Effect of component standoff height on thermo-mechanical reliability of ball grid array (BGA) solder joints operating in high-temperature ambient

Effect of standoff height (SH) on thermo-mechanical reliability of solder joints in miniaturised surface mount components in consumer electronics which operates in high-temperature ambient is studied. This work investigates the effect of CSH on ball grid array (BGA) solder joints which operates in high homologous temperature in mission critical systems and seeks to utilise the findings of this investigation to minimise the accumulated strain energy density in the joints. The study focuses to underpin the relationship between CSH and shear strength of the joints while it determines the effect of long high-temperature operations on integrity of the soldered joints. It identifies the failure site and mode in the joints and examines failed surfaces to provide information on the morphology of the material microstructure. The results demonstrate that increase in CSH decreases the shear strength of the solder joints and at prolonged operations in high-temperature of about 150 degrees centigrade, solder joint shear strength decreases due to significant formation and growth of brittle intermetallic compound at the interface between substrate pad and solder bulk. EDS analysis shows that this region is characterized by high Tin/Cu content and demonstrates failure mode of crack initiation, propagation and pad lifting.