Storage and ESD Handling of Power Modules

A power module can leave the factory in perfect condition and still arrive at the production line compromised. A discharge from a technician’s fingertip, a pallet stored beside a loading dock, or a carton opened straight from a cold warehouse can shorten a module’s service life before it ever carries current. Because modules are high-value, long-lead items, disciplined storage and ESD (electrostatic discharge) handling are among the cheapest forms of reliability insurance. This guide covers how to receive, store, and handle IGBT and SiC power modules, what the datasheet does and does not tell you, and which checks catch problems before installation.

Why Storage and ESD Handling Matter

Power modules look rugged, but several parts of them are not. Four risks are worth keeping in mind:

• Sensitive gate and signal terminals. The gate and auxiliary pins connect to thin gate dielectrics and sensing circuits that a small discharge can damage.
• Partial damage. A module can be degraded without failing on the spot, so a faulty unit may pass a quick check and fail later in service.
• Environmental exposure. Condensation, corrosive gases, and long storage in poor conditions can affect terminals and interfaces.
• Mechanical shock. Drops and impacts during transport or stocking can damage internal structures that are not visible from outside.

The ESD Association’s device sensitivity primer explains that susceptibility depends on a device’s ability to withstand or shunt discharge energy, and cautions that devices are becoming more sensitive over time. Its two common test models illustrate the threat. The Human Body Model (HBM) represents a discharge from a person’s fingertip using a 100 pF capacitor and a 1.5 kΩ resistor. The Charged Device Model (CDM) represents a charged device discharging to a conductive surface in under about a nanosecond, with peak currents of several tens of amperes. Sensitivity classes are described as guides, not absolutes, so the safest assumption is that every module needs full ESD precautions.

Where ESD Risk Enters a Module’s Life

ESD exposure is not limited to the assembly line. It follows the module from the dock to the field. The table below links each stage to its main risk and the controls that address it.

Infineon’s mounting instructions for the EconoDUAL 3 package state the practice plainly: ESD workstations are mandatory for unpacking, with a high-impedance ground connection, a conductive surface, and wrist straps, and modules must not be operated or measured with open gate-emitter terminals. The same note says its modules ship with ESD protection at the terminals. Although that document covers Infineon’s own product, the principles apply to any module in the same class.

A Note on SiC Gates

Silicon carbide MOSFET gates leave less margin than many engineers expect. On HIITIO’s discrete SiC MOSFET pages, such as the HCM13S12T4K3A, the gate-source absolute maximum is -10/+22 V, with recommended operating values of -5/+18 V. Those are electrical operating limits, not ESD ratings, but they show how narrow the safe window is. Extra care with grounding and gate drive is therefore well justified, and our guide to body diode degradation and forward voltage drift covers another SiC reliability topic worth planning for.

Receiving and Unpacking: A Step-by-Step Routine

A consistent routine prevents most handling damage:

1. Inspect the outer carton. Look for crushed corners, impact marks, or moisture before accepting the delivery.
2. Acclimatize cold shipments. Let cartons reach room temperature before opening to avoid condensation on terminals and baseplates.
3. Move to the protected area. Open packaging only at a grounded ESD workstation.
4. Keep terminal protection in place. Remove it only at the moment of installation.
5. Hold the module by its body. Avoid touching gate, auxiliary, and NTC pins.
6. Record identification data. Log the date code and serial number, which supports single lot traceability if a question arises later.

Shipping damage deserves its own attention. Our overview of import logistics for power module buyers explains how to plan packaging and transit so units arrive intact.

Storage Conditions: What to Confirm

Storage limits are not universal, so the supplier’s datasheet and packaging label take priority. The table below summarizes the main conditions and what to confirm.

The Infineon note adds one practical benefit: modules stored under the recommended conditions do not need pre-drying before assembly. Whatever your supplier’s rules are, the same discipline applies in the warehouse:

• Use first-in, first-out. Rotate stock by date code so older modules ship first.
• Control the area. Keep stock away from dock doors, chemicals, and direct sunlight.

If you hold engineering samples for extended trials, our guide to SiC power module sample evaluation covers how to organize them.

Handling During Mounting and Assembly

Good storage can be undone at the heat sink. A few points deserve attention during installation:

• Flat, clean interfaces. Infineon’s note recommends heat sink flatness of 30 µm or better and surface roughness Rz of 10 µm or less, with contact surfaces cleaned only with a fresh, lint-free cloth.
• Controlled thermal interface material. It recommends screen printing for a uniform, repeatable layer and keeping screw holes free of paste, since contamination can affect torque. Treat these as reference values and confirm your supplier’s own limits.
• Specified torque. HIITIO’s datasheet for the 62 mm 1200 V 200 A SiC module (HCS200FH120A2C1) lists 4 to 6 Nm for M6 mounting, while the ED3 1200 V 900 A SiC module (HCS900FH120D3C1) lists 3 to 6 Nm for M5 or M6 screws.
• Defined gate path. Connect the gate driver and its gate network before power is applied. Our IGBT and SiC gate driver range is designed to pair with these modules.

Thermal performance also depends on mounting quality, which ties into the points in our article on junction temperature in power modules.

Post-Handling Checks Before Installation

A short verification step can catch damage that visual inspection will miss:

• Gate leakage and threshold checks. Compare against datasheet limits using grounded fixtures.
• On-state check at low current. An unexpected shift in RDS(on) or VCE(sat) can flag a damaged unit.
• NTC verification. Confirm the thermistor reads sensibly at room temperature.
• Quarantine suspect units. If a module has been dropped, exposed to condensation, or mishandled, hold it and contact the supplier rather than installing it.

Build an ESD Control Program That Lasts

Individual precautions work best inside a documented program. The ESD Association describes ANSI/ESD S20.20 as the cornerstone for developing effective ESD control programs. Its program plan covers ESD protected areas, grounding and equipotential bonding, personnel grounding, packaging, and training, and it states that all conductors in the environment, including personnel, shall be bonded. In practice, that means written procedures, trained staff, routine checks of wrist straps and work surfaces, and clear ownership.

Protect Your Modules from Dock to Deployment

Good handling starts with good product and clear documentation. HIITIO Semiconductor supplies SiC modules and IGBT modules in industry-standard packages, including the ED3 1200 V 900 A half-bridge SiC module with a Si₃N₄ AMB substrate, a built-in thermistor, and a 175 °C maximum junction temperature. Tell our engineers about your application, storage practices, and assembly process, and we will recommend suitable modules and drivers, along with the datasheets and handling guidance your team needs. Please ask for storage-duration and ESD handling guidance in writing together with your quotation, so your receiving and production teams work from the same rules. Our modules go through 100% X-ray void inspection and dynamic and static electrical testing during manufacturing, and our technical support is available around the clock. Custom requests receive a tailored recommendation within 24 hours, from the first sample through volume production. Contact HIITIO to get started.

Frequently Asked Questions

How long can power modules be stored?

There is no universal limit. Storage time depends on the supplier, the package, and the storage conditions. For example, Infineon recommends a maximum of two years for its EconoDUAL 3 modules under its recommended conditions. Ask your supplier for the limit that applies to your exact part number and record it in your inventory system.

Are SiC modules more ESD sensitive than IGBT modules?

Treat both as ESD-sensitive. SiC MOSFET gates have a narrow safe window, with absolute maximum ratings of -10/+22 V on HIITIO’s SiC datasheets and recommended drive values close to that range, so grounding and gate-drive discipline are especially important. The same ESD workstation rules should apply to every module type.

Can I measure a module with the gate left floating?

No. Modules should not be operated or measured with open gate-emitter terminals. Use a grounded fixture and a defined gate path, and connect the gate driver before applying power.

What should I do if a module was dropped or exposed to condensation?

Quarantine it and do not install it. Check its electrical parameters against datasheet limits, record what happened, and contact your supplier for guidance. A module with hidden mechanical or moisture damage can fail later in service.

Do I need an ESD workstation just to receive sealed cartons?

Sealed ESD packaging protects the module in transit, so the carton itself can be handled normally. Open it only at a grounded ESD workstation and keep terminal protection in place until the module is ready to install.