There are several potential root-causes of board warpage:
1. Incomplete cure of epoxy resin
2. Asymmetrical stackup of board layers
3. Unbalanced circuitry layers
4. Excessive bowing during board fabrication
                Non-parallel lamination fixturing/press platens
                Inadequate post-lamination stress relief
5. Absorption of moisture before assembly
6. Excessive temperatures during assembly
7. Rapid heating or rapid cooling during assembly
8. Bad fixturing during wave soldering

-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Malewicz Wesley
Sent: Monday, November 13, 2000 10:08 AM
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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