Studies of the interface between the epoxy molding compound and the copper leadframe by x-ray photoelectron spectroscopy, Auger electron spectroscopy, and secondary electron microscopy

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Abstract
The interface between the epoxy molding compound and the copper leadframe of an integrated circuit device has been studied by x-ray photoemission spectroscopy (XPS), Auger electron spectroscopy (AES), and secondary electron microscopy (SEM). The surface of the copper frame is composed of CuO, Cu2 O, or Cu(OH)2 depending on the heat treatment for the frame before the molding process. The XPS results show that cuprous oxide is the primary copper oxide at the interface between the leadframe and the epoxy polymeric encapsulant after the molding process. Copper was found to migrate into the epoxy resin side. According to AES and SEM, silica fillers in the molding compound abrade the copper oxide layer on the copper frame during the molding process, and the injected hot epoxy fluid can interact directly with the freshly exposed metallic copper surface. The accelerator of the molding compound segregates to the abraded area at the interface. The rugged interfacial structure close to the molding compound injection gate is probably the primary factor causing the microgap problem at the interface.

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