Ok, I have a large quantity of recently acquired transistor (TO-92 case, if that matters) that I am convinced are bogus versions. Yes they function, but the curves don't match the mfrs at all.
I would like to un-pot via chemical means the die + leads from the plastic case. What can be used that works??
Mechanical means are not an option.
I can then compare the known good NOS devices to the recently acquired devices and probably know for sure... maybe. Well, if it is night and day, then for sure. We have microscopes.
_-_-bear
PS. a search or two did not reveal this answer... if there is one.
I would like to un-pot via chemical means the die + leads from the plastic case. What can be used that works??
Mechanical means are not an option.
I can then compare the known good NOS devices to the recently acquired devices and probably know for sure... maybe. Well, if it is night and day, then for sure. We have microscopes.
_-_-bear
PS. a search or two did not reveal this answer... if there is one.
Glacial acetic acid is a good starting point. The more drastic alternatives should be avoided, as they are really nasty (not that acetic acid is a treat). A better alternative would be to check the parts out and see if they've been remarked, the usual conterfeiter's strategy ( actually making parts is too much work, so just get some inferior parts/castoffs and mark them with a hot-selling number).
Are the parts laser marked, or with ink?
Are the parts laser marked, or with ink?
Why aren't mechanical means an option? I've split TO92s well enough to see the die and confirm what it was. If you have a lot to experiment with, crush a couple in a vise from the sides and see if they'll split. Don't know what type you're dealing with, but I always found the old National Semi book on discretes useful as it had a die image for each type. I was able to ID many surplus house numbers that way.
I can try the mechanical method(s)... would prefer a straight melt away... no diamond wheels here right now...
...Conrad, I will try the vise crush method, do you mean the flat & curved sides , or the wide side in the jaws of the vise?
These are not Nat Semi parts. I will have to compare NOS to these... regardless they do *not* look the same when curve traced.
Found online in a paper that commercially strong acids are used, and that the die remains impervious... doesn't seem like "plan A".
wrenchone, I am unsure if they are laser marked, they well may be. they don't look quite right under a high power loupe. I'd say, not ink, now that you mention it. I can test for that with a bit of acetone, that ought to remove the ink and not the laser etch, I would expect.
What effect will the glacial acetic acid have on the plastic??
How long in the acid??
Have you done this??
Also, it might be easier to get "battery acid" than glacial acetic.
Is there an easy source for glacial acetic (I used to get Kodak, but that was when there were still stores that sold photo supplies for the home darkroom)?
bottom line here is Grrrrr...
...Conrad, I will try the vise crush method, do you mean the flat & curved sides , or the wide side in the jaws of the vise?
These are not Nat Semi parts. I will have to compare NOS to these... regardless they do *not* look the same when curve traced.
Found online in a paper that commercially strong acids are used, and that the die remains impervious... doesn't seem like "plan A".
wrenchone, I am unsure if they are laser marked, they well may be. they don't look quite right under a high power loupe. I'd say, not ink, now that you mention it. I can test for that with a bit of acetone, that ought to remove the ink and not the laser etch, I would expect.
What effect will the glacial acetic acid have on the plastic??
How long in the acid??
Have you done this??
Also, it might be easier to get "battery acid" than glacial acetic.
Is there an easy source for glacial acetic (I used to get Kodak, but that was when there were still stores that sold photo supplies for the home darkroom)?
bottom line here is Grrrrr...
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Fuming nitric acid (you get it to fume by boiling it) will disolve the mold compound.
Use very little acid, a fume hood and other safety equipment. It's very nasty business.
A much better idea would be to engage the services of an independant semiconductor failure analysis lab (let them play with the acid).
Use very little acid, a fume hood and other safety equipment. It's very nasty business.
A much better idea would be to engage the services of an independant semiconductor failure analysis lab (let them play with the acid).
at this price point, the independent lab will cost more than the parts... 
regular nitric acid won't do a thing??
wish I could hit it with a laser and heat it locally to boil a teeny tiny bit...
carp!
_-_-
I think I am stuck with being screwt, as they say.
They are jfets, fwiw, and they do function, just that they are very unlikely to the be ones that were claimed. Bummah...
regular nitric acid won't do a thing??
wish I could hit it with a laser and heat it locally to boil a teeny tiny bit...
carp!
_-_-
I think I am stuck with being screwt, as they say.
They are jfets, fwiw, and they do function, just that they are very unlikely to the be ones that were claimed. Bummah...
As I said, a number of solvents and ready-made mixes can do it (not all will work on epoxy B):
Attack Epoxy Solvent
Global Specialty Products - environmentally safe, non-hazardous, non-flammable, biodegradable and recyclable aqueous and solvent based industrial cleaning products.
You can also try mixes of commercial products, based on methylene chloride (paint stripper) or benzyl alcohol ( http://flexisolv.com/documents/FlexiSolv Benzyl Alcohol Technical Data Sheet.pdf ) for example
These are relatively harmless compounds.
Some (much nastier) chemicals may be more effective:
dimethylformamide (DMF), cyclohexanol, diethyltoluamide, aniline (at your own risks)
In general, it will be necessary to heat the mixture and let the part soak for several hours
Attack Epoxy Solvent
Global Specialty Products - environmentally safe, non-hazardous, non-flammable, biodegradable and recyclable aqueous and solvent based industrial cleaning products.
You can also try mixes of commercial products, based on methylene chloride (paint stripper) or benzyl alcohol ( http://flexisolv.com/documents/FlexiSolv Benzyl Alcohol Technical Data Sheet.pdf ) for example
These are relatively harmless compounds.
Some (much nastier) chemicals may be more effective:
dimethylformamide (DMF), cyclohexanol, diethyltoluamide, aniline (at your own risks)
In general, it will be necessary to heat the mixture and let the part soak for several hours
Fully cured epoxy doesn't actually dissolve, the "solvents" actually tear it up and dissolve the pieces. And if they'll tear up epoxy, they'll not be very good for humans to touch or inhale. If they're certified as safe, conversely, they won't tear up cured epoxy.
Ventilation, goggles, and gloves at a very minimum!
I'll see if i can find any of the "safer" products. Maybe they will actually work.
The die is teeny, tiny. Anything that does less than more or less gently remove the 'plastique' will likely mess up the die. By contrast opening the top of a random metal can transistor was a piece of cake. Easy to see the die clearly.
Cracking the case in a vise yielded a small square nondescript square with no clear surface or connections and a non flat surface... a mess.
I've yet to destroy any NOS part, since there is no point in that until I have a good way to get the job done...
Bwwaaaah!
Thanks for the ideas.
The die is teeny, tiny. Anything that does less than more or less gently remove the 'plastique' will likely mess up the die. By contrast opening the top of a random metal can transistor was a piece of cake. Easy to see the die clearly.
Cracking the case in a vise yielded a small square nondescript square with no clear surface or connections and a non flat surface... a mess.
I've yet to destroy any NOS part, since there is no point in that until I have a good way to get the job done...
Bwwaaaah!
Thanks for the ideas.
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