AQG 324 (Automotive Qualification Guideline 324) is a guideline jointly developed by ZVEI (Zentralverband Elektrotechnik- und Elektronikindustrie) and ECPE (European Center for Power Electronics) as a quality qualification standard for automotive power modules. It is widely referenced for the reliability verification of IGBT and SiC MOSFET modules used in automotive inverters, OBCs (on-board chargers), and DC-DC converters, and is incorporated into the procurement requirements of major OEMs and Tier 1 suppliers.
Automotive power modules are subjected to more severe conditions than those for general industrial use. As EV power systems shift from 400V to 800V, some manufacturers have already introduced 1,200V GaN specifications. With the trends toward higher voltage and higher output, the reliability verification standards for automotive power devices are becoming increasingly stringent. AQG 324 reflects these market demands, requiring higher load conditions and long-term durability than consumer and industrial standards such as JEDEC.
Humidity and Corrosion Tests
THB (Temperature Humidity Bias), H3TRB, HAST, etc. Long-term verification of moisture resistance reliability for encapsulants and bonding.
Power Cycling Tests
Repeated junction temperature fluctuations (ΔTj). Evaluation of fatigue failure modes in solder layers, bond wires, and substrates.
Thermal Shock and Temperature Cycling
Verification of thermal expansion differences in laminated structures due to rapid temperature changes. Accelerated evaluation of delamination at package interfaces.
Vibration and Mechanical Shock
Confirmation of terminal and encapsulant resistance to road noise and shocks during vehicle operation.
Structure of Test Requirements
AQG 324 assumes the qualification of the entire module, and in principle, evaluates the finished product including the package, substrate, terminals, and encapsulant, rather than the chip alone. Test items are classified as Mandatory and Recommended, and additional tests may be imposed depending on the application's stress profile (cooling method, switching frequency, operating environment).
In power cycling tests, durability is evaluated based on the relationship between junction temperature fluctuation (ΔTj) and the number of cycles. Since the junction temperature limit for SiC modules is higher than for Si (175–200°C), the absolute temperature increases even at the same ΔTj, requiring different knowledge for the selection of solder materials and substrates than in the past. ROHM's TRCDRIVE pack™ is offered in designs that include part numbers compatible with the AQG 324 automotive power module standard, achieving both a low main wiring inductance of 5.7nH and a power density 1.5 times higher than that of general SiC molded modules.
SiC-Specific Challenges and Countermeasures
As wide-bandgap semiconductors are widely adopted as key technologies for EVs and energy storage systems, there are unique challenges in the AQG 324 qualification of SiC MOSFETs.
First, gate oxide reliability: The SiO₂/SiC interface in SiC has a higher defect density than in Si, necessitating separate monitoring of gate threshold voltage shifts under high-temperature, long-term bias. Second, changes in joining technology: To accommodate high current density and high-temperature operation, the industry is shifting from aluminum wires to copper clips and sintered silver joining. Third, body diode degradation: SiC body diodes are susceptible to degradation under current conduction (increase in Vf), making it essential to confirm characteristic changes before and after the AQG 324 power cycling test.
Infineon offers a power module portfolio covering four categories—IGBTs, SiC MOSFETs, thyristors, and diodes—for both industrial and automotive applications, with Si/SiC MOSFET modules catering to a wide range of applications. As the scenario of BEVs completely replacing ICE vehicles has receded, and the coexistence of ICE, BEV, and HEV vehicles has become the mainstream market forecast, the period for which IGBTs and SiC will run in parallel is expected to be longer, making the AQG 324 compliance of both devices continuously important.
Implications for Procurement and Design
AQG 324 qualification is not just about obtaining certification; the practical challenge lies in aligning with customer-specific requirements for each OEM. Major OEMs may impose their own test conditions (such as a higher number of power cycles or specific cooling conditions) as additional requirements on top of AQG 324, making it necessary to confirm customer specifications after qualification. When changing suppliers or adopting new components, presentation of the AQG 324 Qualification Test Report is required, making it crucial to plan for data preparation and storage periods (typically 15 years or more) from the initial design phase.