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Subject:	Hand Soldering on Polyimide Rigid-Flex Assemblies
From:	"Richard D. Krug" <[log in to unmask]>
Reply To:	TechNet E-Mail Forum <[log in to unmask]>, Richard D. Krug
Date:	Mon, 26 Jul 2010 10:59:01 -0400
Content-Type:	text/plain
Parts/Attachments:	text/plain (31 lines)

We assemble limited quantities of polyimide rigid-flex assemblies.  Due to moisture absorption by the polyimide substrate, we perform a bake prior to mass soldering processes;  either reflow, wave or single point selective soldering.
We have recently found some vias near hand soldered locations on the rigid portion of the substrate that are open.  Cross sections reveal the opens are at the interface between the rigid substrate and the flexible substrate.  We have not specified a bake prior to hand soldering components on the rigid portion of the rigid-flex assembly.  We are using Sn63Pb37 solder.

Is the open caused by TCE differences between the rigid and flexible substrates or by moisture turning to steam?
Is it necessary to bake polyimide rigid-flex substrates prior to hand soldering?
Is this inherent in all polyimide rigid-flex substrates or do we have a weakly bonded substrate?

Dick Krug, CSMTPE
SMT Process Engineer
Sparton Corporation
30167 Power Line Road
Brooksville, FL  34602-8299
p (352) 540-4012  (Internal Ext. 2012)
[log in to unmask]


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