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Author: Subject: Dissolving plastic/epoxy case of integrated circuit w/o dissolving metal leads
RogueRose
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[*] posted on 2-12-2019 at 08:30
Dissolving plastic/epoxy case of integrated circuit w/o dissolving metal leads


I'm trying to figure out a way to either cover the metal leads on an integrated circuit or at least mask off an ares of the chip, leaving an area uncovered which can be attacked by an acid.

The IC's are usually made of thermosetting polymer or thermoplastic with ultrafine glass particles while the others use a ceramic so IDK how good nitric acid would work on the ceramic but I know the HF will work for this.

There are some tutorials online that show the decapping technique and they use heated fuming nitric acid or a ~10% HF solution, both of which are pretty nasty to mess with.

Since FNA seems to work well, IDK if it is b/c it's an oxidizer or not, but I've also heard that concentrated H2SO4 works as well, especially when heated. I'm interested in trying H2SO4 + H2O2 or even HCl + H2O2. If anyone has any suggestions on something else to use, I'd be interested.

The process of "decapping" requires placing a drop of acid in the same location over and over until it reaches the circuitry. I was thinking the only thing that will work is something like sticky PTFE tape to mask off the top of the chip. I'm wondering if something can be placed on the leads (metal legs) to protect them as well. I thought paraffin may work well if the temps are kept low. I was wondering if H2SO4 + H202 (35-50%) might allow a lower temp to be used, or even just room temp, allowing paraffin to either protect the leads or even to mask off an area.

Some people have been using "Viton" which is a flourine based chemical but is is EXTREMELY expensive and rare, or was when they produced the guide. Luckily only a small amount is needed. So


There seem to be a number of PTFE based tapes availble and they aren't very expensive for the amount needed.

https://www.amazon.com/Coated-Fabric-Teflon-Adhesive-Tempera...


Some other PTFE tapes
https://www.customfabricate.com/tapes/ptfe-tapes-fabrics.htm...

https://www.fiberflon.de/Products/PTFE-Adhesive-Tapes/Page-3...

https://www.adezif.com/ptfe-adhesive-tape

https://www.tapecase.com/sd/tapes-die-cuts/1076/1/1/0.0/ptfe...


Microchips1.jpg - 116kB
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sodium_stearate
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[*] posted on 2-12-2019 at 10:22


Haha! Nice pic of the ceramic packages on those
eproms. :cool:




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B(a)P
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[*] posted on 2-12-2019 at 11:07


This guy does a similar thing using nitric, but he does mill a slot in first to hold the acid.
https://youtu.be/mT1FStxAVz4

[Edited on 2-12-2019 by B(a)P]
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RogueRose
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[*] posted on 2-12-2019 at 11:41


Quote: Originally posted by sodium_stearate  
Haha! Nice pic of the ceramic packages on those
eproms. :cool:


Ahh, but you are confused. You see those are an example of my expert decapping skills which show how perfectly I bore a hole straight down the middle and then installed a glass window so I could admire it later.

IDK what you were implying, if I didn't know the diff between epoxy/glass and ceramic or if you liked the pic, but I just choose it b/c it was on the wiki for IC's and I liked the pic, I'm always excited when I find them on boards I'm going though and can pull them off.
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RogueRose
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[*] posted on 2-12-2019 at 11:46


Quote: Originally posted by B(a)P  
This guy does a similar thing using nitric, but he does mill a slot in first to hold the acid.
https://youtu.be/mT1FStxAVz4

[Edited on 2-12-2019 by B(a)P]


I was trying to find a way to do similar but protect the metal leads at the same time which is why I thought maybe the PTFE tape to mask an area might be a good idea. Much of it is good for 400-500F. IDK if the acid will work it's way under the tape/adhesive but I think it might be worth trying.
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B(a)P
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[*] posted on 2-12-2019 at 12:33


Yeah, the acid may well attack the adhesive, particularly if you need to earn it like in that video. Worth a go though for sure.
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sodium_stearate
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[*] posted on 3-12-2019 at 07:35
ceramic ic package


It's all good....

I was just being snarky because your post
is about decapping plastic-packaged ics, and then
there's a picture of some ceramic ones.

Hmm......:cool:




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wg48temp9
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[*] posted on 3-12-2019 at 09:58


Ebay sells FEP sheet and tubing, FEP is a fluoropolymer with about one in four of F replaced with Cl. FEP has similar chemical resistance to PTFE but it becomes soft and sticky at about 300C. Perhaps you could use that for the walls of a well.





i am wg48 but not on my usual pc hence the temp handle.

Thank goodness for Fleming and the fungi.
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draculic acid69
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[*] posted on 3-12-2019 at 19:24


What about pvc pipe glue.that blue stuff?
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hyfalcon
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[*] posted on 4-12-2019 at 03:27


MEK will attack the plastic packages.
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draculic acid69
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[*] posted on 4-12-2019 at 04:28


Isn't dissolving the plastic what your trying to do.
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