As industrial manufacturing reaches new heights of precision, the reliability of power semiconductor devices has become the ultimate frontier for engineers. At SHYSEMI, we recognize that as Intelligent Power Modules (IPM) become more integrated, diagnosing their failure modes requires a sophisticated blend of systemic testing and surgical precision.
This guide explores advanced methodologies for IPM failure analysis, focusing on how to localize faults—ranging from HVIC malfunctions to IGBT degradation—while maintaining the integrity of the device under test.
An IPM (Intelligent Power Module) is a highperformance power header that integrates power switching devices (typically IGBTs) with specialized gate drive circuits. Unlike discrete solutions, a SHYSEMI IPM incorporates builtin protection logic for:
- Overvoltage and Overcurrent
- Overtemperature
- Shortcircuit protection
- Undervoltage Lockout (UVLO)
By communicating diagnostic signals directly to the CPU, the IPM ensures systemlevel safety. Their high reliability and "plugandplay" functional density make them indispensable in motor drives, variable frequency inverters, and renewable energy power supplies.
Internal structure schematic diagram of IPM (Intelligent Power Module)
To effectively troubleshoot an IPM, one must understand its internal synergy. A standard threephase inverter IPM (such as those in the SHYSEMI IPM Series) comprises five core elements:
- IGBT Inverter Bridge: Six IGBTs (IGBT1–IGBT6) responsible for power switching.
- UltraSoft Freewheeling Recovery Diodes (FRD): Six diodes connected in antiparallel to the IGBTs to handle reactive power and inductive spikes.
- High Voltage Integrated Circuits (HVIC): Three halfbridge drivers that eliminate the need for optocoupler isolation, reducing system cost and footprint while providing optimal gate drive conditions.
- NTC Thermistor: A Negative Temperature Coefficient sensor mounted on the internal insulated substrate for highspeed thermal protection.
- Filtering Capacitors (RC): Dedicated RC circuits at the HVIC power inputs to suppress noise and ensure signal integrity.
2. Strategic Failure Localization Framework
Since IPMs are multicomponent systems encapsulated in epoxy resin, traditional "destructive" decapsulation can often introduce new artifacts or mask the original root cause. SHYSEMI advocates for a nondestructive functional testing workflow to localize the fault before opening the module.
2.1 Insulation & Dielectric Strength Testing
Often referred to as the "HiPot" test, this verifies the dielectric integrity between the electrically active components and the nonconductive baseplate.
Method: All pins are shorted and connected to the negative terminal of a pressure tester, while the copper baseplate is connected to the positive terminal.
Typical Failure Modes: Insulation failure is usually tied to voids in the encapsulation (due to organic contamination) or mechanical stress cracks in the Direct Bonding Copper (DBC) ceramic substrate caused by improper mounting pressure.
(a) High-voltage withstand test failure due to dielectric voids.
(b) Insulation breakdown resulting from stress cracks in the copper-clad ceramic substrate.
Thermal management is the heartbeat of power electronics. If the IPM’s internal heat dissipation path is compromised, the device’s lifespan drops exponentially.
Diagnostic: We measure the NTC resistance across various temperatures to plot the RT curve.
Common Issues: "Opencircuit" failures often stem from poor NTC soldering (tilting), while "parameter drift" is frequently caused by edge stress cracks or electrical overstress (EOS).
(a) Open-circuit failure due to defective NTC solder joints and tilted mounting.
(b) NTC parameter drift caused by edge stress damage.
Continuity testing utilizes the forward bias of internal ESD protection diodes to "map" the internal connections.
The Curve Tracer Method: By comparing the IV characteristics of a failed unit against a SHYSEMI golden standard, engineers can identify open circuits (broken bond wires) or leakage currents (process defects or ESD damage) without decapsulation.
2.4 FRD (Freewheeling Diode) Characterization
The FRD's performance is critical for switching efficiency. Testing the reverse conduction voltage allows us to evaluate the diode's health independently of the VCC bias.
Ultra-fast Diode Characterization Test
3. Advanced Functional Testing
When basic continuity isn't enough, we look at the dynamic parameters:
HighVoltage Leakage (IDSS): We measure the CollectorEmitter leakage current while the HVIC holds the IGBT in the "OFF" state. A reduced breakdown voltage usually points to IGBT die degradation.
High-voltage leakage current test
4. ComponentLevel Root Cause Analysis
If functional tests are inconclusive, SHYSEMI technicians perform a surgical separation of the HVIC and the IGBT. This involves precision decapsulation and cutting the bond wires between the driver and the power die.
IGBT Analysis: We check for gate leakage. Common culprits for IGBT failure include dynamic avalanche breakdown, "hot spots" from metal melting, and bond wire liftoff.
HVIC Analysis: Statistics show that nearly 50% of field failures are caused by EOS or ESD. Under overstress, HVIC protection circuits can experience "via melting," leading to a loss of gate drive signals (e.g., LVG outputs correctly, but HVG remains dead).
VIA melting caused by ESD was identified in the HVIC internal protection circuit.
Effective IPM failure analysis is a transition from "systemlevel observation" to "componentlevel precision." By utilizing the testing workflows outlined above, SHYSEMI ensures that our partners can rapidly identify failure mechanisms, optimize their system designs, and maintain the highest standards of power efficiency.
Would you like SHYSEMI to provide a detailed technical datasheet for our latest IPM series or assist you with a specific failure analysis report? [Contact-us]