Application Note: Troubleshooting Common IGBT Module Failures

An IGBT module failure can be a costly and time-consuming event. Understanding the root cause is essential to prevent future occurrences. This guide covers the most common failure modes our FAEs encounter and how to diagnose them.

Failure Mode 1: Short-Circuit / Overcurrent

This is one of the most destructive failure modes. It occurs when the IGBT is forced to conduct a current far beyond its rated maximum, often due to a load short-circuit or a shoot-through event in a half-bridge.

Symptoms:

• Catastrophic failure with visible damage to the module casing (cracks, burn marks).
• Internal bond wires fused or lifted.
• Shorted collector-emitter junction.

Prevention:

Ensure your gate driver has a fast-acting desaturation (DESAT) protection circuit that can turn off the IGBT within the specified Short-Circuit Withstand Time (typically 5-10µs).

Failure Mode 2: Overvoltage

This occurs when the voltage across the collector-emitter (Vce) exceeds the module's breakdown voltage rating (Vces). This is often caused by stray inductance in the DC-link busbar during high di/dt switching events.

Symptoms:

• Punctured die, often with no external signs of damage.
• Increased collector-emitter leakage current.

Prevention:

Minimize the inductance in your DC bus layout using laminated busbars. Use high-quality, low-ESL DC-link capacitors and consider adding a snubber circuit if voltage overshoot is still an issue.