>Phil,
>     For aluminium wedge bonders try K&S, Palomar, or Delvotek. Wedge bonding to
>nickel, immersion gold is a reasonable process. I have not tried it over three
>layers of photo imagable dielectric though, but can see no fundermental reason
>why it shouldn't work. Bonding takes place at room temperature, so the Tg of the
>material isn't so important for bonding. 

Have you tried gold ball bonding to copper/nickel/flash gold?  One vendor is telling me that gold ball bonding to copper/flash silver (4u") works just fine.  I'm skeptical.  I only know what I run across in traderags etc... but it seems to me that the consensus is that while gold ball to immersion flash gold is possible, it is somehow unreliable or inconsistent for MCM purposes (my MCM has 700 wires in a 1.5x1.5" area to all kinds of different devices).  If it isn't reliable for gold, I can't see how flash silver would be any better!?  Shoot, I have enough problems consistently bonding to thickfilm gold!

A three layer built up board is going
>to limit your choice of suppliers at the moment, but you may be able to find one
>who can give you a gold bondable surface. 

MicroVia in Florida can do 3 microvia layers, but they can't put on soft gold right now, only thin immersion flash. 

Jeremy, thanks for the bonder edu!

Resp.
Phil Hersey, Hytek