[labnetwork] PCB in e-beam evaporator?

[Michael Khbeis]

Russ,

In principle you can do this but the organic substrate (assuming FR4) will
take forever to pump down due to water absorption. Highly recommend you
bake out the board at 100-120C for 1-2 hrs in a vac oven prior to loading
in the evap.

The bigger question is why is your immersion gold not working for wire
bonding? Is it the right thickness? Right metal stack? I assume you have
electroless nickel immersion gold as a typical barrier/“bondable gold”
stack on top of Cu. Bondable gold is thicker, usually with a 300nm minimum
thickness for robust wire bonding. If you are using a standard
autocatalytic immersion gold bath it will self-limit the plating at 100nm.
This is standard thickness for soldering applications where excess gold
thickness is problematic due to AuSn intermetallics. There are some
immersion gold chemistries that do not self limit which would allow you to
target the 300nm with a longer deposition time. Also, if you are ordering
the PCB from an external source - just make sure to spec “bondable gold”
finish and not standard ENIG. Also, ENEPIG (E-less Nickel, E-less
Palladium, Immersion Gold) is a universal finish - you can use it both for
wire bond and soldering applications.

Hope that helps!

Best,

Dr. Michael T. Khbeis
Design / Process Engineer/Cleanroom DirOps
mtkhbeis at gmail.com

On Thu, Jul 2, 2026 at 5:06 AM Russ Renzas <rrenzas at unr.edu> 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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