Agreed, don't bother heating it. Just allow more time.

 

I was just helped a friend open an old HP calculator so he could get the chips out. His goal is to photo-micrograph of the bare die as the first step in extracting the software from the ROM.

He says the way to de-pot an epoxy cased IC is to use fuming nitric acid! If I understood him correctly this is 80% pure acid.

Note: Obviously, I am no chemist. Thanks to the others on this forum who are.

 

I was just helped a friend open an old HP calculator so he could get the chips out. His goal is to photo-micrograph of the bare die as the first step in extracting the software from the ROM.

He says the way to de-pot an epoxy cased IC is to use fuming nitric acid! If I understood him correctly this is 80% pure acid.

Note: Obviously, I am no chemist. Thanks to the others on this forum who are.

Thanks for the story, Richard... I might consider using that stuff as a last resort... if ever my life becomes so bleak that I'd want to meet the Lord before my time is due...

 

well... it's been about 20 hrs since I placed the piece in the jar with the paint remover... and as expected, all of the paint fell off... but the plastic (or polymer, or whatever it is) is intact... it hasn't softened or swelled or anything... it hasn't even lost its black coloring ... the thing's hard as a rock... what now?

EDIT: What if it were Bakelite or some sort of phenolic ???

 

I would suggest an x-ray.

Where does the demand come from for companies like Dynaloy?

 

I am not surprised with that result. Did you physically reduce the amount by grinding before soaking? Grind off a sliver and burn it. Bakelite has a characteristic odor. I doubt it is Bakelite. Regardless of that, burning a small chip may narrow the possibilities down.

Anyway, for simple solvents, that leaves NMP. Heat is another option. Epoxies can have a wide range of glass transition temperatures, Tg (http://www.epotek.com/site/files/Techtips/pdfs/tip23.pdf ). Your PCB may be relatively high (e.g., 140°C), while the potting might be a lot lower, say 110° to 130°. It won't melt like butter, but it will become flexible enough so you can peel it. Again, getting rid of as much potting material as you can with mechanical means is very important.

John

 

Yeap, x-raying the thing is definitely on the table... I'll see how I can get NMP this monday, I'll test it, and then get back to this group with the results.

 

When all else fails, Google. http://www.dynaloy.com/products/epoxy

https://www.google.com/search?q=epo...la:en-US:official&client=firefox-a&channel=sb

 

@shortbus
That's good to know. Here is a snippet of the MSDS for Dynaslove 185:

NMP (aka 1-methyl-2-pyrrolidinone) is 80 to 90% of the mixture. My intuition in post #48 is consistent with that. I guess we were on the way to re-inventing the wheel. The other compounds in the mixture probably act emulsifiers or surfactants. I am now more optimistic that PeelAway7 or even neat NMP will work.

I emphasize again the importance of removing as much polymer physically as is practical before trying a solvent. That may reduce the time needed dramatically.

John

Edit1: I responded to the company and asked about retail outlets or distributors in Monterrey, Mexico. Will keep you updated.

Edit2: Just heard from the company,"Ellsworth Adhesives is one of our Distributors here in the US, and I believe they also service Mexico." The agent also added that you can buy directly from Dynaloy (an Eastman Chemical Company subsidiary), but they do not ship to Mexico.

 

@shortbus The agent also added that you can buy directly from Dynaloy (an Eastman Chemical Company subsidiary), but they do not ship to Mexico.

Yeah, I had heard of Dynaloy before, but I had ruled it out (prematurely, as it seems) because they don't ship to Mexico. I should've re-checked them after I learned the list of possible solvents posted in this forum. I'll see and try to get my hands on some NMP today, if I can. Thanks again.

 

Update: just found a few distributors down here of NMP that are even willing to hand me a few samples so I can test it on my application.
I've also got its safety data sheet, and it seems that it will be a thing I'm going to have to be careful with.
I'm going to have to find suitable gloves to handle this substance, since it says here that nitrile is not a good choice.

 

It used to be considered quite safe. Try neoprene gloves. And of course, wear eye protection. Nothing will hold up very long. Just try to avoid getting it on you. You can imagine doing a ceiling with it. I wore a bunny suit, because you just couldn't keep it from dripping.

I expect what you will get will be a gooey mess, which you can then use MEK or acetone to clean up.

John

 

It used to be considered quite safe. Try neoprene gloves. And of course, wear eye protection. Nothing will hold up very long. Just try to avoid getting it on you. You can imagine doing a ceiling with it. I wore a bunny suit, because you just couldn't keep it from dripping.

I expect what you will get will be a gooey mess, which you can then use MEK or acetone to clean up.

John

Thanks John... one last thing, what's the best way to dispose of the gooey mess (including the one I already have)? Should I mix it with something to neutralize it before throwing it away?

 

There is nothing really to "neutralize" as in acids or bases. In the US, small producers of volatile-solvent waste can allow those solvents just to evaporate. The residue can go in the solid waste. The epoxy board itself can also go in the trash. Larger users in the US used to be allowed to burn similar waste, but I don't know the current regulations. Governments are kind of sensitive to people burning chlorinated hydrocarbons (e.g., methylene chloride), but that won't be a problem with NMP. If you look at its structure, it is not that much different from the amino acid proline, which is in ordinary proteins.

I would just let everything dry out or add some absorbent to it, even paper towels, and put it in the solid waste.

John

 

Can you get a schematic of the circuit?
If you are simply wanting to know what is inside?
You might even be able to get an idea of the location of various parts you suspect for failure.

I've done a couple of power supplies, with the hammer and chisel method, and depending on the size, they aren't usually that difficult. A drill with various bits helps also.

You might also try freezing the part, then use the Hammer and Chisel method.

HTH

 

You might also try freezing the part, then use the Hammer and Chisel method.HTH

Thanks for the tip... I'm going to consider chilling the part as you say...

 

Cool with liquid nitrogen??? Cheap and readily available. Not as dangerous as the other stuff I have mentioned...

 

Cool with liquid nitrogen??? Cheap and readily available. Not as dangerous as the other stuff I have mentioned...

I just MIGHT use your advice as a last resort... thanks...

 

I have finally gotten a sample of NMP from a local distributor. It's about 200 ml, more than enough to completely submerge the part ... This morning I took the piece out of the jar and rinsed it and cleaned it thoroughly. And let me tell you that after more than three weeks submerged in paint remover (Methylene Chloride) the only thing that happened to it is that its red paint fell off... as for the encapsulating plastic, nothing, and I mean absolutely nothing happened to it... it didn't decolorize or swelled or turned soft or changed its outward appearance in any way whatsoever... The thing is hard as a rock, though it can be scratched a little with a conventional knife, and I was even able to slice a small sliver from it, which turned out to be quite brittle and fragile... it even made me wonder if what I'm dealing with is a plastic or not...
Anyway... I just placed it in the jar and I'll wait until tomorrow to get back to this forum with the results... I'm crossing my fingers here...

 

... I'm crossing my fingers here...

It is amazing how often crossed fingers are a vital part of success in the lab yet not required once a product goes into production.

Interesting note: in Germany, they do not say "cross your fingers", but rather, "press your thumbs" for good luck. Although it is often said, I have never seen anyone make a thumb pressing gesture so I don't know exactly how it is done - more of a saying than an action, I guess.