Thank you very much Guy and Kevin for your responses. Guy's threshold is slightly lower (approx 25 gm/inch^2) as compared to Kevin's (30gm/inch^2), but both are in the same ballpark.
Regards,
Amol
-----Original Message-----
From: Guy Ramsey [mailto:[log in to unmask]]
Sent: Tuesday, February 26, 2008 4:06 PM
To: 'TechNet E-Mail Forum'; Kane, Amol (349)
Subject: RE: [TN] Component Suitability for Second Side Reflow
Here is the rule of thumb from the EMPF Boot Camp: Four grams per square
centimeter of solderable surface area on the device or board, which ever is
less. You need a pretty good scale and take careful measurements to use the
formula. It is a conservative rule of thumb. I have pushed it and still had
good process results. It is good for SnPb solder.
We have done a lot of Pb-Free double side assembly, at NPI-Proof of Concept
quantities. Most new designs are well within the ratio above and are fine.
SMT style RF connectors will fall off. Relays like the Coto 9852-05-00 and
NEC UB2-5NJ relays may stay on but our process resulted in some disturbed
solder joints. They must have been darn close to falling off.
Good luck
Guy
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Kane, Amol (349)
Sent: Tuesday, February 26, 2008 3:17 PM
To: [log in to unmask]
Subject: [TN] Component Suitability for Second Side Reflow
Dear Technetters,
Where would I be able to find guidance on the suitability of a particular
component for second side reflow?. Obviously, the weight of the component on
the bottom side has to be <= by the solder surface tension force to prevent
the component from falling off the board during reflow. Is there literature
available for calculation of the maximum wt of a component that can be
safely put on a pad, knowing the pad geometry, solder volume and lead
surface area?
Sounds simple enough....until you go to do the actual calculation.
Any pointers would be greatly appreciated.
Thanks,
Amol
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