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 x 60.4 mm, 16 read out ICs, each serving 24 x 160 pixel unit cells, a module controller chip (MCC), an optical transceiver and the local signal interconnection and power distribution busses. Figure 1 shows a prototype of such a module with additional test pads on both sides. The outer dimensions of the final module will be 21.4 mm x 67.8 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 dies are then attached by flip-chip assembly to the sensor diodes and the local busses. This thin film technology has been described in [1] and is under further development at Fraunhofer-IZM in Berlin, Focus of this paper is the description of the first results of such MCM-D-type modules.