The reliability study of a high density multi chip packaging with folding flexible substrate

This paper presents a multichip stack packaging based on flexible substrate. In this structure, three dummy chips with daisy chain test circuit were flip-chip bonded on a double-layer non-gel flexible substrate, then a 3D packaging were made by folding process. The dimension of the 3D package after folding was about 6×6.6×1.3mm³. The dimension was mainly confined by the dimension of dummy chips. To test the structure and process, some electrical measurements was taken. And the main reliability problem of a flexible package was investigated through a series of reliability tests.