Effects of ACFs Modulus and Adhesion Strength on the Bending Reliability of CIF (Chip-in-Flex) Packages at Humid Environment

In this paper, the effects of ACFs material properties on the dynamic bending reliability was investigated not only at room temperature but also at heated and humid conditions. There are two ACFs material properties improving the dynamic bending reliability of CIF packages. The first is the increase of resin modulus of ACFs, and the second is the increase of adhesion strength of ACFs. For experiments, 4 types of ACFs with different modulus and adhesion strengthes were prepared. Dynamic bending tests of ACFs-assembled CIF packages were performed up to 160,000 bending cycles with the bending radius of 6 mm at room temperature. In addition, the environmental reliability of ACFs-assembled CIF packages were also evaluated at the 85°C/85% RH thermal humidity storage test for 1,000 hours using a bending rod of 6 mm radius. As a result, it was found out that the most effective method to obtain higher bending reliability of CIF packages is increasing the modulus of ACFs not only at room temperature but also at thermal and humid conditions.