First MCM-D modules for the b-physics layer of the ATLAS pixel detector

The innermost layer (b-physics layer) of the ATLAS Pixel Detector will consist of modules based on MCM-D technology. Such a module consists of a sensor tile with an active area of 16.4 mm×60.4 mm, 16 read out ICs, each serving 24x 160 pixel unit cells, a module controller chip (MCC), an optical transceiver and the local signal interconnection and power distribution busses. We show a prototype of such a module with additional test pads on both sides. The outer dimensions of the final module will be 21.4 mmx67.8 mm. The extremely high wiring density, which is necessary to interconnect the read-out chips, was achieved using a thin film copper/photo-BCB process on the pixel array. The bumping of the read out chips was done using electroplating PbSn. All dice are then attached by flip-chip assembly to the sensor diodes and the local busses. The focus of this paper is the description of the first results of such MCM-D-type modules.