Microstructural evaluation and failure analysis of Ag wire bonded to Al pads

Abstract

We found the failure mechanisms in Ag wire bonded to Al pads during the high-temperature-storage lifetime test (HTST) and the unbiased highly-accelerated temperature and humidity storage test (uHAST). The native oxide layer on the Al pads caused a ball lift The moisture and the thermal energy during uHAST along with the Cl- ion in epoxy molding compounds (EMCs) induced repetitive oxidation and reduction reactions of the Ag-Al intermetallic compounds (IMCs) with the Al pads. These repetitive reactions formed H-2 gas as a by-product causing the formation of a micro-crack. In addition, the alumina layer acted as a resistive layer in the Ag-Al IMCs. The phases of the Ag-Al IMCs were identified as Ag2Al and Ag3Al, and the growth rates of those IMCs were measured at 150 and 175 degrees C for 2000 h. (C) 2015 Elsevier Ltd. All rights reserved.