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protection against vibration

Discussion in 'Electronic Design' started by veeresh, Jun 4, 2007.

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  1. veeresh

    veeresh Guest

    Hi,
    On one of my PCBs i'm using a heavy IC. It is a 70pin gull wing
    package. And, the problem is that the pins are breaking near the IC
    package. I don't want to use RTV, as it's difficult to remove. What
    best I can do to protect this against vibration tests?

    Thanks and Regards,
    Veeresh
     
  2. If the board is close to a panel of some sort them you could use that
    thermally conductive matting stuff between the PCB and the panel that
    also acts as a vibration absorber.

    Got a link to the actual package?

    Vibration tests are done for a reason, if it's failing then you have
    trouble. Do you just want to a) pass the test (as you seem be to
    implying), or b) do you want to pass the test and make your product
    more reliable?

    Dave.
     
  3. Can you link to a package drawing?


    Best regards,
    Spehro Pefhany
     
  4. MooseFET

    MooseFET Guest

    The breaking is often caused by the PCB flexing. During the vibration
    test, the vibration may hit a resonant frequency for the PCB. Adding
    another attachment point ot the PCB can help.

    Placing a rubber foot such that the PCB bumps into it if it deflects,
    will often help to damp a resonance.

    Changing details of the mounting will often help. Basically, you want
    to push the resonant frequency up and increase losses. It matters
    less how you do this than that it is done.
     
  5. Tim Wescott

    Tim Wescott Guest

    Or going to a thicker PC, or attaching stiffeners to the PC -- One of
    these will be the least expensive for you, but it depends on your situation.

    --

    Tim Wescott
    Wescott Design Services
    http://www.wescottdesign.com

    Posting from Google? See http://cfaj.freeshell.org/google/

    Do you need to implement control loops in software?
    "Applied Control Theory for Embedded Systems" gives you just what it says.
    See details at http://www.wescottdesign.com/actfes/actfes.html
     
  6. Tim Wescott

    Tim Wescott Guest

    I think I would want to make my product better, and pass vibration tests
    as a consequence, rather than being focused on passing the tests and
    damn what happens to my product in the field.

    --

    Tim Wescott
    Wescott Design Services
    http://www.wescottdesign.com

    Posting from Google? See http://cfaj.freeshell.org/google/

    Do you need to implement control loops in software?
    "Applied Control Theory for Embedded Systems" gives you just what it says.
    See details at http://www.wescottdesign.com/actfes/actfes.html
     
  7. Marra

    Marra Guest

    Rubber mounts on the pcb should reduce it.
     
  8. John Larkin

    John Larkin Guest

    As others have mentioned, it's flex resonances of the board itself
    that are probably the problem. Boards will blur at resonance, and
    literally throw parts off. The board should be stiffened, damped, or
    vibration isolated.

    John
     
  9. veeresh

    veeresh Guest

    Hello Sir,
    Thanks for the kind response from all of you.

    It has passed the tests some times. But when tested for many times,
    the pins break. I want to make it rugged... exactly option (b) :)
    The PCB is housed in an enclosure with screws at every 5cm w.r.t each
    other. Please check the link below for package diagram.

    http://www.ddc-web.com/FileLibrary/Default.aspx?type=Datasheets&div=MIL-STD-1553


    please consider the data sheet of BU-61580(second one ). I'm using the
    gull wing package - page 44 of 46. I took this perticularly to save
    the space.
    Now, I've kept a sil pad below the device, super glue on four corners,
    and RTV on pins. Is this fine, or something better can be done?

    Regards,
    Veeresh
     
  10. veeresh

    veeresh Guest

    I think I can fill upto 1 inch to reach the top plate, using sil pad.
    ~Veeresh
     
  11. veeresh

    veeresh Guest

    Hello Sir,
    What can we use for this vibration isolation? Is it some kind of
    washers, and studs that we use to fix the board in the box?
    ~veeresh
     
  12. veeresh

    veeresh Guest

    please consider the link below
    http://www.ddc-web.com/
    FileLibrary/Default.aspx?type=Datasheets&div=MIL-STD-1553
     
  13. veeresh

    veeresh Guest

    please consider the link below
    http://www.ddc-web.com/
    FileLibrary/Default.aspx?type=Datasheets&div=MIL-STD-1553
     
  14. veeresh

    veeresh Guest


    please consider the link below. Sorry for inconvinience.
    http://www.ddc-web.com
    /FileLibrary/Default.aspx?type=Datasheets&div=MIL-STD-1553
     
  15. veeresh

    veeresh Guest


    please consider the link below. Sorry for inconvinience.
    http://www.ddc-web.com
    /FileLibrary/Default.aspx?type=Datasheets&div=MIL-STD-1553
     
  16. veeresh

    veeresh Guest

    US$ 1000 :)
     
  17. veeresh

    veeresh Guest

    actually they suggested putting glue on the pins, and all. But once
    glue is put, the maintainance will be diffiult

    Why don't you tell us
     
  18. John Larkin

    John Larkin Guest


    Google "vibration isolator". The classic vendor for this stuff is at
    lord.com.

    John
     
  19. Have you considered asking the manufacturer? Why don't you tell us
    how much it costs so Joerg can have a heart attack? Last part I used
    from that company was in the high four digits (USD).


    Best regards,
    Spehro Pefhany
     
  20. That's a lot of Sil-Pad dude, and it ain't cheap.
    There are much easier ways to solve your problem.

    Dave.
     
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