Just another possibility, is that the boards were warped after bare board
fabrication and then flattened in a post-fab process to come within spec.
Then, reflow relaxes the stresses in the boards and they return to their
original warped state.


Phil Dutton C.I.D.
Senior CAD Technician
IPC Certified Interconnect Designer

Tenix Defence Systems Pty Ltd
Systems Division - Adelaide
Second Avenue, Technology Park,
Mawson Lakes.  SOUTH AUSTRALIA  5095

================================
Phone   (08) 8300 4400 (reception)
Fax             (08) 8349 7420
email           [log in to unmask]
Internet Page   http//www.tenix.com
================================


-----Original Message-----
From: Malewicz Wesley [mailto:[log in to unmask]]
Sent: Tuesday, 14 November 2000 1:38
To: [log in to unmask]
Subject: [TN] Warp/Bow after reflow
Importance: High


Hi,

What are some of the contributors that would cause a .040 thick PCB in a 12
up panel, routed and scored, with components mounted on both sides, to
warp/bow after reflow.

Thanking you in advance for your suggestions.

Wes Malewicz
Printed Circuit Development Supervisor
Siemens Medical EM-PCS
email:  [log in to unmask]

-

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