LEAD-FREE SOLDERS FOR ELECTRONIC ASSEMBLY

Progress towards the development of lead-free soldering processes as replacements for traditional technology based on Sn-40Pb solder is described. Factors considered include the economic and supply situations for the candidate metals, as well as the technical questions surrounding the replacement for a solder that has been used since Roman times. Alloys based on the binary Sn-Ag and Sn-Cu eutectic compositions showed the greatest potential as replacements for Sn-40Pb in lead-free wave and reflow soldering processes. However, it emerged clearly that all components of the solder joint, including the solder alloy, the metallizations on both boards and components, and the fluxing system must be considered together when designing a lead-free soldering process.