Implantable medical devices (IMDS) having RF
telemetry capabilities for uplink transmitting
patient data and downlink receiving
programming commands to and from an external
programmer having an improved
RF module configured to occupy small spaces within the IMD housing to further effect the
miniaturization thereof. An
RF module formed of an
RF module substrate and at least one IC
chip and discrete components has a volume and dimensions that are optimally minimized to reduce its volumetric form factor.
Miniaturization techniques include: (1) integrating inductors into one or more IC chips mounted to the RF module substrate; (2) mounting each IC
chip into a well of the RF module substrate and using short bonding wires to electrically connect bond pads of the RF module substrate and the IC
chip; and (3)
surface mounting discrete capacitors over IC chips to reduce space taken up on the RF module substrate. The integrated inductors are preferably fabricated as planar
spiral wound conductive traces formed of high conductive metals to reduce trace height and width while maintaining
low resistance, thereby reducing parasitic capacitances between adjacent trace side walls and with a
ground plane of the IC chip. The spiral winding preferably is square or rectangular, but having truncated turns to eliminate 90° angles that cause point-to-point parasitic capacitances. The planar
spiral wound conductive traces are further preferably suspended over the
ground plane of the RF module substrate by micromachining underlying substrate material away to thereby reduce parasitic capacitances.