Are there any long-tern reliability implications of “re-tinning” conventional SnPb components using lead-free materials and then processing them using a lead-free process?
A35. There are no specific data here, but there are two aspects to be considered – component functionality, and solder joint performance. Component functionality: No additional thermal excursion is desirable since it may cause damage or de-lamination within the component; samples can be checked after tinning using scanning acoustic microscopy (SAM). For high reliability products it is recommended that long-term component reliability is undertaken. Solder performance: this is unlikely to be a major issue. Such data as there are suggest that if bismuth is not involved then it is probably better not to waste time and money on costly retinning. Hence try and avoid the use of bismuth-containing materials and go ahead without tinning. However, some retinning may be necessary because of “lifetime buys” of components with SnPb terminations, which will be used, when the restriction of the RoSH Directive comes into force requiring no more than 0.1 wt% lead in any homogenious material. In this ca
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