ABSTRACT: Leadless chip resistor (LCR) assemblies were manufactured using both traditional tin-lead (Sn37Pb) and lead-free (Sn3.8Ag0.7Cu)
solders. The leadfree test vehicles were assembled using three different cooling rates: 1.6°C/sec, 3.8°C/sec, and 6.8°C/sec.
They were then exposed to accelerated thermalcycling (ATC) tests between 0°C and 100°C with a 10–14°C/min ramp rate and a
5-min dwell time. The test results indicated that these lead-free solder joints had better creep-fatigue performance than
the tin-lead solder joints. The LCR built with the medium cooling rate showed the longest fatigue life compared with the resistors
built with the normal cooling rate of 1.6°C/sec and the higher cooling rate 6.8°C/sec. The number of cycles to failure was
significantly correlated to the void defect rate. Failure analyses were done using cross-sectioning methods and scanning electron
microscopy (SEM). Finite-element models were built to analyze the inelastic, equivalent strain range in solder joints subjected
to thermal-cycling conditions with different degrees of solder wetting. The results indicated that poor wetting increases
strains throughout the joint significantly, which is in accordance with the ATC results.
Journal of Electronic Materials 11/2004; 33(12):1497-1506. · 1.47 Impact Factor