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Good Semiconductor IC / Bad semiconductor IC?

Discussion in 'Electronic Basics' started by Talal Itani, Jun 26, 2007.

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  1. Talal Itani

    Talal Itani Guest

    When it comes to memory ICs, made by different manufacturers, can there be a
    low quality IC and a high quality IC.
     
  2. Guest


    Sure!

    You'll probably find that the absolute cheapest memory you can buy
    doesn't last as long or perform as well as the more expensive stuff.

    Back in school, some classmates and I went on a tour of NEC in
    Roseville. The tour guide (a former chemical engineering student)
    mentioned, in front of a neat laser that processed memory chips, that
    NEC's chips have redundant wires, so if one wire fails, the chip can
    still work. You might not find that feature on cheaper chips.
     
  3. Guest

    This is probably bad advice. One of the more important influences on
    the price of a chip is the volume being produced. More expensive chips
    remain available largely because it is cheaper to keep on using a more
    expensive chip than it is to redesign and re-layout a printed circuit
    board to take advantage of a chip that didn't go into production until
    after the board was designed.

    So the equation of higher price with better quality is rarely - if
    ever - valid.

    And NEC was spending money on putting in redundant connections because
    a significant proportion of the chips coming off the end of their
    production line didn't work, and some of those non-working chips could
    be made to work by using one of the "redundant" connections.

    Once they'd got their production process under better control, most of
    the chips produced would have worked first time, and they'd have
    stopped wasting money on the redundant connections (which never did a
    thing for the end-user anyway).
     
  4. JeffM

    JeffM Guest

    A company that wants to stay in business
    TESTS its products before shipping them.

    If an item does not meet all specifications at Final Test,
    that item is rejected. If a pattern of failure is detected,
    a cause in the manufacturing process is sought.

    Companies that consistantly don't meet their published specs
    are soon exposed and rapidly lose business.
     
  5. Guest



    Learn something new everyday... thanks!

    This NEC tour was back in '98 or so. Were redundant connections more
    commonly needed back then?

    Michael
     
  6. Rich Grise

    Rich Grise Guest

    Yes, yields were much lower, hence the redundant connections so they
    could bypass bad cells.

    But that's just to get their production yield up - it doesn't have
    anything to do with what the end user sees, i.e., the "redundant wires"
    aren't field-programmable. Like Bill said, when they get their production
    yield up, then the redundancies become superfluous.

    And yes, there can be better/poorer quality of chips, just like
    transistors have a range of paramaters, even in the same batch. This
    is where things like "beta: 50 min 300 max" come from.

    So, yeah, sure. :)

    Cheers!
    Rich
     
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