Abstract
It shall be very important in future that the bare copper surface preparation of SMT boards shall be treated with both corrosion inhibitors and protective coating so called pre-flux in respect to the solderability, reliability of solder joints and mounting and working ability. In this paper, kinds of corrosion inhibitors, the effect of a softetchant on the degreased surface and heat resistance of pre-fluxes are studied, and the summary of the results were that the development of both the process and the preparation agent with good enough protecting effect might be possible in comparison with the solder hot air leveling effect. The process is as follows: degreasing→washing with DI water→softetchang→washing with DI water→preparation with corrosion inhibitor→washing with DI water→mild hot air drying→pre-flux coating. It is clear that etching depth should be controlled at the range of 0.5-3.0μm, a corrosion inhibitor should have the lower melting point than the soldering temperature, preferably it should be lower than the melting point of a solder, the pre-flux should not react with copper, and the heat stable synthetic resins are suitable for the said flux.
