In this example of solder wicking it is clearly caused by the printed board surface finish. The solderability of the gold is poor due to a plating problem and the paste has not wetted the pads during reflow. Close examination of the leads shows a slightly bulbous appearance on the leads. The solder has tended to wet the lead rather than the pad. Often in this situation the printing process is blamed for not printing paste successfully on to the pad.

The solderability of the printed board should be tested using a wetting balance.