epoxy instead of solder?

Has anyone tried Masterbonds conductive epoxy for attaching SMT components to a printed circuit board?

Seems like a great idea, especially if it works well:>:

Not really. Consider the angle of serviceability. It's easy enough to use a 'HoTweezer' station to replace a bad chip component secured with solder. It's darn near impossible to replace the same component if secured with Epoxy.

Also, I'm not convinced that "conductive" Epoxy really is. I'd want to see some real numbers on resistance per cm/squared on the stuff before I even consider it for any sort of repair work.

Any job worth doing is worth doing right. If you're trying to attach surface-mount components, invest in the proper soldering/desoldering equipment instead of looking for impractical shortcuts. It may cost more at the get-go, but it'll cost a lot less in the long run.

Keep the peace(es).

Hello John,

Then there is the stench that most epoxies let off. Mostly of the not so healthy kind.

Regards, Joerg

Sounds like a terrible idea. The surface tension of solder and the solder mask/PCB landing on the circuit board interact very nicely to make sure that a blob of solder and the part itself stays on exactly the right spot when you solder on a SMT component (either hand soldering or toaster-oven style). None of that is working to your advantage when you use epoxy.

Hand-soldering even fine-pitch (0.5mm) SMT stuff is not a big deal to do by hand with even primitive (e.g. just a weller soldering iron and a fine-tip point and some solder wick) tools. BGA's will require a toaster oven though :-).

Tim.

No, conductive epoxy is used in many microwave circuits, because heat would ruin the characteristics of the very thin microstrip substrate. Other than for that, I would not use it.

I do not know about Masterbonds conductive epoxy(ies), but i have used silver conductive epoxy. 1) EXPENSIVE, 2) good for short-term and medium-term repair, but no where as reliable as a solder connection.

The silver conductive epoxy is extremely conductive, and even tho i never measuresd the resistivity, i would wager that it is better than copper if used properly.

First time i heard that Kapton or Teflon was heat sensitive...

It is done in special circumstances, but not that often. SMT passives are available with different termination platings/coatings for such an application, but they are harder to come by. It won't work as well if you use devices with terminations intended for soldering.

Here are some examples of silver epoxies:

Copper:

According to these sources, copper is about 100 to 10,000 times as conductive as silver filled epoxy.

Just another point of reference. From:

Sounds VERY interesting! I have some clients that need to mount components that can't stand the heat of soldering. The only problem might be "tenacity"... how much "shake, rattle and roll" can it take?

...Jim Thompson

The 3M conductive adhesives like the 9703 work well. Not sure how they do it but it conducts in the Z axis ( thru the adhesive ) but not accross the surface direction ( X & Y axis ). It's a pressure sensitive transfer adhesive ( tape that you stick on then peel off the paper carrier leaving the adhesive behind)

X-Y axis Insulation Resistance = 3.4 x 10 to the 14th Ohms/square Z axis Contact Resistance = 1.25 milliOhm-in2

Pretty neat stuff!

Ron H.

x-- 100 Proof News -

I have a roll of that. Very pricey. It contains lots of short bits of very fine copper wire precisely aligned through the thickness of the adhesive gel. The wires do not contact each other, so there is no conductive path along the gel.

Definitely. Sort of the dual of enameled wire. Conducts only at right angles to the length.

Its glorifies scotch tape:

Just go to 3m.com and search for "conductive adhesive" or "9703"

it

x-- 100 Proof News -

I read in sci.electronics.design that snipped-for-privacy@rica.net wrote (in ) about 'epoxy instead of solder?', on Thu, 6 Oct 2005:

resistivity, not conductivity.

Thank you.

Conductive adhesives have been discussed in Advanced Packaging magazine (IIRC, might have been another trade mag) and the main problems preventing widespread replacement of solder are not adhesion but high initial resistance (not suitable for the current required by large processors etc), and worse, gradual increase in resistance over time especially at higher temperatures and humidities due to slow oxidation of the conductors as water vapor and oxygen diffuse through the adhesive polymers. Not ready for prime time now, and might not be for a long time due to the lack of candidate impermeable adhesive polymers. Suitable now for low power apps in benign envireonments where long life is not important.