Subject: | |
From: | |
Reply To: | TechNet E-Mail Forum. |
Date: | Thu, 25 Apr 2002 13:48:45 -0400 |
Content-Type: | text/plain |
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IPC 600 page 56 section 2.11 on flatness, but your assembly line/ process
really indicates what's acceptable. Use your least robust machine (the one
that cannot tolerate bow/twist) to determine your REAL requirement. Each
manufacturer (pick/place) recommends a bow/twist max in mm or in. It also
depends on PWB thickness - a 0.030" telecon PWB is much more flimsy than a
0.125" high voltage PWB. In line conveyors hate excessive bow or twist,
especially.
PS. PWBs can be flattened with a soak at warm temps under a weight.
Mike
-----Original Message-----
From: K HERK [mailto:[log in to unmask]]
Sent: Thursday, April 25, 2002 11:11 AM
To: [log in to unmask]
Subject: [TN] BOW/WARP
Is there a chart for PCB bowing ?
I have a typical value of 0.007"/1" bow, but a
customer wants to know the
bow for the specific case of 1.6mm FR-4. Are there
different "ranges" of
bowing that a PCB is specified at ?
Also, how does temperature affect bowing ? The
customer says that bowing
occurs during solder reflow where the temperatures are
a few 100 degrees
Celsius.
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