Power semiconductor modules operate at the intersection of high electrical load, concentrated heat and complex material interfaces. IGBT, MOSFET and silicon-carbide modules may combine semiconductor dies, metallization, bond wires, solder or sintered layers, ceramic substrates, baseplates, encapsulants and external terminals. Repeated thermal and environmental stress can affect any of these interfaces.
An effective reliability program separates ambient environmental stress from internally generated power cycling, then combines them only when the test objective and equipment architecture are clearly defined.
Map the likely failure mechanisms
Ambient temperature cycling can stress the module stack and external interfaces. Powered operation adds junction-temperature swings that may fatigue die attach and interconnects. Humidity can contribute to corrosion, insulation degradation and surface leakage, especially at terminals, gel boundaries or contaminated surfaces.
Define which mechanism the test is intended to accelerate. This determines whether the chamber controls ambient air while an external power system creates device heating, or whether the specimen remains unpowered during exposure.
Account for heat generation
A powered module can release significant heat into the chamber. The environmental system must maintain the required air condition while absorbing that load. Provide the chamber supplier with maximum dissipation, duty cycle, fixture mass, coolant conditions and cable routing.
Measure both chamber air and representative module temperatures. Junction temperature may require estimation from electrical parameters or dedicated instrumentation, while case, baseplate and coolant temperatures can often be measured directly.
Build humidity tests around insulation
High humidity can reveal weaknesses in creepage paths, coatings, encapsulation and terminal design. If the device is energized, establish safe voltage and current limits, isolation, fault detection and independent shutdown. Avoid assuming that a generic humidity cycle automatically reproduces field condensation; dew-point conditions must be analyzed separately.
The 2025 edition of IEC 60068-2-78 addresses steady high humidity without condensation, while IEC 60068-2-30 covers cyclic exposure that generally produces condensation. Semiconductor qualification programs may also reference JEDEC methods. Use the exact method and revision specified by the customer.
Improve repeatability
Standardize fixture material, mounting torque, thermal interface material, cable stress and sample orientation. These details can influence module temperature and mechanical loading. Synchronize electrical data with chamber conditions so drift, leakage or intermittent events can be traced to the exposure.
Recommended data can include:
- Case and baseplate temperature.
- Voltage, current and on-state parameters.
- Insulation resistance or leakage current.
- Gate behavior and communication status.
- Coolant inlet and outlet conditions.
- Chamber temperature, humidity and alarms.
Select a system around the whole experiment
SCICOOLING can configure temperature-humidity, rapid-change and thermal-shock systems with power feedthroughs, sensor ports and control interfaces for power semiconductor research and qualification. The chamber is one part of the experiment; robust results require coordinated environmental control, electrical operation, cooling, safety interlocks and time-aligned data.
Editorial note: Confirm the contractual standard edition, test severity, acceptance criteria and final internal URLs before publication.