Development of a Four-Side Buttable X-Ray Detection Module With Low Dead Area Using the UFXC32k Chips With TSVs

Nowadays, single photon counting pixel hybrid detectors are becoming increasingly popular in high-energy physics, X-ray detectors for synchrotron applications, and medical imaging. Readout chips for these detectors usually have the area of a few square centimeters and are designed to be abutted on three sides. However, many applications require large-area detectors without dead areas. The through-silicon vias (TSVs) aim to minimize the dead area and in that way to enable development of four-side buttable large-area detectors. AGH, Krakow, and IZM, Berlin, have undertaken a common effort to apply TSV (via last) technology to the readout integrated circuit called UFXC32k containing a matrix of 128 x 256 pixels, with a pixel pitch of 75 mu m and a total area of 2 cm(2). The TSVs were applied to the 87 I/O pads located at the bottom of UFXC32k IC. A TSV diameter of 20 mu m was chosen while the wafers were thinned to 100 mu m. The redistribution layer and the array of pads for solder bumping were distributed at the bottom side of the chips. Two UFXC32k chips with TSVs were attached to a single, 320-m-thick silicon sensor and finally, the chip detector modules were attached to low-temperature co-fired ceramic boards. The 2 x 2 cm(2) plug-in detector modules were successfully built and tested.