CCD-world: Printed cct boards as CCD substrates?

[Chuck Gilman]

The following was posted to CCD-world:

I'm surprised no one has commented about the use of a "silicone-elastomer
adhesive" in this application.  I typically avoid these types of adhesives around
optics due to outgassing problems.

Chuck Gilman, Sr. Opto-mechanical Engineer
PRISM Consulting & Design, Inc.
8166 SW Durham Rd.
Tigard, OR 97224

(503) 968-6847

http://www.prism-inc.com

Jean-Luc Gach wrote:

> The following was posted to CCD-world:
>
> On Thu, 4 May 2000 C.J.S.Damerell at rl.ac.uk wrote:
>
> > The following was posted to CCD-world:
> >
> > I'm from the particle physics community, where our use of CCDs for tracking
> > detectors has until now used beryllium substrates, with copper/kapton flex
> > ccts bonded to them.
> >
> > For an R&D application, it would be more convenient for us to use standard
> > multi-layer printed cct boards, to which the CCD would be attached with a
> > silicone elastomer adhesive to avoid thermal stresses, and wire-bonded to
> > the top PCB layer. For what we are doing, we would need a 4-layer board.
> >
> > Are there problems associated with using PCBs on repeated cycling to reduced
> > temperature (down to say 100 K)? One could imagine delamination, breakage of
> > through-hole plated vias,  etc.
> >
> > For all I know, the use of these boards in low temperature applications may
> > be standard practice in the astronomy community. Any feedback would be most
> > welcome.
>
> Dear chris,
>
> we are experiencing here that kind of stuff. What i can say to you is that
> we have almost no problem with FR4 standard epoxy. Simply, at the
> beginning we had to pump each 15 days, this will reduce shortly to
> once each 2 month. Up to now, we used two layers boards, 0,8 millimeter
> thick in order to reduce the amount of epoxy inside the dewar. At the
> beginning we used film-protected PCBs, but we had to switch to PCBs
> without any protection (clear SnPb finished) due to the outgasing of this
> protective layer. This board operates at 170 K, we noticed no breakage of
> vias.
>
> cheers
>
> ------------------------------
> GACH Jean-Luc
> Observatoire de Marseille
> 2, Place Le Verrier
> 13248 MARSEILLE cedex 4
> FRANCE
>
> tel: (+33) 4 95 04 4119
> fax: (+33) 4 91 62 1190
>
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