Hi Royce:
	         Have you tried two smaller dots of adhesive instead of
one larger one?  The same amount of glue would be dispensed but along
the width of the part.
	Regards,
	Ramon
 

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Royce Taylor
Sent: Monday, January 15, 2007 2:04 PM
To: [log in to unmask]
Subject: [TN] tombstoning of 0508 ceramic capacitors

I have a question for the "Adhesive Dispense"  OR the "0508 chip"
experts out in Technet land.

We at times struggle with 0508 capacitors tombstoning (yes, 0508 not
0805). We do run Nitrogen and turning it off helps at times but there
are many times we need to run nitrogen for other reasons. Most times we
try to dispense a dot of adhesive (Loctite 3609) but we are having
occasional issues with the adhesive getting into the solderpaste, the
gap between the pads measures ONLY 0.020" so it is difficult to prevent
this from happening.  Does anyone out there run into the same issues??
Any thoughts?? We run a Camalot Gemini and a Fuji GL dispenser and use a
25 GA needle. Also we use Indium SMQ92J No Clean solderpaste so I don't
know if this paste is contributing to the tombstoning.

A re-layout of the boards is not an option. We have tried both a
"straight ramp"  and a "ramp-soak-ramp" profile with little or no
difference.

Thanks for your thoughts and advice

Royce
*************************************************
Royce Taylor
Raytheon
350 Lowell St.
Andover, MA  01810
(978) 470-7431

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