IPC-FA-251 recommends 121C for 30-60 minutes for 1 and 2 layer circuits.
A rigid flex can take easily an hour per layer depending on the
construction. The more layers the longer the time. 140C is above the
rating of acrylic adhesives and could possibly damage the bond. Regards
Steve Kelly

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Rick Thompson
Sent: Tuesday, June 04, 2002 3:50 PM
To: [log in to unmask]
Subject: [TN] Rigid-Flex Bake Requirements??

We're assembling a fairly complex rigid-flex PCB (10 layer, sub-4mil
line/space, polyimide/FR4 sandwich) and have had some issues with
bake-out to remove moisture.  The boards we received were individually
sealed with dessicant pack and humidity indicator card in each.  Our
assumption was that they did not need baking since they were sealed and
had been fabricated only a couple of days prior.  The board vendor is
telling us they need 2 hours at 250 F bakeout, regardless of packaging.

My question is this:  Can anyone offer any guideline, insight, etc into
the baking that may be required for this type of rigid-flex PCB?  Are
there any industry standards that may cover this?

Thanks in advance,


Rick Thompson
Ventura Electronics Assembly
2655 Park Center Dr.
Simi Valley, CA 93065

+1 (805) 584-9858   x-304  voice
+1 (805) 584-1529 fax
[log in to unmask]

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