Temperature–humidity–bias testing on insulated‐gate bipolartransistor modules – failure modes and acceleration due to high voltage

Abstract

The temperature-humidity-bias (THB) test is the standard for accelerated stress testing with respect to corrosion and other humidity driven degradation mechanisms. Usually, 1000 h tests at 85°C and 85% relative humidity are used to predict up to 25 years of operation. The bias is usually limited to 80 V in order to fulfil the respective standards. Nevertheless, THB tests on 1700 V insulated-gate bipolar transistor (IGBT)-modules have shown that higher bias is a more severe test condition. The failure analysis confirmed Cu-and Ag-dendrites and corrosion of the aluminium (Al)-chip-metallisation as the relevant failure mechanisms. To determine the acceleration factor due to voltage, 1200 V IGBT modules were tested in THB at 780 V (65% of V CES) and 1080 V (90% of V CES). A characteristic degradation consisting of three phases has been identified. The second phase seems to be determined by Al corrosion and an acceleration factor of about two has been estimated from 780 to 1080 V. Within the third phase, the devices stabilised probably due to localised self-heating. Thus, this degradation mechanism is kind of self-limiting, but the higher leakage also increases the risk of thermal runaway especially when biased close to the rated collector-emitter voltage.

Exploring the Causes of Power-Converter Failure in Wind Turbines based on Comprehensive Field-Data and Damage Analysis

“…• insulation degradation in the DC-link busbars/laminates, but above all of the DC terminals and busbars of power modules, which leads to short-circuit failure and with that often to a damage of modules connected to the same DC link • a reduction of the blocking capability of the power semiconductors due to electrochemical migration and aluminum corrosion, which was demonstrated by [43] under the combined influence of 85% relative humidity, a temperature of 85 • C and voltages above 65% of the nominal blocking voltage, and for which the occurrence even at lower humidity, temperature and voltage-stress levels is subject of further investigations…”

Enhancement of Reliability in Condition Monitoring Techniques in Wind Turbines

“…These wires can become detached (lifted-off) during power cycling due to temperature stresses. From early failure when Bond wire lift-off one bond wire is lifted off to almost 65% of the wires lifted off, the IGBT is still able to function, albeit with a significantly increased risk of total failure [12]. Voltage drop across the bond wires increases as bond wires come adrift because of the increased load current passing through the remaining wires.…”

“…As an alternative to a physical sensor, several methods have been presented in the literature to estimate junction temperature, , by monitoring certain electrical parameters. These methods are either based on direct measurement or data-driven methods as summarized in Fig 2 [10][11][12]. The direct method is not widely used due to the high implementation costs and the requirement to access the inside of the module.…”

Sensitivity analysis of switching electrical parameters of semiconductor devices for wind turbine converters

“…Previous studies have shown that the on-state collectoremitter voltage V CE,on is a good failure indicator of BWLO [9]. However, this parameter is affected by temperature changes and, hence, it can be cause by both BWLO and SF.…”

“…These can be detected with different methods before a complete damage to the component has occurred. Temperature swings are the cause of a not uniform expansion of the different materials of IGBT's and the resulting shear stresses potentially lead to fatigue [9]. The bonded area is where the bond wire foot is connected to the metal chip.…”