Preparation method of plating layer of salt-spray-corrosion-resistant alloy cover plate

Abstract

The invention discloses a method for preparing a plating layer of a salt-spray-corrosion-resistant alloy cover plate, which comprises the following steps of: immersing the alloy cover plate into an acetone or alcohol solution, cleaning the surface of the alloy cover plate by utilizing ultrasonic cleaning, and removing impurities; the cleaned alloy cover plate is clamped on a cold spraying workbench, and a pure titanium thick film is formed on the upper surface of the alloy cover plate through the cold spraying technology; the alloy cover plate is immersed in acetone or alcohol, the surface of the alloy cover plate is cleaned through ultrasonic cleaning, and impurities are removed; all the outer surfaces of the cleaned alloy cover plate are sequentially plated with nickel and gold, and a nickel plating layer and a gold plating layer are formed; a tube shell to be subjected to parallel sealing welding is placed on a parallel sealing welding machine workbench, an alloy cover plate is placed above the tube shell, and the center of the alloy cover plate is aligned with the center of a tube shell sealing frame; and pre-welding and positioning the alloy cover plate and the tube shell by using a parallel sealing and welding machine, and then carrying out airtight sealing and welding on the alloy cover plate and the tube shell. The problem that the salt spray corrosion resistance is reduced due to the fact that iron elements are exposed on the surface of a weld joint in an existing parallel seal welding technology can be solved.

Description

Technical Field

[0001] The invention relates to integrated circuit packaging technology, and in particular to a method for preparing a plating layer of an alloy cover plate resistant to salt spray corrosion. Background Art

[0002] Parallel welding is a common method for high-reliability metal-ceramic airtight packaging of integrated circuits. This technology uses the principle of resistance welding and the resistance heat generated when a large pulse current passes through a pair of coaxially opposed truncated copper alloy electrodes and a cover plate to heat the local metal to the melting point, thereby partially melting the cover plate substrate and the coating on the cover plate, so that the tube shell and the cover plate are welded together. The surface of the conventional parallel welding cover plate is only coated with a nickel layer and a gold layer of a few microns. Under the action of the parallel welding electrode pressure and resistance heat, the coating on the cover plate is destroyed, the cover plate substrate at the bottom of the coating layer melts, and the iron element in the cover plate substrate material diffuses and flows, resulting in the iron element being exposed on the upper surface of the weld.

[0003] In a salt spray environment, the iron on the weld surface and the high-potential metal nearby form a corrosion cell. The iron, as the anode, loses electrons and undergoes an oxidation reaction. The high-potential metal, as the cathode, transfers the electrons it obtains to oxygen, causing an oxygen absorption reaction on the cathode surface. As the electrochemical corrosion reaction progresses, the iron element in the weld continues to dissolve and rust, eventually leading to airtight failure and threatening the performance reliability of integrated circuit devices. Summary of the invention

[0004] Purpose of the invention: The purpose of the present invention is to provide a method for preparing a coating layer of an alloy cover plate resistant to salt spray corrosion, so as to solve the problem in the existing parallel sealing technology that the iron element is exposed on the weld surface and reduces the salt spray corrosion resistance.

[0005] Technical solution: A method for preparing a coating layer of a salt spray corrosion resistant alloy cover plate of the present invention comprises:

[0006] Immerse the alloy cover plate in acetone or alcohol solution, and use ultrasonic cleaning to clean the surface of the alloy cover plate to remove surface impurities;

[0007] The cleaned alloy cover plate is clamped on a cold spraying workbench by a fixture, and a pure titanium thick film is formed on the upper surface of the alloy cover plate by using a cold spraying technology;

[0008] The alloy cover plate with the pure titanium thick film is immersed in acetone or alcohol, and the surface of the alloy cover plate with the pure titanium thick film is cleaned by ultrasonic cleaning to remove surface impurities;

[0009] All outer surfaces of the cleaned alloy cover plate with a pure titanium thick film are plated with nickel and gold in sequence to form a nickel plating layer and a gold plating layer;

[0010] The tube shell to be parallel welded is placed on the workbench of the parallel welder with a fixture, and the alloy cover plate with nickel plating and gold plating is placed on the tube shell to be parallel welded, and the center of the alloy cover plate is aligned with the center of the tube shell sealing frame;

[0011] Use a parallel sealing machine to pre-weld and position the alloy cover plate and the tube shell to be parallel sealed, and then complete the airtight sealing.

[0012] Furthermore, the thickness of the pure titanium thick film is 10-100 μm, so as to improve the salt spray corrosion resistance of the parallel sealing weld without increasing the welding heat input.

[0013] Furthermore, the pure titanium thick film comprises a plurality of pure titanium particles, the purity of the pure titanium particles is greater than 99%, and the particle size is 1-100 μm, which facilitates the adjustment of the film thickness when cold spraying the pure titanium thick film.

[0014] Furthermore, the spraying temperature of the spray gun in the cold spray workbench is set to 400-1000°C, the gas pressure is set to 3-5Mpa, and the accelerating gas is helium to ensure the bonding strength between the pure titanium thick film and the alloy cover plate and to ensure that the pure titanium layer is not oxidized.

[0015] Furthermore, the distance from the spray gun mouth to the upper surface of the alloy cover plate in the cold spraying workbench is 30-60 mm, and the spray gun moving speed is 50-500 mm / s to ensure the bonding strength between the pure titanium thick film and the alloy cover plate and the deformation degree of the alloy cover plate.

[0016] Furthermore, the thickness of the nickel plating layer is 1.3-8.9 μm.

[0017] Furthermore, the thickness of the gold plating layer is 1.3-5.7 μm.

[0018] Furthermore, the angle of the electrode material used in the parallel sealing machine is 4-16°.

[0019] Furthermore, the pulse peak value of the parallel sealing machine is set to 200-3500W, and the pulse width is set to 1-40ms.

[0020] Furthermore, the parallel sealing machine has a sealing speed of 0.5-10 mm / s and an electrode pressure of 100-1600 g.

[0021] Technical effects: Compared with the prior art, the significant technical effects of the present invention are as follows:

[0022] A layer of pure titanium thick film is formed on the surface of the alloy cover plate through cold spraying technology as a protective barrier layer, which significantly inhibits the exposure of iron elements in the iron-nickel alloy or Kovar alloy cover plate on the weld surface after parallel sealing welding, and ultimately improves the salt spray corrosion resistance of parallel sealing welding.

[0023] During cold spraying, the pure titanium particles accelerated by the high-speed airflow hit the substrate surface at an extremely high speed. On the one hand, the alloy cover plate is deformed and thinned; on the other hand, the pure titanium particles are embedded to a certain depth on the surface of the alloy cover plate. Therefore, when forming a pure titanium thick film, the thickness of the alloy cover plate can be increased as little as possible. During parallel sealing, no additional heat input is required to avoid causing greater thermal stress and ensure the airtightness of the integrated circuit device.

[0024] The present invention can ensure airtight packaging under the same level of process parameters, significantly improve the salt spray corrosion resistance of the parallel sealing weld, and enhance the performance reliability of integrated circuit devices. The operation method is simple, the process is stable, and it is easy to realize industrialization and automated mass production. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a schematic diagram of the overall process of the present invention;

[0026] Figure 2 It is a cross-sectional schematic diagram of the alloy cover plate with a pure titanium thick film in the present invention;

[0027] Figure 3 It is a cross-sectional schematic diagram of the assembly of the tube shell to be sealed and welded and the alloy cover plate in the present invention;

[0028] Figure 4 This is a comparison diagram of the salt spray corrosion effect of Example 1 and the existing parallel sealing weld;

[0029] Figure 5 This is a comparison diagram of surface elements of the weld seam between Example 1 and the prior art parallel sealing welding;

[0030] Figure 6 This is a comparison chart of the salt spray corrosion effect of Example 2 and the existing parallel sealing weld. DETAILED DESCRIPTION

[0031] The technical solution of the present invention is described in detail below in conjunction with specific implementation methods and the accompanying drawings of the specification.

[0032] Example 1

[0033] like Figure 1 As shown, a method for preparing a coating layer of a salt spray corrosion resistant alloy cover plate of the present invention comprises the following steps:

[0034] S1. Immerse the alloy cover plate 4 in acetone or alcohol solution, and use ultrasonic cleaning to clean the surface of the alloy cover plate 4 to remove impurities such as surface oil stains.

[0035] In this embodiment, the alloy cover plate material is 4J42.

[0036] S2, clamping the cleaned alloy cover plate 4 on the cold spraying workbench with a fixture, and forming a pure titanium thick film 1 on the upper surface of the alloy cover plate by cold spraying technology, such as Figure 2 shown.

[0037] The thickness of the pure titanium thick film 1 is 10-100μm. The thickness of the pure titanium thick film 1 mainly relates to whether the alloy cover plate melts during welding. When it is 10-50μm, the alloy cover plate will still melt; when it is 50-100μm, the alloy cover plate will no longer melt during the welding process, only the coating will melt, and the pure titanium layer will become a barrier layer. In parallel sealing welding, the thickness of the alloy cover plate is usually 0.08-0.12mm, so the pure titanium layer > 100μm will become meaningless. If the thickness is > 100μm, it is better to use a pure titanium cover plate directly. The pure titanium thick film includes a number of pure titanium particles with a purity greater than 99% and a particle size of 1-100μm. The spraying temperature of the spray gun in the cold spray workbench is set to 400-1000℃, the gas pressure is set to 3-5Mpa, and the accelerating gas is helium. The distance from the spray gun mouth to the upper surface of the alloy cover plate in the cold spray workbench is 30-60mm, and the spray gun moving speed is 50-500mm / s.

[0038] In this embodiment, the purity of the pure titanium particles used for cold spraying is 99.9% and the particle size is 40-50 μm. The spraying temperature used for cold spraying is 700°C, the gas pressure is 4 MPa, the distance from the spray gun mouth to the upper surface of the alloy cover plate is 45 mm, and the spray gun moving speed is 275 mm / s. A pure titanium thick film 1 with a film thickness of 40-50 μm is formed on the upper surface of the alloy cover plate. Figure 2 The thickness of the cover plate edge before and after cold spraying was measured with a vernier caliper. The thickness was 0.1 mm before cold spraying and 0.12 mm after cold spraying, indicating that the sum of the compression deformation of the cover plate and the depth of pure titanium particles embedded in the alloy cover plate was 20-30 μm.

[0039] S3, immersing the alloy cover plate 4 with the pure titanium thick film 1 in acetone or alcohol, and cleaning the surface of the alloy cover plate with the pure titanium thick film 1 by ultrasonic cleaning to remove impurities such as surface oil and dust.

[0040] S4, such as Figure 2 As shown, all outer surfaces of the cleaned alloy cover plate 4 having the pure titanium thick film 1 are plated with nickel and gold in sequence to form a nickel plating layer 2 and a gold plating layer 3 .

[0041] The thickness of the nickel plating layer is 1.3-8.9 μm, and the thickness of the gold plating layer is 1.3-5.7 μm.

[0042] In this embodiment, the nickel and gold are plated by electroplating process, and the thickness of the formed nickel plating layer 2 is 4-5 μm, and the thickness of the formed gold plating layer 3 is 1.3-2 μm.

[0043] S5, the tube shell 5 to be parallel sealed is placed on the workbench of the parallel sealing machine with a fixture, and the alloy cover plate with nickel plating and gold plating is placed on the tube shell 5 to be parallel sealed, and the center of the alloy cover plate is aligned with the center of the sealing frame of the tube shell 5, such as Figure 3 shown.

[0044] S6. Use a parallel sealing machine to pre-weld and position the alloy cover plate and the tube shell to be parallel sealed, and then complete the airtight sealing.

[0045] The electrode material angle used by the parallel welding machine is 4-16°. The pulse peak of the parallel welding machine is set to 200-3500W, and the pulse width is set to 1-40ms. The welding speed of the parallel welding machine is 0.5-10mm / s, and the electrode pressure is 100-1600g.

[0046] In this embodiment, the sealing frame size of the airtight packaging product is 16mm×15.5mm, the electrode angle used for parallel sealing is 10°, the pulse peak is 2000W, the pulse width is 5ms, the electrode pressure is 300g, and the sealing speed is 3mm / s.

[0047] For the samples that have completed airtight packaging, the leakage rate of the fine inspection is measured to be less than 5×10 -9 Pa cm 3 / s, no obvious bubbles were observed in the rough leak test. Subsequently, the sample was subjected to a salt spray corrosion test, and the results are shown in Figure 4 ,in Figure 3 Figure (a) shows the salt spray corrosion effect of the parallel sealing weld of the present invention. Figure 3 Figure (b) is a diagram showing the effect of salt spray corrosion on the existing parallel-sealed welds. Obviously, under the same technical parameters, the area of ​​weld corrosion defects is significantly reduced using the method of the present invention, and the salt spray corrosion resistance of the welds is significantly improved after parallel-sealed welding.

[0048] like Figure 5 As shown, Figure 5 Figure (a) is an element distribution diagram of the weld surface obtained by using the technical solution of the present invention. Figure 5 Figure (b) is the element distribution diagram of the weld surface of the existing parallel sealing technology. Obviously, the technical solution of the present invention forms a layer of pure titanium thick film on the upper surface of the alloy cover plate as a protective barrier layer through cold spraying technology, thereby significantly inhibiting the exposure of iron elements in the iron-nickel alloy or Kovar alloy cover plate on the weld surface after parallel sealing, and ultimately improving the salt spray corrosion resistance of parallel sealing.

[0049] Example 2

[0050] The steps and parameters used in this embodiment are the same as those in embodiment 1, except that: a pure titanium thick film 1 is formed on the surface of the alloy cover plate by cold spraying with a thickness of 40-50 μm, and then it is polished with sandpaper until the thickness of the edge of the cover plate is about 0.10 mm, and the thickness of the pure titanium film is thinned to 20-30 μm. The salt spray corrosion results are shown in FIG. Figure 6 , Figure 6 Figure (a) shows the salt spray corrosion effect of the parallel sealing weld of the present invention. Figure 6 Figure (b) shows the salt spray corrosion effect of the existing parallel sealed weld. It can be seen that under the conditions of the same technical parameters, the corrosion resistance of the weld of the cold sprayed pure titanium thick film is better than that of the existing parallel sealed weld.

[0051] The above embodiments prove that the technical solution of the present invention has obvious advantages. Pure titanium metal particles impact the upper surface of the alloy cover plate at high speed and embed to a certain depth. While the titanium film is thickened, the alloy cover plate is deformed and its thickness is reduced. Therefore, by adjusting the thickness of the pure titanium thick film, it is possible to ensure airtight packaging and significantly reduce the exposure of iron elements on the surface of the parallel sealing weld without increasing the parallel sealing heat input to cause greater thermal stress, thereby improving the salt spray corrosion resistance of the integrated circuit device and enhancing the performance reliability of the integrated circuit device.

[0052] The present invention solves the problem that the iron element of the existing iron-nickel alloy or Kovar alloy cover plate diffuses and flows and is exposed on the weld surface after parallel sealing, causing the parallel sealing weld to be corroded in a corrosive atmosphere, resulting in airtight failure. Compared with thin films, pure titanium thick films can more effectively inhibit the exposure of iron elements on the surface of parallel sealing welds, so that titanium elements form a corrosion barrier layer on the weld surface, significantly improving the salt spray corrosion resistance of parallel sealing welds; compared with metal surface deposition technologies such as electroplating, chemical plating and vacuum evaporation, cold spray technology is easier to form thick films.

Claims

1. A method for preparing a coating layer of a salt spray corrosion resistant alloy cover plate, characterized in that: include: Immerse the alloy cover plate in acetone or alcohol solution, and use ultrasonic cleaning to clean the surface of the alloy cover plate to remove surface impurities; The cleaned alloy cover plate is clamped on a cold spraying workbench by a fixture, and a pure titanium thick film is formed on the upper surface of the alloy cover plate by using a cold spraying technology; The alloy cover plate with the pure titanium thick film is immersed in acetone or alcohol, and the surface of the alloy cover plate with the pure titanium thick film is cleaned by ultrasonic cleaning to remove surface impurities; All outer surfaces of the cleaned alloy cover plate with a pure titanium thick film are plated with nickel and gold in sequence to form a nickel plating layer and a gold plating layer; The tube shell to be parallel welded is placed on the workbench of the parallel welder with a fixture, and the alloy cover plate with nickel plating and gold plating is placed on the tube shell to be parallel welded, and the center of the alloy cover plate is aligned with the center of the tube shell sealing frame; Use a parallel sealing machine to pre-weld and position the alloy cover plate and the tube shell to be parallel sealed, and then complete the airtight sealing.

2. The method for preparing a coating layer of a salt spray corrosion resistant alloy cover plate according to claim 1, characterized in that: The thickness of the pure titanium thick film is 10-100 μm.

3. The method for preparing a coating layer of a salt spray corrosion resistant alloy cover plate according to claim 1, characterized in that: The pure titanium thick film comprises a plurality of pure titanium particles, the purity of the pure titanium particles is greater than 99%, and the particle size is 1-100 μm.

4. The method for preparing a coating layer of a salt spray corrosion resistant alloy cover plate according to claim 1, characterized in that: The spraying temperature of the spray gun in the cold spray workbench is set to 400-1000° C., the gas pressure is set to 3-5 MPa, and the accelerating gas is helium.

5. The method for preparing a coating layer of a salt spray corrosion resistant alloy cover plate according to claim 1, characterized in that: The distance from the spray gun mouth to the upper surface of the alloy cover plate in the cold spraying workbench is 30-60 mm, and the moving speed of the spray gun is 50-500 mm / s.

6. The method for preparing a coating layer of a salt spray corrosion resistant alloy cover plate according to claim 1, characterized in that: The thickness of the nickel plating layer is 1.3-8.9 μm.

7. The method for preparing a coating layer of a salt spray corrosion resistant alloy cover plate according to claim 1, characterized in that: The thickness of the gold plating layer is 1.3-5.7 μm.

8. The method for preparing a coating layer of a salt spray corrosion resistant alloy cover plate according to claim 1, characterized in that: The angle of the electrode material used in the parallel sealing welding machine is 4-16°.

9. The method for preparing a coating layer of a salt spray corrosion resistant alloy cover plate according to claim 1, characterized in that: The pulse peak value of the parallel sealing machine is set to 200-3500W, and the pulse width is set to 1-40ms.

10. The method for preparing a coating layer of a salt spray corrosion resistant alloy cover plate according to claim 9, characterized in that: The parallel sealing machine has a sealing speed of 0.5-10 mm / s and an electrode pressure of 100-1600 g.

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