"Behind the Scenes" of Effective OSP Protection in Pb-free Processing

Advancements and evolutions in printed circuit board manufacturing, design, and electronics assembly have driven new research on high temperature organic solderability preservative (HT OSP) surface finishes. More specifically, developments in OSP chemical processes are aimed at producing a durable finish which ensures that a board surface retains solderability through more challenging and harsh Pb-free assembly conditions. From this, it is clear that advancements in OSP processing and coating performance require a solid understanding of the mechanisms associated with coating formation and thermally driven degradation. This work examines and describes OSP structure and composition and how it is affected by heat treatments. Additionally, mechanisms of degradation of OSP are proposed along with possible strategies to remedy it.