Use of Organic Metal to enhance the operating window and solderability of immersion tin

As an alternative to hot air levelling, a fundamentally new surface finish chemistry and process for solderability preservation of printed circuit boards is described: a pretreatment of the copper followed by an optimized formulation of an immersion tin. The precise and reproducible surface finish formation offers reliable solderability, economic and technical advantages for all kinds of PCBs, even for those with the most modern miniaturized structures. The deposition chemistry and ageing properties of the new Organic Metal/tin surface is discussed, based on electrochemical, wet chemical and electron microscopy studies. The results culminate in an almost complete basic understanding of the tin chemistry and the surface finish performance.