The Sensor Module

The ExcaliburRX Sensor Module

The ExcaliburRX sensor module consists of a single monolithic silicon sensor of 500um thickness consisting of 2048x512 pixels, each 55um square. 16 Medipix3RX ASICs are flip-chip bonded to the back of the sensor using SnPb solder bumps at 55um pitch.

Exploded CAD drawing of the ExcaliburRX module

The heat generated by the ASICs is dissipated by a molybdenum cold finger attached to a closed loop liquid cooling system. The communication with the Medipix3RX chips is achieved using a PCB with two 300-way connectors. The ASIC I/O is connected to the PCB with aluminium wirebonds. The image to the left shows an exploded CAD drawing of the ExcaliburRX module. Rightmost is the silicon sensor, and from right to left, the ASICs, the cold finger and the PCB.

Microscope image of an ExcaliburRX sensor module

The image to the right shows a microscope image of the corner of an ExcaliburRX sensor module.

Uppermost is the sensor, dull grey in colour, in the bottom corner of which can be seen the two wirebonds cascading down to the leftmost bond pad of the green PCB. These wirebonds carry the high voltage bias, typically 120V, to the sensor. Underneath the sensor can be seen the wirebond extender pads of the Medipix3RX ASIC. Approximately 1/3 of the chip edge can be seen with the corresponding wirebonds cascading over the molybdenum coldfinger, sandwiched between the ASICs and the PCB, connecting to the landing pads on the PCB.

The thickness of the silicon sensor, 500um, was chosen to best cover the detector operating range of 6 - 20 keV. At 20 keV an efficiency of 40% is obtained.