Hi Will
We made the leap a few years ago and it turned out to be just a short
hop. Not a big deal.
Pad design - we tended toward the smaller end of the recommendations.
I believe I had a thread going on TechNet on that topic a few years
ago.
Aperture - we used the same practice as we do for 0603s. We run RMA
paste and just use a 1:1 to the pad for the discretes. Tombstoning is
not an issue when we run in air in the oven, but does occur when we run
in nitrogen.
We use a GSM-1 for p&p, had to get a smaller nozzle for the 0402s.
Other than that, with the camera setup we have the machine rejects a
fair bit more 0402s than it does 0603s so attrition needs to be
watched.
I would NOT use 0402s on a glue/wave process. Wouldn't even consider
it. If they have to go on the bottom side I'd go with an aperture
pallet to shield them. Getting a glue dot that small that doesn't get
onto the pads would be very difficult.
I'd recommend getting some dummy parts and giving a try before
committing to a design, that way you won't be too worried about risk.
- Graham Collins
L-3 Communications Electronic Systems
Halifax, Nova Scotia
>>> [log in to unmask] 05/10/06 09:34AM >>>
Dear fellow TechNeters,
For many of you this is old technology, and you most likely are
focusing
on 0201 implementation or Pb-Free.
However for our team, we are about to make the giant leap from 0603
components to 0402s!
Thus, you guys out there at the cutting edge will have a boat load of
experience to share with regard to the implementation issues and
pitfalls with the introduction of 0402s, and I am hoping that you will
be able to give me the 'skinny'!
Obviously stuff like aperture design, stencil design, nozzle
selection,
placement capability, cam speed, AOI, rework, inspection
magnification,
etc. will all be affected.
However, what I am looking for are details that would help our
transition sail through, coupled with some unanticipated issues you
were
faced with and how they were overcome, e.g. tombstoning, soldering,
placement accuracy, etc. which were not apparent when placing 0603s.
Have you guys had any reliability issues with 0402s?
Also, do you guys use 0402s on the solder-solder side, with a glue and
wave process? Is this a no no?
Would really appreciate if you would be willing to share your
experience.
Best regards,
Will
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