EVALUATION OF TIN COPPER (SnCu) MODIFIED LEAD-FREE SOLDER ALLOYS FOR WAVE SOLDER PROCESSES

摘要

The plated thru hole wave soldering technology has been a highly characterized, mature process for the electronic industry for many years. The introduction of lead-free solder alloys and processes due to the European Union RoHS Directive has resulted in a reevaluation of wave solder process materials, process parameters and equipment requirements. One aspect of the renewed investigations of wave solder processes is the solder joint integrity of plated thru hole components as a function of the various lead-free solder alloy choices. The electronics industry has embraced the SAC305 lead-free solder alloy as a primary material choice. However, a significant amount of industry resources are being expended in investigating the tin-copper modified alloy options. This paper documents an investigation to determine the plated thru hole thermal cycle solder joint integrity of several candidate tin-copper modified wave solder alloys. Test vehicles were thermal cycled in accordance with the IPC-9701 specification for a total of 6593 total cycles. Metallographic cross-sectional analysis was conducted on the test vehicles to determine a damage severity ranking for each candidate Pbfree wave solder alloy. The test results show that all candidate Pbfree wave solder alloys would provide acceptable solder joint thermal cycle integrity for plated thru hole components but at a slightly lower overall reliability level in comparison to the Sn63Pb37 baseline solder alloy.