Wicking describes unwanted capillary flow in two places. In assembly, solder wicks up component leads or down open vias in pads, robbing the joint and leaving it starved or voided. In fabrication, wicking is copper or plating chemistry penetrating along glass fibers from a drilled hole wall; it is measured in microsections and limited by IPC class because it shortens the spacing to neighbouring conductors and can seed CAF.
Solder is wicking down the open vias in the thermal pad, plug them or tent them from the bottom.
Also heard as
- solder wicking
- copper wicking
Related terms
Via-in-pad
Via placed directly in a component pad, filled and plated over so solder cannot drain down it.
Tenting
Covering a via with soldermask or film so its hole is sealed over instead of left open.
CAF
Conductive anodic filament: copper growth along glass fibers inside a board that shorts holes under voltage.
Cold joint
Solder joint that never got hot enough to flow and wet properly, leaving a dull, grainy and unreliable bond.