Vacuum quality evaluation for uncooled micro bolometer thermal imager sensors

This paper presents an innovative and effective method of measuring the internal vacuum quality of uncooled micro bolometer thermal imager sensors where the bolometer sensor elements themselves are used for vacuum measurement. A feasible thermal calculation model using an extended Fourier's Law is presented which is integrated in thermal FEM simulations. Experimental results correlating with FEM simulations prove the feasibility of this method. A measuring range to pressures as low as 5 x 10(-3) mbar was achieved that fully covers the needed range where the internal package pressure is leading to performance losses of the IRFPA. The vacuum quality evaluation method supported by a developed temperature compensation method is showing a high repetitive accuracy with a remaining mean failure of 0.2%. Without the need to integrate additional pressure sensors this method reduces costs and chip area and it is fast and highly accurate. Therefore, it can be used for stationary test systems as well as in mobile infrared camera systems. (C) 2014 Elsevier Ltd. All rights reserved.