A medical device for the diagnosis or treatment of tissue in a body and method for fabricating the same are provided. The device includes an elongate, tubular, deformable shaft comprising a proximal end and a distal end. The device also includes an electronic subassembly (54) disposed within the shaft and a conductor (76, 78) coupled to and extending from the electronic subassembly. The electronic subassembly includes a flexible substrate (72) and an electronic device (74). The flexible substrate comprises an interior side (84) and an exterior side (86) opposite the interior side. The flexible substrate also defines a first conductive area (92, 94). The electronic device is mounted on the interior side of the flexible substrate, is coupled to the first conductive area, and is at least partially enclosed within the flexible substrate.
