Letter 7027

Plating on Aluminum? 

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I am interested in wet (immersion) process that will allow deposition of thin (about one micron each) nickel and gold films on aluminum die individually. Zincating is the process that I have heard of, but how mature is this process? Is controlled cleaning/etching of aluminum a problem even if the aluminum is of high purity (sputtered)

This process if matured enough can be used at flip chip attachment.

Thanks

adarsh kumar
Microelectronics Research Lab - Columbia, Maryland, USA

Zincating is a very mature process, for large parts. Thousands of miles of aluminum bus bar has been zincated then copper plated. Hundreds of thousands (maybe millions) of aluminum automobile and truck bumpers have been zincated then copper-nickel-chrome plated. Tens of millions of die castings and electronic parts have been zincated then plated.

Whether the process is suitable for your needs, though, I wouldn't know. You might want to search for some of the papers on zincating by David Lashmore, such as:

• "Immersion Deposit Pretreatments for Electroplating on Aluminium - Literature Review", Plating & Surface Finishing, Apr. 78.
• "Progress in Plating onto Aluminium", Plating & Surface Finishing, Jan 80.
• " Plating on Aluminium - A Review", Plating & Surface Finishing, June 85.

because his studies tended to look at the zincate film from a material science point of view whereas many of the other papers talk about more practical production-oriented issues in zincating.

 
Ted Mooney, P.E. - finishing.com Inc. - Brick, NJ

The use of zincate is well established as an adhesion layer for Al. Developed a process for plating Ni and Au on very thin films of Al on power devicesusing zincate as an activation layer. It was a technology used to fabricate flip chips

RP Daniel
Microplex - Placentia, CA

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