IPC SMC-WP-005:1997

The acceptance and use of Organic Solderability Preservatives (aSPs) as replacements for Hot Air Solder Leveling (HASL) continues to grow. aSPs selectively protect and maintain the solderability of a PCB's copper features (i.e. SMT pads, through-holes) by providing thermal protection against degradation during assembly.

Historically one class of aSP, the benzotriazole inhibitors, has been successfully used by a number of major OEMs in select assembly applications requiring a single heat excursion. During the past five years a new upgraded class of aSP, the substituted benzimidazole, has proven to yield additional benefits to PCB fabricators while addressing a diversity of processing challenges encountered by PCB assemblers and OEMs.