Effect of Material Properties of Double-Layer Non Conductive Films (D-NCFs) on the Reflow Reliability of Ultra Fine-Pitch Cu-Pillar/Sn-Ag Micro Bump Interconnection

In order to interconnect ultrafine pitch Cu-pillar/Sn-Ag micro bump, Non Conductive Films (NCFs) have been used. During thermo-compression bonding processes, applied pressure and heat make molten solder deform and wet on the sidewall of Cu-pillar. As a result, large Sn-Ag/Cu-pillar sidewall interface reaction makes Sn consumption faster and the Kirkendall void formation. In this study, novel double-layer NCFs(D-NCFs) have been introduced and successfully solve the solder sidewall wetting problem of Cu-pillar. As a result, D-NCFs with proper curing behavior of NCFs material properties prevent Sn wetting on the Cu sidewall and increased the remaining Sn content at the solder joint. Therefore, NCFs with better mechanical properties produced good joint interconnection properties after solder reflow test resulting in better reliability electrical performance.