Failure mechanisms of microbolometer thermal imager sensors using chip-scale packaging

• Published in: Microelectronics and reliability Vol. 55; no. 9-10; pp. 1901 - 1905
• Main Authors: Elßner, Michael, Vogt, Holger
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01-08-2015
• Subjects: Degradation; Failure mechanisms; Hermetic packaging; Infrared imager; Micro bolometer; Reliability; Vacuum quality; Degradation; Hermetic packaging; Infrared imager; Micro bolometer; Reliability; Vacuum quality; Failure mechanisms
• ISSN: 0026-2714; 1872-941X
• DOI: 10.1016/j.microrel.2015.07.040

This paper analyzes relevant failure mechanisms for microbolometer thermal imager sensors that are assembled with a small size and low cost chip scale package. The analyses focus on device specific elements like the bolometer sensor structures, the longtime stability of the sensor and its performance, and the stability of the hermetic chip scale package. Executed reliability tests showed a high reliability of the sensor and the package without hard failures. The package survived harsh environmental accelerated stress tests and showed only a slight reduction of the shear strength through void formation and small cracks within the lead frame that could be verified through FEM simulations. The stress on the bolometers is investigated by thermomechanical FEM simulations. Executed reliability tests showed no enlargement in the number of defect pixel. The sensor performance showed a longtime drift and temperature dependence through outgassing processes inside the package leading to a significant performance reduction. Thus this effect is investigated more closely and possible countermeasures are proposed.
•Analysis of failure mechanisms of infrared sensors, through simulation and reliability tests•Focus on the performance degradation and reliability of chip scale package•The main failure mechanism is the rising pressure inside the hermetic vacuum package.•Outgassing processes are leading to significant performance degradation.•The package showed smaller cracks, void formation and a reduction of mechanical strength.