A problem with rapid cure epoxies is that you never have time to get a 
homogeneous mixture; you will therefore have spots with an excess of one 
component and others with a lack of it, even in the unlikely event of 
your getting the proportions right. The right word to look up is 
stoichiometry. In addition rapid epoxies are very exothermic and 
temperature differentials can create stress and even cracking. A good 
electrical grade (reduced ionics) with a cure time of several hours 
would seem appropriate for such a hi-V job

Brian

On 21.06.2013 16:20, Nutting, Phil wrote:
> 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
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