SBS - Silicon Detector - JLab12

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SBS - Silicon Detector

Hardware Projects > SBS

The INFN Roma silicon detectors will work in front of the magnet of the SBS spectrometer [Fig. 1] , giving the first tracking of each particle. The silicon detectors have a custom design [Fig. 2] developed in order to maximize the active area obtainable using a silicon wafer with 150 mm (6") of diameter, available from Hamamatsu Photonics foundry. There are 5 detectors with a thickness of 320 µm, a strip pitch of 50 µm  for a total of 2070 channels for each detector. A couple of detectors will form the X plane  and a second couple will form the Y plane. In order to connect each detector to the front-end electronics, PCBs (Printed Circuit Boards) with six layers [Fig. 3]  were developed. The first layer (top layer) has a ground plane and the circuitry for reverse bias. The 4 inner layers have the tracks for signal and the last layers (bottom layer) provides the cradle in which the silicon detector will be glued. The connection between the silicon detector and PCB tracks will be done by an ultrasonic wirebonding machine using a 18 µm Al wire. A second stage of connections, between the PCB and the Read Out electronics, will be performed by a flexible Kapton connector.   Signal read out will be performed by APV25 boards, using custom backplanes that fit the small dimension of the detector [Fig. 4]. A single backplane configures and reads four APV25 boards at the same time using a standard HDMI cable.

At the end a complete detector will  be equipped with 5 backplanes and 20 APV25 boards [Fig. 5]. Because of the need of containing the size of detector, the PCB will be equipped with two layers of backplanes, one for each side of the detector and with one backplane on the third side in addition. The entire detector-PCB assembly will be done in the INFN Roma clean room Class 10000. The assembly will be performed in two stages: the first one is the gluing of the detector on the PCB, the second stage is the ultrasonic wire-bonding of the detector Al strips with the PCB tracks. For this purpose two custom mechanical apparatuses were made [Figs 6-7]. All the operations have to be done at a fixed temperature of 21°C and a relative humidity of 50%, to avoid accidental electrostatic discharge during assembly operations and during the storage of the detectors.

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