Reflow profile optimization of μBGA solder joints considering reflow temperature and time coupling

The purpose of this paper is to present a novel reflow profile optimization method using mechanical reliability estimation of micro‐ball grid array (μBGA) solder joints, based on the heating factor, Q_η is introduced, where the coupling effect of reflow temperature and time on the mechanical reliability of μBGA joints is considered.

The method presented is actualized through vibration fatigue tests. First, a two‐parameter Weibull distribution is used to model the collected data of vibration fatigue lifetime for different Q_η. After that, two explicit functions are deduced in a unified mathematic expression form, which give an intuitionistic description of the mean time to failure and reliability of solder joints against induced variable Q_η, thus revealing definitely the effect of Q_η on the mechanical fatigue lifetime of solder joints suffering from cyclic vibration loading. Finally, for a specified reliability goal, how to choose proper Q_η values, based an improved Golden Section Search arithmetic, is discussed.

Numerical analysis and calculation are performed. The results show that the solder joints made at Q_η near 510 have higher mechanical reliability, and those reflowed farther away this optimal value have less reliability.

This paper presents a useful and applicable solution to achieve reflow profile optimization and process control for a quantitative mechanical reliability estimation of μBGA solder joints.