How to reduce the microphonic effect in pyroelectric detectors?

摘要

All pyroelectric crystals are inherently piezoelectric. Therefore, an unwanted signal is produced if a pyroelectric detector is excited mechanically. This behaviour is called microphonic effect or, sometimes, vibration responsivity. Based on the analytical and numerical description of the piezoelectric response of a pyroelectric detector a novel chip assembly has been developed to reduce the microphonic effect. Using a special chip carrier, the deformation of the pyroelectric chip is controlled and the microphony is reduced significantly. The chip carrier consists of a base plate with a central column surrounded by four symmetrically arranged columns. The reduction of the microphony depends on the thickness of the electrodes, the elastic modulus of the adhesive, by which the pyroelectric chip is bonded onto the chip carrier, and the position of the outer columns. The vibration interference voltage is minimal in the majority of practical applications if the outer columns are placed near the middle between the centre column and the rim. Typically, the reduction of the vibration responsivity is more than one order of magnitude. It can reach two orders of magnitude if the alignment between chip and chip carrier is perfect..