I do two hours at 125 C, and this seems to work fine (the oven is at 125
when I put boards in). If that hasn't worked, it's usually been because of
lack of cleanliness of the copper surface prior to coverfilm lamination, and
through working with my fab shops, we've been able to improve situations
like that.
I'm also using the LF material for the coverfilm. The base is all
adhesiveless (and I've never been happier - yields are up dramatically with
it), but we still have that acrylic for the coverfilm. Some on this list
have said they've had luck with other types of adhesive (epoxies and the
like), but I've never played with them.
Hey, it's my first response to a question on Technet! I've been asking for
the past year, but I've never added anything myself.
Matt
Matthew Sanders
PCB/Metal Procurement Engineer, Trimble Navigation Ltd.
[log in to unmask]
Phone: (408) 481-7817
Fax: (408) 481-8590
-----Original Message-----
From: Steve R Mikell [mailto:[log in to unmask]]
Sent: Monday, July 19, 1999 2:14 PM
To: [log in to unmask]
Subject: Re: [TN] Rigid-Flex Board baking
Charles Barker asked
*********************************************************************
Charles Barker
07/18/99 01:53 PM
To: [log in to unmask]
cc:
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
************************************************************************
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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