There is a formula that uses the weight of the component and the surface
area of the leads to predict whether or not the component will stay on the
secondary side of the board without adhesive. Search the technet archives. I
think Steve posted it in 97 or 98.
I found it to be reliable. We did encounter a SMT relay that would not stay
on the board. We tried adhesive, but it stretched during reflow. The result
was disturbed joints. I don't recall what we did to resolve the problem.
Hope you don't need to try.

 Guy Ramsey
American Competitiveness Institute
Senior Lab Technician / Instructor
610 362-1200 ext 107


-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Lefebvre, Scott
Sent: Wednesday, January 24, 2001 6:33 PM
To: [log in to unmask]
Subject: [TN] SMT components on BOT SIDE


I need to place 16 QFP168 with 16mil pitch leads on the bottom side.
I will am going to reflow both top and bottom.

I feel that there should be enough surface tension to hold the parts onto
the bottom, but
I thought I would get some confirmation on this.

Thanks

Scott

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