I Have seen this problem and I have also read the responses from fellow
TechNet subscribers. To me the problem is not the size of the board or the
direction in which it travels through the wave solder machine. The problem
lays in the board itself. This bowing can be caused by a large thermal
gathering on the bottom side of the PCB due to a large concentration of
tracks, or even a ground plane. PCI connector's that I have had experience
with have given the same problems. The solution that was reached with the
process was the redesigning of the "barbs" in the center. The more common
PCI connector that I have seen does not have this "barb" Our warpage got so
bad at one stage that the center barb was pulls from the plastic Housing.
We sat down with AMP components and explained our situation and they
designed the part to suit our process. This was the only way that we could
eliminate this problem.


I Hope that this is of help to you.

Ger.

----------
> From: [log in to unmask]
> To: [log in to unmask]
> Subject: [TN] Warped boards at PCI connector?
> Date: 12 December 1998 02:22
>
> To technet
> I have this board that is 18 by 14 though hole and SMT. After reflow the
board
> looks good not warped. Once assembled and sent to wave the board warps,
only
> around the PCI connectors. It warps so bad I don't have any lead
protrusion. I
> have tried to run this board many ways fast slow and minimal preheat. I
still
> have this problem. Has anyone ran into this problem before? Is this
common
> around PCI connectors? I recall this happening once before many years
ago, I
> resolved it by tacking down the edge and middle of the connectors then
> masking. Is this the only fix? Any other suggestions
>
> Thanks in advance
> Angie
>
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