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> I'm not sure how they solder those SMT chips-I always thought they were done
> with wave soldering, not individual legs/contacts.
Surface mount isn't done with wave soldering. Wave soldering, by it's
nature involves a wave of solder (who'd 've guessed). There are three
major problems you run into with wave soldering:
1) the solder has a fairly high mass and as the wave passes under the
board, any component that is surface mounted would be likely be swept
away.
2) the solder is (obviously) very hot and transfers heat very readily.
This would easily cook small heat-sensitive components very quickly.
3) most important - and when you think about it - the most obvious -
the solder is under the influence of gravity. The solder sits in a
tank and is pumped over a barrier creating a wave. The boards are then
passed over the tank, through the peak of the wave where solder is
applied. This isn't a problem for through-hole mounted components
where the components are out of harms way and unable to move because
of the holes their mounted it, but guess what happens when mount (as
yet) unsoldered components on the surface of a board and then turn it
upside down into a wave of solder? :-) Glue can only do so much.
Look up "vapor phase reflow" on a search engine. It's a very ingeneous
technique really. No mechanical force is applied to the components,
it's possible to do both sides a board simultaneously (when SMC's are
glued to the underside) and it doesn't thermally jolt the components.
Matthias Jetleb
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Message is in Reply To:
 | | Re: SCARA *rocks*
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| (...) The webpage says "high speed PCB assembly, inspection, manipulation, and sorting." That to me suggests the manipulation of PCBs themselves, yet the video shows the robots doing something to locations ON the PCB (ie, where chips would be). (...) (23 years ago, 10-Apr-02, to lugnet.org.ca.rtltoronto)
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