Micro-joint reliability of flip chip assembly under thermal shock-strain and stress

The stress and strain of soldered joints under thermal shock were studied, and the crack growth in soldered joint were also analyzed. The results show that the corner soldered joint has the most accumulated plastic strain and plastic work density, which is the critical soldered joint in the assembly.The accumulated plastic work density is mainly located in chip sidenear Ni pad. The largest value is in the outside, and decreases along the Ni pad to inside, which indicate the crack formed on the chip side, and then grew along Ni pad from outside to inside, at last crossed through the whole soldered joint. The experimental result matched the simulation analysis well, and further proved the analysis of crack growth in soldered joint.