CCD-world: Printed cct boards as CCD substrates?

[Tom Droege]

The following was posted to CCD-world:

A historical note.  Back in ancient days, G-10 was the standard material.
Then along came safety programs and FR-4 appeared because G-10 could burn.
FR-4 was soon found by the high energy physics community to be bad news in
a vacuum.   I think you owe them the fact that you can still get G-10.
They insist that it keeps being made.  FR, I believe, stands for "Fire
Retardant".   It is a reformulation of the epoxy to include a fire
retardant, which, you can imagine, comes out in a vacuum.   So if you are
going to use printed circuit material in a vacuum, be sure you find someone
who knows how to specify the material.  I am too old to know for sure
anymore.  

Tom Droege

At 09:05 AM 5/4/00 -0400, you wrote:
>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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