Scalable PCB cooling method for SiPM-ASIC PET detector modules

We are developing an MR-compatiblepositron emission tomography (PET) detector system comprising silicon photomultipliers (SiPMs), and application specific integrated circuits (ASICs) mounted in the same printed circuit board (PCB). Since the heat generated from the ASICs can affect the performance of temperature-dependent SiPMs, a scalable PCB cooling method for stable and uniform SiPM performance was designed, developed and investigated.To cool the SiPM surface within the PCB, a thermal layer is added below the SiPM layer, which is then connected to the bottom layer through thermal vias for efficient heat conduction. Then, either a “cooling plate” or “square tubes” is attached to the bottom layers of multiple detector modules. A proof-of-concept thermal experiment was performed to test the feasibility of the PCB cooling method for SiPM-ASIC PET detector modules, then a 3D transient heat transfer simulations was performed to analyze the temperature profile on the SiPM surface of the more realistic PCB. The thermal experiments were performed using a prototype PCB with a 6 W heater strip mimicking the ASICs and 15° water flowing through the cooling structure; the plate which has more contact to the PCB resulted in 18.0° average temperature and 0.8° maximum temperature difference across the 5 cm width SiPM layer, while square tubes showed slightly worse results of 18.7° and 1.3°, respectively. In realistic thermal simulations, the square tubes with thermal vias showed deviation from the experimental results with 21° average temperature and 6.5° maximum temperature difference. In addition, the thermal gradient was significantly worse without the thermal vias. Considering the compact and simple geometry of the square tubes compared to the plate configuration, the former with thermal vias are an attractive choice to cool the SiPM-ASIC PET detector modules; ASICs can further optimize the minor non-uniform SiPM performance using digital calibrations.