[labnetwork] PCB in e-beam evaporator?

[Prashant Srinivasan]

Hi Russ,

I don't think this is a good idea. FR4 outgasses and this alone can be a 
problem. The base material, FR4 is some kind of an epoxy resin, which 
you definitely do not want to contaminate your chamber and the QCM with. 
Heating wise you should be okay as the PCB will probably sit about 1m 
away from the source.

Have you tried electroplating Au? If you are getting a PCB made, many 
PCB houses provide an Au-Pd-Ni stackup that lends itself to a reliable 
wirebond. (https://www.protoexpress.com/kb/enepig-surface-finish/)

As for Al -Au, I don't think that works well. The hard Al2O3 layer must 
be removed and even worse Al alloys with Au (purple plague) by forming 
an intermetallic which is brittle with high resistivity. Just not good.

Prashant

On 7/1/2026 7:10 PM, Russ Renzas wrote:
> For a summer lab class we're trying to have students make a chip and 
> wirebond it to a PCB. We're having trouble wirebonding to the 
> immersion gold pads though.
>
> Is it okay to put pcbs in our ebeam evaporator to evaporate Au?
>
> We tried a small piece in a Au SEM prep sputter coater and that worked 
> but it's too small for the class PCBs.
>
> Thanks, also appreciate any tips on how to spec pcb metalization for 
> wirebonding compatibility. We have both Al ultrasonic wedge and Au 
> ball bond capabilities.
>
> Russ Renzas
> University of Nevada, Reno
>
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-- 
Prashant Srinivasan,
Teaching Cleanroom Manager
Department of Electrical and Computer Engineering
University of California Santa Barbara
Santa Barbara, CA 93106
https://www.ece.ucsb.edu/department-resources/electronics-shop/tcr
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