Adhesives for securing PCBs/perfboard.

I've been trying to figure out how to attach one of my circuits to the inside of a metal container. I don't want there to be any sort of imperfections on the outside of the container so I don't want to screw through the surface.

I thought about glueing the board to the inside but I don't know what kind of glue or how to glue it in there. Do I glue over the electrics or just on corners? What kind of glue would be best; hot glue, silicone, epoxy, etc.?

Any suggestions or other ideas would be appreciated.

Because it’s a metal box I would line the inside of the box with some thin plastic or cardboard to reduce the chance of things shorting out should the PCB become loose, then epoxy glue PCB terminals to the box (through cut-outs in the plastic/cardboard) to mount the PCB on. Another option would be to use ESD foam to both line the box and hold the PCB securely. As long as the PCB does not generate to much heat this should be fine.

I typically use the input devices (rotary encoders or potentiometers) to attach the pcb to the case. I buy encoders or potentiometers with PCB terminals and a threaded shank, then I solder those devices to the pcb, and attach them to the case using the threaded shank.

If you don't have that option available then I would use silicone rubber to glue the edges of the board to the box. Silicone rubber sticks to most things, and is more flexible than epoxy, so it will cope with vibration better. It is also much easier to remove than epoxy when you need to disassemble the unit.

Depending on how secure/removable I want it to be. I either epoxy/silicone the PCB into the box, or I screw the PCB to a piece of Lexan, and silicone/epoxy the lexan into the box.

You should always have holes on your pcbs, so you can use standoffs to mount them
away from the metal surfaces.

Secondly, my favorite most glue of all is Goop. It sticks to about everything, and
best of all, it stays soft and pliable and can easily be removed from surfaces
without having to use nasty solvents. Just pull it off by hand. Available in the US,
but not sold in the UK or maybe some other countries. Use all glues in a ventilated
area.

After mounting to the pcb, you can dip the ends of the standoffs in Goop and hold
them down on the metal surfaces of your box.

oric_dan(333): After mounting to the pcb, you can dip the ends of the standoffs in Goop and hold them down on the metal surfaces of your box.

My favorite glue is J-B Weld - it's basically one of the strongest 2-part epoxies you can purchase. I've seen (and used) it for things that they say you shouldn't use it for: It fixed up an aluminum blower-housing crack on my brother-in-law's diesel engine powered dump truck. Held for about 15 years until it cracked again - in a different place (at which point he replaced the housing). I've used it on an anti-backfire valve mounted to the top of the engine manifold of the V8 in my 79 Bronco; it's held fine for 8 years now.

I do think your suggestion of attaching the standoffs to the PCB, then dipping in glue and putting them in place in the box is great suggestion; regardless of the glue being used, cleaning the metal properly should be done to prevent any contaminants (oils, grease or dirt) from weakening the joints made.

I totally agree with gluing standoffs to the box and mounting the board to those. If you fix the board solidly to the box then the probability of having to remove it soon increases according to Murphy's Law.

I'm a big fan of hot glue but in your case it's probably not the answer.

My favorite glue is J-B Weld - it's basically one of the strongest 2-part epoxies

Trust me [haha], you have to try Goop if you've never done so. Since I discovered it, I've not used epoxy. Goop is also the only thing I found that'll hold well to ABS plastic, other than the stuff with the horrible solvent that melts the surface, and makes an irreversible mess.

What kinds of materials do you use for stand offs? Dowel, PVC and the like? Also I'm using a perf board I cut to size and because of that I no longer have those holes. Should I drill new ones?

Also on the subject of those threaded switches and pots, I do plan on having a switch accessible on the outside but it is not threaded and Pretty much lined up opposite to the board so I also have a problem with mounting the push button latching switch. Would it be advisable to use Goop or an epoxy to secure it?

You can use bolts and nuts for standoffs. Put one nut on the bolt to set the height you want and then another nut to fasten the board on top of that. You could even pinch the board edges between the nuts but having the bolts go through holes is more solid.

If you can find a fastener catalog, there are an amazing number of clips and bits that are less crude. It's just that in my case I have a collection of bolts and nuts and plastic mobo standoffs (hehehe, saved that for last!). What I use is first what I have and then what I can get when it comes to hobbies.

Bolts work ok for standoffs, but all of the distributors like digikey, mouser, and jameco sell standoffs, both threaded and non-threaded. They come in metal and also nylon. I've not tried to glue or Goop nylon however. That may be the exception for using Goop. Standoffs for #4 screws are the most useful for small pcbs. There are very thin hollow metal ones, and also standard 0.187" and 0.25" o.d.

On a perfboard, I would simply drill larger holes in the corners for standoffs.

For the switch mounting, you'll have to experiment and see how well epoxy/Goop holds it. I would rather use a switch with threaded nut on the outside to hold it, then it'll won't give.

Hi,

Another suggestion - 3m heavy duty double sided tape.

On clean surfaces it is amazingly strong - we use it all the time for holding escs and receivers in RC cars, its strong enough that you worry you might break you radio before you get it off the car.

If its a component i want to remove later i take care to use small sections, its that strong.

Duane B

rcarduino.blogspot.com

I don't know what these are called, but I think at Home Depot we picked up a bag of cable tie holders. Little squares of plastic with peel & stick backing and a loop on the front to secure a cable tie to. Loop the cable tie thru that, thru a hole in your board, and snug up the cable tie. One on each corner. You'll have to determine if having a thoroughly clean metal surface is enough.

If you need standoffs, you can buy small bags of them from pololu.com. I use the nylon tubes with #4 screw & nut. I'll put a nylon washer under the screw (or nut) head also to prevent any metal shorts around the hole if needed. http://www.pololu.com/search?query=nylon I don't recall which diameter I use. Used a dial caliper to measure the screw diameter, then ordered several bags in different lengths.

http://www.harborfreight.com/catalogsearch/result?q=caliper I used something like the $3 one. There's a HarborFrieght a couple towns over, next to Guitar Center, I grabbed one of the digital calipers last time I was there as they happened to be on sale (and at the other one had gone into hiding on me). Handy tool.

This is the stuff - exterior mounting tape - upto 2.3kg per square inch !

http://products3.3m.com/catalog/au/en005/office/office/node_GSZLYR7J5Zgs/root_D58K9TX3VWgv/vroot_G3SJG25V2Hge/bgel_VZTM7MGQ8Qbl/gvel_WMK00LBHNRgl/theme_au_office_3_0/command_AbcPageHandler/output_html

Duane B

rcarduino.blogspot.com

I use #4 and #6 nylon screws and nuts for many mounting needs. I have a chunk of 6mm nylon tubing from which I cut stand-off of the right length for whatever application. Another approach I use is to use a plastic enclosure and just drill holes and tie circuits down with cable ties in the corners. These work well when it’s okay to drill holes in the box.

When I can’t drill a hole, so far I’ve been bolting the boards to a piece of perspex with stand-offs, and then put that in the box with two-sided tape.

One thing I have not figured out is weather-resistant openings in the case for cables to come and go. Gooping the cable entrance with RTV or regular silicone works, but is tough to re-work if you decide you need one more conductor or something.

http://products3.3m.com/catalog/au/en005/office/office/node_GSZLYR7J5Zgs/root_D58K9TX3VWgv/vroot_G3SJG25V2Hge/bgel_VZTM7MGQ8Qbl/gvel_WMK00LBHNRgl/theme_au_office_3_0/command_AbcPageHandler/output_html

Duane B

That tape is just great. I’ve used it to attach servos on some of my walking robots.
You can hold about 500 servos with 1 $5 roll.