Cu-based leadframe is the most useful material in IC packaging for high thermal conductivity and low cost. To make a electrical connection to Si chip, Au wire is used. But,in this wire bonding process, the Cu L/F has to be exposed to 200∼240℃ temperature. The formed Cu oxide layer plays a bad role in the adhesion between L/F and EMC. So, to control the thickness of Cu oxide is a very critical point in packaging process.
In this study, the Cu oxide layer is formed, being exposed to 160∼300℃ heater block temperature. To measure the thickness of Cu oxide, Galvanostatic Reduction method is used. The formed oxide layer is proved to $Cu/Cu_2O/CuO$ by XRD(X-Ray Diffraction). And, to check the adhesion, there was a molding and Pull-out test. The pull strength decreases rapidly above 50nm oxide thickness. This thickness corresponds to 200℃, 2∼4min oxidation. Failure analysis is performed with this pull-out test specimen. The used instruments are SEM(Scanning Electron Microscopy), EDS(Energy- Dispersive X-Ray Spectroscopy), AES(Auger Electron Spectroscopy), XPS(X-ray Photoelectron Spectroscopy). The failure locus was proved to mainly Cu/Cu Oxide layer, partly internal oxide layer or oxide/EMC interface.
