Decapsulation of high pin count IC packages with palladium coated copper wire bonds using an atmospheric pressure plasma

The applicability of microwave induced plasma based decapsulation technique to high pin count palladium coated copper wire bonded IC packages is studied. One of the major limiting factors that causes low molding compound etching rate by plasma is the SiO₂ agglomerate formation during etching. A new process combining Ar/O₂ plasma etching with ultrasonic cleaning is developed to safely and efficiently remove the molding compound without causing damage to the die and the copper wire bonds. General plasma etching recipe that can be easily applied to different types of packages is developed. Comparison between plasma and cold acid decapsulation based on the same BGA package with 20 um palladium coated copper bond wires is made. Plasma removal of the Si₃N₄ passivation layer is achieved with endpoint detection by real-time imaging of the plasma etching process. It appears that the combination of laser ablation with plasma etching gives a superior performance over laser ablation with cold acid etching.