Users of early SMT solder pastes will remember something similar, the paste
would not reflow. Actually it had and probably your pipe too! 
The solder powder had melted but like M&Ms (Smarties in UK), the solder had
melted inside the coating on each sphere. 
In those days the powder was more oxidized than now, and fluxes were not as
effective or persistent as now. So with the soak profiles required by the
inefficient reflow ovens of the time (in a brilliant marketing stroke the
oven guys used to say the soak was for the paste to activate) the powder
would actually be processed into hollow ceramic spheres with metal fillers. 


Regards

Mike Fenner 
Bonding Services & Products
T: +44 [0] 1865 522 663 E: [log in to unmask]

 

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Blair Hogg
Sent: Thursday, March 29, 2012 6:20 PM
To: [log in to unmask]
Subject: [TN] NTC- unmeltable solder

The recent discussions on rework issues reminded me of a while back where I
needed to repair a leaky water pipe in my home. Took a chunk of the ceiling
out, got out the plumbers torch, drained the pipes and started to heat. No
matter what I did to the joint that was leaking I could not get anything to
melt. Had to cut the pipe on either side of the elbow joint and patch in a
new section. Even afer I took it out I could not get it apart. Not sure what
happened to the solder but something changed it to make it unmeltable. 

Blair



______________________________________________________________________
This email has been scanned by the Symantec Email Security.cloud service.
For more information please contact helpdesk at x2960 or [log in to unmask] 
______________________________________________________________________