Pan Pacific Symposium Conference Proceedings


ELECTROLESS NICKEL / ELECTROLESS PALLADIUM / IMMERSION GOLD PLATING PROCESS FOR GOLD- AND ALUMINUM-WIRE BONDING DESIGNED FOR HIGH-TEMP APPS

Authors: Kuldip Johal, Sven Lamprecht, and Hugh Roberts
Company: Atotech
Date Published: 2/10/2004   Conference: Pan Pacific Symposium


Abstract: This paper summarizes the results of qualification testing of the Electroless Nickel / Electroless Palladium / Immersion Gold (Ni/Pd/Au) process as it may be applied for use in high-temperature functional applications. The effects of exposure to heated, high humidity environments were also examined, in addition to the impact of extended thermal cycling.

The survivability of the Ni/Pd/Au deposit was studied for both gold wire (30-µm gauge) and aluminum wire (32-µm gauge) bonding under the following test parameters:

- Dry heat aging at 125°C and 150°C.
- Relative humidity up to 85% at 85°C.
- Exposure times up to 2000 hours.
- Thermo cycling (- 40°C / +125 °C) for 2000 cycles.

The reliability of the wire bonds was characterized by both wire-pull testing and visual inspection. With respect to gold wire bonds, it was found that regardless of environmental exposure the wire pull force remained unchanged during the testing period. Conversely, for aluminum wire bonds the pull force under dry-heat aging decreased initially and then stabilized.

During this qualification of the Ni/Pd/Au process, an examination of ball shear strength of BGA solder joints during thermal aging was also conducted. The results of these tests with eutectic Sn/Pb solder after thermo-cycling will be presented in a subsequent paper.

Key words: nickel/palladium/gold, ceramics, gold wire, aluminum wire, bonding.



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