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ES Incoming Inspection Tests for Power Modules
Supplier testing is only half the story. Learn which visual, electrical, and isolation checks to run on incoming IGBT and SiC modules, how to set acceptance limits, and how to build a baseline that protects your line.
A power module is one of the most expensive components on a converter bill of materials, and it is installed late in assembly, after the heat sink, driver board, and busbar are already in place. Finding a bad unit at that stage means rework, scrap, and schedule loss. Incoming inspection moves the discovery to the receiving dock, where the cost is a few minutes of testing instead of a failed assembly. This guide explains which visual, electrical, and isolation checks matter for IGBT and SiC modules, how to run them consistently, and how to set acceptance criteria you can defend.
Why Incoming Inspection Pays Off
Supplier test reports are valuable, but they describe the module on the day it shipped. Incoming inspection answers a different question: is the unit in your hands the right part, undamaged, and ready to assemble? Four benefits stand out:
- Catches transit and handling damage. Impact, moisture, or electrostatic discharge can occur anywhere between the factory and your dock.
- Confirms identity. Part number, date code, and serial number are checked against the order and the packing list.
- Creates a baseline. Measured values at receipt give you a reference for later drift analysis and make any future warranty claim far stronger. Our guide to RMA and warranty terms explains why that evidence matters.
- Protects downstream assets. A faulty module never reaches a costly driver board, busbar, or cooling plate.
Start with Documents and Visual Checks
Before any instrument is connected, complete a documentation and visual review:
- Match identification. Compare part number, date code, and serial or lot marking with the purchase order. Consistent coding also supports single lot traceability.
- Check the datasheet revision. Make sure the revision you hold is the one your design was based on; our guide on how to compare power module datasheets helps with this.
- Inspect packaging. Look for crushed corners, moisture marks, and damaged ESD protection.
- Inspect the module. Look for housing cracks, bent or damaged pins, terminal deformation, baseplate scratches, and contamination.
- Photograph and log anything unusual. Do this before the module is handled further.
All opening and testing should take place in an ESD-protected area. The ESD Association describes ANSI/ESD S20.20 as the cornerstone for ESD control programs, covering protected areas, grounding, packaging, and training. For practical guidance on storage and handling before testing, see our article on storage and ESD handling of power modules.
Core Electrical Tests
Static (DC) tests are the backbone of incoming inspection because they are fast, repeatable, and sensitive to damage. IEC 60747-9 covers terminology, essential ratings and characteristics, verification of ratings, and methods of measurement for IGBTs, so it is a sound reference for how these measurements should be defined. The table below lists the tests, what they reveal, and example datasheet values from two HIITIO modules.
| Test | What It Reveals | Datasheet Example |
|---|---|---|
| Gate leakage (IGSS / IGES) | Gate dielectric damage, ESD exposure | SiC module HCS200FH120A2C1: 200 nA max at VGS = 20 V. IGBT module HCG200FH120A2D: 400 nA max |
| Gate threshold (VGS(th) / VGE(th)) | Damaged chips, wrong part | SiC: 1.8 V min, 2.7 V typ at ID = 70 mA. IGBT: 4.8 / 5.7 / 6.3 V (min/typ/max) at IC = 2.0 mA |
| Blocking and leakage (V(BR)DSS, IDSS / ICES) | Die damage, contamination, moisture | SiC: 1200 V min breakdown, 2 µA typ IDSS. IGBT: 1.0 mA max ICES |
| On-state (RDS(on) / VDS(on) / VCE(sat)) | Chip quality, internal connection problems | SiC: 9.1 mΩ typ at +18 V, 200 A, 25 °C; VDS(on) 1.82 V typ |
| Diode forward voltage (VF) | Body diode or free-wheeling diode health | SiC: 1.93 V typ at 200 A, 25 °C |
| Isolation (VISOL) | Insulation damage between terminals and baseplate | SiC: 4.0 kV RMS, 50 Hz, 1 min. IGBT: 2.5 kV RMS |
| NTC resistance | Thermistor continuity and calibration | IGBT: R25 of 5.0 kΩ, B25/50 of 3380 K |
Two details deserve attention. First, many datasheet entries are typical values, not limits. The SiC module above lists typical figures for on-state resistance and leakage, so a pass/fail decision needs limits agreed with the supplier. Second, always test under the conditions printed in the datasheet, including gate voltage, current, and temperature, or your numbers cannot be compared with it.
Run Tests Safely and Consistently
Good data depends on good method. Dynex Semiconductor’s note on power semiconductor static testers lists the parameters typically measured (VCEsat, VGEth, ICES, IGES, and diode VF, plus Kelvin contact connectivity) and states that pulsed power is the preferred method so the rise in chip temperature stays minimal. It is a vendor document, but the principle is widely applied. Practical rules include:
- Use pulsed, low-duty-cycle measurements. Self-heating shifts on-state readings, particularly for SiC.
- Use Kelvin connections. They remove contact and lead resistance from low-resistance measurements.
- Control temperature. Record case or ambient temperature with every reading.
- Keep the gate defined. Never leave a gate floating, and use grounded fixtures and wrist straps throughout.
- Calibrate instruments and fixtures. Verify with a known reference unit at regular intervals.
- Respect high-voltage safety. Use interlocks, trained operators, and discharge procedures during blocking and isolation tests.
Sampling Plans and Acceptance Criteria
Not every delivery needs the same depth of testing. Match effort to risk, as shown below.
| Scenario | Suggested Scope | Acceptance Basis |
|---|---|---|
| New supplier or new part number | Full static and isolation tests on all first-article units | Datasheet limits plus supplier-confirmed production limits |
| Established supplier, routine lot | Visual check on all units; static tests on an agreed sample | Datasheet limits and comparison with previous lot data |
| Safety-critical or high-reliability program | Static and isolation tests on every unit | Customer specification, with serial-level records |
| Aged stock or returned inventory | Visual and static re-verification before use | Original baseline and datasheet limits |
| Engineering samples | Full characterization, including dynamic tests where needed | Design requirements; see our SiC sample evaluation guide |
Agree on Limits with Your Supplier
Because datasheets often show typical values only, ask the supplier three questions before your first order:
- What production test limits apply? Request pass/fail limits for typical-only parameters such as on-state resistance and leakage.
- What are the exact test conditions? Match gate drive, current, temperature, and pulse width.
- Can results be correlated? Compare readings on a few shared units so your fixture and theirs agree.
Insulation checks should also follow the module’s rated creepage and clearance; our overview of creepage and clearance for high-voltage modules explains these distances.
Check Mechanical Readiness Before Mounting
A module that passes electrical tests can still be installed badly. Before assembly, confirm baseplate cleanliness, heat sink condition, and screw-hole condition, then follow the datasheet torque. For example, HIITIO’s datasheets list 4 to 6 Nm for the M6 screws of the HCS200FH120A2C1 and 2.5 to 5 Nm for the M5 screws of the HCG200FH120A2D. Record the torque used so it becomes part of the module’s history.
Record Results and Track Trends
Inspection data is only useful if it is kept. Store results by serial number and date code, together with the instrument, fixture, and temperature used. Review them by lot: a gradual shift in gate threshold or on-state voltage across deliveries can reveal a process change before it becomes a field problem, and it gives you evidence to raise with your supplier. Pair this habit with a formal change notification process, such as the one described in our PCN management guide, so you are alerted when materials or processes change. Retain the records for at least the length of the applicable warranty.
Receive Modules You Can Verify and Trust
Inspection is easier when the module comes with clear data. HIITIO Semiconductor publishes datasheets for its SiC modules and IGBT modules, including the HCS200FH120A2C1 (62 mm, 1200 V, 200 A SiC half-bridge) and the HCG200FH120A2D (62 mm, 1200 V, 200 A IGBT half-bridge). Our modules go through 100% X-ray void inspection and dynamic and static electrical testing during manufacturing. Tell our engineers your application and inspection approach, and ask for test conditions and recommended production limits in writing with your quotation, so your receiving team and ours work from the same numbers. We can also pair modules with matching IGBT and SiC gate drivers and provide datasheets for your evaluation. Technical support is available around the clock, and custom requests receive a tailored recommendation within 24 hours, from the first sample through volume production. Contact HIITIO to get started.
Frequently Asked Questions
Do I need to test every power module I receive?
Not necessarily. Test every unit for first articles and safety-critical programs, and use an agreed sampling plan for routine lots from a qualified supplier. What matters is that the plan is documented and agreed with the supplier before problems arise.
Can I check a module with a multimeter?
A multimeter in diode mode can show gross faults such as a short, but it cannot verify leakage, threshold voltage, or on-state performance. Use a static tester or a curve tracer with pulsed measurements for meaningful incoming inspection data.
What should I do if a reading is outside the datasheet limit?
Re-measure using the correct fixture, conditions, and ESD precautions first. If the result is confirmed, quarantine the unit, record the data and photographs, and contact the supplier with the serial number, date code, and test conditions.
Should incoming inspection include dynamic switching tests?
Usually not for routine lots. Static tests catch most handling and manufacturing problems quickly. Dynamic tests are better suited to engineering samples, qualification work, and designs where switching behavior is critical.
How do I judge a value when the datasheet only gives a typical figure?
A typical value is not a pass/fail limit. Ask the supplier for production limits, and build your own lot-to-lot baseline so you can recognize outliers even before formal limits are agreed.
