Effect of electroless palladium immersion gold deposit properties on gold wire bonding

Microelectronic wire bonding is a widely used and cost effective manufacturing process used to electrically connect integrated circuits (IC) with printed circuit boards (PCBs) or other substrates. The first bond is formed on the chip side and the second bond at the circuit board side. The choice of wire bondable surface finishes used on the circuit board can have a great impact on the reliability of the device. Electroless nickel electroless palladium immersion gold (ENEPIG) is one of the available wirebondable finishes and has been applied in these applications for some time. Although the rate of adoption of ENEPIG has been limited, it is attracting more interest due to increased gold prices, as a replacement for electrolytic nickel gold. This paper will present experimental data that demonstrates the capability of ENEPIG as a versatile surface finish providing reliable gold wire bonding performance. It also confirms that ENEPIG is a viable alternative to electrolytic nickel/gold.