Investigation on Fatigue Life of Non-Symmetric Solder Joints in Chip Resistors

This study is aimed to find correlation between the fatigue life and solder joint shape with respect to component location in experimental and numerical approaches. The test vehicle was mounted chip resistors, R1005
$(1.0\times 0.5\ \mathrm{m}\mathrm{m})$
, which were intentionally misplaced from the center in the component's length and width directions. The solder joints at two terminations on a single resistor were artificially induced to unsymmetrical solder shapes with respect to the component locations. The test assembly was then subjected to the thermal shock loading
$(-55^{\circ}\mathrm{C}$
to
$150^\circ \mathrm{C}$
, dwell time 3 min, 6 cycles per hour). The results were analyzed to investigate the effect of overhanging or skewing of component on the thermal fatigue life and the change of solder joint shapes regarding on the component locations. It is observed that overhanging in x axis had an overall reduction in thermal reliability than in y axis and its difference became larger once chip resistor was more overhung. Overhanging in both
$\mathbf{x}$
and
$\mathbf{y}$
axes was predicted the worst fatigue life while fatigue life of chip resistors in fail criterion region dropped 39% down respectively.