Study on Soldering Alloy Structure Influence on Whiskers Germination and Grow Process in Joints Executed Using Tin Base Soldering Alloys

Abstract

Electronic components soldered with tin base alloys are subject to whiskers formations after an operation period, which produced failures by short circuits. The main factors which determine formation of whiskers are soldering alloy characteristics, substrate alloys which is placed on the surface of the PCB boards and not the least the working environment. Soldering alloy has a major influence on germination and growing whiskers process, by its nature and grain form, dimensions and orientation. Given the preliminary research carried out to diminish the formation of these defects, was proposed to realize these soldered joints using new soldering alloys obtained by melt-spinning method, which have a nanocrystalline, quasi-crystalline or even amorphous structure. In this paper are presented some results obtained on following the influence of soldering alloy structure over whiskers germination and growing process, by simulating the operation conditions according to applicable standards. Were obtained soldered joints on copper plates using a commercial soldering alloy as well as soldering alloys base on Sn-Cu-Ga, Sn-Cu-Ni, Sn-Cu-CO families, obtained by melt-spinning method. Soldering was performed using a soldering iron and after this process, the soldered joints were placed in an incubator under controlled temperature and humidity conditions. Performing SEM analyzes on soldered joints subject to the above treatment, was observed that formation and growing of whiskers diminished with decrease of the grain size.