EPC Fets and Bondit

Sorry, Bondic not Bondit.

The stuff at the bottom of the vias is hard.

Does it release easily with alcohol like hot glue does?

...

Dentists use a lot of UV-cure materials. For cosmetic work, they get applied in multiple thin layers, cured one at a time. I believe this is so folk don't end up with uncured resins in their mouth - so it's is quite likely a problem.

On the other hand, anywhere you can't get UV is somewhere you can't see, so if there's uncured resin there, you'd only know by cutting into it.

Improperly mixed (or wrong ratio!) epoxies form a microscopic mesh containing uncured resin components. If the ratios are close, the result is almost as strong as properly cured epoxy, but professionals still take extreme care with proper weighing and mixing of parts.

I learned this from a neighbour who spent his whole career in this industry. His techniques are being used in Melbourne to make airfoils for Boeing jets, and his technique&design for making refrigerated shipping containers is the industry standard. Vale Bill Maloney. He was a lovely chap.

CH

Not very fast, if ever. In optical assembly it's common to tack parts together by partly curing a few areas, so that if there's some screwup you can get them apart again.

IIRC it depends on the catalysis mechanism. If the catalyst is a small molecule, it eventually diffuses around pretty well. OTOH it isn't at all difficult to get mixing on molecular scales. The exponential effect of folding does a very good job even for epoxy putty.

Cheers

Phil Hobbs

While that may be true of UV cure acrylic adhesives, there are UV cure adhesives designed to cure in unexposed areas such as under components, for example:

Unlike the Bondic site

- they claim it is proprietary!

There are other mfgrs of UV cure adhesives designed for electronic component encapsulation which provide good specs too, some of which seem to be readily available in small quantities from the usual suspects

BTW I have found that half a bottle of UV cure optical adhesive will cure in the bottle if left in a dark refrigerator for a decade :-).

Most Epoxy manufactures claim that under mixing is the most common cause of failure to achieve rated properties, and many recommend mixing until the mix visually appears to be complete, then continue mixing in the same manner for the same time again, mixing twice as long as appears necessary. The catalyst is rarely a small molecule in epoxy, it won't diffuse far and is not purely a catalyst responsible for initiating polymerization but also an essential part of the cured co-polymer resin.

Interestingly many of the UV cure adhesives tailored specifically to glob- top encapsulation and BGA underfill (UV + anreobic cure) are one part epoxies, not acrylics.

Yeah, I'm mostly familiar with Norland 65 and 85, which I standardized on long ago.

Cheers

Phil Hobbs