Every programme eventually receives the same email. A lot of boards has shipped, or is about to, and one characteristic is out of specification. The supplier proposes a waiver. The buyer has a build schedule, a customer waiting, and an engineer who says the deviation is cosmetic. The waiver gets signed, the boards ship, and everyone moves on.
Nothing about that single decision is necessarily wrong. The problem is what happens the second, third and fourth time the same characteristic goes out of specification. At some point the concession stops being an exception and becomes, in practice, the specification — but no document says so, the drawing is never revised, and a new supplier quoting the same part will be measured against a requirement the incumbent has not met for a year. This guide covers how to keep waivers and deviations under control: what the two terms actually mean, which defects can be conceded at all, who should be signing at what value, and how to detect the drift before it becomes policy.
Waiver vs Deviation: The Distinction That Decides Everything Else
The two terms are used interchangeably in daily correspondence and mean different things. The distinction is not semantic — it decides whether your next order is measured against the drawing or against a concession.
- A waiver accepts a specific, already-existing nonconformance on a specific lot, for a limited quantity or period. It does not change the requirement. The next lot must comply with the drawing, or it needs its own waiver. This is a one-time concession on a known nonconformance.
- A deviation authorises production against a requirement different from the released drawing for a defined period or quantity — usually before the nonconforming parts exist, often to avoid a tooling change or a material shortage. It is a temporary amendment to the specification.
The practical consequence: a waiver should never be repeatable without a new decision, while a deviation should have an expiry date and a plan to return to the drawing. Programmes that collapse the two end up with documents labelled "waiver" that function as permanent specification changes with no revision control, and with drawings that no longer describe the product being bought.
There is a third category that gets mislabelled as a waiver and should not be: a genuine drawing error. If the requirement itself is impossible or wrong — a hole diameter that cannot be drilled in the specified laminate, a clearance that violates the fabricator's minimum — the correct action is an engineering change order and a drawing revision, not a concession. Conceding a defect caused by a bad drawing teaches the supplier to expect concessions and leaves the root cause in place.
Which Defects Can Be Conceded, and Which Cannot
The list of what is concessionable is shorter than most suppliers suggest and depends on the acceptance class the part was purchased against. The organising principle: a defect can be conceded only if its consequence is fully understood, bounded, and not reliability-related. Anything whose failure mode is progressive, hidden or safety-linked is not concessionable regardless of how small the sample appears.
| Condition | Concessionable? | Reason |
|---|---|---|
| Silkscreen smudge, off-centre legend, ink bleed within legibility | Usually yes | Cosmetic, no effect on assembly or reliability; check it does not obscure a fiducial |
| Solder mask colour or gloss off the approved shade | Yes, with care | Cosmetic — but it becomes a golden-sample problem, so record the accepted shade |
| Board dimension out of tolerance but within assembly clearance | Conditionally | Only if the mating part and the panel/CAM consequences have been checked, not assumed |
| Solder joint below the minimum fillet for the class | No | Progressive failure mode under thermal cycling; a joint that looks close is still under-filled |
| Voiding above the acceptance limit on a thermal pad | No | Directly changes thermal resistance; invisible and not detectable at final test |
| Insufficient copper barrel plating in a via | No | Barrel cracking is a latent field failure, not a yield issue |
| Leakage current or insulation resistance near limit | No | A safety characteristic with no defensible "small" margin |
The third row is where most of the arguments live. A dimension that is out of tolerance but "obviously fits" is not obviously anything until someone has checked the mating part, the assembly fixture, the panel edge clearance and the effect on downstream process. A concession granted on the basis that the buyer's engineer cannot see a problem is a concession granted without analysis — and the analysis is usually one hour of work.
Factory reality: the concessions that cause the most expensive problems are not the obvious cosmetic ones. They are the ones justified by a phrase like "within the spirit of the class". If a defect needs that phrase to be accepted, it is a failure against the standard you purchased, and the honest choice is either to accept it in writing with a reason or to reject it. The middle position is what later becomes unarguable in both directions.
Who Signs, and at What Value
A waiver signed by whoever happened to be on email is not a controlled decision. Authority levels should be set in advance, in the quality agreement, and tied to the consequence rather than to the dollar value of the lot — though lot value is a reasonable secondary trigger.
- Buyer's quality engineer — cosmetic and dimensional concessions on lots below a defined value, where the defect is fully visible and the effect is contained within the buyer's own process. No customer-facing consequence.
- Buyer's engineering plus quality jointly — anything touching an electrical, thermal or mechanical characteristic, or any concession where the analysis required someone to look at the mating assembly.
- Programme owner or customer, where the buyer is not the end user — any concession on a part that ships inside a regulated product, and any concession on a characteristic named in the customer's own drawing or specification. A supplier's concession that voids the buyer's own contractual position is not the buyer's to grant unilaterally.
- Nobody — safety-related characteristics, and anything on a lot already known to be part of a field issue. These are not concession decisions; they are disposition decisions under a failure investigation.
Two mechanics make the authority real rather than nominal. First, the concession record needs a field for what happens to the remaining quantity — is the waiver for this lot only, or does the supplier believe it covers the balance of the order? Second, the record needs a stated consequence: rework, sort, price adjustment, or acceptance as-is with no further claim. A waiver that says "accepted" without saying what was given up in exchange is a document that resolves nothing.
The Drift Problem: When a Concession Becomes the Specification
This is the failure mode that matters most and is almost never monitored. The mechanism is simple: the same characteristic is conceded three times, the supplier adjusts its internal process control to the conceded value because that is what gets accepted, and by the fourth lot the concession is the de facto requirement. The drawing still says otherwise. Nobody has decided anything.
You can detect it with a report nobody has to write by hand if the data already exists — and it usually does, because concessions are documented. Three counts, reviewed quarterly:
- Repeat concessions by characteristic. If the same characteristic is conceded more than twice in twelve months, it is not an exception. Either the drawing is wrong (raise an ECO) or the process is not capable (raise a corrective action), and both routes are more honest than a fourth waiver.
- Concessions by supplier and by lot. A rate that climbs after a process change, a staffing change or a material substitution is an early warning about that change, not about the parts.
- Concessions with no expiry. Any deviation document older than its stated period, still being cited as authority for shipping, is a specification change that was never approved.
The corrective-action half of this belongs in a formal CAPA rather than in email. What a defensible one contains, and how it differs from a root-cause report that only describes the symptom, is set out in our 8D report and CAPA guide. Where the concession pattern traces back to a supplier whose process capability is simply not adequate for the drawing, the right response is a capability conversation backed by data, which is the subject of SPC control charts and Cpk.
What the Concession Record Must Contain
Six fields make a concession record defensible a year later. Most supplier templates have two of them.
- Part number and both revisions — bare board and assembly, stated separately, because a concession on one is not a concession on the other.
- The characteristic and the measured value, against the drawing limit. "Slight misregistration" is not a record; a measured offset against a stated tolerance is.
- Lot identity and quantity covered — work order, date code, and whether the concession is lot-specific or extends to quantities not yet built.
- The justification and who performed the analysis. A name, not a department, and the basis: measurement, calculation, or precedent.
- Disposition of already-built units — including any in transit or in the supplier's finished-goods store. Concessions frequently cover the lot in front of the inspector and silently exclude the three lots behind it.
- Closure route — an ECO number, a corrective action number, or an explicit statement that the drawing will stand and the concession will not recur. A concession with no closure route is an open loop.
Where the concession is granted on an outgoing lot rather than at goods-in, the same fields belong inside the pre-shipment documentation rather than a separate file, because that is the moment when the buyer still has leverage. The mechanics of that gate are covered in our pre-shipment inspection guide.
Contract Clauses That Prevent the Habit
Three clauses do most of the work, and all three are cheap to negotiate at the start and nearly impossible to add later.
- A notification obligation with a clock. The supplier must notify before shipping a nonconforming lot, not after it has been discovered at the buyer's dock. Concessions requested after shipment are requests to accept a fait accompli, and the buyer's leverage at that point is limited to return freight.
- A cap on repeat concessions. The same characteristic may be conceded at most twice in a rolling twelve months; the third occurrence triggers a mandatory corrective action and, at the buyer's option, a re-qualification. This clause converts a pattern into an event somebody has to answer for.
- No concession authority over safety characteristics. Stated explicitly, with the list of characteristics named in the quality agreement rather than left to interpretation.
What ties all of this to the rest of the purchase is the acceptance standard itself. A concession only means something if the requirement it departs from is specific — which is why the sampling plan, the class and the defect catalogue belong in writing before the first order, as set out in our AQL sampling guide. A waiver against a vague requirement concedes nothing measurable.
At Huaxing PCBA, concessions are raised as written records against a named characteristic, drawing limit and lot, with the disposition of all affected quantities stated and a closure route assigned before shipment. Our quality team works to IPC-A-610 Class 2 and 3 acceptance and issues the record as part of the shipment documentation, so the concession history is visible at every goods-in rather than reconstructed during a dispute. Send your drawing and acceptance class for a quote, or ask an engineer how a concession would be handled on your part.
