CCD-world: Printed cct boards as CCD substrates?

[dykaar at dalsa.com]

The following was posted to CCD-world:


I've done many experiments at low temperature (2-4 K) and there is a
special FR-4 type material called G-10 used for these applications. I
fabricated a set of superconducting devices at what was then NBS (now NIST)
in Boulder CO, including a G-10 device holder. The board used a
berillium-copper spring contact layer for easy device swapping. The
cryo-electronics group leader at NBS at the time was Clark Hamilton (U. of
Rochester grad).

Most failures that I experienced tended to happen during the pre-cool
cycle. By 70 K (LN2) all the excitement was over. At 100, or 170 K, I would
expect many fewer problems.

To wire bond to a PCB reliably, you need to Au plate the bond fingers.

Regards,

Doug Dykaar
Research Manager, and ex superconductivity jock
DALSA, Inc.
605 McMurray Road
Waterloo Ontario
Canada N2V 2E9
dykaar at dalsa.com
www.dalsa.com
519/886-6000x229
519/886-5767 fax






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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