Reliability of copper wire bonds on a novel over-pad metallization

Abstract

Wire bonding technology is used in most semiconductor products. Recently, high gold prices have forced semiconductor manufacturers to replace Au wires with Cu wires. Because Cu wire bonds are vulnerable to high temperature and humidity, they remain unpopular in automotive and industrial applications with narrow-bond-pad pitches and small deformed ball diameters. To avoid forming the corrosive Cu-rich intermetallic compound Cu 9 Al 4 , the use of a Ni/Pd(/Au) over-pad metallization (OPM) structure produced by electroless plating on the Al metallization has been proposed. However, certain technical issues must be overcome, such as variations in the purity and thickness of the plating. To tackle these issues, a novel OPM structure produced by physical vapor deposition is proposed and evaluated in this study.

Investigation of connecting techniques for high temperature application on power modules

“…between the substrates and between the substrate and the main terminal. Conventionally pure Al wire have been used to connect these areas, however when the substrate surface is Cu, Cu-Al IMCs (intermetallic compounds) like Cu 9 Al 4 and CuAl form after package assembly [9] . During high temperature operation, they grow rapidly and become easy to break the electrical contact.…”