There are countless challenges in making mobile electronics more reliable, including the thin form factor of cellphones and tablets that is forcing mobile computing packages to get thinner. Using coreless ball grid array (BGA) substrates decreases the overall height of the component, but it presents manufacturing challenges and potential reliability concerns when subjected to thermal cycling. This study presents results from tests performed on a coreless 25 mm by 27 mm BGA package with a relatively large die and stiffener ring that survived over 8,000 temperature cycles without failure. In order to investigate the reason behind this robust performance the coefficient of thermal expansion (CTE) of the part was measured using digital image correlation (DIC). The DIC results indicated that this combination of die size, package size, and stiffener ring reduces the CTE mismatch between the BGA package and printed circuit board (PCB).