The Property and Thickness Evaluation of High Temperature Resistant OSP Coatings for Lead-free Assembly Processes
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. As the latest generation of the industry standard OSP, the newly developed high temperature resistant (HT) OSP meets the greater lead-free solderability requirements.This paper will introduce the chemistry characterization of high temperature resistant OSP including coating composition analysis, thermal analysis of key azole compounds and OSP coatings, and OSP coating surface analysis. Gas Chromatography-Mass Spectroscopy (GC/MS) is used to determine the small organic compounds entrained in the cross-linked OSP coatings. Thermogravimetric Analysis/Differential Scanning Calorimetry (TGA/DSC) is used to characterize the thermal stability of azole compounds and OSP coatings. X-ray Photoelectron Spectroscopy (XPS) is used to characterize HT OSP oxidation after multiple lead-free reflow processes.This paper will also introduce the robustness of coating thickness control from production experience. HT OSP offers robust and flexible coating thickness control. Thickness analysis shows that OSP coatings exhibit a micro-leveling effect during coating formation and sufficient coating thickness is necessary to guarantee the full protection of copper from oxidation for a variety of substrates treated by different micro-etch processes in the industry. The high temperature resistant OSP coating and robust coating thickness control ensure the excellent reliability for lead-free soldering.
Shenliang Sun John Fudala Robert Farrell Yung-Herng Yau Karl Wengenroth Joseph Abys
Enthone Inc.-Cookson Electronics,West Haven,CT 06516
国际会议
上海
英文
2008-03-17（万方平台首次上网日期，不代表论文的发表时间）