Ship right away?  That's scary!

You need to list the characteristics required other than it needs to be very fast cure.  The 5 minute epoxy is horrendous stuff--breaks down readily with heat, bad ionics, smells bad, not very strong, ...but it does cure quick!

Sounds like you just need to get strength back without harming the circuit board.  And the stuff needs to be able to take high temperature--but probably below soldering temperature, and it needs a reasonable breakdown voltage.

The Circuit Technology products are a pretty good way to go--much stronger than 5 minute, and much lower in ionics.

A COB material such as Hysol FP4470 would probably do an awesome job if you can get your hands on some.  It would withstand reflow.  It needs to be cured under a vented hood because some of the vapors coming off aren't good for you.  It is very runny, so it fills cavities well.  Adhesion to FR4 is great.  There's a "Dam" version of this product line as well if you need higher viscosity.  But you may have a delay in getting the material, minimum quantities can be expensive, and the cure cycle is several hours.

Of course, JB Weld is pretty awesome too, but it isn't rated for electronics and it has iron particles in it which might degrade the voltage withstanding capability.  But I'd still take that over 5minute epoxy!

Wayne Thayer

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Nutting, Phil
Sent: Friday, June 21, 2013 9:21 AM
To: [log in to unmask]
Subject: [TN] circuit board repair materials

Good morning all,

This is a question regarding the repair of FR-4 after there has been a high voltage arc/burn.  In a recent failure we ground out all the burned material and "repaired" the board with 5 minute epoxy.  This is on a pancake connector for a 160kV x-ray tube.  I am of the opinion that 5 minute epoxy will soon fail as it does not have the same insulating characteristics as the base FR-4.

I see that Circuit Technology carries all sorts of repair materials/kits.  So, if you were to salvage a burnt circuit board that had to ship right away, what materials would you use?

Off line replies are accepted if you want to protect your sources or don't want to "advertise" on Technet.

Thanks in advance for your wealth of information,

Phil Nutting  |  HVP Development Engineer   |  Excelitas Technologies Corp

Office: +1 978.224.4152
35 Congress St, Salem, MA  01970 USA
[log in to unmask]<mailto:[log in to unmask]>
www.excelitas.com<http://www.excelitas.com/>


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