The Research On Environment-friendly Plated-through-hole Technics

At present, formaldehyde has been widely used as reducing agent in electroless copper plating process but formaldehyde is a carcinogen and it can be easily volatile, too much exposure in it will have a negative impact on the human body, in the producing process and the dispose process of waste water and residues have a lot of security risks. Therefore, the research and development of an environment-friendly electroless copper plating process to replace the formaldehyde electroless copper plating process is very important. This paper aims to develop an environment-friendly non-formaldehyde electroless copper plating process make its technique operability can satisfy the existing requirements of production and environment protection.A stable non-formaldehyde PTH(Plated-Through-Hole) electroless copper plating process is studied in this paper, in the process, using glyoxylic acid as a reducing agent to replace formaldehyde, copper sulfate as copper sources, EDTA·2Na and Tart as a complexing agent, potassium ferrocyanide and 2,2'-bipyridine as a stabilizer. By using single factor method, the effect of the major components (the main salt, complexing agent, reducing agent, etc.) and operating conditions (temperature, pH) on the plating rate, bath stability and coating properties (color coating, bonding, light brightness, homogeneity), as well as the effect of stabilizing agent (different types of stabilizer and stabilizer concentration) on the plating rate and operating parameters on the coating performance are discussed in glyoxylic acid bath of electroless copper plating system.At last,by using backlight test, coating binding force test, scanning electron microscopy analysis tested the coating quality of the productsStudy shows that:the solution composition and operating conditions all have great effect on bath performance and coating performance. the addition of methanol can increase the stability of plating solution, to some extent, the ratio of 2,2'-bipyridine and potassium ferrocyanide will effect coating appearance. In the optimized process conditions:copper sulfate concentration is 16g/L, EDTA-2Na concentration is 24g/L, Tart concentration is 15g/L, glyoxylic acid concentration is 13g/L, methanol concentration is 6g/L, potassium ferrocyanide concentration is 10mg/L,2,2'-bipyridine concentration is 10mg/L, pH is 12.5, Temperature is 50℃, plating time is 30min. Under these conditions, we can get painstaking and uniform coating. The process does not use formaldehyde, non-polluting, has good environmental effects and social effects and broad application prospects.