Don,

   The number of pins isn't the limiting factor for double side reflow. I
believe more in practical test due to several different parameters involved
( pad position, contact area, force distribution, surface tension, time
above liquidous, peak temperature, conveyor vibration, etc... ). Take some
scraped boards and pass trough the oven with the components facing down and
realize yourself what component can or can't be on the second reflow side. I
did this experiment with a VGA card with 1 QFP 208 pins and 4 QFP 100 pins
and no components fall off ...
   Good luck

Jorge Dourado de Santana
Maintenance / Process Engr
Microtec - Brazil



> -----Original Message-----
> From: Hurst, Joe [SMTP:[log in to unmask]]
> Sent: 17 de Setembro de 1999 12:51
> To:   [log in to unmask]
> Subject:      Re: [TN] Bottom Side reflow.
>
> Don
>         A number that was seen on this forum at one time was 30 grams of
> component mass per 1 square inch of total pad area.  I have used this on
> some oscillators and it was OK.
>
> Joe Hurst, CET
> PWB Designer
> Computing Devices Canada
> A General Dynamics Company
> [log in to unmask]
> 613-596-7816
>
>
> -----Original Message-----
> From: Steffen, Don E [mailto:[log in to unmask]]
> Sent: Friday, September 17, 1999 11:35 AM
> To: [log in to unmask]
> Subject: [TN] Bottom Side reflow.
>
>
> Technetters
>
> We are doing a double side reflow. What is the formula to determine the
> maximum component mass double side reflow so the components will not fall
> off during reflow. I realize it is also necessary to know the amount a
> surface tension also necessary. Is there a point, such as 14 pin or less
> IC
> that I can safely process through the reflow. What is the experience of
> the
> industry? I appreciate any responses you can provide!
>
> Donn E Steffen
> Senior Quality Engineer
> VDO Control Systems
> Auburn, IN 46706
> Phone (219)925-8887
> Fax (219)925-8710
> Email: [log in to unmask]
>
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