What material (double sided sticky) can we use to micro gap an SMPS Forward transformer?

[treez]

What material (double sided sticky) can we use to micro gap an SMPS Forward transformer?

The following threads show that generally speaking , its advantageous to have a tiny gap in a Forward converter core. (Standard ferrite lapping process means that you have a gap in “Ungapped” cores anyway, if only at microscopic level)……

https://www.edaboard.com/threads/push-pull-start-up-issue.348624/#post-1489330

https://www.edaboard.com/threads/tw...verter-with-bootstrap-high-side-drive.340530/

https://www.edaboard.com/threads/gapping-a-ferrite-core-for-full-bridge-smps-transformer.341980/

We were going to use a bit of kapton as a shim between all joining faces (centre and outer legs) but its awkward to cut up and not double sided sticky.

Is there an ultra-thin double sided sticky tape that can fill this purpose?

 

[wwfeldman]

if i recall, kapton also stretches relatively easily so the gap length will change after a while
as the core pieces on either side of the kapton are attracted to one-another

why double sided sticky? wouldn't single sided sticky be sufficient?
varnishing or impregnating the magnetics should be enough to hold the gaping material in place

 

[treez]

Thanks, thats a good point, we need the gapper to be not too compressible, but a bit is ok, as its only a forward converter, and as long as theres some kind of gap then its fine..

I suppose yes it doesnt have to be double sided sticky

 

[dick_freebird]

How about you smear a little bit of JB Weld
(or other temperature capable epoxy) on
both sides of the Kapton film?

 

[Easy peasy]

Kapton film is fine as long as its not pre-stretched, there are differing thicknesses available too ... the amount of force needed to compress Kapton is far greater than you will see from cores ( peak B ) or clips

 

[FvM]

You can buy double-sided tapes, e.g.
**broken link removed**

Double Sided Polyimide Tapes

Consider that the adhesive layer involves a possible thickness variation