Goo on automotive electronics - best method to remove? Acetone?

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JaMora

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Hello GRF members. I'm sure a lot of you have run into this situation before. I have two questions someone may be able to assist with:
  1. In the pictures, I find many automotive electronics that have a membrane of goo over a ceramic board with exposed 'lose' gold bond wires. Does anyone have an easy and safe way to remove about a 1 cm of goo on a ceramic board? Would acetone be a workable solution?
  2. The other issue is that these aluminum computer encasings have an extremely strong glue that bonds the ceramic boards to the aluminum. I have only so far attempted to use a high power heat gun but to no avail. If said goo is removed - Does anyone have any intelligent solutions to remove the ceramic boards from the aluminum?
Thanks in advance, and Merry Christmas! (soon) :)

Image 1 - goo still on one of these boards
Image 2 - have rubbed most of it off by hand
20211221_124512.jpg 20211221_124517.jpg
 
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Most adhesive resins get brittle and/or lose adhesion in freezing temps. As for the “goo,” MEK is probably your best bet.
 
Polar organic solvents like acetone, MEK or ethyl acetate should work. Also dichloromethane is very good solvent for dissolving any kind of stubborn resin/paint stuff (that is why it is used as paint remover). Toluene could work also, but it is often less "powerful".

Glue could be one-component, two-component or solvated. Glue which set is mixed from two diferent monomers, which polymerise together, and these types of glues can´t be dissolved in solvents - only in destructive ways eg with oxidating acids etc... And heat does not much to them, they only loosen when starting to decompose.
One component glues such as superglue polymerise to long chains, thus creating "glue" effect. These could be dissolved to some extent, but it is often very difficult. Heat could help, but as in the first case, not very much.
Solvated glues work by dissolving short chains of monomers in some solvent, applying it and letting the solvent evaporate - what creates sticky viscous substance adhering to the surfaces. Sticky tape, any kinds of flexible glues etc... This could be dissolved fairly easily and heat also lower the viscosity - so two surfaces could be slowly "unglued".

If for gold recovery, i would not bother about shape in which you will get it out :) I will just crack it and loosen the pieces out. Then get it a good acetone/MEK bath, fish it out and wash with some fresh acetone to get rid of the last traces of glue.
 
Thank you @Jado and @orvi for your responses, much appreciated.

I've decided to go with both acetone and MEK. I placed items in separate baths of each solvent to see which works best to assist in removing the protective film of goo..

I expect, as orvi said, I will need to break the ceramic away from the aluminum casting after the goo is removed, regardless of the condition of the ceramic board haha. Thereafter, place into the pile of ceramic gold crystal oscillators for later processing.

I will reply after a conclusion is met, in case the outcome will help anyone else.
 
I might receive well-deserved flaming but warm sulfuric acid is hard on organic materials (including you). Resins are organic. It is not highly reactive against metals you are targeting.
You should become very comfortable with your PPE and fume management requirements before trying this though.
 
I might receive well-deserved flaming but warm sulfuric acid is hard on organic materials (including you). Resins are organic. It is not highly reactive against metals you are targeting.
You should become very comfortable with your PPE and fume management requirements before trying this though.
Yes, it will decompose it right away. Wet leach of any organic is messy... Sure, it works, but somewhat i dont like the whole thing :) creating few liters of acidic corrosive organic-toxic junk. What to do with it aside from putting down the drain ?
 
Yes, it will decompose it right away. Wet leach of any organic is messy... Sure, it works, but somewhat i dont like the whole thing :) creating few liters of acidic corrosive organic-toxic junk. What to do with it aside from putting down the drain ?
Boiling sulfuric (eg the waste you mentioned) turns carbon to CO2 and you can remove other liquid from the sulfuric via distillation. The sulfuric can be reused and I do so extensively after using sulfuric to recover my nitric from copper nitrate waste. Hella dangerous to the unprepared.
 
Boiling sulfuric (eg the waste you mentioned) turns carbon to CO2 and you can remove other liquid from the sulfuric via distillation. The sulfuric can be reused and I do so extensively after using sulfuric to recover my nitric from copper nitrate waste. Hella dangerous to the unprepared.
True, to some extent it will release CO2 and SO2, but some aromatics are generally quite resistant and you produce quite a bit of them by dissolving resins and stuff. It cannot be seen because they are well sulfonated and soluble. Not a big issue from our wiew (in quantities we do), but here where I live, similar junk was disposed (like it was straight from the "pot" to the open pit) for many and many years during 50-80s. Big bad for enviroment :)
Stay safe. I´ve done similar stuff in my beginnings, but now i try to avoid using nitric on everything (as hobbyist-banned for public use here, hard to access).
 
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