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<p>Hi Russ,</p>
<p>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. </p>
<p>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.
(<a class="moz-txt-link-freetext" href="https://www.protoexpress.com/kb/enepig-surface-finish/">https://www.protoexpress.com/kb/enepig-surface-finish/</a>)</p>
<p>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.</p>
<p>Prashant</p>
<div class="moz-cite-prefix">On 7/1/2026 7:10 PM, Russ Renzas wrote:<br>
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cite="mid:DSVPR01MB9945226671EEC5DE55F7133651AAF52@DSVPR01MB994522.prod.exchangelabs.com">
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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.</div>
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Is it okay to put pcbs in our ebeam evaporator to evaporate Au? </div>
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We tried a small piece in a Au SEM prep sputter coater and that
worked but it's too small for the class PCBs.</div>
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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.</div>
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Russ Renzas</div>
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University of Nevada, Reno</div>
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<pre class="moz-signature" cols="72">--
Prashant Srinivasan,
Teaching Cleanroom Manager
Department of Electrical and Computer Engineering
University of California Santa Barbara
Santa Barbara, CA 93106
<a class="moz-txt-link-freetext" href="https://www.ece.ucsb.edu/department-resources/electronics-shop/tcr">https://www.ece.ucsb.edu/department-resources/electronics-shop/tcr</a></pre>
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