Lead-Free Solder Paste with ICT-Probe Penetrable Residues

摘要

Because in-circuit testing provides an efficient way of evaluating electronic assemblies, it is increasingly important in the electronics industry. In order to test connections made with no-clean sol ier paste, the post-reflow flux residue must be easily penetrated by ICT pin-probes. Recent advances in materials for electronics assembly include lead-free, environmentally friendly solders. However, many lead-free solders, particularly the tin-silver-copper alloys recommended by NEMI, have higher melting points than conventional eutectic solder. The hotter reflow conditions required for lead-free solder paste influence the consistency of the solder paste flux residue and its suitability for in-circuit testing. These hotter reflow conditions often produce hard, brittle residue that is difficult to pin probe. ICT probe penetrability data for lead-free solder paste residue are presented for different reflow conditions and post-reflow times, showing that lead-free solder paste can be suitable for post-reflow in-circuit testing. A discussion of desirable characteristics for solder paste flux residue with regard to in-circuit testability is also given.