Who is a glue expert

T Chap

Currently I run a giant bead of heat glue around the inside of this enclosure to hold the PCB in place. It needs a good grip, heat glue holds for a short time but will separate after a period of time and is not a good method. The heat glue is very messy and looks bad. I tried crazy glue, it is not great either. A two part epoxy seems to work best but looks really really bad when applying by some stick or other method to spread it in the angle between the PCB and wall. I need some glue that can be placed in a bead with a small tip and have it look very neat and clean. Can anyone suggest a glue that would bond to the PCB (resist coated) and the black ABS or glass filled nylon enclosure shown? It needs to be robust and not easily separate. This enclosure presses inside another receiver part, so some force does get applied to the enclosure when pulling it back out, that is why it needs to be a strong bond.

erco

How about a construction adhesive? Those come in small squeeze tubes with tips, and also caulking gun size. You can cut the tip opening for any bead size you like. Alternatives: many times of caulking and rtv sealers to try.

W9GFO

Don't know how compatible it is with electronics but I have found Goop to be very strong. It comes in a tube and is clear and flexible when set.

Rich H

HollyMinkowski

Try the clear silicone caulk.
The type that never gets hard.
I have used it for many purposes
and it seems to really stick well.
It's supposed to stay flexible forever.
It makes nice rubbery feet for project
boards and cases....you let it dry a bit
and then press the case down on a slick
surface to flatten and level the rubbery
globs.

Erik Friesen

100% silicon should work.

Bean

For a permanent bond, use a polyurathane glue (gorilla glue for example).

Bean

localroger

I'm with Holly and Erik, this is a job for clear silicone caulk. You can get it both in small tubes and caulk gun cartridges, cut the tip down to whatever width bead you want, lay it down very neatly, doesn't conduct electricity, and when applied like this it's much stronger than you would expect. Plus it's easier to cut off if you ever want to remove it.

John R.

You mentined that epoxy was working, but messy. If you go to a "commercial" adhesive supplier, you can get epoxy of about any type in a "double tube" where both parts (even if unequal portions by using different sized tubes) are squeezed out through a "mixer". The mixer is a single tube with some stationary flights that mix the two parts as the move through. The tip of the mixer is pointed just like a caulk tube, and can be cut to give the disired opening.

For prototype, you could also go with a "pastry bag" type application.

Having said that, I'd personally be inclined to go with RTV/Silicone. (RTV = Room Temperature Vulcanizing)

John R.

W9GFO

Silicone RTV releases corrosive acetic acid during the curing process.

Rich H

erco

BTW, there are many types of "Krazy Glue", AKA cyanoacrylate, or CA. Comes in thin, medium, and thick consistencies. I use the thick gap-filling stuff almost exclusively, it stays where you put it until you can put some kicker (accelerator) on it. Thin stuff runs and capillaries where you don't want it. Might work for your app, just apply in a few spots to try it.

Per my previous post, the best use for the thin CA is to make fillets when gluing thin plates together, in conjunction with sprinking baking soda into the wet CA. Goes exothermic and makes a rock-hard compound. You can quickly build up fillets or make complete PARTS by alternating layers of thin CA and baking soda.

Phil Pilgrim (PhiPi)

Most silicones release acetic acid while curing, rendering them incompatible with electronics. There are exceptions, though. Look for assertions on the package that say something like "scentless". I believe Boatlife Caulk falls into this category.

-Phil

localroger

I have never had a corrosion problem from using silicone on circuit boards; the amount released is enough to smell but not enough to do damage. It is not very acidic even during the cure and evaporates fairly quickly (which is why you can smell it) so does not have much time to do damage before it's gone. But if that bothers you you could always Google for "neutral cure silicone," which doesn't have the problem at all.

T Chap

Thanks for all the suggestions. I tested a combination today of strategic dots of Gorilla Super Glue to give some holding strength while the silicon 'bead' sets up. The silicon is a messy option, not a fun cleanup, but I suppose there is no good clean up option. This may be a good method for a while until something else works out. The problem is that I have to hold the parts in place by hand until it sets, silicon alone is not for quick set.

Jay Kickliter

I've always been a big fan of 3M 5200 and 4200. They are permanent, but flexible. 4200 is a little less permanent bond.

mctrivia

potting compound works great and is perfectly safe on your electronics.

T Chap

Yes, I remember using some potting compound in the past and it is great, but the issue remains in the dispensing after mixing. It has to be a nice clean bead.

Ravenkallen

On a lot of materials/ some plastics ,the "Gorilla super glue - impact tough formula" works very well. I have even had success with the cheap dollar store super glue. What i do is just buy a bunch of different kinds and test them out on scrap materials. You can't really know if a glue is going to work for a particular application until you test it....

mctrivia

most potting compouinds will stay liquid for about 2 hours. if you place in your enclosure on a level surface it will self level giving a nice neat look. If you put enough in you can completely encapsulate the board to the enclosure making it water proof and tamper resistant. If you put in only enough to cover the back of the board it will be next to impossible to remove the board and if you use black potting compound will look like the board is fused to the enclosure.

K2

T: I like all the suggestions! GOOP really is fantastic stuff. Dr. Kevin Dunn uses it on all his electrostatic projects.

Here at work we use Liquid Nails "Perfect Glue." It is silicone-based but entirely odorless. It seems to set-up faster than standard RTV and bonds very well to PCBs and ABS.

(By PCBs I mean printed circuit boards, not polychlorinated biphenols.)

Edit: FWIW, "Perfect Glue" is significantly more fluid out-of-the-tube than is silicone caulk. That may be a benefit or a liability. It certainly makes a smooth surface simple to achieve. As for GOOP, it shrinks as it dries, pulling things together more tightly. That helps in some situations and hinders in others.

Capt. Quirk

(glass) Micro Ballons mixed with epoxy will form a nice bead, and looks good after it dries. Micro-Ballons will turn the epoxy white, but if you prefer black to match your case, use black ink to change the color.

Bill M.