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| Date: | Thu, 10 May 2018 16:20:04 -0300 |
| Content-Type: | text/plain |
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Hey Technet
I've got a problem with 0201s capacitors tombstoning. No resistors,
just a few of the caps. This is a lead-free build, no nitrogen, and
there is an EMI shield installed on top prior to reflow (solid shield,
no openings). Thermal layout looks OK, no glaring copper imbalances.
The boards were inspected prior to placing the EMI shield, placement
accuracy was good, paste accuracy was good. Some of the parts are
adjacent the EMI shield side wall, but not all.
The only idea I've got to try is to reduce the size of my paste
aperture. It is 13.5x11.2 mils, on a 4 mil coated stencil, I'm
pondering going down to 10x10 mils.
We don't see this with other 0201 placements, but this is the only one
we are building that has an EMI shield on top.
Any other ideas?
--
Graham Collins
Senior Process Engineer
Sunsel Systems
(902) 444-7867
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