Depending on the type of adhesive process (thermal set or PSA tape) they
could be applied at different stages. Typically they're done in panel form
using external tooling holes for registration. If however, PSA tape is being
used to apply then they could be applied in pc form and aligned by eye. As
far as the size of clearance in the stiffeners normally they're slightly
larger than the underlying pad that you plan on wicking solder to. If you're
wanting a S/S flex without pads on the side your applying the stiffener to,
then you could go smaller. It's best to contact the potential supplier and
seeing what they recommend that will best fit their processes and get you
what you need.
Dan S.

----- Original Message ----- 
From: "Harris Dy" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Friday, November 20, 2009 10:05 AM
Subject: [TN] Stiffener on Flex Circuit


Hi guys,

I am not that familiar with Flex manufacturing so I would appreciate if you
can share your knowledge and help me understand the process of adding FR4
stiffeners to Flex circuit.

1. At what point of the process is FR4 stiffener normally added to the Flex?

2. If there are holes that needs to be drilled on the stiffeners to match
the Flex holes, is it drilled larger (due to misregistration?)? If so, by
how much bigger?

3. I remember FR4 stiffeners were drilled and routed together with adhesive.
How is it registered then to the Flex? It's not being attached individually
or manually right?

I would appreciate if you can explain in greater detail.

Thanks for your help.
HDY




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