HI Paul:

Are you sure the paste is what it says it is? It could be a mismarked
container of solder paste. Regardless of the type of flux all the paste must
reach soldering temperatures to coalesce and form a homogeneous mass of
solder to hold the lead. Check the profiles and the time above reflow. Check
to see if it is a particular component and what the plating is on the
component. If bismuth is around, the melting point of the alloy could be as
low as 98 degrees F. So check this out. Finally I would recommend getting
some microsections of the affected joints to fully analyze the metallurgy of
the metal and see what the physical joint looks like.

I hope this helps, good luck

Leo Lambert
EPTAC Corp
www.eptac.com
603-673-7822 ext 15

-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Black, Paul
Sent: Thursday, August 21, 2003 6:20 PM
To: [log in to unmask]
Subject: [TN] Soft solder


Has anyone ever run into this issue with solder paste? A year ago, we had
some boards with paste that was soft after reflow, to the point that in some
cases you could move the leads that were supposedly soldered. The paste
manufacturer came in and made some changes to our oven profile, saying that
the recipe was not allowing the solder to remain in the liquidus state long
enough. We thought the problem was solved but recently had a couple of
failed boards returned by a customer and found the problem again. This is a
no-clean 63/37 paste.

Thank you,
Paul Black
Manufacturing Engineer
Kronos

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