How best to remove glued down capacitors without damaging the board?

[hydrogen maser]

Subject says it all - "How best to remove glued down capacitors without damaging the board?" These are the typical larger elctros in a power supply glued down to the circuit board. This device is at least 15 to 20 years old and the glue appears to be just that - some type of glue - semi-transparent, light brown and hard and not: the white soft but tough stuff often seen - "silastic". Hot air? Solvents? Acetone? I really don't want to damage the board on this one.

[nidlaX]

Subject says it all - "How best to remove glued down capacitors without damaging the board?" These are the typical larger elctros in a power supply glued down to the circuit board. This device is at least 15 to 20 years old and the glue appears to be just that - some type of glue - semi-transparent, light brown and hard and not: the white soft but tough stuff often seen - "silastic". Hot air? Solvents? Acetone? I really don't want to damage the board on this one.

I puzzled over this while repairing my Keithley 193. My solution: cut around it with a knife, try to scrape some off the PCB as best as I can, then replace the caps and forget about it.

[Shock]

The heat and the IPA is probably more effective if the glue isn't baked hard. But I just tried it on a super hard dried out glue on a SMPS I have in front of me.

Aim to get it off the PCB board (not the component) as once the component can be removed you can clean it up easier.

I soaked a cotton bud/swab and dabbed around the edges in a controlled manner periodically for about 20 mins going between the different spots.

After you have done that and only if you can (for smaller components) gently push the component in the direction away from the bonded seal which can make a tiny gap on the seals edge to apply more IPA into, just do that while applying more IPA. A very small movement will start to release it without effort.

Once the IPA has had plenty of time to settle in, with your tool of choosing (fine tipped pliers) now try to squeeze the glue and crush it up slowly on itself while giving the component extra support with your fingers, it should break apart and instead of messing up the component or pcb hopefully the IPA got in there and it comes away cleanly.

Another way of long soaking is to make a tissue ball or cotton ball and use a syringe to keep it moist with IPA. I think this method breaks up the bond only, a mineral or citrus solvent may eventually make it goo like.

When you get some glue off you can test it in the solvent of your choice.

[hydrogen maser]

Thank you very much for the info Shock, will definitely go that route next time. It turned out that for this project all I had to do was wiggle the caps a little after desoldering and it broke the glue bond (and took off some of the solder mask in a few places but no major harm done).