Plating for aluminum wire bonding

Hi

It sounds like you are in a different country or in the USA a long time ago.

I have no idea of the process either is using, so they can be comparable or one can be better than another and lop sided compared to other places.

Benchmarking I think is the wrong term since you are only using two suppliers. Benchmarking applies to the entire industry.

Ask each of them to slightly vary the process or give you parts from the low and high side of their outputs. Compare results in your shop. Now this isn't really statistical yet it give you a sense of each supplier's process as run through your shop.

YiEng MA/NY DDave

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Electroplated nickel and electroplated gold is the more �traditional� finish for aluminum wire bonding. That surface was an extension of gold thermosonic wire bonding that requires a thick [50 thou min] gold surface. For years fabricators recommended a thinner [~25 thou] gold for aluminum wire bonding.

Separately, with the drive for flatter solderable surfaces, ENIG became a desirable surface for fabricators, because they could command high mark-ups from their customers that were used to HASL pricing. Assemblers found ENIG acceptable for aluminum wire bonding, which is good because to increase the maximum imm gold plating thickness [<12 thou] to the traditional thickness requires an additional electroplating fabrication step.

So, your suppliers are correct. Either surface works.

We don�t think either surface is superior. * Electrolytic [electroplated] nickel plating is a less demanding process that electroless nickel * Electrolytic require bussing and electroless doesn�t, but if you�re running electroplated gold the boards require bussing and maybe accomplished using the same racking, just prior to gold plating. * Electroless nickel has traditionally been used where no bussing is available. * Lack of ENIG process control can result in black pad [search fine SMTnet Archives for background] that affects wire bonders as well as solderers.

So, price differences may have more to do with individual fabricators set-up and process preferences than underlying materials or structural costs.

Purity of plated material is very important for any type of wire bonding process. * For aluminum wedge bonding the nickel becomes critical. Always have a minimum of 50 thou nickel. You want the nickel plated as soft as possible, no contaminates or voids. It requires good control of pH and plating chemicals in the plating bath. * For aluminum wedge wire bonding, you want the gold thickness to be a minimum of 3 thou and a purity of 99.99% (no thalium).

What problems are you seeing with your ENIG boards? * Wire bonds don't stick when bonded * Wire bonds fall off, or break during service

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