Crack growth analysis of ball grid array resistor's solder joint subjected to thermal cycling and 4 point cycling bending

The crack growth rate of two different constructed BGA resistor’s solder joint subjected thermal cycling was calculated using a dye penetration method. “ The crack percentage ” and the number of thermal cycling were recorded until the end of the test that “ the crack percentage” greater than 50%. 4-point cycling bending test was also performed to observe failure mode compared with thermal cycling. The experiment indicated that 1) The dyeing appearance of solder was central symmetry and 2)”The crack percentage” and the number of thermal cycling has the exponent relationship and 3)The crack happened on both PCB side and component side, the crack growth direction at component side is from outside to the component central and 4)the contrary crack growth direction was observed in the 4-point bending fatigue test and 5) the failure mode was proved by FEM.