Power Cycling and Thermal Characterization

Fields of Research and Service

Lifetime testing of power semiconductors and modules including wide-bandgap devices for product development or qualification e.g. according to AQG324:

  • Generation of lifetime data incl. PCmin, PCsec
  • Statistical analysis and interpretation of measured lifetime data
  • Transient thermal characterization incl. thermal resistance Rth 
  • Lifetime modelling and prediction for die attach technologies and power modules
  • Long time experience on power cycling tests and analyzing of failure mechanisms
  • Consultancy on test planning, failure modes, and result interpretation


Special features

  • 7 independent test benches available
  • Up to 40 devices in one test run
  • Heating current from 0.1A up to 2000A
  • Heating voltage up to 35V
  • Heating and cooling power up to 20kW
  • Coolant temperatures from -60 ... +350°C possible
  • Thermal impedance Zth measurement during each cycle and all samples
  • Foster-Cauer network calculation and modelling Digital Power-Cycling Twin
  • On-line measurement and control system for each device under test (indirect measurement principle)
  • Individual setting of gate-voltage for every device under test
  • Automatic end-of-life-detection


Description of test principle

  • Active temperature cycling is an accelerated lifetime test for power electronic devices
  • Reliability characterization of new packaging concepts, materials, devices and technologies
  • The device is heated up via DC-current by semiconductor power losses
  • Intrinsic semiconductor characteristics act as a thermometer (virtual junction temperature)
  • After heating the samples are cooled down by the heat sink coolant
PCT test
© Fraunhofer IISB
PCT test
Bondwire liftoff
© Fraunhofer IISB
Bondwire liftoff
Silicon carbide device at high temperature and overcurrent
© Fraunhofer IISB
Silicon carbide device at high temperature and overcurrent

Devices for testing

  • IGBTs, mosfets, thyristors
  • Resistors
  • Schottky-diodes, pn-diodes
  • Si, SiC and GaN devices

Packaging for testing

  • Power modules with or without baseplate
  • PCB-Boards with discretes (TO-devices, D2Paks, etc.)
  • In-house test layouts and samples

Coolant strategies

  • Liquid and air cooling
  • Coolant temperatures from -60.. +350°C possible
  • Coolant pressure up to 8bar possible
  • Various coolants possible
  • Interaction of power cycling with temperature or pressure swings in coolant possible

Test procedures

  • Constant heating current (application near)
  • Constant temperature swing (academic by adjusting the gate voltage)
  • Constant heating power

Power modules
© Fraunhofer IISB
Power modules
Discrete on PCB
© Fraunhofer IISB
Discrete on PCB
Heat sink for 10 power modules
© Fraunhofer IISB
Heat sink for 10 power modules

Active Power Cycling Test


Thermal Characterization

[ PDF 0.55 MB ]