Influence of No-Clean Flux on the Corrosivity of Various Surface Finishes After Reflow

Abstract

High-quality soldered joint is necessary for the trouble-free operation of electronic equipment. The quality of the soldered joint is determined by several parameters. One of the parameters is the type of used flux. There are no-clean fluxes and fluxes that must be cleaned after the soldering process. Today, no-clean fluxes are widely used. This work is a continuation of the study [1] and it is focused on studying the effect of flux aggressiveness on commonly used PCB surfaces such as electroless nickel immersion gold (ENIG), immersion tin, and organic solderability preservative (OSP). Five fluxes with different classifications were investigated in the work: Weller Lötwasser, Topnik RF800, Topnik TE - 400, Topnik ESW 32, and Topnik LP-1. The most aggressive influence showed no-clean fluxes Topnik TE-410 and Topnik LP-1. These fluxes corroded the OSP surface by at least 0.5 $\mu$m. The results also showed the most resistant type of surface finish was ENIG and the most susceptible to no-clean flux aggressiveness was OSP.