Steffen:
  Maybe you should provide mroe detailed information
such as board thickness,construction,laminate material
(FR-402 or FR-406, more for Tg), copper thickness,Is
copper balanced at two sides, bow &twist percentage,
minimim pitches of SMD etc.
  Your question is: Is there board material out there
in the industry that would warp less than others?
  Yes. Such as Panasonic R1705SX. But frankly speaking
this is not a solution. You can meeting IPC spec. by
using common FR-4 laminate. Look at design and process
control. Bow and twist is caused by mismatch of CTE of
resin/copper/glass by nature.(resin: 40-60 PPM/C;
Copper: 17 PPM/C; Glass: 5.5 PPM/C).
  Reduce colling at reflow seems not reasonable. A
good cooling is important than heating for warpage.

  Good luck

  Shirley Xiao


--- "Steffen, Don E" <[log in to unmask]> wrote:
> Technetters
>
> We are having a problem with board warpage. The
> board material is FR4. One
> board is double sided and the other is 4 layers.
> Appears that the double
> sided board warp more the four layer. We tried
> reducing the cooling portion
> of the reflow oven and this did not help. We are
> using paste that is a 63/37
> mixture so are using a normal thermal profile......
> The question is: Is
> there board material out there in the industry that
> would warp less than
> others? Are there other process variations that we
> can consider to lessen
> the warpage? This board is depaneled via a punch
> versus a router. We have
> reduce the size and number of tabs in order to
> reduce any induced
> microstrains shocks in the circuit. I would
> appreciate any guidelines if
> there are any out there.
>
> Thanks
>
> Donn Steffen
> Wk# (219)925-8887
> Fax# (219)925-8710
> Email: [log in to unmask]
>
>
##############################################################
> TechNet Mail List 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 web site
> (http://www.ipc.org/html/forum.htm) for additional
> information.
> If you need assistance - contact Keach Sasamori at
> [log in to unmask] or
> 847-509-9700 ext.5315
>
##############################################################
>


__________________________________________________
Do You Yahoo!?
Send instant messages & get email alerts with Yahoo! Messenger.
http://im.yahoo.com/

##############################################################
TechNet Mail List 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 web site (http://www.ipc.org/html/forum.htm) for additional
information.
If you need assistance - contact Keach Sasamori at [log in to unmask] or
847-509-9700 ext.5315
##############################################################