[sci.electronics] reverse engineering

donaldo@fornax.UUCP (Don Smith) (06/02/90)

I would like to reverse engineer a calculator watch but am having
a hard time removing the epoxy coating the chip.  So far I have 
tried a number of chemicals including: 

   acetone
   and hydrochloric acid.

The hydochloric acid removed the epoxy but also damaged the chip. It
appears that the epoxy is a cross linked polymer structure which is
hard to break apart. I would appreciate the names of chemicals which
can break up cross linked polymers without damaging the chip.  The
watch is an inexpensive OEM type watch costing about $10.

tomcat@cbnewsl.att.com (fred.j.shubert) (06/05/90)

In article <778@fornax.UUCP>, donaldo@fornax.UUCP (Don Smith) writes:
> I would like to reverse engineer a calculator watch but am having
> a hard time removing the epoxy coating the chip.  So far I have 
> tried a number of chemicals including: 
> 
>    acetone
>    and hydrochloric acid.
 



A while back I did RE on a number of devices.  I got to the point that
I could still run the chip _after_ opening it (DIPs).  If the metallization
on the chip is alumunim (you probably don't know) then you want to use
boiling 99.99% sulfuric acid.  WARNING!!!!!  This is NASTY shit.  Acids
will not open these epoxied devices unless it or th eacis is hot.  You
can heat the part to >200 degrees F and use an eyedropper to SLOWLY
etch away the epoxy.  As the epoxy etches off, rinse with isopropanol
(off the hot plate) and air dry.  Then continue the process until you see
silicon.  If the metallization is gold, use boiling fuming nitric acid
and the same process.   Remember, this is VERY DANGEROUS AND I REALLY
RECOMMEND YOU DON'T RISK LOSING YOUR SIGHT, FINGERS, OR LIFE TO LOOK
AT A CALCULATOR CHIP.  THIS TYPE OF WORK BELONGS IN THE LAB USING
APPROPRIATE EQUIPMENT OBSERVING THE PROPER LABORATORY SAFETY PROCEDURES.
I PROVIDED THIS INFO TO SHOW YOU THAT YOU ARE REALLY MESSING WITH FIRE!!

     
If you really want to discuss this further, E-mail me and have a
company or college chemistry lab and supervision available.  Then
we can talk.



______________________________________________________________________________
Fred J. Shubert         | "You haven't lived until you've seen a 'cat fly!!!"
AT&T Bell Labs          |-----------------------------------------------------
Whippany, N.J.          | DISCLAIMER:  All views are that of my own. PERIOD.
Ma-Bell 201-386-3094    |              Who else could be so 'cat crazy!!

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             Let's turn and burn!!

larry@kitty.UUCP (Larry Lippman) (06/06/90)

In article <778@fornax.UUCP>, donaldo@fornax.UUCP (Don Smith) writes:
> I would like to reverse engineer a calculator watch but am having
> a hard time removing the epoxy coating the chip.  So far I have 
> tried a number of chemicals including: 
>    acetone

	If you are dealing with a true epoxy compound (as opposed to say,
a thermoformed polymer), you are generally barking up the wrong tree using
acetone or other ketones (such as MEK, methylethyl ketone).

>    and hydrochloric acid.
> The hydochloric acid removed the epoxy but also damaged the chip.

	Not at all surprising!

> I would appreciate the names of chemicals which
> can break up cross linked polymers without damaging the chip.  The
> watch is an inexpensive OEM type watch costing about $10.

	I can give you the names of two chemicals to try which I have
personally used in years past for this purpose: dimethylformamide (DMF)
and 1,4-dioxane.  Your mileage will vary depending upon the actual
epoxy that has been utilized.  HOWEVER, THESE CHEMICALS ARE EXTREMELY
HAZARDOUS and should only be used in a properly constructed fume hood
by technically competent persons.  Don't even THINK of trying to use
these chemicals at home!

Larry Lippman @ Recognition Research Corp.  "Have you hugged your cat today?"
     {boulder||decvax||rutgers||watmath}!acsu.buffalo.edu!kitty!larry
VOICE: 716/688-1231 || FAX: 716/741-9635  {utzoo||uunet}!/      \aerion!larry