A dynamic bending method in CSP package validation for portable electronics application

In the study, instead of electrical resistance monitoring in JEDEC JESD22-B111 for mechanical shock testing of handheld electronics, a proprietary strain-controllable dynamic bending method is applied to verify the effects of lead free SnAgCu solder ball with different dopant on the board level reliability of green TFBGA package. The result shows the strain-controllable dynamic bending method can identify the weakness of IC package on board by way of the setting of the low strain to high strain gradually. Various failure modes from interfacial IMC crack in component and PCB side, pad crater due to core material adhesion issue of HF PCB and solder bulk itself are scrutinized by advanced FA application of SEM/EDX, polarized OM, respectively. The SnAgCu solder with 4^th element dopant to compare with SAC105 will demonstrate certain improvement in solder joint reliability. On the contrary, the HF PCB will downgrade certain percent solder joint reliability due to its higher stiffness, as well the larger package size and thermal aging precondition present similar behavior.