Development of inclined conductive bump (ICB) for flip-chip interconnection

The Anisotropic Conductive Film (ACF) has been widely used for interconnection of the display and semiconductor because ACF has various advantages such as the low temperature bonding, low cost and small package size compared with wire bonding. However, as the pitch between the bumps decreases, the short-circuit of the bumps can occur by conductive particles of the ACF and the electrical conductivity depends on the number of particles trapped between the bump and pad. Attempts were made to overcome these shortcomings of the ACF by forming the conductive elastic bumps on the pads of the chip and utilizing the array of metal pillars fabricated on the polymer sheet. In this paper, the inclined conductive bump (ICB) is proposed, which provides the uniform electrical conductivity, elastic modulus and controlled bump deformation. The ICBs were fabricated on the test wafer and the inclined angles of the ICB were 70 and 80 degrees. Pitch of the ICB was 30μm ICB's were formed on each pad. The singulated chips are applied to assemble on organic substrates using a thermo-compression bonding method. ICBs showed good contact resistances of 12∼27mω.