This is a four-part series. Part 1 outlined the two primary options in implementing lead-free electronics, while Part 2 provided the viable solder alloys for either of two approaches. Part 3 explained successful lead-free implementation without higher temperature, and Part 4 summarizes critical production parameters. As highlighted in my January column, reflow temperature below 238℃ is a proven SMT manufacturing condition. Therefore, the solder joint alloys that can be reliably soldered below 238℃ can serve as a replacement for 63Sn37Pb without requiring any changes in process, boards and components. The relationship between the process and alloy melting temperatures (or add-on temperature) used for 63Sn37Pb still is essentially applicable to lead-free. Benefited by recent advancements in reflow oven capabilities, the solder alloy with melting temperature below 213℃ is expected to readily perform its purpose under existing process conditions without requiring changes. This is the premise of designing solder alloys at the outset.
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