base material resin that covers the interface between the exposed edge of an innerlayer pad and through-hole plating
NOTE 1 The resin transfer is usually caused by the drilling operation and removed during the desmear process. The term ‘resin smear’ or ‘smearing’ are synonymous.
NOTE 2 The aspect of smear can be mistaken for interconnect defect, or vice versa. Smear is the presence of resin, whereas interconnect defect is an adhesive separation of copper plating.
[adapted from IPC-T-50M]