Richard,

Before you ask any other questions.....you have to rule out moisture by baking prior to hand soldering....SPECIALLY POLYIMIDE rigid-flex.

We just gone thru' a lengthy exercise to appreciate the importance of baking......our experience was also with hand soldering of polyimide rigid-flex.

IT is also important that you have a clear idea of how much baking is required....specially if the assy already has components on it.

Call me or write off-line if you want to discuss in detail.

Rush Patel
Accurate Engg Inc.
www.Accueng.com
818-768-3919 (w)
818-415-0030 (c) 

 

 


 

 

-----Original Message-----
From: Richard D. Krug <[log in to unmask]>
To: [log in to unmask]
Sent: Mon, Jul 26, 2010 7:59 am
Subject: [TN] Hand Soldering on Polyimide Rigid-Flex Assemblies


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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