Research On The Additives And Process Of High-speed Silver Electroplating For Lead Frame

High-speed silver electroplating is a commonly used electroplating process in electronic electroplating industry. It is of high efficiency, high-speed, and can be produced continuous. It's now widely used to produce silver plating on lead frame and LED. In the domestic market, most of the high-speed electroplating processes we are using belong to the patented products of foreign companies, for example, Rohm and Haas, Enthone and Umicore. It's difficult to adjust the plating technology according to the requirement of the new plating products. On the other hand, the price is very expensive and the cycle of supply is long. It affects the development of the new product of the electroplating factories. However, the high-speed silver electroplating processes we developed are not as good as the foreign processes. Especially the stability of the plating solution, operating range and the brightness of the plating are not so good. It limits the application of our process in high-speed silver electroplating production line,especially the high-end production line.In this paper, we studied the basic solution of high-speed silver electroplating,additives, process and anti-silver replacement agent, got new high-speed silver electroplating process, the quality of which is fairly to the foreign process. According to the requirements of the new plating products, it is easy to adjust the processes. The research contents are as follows:The compositions and content of the high-speed silver electroplating based solution were determined by screening and optimization. The based solution includes the opening salts, the main salt and free cyanide. The type and content of the wetting agent was determined by salt resistance, wet ability and the foam height. The basic components of the brightening agent were screened by Hull cell experiments. And then the screened components were mixed to make a new kind of brightening agent. The dosage of the new brightening agent in the plating solution was determined by rack plating. At last, we got the best condition of plating processed by single variable method, which includes the temperature, p H and cathode-current density.As the effect of domestic anti-silver replacement agents are not so good, and usually when they are taken into the high-speed silver electroplating solution, they would bring adverse effect to the plating. In order to improve the situation, we organized and summarized some literatures and patents from home and abroad. By the experimentsof open circuit potential tests, the effect of anti-silver replacement agents and the effect of adding anti-silver replacement agents, we studied the effect of thiolactic acid,thiomalic acid, S-1 and thiobarbituric acid. And then we got a new anti-silver replacement agent named BAg-AR.At the basic of determining the composition of high-speed silver electroplating solution, we tested the quality of the plating solution and the plating coating, the results are as follows: the plating solution developed by us is of good dispersal capacity, high cathode efficiency and good stability. The surface of the plating coating is even and bright, it's also with high hardness, high purity and good weld ability. The overall performances are fairly to the foreign products.