A soldering reliability study: a comparison among alloy-surface finish combinations considering different component packaging
Keywords:reliability test, lead-free, soldering alloy, surface finish, Weibull statistical models
The assembly process of components in a Printed Circuit Board (PCB) requires exposed copper areas coated with a surface finish. In the past, the predominant surface finish in the PCB industry was traditionally Hot Air Solder Leveling (HASL) combined with tin-lead as the soldering alloy. Besides replacing the soldering paste containing lead, the PCB industry has also been active in seeking surface finish options as an alternative to HASL. This
research proposes a detailed and comparative study on the reliability behavior of a solder joint by considering different surface finishes and several component packages. In particular different combinations of alloys, (e.g. tin-lead, tin silver-copper) and surface finishes, (e.g. HASL; Electroless Nickel Immersion Gold known -ENIG; Immersion Tin I-Sn; Organic Solderability Preservative - OSP), considering four types of components, were evaluated through Weibull distributed data and statistical models for reliability, with the aim to appraise how
the type of package, or geometry of the joint are able to affect the soldering reliability. Two-by-two comparisons of alloy-surface finishes were carried out and the statistical results were presented. The tin-silver-copper alloy, with related finishes, reveals higher reliability than the boards soldered with the traditional alloy-finish combination.