Feed-Thru VIA is a plated through hole (PTH) in a Printed Circuit Board that is used to provide electrical connection between a trace on one side of the board to a trace on the other side. Since it is not used to mount component leads, it is generally a small hole and pad diameter. The windows openings of feed-thru vias are always kept in standard boards, while tented by solder mask or resin in HDI boards.
Feed-Thru VIA