10 and 7 μm Pitch Thermo-compression Solder Joint, Using A Novel Solder Pillar And Metal Spacer Process

In this paper, spacer bumps concept is introduced to increase the process window for TCB, lower the sensitivity of electrical yield to bump height variation, maintain the gap between two dies and to prevent too much solder deformation for a test vehicle having multi-diameter bumps from 40um down to 5um pitches. Adding spacer bumps improves the electrical yield dramatically to close to 100% and ensures having good solder joint and IMC formation for both face to face N=2 and back to face N=4 stacks.