IMMERSION TIN AS A COST-EFFECTIVE AND RELIABLE SURFACE FINISH FOR PB-FREE AUTOMOTIVE ELECTRONICS APPLICATIONS -PHASE II INVESTIGATIONS

摘要

Few events in the electronics manufacturing industry have caused such a widespread impact as the recent adoption of Pb-free initiatives. Nearly every aspect of PWB and IC substrate fabrication and assembly has been affected, either directly or indirectly. One of the most widely studied areas is that of the PWB and package substrate surface finish. Exemptions within the automotive electronics segment have not stopped major OEMs from considering and preparing for the eventual transition to the Pb-free world. As such, alternative surface finishes are being examined by some Tier-1 suppliers to meet the extreme requirements for automotive PWB and substrate applications. Immersion tin is one surface finish receiving considerable attention, particularly for automotive applications. Unlike the traditional hot air solder leveling (HASL) process, immersion tin provides an extremely planar finish on the copper pads, making it very suitable for SMT applications. Use of immersion tin does not compromise the solder joint by introducing (or increasing) ternary metals that may affect solder joint reliability. Furthermore, unlike organic coatings, immersion tin provides a surface that is easily detectable by common AOI techniques, has excellent wettability for both reflow and wave applications and is readily suited for in-circuit testing methods.