I only remember seeing it back in the early days of water soluble
pastes. In that case the flux was consumed before the board got into
reflow and the oxides prevented the paste from coallesing. Never knew it
had a formal term associated with it. 

 


Tom  

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Guy Ramsey
Sent: Thursday, December 13, 2007 4:12 PM
To: [log in to unmask]
Subject: Re: [TN] "Grape-ing"

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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