Panel plating after PTH process is to plate 5-8 um extra copper to the surface of PTH copper. This is to protect PTH copper from damage during the next following up process.

WELLER：
Copper thickness on through plated hole: 25um(min). Which is the same standard of IPC class 3.
Or else, the poor thickness copper on the through plated hole will take risk of open circuit after high temperature of assembly process.