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Semi-bright lead-free chemical tinning liquid and using method thereof

A lead-free chemical and chemical tin plating technology, applied in the field of chemical plating, can solve the problems of continuous self-catalytic deposition of tin, high hydrogen evolution potential of tin, unsatisfactory repeatability, etc. The effect of obvious refinement and wide range of process parameters

Inactive Publication Date: 2010-06-02
KUNMING UNIV OF SCI & TECH
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

However, due to the high hydrogen evolution potential and low catalytic activity of tin, if formaldehyde, sodium hypophosphite, borohydride and other reducing agents are used alone, continuous autocatalytic deposition of tin cannot be achieved, and thicker coatings cannot be obtained.
With a strong reducing agent, such as Ti 3+ , V 2+ , Cr 2+ Electroless tin plating has been reported, but due to low deposition rate, poor stability, unsatisfactory repeatability, and high price, it has not been applied industrially

Method used

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Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0021] The formula of electroless tin plating solution is: stannous sulfate 15g / L; sulfuric acid 50ml / L; ethylenediaminetetraacetic acid 3g / L; thiourea 80g / L; citric acid 10g / L; sodium hypophosphite 80g / L; gelatin 0.3 g / L; benzaldehyde 0.5ml / L;

[0022] The process conditions of the electroless tin plating solution are: the temperature of the plating solution is 88±2°C, the pH value is 1.0, the electroless plating time is 3 hours, and the loading capacity of the plating solution is 1.2dm 2 / L.

[0023] The thickness of the electroless coating in Example 1 is 26.4 μm, the appearance is silvery white, the mass percentage of tin is 93.4wt%, and the porosity is lower than 4 / 6cm 2 . In a tin-lead alloy in which the flux is 25% rosin isopropanol and the solder is 60% tin + 40% lead, the wetting time is less than 3s, and the solderability is better. After passivation treatment, the appearance and color of the electroless coating will not change after being placed in the atmosphere...

Embodiment 2

[0025] The formula of electroless tin plating solution is:

[0026] Stannous sulfate 20g / L; sulfuric acid 40ml / L; ethylenediaminetetraacetic acid 3g / L; thiourea 100g / L; citric acid 20g / L; sodium hypophosphite 80g / L; gelatin 0.3g / L; benzaldehyde 1.0ml / L;

[0027] The process conditions of the electroless tin plating solution are: the temperature of the plating solution is 88±2°C, the pH value is 1.5, the electroless plating time is 3 hours, and the loading capacity of the plating solution is 1.2dm 2 / L.

[0028] The thickness of the electroless coating in Example 2 is 22.7 μm, the appearance is silvery white, the mass percentage of tin is 92.8wt%, and the porosity is lower than 4 / 6cm 2 . In a tin-lead alloy in which the flux is 25% rosin isopropanol and the solder is 60% tin + 40% lead, the wetting time is less than 2s, and the solderability is good. After passivation treatment, the appearance and color of the electroless coating will not change after being placed in the a...

Embodiment 3

[0030] The formula of electroless tin plating solution is:

[0031] Stannous sulfate 30g / L; sulfuric acid 30ml / L; ethylenediaminetetraacetic acid 5g / L; thiourea 120g / L; citric acid 25g / L; sodium hypophosphite 100g / L; gelatin 0.5g / L; benzaldehyde 1.0ml / L;

[0032] The process conditions of the electroless tin plating solution are: the temperature of the plating solution is 88±2°C, the pH value is 2.0, the electroless plating time is 3 hours, and the loading capacity of the plating solution is 1.2dm 2 / L.

[0033] The thickness of the electroless coating in Example 3 is 32.7 μm, the appearance is silvery white, the mass percentage of tin is 94.6wt%, and the porosity is lower than 4 / 6cm 2 . In a tin-lead alloy in which the flux is 25% rosin isopropanol and the solder is 60% tin + 40% lead, the wetting time is less than 2s, and the solderability is good. After passivation treatment, the appearance and color of the electroless coating will not change after being placed in the ...

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Abstract

The invention discloses new semi-bright lead-free chemical tinning liquid and a using method thereof. A semi-bright silver tin-copper alloy chemical plating layer is obtained on copper and copper alloy matrix. In the chemical plating liquid, tin sulfate is used as a main salt, thiourea is used as a main complexing agent, citric acid is used as an auxiliary complexing agent, sodium hypophosphite is used as a reducing agent, ethylene diamine tetraacetic acid is used as an antioxidant, sulfuric acid is used as a stabilizing agent, gelatin is used as a leveling agent, and benzaldehyde is used as an auxiliary brightening agent. The pH value of the plating liquid is 0.8 to 2.0, the temperature of the plating liquid is between 80 and 90 DEG C, the carrying capacity of the plating liquid is 0.8 to 1.5dm2 / L, and the mechanical stirring speed is 50 to 100 rpm. The continuous self-catalytic deposition of tin is implemented on the copper and copper alloy matrix, plating layers of different thicknesses can be obtained by controlling the chemical plating time, and the deposition speed is high; crystalline grains are obviously refined, the surface flatness of the plating layer is improved, and the plating surface area is large; the plating layer and the matrix are combined firmly; and after passivating treatment, the change resistance of the plating layer is high. The technology has broad application prospect in products such as deep hole pieces, blind hole pieces, small-sized electronic parts and components which are difficult to process, printed circuit boards (PCB) and the like.

Description

technical field [0001] The invention relates to the technical field of electroless plating, in particular to the technology of electroless tin plating. Background technique [0002] Tin coating is a coating with good solderability and certain corrosion resistance, which is widely used in electronic components and printed circuit boards. At the same time, due to the stability of tin to organic acids and the harmlessness of tin compounds to the human body, it is also widely used in the food industry. The tin coating can be prepared by electroplating, immersion plating and electroless plating. Immersion tin plating is easy to operate and low in cost, but the thickness of the coating is limited, generally only 0.5 μm, and the plating solution is easily poisoned, which cannot meet industrial requirements. Electrolytic tin plating cannot process deep-hole parts, blind-hole parts and small electronic components that are difficult to handle; the electroless tin plating layer has u...

Claims

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Application Information

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IPC IPC(8): C23C18/52
Inventor 徐瑞东王军丽
Owner KUNMING UNIV OF SCI & TECH
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