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theusch
PostPosted: Jul 12, 2011 - 10:11 PM
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We are on a reverse-engineering mission, more out of curiosity than anything else. (Thus, no amount of wasted effort is too much...)

We've got a small board from a sensor that does sensor excitation and signal conditioning. It is in what appears to be expoy potting compound.

Are there any methods other than grind-grind-grind to remove most of it so we can take a peek?

Lee
 
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gchapman
PostPosted: Jul 12, 2011 - 11:10 PM
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http://www.mgchemicals.com/products/832b.html
states acetone.
Else nitric acid may work but will likely destroy PCB and is not safe.
 
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DocJC
PostPosted: Jul 12, 2011 - 11:17 PM
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Of course, in 45 days he could have done the grind-grind-grind routine for 1080 hours. Wink

JC

Edit: (The 45 Days was spec'd on the site above for Acetone to be effective.)


Last edited by DocJC on Jul 13, 2011 - 08:25 PM; edited 1 time in total
 
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gchapman
PostPosted: Jul 12, 2011 - 11:28 PM
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Laughing
1080 hours - I've yet to use this stuff but it appears to be tough.
 
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Kas
PostPosted: Jul 12, 2011 - 11:56 PM
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Heat gun or chisel-ended macho soldering iron are worth trying .
At least at solder melting temperature such a compound smokes and softens, making easy removal layer after layer. Cheap and really dirty.
For chemicals it should take using quite aggressive ones, because epoxy compounds are quite inertial when set.
 
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theusch
PostPosted: Jul 13, 2011 - 12:31 AM
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Quote:

Of course, in 45 days he could have done the grind-grind-grind routine for 1080 hours.

Remember:
Quote:

(Thus, no amount of wasted effort is too much...)


LOL.

So maybe grind away the excess and then soak the remainder in acetone...

Lee
 
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Kartman
PostPosted: Jul 13, 2011 - 01:45 AM
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Most epoxies go rubbery/chalky at around 100C. So put it in the oven, heat it up (not too hot!!) and pick off chunks with a small screwdriver. Rinse and repeat. This has worked well for me on a number of occasions. The worst was one unit that was loaded with silica. It wrecked a perfectly good screwdriver by abrading it away.

There are specific compounds that will decapsulate but they are usually nasty and expensive.
 
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meslomp
PostPosted: Jul 13, 2011 - 06:31 AM
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Like Kas said a soldering iron will do.

we often use DIE's in our products and sometimes we also need to remove the potting that has been applied in the factory(there are occasions that they mount the chip the wrong way around or bond it wrong.
we use a soldering iron and then slowly remove the potting.

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ignoramus
PostPosted: Jul 13, 2011 - 09:49 AM
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Hot MEK.

Pickle the epoxy and eventually ( not weeks ) it will be pliable under Your grinder.
 
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js
PostPosted: Jul 13, 2011 - 10:20 AM
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Nitroglicerine.

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polecat
PostPosted: Jul 13, 2011 - 03:08 PM
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I've used a product called Decap http://www.ellsworth.com/display/productdetail.html?productid=5359 It was pretty effective on most epoxies, won't touch IC packages though. Just be sure to follow instructions on handling. Has kind of a sickening smell to it though. I used it back in the days of the Videocypher modules for satellite TV.

Roger
 
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RickB
PostPosted: Jul 13, 2011 - 03:44 PM
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Paste type paint remover should do it. If not, try paste type epoxy paint remover, or just use it first. It's a bit more expensive. Both are quite caustic and will break down many plastics. Use gloves and DON'T breathe the fumes. Works well as enamel wire stripper also.

Rick
 
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ignoramus
PostPosted: Jul 13, 2011 - 10:50 PM
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Make sure gloves are caustic resistant
 
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DocJC
PostPosted: Jul 14, 2011 - 03:15 AM
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OH, LOOK! There is Lee about to enter the Micro Hacking Lab! Wink
 
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Kartman
PostPosted: Jul 14, 2011 - 05:12 AM
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Ths was the stuff I was referring to but I couldn't remember the name. Points to Polecat.

http://www.ellsworth.com/display/produc ... uctid=5359

It is nasty and expensive!
 
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rberger
PostPosted: Jul 14, 2011 - 04:47 PM
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Quote:
It is in what appears to be expoy potting compound.
we used to use a Ciba Giegy LC177N resin and HY956 hardener in proportions 10:1 by weight for potting. They had a solvent (clear liquid) for it that would convert the set epoxy to flakes. This was usually an overnight process.

The solvent was not bad smelling, nor did it harm skin with minimal contact, but this was in the late 70's, so not sure if it is still available or if it would suit the epoxy used in your sensor board.
Ron.
 
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theusch
PostPosted: Jul 18, 2011 - 03:32 PM
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Quote:

So maybe grind away the excess and then soak the remainder in acetone...

That's what we did, and got a fairly clean circuit board after about a week.

Thanks, all.

Lee
 
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