Reliability testing of lead-free solder joints

For studying the reliability of lead-free SnAgCu solder joints, reliability test were performed on test structures obtained by three variants of PCB surface finishing: Copper, Gold and HASL (Hot Air Solder Levelling), respectively, achieved by an industrial process and, in parallel, by in laboratory (research) conditions. Two types of reliability tests were used: (i) Thermal cycling at -55°C / +125°C / 30 minutes at each step; (ii) Cycling damp heat at -40°C / 85°C and 85%RH. The results clearly show that both the industrial process and the research conditions ensure the higher reliability level for the HASL variant.