Flip chip assembly with wafer level NCF

Flip chip assembly with the newly developed pre applied NCF on wafer was demonstrated. The two types of the test vehicle of 7.3 × 7.3 mm² and 12.0 × 12.0 mm² were used and the NCF was pre laminated on the die side. The NCF applied dies were bonded to the substrate. The dies had Cu pillar bumps with Sn-Ag solder caps in both of the core and the peripheral area. The substrates had Cu/OSP electrode pad. The bonding was carried out at 240°C. The observations with C-SAM and microscopy which was done after parallel lapping didn´t show any void inside the NCF. The microscopic observation at the cross section of the joint of the die bump and the Cu trace on the substrate revealed the formation of good solder welding. The embedded daisy chain circuit resistance measurement indicated achievement of the bump interconnection of both test vehicles of 7.3 × 7.3 mm² and 12.0 × 12.0 mm² die. Test of the thermal cycle between -55°C and 125°C didn´t affect either the daisy chain circuit resistance or NCF adhesion.