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December 2007

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From:
Guy Ramsey <[log in to unmask]>
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Date:
Thu, 13 Dec 2007 16:11:34 -0500
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I have seen what the Hinkle guy described in the referenced thread. The
paste brick remains intact but something in the paste fails to encourage
wetting of the individual spheres to each other and the component. I think
it looks more like a lump of silver caviar. 

The condition is usually profile related. I have seen it induced by letting
the paste dry prior to reflow. Most pastes have such long life now days that
you only see it in a Designed Experiment. Perhaps new Pb-Free pastes are
more susceptible. 

I have seen one instance attributable to solder paste failure. Soldering to
a machined socket pin mounted on a very thick board with a validated profile
results were poor (A lot of inspector whining). Noting that the paste was
near the end of our permitted open life, we switched to a new jar and got
good results.

I suspect that even this was, to some extent profile related. We were
operating on the long edge of the maximum "soak" time in a straight ramp to
reflow because of the nature of the application. 
 
 

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Phillip Bavaro
Sent: Thursday, December 13, 2007 6:06 AM
To: [log in to unmask]
Subject: [TN] "Grape-ing"

My solderpaste supplier is educating me regarding a defect called
"grape-ing".

Anyone care to shed a little light on this soldering defect?

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