Pyroelectric infrared detector with flip-printed circuit boards (PCBs) architecture for efficient thermal compensation

Abstract This paper reports a flip-printed circuit boards (PCBs) architecture for effective thermal compensation in the fabrication and packaging of a pyroelectric infrared (IR) detector. To enhance the stability of the IR detector and minimize the impact of ambient temperature variations, a dual-element configuration is adopted here. The top PCB consists of the active pyroelectric sensing element, which is fabricated using lithium tantalate (LiTaO 3 ) with a carbon black absorber layer, which achieves approximately 90% absorption in the mid-IR range. The bottom PCB carries a thermal compensation element, purposefully shielded from incident IR radiation to respond only to ambient temperature variations. Both the PCBs are clubbed in a flip-PCBs configuration, physically separated by a nitrogen-filled gap, which works as an isolation layer with high thermal resistance, results in minimizing thermal and optical crosstalk between the two elements. A circular PCB, compatible with a TO-39 header package, along with the charge to voltage conversion circuit, which includes a junction field-effect transistor (JFET) and high-value resistors, with the detector assembly. The fabricated IR detector demonstrates a mean peak-to-peak voltage (V pp ) of ∼2.17 V logged at 30 °C. Testing under varying ambient temperature surroundings from 30 °C to 50 °C exhibits a mean V pp variation from 2.17 to 2.30 V, confirming the effectiveness of the thermal compensation scheme in comparison to the change in output voltage from 1.13 to 2.55 V in case of uncompensated detector.