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Looking for somewhat flexible metallized film

Discussion in 'Electronic Design' started by Joerg, Nov 5, 2013.

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  1. Joerg

    Joerg Guest

    Folks,

    Here is what we want to do. Stretch a film over some dielectric material
    which has varying properties. Then a water- or air-filled balloon is
    pressed onto that, and this presses the film against the dielectric. The
    more pressure, the more dielectric is touched. Width of dielectric is a
    few inches, pressure doesn't matter (by hand). There is an electrode on
    the other side of the dielectric.

    So the plastic must be somewhat flexible for up to 5% of sag and I guess
    that rules out Mylar and Kapton. Also, the metallization should be
    non-oxidizing which usually means gold or similar. The surface roughness
    must be as low as possible, low single-digit nanometers.

    Does anyone know a supplier for such film that sells in quantities less
    than truckloads?
     
  2. Jamie M

    Jamie M Guest

    Hi,

    Aluminized mylar is pretty common, not sure if it will stretch
    5% though!

    Ebay has quite a bit:
    http://www.ebay.ca/sch/i.html?_nkw=mylar+rolls

    cheers,
    Jamie
     
  3. Joerg

    Joerg Guest

    Mylar is tough to stretch. We could probably do it somehow but aluminum
    metallization can develop a fine non-conductive layer quickly and has a
    pretty bad surface roughness.
     
  4. Phil Hobbs

    Phil Hobbs Guest

    You're going to want to use conductive ink for that, not a metal film.
    The metal will crack into a zillion tiny islands. Good-grade carbon ink
    will stick to low surface energy substrates such as teflon or
    polyethylene, and is tough enough to take a hard crease without cracking.

    Cheers

    Phil Hobbs

    --
    Dr Philip C D Hobbs
    Principal Consultant
    ElectroOptical Innovations LLC
    Optics, Electro-optics, Photonics, Analog Electronics

    160 North State Road #203
    Briarcliff Manor NY 10510

    hobbs at electrooptical dot net
    http://electrooptical.net
     
  5. RobertMacy

    RobertMacy Guest


    That single annometer roughness is pretty tough to meet. But have you
    looked at the food industry? Like Lay's potato chips come in a pretty thin
    metallized film.
     
  6. Joerg

    Joerg Guest

    Some does, a little. But they mostly have the same problem as party
    balloons: Another non-conductive coating to make them shiny or have a
    "wet" look. It's all about shelf appeal. Buy me, buy me, be hungry,
    salivate, be hungry, now, must buy, must buy.
     
  7. Joerg

    Joerg Guest

    Good idea. Do you know where one could buy such material ready-to-go off
    the shelf? Price is not important unless it's really outlandish, because
    this is only for a materials test station.

    I've looked at carbon nanotube material which could almost get there in
    terms of surface roughness. But it only existed on glossy print, not on
    a shelf with a price tag on there.
     
  8. RobertMacy

    RobertMacy Guest

    Isn't metallized mylar used to prevent the helium from escaping, not for
    the looks?
     
  9. Does the film have to be metallic or just conductive ? A finnish company
    called Canatu manufactures carbon nanotube coated films, which might be
    suitable. Their main substrate is PET, but they might have something
    more stretchable, too.
     
  10. Joerg

    Joerg Guest


    No idea but definitely also for looks. There were shiny golden ones and
    silver ones.
     
  11. Joerg

    Joerg Guest


    Only conductive and that doesn't even have to be very good. A few
    hundred ohms corner to corner would be ok. I also does not matter
    whether it's translucent or not. But surface roughness is a key
    parameter. If that is more than very few nanometers the whole testing
    idea isn't going to work.
    Aha, now we are getting somewhere. Thanks!

    http://www.canatu.com/products/
     
  12. < 10nm is < 0.5 microinch (not sure if you're talking RMS or AA, but
    it's very smooth in any case). So you're looking for optical grade
    film.

    Maybe ITO or gold on PET would work, but this paper indicates that
    your 5% may not be achievable without cracking:

    http://ieeexplore.ieee.org/xpl/logi...re.ieee.org/xpls/abs_all.jsp?arnumber=5936492

    Could you use gold leaf bonded to a flexible optical-grade film?
     
  13. PET has a Young's modulus of around 2.5 GPa, and elongation at yield
    of > 15%.
     
  14. They're really concerned about keeping the chips airtight to get long
    and consistent shelf life. I did some work for a company that makes
    the packaging materials years ago.
     
  15. Joerg

    Joerg Guest

    If we can't get 5% we could back off to maybe 3% or less but the real
    challenge seems to be the surface roughness spec for the metallization.
    It has to be in the low single-digit nanometers. We can do that in-house
    but it would be a major effort that we are trying to avoid for a one-off
    test station.
     
  16. Joerg

    Joerg Guest

    I am sure they do that as well. But when talking to a packaging designer
    I was amazed how much effort goes into the glitz factor. IIRC he was a
    very highly paid guy and had the freedom only real artists are afforded.
     
  17. Phil Hobbs

    Phil Hobbs Guest

    Yup. Gas diffusion in metal is many orders of magnitude slower than in
    plastic.

    Cheers

    Phil Hobbs

    --
    Dr Philip C D Hobbs
    Principal Consultant
    ElectroOptical Innovations LLC
    Optics, Electro-optics, Photonics, Analog Electronics

    160 North State Road #203
    Briarcliff Manor NY 10510

    hobbs at electrooptical dot net
    http://electrooptical.net
     
  18. Jasen Betts

    Jasen Betts Guest

    you're looking for a metal that can deforem 5% elastically ?
    if the matal can;t handle the deformation it'll come off the film.

    I've seen metalised PE used in wine bladders.
    I don't know it if can handle 5% though.
     
  19. Joerg

    Joerg Guest

    We can go lower than 5% if needed. The main problem is surface roughness
    which needs to be very few nanometers. We've got a process in-house that
    can do this but it can't make such large films and it is very labor
    intense to do that just for a test station.
     
  20. Hi Joerg, nanometers sounds hard! (But I really don't know.) Is this thing going to live in vacuum? For optics I always figured the scratch and digs are in the few micron range. (You've got to be able to see them after all.)

    I think a monolayer of water on your surface will be in the nanometer range.

    George H.
     
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