Double pulse plating solution for preparing lead-free Sn-Cu alloy solder and plating process

Abstract

The invention discloses a double pulse plating solution for preparing lead-free Sn-Cu alloy solder and a plating process. Metal Si wafers are put in a plating solution, and a dual-pulse current is communicated for double pulse plating. The plating solution comprises chemical compositions: 0.4-0.5mol / L of ammonium citrate tribasic, 0.2-0.25mol / L of stannous chloride dehydrate and 0.025-0.035mol / L of copper chloride dihydrate which are analytically and purely prepared. The parameters of the double pulse plating solution comprise: frequency is 80-120Hz, the duty ratio of double pulses is 18-22%, positive / negative pulse time is 900-1100 / 90-110ms, and current density is 9-11mA / cm2. The method reasonably selecting a plating solution formula and pulse electrodeposition process parameters to prepare the Sn-Cu alloy solder improves the plating rate, and the prepared Sn-Cu alloy solder has the advantages of low roughness, uniform thickness, level surface, less pores, dense structure and small stress in a plating layer.

Description

technical field [0001] The invention relates to the technical field of alloy solder preparation, in particular to a double-pulse electroplating solution and an electroplating process for preparing lead-free Sn-Cu alloy solder. Background technique [0002] For a long time, Sn-37Pb (mass fraction) alloy solder has been widely used in the electronics industry for its low cost, low eutectic temperature (183°C), good electrical, mechanical and chemical properties. However, with the enhancement of people's awareness of environmental protection, at the same time, recent studies have shown that once lead ions discharged into the atmosphere or groundwater due to various reasons enter the human body, it may cause mental retardation, reproductive organ disorders, cancer, hypertension and other diseases in children . my country has now become the third largest producer of electronic products in the world. A large amount of lead enters people's daily life along with household appliance...

AI Technical Summary

Problems solved by technology

Solder paste connection is cheap and easy to operate, but the positioning and thickness control of the solder is not guaranteed, and the solder is easily oxidized, which is not conducive to substrate bonding

Vacuum deposition techniques allow better process control and reduce oxide generation, but are quite expensive and time-consuming, so neither technique is suitable for large-scale preparation of Sn-based lead-free solders

[0005] Although the traditional electroplating technology (DC electroplating, DC periodic reversing electroplating) overcomes the shortcomings of the above methods (coating solder paste or vacuum deposition technology) to a certain extent, the uniformity and deposition rate of the electroplating layer are not ideal. Moreover, the internal stress and porosity are relatively large

At the same time, most of the electroplating solutions used in my country's electroplating industry contain toxic components (such as cyanide in the gold plating solution), and various additives are added to the electrolyte. The solution components are complex, and the stability of the electroplating solution is poor, resulting in solder preparation costs. High, improper treatment of electroplating waste liquid will also cause harmful effects on the environment

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