Thermosonic flip-chip assembly on flex substrates

Thermosonic (TS) flip-chip assembly on rigid substrates has been successfully demonstrated previously. In this paper we extend the TS bonding technique to the application of flip-chip assembly on flexible substrates. A custom TS bonder was constructed for this purpose that can heat the assembly rapidly without causing thermal damage to the flexible substrate. The reliability of the assemblies produced was investigated by the Temperature and Humidity reliability test. It was found that the interconnections of the TS flip-chip assemblies were more reliable than those of anisotropic adhesive assemblies prepared on the same bonder. The results indicate that TS bonding may have the potential to improve the reliability of chip-on-flex assemblies.