PCB "glue" for Electrolytic Caps.

erky32

I'm just carrying out the Fromel mods on my failing HRDX which involves replacing the electrolytic capacitors. These are bonded to PCB with some silicon-like semiflexible stuff for mechanical stability. Whatever I use needs to be heat resistant and won't leach out any corrosive chemicals. I believe Hot-melt is no good because of the heat issue, silicon sealant unless neutral contains acetic acid. What do the pro workshops use & where do you get it? Or from experience , do the former two products work as well?

jpfamps

I use Silcone.

The Servisol Silcone adhesive is non-corrosive.

gringopig

.

Headphones

The board and components are designed to withstand the heat of soldering, so I'd doubt there's a real issue with a hot glue gun - though I've not used it myself in this role.

erky32

Headphones said:

The board and components are designed to withstand the heat of soldering, so I'd doubt there's a real issue with a hot glue gun - though I've not used it myself in this role.

it's an issue of remelting due to heat losing its bonding effect.

ICBM

I use hot melt. The board doesn’t get hot enough to melt it, and in fact if it does soften it, it will improve the bond not weaken it, because it it will get sticky again. If the temperature was high enough to melt it fully it would be a hazard to the caps anyway.

The purpose is just to stop vibration weakening the solder joints, it doesn’t actually need to be strong.

erky32

Cheers @ICBM I was looking forward to your twopennyworth  ....I'd never considered that rebonding aspect, but it makes good sense to me, I had become aware that some glues would dry out, harden and become ineffective. If you use hot-melt thats good enough for me. There is some evidence of heating on the board under the two white power resistors, but I understand the best advice there is to give them 1/4" of free breathing space.
Thanks for your advice again!