Hi all:

There have a big difference on Vertical fill of solder between IPC-A-610/J-STD-001 E version and F version.  In the F version said that Vertical fill of solder for component with less than 14 leads is 75%, and Vertical fill of solder for component with 14 leads or more is 50% for class 2.  But in some case some holes connect to ground plane in many layers, they are very difficult to get 75% vertical fill during wave soldering or hand soldering. 
My question are:
How to improve the process to increase vertical fill from 50% to 75% in through holes which connect to many layers?
Why IPC do this change? Why IPC define 14 leads, but not 8 leads or 16 leads?

 
Best regards
Deng