Ceramic copper coating method

Abstract

The invention discloses a ceramic copper coating method which comprises the following steps: S1, performing surface etching treatment on a ceramic substrate to obtain a pretreated ceramic substrate; s2, a copper substrate is taken to be subjected to surface treatment, a copper nanocone array is formed on one face of the copper substrate, and a pretreated copper substrate is obtained; and S3, sequentially stacking the graphene sponge, the AgCuTi foil, the graphene sponge and the pretreated copper substrate on the surface of the pretreated ceramic substrate, enabling the surface with the copper nanocone array to be in contact with the graphene sponge, and then welding to obtain a ceramic copper-clad product. The ceramic copper-clad product prepared by the method disclosed by the invention has good bonding strength and cold and heat cycle resistance.

Description

Technical Field

[0001] The invention relates to the technical field of electronic packaging, and in particular to a method for copper coating ceramics. Background Art

[0002] For electronic packaging, the packaging substrate plays a key role in connecting the upper and lower parts and connecting the internal and external heat dissipation channels. It also has functions such as electrical interconnection and mechanical support. For the ceramic substrate, it is not conductive in itself, so it needs to be copper-clad to meet the electrical interconnection requirements. In the copper-cladding process, compared with DPC (direct electroplating ceramic substrate) and DBC (direct bonding ceramic substrate), AMB (active metal welding ceramic substrate) process research shows a large growth trend and is a research hotspot in various countries.

[0003] The main process of AMB is to place silver-copper-titanium solder sheets or print silver-copper-titanium solder paste between oxygen-free copper sheets and ceramic plates, and then perform brazing in a high vacuum environment. However, due to the large difference in thermal expansion coefficients between ceramics and copper sheets, large residual stress is easily generated at the joints, which leads to joint failure. It is necessary to improve the bonding strength and resistance to cold and hot cycles of the joints. Summary of the invention

[0004] Based on the technical problems existing in the background technology, the present invention proposes a method for copper-clad ceramics. The copper-clad ceramics product prepared by the method of the present invention has good bonding strength and resistance to cold and hot cycles.

[0005] The present invention provides a method for copper coating ceramics, comprising the following steps:

[0006] S1, taking a ceramic substrate and performing surface etching treatment to obtain a pretreated ceramic substrate;

[0007] S2, taking a copper substrate and performing surface treatment to form a copper nanocone array on one side of the copper substrate to obtain a pretreated copper substrate;

[0008] S3. Stacking graphene sponge, AgCuTi foil, graphene sponge, and pretreated copper substrate in sequence on the surface of the pretreated ceramic substrate, and making the side with the copper nanocone array contact with the graphene sponge, and then welding to obtain a ceramic copper-clad product.

[0009] In the above S3, graphene sponge, AgCuTi foil, graphene sponge, and pretreated copper substrate may be stacked in sequence on one or both sides of the pretreated ceramic substrate, and the side with the copper nanocone array is in contact with the graphene sponge.

[0010] Preferably, in S1, the material of the ceramic matrix is ​​AlN ceramic.

[0011] Preferably, in S1, the ceramic substrate is etched with an aqueous sodium hydroxide solution.

[0012] Preferably, the concentration of the sodium hydroxide aqueous solution is 0.1-0.2 mol / L.

[0013] Preferably, in S1, etching is performed at room temperature for 20-25 minutes.

[0014] Preferably, in S2, in the copper nanocone array, the copper nanocones have a width of 15-25 μm and a depth of 8-12 μm.

[0015] Preferably, in S2, a surface of the copper substrate is subjected to femtosecond laser treatment to form a copper nanocone array on one side of the copper substrate.

[0016] Preferably, during femtosecond laser processing, the laser power is 180-220 mW, the scanning interval is 25-30 μm, and the scanning speed is 1400-1500 μm / s.

[0017] Preferably, in S3, the AgCuTi foil contains nano-TiB2.

[0018] Preferably, in the AgCuTi foil, the Cu content is 26-27wt%, the Ti content is 4-5wt%, and the nano-TiB2 content is 1-1.5wt%.

[0019] Preferably, in S3, the preparation method of the graphene sponge comprises: mixing nano-TiB2 and graphene oxide dispersion, freezing and solidifying, freeze-drying to obtain a sponge intermediate, and then reducing the sponge intermediate with hydrazine hydrate vapor to obtain a graphene sponge.

[0020] The present invention evenly disperses nano-TiB2 and graphene oxide, and the hydroxyl groups on the surface of nano-TiB2 can combine with the active groups (carboxyl groups, epoxy groups, etc.) in graphene oxide, so that nano-TiB2 is evenly dispersed on the graphene surface, and then an ice template method and hydrazine hydrate are used to obtain a graphene sponge with evenly distributed nano-TiB2.

[0021] Preferably, the mass fraction of the graphene oxide dispersion is 2-4wt%.

[0022] Preferably, the solidification is carried out by freezing at -10 to -30°C.

[0023] Preferably, freeze-drying is performed at -30 to -50°C.

[0024] Preferably, the weight ratio of nano-TiB2 to graphene oxide is 0.2-0.4:10.

[0025] Preferably, in S3, the vacuum degree during welding is 1.5×10 -3 -2.5×10 -3 Pa, the applied pressure is 4-6MPa.

[0026] Preferably, in S3, the welding temperature is 780-800°C, and the welding time is 30-40 minutes.

[0027] The present invention first performs surface treatment on a ceramic substrate and a copper substrate so that the substrate surface has a micro-nano structure, and then sequentially stacks a graphene sponge, an AgCuTi foil, a graphene sponge, and a pretreated copper substrate on the surface of the pretreated ceramic substrate for welding, wherein the AgCuTi foil melts into the graphene sponge and penetrates into the micro-nano structure on the substrate surface to achieve mechanical interlocking and metallurgical bonding, thereby greatly improving the bonding strength of the joint;

[0028] The appropriate amount of nano-TiB2 whiskers in the AgCuTi foil can cooperate with the graphene sponge and the nano-TiB2 whiskers therein to form a specific combined structure, and can reduce the thermal expansion coefficient and maintain a high thermal conductivity, thereby greatly relieving the residual stress of the joint organization, so that the welded joint has good bonding strength and resistance to cold and hot cycles; and the graphene sponge and the nano-TiB2 whiskers therein, the AgCuTi organization and the nano-TiB2 whiskers therein cooperate with each other, so that a strong three-dimensional network structure is formed between the ceramic matrix and the copper matrix, which greatly improves the bonding strength of the joint and the performance of relieving residual stress;

[0029] Moreover, graphene can also prevent oxidation of the copper substrate at the welding point, thereby improving the bonding strength of the base joint; in addition, the present invention selects a suitable welding process to reduce the porosity of the joint structure and further improve the bonding strength of the joint. DETAILED DESCRIPTION

[0030] The technical solution of the present invention is described in detail below through specific embodiments.

[0031] Example 1

[0032] A method for copper coating ceramics comprises the following steps:

[0033] S1, taking an AlN ceramic substrate and adding it into a 0.1 mol / L sodium hydroxide aqueous solution, stirring and etching at room temperature for 25 min, then washing with water and drying to obtain a pretreated ceramic substrate;

[0034] S2, taking an oxygen-free copper substrate, cleaning it to remove oil stains and an oxide layer, and then treating it with a femtosecond laser (the laser power during the femtosecond laser treatment is 220 mW, the scanning interval is 25 μm, and the scanning speed is 1500 μm / s) to form a copper nanocone array on one side of the copper substrate to obtain a pretreated copper substrate, wherein the copper nanocone array has a width of 25 μm and a depth of 12 μm;

[0035] S3, according to the weight ratio of nano-TiB2 to graphene oxide of 0.2-0.4:10, nano-TiB2 and a graphene oxide aqueous dispersion with a mass fraction of 2-4wt% are mixed, frozen and solidified at -10 to -30°C, and freeze-dried at -30 to -50°C to obtain a sponge intermediate, and then the sponge intermediate is reduced with hydrazine hydrate vapor, and cut into sheets with a thickness of 5mm to obtain a graphene sponge;

[0036] Graphene sponge, AgCuTi foil, graphene sponge, and pretreated copper substrate were stacked on the surface of the pretreated ceramic substrate in sequence, and the side with the copper nanocone array was in contact with the graphene sponge. The vacuum degree was adjusted to 1.5×10 -3 Pa, the applied pressure is 6MPa, the welding is carried out at 780℃ for 40min, and then cooled in the furnace to obtain a ceramic copper-clad product;

[0037] The AgCuTi foil contains nano-TiB2, wherein the Cu content is 26wt%, the Ti content is 5wt%, and the nano-TiB2 content is 1wt%.

[0038] Example 2

[0039] A method for copper coating ceramics comprises the following steps:

[0040] S1, taking an AlN ceramic substrate and adding it into a 0.2 mol / L sodium hydroxide aqueous solution, stirring and etching at room temperature for 20 min, then washing with water and drying to obtain a pretreated ceramic substrate;

[0041] S2, taking an oxygen-free copper substrate, cleaning it to remove oil stains and an oxide layer, and then treating it with a femtosecond laser (the laser power during the femtosecond laser treatment is 180 mW, the scanning interval is 30 μm, and the scanning speed is 1400 μm / s) to form a copper nanocone array on one side of the copper substrate to obtain a pretreated copper substrate, wherein the copper nanocone array has a width of 15 μm and a depth of 8 μm;

[0042] S3, according to the weight ratio of nano-TiB2 to graphene oxide of 0.2-0.4:10, nano-TiB2 and a graphene oxide aqueous dispersion with a mass fraction of 2-4wt% are mixed, frozen and solidified at -10 to -30°C, and freeze-dried at -30 to -50°C to obtain a sponge intermediate, and then the sponge intermediate is reduced with hydrazine hydrate vapor, and cut into sheets with a thickness of 5mm to obtain a graphene sponge;

[0043] Graphene sponge, AgCuTi foil, graphene sponge, and pretreated copper substrate were stacked on the surface of the pretreated ceramic substrate in sequence, and the side with the copper nanocone array was in contact with the graphene sponge. The vacuum degree was adjusted to 2.5×10 -3Pa, the applied pressure is 4MPa, and the welding is carried out at 800℃ for 30min, and then cooled in the furnace to obtain a ceramic copper-clad product;

[0044] The AgCuTi foil contains nano-TiB2, wherein the Cu content is 27wt%, the Ti content is 4wt%, and the nano-TiB2 content is 1.5wt%.

[0045] Example 3

[0046] A method for copper coating ceramics comprises the following steps:

[0047] S1, taking an AlN ceramic substrate and adding it into a 0.15 mol / L sodium hydroxide aqueous solution, stirring and etching at room temperature for 25 min, then washing with water and drying to obtain a pretreated ceramic substrate;

[0048] S2, cleaning the oxygen-free copper substrate to remove oil stains and oxide layer, and then treating it with a femtosecond laser (the laser power during the femtosecond laser treatment is 200 mW, the scanning interval is 25 μm, and the scanning speed is 1500 μm / s) to form a copper nanocone array on one side of the copper substrate to obtain a pretreated copper substrate, wherein the copper nanocone array has a width of 20 μm and a depth of 10 μm;

[0049] S3, according to the weight ratio of nano-TiB2 to graphene oxide of 0.2-0.4:10, nano-TiB2 and a graphene oxide aqueous dispersion with a mass fraction of 2-4wt% are mixed, frozen and solidified at -10 to -30°C, and freeze-dried at -30 to -50°C to obtain a sponge intermediate, and then the sponge intermediate is reduced with hydrazine hydrate vapor, and cut into sheets with a thickness of 5mm to obtain a graphene sponge;

[0050] Graphene sponge, AgCuTi foil, graphene sponge, and pretreated copper substrate were stacked on the surface of the pretreated ceramic substrate in sequence, and the side with the copper nanocone array was in contact with the graphene sponge. The vacuum degree was adjusted to 2×10 -3 Pa, the applied pressure is 5MPa, and the welding is carried out at 800℃ for 35min, and then cooled in the furnace to obtain a ceramic copper-clad product;

[0051] The AgCuTi foil contains nano-TiB2, wherein the Cu content is 26.5wt%, the Ti content is 4.5wt%, and the nano-TiB2 content is 1.3wt%.

[0052] Comparative Example 1

[0053] A method for copper coating ceramics comprises the following steps:

[0054] The AlN ceramic substrate and the oxygen-free copper substrate are not pretreated and are welded according to step S3 of Example 3.

[0055] Comparative Example 2

[0056] A method for copper coating ceramics comprises the following steps:

[0057] Without using graphene sponge, AgCuTi foil and pretreated copper substrate are placed on the surface of pretreated ceramic substrate in sequence, and the side with copper nanocone array is in contact with graphene sponge, and the rest is the same as in Example 3.

[0058] Comparative Example 3

[0059] A method for copper coating ceramics comprises the following steps:

[0060] The graphene sponge does not contain nano-TiB2, and the rest is the same as in Example 3.

[0061] Comparative Example 4

[0062] A method for copper coating ceramics comprises the following steps:

[0063] The AgCuTi foil does not contain nano-TiB2, and the rest is the same as in Example 3.

[0064] The properties of the ceramic copper-clad products obtained in Examples 1-3 and Comparative Examples 1-4 were tested, and the results are shown in Table 1.

[0065] Table 1 Test results

[0066] Grouping Shear strength MPa -40℃ to 125℃ cycle times Example 1 124 6437 Example 2 121 6312 Example 3 126 6544 Comparative Example 1 86 5149 Comparative Example 2 61 4178 Comparative Example 3 98 5377 Comparative Example 4 107 5458

[0067] It can be seen from Table 1 that the welding joint of the ceramic copper-clad product prepared by the method of the present invention has good bonding strength and resistance to cold and hot cycles.

[0068] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A method for copper coating ceramics, characterized in that: The steps include: S1, taking a ceramic substrate and performing surface etching treatment to obtain a pretreated ceramic substrate; S2, taking a copper substrate and performing surface treatment to form a copper nanocone array on one side of the copper substrate to obtain a pretreated copper substrate; S3. Stacking graphene sponge, AgCuTi foil, graphene sponge, and pretreated copper substrate in sequence on the surface of the pretreated ceramic substrate, and making the side with the copper nanocone array contact with the graphene sponge, and then welding to obtain a ceramic copper-clad product.

2. The method for copper coating ceramics according to claim 1, characterized in that: In S1, the material of the ceramic substrate is AlN ceramic; preferably, in S1, the ceramic substrate is etched with a sodium hydroxide aqueous solution; preferably, the concentration of the sodium hydroxide aqueous solution is 0.1-0.2 mol / L; preferably, in S1, etching is performed at room temperature for 20-25 min.

3. The method for copper coating ceramics according to claim 1 or 2, characterized in that: In S2, in the copper nanocone array, the width of the copper nanocones is 15-25 μm and the depth is 8-12 μm.

4. The method for copper coating ceramics according to any one of claims 1 to 3, characterized in that: In S2, the surface of the copper substrate is treated with femtosecond laser to form a copper nanocone array on one side of the copper substrate; preferably, during the femtosecond laser treatment, the laser power is 180-220 mW, the scanning interval is 25-30 μm, and the scanning speed is 1400-1500 μm / s.

5. The method for copper coating ceramics according to any one of claims 1 to 4, characterized in that: In S3, the AgCuTi foil contains nano-TiB2; preferably, in the AgCuTi foil, the Cu content is 26-27wt%, the Ti content is 4-5wt%, and the nano-TiB2 content is 1-1.5wt%.

6. The method for copper coating ceramics according to any one of claims 1 to 5, characterized in that: In S3, the preparation method of the graphene sponge includes: mixing nano-TiB2 and graphene oxide dispersion, freezing and solidifying, freeze-drying to obtain a sponge intermediate, and then reducing the sponge intermediate with hydrazine hydrate vapor to obtain a graphene sponge.

7. The method for copper coating ceramics according to claim 6, characterized in that: The mass fraction of the graphene oxide dispersion is 2-4wt%; preferably, it is frozen and solidified at -10 to -30°C; preferably, it is freeze-dried at -30 to -50°C.

8. The method for copper coating ceramics according to claim 6, characterized in that: The weight ratio of nano-TiB2 to graphene oxide is 0.2-0.4:

10.

9. The method for copper coating ceramics according to any one of claims 1 to 8, characterized in that: In S3, the vacuum degree during welding is 1.5×10 -3 -2.5×10 -3 Pa, the applied pressure is 4-6MPa.

10. The method for copper coating ceramics according to any one of claims 1 to 9, characterized in that: In S3, the welding temperature is 780-800°C and the welding time is 30-40min.