A tiled array of hybrid pixel detectors for X-ray imaging

A prototype multichip hybrid was developed, based on tiling together eight Medipix2 readout chips onto a single silicon sensor with a sensitive area of 28×56 mm² for a total of about 0.5 Mpixels. A main difficulty of this approach is in the high density of interconnections needed to read out all the circuits in such a tiled array. The amount of connectivity between the readout circuits is drastically reduced by the use of a high-speed serial protocol, allowing the use of low-voltage differential signaling at frequencies above 100 MHz. To mount the multichip hybrid, we are using a new printed-wire-board technology called multilayer sequential buildup with staggered micro-vias, which allows accommodation of the 128 wire bonds per chip on a ten-layer printed wire board, with smallest feature size of 60 μm linewidth and 100 μm pitch.