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Ethylene Oxide cleaning of printed circuit boards

Discussion in 'Electronic Design' started by René, Mar 15, 2005.

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  1. René

    René Guest

    Hi All,

    Has anybody experience with Ethylene Oxide cleaning of a PCB
    containing SMD parts and connectors? Is a coating necessary? Will
    connectors stand up (over time) after cleaning?

    We are building a PCB that will be incorporated in a larger assembly
    for medical application - hence the EtO cleaning...

    TIA!
     
  2. EtO, nice stuff....
    http://www.nsc.org/library/chemical/Ethylen0.htm

    martin

    "An eye for an eye makes the whole world blind"
    Gandhi
     
  3. René

    René Guest

    OK - so I will not inhale.....:)

    Anyway - we have to supply the PCB's - our customer does the dangerous
    stuff. All we must do is to make the product survive the EtO.
     
  4. Chris Carlen

    Chris Carlen Guest

    Yes. I came close to needing that stuff for a synthesis once, but found
    an alternative approach that spared the need for this.

    There is something screwy with the practice of gassing items with EtO
    for medical sterilization when it has such low TLV/PELs and is a "de
    minimis" carcinogen.

    Something like a PCB with components would certainly retain trace
    amounts of the stuff, unless baked out afterward in vacuum.

    Is a vacuum bakeout part of the normal procedure for EtO sterilizations?




    Good day!



    --
    _______________________________________________________________________
    Christopher R. Carlen
    Principal Laser/Optical Technologist
    Sandia National Laboratories CA USA

    NOTE, delete texts: "RemoveThis" and "BOGUS" from email address to reply.
     
  5. Isn't that what US president's claim?


    martin

    "An eye for an eye makes the whole world blind"
    Gandhi
     
  6. Al

    Al Guest

    Remember, just because it is sterile doesn't mean that it is not
    contaminated.

    Al
     
  7. Mark Jones

    Mark Jones Guest

    Ha! that's what all Americans claim. :)
     
  8. Joerg

    Joerg Guest

    Hello René,

    EtO is very corrosive. I have dealt with a lot of electronics that got
    sterilized that way. There isn't much else you can do with electronics.
    Radiation, for example, will destroy most of the stuff. Same with
    processes that require high temperatures.

    We had potted and non-potted designs. However, it was all disposable so
    there were no repeat sterilization although we did have to do those to
    validate margins etc.

    Also, keep in mind that you will have to do other stuff as well, such as
    passing the biocompatibility test. That starts with lots and lots of
    paperwork. Keep in close contact to the Regulatory/QA folks of your client.

    And never, never, touch anything before the outgassing phase is
    completed. But people who work under a proper QA system normally won't
    let you anyway.

    Regards, Joerg
     
  9. René

    René Guest

    Given the fact that the PCB will be disposable and will contain fine
    pitch tracks and several connectors (micromatch, slotted 1/10"
    headers), what is advisable relative to coatings, connector pin
    materials (gold, tin etc.)Thanks for answering!
     
  10. Joerg

    Joerg Guest

    Hello René,
    Our circuit boards were regular issue, no fancy coatings. But with
    respect to surface coating and connectors I would study a bit,
    especially if you are facing multiple EtO cycles. This may be a start:

    http://www.devicelink.com/mddi/archive/04/06/009.html

    For connectors, gold plating is popular. But always get the
    manufacturers blessing first. Here is a start:

    http://www.fischerconnectors.co.uk/products/connectors.htm

    Most major connector manufacturers and especially the ones catering to
    the medical device industry (such as LEMO S.A.) can guide you. As I said
    before, a very important aspect is that you receive sufficient data for
    bio burden. Without such data a connector may be useless no matter how
    good it is. Med is a heavily regulated industry, and it should be. So,
    the QA folks are going to want to know what's in your design from a
    chemistry point of view.

    Regards, Joerg
     
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