Cyclic Bending Testing condition effect on the SnAgCu Solder Interconnects in TFBGA Package on Board

With the more reliability requirement increasing in the IC packaging for mobile product, the testing condition to simulate the service life of IC packaging on board will be emphasized, such as mechanical drop, temperature cycling, bending, vibration and so on. 4 point cyclic bending condition including different bending frequency and displacement to simulate actual service condition is defined in JEDEC22-B113. The best testing condition (1 Hz/2 mm) is recommended to accommodate better for service condition, but the correlation among each testing condition showing different strain rate will present different ductile and brittle behavior due to unique SnAnCu interconnect characteristics upon actual IC package. In the study, it will be investigated the effect of board level cyclic bending condition on the solder joint durability of 0.5 mm pitch lead free TFBGA packaging. The various testing condition described in the JEDEC spec is conducted to explore the ductile/brittle transition behavior of the TFBGA package. Furthermore, the surface finish on the PCB effect between OSP and Ag immersion and solder ball composition effect under optimized bending condition will be concluded with the metallurgical analysis of X-section, SEM and FIB. Finally, the IC packaging behavior on board by way of various cyclic bending conditions can be referred to simulate lower strain rate and higher strain rate deformation in temperature cycling and mechanical drop test for the TFBGA package design optimization.