Influence of intermetallic compounds growth on properties of lead-free solder joints

This article deals with the growth of intermetallic compounds (IMCs) in solder joints and influence of these IMCs on properties of soldered joints. The test specimens of printed circuit boards (PCBs) with different surface finishes were made for this experiment. Tin_G (galvanic tin), Tin_C (immersion tin), Cu (pure copper), OSP (organic solderability preservative) and ENIG (electroless nickel immersion gold) surface finishes were chosen. The soldered joints were created on the test specimens by reflow soldering process concretely vapour-phase soldering. The surface mount solder joints of LCCC resistor of size 1206 were studied. Two lead-free solder paste and one tin-lead solder paste were chosen for research of IMCs and their influence on properties of soldered joints. The test specimens were exposed to elevated aging for research of IMCs growth in solder joint. The specimens were thermal stressed in hot air oven at the temperature of 150°C for a periods of 0, 1, 2, 4, 8, and 16 days. The shear test was used for research of IMCs growth influence on strength of soldered joints. The results of analysis of IMCs in solder joints using confocal and metallographic microscopes and the results of shear strength measurement will be presented in this article.