This article is intended to address the issues involved in hand soldering using these new materials, whilst maintaining joint quality. It is as well to remember that the failure of a single soldered connection has the potential to disrupt a complete electronic system. Developments in Solders One of the most important characteristics of a solder alloy is its melting point. The actual value is relevant, but more important is the range of transition from liquid to solid. Solders are predominantly alloys of tin, which has a melting point of 232 C. Other metals are added to produce the desired physical characteristics at an economic cost, and to achieve a specific melting point.
Every alloy has a proportional mix where the rapid transition described above exists.
This ability to produce different melting points is a real advantage to the engineer attempting to rework very dense PCBs. A thorough treatment of solder alloy composition and other related topics can be found in reference 2. Lead is widely used in solder alloys, but environmental concerns mean this is unlikely to continue. The toxic nature of lead on all forms of life is well understood, and with landfill sites containing more old electronics, the polluting potential is clear. Both the automotive and telecomm industries have medium term plans to remove lead from their products.