Thermo-mechanical finite-element modeling of a chip-on-foil bonding process

A chip-on-foil (COF) inner-lead bonding (ILB) process for diplay driver ICs is studied by means of thermo-mechanical finite-element modeling (FEM). The residual stress distribution in the assembly after bonding is calculated for different bump arrangements and process parameters. The simulated foil induced shear force on the corner bumps could be correlated to experimentally observed corner bump failures. A redesign of the bumps decreased the failure rate after bonding from typically 1% to typically 0.01%.