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How to open chips

Discussion in 'Electronic Design' started by Janvi, Jan 30, 2004.

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  1. Janvi

    Janvi Guest

    Heard that it is possible to open
    IC cases to free the chip for optical
    examination and bond wire pull tests
    by the use of fuming nitric acid.

    Anybody experienced with that procedure?
     
  2. Jim Thompson

    Jim Thompson Guest

    I think it's likely to ruin wirebond-pull testing. But photos will be
    OK.

    My favorite way to get die photos was to run the plastic package thru
    a thick-film firing furnace; then pick off the ash, leaving an
    undamaged die.

    ...Jim Thompson
     
  3. Do a web search. The chemicals are nasty and expensive if you have to
    buy them from a lab supply outfit in small quantities. There are
    companies that do this in exchange for reasonable amounts of currency
    of various sorts.

    Best regards,
    Spehro Pefhany
     
  4. Most adhesive houses also sell epoxy strippers.

    --
    Many thanks,

    Don Lancaster
    Synergetics 3860 West First Street Box 809 Thatcher, AZ 85552
    voice: (928)428-4073 email: fax 847-574-1462

    Please visit my GURU's LAIR web site at http://www.tinaja.com
     
  5. S.M.Taylor

    S.M.Taylor Guest

    Doesn't Formic Acid work too ?

    Steve
     
  6. Jeff

    Jeff Guest

    Look up info in google for people hacking microcontrollers. Nitric acid is
    used to strip the plastic/epoxy, and the chip is then fired up and
    microprobed to retrive data. The bond wires seem to remain in tact.
     
  7. Mike

    Mike Guest

    One such company is located close to me in Southern California, and will
    decap standard plastic parts for (IIRC) around $50, typically the same day.

    -- Mike --
     
  8. Mike

    Mike Guest

    Will it? I have parts decapped when I need to probe. After decapping, the
    chip and bondwires are exposed and electrically undamaged. We don't use Al
    or Cu bondwires, which might be sensitive to the acid. It would seem to me
    that if there was mechanical damage, there would also most likely be
    electrical damage as well (and I'm presuming a complementary relationship:
    the lack of electrical damage implies a lack of mechanical damage).

    -- Mike --
     
  9. Mac

    Mac Guest

    I seem to remember that formic acid is particularly hazardous, but I don't
    remember the specifics. Make sure to read the Material Safety Data Sheet
    (MSDS) if you use it.

    Mac
     
  10. Mac

    Mac Guest

    No, but I wouldn't want to handle fuming nitric acid outside of a properly
    equipped lab. Also, you can use fuming nitric acid to make TNT, IIRC. So
    maybe people will become interested if they see you buying it. Then again,
    it may be so common, and used for so many things that it doesn't register.

    Good luck, and be careful.

    Mac
     
  11. When we started dealing with one of the big companies, they required
    an company account (which entails a credit check, banking information
    and vendor references, so they know you are for real) and a real
    person also asked a few questions about what they were to be used for
    (even though the chemicals were not very toxic or dangerous AFAIUI).
    After you have an account set up for a few years they are not as
    fussy. This is for Canada, the US is probably much more paranoid these
    days. Both for the above-mentioned concern and for liability issues
    (imagine if they were found to have shipped dangerous chemicals to a
    kid who injured himself or others). Although you can get all kinds of
    weird and wonderful stuff, the prices are insanely high for any kind
    of production work. For what they charge for a few kg you can
    probably get a MT (metric ton) of many commonly used chemicals. With
    disposal issues and hazmat shipping ($$$$), even though we have an
    in-house expert on such matters (the consultants for that kind of work
    charger at least as much as engineering consultants), I prefer to stay
    away from them as much as possible.

    Best regards,
    Spehro Pefhany
     
  12. Janvi

    Janvi Guest

    Most adhesive houses also sell epoxy strippers.

    do you have any brands or article # already proven?
     
  13. Dave Cole

    Dave Cole Guest

    Formic acid dissolves nylon very well; not sure about epoxy. Maybe acetone?

    Dave Cole
     
  14. Octa Ex

    Octa Ex Guest

    No

    but I have decapped chips with a lawn mower.
    Place the ICs on the lawn and run the running lawn mower over it.
    It does a rough job,
    but some chips are decapitated well enough to see the wiring!

    X X
    X
    X X
     
  15. That's an interesting technique! Can you recommend specific types of
    lawn mower that work well? Is it better to work with a blunt blade or a
    sharp blade? From which direction do I approach the IC? Should the lawn
    be mown already or is it advantageous to work with longer grass.

    Or is that confidential because you're preparing a patent application?
     
  16. Perhaps Jim can send me a lead to the precursors of the encapsulant,
    or just ask a chip mfr's process chemist or engineer how they clean up
    spills.

    If I were working with another experienced chemist, and they told me
    they were going to work with fuming nitric acid, I would say "when?"

    Commonly available "conc. nitric" is 70%, or about 15M. This is the
    stuff in the bottles with the red cap in lab storerooms, and it turns
    from water white and clear when new to the yellowish liquid with brown
    vapor above it in half filled bottles that you may have seen sometime
    in your past.

    Conc nitric is hazardous in a lot of ways.

    I sometimes use a hot mixture of conc. nitric acid acidified with
    sulfuric acid (9 HNO3 : 1 H2SO4) to clean glassware and am comfortable
    with my ability to handle that mixture. That mixture is such a
    powerful oxidizer that it will oxidize iodide to idoine, which will
    form purple vapor and needle crystals in the condenser above reflux,
    and can be trapped in the condensate. I dress, pay attention, and
    make sure a colleague knows what I am doing, change clothes, shower.

    Carelessness with conc. nitric can be dangerous, and an interesting
    page may be found at http://www.ilpi.com/safety/explosion.html

    However,

    Fuming nitric is an uglier beast. It is sometimes called 90% nitric.
    It is poison. Its vapors are poison. Its decomposition products are
    poison. It is dryer than distilled nitric acid. It is hazardous to
    add water to it. It is energetic. I have never needed to work with
    it.

    It is hypergolic with many materials. I have heard rumors that
    ordinary old flesh, wet red meat, will spontaineously catch fire on
    exposure to it. One page that mentions several combinations of
    hypergolic partners is http://www.permanent.com/t-mikesc.htm, though I
    don't know how exotically dry their "nitric acid" is. (Chemically,
    really, really dry nitric acid would be the nitrogen tetroxide of
    rocketry usage on the same page. Nitric acid dried by fractional
    distillation is the 70% conc. nitric azeotrope.)

    Usually, I think the MSDSes are written by attorneys to cover the
    corporations liability, and I make my students read the MSDS for water
    and benzaldehyde (the flavor of Maraschino cherries) to keep things in
    perspective. Many of the phrases in the MSDS of chemicals that
    chemists regard as routine and easy to use are presented in
    essentially the same way in the MSDS for fuming nitric. I teach in
    lab that this leveling of the report of hazard is an insideous danger
    that robs the readers of judgement. I am usually trying to move them
    away from a phobia of chemicals.

    I am not trying to make you comfortable ragarding fuming nitric acid.

    An MSDS for fuming nitric is online at
    http://www.sefsc.noaa.gov/HTMLdocs/NitricAcidFuming90.htm

    to quote selections:

    "
    Incompatibilities:
    A dangerously powerful oxidizing agent, fuming nitric acid is
    incompatible with most substances
    "

    "Incompatible with" in this context means, in part, "may be hypergolic
    at temperature, pressure, and concentration conditions found on the
    bench."
     
  17. Mac

    Mac Guest

    Sodium chloride is similar in that regard.
    I wasn't comfortable to begin with. I'm even less comfortable now.
    Heh. It's almost like anti-matter. ;-)

    Around 15 years ago I worked for EH&S as a student employee at a California
    University. Another student and I collected all of the hazardous chemical
    and radioactive waste from all the labs on campus, as well as all the
    biohazardous material from the health center. It's been long enough that I
    have forgotten pretty much all the details of hazardous substances. I
    don't work with any chemicals or radionuclides nowadays.

    The biohazard stuff we autoclaved and then threw away in the dumpster.
    This was the correct procedure, and complied with all applicable
    regulations.

    Also, we were allowed to store certain short-half-life radioactive waste,
    and discard it when it had decayed through enough half-lives. This was
    true only for waste not hazardous in some other way. For liquids, we just
    poured it down the drain once it decayed out. We did measure the pH and
    test for flammability first. Once again, this was all correct procedure
    and perfectly legal at the time. The storage facility had a lot of safety
    equipment, and was restricted to authorized personnel, obviously.

    It was a lot of fun. Probably my favorite part was driving around campus
    in the EH&S pickup truck with the radiation hazard sign displayed.

    Mac
     
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