unpotting, solvent, melting agent, removal agent, for transistor or IC cases?? - diyAudio
Go Back   Home > Forums > Design & Build > Parts

Parts Where to get, and how to make the best bits. PCB's, caps, transformers, etc.

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 4th October 2012, 12:57 AM   #1
expert in tautology
diyAudio Member
 
bear's Avatar
 
Join Date: Apr 2002
Location: New York State USA
Exclamation unpotting, solvent, melting agent, removal agent, for transistor or IC cases??

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.
__________________
_-_-bear
http://www.bearlabs.com -- Btw, I don't actually know anything, FYI -- [...2SJ74 Toshiba bogus asian parts - beware! ]
  Reply With Quote
Old 4th October 2012, 01:10 AM   #2
diyAudio Member
 
wrenchone's Avatar
 
Join Date: Feb 2004
Location: Silicon Valley
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?
  Reply With Quote
Old 4th October 2012, 01:18 AM   #3
WSJ is offline WSJ  United States
diyAudio Member
 
WSJ's Avatar
 
Join Date: May 2009
Location: GILROY, CA
I used un-potting chemicals, it expanded the epoxy and made big mess.
The PCB inside had the parts ripped apart. I found it to me useless.
  Reply With Quote
Old 4th October 2012, 02:11 AM   #4
diyAudio Member
 
Join Date: Mar 2007
Location: Canandaigua, NY USA
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 may be barking up the wrong tree, but at least I'm barking!
  Reply With Quote
Old 4th October 2012, 02:39 AM   #5
WSJ is offline WSJ  United States
diyAudio Member
 
WSJ's Avatar
 
Join Date: May 2009
Location: GILROY, CA
I used the failure analysis lab at Fairchild Semiconductor in 1966,
where epoxy devices were analyzed. We would grind the epoxy down and
use polishing wheels with different grit compounds until the die was visible.
We did this with hundreds of transistors and ICs.
  Reply With Quote
Old 4th October 2012, 01:10 PM   #6
expert in tautology
diyAudio Member
 
bear's Avatar
 
Join Date: Apr 2002
Location: New York State USA
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...
__________________
_-_-bear
http://www.bearlabs.com -- Btw, I don't actually know anything, FYI -- [...2SJ74 Toshiba bogus asian parts - beware! ]

Last edited by bear; 4th October 2012 at 01:14 PM.
  Reply With Quote
Old 4th October 2012, 02:38 PM   #7
SY is offline SY  United States
diyAudio Moderator
 
SY's Avatar
 
Join Date: Oct 2002
Location: Chicagoland
Blog Entries: 1
Epoxy won't melt, alas. Crosslinked thermoset. You're down to acid or mechanical.
__________________
And while they may not be as strong as apes, don't lock eyes with 'em, don't do it. Puts 'em on edge. They might go into berzerker mode; come at you like a whirling dervish, all fists and elbows.
  Reply With Quote
Old 4th October 2012, 03:32 PM   #8
Elvee is offline Elvee  Belgium
diyAudio Member
 
Elvee's Avatar
 
Join Date: Sep 2006
There are a number of specially formulated solvents for thermosetting plastics, including epoxy.
A typical example is the Panasolve range, but there are many alternatives now, including (relatively) green ones.
__________________
. .Circlophone your life !!!! . .
♫♪ My little cheap Circlophone© ♫♪
  Reply With Quote
Old 4th October 2012, 06:38 PM   #9
diyAudio Member
 
Join Date: Sep 2011
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).
  Reply With Quote
Old 5th October 2012, 02:05 AM   #10
expert in tautology
diyAudio Member
 
bear's Avatar
 
Join Date: Apr 2002
Location: New York State USA
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...
__________________
_-_-bear
http://www.bearlabs.com -- Btw, I don't actually know anything, FYI -- [...2SJ74 Toshiba bogus asian parts - beware! ]
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Agent needed from OKC or Dallas area who is going to Dayton, OH 7/14 jmillerdoc Swap Meet 0 19th June 2012 05:38 AM
IKEA, Orlando, FL; need purchasing agent Ed LaFontaine Swap Meet 18 30th March 2012 05:52 PM
What solvent for best removal of solder flux? space Everything Else 10 18th April 2007 08:57 AM
Chemical Stripping Agent for Magnetic Wire mbcouple Parts 8 20th January 2005 11:44 AM


New To Site? Need Help?

All times are GMT. The time now is 03:44 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright ©1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2