Electronics > Repair
Glue for smoke sreen
Laval:
Hello everyone,
I got a Keithley 2015, a friend of mine who works at the university sold it to me for very cheap. I recapped the boards and replaced a couple of oxidized connectors and it work great. The smoke screen over the display is in very bad condition though. It had stickers on it and someone tried to remove them using acetone (I assume) which completely ruined the acrylic. I got a replacement part (from eBay) and I removed the old one. It is fairly easy using a simple spudger. I'm just not sure what kind of glue to buy to put the new one in place. The glue on the old part is not a hard curing glue. It's sticky and rubbery a bit like silicon. It ca be scraped off for the most part and makes little sticky balls when removed. The residue can be cleaned up with IPA or mineral spirit. Anyone know what kind of glue it could be ?
jpanhalt:
What you describe sounds like a very soft, sticky, hot melt glue. Some synonyms are "snot glue, credit card glue, fugitive glue." The first two I have seen more commonly. Hot melts are often easily removed, but not dissolved by IPA.
Do you know the plastic type? If acrylic (or similar), I would recommend against any instant glue (cyanoacrylate, CA), even the fumeless variety. I would also recommend against anything with MEK/acetone/aromatic hydrocarbons as its solvent. A water-based glue, like carpenters glue will seem to hold, but peel strength is very low.
That leaves a neutral curing adhesive like electronic grade silicone or polyurethane. Both are hard to remove, so snot glue would be a top choice of mine to replicate your observations, but I have never done that repair. (IPA will help remove silicone but not as easily as it does with hot melts.)
EDIT: There are some so-called plastic safe CA glues, but I have no experience with them. They harden and are not like what you describe.
Stray Electron:
Not that I am recommending super glue (cyanoacrylate) but FWIW I have used that around displays but then placed a fan nearby to draw the fumes away from the display so that the fumes don't attack the display bezel. It doesn't need a lot of air flow, just enough so that the fumes can't collect and settle around the display.
Another word of note, SG fumes can also built up on conductive surfaces and prevent them from making contact with other conductive surfaces, such as on keyboards or when two circuit boards are pressed together. It can also probably prevent IC and other sockets from making contact. Using a fan seems to prevent any problems, BUT it's probably safer to use some sort of hot melt glue or electrical grade RTV if you have a choice.
Laval:
--- Quote from: jpanhalt on April 21, 2024, 01:51:37 pm ---What you describe sounds like a very soft, sticky, hot melt glue. Some synonyms are "snot glue, credit card glue, fugitive glue." The first two I have seen more commonly. Hot melts are often easily removed, but not dissolved by IPA.
Do you know the plastic type? If acrylic (or similar), I would recommend against any instant glue (cyanoacrylate, CA), even the fumeless variety. I would also recommend against anything with MEK/acetone/aromatic hydrocarbons as its solvent. A water-based glue, like carpenters glue will seem to hold, but peel strength is very low.
That leaves a neutral curing adhesive like electronic grade silicone or polyurethane. Both are hard to remove, so snot glue would be a top choice of mine to replicate your observations, but I have never done that repair. (IPA will help remove silicone but not as easily as it does with hot melts.)
EDIT: There are some so-called plastic safe CA glues, but I have no experience with them. They harden and are not like what you describe.
--- End quote ---
Yes, I don't want to use a hard glue like cyanoacrylate because I want to be able to remove it later should it need to be replaced again.
The smoke screen is made of acrylic and the front panel on which it was glued is made of ABS.
Thank you for the post, I'll look for some snot glue (that one makes me laugh :-DD) but it's a good description. I wouldn't say it is easily dissolved by IPA, there was very little residue left on the ABS panel which I removed with IPA but it doesn't work as well on the acrylic screen (not that I need to remove the glue on it, just testing).
jpanhalt:
If you have not used IPA to remove hot melt from a hard surface, try it. It's like magic as it has just the right properties to wick under the hot melt and break the bond. I usually use 91% or 99%; some people use a lower percentage. Rather than having to pick little pieces, it comes off cleanly in big chunks.
EDIT: Also IPA is generally safe does not cause cracking on ABS.
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