The Research Of Electroless Tin Plating On PCB

Firstly, by single factor analysis of the composition in electroless tin plating solution, including sulfuric acid bath and methane sulfonic acid, this paper discusses the effect of composition in the electroless tin plating solution on tin coating thickness and surface microtopography. Meanwhile, determined effect of the composition in pre-plating bath on tin coating thickness, surface microtopography and coating binding power throught single factor experiment of pre-plating solution. the result is that pre-plating technology can not only enhance the tin coating uniformity coefficient, but also enhance the binding power of the tin coating and the coating with pre-plating technology can reach all the requirement of solderability coating. Respectively design two kinds of five factor four level Orthogonal test, including sulfuric acid type and methane sulfonic acid type, after analyzing these two orthogonal test result, gets the best formula of sulfuric acid solution and methane sulfonic acid solution, and discusses the effect grade of solution compositions on tin coating thickness, surface topography and binding power, and identify the most fluence factor.Mack sure the rule cause that how this additives effect tin coating on thickness and surface topography by screening each kind of additives, including reducing agents, complexing agent, surface active agent, anlioxidants and brightener, and then give out a method that how to choose these kinds of additives and every additive's best formula. At last, make sure the complete composition of electroless tin plating solution, with this formula, we can acquire an acceptability tin coating which plating temperature is 45℃and plating time is 15 minutes, the thickness of this coating is 0.8μm.Then, study the functions of compositions and the effect of the compositions on coating during charging reaction by i~t curve meanwhile during reduction by Taffel curve and Cathodic Polarization curve. Finally, indentify the whole flow of electroless tin plating by analysis XRD, XPS, SEM results, and stressly analysis the flow of reducion stage. Bring forward adsorption-complexation mechanism of thiourea by analysis EIS cuvre, Taffel curve, CV curve, and give out a simulating circuit by fitting EIS curve, that establish the foundation of further study in...