Abstract
Chip-on-flex (COF) with anisotropic conductive film (ACF) assemblies is widely used in recent years because of their smaller packaged volume and flexibility. In this study, four-point bending test method was chosen to observe the flexible performance of the specimens. The experiments were divided into two parts. In the first part, the accelerated environmental tests including high humidity (85 %RH) at high temperature (85 oC), high temperature aging（150 oC）, and thermal cycling test (-40 oC~125 oC). After different storage time of accelerated environmental tests, the COF assemblies were took out and tested at room temperature. Bending fatigue behavior of the COF assemblies was investigated as the second part. The displacement controlled bending fatigue tests were performed at 80 oC/85 %RH and 60 oC/85 %RH conditions with different frequencies. The results show that the daisy-chain resistance of COF specimens were almost invariant during accelerated environmental tests. The flexibility of the COF assemblies decreased progressively with increasing aging time of the humidity test and the fracture mode was originally cohesive fracture and translated into interface fracture between ACF layer and substrate after the effect of humidity. However, the flexibility increased slightly with high temperature aging and thermal cycling. The transition phenomenon of the fracture mode didn’t appear during the high temperature aging and thermal cycling tests. In the bending fatigue experiments, with increasing the temperature of testing environment, fatigue life at low frequency test decay more apparently than that at high one. Finally, it is obtained that the ACF layer destroyed notably at high frequency than low frequency at high temperature and humidity environment.