Reliability assessment of flip chip interconnect electronic packaging under thermal shocks

In the paper, 3968 solder bumps and underfills were prepared on ceramic substrates with flip chip method. After thermal shocks the solder joints of serial number before 24 were left wrapped and the solder joints of serial number after 39 were right wrapped. The average spreading area and diameter of solder joints were 4681 μm
²
and 119 μm, respectively. The solder joints with small serial number were left offset and the maximum offset of left was 28 μm. Inversely, the solder joints with big serial number were right offset and the maximum offset of right was 31μm. The deviation of solder joints on both sides were the most evident. This might be owing to CTE mis-matching between silicon chip and ceramic substrate. Besides, the IMC layer of both sides was mainly Cu
₆
Sn
₅
. The IMC layer on top of Cu pillar was Ni and Ni
₆
Sn
₅
.