Oxygenous reflow affecting performance of Pb-free TFBGA assembly

Abstract

More high-pin count package and thinner thickness of ball-grid-array (BGA) substrate are appreciated in the recent commercial electronic products. Using thin profile fine-pitch BGA (TFBGA) substrate incorporated into the assembly line is a feasible solution. To expose the possibility with this substrate, two species of lead-free solder balls with and without nickel were applied and the oxygen concentration impacting the solder quality in reflow process was considered. The flux assistance for solderability was adopted to verify the integration capability in assembly mass production. The temperature effect attacking the solder adhesion due to the thermal stress and the difference of thermal expansion coefficients for entire package products was also taken into concern. Using the shear test and drop test could clarify the solder adherence between solder ball and TFBGA carrier substrate. Finally, the Cpk values for all of test groups were greater than 1.33, which demonstrated the TFBGA substrate was suitable to be employed in the high-pin count and high-profit electronic products.