Fantastic, never knew stuff like this existed.   We have old potted comparators 60's vintage that we need to reverse engineer,  someone was going to have to spend hours grubbing out the case to see what exactly was inside.   Looks like it might be an easier solution.    

Pat Goodyear
Control Tech PG&E

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Steven Creswick
Sent: Thursday, October 11, 2012 2:38 AM
To: [log in to unmask]
Subject: Re: [TN] Glob Top removal

Mark,

I used to use a material called Decap from Dynaloy - based out of Indianapolis, IN.  Here is their web site.
http://www.dynaloy.com/dynaloy-chemical-solutions-products/specialty-chemist
ries/epoxy-products.html

The Decap will work for many glob tops, but you must keep an eye on temperature.  Some are removed better with warm temps, others with hot temps.  You really have to test for yourself unless you know the composition of the glob top material.  DO NOT use without a vented hood.  The stuff reeks something terrible.  Make you wish you lived next to a pig barn!

What I would do is suspend the part in the solution and periodically shake it around a bit to dislodge the silica particles from the 'glob', thereby exposing new epoxy to the chemical.  It is not perfect, but is far less hazardous than fuming nitric!


They also have materials for Urethane CC removal, but not necessarily localized removal...

Steve Creswick
Sr Associate - Balanced Enterprise Solutions http://www.linkedin.com/in/stevencreswick
                         616 834 1883



-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Woolley, Mark D. (Mark)
Sent: Wednesday, October 10, 2012 11:59 PM
To: [log in to unmask]
Subject: [TN] Glob Top removal

Does anyone know of a way to remove the epoxy that is used to cover CoB ICs, while maintaining the integrity of the PWB-CoB Assembly afterwards?
I have tried hot Nitric Acid, which does remove the epoxy nicely, but also removed the copper on the PWB and swelled during the decap process and ruptured the bondwires.  I believe Red Fuming Nitric would also swell the epoxy lifting the bondwires.  Most aggressive solvents don't remove epoxies well. So I am pout of ideas at present.

Thanks,
mark

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