I need to remove the connector from a PCB which was completely covered with soft transparent silicone (?)

I was told heat would not really help. Any suggestions? Caulk remover? Mineral spirit? What would be the procedure - do I submerge this into the remover? For how long? I do not want to damage the plastic part which makes it tricky.

Here is where I am at right now. So far only mechanical brute force applied:

Here is how this stuff looked before I've started messing with it:

 

It is probably Conformal Coating, bit of a devil to remove.
Max.

 

try acetone, or nail polish remover.

 

Referring to the colorless, grease looking stuff, if that is really conformal coating, then I agree on the use of a lacquer type solvent, e.g., acetone or lacquer thinner.

It does not look like conformal coating to me given its thickness and apparent texture. It may well be silicone, and nothing dissolves silicone caulk. There are some ways to denature it, however.

There are three ways I know of to remove silicone rubber caulk:
1) Mechanical -- just pick it off
2) Isopropyl alcohol (99%) and light mineral spirits, 2:1 (e.g. ,VM&P Naphtha, Stoddard solvent) -- requires a lot of soaking and rubbing, but eventually the mineral solvent disrupts the bond to the substrate and it comes off. I use this mixture for the final clean up when there is just a slight haze of the caulking/rubber.
3) A type of caulking remover that contains a sulfonated, long-chain hydrocarbon : CH3(CH2)nSO3H (http://en.wikipedia.org/wiki/Sulfonic_acid). Those removers are relatively recently on the market. They denature the silicone and facilitate its removal. One brand is McKanica (http://www.acehardware.com/product/...182&KPID=2373634&kpid=2373634&pla=pla_2373634). My experience with "Motsenbockers" silicone caulk remover available at Home Depot, which I had hoped might be a bit safer and less aggressive than the sulfonic acid, was that it was a complete waste of money. The secret of the sulfonic acid appears to be that the long carbon chain facilitates penetration through the hydrophobic silicone. Then the strongly acidic sulfonic acid group denatures the silicone and disrupts the bond to the surface. The problem, of course, is that the sulfonic acid is quite a strong acid. It is in the same class as sulfuric acid (battery acid). It will not be kind to electronic parts. However, if the board under the silicone was coated with an epoxy resist or conformal coating, you might get away with using it.

My first choice would be soaking in the IPA/Naptha and then trying mechanical remomval. Only if that failed, and I really needed to get the silicone off, would I go with the sulfonic acid.

John

 

there are some commercially available 'silicone remover' products available. it actually breaks down the silicone bonding to enable removal (eg silicone in bathrooms)

not sure whats available in the states, downunder we have http://www.selleys.com.au/sealants/silicone/remover/

 

commercially available 'silicone remover'

Right, that's only if the once available to regular Joes in regular hardware stores are strong enough A bit above there is some negative experience with "Motsenbockers" silicone caulk remover which is a spray.

I've just cut my connector in pieces (it's four housings together), and submerged one piece in liquid "Goof Off" and another piece in VM&P Naphtha. Will see how it looks in three hours from now.

 

McKanica is available at Ace Hardware stores. If you check the link, you will probably find one in Chicago. You may need to order it shipped to store. The price is a bit steep for what it is.

As they say:
Easy to find
Works
Cheap

Pick two out of the three.

John

 

40 minutes update:
"Goof Off": silicone got a bit softer
VM&P Naphtha: silicone has expanded x2 & got even more softer

 

i second the vote on the naptha/kerosene soak. It will not damage most boards and components.
Mechanical removal is still needed, a stiff nylon bristle brush works well.
2-propanol or isopropal will remove most of the greasy residue you are left with.

 

2 hours of VM&P Naphtha
tooth brush cleanup
2 hours of fresh VM&P Naphtha
tooth brush cleanup & warm soapy water
success

Thank you!

 

2 hours of VM&P Naphtha
tooth brush cleanup
2 hours of fresh VM&P Naphtha
tooth brush cleanup & warm soapy water
success

Thank you!

I am impressed.

Nice work from the mess you had to start with.