es of Fan-idFan-out Structure and Unde~~ll Fillet on TCT Reliability of Flip Chip

The reliability of two types of flip chip BGA was investigated using temperature cycling test (TCT). It showed that the reliability of the Fan-out structure was higher than that of the Fan-in structure. The Fan-in structure broke easier at the die edge than the Fan-out structure. The highest region of thermal stress on the Fan-out structure package was different from that of the Fan-in structure package. Therefore, the crack modes were also different. FEM analysis makes clear the difference of the maximum principal stress on the backside. The higher stress region of each structure influences their TCT reliability. The use of a ceramic substrate, as opposed to BT resin, improved the life time of the Fanin structure for the thermal stress.