ISSUES IN THE REPLACEMENT OF LEAD-BEARING SOLDERS

The use of soft solders, particularly those containing lead, dates back nearly 5,000 years. Solders similar to the materials used to seal the aqueducts of ancient Rome are now an important building block in the manufacture of high-speed computer assemblies. This history attests to the technological versatility of soft solders and, in particular, the solder alloys that contain lead. However, the health effects of prolonged exposure to lead have also been documented; measures to limit human exposure-at the work place and indirectly through the environment-are being considered. The successful introduction of lead-free solders in to future electronic products will rely heavily upon their solderability, which can be evaluated by test procedures such as the meniscometer/wetting balance technique and the capillary flow test.