A Case Study of the Reliability of Copper Bond Wires In Plastic Encapsulated Integrated Circuits

Abstract

Sixteen plastic encapsulated integrated circuits were initially received as part of a root-cause failure investigation, twelve of which contained copper bond wires and the other four containing gold bond wires. It was reported that eight of the integrated circuits had failed in the field with intermittent or complete malfunction of the components. Electrical testing confirmed the reported failure and found temperature sensitive, intermittent open circuits on various pins coinciding with the sample history. C-Mode scanning acoustic microscopy (CSAM) was performed on the devices, with each sample exhibiting varying degrees of delamination between the lead-frame and the plastic encapsulant. The backside of the package was polished into the underside of the lead-frame to preclude the introduction of any contamination due to chemical decapsulation. This allowed the mechanical removal of the leads from the package and inspection of the stitch bonds. Scanning electron microscope (SEM) inspection revealed that the copper stitch bonds had corroded to some extent (ranging from mild corrosion to complete consumption of the stitch bond) in each of the examined bonds, whereas the gold stitch bonds were unaffected. Overall inspection of the leads identified chlorine contamination along the delaminated interface.