Tiny carrier board for a 3 mm C-Series MICROFC-60035-SMT silicon photomultiplier by onsemi. PCB size is 6 x 6 mm. The solder pads for the SiPM are slightly bigger than they need to so that you can easily hand-solder everything.
On the front side there is only the sensor itself and the two connections are on the back. This ensures good optical contact and light-tight sealing.
To connect the sensor, solder wires to the anode A and cathode C pads of the PCB. These are connected straight to the respective pads on the SiPM.