The Characterization of Novel High Temperature Resistant OSP Coatings for Lead free Processes by Comparing to Other Commercial OSP Coatings

摘要

In order to meet the growing requirement of eliminating lead from electronics, the printed wiring board (PWB) industry is migrating from hot-air-leveled solder (Sn/Pb) to lead free compatible alternative final finishes. Among the available alternatives which include organic solderability preservative (OSP) immersion silver, immersion tin and electroless nickel/immersion gold, the OSP type coating is considered to be one of the leading candidates because of its excellent solderability, ease of processing and low cost. This paper uses Gas Chromatography-Mass Spectroscopy (GC/MS), Thermogravimetric Analysis (TGA), and X-ray Photoelectron Spectroscopy (XPS) to characterize the relative thermal properties of a novel high temperature (HT) resistant OSP coating. The GC work performed in this study clearly shows the key organic components in the HT OSP coating that affects solderability. The GC work also shows the alkyl benzimidazole-HT used in HT OSP is of the lowest volatility. The accompanying TGA data also illustrates that the HT OSP coatings have a higher decomposition temperature compared to existing industry standard OSP coatings. The XPS shows that HT OSP has only about 1% increase of oxygen content after five Lead Free reflow cycles. In combination, these improvements are assessed relative to the industry needs to meet the performance challenges of lead free soldering.