What the attached material called & where I can get it

Discussion in 'General Electronics Chat' started by aamirali, Apr 4, 2012.

  1. aamirali

    Thread Starter Member

    Feb 2, 2012
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    In LCD, there is a black material to cover/hide IC below. What's this material called & where I can get it.
    I have attached jpeg image for reference
     
  2. chrisw1990

    Active Member

    Oct 22, 2011
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  3. jimkeith

    Active Member

    Oct 26, 2011
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    This is special stuff that does not contaminate the silicon die.
    I do not know were to get it, but can offer alternative:
    RTV compound (silicone rubber)
     
  4. aamirali

    Thread Starter Member

    Feb 2, 2012
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    We use programmable IC, MCu. Now I need to hide the IC. What's the best solution for it.
    Is potting compound is fine?????
     
  5. chrisw1990

    Active Member

    Oct 22, 2011
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    Potting Compound Explained Its used to protect peoples electronics from a) damage and b) theft! my mate uses it on his circuits which are used in automotive applications.. protects them from tampering and any additional rubbish that might be hanging around.

    if you're unsure, buy a little tube or something, and put it on blank pcb.. then test it, or apply it, its exactly the same as conformal coating, a clear laquer that lasts about 10years!
     
  6. SgtWookie

    Expert

    Jul 17, 2007
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    Note that most RTV silicon emits ascetic acid while curing, and the acid is corrosive. If you do decide to use RTV, you need to use a type that is specifically recommended for electronics.
     
  7. ErnieM

    AAC Fanatic!

    Apr 24, 2011
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    You are looking at glob top ic's. These parts started as bare silicon dies that get glued down (there are both conductive and non conductive epoxies for that), then the IC pads are wire bonded from the chip to the PC board. The board needs special wire bondable gold on those pads which is not as uncommon as you think.

    Once the part is wired this way it is given a shot of a hard cure epoxy to protect everything. From the uniform nature of these devices there is a machine dedicated to dropping this shot of glue.

    The advantage is a lower per-piece cost after incurring a huge set up cost so it is best for high volume devices, such as generic alphanumeric LCD displays where I often see them, but not uncommon in game devices where total units is high but profit margins are slim.

    I've used such materials in the past. I don't have any part numbers handy but could get then if you are still interested.

    Note doing this by hand is difficult, and our company managed to scrap an entire year's worth of production by using the wrong material. Most of this had already hit the customer and caused huge problems. I got on board at the end of this mess and made the call to scrap all the present material and begin building again with something else.

    Since RTV is pliable (the R stands for RUBBER) yo could press on it and disturb the wirebonds underneath. That is a no-no. You want a hard epoxy shell.
     
  8. gerty

    AAC Fanatic!

    Aug 30, 2007
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  9. ErnieM

    AAC Fanatic!

    Apr 24, 2011
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    OK, so it seems you have a packaged device and you want to obscure which exact part it is to make it more difficult to reverse engineer.

    The simplest way it to just lightly sand the top to remove the markings. Next up is a little paint, but that might be chipped off to reveal markings, especially if they are laser burned on and not printed.

    A potting epoxy would also work. Even if you obscure the device outline an xray would reveal that. Many companies have these for inspection, and any friedly dentist possess all the equipment required

    RTV can be worked off pretty easily.
     
  10. t06afre

    AAC Fanatic!

    May 11, 2009
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    You can protect the code inside micro-controller. So other can not read it out. In adition you can mask the chip by taking away the ID. From what I see. The blob is some kind of epoxy that is also safe for the electronics.
    For a small series product. Using code protection and chip masking. Should be more than good
     
  11. Stuntman

    Active Member

    Mar 28, 2011
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    Two things:
    A. SgtWookie is right on. I conducted tests on a change in material for sealing compounds for potting fixtures. This sealant came in direct contact on the board solder joints/leads.

    B. Some of these RTV products take longer to dry (app. 1 week) than others (24hrs), exacerbating this issue. Also, during the cure time, these products CAN be conductive.

    All said, I have found the 100% silicone sealants (can be bought in big tubes for sealing windows and doors) drys faster and the product I have personally tested (from GE), have not been conductive during the curing stages. Also, this limited/visibly eliminated the corrosion issue.

    As for something like siliconized acrylic... bad news. I've seen this stuff stay wet for days in 100+ degree weather, allowing crosstalk between leads during this time, and pretty severe oxidation of the contacts.

    Something to try (that I haven't delved into myself) may be a cheap epoxy (if size permits). This would be much more tamper-proof and may not have any of these corrosion/conduction issues.
     
  12. mcgyvr

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    Oct 15, 2009
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