Soldering ability or Solderability
While the environmental reasons for eliminating lead from solder are laudable, the switch has put electronics manufacturers on the back foot when it comes to determining the reliability of their products. Tried-and-trusted test methods – satisfactory for qualitative assessment of tin/lead joints – no longer apply, and new techniques must be put in place. IPC and IEC member Graham Naisbitt explains
Removing lead from electronics may be a good idea, but the transition to lead-free solder does dramatically alter the electronics assembly procedure, particularly for high-reliability products. Tin/lead solder joints have been comprehensively characterised over many decades, and manufacturers of products for safety-critical or life- dependent applications are able to reassure end users of their reliability. This is not the case for lead-free alternatives. Although staff at standards bodies such as IPC and IEC have devoted many man-months to characterising solder joints formed using their recommended lead-free alloys, and proposing test regimes to ensure their reliability there is much more to do.
In addition, high-reliability products such as avionics systems or utility meters can have a life expectancy of up to 25 years. This means they are very likely to be subject to repair during their operational life. Rework procedures using tin/lead solder are proven and reliable, while questions inevitably remain about those formed from lead-free alloys.
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