Microwave Induced Plasma decapsulation of thermally stressed multi-tier copper wire bonded IC packages

Thermally stressed high-density multi-tier copper wire bonded IC packages are the most challenging tasks in IC package decapsulation. For acid decapsulation, the hardening of epoxy in molding compound after stress tests requires much longer etching duration. As a result, copper bond wires suffer severe corrosion damage compared to un-stressed package counterparts. For plasma decapsulation, the high-density bond wires block the radicals in the plasma to reach the molding compound beneath the wire loops. As a consequence, molding compound residues around the Cu/Al ball bonds become impossible to remove. This work investigates the difficulties when exposing Cu/Al ball bonds in high-density copper wire packages after thermal stress testing, and proposes an improved Microwave Induced Plasma decapsulation process that enables clean exposure of Cu/Al ball bonds while preserving the bond wire surface features.