First Article Inspection Report for Magnetic Components: What It Must Contain

What a First Article Report Should Contain

A first article inspection (FAI) report is the document that proves a supplier can build the part you specified — not the part they intended to build. In magnetic components, the report is often thin: a drawing sign-off, a hipot result, an inductance reading. That is enough to release a standard part and not nearly enough to release a custom transformer or a choke going into a safety-critical application.

This note lists what a complete FAI report contains for a wound component, and the five items most often missing.

The Full Contents

FAI report contents for a magnetic component
Section	Evidence	Why it is needed
Drawing and revision	Ballooned drawing with every dimension numbered	Ties the report to the controlled document
Dimensional results	Measured values per balloon, with instrument and tolerance	Catches envelope and pin position errors
Electrical results	Inductance, DCR, turns ratio, hipot, IR — with test conditions	Confirms the magnetic design, not just pass/fail
Material traceability	Core grade and lot, wire, bobbin resin, varnish, tape	Proves the approved BOM was used
Process records	Winding program, solder pot verification, cure profile, potting ratio	Shows the process, not only the outcome
Insulation system	UL file reference and the barrier stack as built	Connects the part to the safety qualification
Photographs	Winding layers before closure, terminal area, marking	Reveals what drawings cannot show
Nonconformance	Any deviation with disposition and approval	Prevents silent acceptance

The Five Items Usually Missing

1. Test conditions. An inductance number without frequency, bias, and instrument is not a measurement. A DCR without temperature is equally ambiguous.

2. Winding layer photographs. The barrier stack and the layer arrangement are the most error-prone part of a transformer, and they are invisible in a finished part. Photographs taken before closure, or an X-ray of the wound section, are the only evidence.

3. Material lot identity. “Core: MnZn ferrite” is not traceability. The grade and lot number link to the supplier’s certificate and enable a later recall.

4. Cure and process parameters. Varnish cure time and temperature, potting mix ratio, and solder pot temperature are process controls that determine field reliability; a report without them cannot distinguish a good part from a lucky one.

5. Nonconformance disclosure. A clean report with no deviations is either a very good supplier or a report that hides something. Ask explicitly what deviated and how it was dispositioned.

Sampling and Repeat Requirements

FAI is required at the first production run, and again after any of the following: a tooling change, a material change, a process change, a site change, or a gap in production longer than a defined period (typically 12 months). Suppliers who treat FAI as a one-time event at program launch are usually the ones who ship a changed varnish two years later without notice.

How to Review It Efficiently

Do not read the report top to bottom. Check three things first: the drawing revision matches your controlled release; the insulation system reference covers the construction as built; and the electrical results include the test conditions. Those three catch most of the risk. Then check material lots against the approved BOM and read the nonconformance section last, because that is where the honest information usually sits.