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Incoming Inspection for Used MOSFET Lots: A Buyer’s Workflow
Plan lot identification, visual inspection, electrical evidence and acceptance records when purchasing used power MOSFETs.
Published 1 November 2026 · Mosvanta editorial · Updated 4 November 2026
Identify and hold the incoming lot, compare it with the purchase requirements, then record visual and agreed electrical checks under stated conditions. Link each result to the lot and sampled devices. Decide acceptance using the criteria agreed before shipment; a passing sample is not evidence that every device was tested.
Decision checklist
| Check | Evidence to request | Reason to pause approval |
|---|---|---|
| Receipt | Record order, quantity, lot and package photos | Mixing shipments before inspection |
| Electrical check | Use exact datasheet and stated conditions | Comparing resistance readings with no drive conditions |
| Disposition | Record failures, decision and responsible reviewer | Removing failures without investigating the lot |
Incoming inspection should answer a defined purchasing question: does this identified lot meet the requirements agreed for this order? It is not a substitute for circuit qualification, and a basic continuity check cannot establish all datasheet characteristics or long-term reliability.
Start with lot control
Keep incoming packages separate until their identity is recorded. Capture the supplier reference, purchase order, received quantity, claimed MPN, date codes and packing photographs. Assign an internal lot identifier and use it on the inspection record. If markings or conditions differ, record the groups separately instead of combining results into one unexplained average.
Check documents and physical condition
Compare the delivery against the approved sample and agreed condition statement. Review package type, lead arrangement, markings, solder residue, cracks, bent leads and signs of handling damage. Record discrepancies with photographs and counts. Appearance checks can identify visible problems; they do not independently prove authenticity or hidden device integrity.
Specify electrical checks before interpreting results
Agree which characteristics matter, the instrument and fixture, test conditions, limits and sampling method. Keep measured results linked to individual samples where practical. Use the manufacturer datasheet for the exact ordering code; do not apply limits from a similar-looking device.
Gate threshold voltage is specified at a defined small drain current. It should not be interpreted as the gate voltage that fully turns the device on for a power application. See Infineon’s threshold measurement explanation for the role of test conditions.
For on-resistance comparisons, record the gate drive, current and temperature conditions used. Toshiba explains why the gate drive used for an on-resistance specification differs from a threshold measurement in its MOSFET gate-voltage guidance. A number without its conditions is difficult to compare with a datasheet limit.
Handle samples with suitable ESD controls
Use the handling procedure appropriate to the specific device and work area. Gate structures can be sensitive to electrostatic discharge; an incoming test process should not introduce damage. Review the relevant handling information and Infineon’s MOS-gated device ESD application note. This guide does not prescribe a destructive stress test or a universal safe test voltage.
Write an actionable acceptance record
Record the lot size, inspected quantity, selection method, observed defects, measured values, conditions, acceptance criteria and decision. Distinguish “sampled electrical checks passed” from “every device tested.” If a failure appears, hold the affected lot and follow the previously agreed investigation or rejection process rather than silently removing a few failed samples.
Carry the evidence into the next order
Retain results alongside supplier and order references so that repeat purchases can be compared. A previous good lot does not automatically approve a different lot. Our quality-control page helps frame the evidence to request; agree the actual inspection scope for your order before shipment.
Related reading
What should stop an order?
Pause approval when the full part identity, agreed condition or evidence needed for your decision is unresolved. Ask the supplier to clarify the specific gap. Keep the response with the order record so that a later buyer can see what was actually approved.