Hi Ryan,
Approach them the way you would a 0603 DOE. The biggest thing I saw that
keeps tombstoning to a minimum is to keep a large area gap between the
pads, and also try to balance the trace widths that come into the pads.
I use a .006 thk stencil with rectangular pads and 1:1 aperature openings.
Also, do not use HASL finish.
I stay away from glue.
I could go on, but lets see what everyone else says.
Kerry McMullen
Principal New Product Mfg. Engineer
LTX Corporation
50 Rosemont Road
Westwood, MA 02090-2306
(T) 781-467-5468
"Ryan, Will" <[log in to unmask]>
Sent by: TechNet <[log in to unmask]>
05/10/2006 08:34 AM
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[TN] 0402 Experience and Pitfalls
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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