The Cost of Poor Quality in Magnetic Components: What the Quotation Does Not Show

The Number That Is Never on the Quotation

Two suppliers quote 1.10 and 1.18 for the same transformer. The procurement decision usually goes to 1.10 and is recorded as a saving. Eight months later there is a rework line at the contract manufacturer, a scrap rate nobody budgeted for, and a field return that costs more than the entire annual price difference. Cost of poor quality is the part of the price that is paid later, in someone else’s budget.

Where Magnetic Components Lose Money After Delivery

Typical failure modes and their downstream cost
Failure	How it appears	Typical downstream cost
Inductance out of tolerance	Converter fails efficiency or stability test at the CM	Rework of finished units, engineering time, shipment delay
Leakage inductance over the limit	Ring or overshoot, EMC retest failure	Board redesign, filter cost, delayed certification
Poor solder joint / termination	Open or intermittent in thermal cycling	Field returns, warranty, brand damage
Wrong insulation system	Hipot failures in production, or a safety review finding	Lot rejection, re-qualification, safety compliance risk
Creepage or clearance shortfall	Found at certification, not at incoming inspection	Redesign of the part and the PCB keep-out
Moisture or crack in the core	Noise, loss rise, or failure after reflow	Scrap at the CM, unexplained yield loss

The pattern is consistent: the cost is not the part, it is the disruption. A single lot rejection at a contract manufacturer can idle a line for a shift, and the accounting usually lands in a different cost centre from the one that booked the saving.

Making It Measurable

Three numbers turn this from an argument into a comparison, and all three can be requested before the order:

PPM and the definition behind it. Ask what counts as a defect and whether the figure includes outgoing inspection failures. A supplier quoting 200 PPM that only counts final-test rejects is not quoting the same thing as one that counts in-process scrap.
First-pass yield at the supplier. A wound component that requires a re-wind step is not a stable process. Ask for the rework rate on comparable parts, not the average across the plant.
Field return rate on similar products. The most useful question is not the number but the trend: what failed, and what changed as a result. A supplier that can describe its last failure mode honestly is usually the safer one.

The Contract Levers That Actually Work

Charge-back clause for avoidable defects, with the inspection standard defined in the PO rather than left to discussion after the lot arrives.
Change control: core grade, wire supplier, varnish and winding machine named in the drawing, with re-approval required for any of them.
First-article approval before volume, with the report contents agreed in advance — otherwise the report that arrives is the one the supplier prefers.
Annual quality review with the PPM, the rework rate and the field return data on the table, not just a certificate renewal.

The Honest Arithmetic

If a 1.18 part reduces the CM’s rework by one hour per hundred units, the higher price is usually the cheaper option. The comparison only works if the rework hours are counted, which means procurement and manufacturing engineering have to look at the same sheet. That is the real reason quality discussions stall: nobody owns the total.