Hello,
I have a PCA that hand solders 6 connector pins to an 4 layer PCB 
assembly.
The finish on the PCB is Lead Free HASL (SN100CL) and the solder used to 
hand solder the pins is SAC305.  The hand soldering is performed as a 
secondary assembly operation after reflow.
What happens to some of the assemblies, but not all of them, is that the 
solder will wick straight up the pin, thereby not allowing a Solder joint. 
 The pin can be pulled right out of the hole, revealing a PTH with no 
inner barrel.
Completely wiped out as if it was never there in the first place.  This 
phenomenon is not present on every PCB or every pin of the same connector. 
 The PCB's are part of a multi-board panel.

As far as I know the PCB started out with a barrel, but I cannot rely on 
this being the case as I do not believe the technician checks 100% of the 
PTH's prior to inserting the pin. 

Am I looking at excessive heat causing complete Copper Dissolution of the 
PTH barrel? 
or
A PCB that may not have a barrel in every hole, part of the PCB 
fabrication process?
or
Any other suggestion as to which direction to head would be appreciated.

Thanks in advance.
 

Tom Burek, CID+



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