Method for generating oxide protective film on surface of diverter manganese-copper plate body

Abstract

The invention provides a method for generating an oxide protective film on the surface of a diverter manganese-copper plate body. The method comprises the following steps: cleaning and activating the surfaces of a manganese-copper plate body and a red copper plate body which are formed by welding; electroplating metal coatings on the surfaces of the manganese-copper plate body and the red copper plate body; and selectively irradiating the electroplated layer by laser to form a compact oxide layer. According to the method for generating the oxide protective film on the surface of the diverter manganese-copper plate body, when laser irradiates a nickel plating layer, light beams with high energy density enable the surface of the electroplated layer to be locally and rapidly heated. In the air, the high temperature promotes an oxidation reaction between the electroplated layer and oxygen to generate an oxide. Corrosion of the manganese-copper plate body is reduced, surface oxidation of the manganese-copper plate body is slowed down, and the influence on the electrical performance of the shunt is reduced.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of surface treatment of electronic components, and particularly relates to a method for forming a protective oxide layer on the surface of a manganese-copper plate body and a red copper plate body of a shunt through a combination of electroplating and laser oxidation, and is particularly suitable for surface protection of a shunt for high-precision current measurement. BACKGROUND

[0002] As a core component for current measurement, a shunt is usually formed by welding a manganese-copper alloy plate body with high resistivity and red copper plate bodies with low resistivity on both sides. However, the manganese-copper alloy is prone to oxidation reaction with oxygen and moisture in the environment during long-term use, resulting in resistance drift and affecting measurement accuracy.

[0003] However, the traditional protection methods of coating organic coating or single electroplating have the following problems: (1) the high insulation of the organic coating affects the heat dissipation performance of the shunt; (2) the conventional electroplated layer (such as nickel plating) may affect the normal electrical performance of the shunt.

[0004] Therefore, there is an urgent need for a surface treatment technology that can protect the manganese-copper plate body from oxidation while maintaining the electrical performance of the shunt. SUMMARY

[0005] The purpose of the present application is to provide a method for generating an oxide protective film on the surface of a manganese-copper plate body of a shunt to solve the problems raised in the background art:

[0006] (1) How to reduce corrosion of the manganese-copper plate body in a high-temperature and high-humidity environment, slow down the oxidation of the surface of the manganese-copper plate body, and reduce the impact on the electrical performance of the shunt.

[0007] To achieve the above-mentioned purpose, the present application provides the following technical solutions:

[0008] A method for generating an oxide protective film on the surface of a manganese-copper plate body of a shunt, comprising the following steps:

[0009] a) Pretreatment: surface cleaning and activation of the welded and formed manganese-copper plate body and red copper plate body;

[0010] b) Electroplating: electroplating a metal plating layer on the surface of the manganese-copper plate body and the red copper plate body;

[0011] c) Laser oxidation: forming a dense oxide layer by selectively irradiating the electroplated layer with a laser.

[0012] On the basis of the above technical solutions, the present application can also be improved as follows.

[0013] Further, the activation in step a) is to immerse the shunt in a 10% dilute sulfuric acid solution to remove the oxide film and improve the adhesion of the plating layer.

[0014] Further, in step b), a nickel sulfamate plating solution is selected, the current density is 2-4 A / dm 2 , the temperature is 50-60℃, and the plating time is 30-60 minutes.

[0015] Further, in step b), a silver cyanide plating solution is selected, the current density is 0.5-1.5 A / dm 2 , the temperature is 20-30℃, the plating time is 20-40 minutes, and a silver layer of 8-15 μm is formed.

[0016] Further, in step b), the thickness of the metal plating layer is 5-20 μm.

[0017] Further, in step c), a laser with a wavelength of 1064 nm, a pulse width of 10-100 ns, a power of 50-200 W, a scanning speed of 100-500 mm / s, a spot diameter of 50-100 μm, and a repetition frequency of 20-100 kHz is selected.

[0018] Further, in step c), the thickness of the compact oxide layer is 0.5-5 μm.

[0019] After adopting such a structure, in the method for generating an oxide protective film on the surface of a manganese-copper plate body of a flow divider, when the nickel plating layer is irradiated with a laser, the high-energy-density light beam locally and rapidly heats the nickel surface (up to several hundred to several thousand degrees Celsius). In air, the high temperature promotes the oxidation reaction of nickel with oxygen, generating an oxide of nickel. The specific reaction product depends on the following factors:

[0020] At high temperatures, nickel tends to generate nickel oxide (NiO) which is more thermodynamically stable. In an oxygen-rich environment, high-valence oxides (such as Ni2O3 or NiO2, but the latter is extremely unstable) can be generated.

[0021] Main oxidation reaction (generating NiO):

[0022]

[0023] Potential side reaction (generating Ni2O3):

[0024]

[0025] (Note: Ni2O3 is easily decomposed into NiO and O2 at high temperatures, so the actual oxide layer is mainly NiO.)

[0026] Similarly, in the method for generating an oxide protective film on the surface of a manganese-copper plate body of a flow divider, when the nickel plating layer is irradiated with a laser, the high-energy-density light beam locally and rapidly heats the silver surface. In air, the high temperature promotes the chemical reaction of silver with oxygen, forming silver oxide (Ag2O or AgO). The specific reaction product depends on the temperature and oxygen conditions:

[0027] Lower temperature or short time heating, silver oxide (Ag2O) is generated, higher temperature or long time heating, silver oxide (AgO) is possible, but AgO is not stable at high temperature, easy to decompose into Ag2O and oxygen.

[0028] Its main oxidation reaction:

[0029]

[0030] Potential side reactions (at high temperature):

[0031]

[0032] The local heating effect of laser makes the silver surface rapidly oxidized, forming a dense oxide layer (mainly Ag2O). This process may be accompanied by the following phenomena: rapid heating and cooling of the laser makes the silver layer microstructure change, increasing the surface activity. High temperature may make the silver surface melt, accelerating the oxidation reaction.

[0033] The thickness of the oxide layer is 0.5-5 μm, and its thickness value can be adjusted by laser power and scanning times. Part of the oxidation gradient transition layer (where the Ni / NiO mixed phase), enhances the bonding force. DETAILED DESCRIPTION

[0034] In order to make the above objectives, features and advantages of the present application more apparent, the specific embodiments of the present application are described in detail below. In the following description, a number of specific details are set forth in order to provide a thorough understanding of the present application. However, the present application can be practiced in many different ways from those described herein without departing from the scope of the present application, and skilled in the art can make similar improvements without departing from the scope of the present application, therefore the present application is not limited to the specific implementation disclosed below.

[0035] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used in the description of the application herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items.

[0036] Example one

[0037] The method for generating an oxide protective film on the surface of a manganese-copper plate body of a flow divider, comprising the following steps:

[0038] a) Pretreatment: surface cleaning and activation of the welded and formed manganese-copper plate body and the red copper plate body;

[0039] Specifically, first, the ultrasonic cleaning is used to remove the welding residues and surface oil stains; then, the shunt is immersed in 10% dilute sulfuric acid solution (40°C, 1-2 minutes) to remove the oxide film and improve the plating adhesion.

[0040] b) electroplating: the metal plating layer is electroplated on the surface of the manganese copper plate body and the red copper plate body, and the nickel sulfamate plating solution (nickel ion concentration 80-100 g / L, pH value 3.5-4.5) is selected, the current density is 2-4 A / dm 2 , the temperature is 50-60°C, the electroplating time is 30-60 minutes, and the thickness of the metal plating layer is 5-20 μm.

[0041] The formula of the nickel sulfamate is as follows: nickel sulfamate 300-400 g / L, nickel chloride 5-10 g / L, boric acid 30-40 g / L, and wetting agent 0.1-0.5 g / L.

[0042] c) laser oxidation: the fiber laser is used, the laser with a wavelength of 1064 nm, a pulse width of 10-100 ns, a power of 50-200 W, a scanning speed of 100-500 mm / s, a spot diameter of 50-100 μm, and a repetition frequency of 20-100 kHz are selected.

[0043] The dense oxide layer is formed by selectively irradiating the electroplating layer by laser, and the thickness of the dense oxide layer is 0.5-5 μm (which can be adjusted by the laser power and the scanning times).

[0044] The shunt produced by the method of generating the oxide protective film on the surface of the manganese copper plate body of the shunt is tested, wherein the salt spray resistance test (ASTM B117) is ≥500 hours without corrosion, and the contact resistance change rate is <0.1% after 1000 hours of aging test.

[0045] Example Two

[0046] The difference between the present example and Example One is only that:

[0047] In the step b), the shunt is plated with silver, the cyanide silver plating solution is selected, the current density is 0.5-1.5 A / dm 2 , the temperature is 20-30°C, the electroplating time is 20-40 minutes, and the 8-15 μm silver layer is formed, which can also achieve the technical effects of Example One.

[0048] The above only describes two embodiments of the present application, and it should be noted that, for those skilled in the art, without departing from the principles of the present application, a number of variations and improvements can also be made, which should be considered as belonging to the protection scope of the present application.

Claims

1. A method for generating oxide protective film on the surface of a diverter manganese-copper plate body, comprising the following steps: a) Pretreatment: surface cleaning and activation of the welded and formed manganese-copper plate body and red copper plate body; b) Electroplating: electroplating a metal coating on the surface of the manganese-copper plate body and red copper plate body; c) Laser oxidation: forming a dense oxide layer by selectively irradiating the electroplated layer with a laser.

2. The method for generating oxide protective film on the surface of a diverter manganese-copper plate body according to claim 1, characterized in that: in step a), the activation is immersing the diverter in a 10% dilute sulfuric acid solution to remove the oxide film and improve the adhesion of the coating.

3. The method for generating oxide protective film on the surface of a diverter manganese-copper plate body according to claim 1, characterized in that: In step b) a nickel sulfamate plating solution is selected, the current density is 2-4 A / dm 2 at a temperature of 50-60 °C and the plating time is 30-60 minutes.

4. The method for generating oxide protective film on the surface of a diverter manganese-copper plate body according to claim 1, characterized in that: The silver plating solution used in step b) is cyanide-based, the current density is 0.5-1.5 A / dm 2 , the temperature is 20-30℃, the plating time is 20-40 minutes, and the silver layer formed is 8-15 μm thick.

5. The method for generating oxide protective film on the surface of a diverter manganese-copper plate body according to claim 1, characterized in that: in step b), the thickness of the metal coating is 5-20 μm.

6. The method for generating oxide protective film on the surface of a diverter manganese-copper plate body according to claim 1, characterized in that: in step c), a laser with a wavelength of 1064 nm, a pulse width of 10-100 ns, a power of 50-200 W, a scanning speed of 100-500 mm / s, a spot diameter of 50-100 μm, and a repetition frequency of 20-100 kHz is selected.

7. The method for generating oxide protective film on the surface of a diverter manganese-copper plate body according to claim 6, characterized in that: in step c), the thickness of the dense oxide layer is 0.5-5 μm.

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