application. Therefore, all equivalent technical changes made using the contents of the present application specification and drawings are included in the protection scope of the claims of the present application.

Claims

1. An active metal brazing substrate, It is characterized in that The active metal brazing substrate comprises: a ceramic substrate layer; an active metal layer, which is formed by an active metal solder and an organic dispersion medium, wherein the active metal solder includes metal silver (Ag), metal copper (Cu) and active metal, and the content of the metal silver is 10 weight percent to 60 weight percent based on the total weight of the active metal solder being 100 weight percent; and a conductive metal layer, wherein the active metal layer is disposed between the ceramic substrate layer and the conductive metal layer; Wherein, the tensile strength of the active metal brazing substrate is 165N / cm to 270N / cm.

2. The active metal brazing substrate according to claim 1, It is characterized in that Taking the total weight of the active metal solder as 100 weight percent, the content of the metal silver is 30 weight percent to 50 weight percent.

3. The active metal brazing substrate according to claim 1, It is characterized in that Taking the total weight of the active metal solder as 100 weight percent, the content of the metal silver is 10 weight percent to 20 weight percent.

4. The active metal brazing substrate according to claim 1, It is characterized in that Taking the total weight of the active metal solder as 100 weight percent, the content of the active metal is 2 weight percent to 4 weight percent.

5. The active metal brazing substrate according to claim 1, It is characterized in that The active metal is selected from the group consisting of: titanium (Ti), zirconium (Zr), tantalum (Ta), niobium (Nb), vanadium (V) and hafnium (Hf).

6. The active metal brazing substrate according to claim 1, It is characterized in that The thickness of the active metal layer is greater than or equal to 6 microns.

7. The active metal brazing substrate according to claim 6, It is characterized in that The thickness of the active metal layer is 18 micrometers to 24 micrometers.

8. A method for manufacturing an active metal brazing substrate, It is characterized in that The manufacturing method comprises: An active metal solder paste is coated on a ceramic substrate to form an active metal layer on the ceramic substrate; wherein the active metal solder paste comprises an active metal solder and an organic dispersion medium, the active metal solder comprises metal silver (Ag), metal copper (Cu) and active metal, and the content of the metal silver is 10 weight percent to 60 weight percent based on the total weight of the active metal solder being 100 weight percent; and A conductive metal layer is disposed on the active metal layer, and a brazing process is performed to obtain an active metal brazing substrate; wherein the tensile strength of the active metal brazing substrate is 165N / cm to 270N / cm.

9. The method for manufacturing an active metal brazing substrate according to claim 8, It is characterized in that Taking the total weight of the active metal solder as 100 weight percent, the content of the metal silver is 30 weight percent to 50 weight percent; the brazing temperature in the brazing process is 900° C. to 950° C.

10. The method for manufacturing an active metal brazing substrate according to claim 8, It is characterized in that Taking the total weight of the active metal solder as 100 weight percent, the content of the metal silver is 10 weight percent to 20 weight percent; the brazing temperature in the brazing process is 1000° C. to 1100° C.

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