You may want to consider pallets to hold the board flat while it heats up
over the way and as it cools down afterwards. The best solution is to fix it
in the design, but if your already stuck with a design a stiffener or pallet
will do the trick. Give me a buzz if you need stiffener or pallet info.
Jim 972-494-1911
-----Original Message-----
From: Vascukynas, Brian <[log in to unmask]>
To: [log in to unmask] <[log in to unmask]>
Date: Friday, January 08, 1999 3:09 PM
Subject: [TN] PWB Warping


>Hello,
>
>We have been experiencing warping on certain PWB's from a specific
>supplier.
>I am curious on what the causes could be.
>
>In each instance, the PWB design layout was checked and found to be
>well balanced. Also our SMT Reflow Profiles were looked at for each PWB
>and found
>to be typical. The boards sometimes exhibit a slight warp right out of
>the MFG
>packaging and will warp out of spec on the first run.
>
>1. We looked at dwell times, ramp up rate, actual temp, speed of PWB
>going thru the
>oven and all appears to be typical per each individual case. Is there
>anything else we
>could be checking for?
>
>2. Is moisture absorption a concern - could it cause warping ?
>
>3. Currently we do not bake PWB's prior to SMT Reflow - Is this
>something we should
>consider.
>
>Thanks in advance.
>
>Brian V.
>
>################################################################
>TechNet E-Mail Forum provided as a free service by IPC using LISTSERV 1.8c
>################################################################
>To subscribe/unsubscribe, send a message to [log in to unmask] with following
text in the body:
>To subscribe:   SUBSCRIBE TechNet <your full name>
>To unsubscribe:   SIGNOFF TechNet
>################################################################
>Please visit IPC's web site (http://www.ipc.org) "On-Line Services" section
for additional information.
>For technical support contact Hugo Scaramuzza at [log in to unmask] or
847-509-9700 ext.312
>################################################################
>

################################################################
TechNet E-Mail Forum provided as a free service by IPC using LISTSERV 1.8c
################################################################
To subscribe/unsubscribe, send a message to [log in to unmask] with following text in the body:
To subscribe:   SUBSCRIBE TechNet <your full name>
To unsubscribe:   SIGNOFF TechNet 
################################################################
Please visit IPC's web site (http://www.ipc.org) "On-Line Services" section for additional information.
For technical support contact Hugo Scaramuzza at [log in to unmask] or 847-509-9700 ext.312
################################################################