Thermosonic-Adhesive flip-chip assembly

Thermosonic (TS) and Non Conductive Film (NCF) flipchip assembly are well known packaging techniques for fine-pitch electronics manufacturing. In this work a novel process combining TS bonding with NCF packaging was developed, termed Thermosonic-Adhesive (TA) flip-chip assembly. The aim was to introduce a TS bonding step into the NCF assembly process in order to replace the mechanical contacts by direct metal-metal TS bonds. A custom TA bonder was constructed for this purpose that can heat the assembly rapidly to the temperature required for TS bonding without causing thermal damage to organic substrates. Assemblies were produced on flexible polyimide substrates and subjected to Temperature and Humidity reliability testing. It was found that the interconnections of the TA flip-chip assemblies were more reliable than those of anisotropic adhesive and TS assemblies prepared using the same bonder. The results indicate that this novel bonding technique may have the potential to improve the reliability of chip-on-flex assemblies.