The impact of thermal cycling regime on the shear strength of lead‐free solder joints

Abstract

PurposeThe purpose of this work is to undertake a comparison of accelerated test regimes for assessing the reliability of solder joints, in particular those made using lead‐free solders.Design/methodology/approachIdentical samples of 1206, 0805 and 0603 resistors were subjected to six different cycling regimes to investigate the effect of thermal excursions, ramp rates and temperature dwells.FindingsThe most damage to joints was found to be caused by thermal cycling between −55 and 125°C, with a 10°C/min ramp rate and 5 min dwells. Large thermal excursions were shown to give faster results without compromising the failure mode.Research limitations/implicationsSimilar degrees of damage in the lead‐free solder joints were experienced from thermal shock regimes with ramp rates in excess of 50°C/min. However, these regimes, although faster to undertake, appeared to cause different crack propagation modes than observed with the thermal cycling regimes. However, these differences may be small and thermal shock testing may still be used to differentiate between, or enable ranking of, the effects of changes to materials or processes on the reliability of the solder joints. Hence, it is envisaged that if a wide range of conditions are to be tested a first sift can be completed using thermal shock, with the final work using typical thermal cycling conditions.Practical implicationsThe difference between the SAC (95.5Sn3.8Ag0.7Cu) and SnAg (96.5Sn3.5Ag) solder alloy results across all types of cycles showed very little difference in the rates of joint degradation.Originality/valueThis paper compares relative reliability (remaining shear strength) of three chip components soldered with two lead‐free alloys based on various thermal cycling conditions.