Residues in printed wiring boards and assemblies

This paper is an examination of residues on printed wiring boards and printed wiring assemblies. Sources of residues are illustrated and the effects of various residues are discussed. Case studies are presented for bare board cleanliness issues, water soluble flux and aqueous cleaning processes, and low solids flux (no‐clean) processes, with and without cleaning. The case studies reflect lessons learned in various process troubleshooting efforts. Residues in this paper were characterized using advanced ion chromatography procedures. In addition, some data on surface insulation resistance (SIR) are presented.