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January 2007

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Subject:
From:
Royce Taylor <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Royce Taylor <[log in to unmask]>
Date:
Mon, 15 Jan 2007 14:03:46 -0500
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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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