Lead-free Soldering System in Reflow, Wave and Wire Soldering Technology Under Conventional Soldering Temperature

摘要

This paper reports the outline of lead-free soldering systems from reflow and wave soldering to wire soldering, using Sn3.0Ag0.5Cu solder. The Sn-Ag-Cu lead-free solder alloy, especially Sn3.5Ag0.7Cu, has great advantage of total manufacturing capability from paste, ingot and to wire. Sn3.5Ag0.7Cu has been evaluated as the standard Sn-Ag-Cu solder alloy by many research projects. However, there are some patent problems associated with this solder. In order to avoid these patent problems, Sn-Ag-Cu alloys of 0.5% higher silver content, Sn4Ag0.5Cu, and 0.5% lower silver content, Sn3Ag0.5Cu, were evaluated. The patent problems may not be severe, but it is worth evaluating the capability of a cheaper solder, with 0.5% lower silver content, in an actual production setting. A major difficulty of this Sn-Ag-Cu lead-free solder is its high melting temperature that affects the performance of lower heat resistance devices. We challenged the capability of Sn3.0Ag0.5Cu in addition to the reduction in cost of material, using the conventional soldering temperature and also new reflow, wave and manual wire soldering equipment and method. All soldering processes had been evaluated and found capable of using the same soldering temperature for Sn-Pb solder.