Hi,

- kind of terminal finishing ?
- terminal oxidized ? (data code)
- try to load PCB in reflow oven by rotating 180°  (front-rear : rear to front)

- Electrostatic Charge on chip ?

The metal EMI could cause thermal unbalance around chips

Have a good luck

Gabriele

-----Messaggio originale-----
Da: TechNet [mailto:[log in to unmask]] Per conto di Graham Collins
Inviato: giovedì 10 maggio 2018 21:20
A: [log in to unmask]
Oggetto: [TN] 0201 tombstoning

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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