Process method for improving diffusion barrier performance and corrosion resistance of amorphous Ni-P coating

Abstract

The invention discloses a process method for improving diffusion barrier performance and corrosion resistance of an amorphous Ni-P coating, and the process method comprises the following steps: step 1, pretreatment: grinding, polishing, cleaning and blow-drying a substrate to obtain a substrate to be plated; step 2, preparing a plating solution: dissolving nickel sulfate hexahydrate, nickel acetate tetrahydrate, trisodium citrate dehydrate, potassium sodium tartrate tetrahydrate, lauryl sodium sulfate, ammonium acetate and sodium hypophosphite into water, mixing to form a mixed solution, and adjusting the pH value of the mixed solution to 6-7 to obtain the plating solution; and 3, chemical plating is conducted, specifically, the to-be-plated substrate obtained in the step 1 serves as a cathode, a Ni sheet serves as an anode, the cathode and the anode are put into the plating solution obtained in the step 2, power-on activation is conducted, after plating is started, chemical plating is conducted spontaneously, and a chemical plating Ni-P plating layer is obtained. The plating layer prepared through the process method is smooth and compact in surface and free of air holes, has a mirror surface effect macroscopically, and has good corrosion resistance and diffusion barrier performance.

Description

Technical Field

[0001] This invention relates to the field of surface treatment technology, and in particular to a process method for improving the diffusion barrier performance and corrosion resistance of amorphous Ni-P coatings. Background Technology

[0002] Currently, Ni-P coatings are widely used in electronic packaging as diffusion barrier layers and in metal corrosion protection. Most widely used Ni-P coatings have a cellular morphology. However, the uneven surface of cellular coatings can form corrosion micro-cells, accelerating corrosion. Furthermore, the presence of numerous columnar grain boundaries within Ni-P coatings can accelerate aging and eventual failure in coastal applications due to the humid climate and the corrosive effects of seawater chloride ions. Simultaneously, the columnar grain boundaries within the cellular structure of Ni-P coatings act as rapid atomic diffusion channels during the brazing reaction, severely impacting their diffusion barrier performance.

[0003] Existing Ni-P coatings have poor corrosion resistance due to their cellular surface structure, and the presence of columnar grain boundaries within the coating also results in poor diffusion barrier performance. In response, this invention provides a process method to improve the diffusion barrier performance and corrosion resistance of amorphous Ni-P coatings. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a method for improving the diffusion barrier performance and corrosion resistance of amorphous Ni-P coatings. The method involves mixing a main salt (a mixture of nickel sulfate hexahydrate and nickel acetate tetrahydrate), a complexing agent (a mixture of trisodium citrate dihydrate and sodium potassium tartrate tetrahydrate), sodium dodecyl sulfate, ammonium acetate, and sodium hypophosphite, then adding water and stirring until homogeneous. The pH is then adjusted to 6-7 to obtain a plating solution. This solution is then used to chemically platrude onto a substrate, resulting in a coating with Ni content of 75%-85% and P content of 15%-25%.

[0005] According to one aspect of the present invention, a process method for improving the diffusion barrier performance and corrosion resistance of amorphous Ni-P coatings is provided, the process method comprising the following steps: Step 1, Pre-treatment: Polish the substrate, clean and dry it to obtain the substrate to be plated; Step 2, Plating solution preparation: Dissolve nickel sulfate hexahydrate, nickel acetate tetrahydrate, trisodium citrate dihydrate, potassium sodium tartrate tetrahydrate, sodium dodecyl sulfate, ammonium acetate, and sodium hypophosphite in water and mix to form a mixed solution. Adjust the pH of the mixed solution to 6-7 to obtain the plating solution. Step 3, chemical plating: The substrate to be plated obtained in Step 1 is placed in the plating solution obtained in Step 2 as the cathode and the Ni sheet as the anode. After activating by electricity, the chemical plating proceeds spontaneously to obtain a chemically plated Ni-P coating.

[0006] Furthermore, the substrate mentioned in step 1 is a steel plate or a Cu plate; In step 2, the concentration ratio of nickel sulfate hexahydrate, nickel acetate tetrahydrate, trisodium citrate dihydrate, potassium sodium tartrate tetrahydrate, sodium dodecyl sulfate, ammonium acetate, and sodium hypophosphite in the mixture is 40~60 : 10~20 : 40~50 : 1~20 : 0.1~0.5 : 20~40 : 10~45.

[0007] Further, in step 2, the concentration ratio of nickel sulfate hexahydrate, nickel acetate tetrahydrate, trisodium citrate dihydrate, potassium sodium tartrate tetrahydrate, sodium dodecyl sulfate, ammonium acetate, and sodium hypophosphite in the mixture is 40~50 : 10~20 : 40~50 : 1~20 : 0.1~0.5 : 30~40 : 20~45.

[0008] Furthermore, the activation time in step 3 is 1~10s; The power supply voltage used for power-on activation in step 3 is 0.5~4V.

[0009] Furthermore, the electroless plating temperature in step 3 is 60~70℃; The electroless plating time in step 3 is 0.2~4 hours.

[0010] Furthermore, the coating surface of the electroless steel plate obtained in step 3 is smooth and dense, without pores.

[0011] Furthermore, the thickness of the coating is 1~50μm; The coating contains 75-85% Ni and 15-25% P.

[0012] Furthermore, when the smooth Ni-P coating is subjected to potentiodynamic scanning in a 3.5% NaCl solution, its polarization curve shows a distinct passivation zone in the range of -0.54 to 0.06 V, indicating a significant enhancement in corrosion resistance.

[0013] Furthermore, when the smooth Ni-P barrier layer is brazed with SAC305 solder, the barrier layer consumption rate constant is 0.43, which is much smaller than the consumption rate constant of 0.81 of the common cellular Ni-P barrier layer.

[0014] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) The electroless plating temperature in the process method disclosed in this invention is about 60-70℃, and the energy consumption is low. In the past, electroless Ni-P plating required pre-plating Ni, or phosphating, zinc immersion, or palladium chloride activation treatment, which were complex processes and expensive chemicals. The process of this invention is simple, easy to operate, and has a good activation effect. (2) Due to proper control of the plating solution formula, the amorphous Ni-P coating prepared by the process method of the present invention has a smooth and dense surface without pores, and exhibits a mirror effect on a macroscopic scale.

[0015] (3) The smooth Ni-P / 20# steel prepared by the process method of the present invention showed obvious passivation (in the range of -0.54~0.06V) after being subjected to potentiodynamic polarization scanning in 3.5% NaCl solution, demonstrating excellent corrosion resistance.

[0016] (4) When the smooth Ni-P prepared by the process method of the present invention is brazed with SAC305 solder, the barrier layer consumption rate constant is 0.43, which is much smaller than the common cellular Ni-P barrier layer consumption rate constant of 0.81. Compared with ordinary cellular Ni-P, the smooth Ni-P barrier layer prepared by the process method of the present invention consumes its thickness more slowly, showing excellent barrier performance. Attached Figure Description

[0017] Figure 1 This is a SEM image of the surface of the amorphous Ni-P coating prepared in Example 1 of the present invention; Figure 2 The XRD pattern of the amorphous Ni-P coating prepared in Example 1 of this invention; Figure 3 The graph shows the corrosion resistance test results of Test Example 1 and Comparative Example 3 of this invention. Figure 4 The graph shows the performance test results of the barrier layer described in Test Example 2 and Comparative Example 4 of this invention. Figure 5 Here is a SEM image of the Ni-P coating surface prepared in Comparative Example 1 of this invention; Figure 6 This is a SEM image of the Ni-P coating surface prepared in Comparative Example 2 of this invention. Detailed Implementation

[0018] The present invention will be further described below with reference to specific embodiments, but this does not limit the present invention in any way.

[0019] Unless otherwise specified, all reagents and raw materials used in this invention are obtained through purchase.

[0020] Example 1 Step 1, Pre-treatment: Grind and polish the 20# steel, ultrasonically clean it, and blow it dry to obtain the 20# steel to be plated.

[0021] Step 2, plating solution preparation: nickel sulfate hexahydrate 40 g / L, nickel acetate tetrahydrate 10 g / L, trisodium citrate dihydrate 50 g / L, potassium sodium tartrate tetrahydrate 10 g / L, sodium dodecyl sulfate 0.1 g / L, ammonium acetate 40 g / L, sodium hypophosphite 25 g / L, and the pH of the plating solution is 6.

[0022] Step 3, chemical plating: The plating solution described in Step 2 is placed in a constant temperature heater, and the temperature is controlled at 60℃. The 20# steel to be plated in Step 1 is used as the cathode, and the Ni sheet is used as the anode. The solution is then immersed in the plating solution. The power supply voltage is set to 0.5V, and activation is performed for 1 second. Chemical plating is then carried out for 0.5 hours, yielding chemically plated 20# steel. The chemically plated 20# steel exhibits a smooth amorphous Ni-P coating. The composition of the coating is Ni 79 at.%, P 21 at.%, and the coating thickness is 4.2 μm. The coating morphology is as follows. Figure 1 As shown, the XRD characterization of the coating is as follows: Figure 2 As shown.

[0023] Comparative Example 1 The difference from Example 1 is that the plating solution in step 2 contains 30 g / L of trisodium citrate dihydrate. The remaining steps are consistent with Example 1. Trisodium citrate dihydrate is a complexing agent. A low concentration of complexing agent in the plating solution results in a high concentration of free main salt ions and reducing agents during the electroless plating reaction, leading to a vigorous reaction. Therefore, the surface of the electroless Ni-P plating layer is uneven and exhibits textures, such as... Figure 5 As shown.

[0024] Comparative Example 2 The difference from Example 1 is that the pH of the plating solution in step 2 is 8, while the remaining steps are consistent with Example 1. The Ni-P coating on the surface of the 20# steel after chemical plating has a cellular structure, as shown in Example 1. Figure 6 As shown.

[0025] Test Example 1 The electroless plated 20# steel (smooth Ni-P / 20# steel) prepared in Example 1 was placed in a 3.5% NaCl solution for potentiodynamic scanning to test its corrosion resistance. The smooth Ni-P / 20# steel exhibited significant passivation in the 3.5% NaCl solution. The polarization curve test results are as follows: Figure 3 As shown, the passivation zone appears in the range of -0.54~0.06V, exhibiting excellent corrosion resistance.

[0026] Comparative Example 3 The 20# steel to be plated in Example 1 was placed in a 3.5% NaCl solution for potentiodynamic scanning to test its corrosion resistance. The polarization curve test results are as follows: Figure 3 As shown, there is no obvious passivation area.

[0027] Test Example 2 The Cu substrate after electroless Ni-P plating was brazed with SAC solder, and the barrier layer performance was tested. The smooth Ni-P substrate exhibited a barrier layer consumption rate constant of 0.43 when brazed with SAC305 solder, demonstrating excellent barrier performance. The test results are as follows: Figure 4 As shown.

[0028] Comparative Example 4 A Cu substrate electroless plated with Ni-P was brazed with SAC solder, and the barrier layer performance was tested. The consumption rate constant of the cellular Ni-P barrier layer was 0.81. The test results are as follows: Figure 4 As shown, this indicates that the cellular structure has a poor Ni-P blocking effect.

[0029] The above description is merely a few embodiments of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any modifications or alterations made by those skilled in the art without departing from the scope of the technical solution of the present invention using the disclosed technical content are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A process for improving the diffusion barrier properties and corrosion resistance of amorphous Ni-P coatings, characterized in that, The process includes the following steps: Step 1, Pre-treatment: Polish the substrate, clean and dry it to obtain the substrate to be plated; Step 2, Plating solution preparation: Dissolve nickel sulfate hexahydrate, nickel acetate tetrahydrate, trisodium citrate dihydrate, potassium sodium tartrate tetrahydrate, sodium dodecyl sulfate, ammonium acetate, and sodium hypophosphite in water and mix to form a mixed solution. Adjust the pH of the mixed solution to 6-7 to obtain the plating solution. Step 3, chemical plating: The substrate to be plated obtained in Step 1 is placed in the plating solution obtained in Step 2 as the cathode and the Ni sheet as the anode. After activating by electricity, the chemical plating proceeds spontaneously to obtain a chemically plated Ni-P coating.

2. The process method according to claim 1, characterized in that, The substrate mentioned in step 1 is a steel plate or a Cu plate; In step 2, the concentration ratio of nickel sulfate hexahydrate, nickel acetate tetrahydrate, trisodium citrate dihydrate, potassium sodium tartrate tetrahydrate, sodium dodecyl sulfate, ammonium acetate, and sodium hypophosphite in the mixture is 40~60 : 10~20 : 40~50 : 1~20 : 0.1~0.5 : 20~40 : 10~45.

3. The process method according to claim 2, characterized in that, In step 2, the concentration ratio of nickel sulfate hexahydrate, nickel acetate tetrahydrate, trisodium citrate dihydrate, potassium sodium tartrate tetrahydrate, sodium dodecyl sulfate, ammonium acetate, and sodium hypophosphite in the mixture is 40~50 : 10~20 : 40~50 : 1~20 : 0.1~0.5 : 30~40 : 20~45.

4. The process method according to claim 1, characterized in that, The power-on activation time in step 3 is 1~10s; The power supply voltage used for power-on activation in step 3 is 0.5~4V.

5. The process method according to claim 1, characterized in that, The electroless plating temperature in step 3 is 60~70℃; The electroless plating time in step 3 is 0.2~4 hours.

6. The process method according to claim 1, characterized in that, The coating obtained in step 3 has a smooth and dense surface without pores.

7. The process method according to claim 6, characterized in that, The thickness of the coating is 1~80μm; The coating contains 75-85% Ni and 15-25% P.

8. The process method according to claim 6, characterized in that, The smooth Ni-P coating was subjected to potentiodynamic scanning in a 3.5% NaCl solution, and a significant passivation zone appeared in the range of -0.54 to 0.06 V, indicating a significant enhancement in corrosion resistance.

9. The process method according to claim 6, characterized in that, When the smooth Ni-P barrier layer is brazed with SAC305 solder, the barrier layer consumption rate constant is 0.43, which is much smaller than the cellular Ni-P barrier layer consumption rate constant of 0.81.

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