Charles Barker asked

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Charles Barker
07/18/99 01:53 PM

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Subject:  Board baking

We are just getting into regular assembly of rigid-flex boards. What are
folks doing about removing the moisture absorbed in the flex?

Is anyone using nitrogen as a drying agent?  What are sources of
"dry-boxes" and such?

All you flex makers out there, what do you recommend?

TIA

Charlie Barker

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Charlie,

Its a Monday, so give us some time to get cranked up.  First, are you talking
old style or modern rigid-flex.
If you are using the old polyimide layers with acrylic adhesive, you can't do
enough good things to guarantee success.
If, on the other hand, you are using the all polyimide construction, the
survivability is greatly enhanced.

If your boards are pre-baked and sealed in moisture proof bags, you may be
able to process without a prebake.  Moisture in your facility and time "out of
bag" will determine the need and severity of your bake.  In cases like these,
I always try and get any "scrappers" from the PWB fab house for experiments.
2 hours at 105 C would be a good starting point if baking proves necessary.

Good luck,

Steve Mikell
Lead Ind. Eng.
Plant 13
SCI Systems

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