An RFID interposer has conductive material that includes an impedance matching structure. The impedance matching structure aids in matching impedance between a chip that is to be mounted to the interposer, and an antenna that the interposer is to be coupled to. The impedance matching structures may allow different chips, with slightly different electrical characteristics, to be impedance matched to the same antenna configuration, using the same type of interposer. The impedance matching structure may have any of a variety of configurations in the electrically conductive material of the interposer. The structure may be parts of the chip mounting bond pads, may be part of the conductive electrical connection between the chip bond pads and antenna bond pads, may be part of connections between the chip bond pads and the antenna bond pads, and/or may be only indirectly electrically coupled to the antenna bond pads (such as by capacitive coupling).