Flexprint PCBs

[Olaf Iwert]

Flexprint circuits :

Here at ESO we are using flexRIGID PCB's since about 4 years at cryogenic 
temperatures inside the dewars, being in every night use at the telescope.
So far the failure rate is 0 %.
We have used them mainly with ZIF sockets for large scientific CCDs, or have 
attached them directly to the connectors of CCDs.

Please note that according to our experience flexible PCBs in contrast to 
flexRIGID PCBs present a lot of problems in the handling/soldering and their
reliability, as on the part where pads are soldered tension is introduced 
which leads to wharping of the board. While cooling down or mechanically 
loading the flexboards typically the solder joints will crack.

FlexRIGID PCB's are therefore enforeced and rigid in those sections where 
soldering takes place, avoid additoinal connectors beteween flexible and 
rigid parts and are industry standard (however at normal operating 
temperatures) for consumer electronics such as SLR Cameras and laptops. 

We have used up to 6 layers at temperatures down to at leasst -100 deg C.

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  Olaf Iwert                        E-mail :               oiwert at eso.org  
  European Southern Observatory     Phone & Voice Mail :   +49-89-320-06-353  
  Optical Detector Lab              FAX :                  +49-89-320-23-62
  Karl-Schwarzschild-Str 2
  85748 Garching
  GERMANY                         
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