FAILURE RATE MEASUREMENT ON SILICON DIODES REVERSE POLARIZED AT HIGH TEMPERATURE

This paper calculates the failure rate on reversed polarized silicon diodes with the aim to justify, experimentally, the rules of the European Space Agency (ESA) which are referred to the component life's extension, the reliability increase and the end of life performance enhancement, by using oversized devices (derating rules). In order to verify the derating rules, 80 silicon diodes are used, which are reverse polarized in a high temperature environment. The diodes are divided in 4 groups of 20 diodes, applying a different voltage to each group, in order to relate the failure rate to the applied derating rule. The experiment described in this paper is developed using a temperature accelerated test to check the leakage current in reverse polarization (HTRB - High Temperature Reverse Bias), with the purpose of obtaining results applying an acceleration factor in order to reduce the test duration. By using a thermal model of the whole system and the equations that describe the reverse polarized diode behaviour, it is possible to stress the 80 diodes up to very high temperature avoiding the runaway effect. Finally, the failure rate is calculated and a revision of the derating rules are proposed by using the experimental result obtained.