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Subject:
From:
Jared Robertson <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, [log in to unmask]
Date:
Thu, 10 May 2018 19:48:24 +0000
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Thermal profile-add a soak before melting point



-----Original Message-----

From: TechNet [mailto:[log in to unmask]] On Behalf Of SALA GABRIELE

Sent: Thursday, May 10, 2018 1:30 PM

To: [log in to unmask]

Subject: [EXT] [TN] R: [TN] 0201 tombstoning



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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