Bump height effect on the reliability and on the strains variations of ACA flip-chip joints

Flip-chip joining using anisotropically conductive adhesive (ACA) has become a very attractive technique for electronics packaging. Many factors can influence the reliability of the ACA flip-chip joint. Bump height, is one of these factors. In this work, the strain development during the thermal cycling test of flip-chip joining with different bump heights was studied. The reliability of flip-chip joining with different bump heights was studied using a temperature cycling test. In the temperature cycling test, the assemblies on FR4 substrate show that reliability decreases with increasing bump height. On the other hand, on the flexible substrate, the electrical performance of the ACA flip-chip does not change with bump height. The effect of bump height is significant in the interface between the bumps and the pads. Bigger volume area of high strain is found for higher bump in the interface between the bumps and the pads. Our calculations show that there is practically no effect of the bump height on the strain variation in the bumps and in the pads