ISSUES IN THE REPLACEMENT OF LEAD-BEARING SOLDERS

The use of soft solders, particularly those containing lead, dates bac k nearly 5,000 years. Solders similar to the materials used to seal th e aqueducts of ancient Rome are now an important building block in the manufacture of high-speed computer assemblies. This history attests t o the technological versatility of soft solders and, in particular, th e solder alloys that contain lead. However, the health effects of prol onged exposure to lead have also been documented; measures to limit hu man 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 soldera bility, which can be evaluated by test procedures such as the meniscom eter/wetting balance technique and the capillary flow test.