Solder Joint Acceptance Class and Defect Disposition: What Your PO Has to Say Before a Batch Is Judged

"Pass" is a citation, not an observation

When an assembler tells you a batch passed, they are not reporting something they saw. They are reporting that what they saw fell inside a boundary that somebody chose. Change the boundary and the same physical board changes status without anyone touching it.

This matters because of what follows. If a batch is judged non-conforming, the next three decisions — rework, sort, accept as is, or scrap — each cost a different amount and take a different number of days. Those decisions get made quickly, often within a shift, and they get made by whoever your purchase order left holding the authority. If the PO is silent, the authority defaults to the assembler's internal procedure. You find out what was decided when the boxes arrive.

So there are two separate things to write down, and most POs write neither:

1. Which judgement applies — the acceptance class, plus the four things a class alone does not settle.
2. What happens after a fail — who decides the disposition, who is notified, what evidence re-releases the batch, and how many times a joint may be reworked.

This article is about those two. It is not about why joints fail; the mechanisms, from wetting through cracking, are a separate subject and PCB168 covers them in PCBA solder joint failure causes and troubleshooting. Mechanism tells you what went wrong. Criteria tell you whose problem it is.

Three legitimate reasons two people disagree about the same board

Before blaming anyone, rule out the cases where both parties are reading correctly and still disagreeing.

The class is different. IPC-A-610 defines acceptance conditions across classes reflecting different end-use expectations. A joint condition that is acceptable in a general-purpose assembly can be non-conforming in a high-reliability one. Neither inspector is wrong. The PO chose one of them, or failed to.

The component category is different. Acceptance conditions are written per joint type — through-hole, chip terminations, gull-wing leads, J-leads, bottom-termination parts, area-array packages. "The solder joints are fine" is not a claim you can evaluate until you know which category is in dispute. A batch can be fully conforming on every leaded part and non-conforming on a single bottom-terminated component.

The detection method is different. Conditions visible under magnified visual inspection are not the same set as conditions visible under automated optical inspection, and neither covers what only transmissive imaging reveals under a package you cannot see beneath. If your requirement says "inspect solder joints" without saying how, the assembler will use their standard method, and their standard method defines what can possibly be found. A defect class that your chosen method cannot detect is, operationally, not part of your acceptance criteria at all.

Each of these is a drafting gap, not a performance failure. All three get closed with sentences, not with better soldering.

Why "per IPC-A-610 Class 3" is not yet a requirement

This is the single most common line in assembly POs, and on its own it leaves four holes.

It does not say which parts. Applying the strictest class uniformly across a board that carries both a connector shell and a fine-pitch array is a decision with cost consequences, and it is often not the decision you intended. Write the class per component group when the board is mixed, or state explicitly that it applies to all.

It does not say by what method. Name the inspection method per category. If area-array parts are in scope and you expect anything beneath them to be evaluated, that expectation has to be written, because visual inspection cannot reach it and no one will add a method you did not ask for.

It does not say how much gets looked at. One hundred percent inspection, sampling, or first-piece-then-sampling are three different quotations. A sampling plan also has a consequence you should state deliberately: a lot can pass while containing non-conforming units, and that is the plan working as designed, not a breach. If that outcome is unacceptable to you, you need a different plan, not a complaint later.

It does not say who adjudicates. When your incoming inspection and the assembler's outgoing inspection disagree — and on borderline conditions they will — someone has to be the tie-breaker. Name them in advance. Naming them after a dispute starts is a negotiation; naming them before is a clause.

A practical framing: the class is the *scale*, and these four are the *scope*. A scale without a scope cannot produce a repeatable verdict, which is why the same PO can yield a clean batch in March and a disputed batch in June with no process change on either side. If you are still building the broader inspection requirement rather than just the solder criteria, PCB168 covers that structure in defining PCBA test and inspection requirements before you get quoted.

Four dispositions, four different costs

Once a non-conformance is recorded, exactly four things can happen to the affected units. They are not interchangeable, and the choice is usually made under schedule pressure.

Rework. The joint is reprocessed to bring it into conformance. Reprocessing applies heat to a part and a pad that have already been heated. It is a legitimate, standardised activity — IPC-7711/7721 exists precisely to describe how it is done properly — but it is not a free undo. Each cycle is an event in that joint's history, which is why a rework limit belongs in the PO.

Sort. The lot is screened and conforming units are shipped. This preserves schedule for part of the quantity and converts the rest into a separate decision. The commercial question is who pays for the screening labour and who owns the rejects, and that answer depends on your material ownership arrangement rather than on the solder criteria.

Accept as is. You, the buyer, waive the requirement for this batch. This is the fastest route and the one most often handled badly, which gets its own section below.

Scrap. The units are destroyed and rebuilt. Longest path, cleanest record.

Notice that two of these four — accept as is and sort — require *your* decision, because they change what you receive relative to what you specified. That is the whole reason a disposition authority matrix is necessary: half the available responses are not the assembler's to choose.

The disposition authority matrix

This is the part that converts a quality discussion into an executable clause. For each non-conformance category, state four things: who decides, who must be notified, within what time, and whether production continues meanwhile.

Adapt the rows to your programme. What matters is not these specific allocations but that every category has exactly one named decider and that the categories where you want control are written as *buyer only* rather than left to inference. The common failure mode is a PO that says quality must be high and says nothing about who decides what happens when it is not.

The notification column deserves one note. "Notify the buyer" with no time attached is not enforceable and, more practically, is not useful: a notification that arrives after the reprocessing is done is a status report, not a decision point. Attach a window, and make it a window your own side can actually answer within.

Rework clauses: authorisation, evidence, limits, identification

Four items, each of which closes a specific hole.

Authorisation before the fact. State which rework categories need your approval before work starts, consistent with the matrix. Retrospective approval requests are not approvals; by the time you see one, your only options are to accept the work or reject a batch you have already paid to have reprocessed twice over.

Evidence that re-releases the batch. Rework creates a new question: on what basis is the batch now acceptable? Decide whether you require re-inspection of only the reworked joints, of the whole unit, or of the whole lot, and whether the record shows which units were touched. Without this, a reworked lot arrives indistinguishable from a lot that never had a problem — and you lose the ability to correlate any later field behaviour with the rework history, because the history is not in your records.

A cycle limit. State the maximum number of reprocessing cycles permitted on a joint and on a component, and state what happens when the limit is reached (scrap, or escalate to you). This is one place where you should resist writing a number you cannot justify: the appropriate limit depends on the component, the termination, the board, and the thermal profile, which is exactly why it is a question to settle with your assembler in the engineering review rather than a figure to copy from an article. Write that the limit must be stated and agreed; let the agreed value come from the review.

Identification. Decide whether reworked units must be identifiable on arrival — by serial, by position in the packing, or by a lot sub-code. If a programme has field reliability obligations, this is not optional, and it is far cheaper to require than to reconstruct.

If you already require a first-article evidence package, note that the rework record is a different document with a different purpose. First article answers whether the build is right; rework records answer what happened to specific units afterwards. PCB168 separates those in PCBA first article inspection report: which rows are release criteria.

Accept-as-is must be per batch, in writing, never standing

The use-as-is concession is where well-drafted agreements quietly come apart, and it happens for an understandable reason: it is the only disposition that costs nothing and takes no time. Under schedule pressure, both sides like it.

The failure is not using it. The failure is letting it become standing. Once a condition has been waived twice, it starts being treated as the working standard — not through anyone's bad faith, but because the people on the line reasonably infer that this condition is acceptable to this customer. The specification on paper and the specification in practice separate, and nobody records the moment it happened.

Three rules keep it contained. One batch per concession, with the batch identified. A stated reason, so the record shows what was waived and why. No precedent language — an explicit sentence that the concession does not alter the acceptance criteria for any subsequent batch. The third is the one people skip and the one that does the work.

There is also a boundary worth knowing before you grant one. A concession waives your right to reject *that* batch for *that* condition. It does not settle what happens if the condition later contributes to a field failure, and whether it does is a function of your warranty and liability terms, not of the concession note. Keep the two documents separate and do not let a quality email resolve a commercial question.

A PO clause block you can adapt

This is a drafting starting point for your legal and engineering review, not a finished contract.

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SOLDER JOINT ACCEPTANCE AND DISPOSITION

1. ACCEPTANCE CRITERIA

1.1 Acceptance per IPC-A-610, class as specified per component group

in Attachment A. Where Attachment A is silent, [class] applies.

1.2 Process requirements per J-STD-001 as applicable to the classes

in 1.1.

1.3 Inspection method per component category is specified in

Attachment A. Categories not listed are inspected by the

Supplier's standard method, which shall be stated in the quotation.

1.4 Inspection coverage: [100% / sampling plan reference] per

Attachment A. Buyer acknowledges that a sampling plan may pass a

lot containing non-conforming units.

1.5 Where Buyer and Supplier inspection results conflict, the

adjudicator is [named party or method] and the result is binding

on both parties.

1. DISPOSITION AUTHORITY

2.1 Disposition authority by non-conformance category is per the

matrix in Attachment B.

2.2 Categories marked "Buyer only" shall not be dispositioned

without Buyer's prior written instruction.

2.3 Supplier shall notify Buyer within [N] working hours of

recording a non-conformance in a Buyer-authority category, and

shall hold affected material pending instruction.

1. REWORK

3.1 Rework per IPC-7711/7721 as applicable.

3.2 Rework in categories requiring Buyer authorisation shall not

commence before written authorisation is received.

3.3 Maximum reprocessing cycles per joint and per component shall be

agreed in the engineering review and recorded in Attachment C.

On reaching the limit, affected units are [scrapped / escalated].

3.4 Re-release evidence: [scope of re-inspection] with records

identifying reworked units.

3.5 Reworked units shall be identifiable on delivery by [method].

1. USE-AS-IS CONCESSION

4.1 Concessions are granted by Buyer in writing, for one identified

batch, with a stated reason.

4.2 A concession does not amend the acceptance criteria and creates

no precedent for subsequent batches.

4.3 A concession does not limit Buyer's rights under the warranty

provisions of this agreement.

1. RECORDS

5.1 Non-conformance and rework records for each lot are a deliverable

and shall be supplied with or before the shipment.

5.2 Records shall be retained for [period] and made available on request.

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Two notes on using it. The bracketed values are deliberately empty — they are the ones that depend on your product, and filling them from a template is how unenforceable POs get written. And Attachments A, B and C are where the real content lives; the clause body only points at them.

What this does to the quotation you get back

Expect the quotation to change, and expect that to be the point.

Requirements written this way are quotable, which means two suppliers' numbers become comparable on the same basis. Requirements written as "high quality workmanship" are not quotable, so each supplier prices their own assumption, and the cheaper number usually belongs to the one who assumed less inspection and more unilateral disposition authority. That gap does not appear anywhere in the quotation document. PCB168 covers reading those boundaries in PCBA quote comparison and scope boundaries.

Expect some line items to appear that were previously invisible: inspection coverage, imaging where you have asked for it, record preparation. These were not absent from the old quotation. They were absent from the old scope, and you were carrying the difference as risk.

One last thing to settle alongside this, because it determines who absorbs the cost of any disposition: whether the material belongs to you or to the assembler at the moment of the non-conformance. Two otherwise identical agreements allocate scrap cost in opposite directions on that basis alone, and PCB168 covers it in PCB assembly contract manufacturing material ownership.

When you are ready to put a specific assembly in front of us, the PCB assembly service page describes our assembly scope, and the quote request page is where the BOM, CPL and your acceptance and disposition attachments go in together. Scope stated in the quotation is what we hold ourselves to; anything beyond the published scope is confirmed in engineering review before it becomes a commitment.

FAQ

Is Class 3 always the right choice for a reliability-critical product?

Not automatically, and applying it board-wide is rarely the intended decision. The classes in IPC-A-610 reflect different end-use expectations, and a mixed board can legitimately carry different classes per component group. The question to answer is which joints actually sit in the reliability path. Specifying the strictest class everywhere raises the inspection burden on parts where it buys nothing, and that cost shows up in the quotation whether or not you intended it. Decide per group, write it in the attachment, and confirm feasibility in engineering review.

Our PO says "per IPC-A-610 Class 2" and a batch was disputed anyway. What was missing?

Almost certainly one of four things: which component categories the class applies to, what inspection method applies per category, how much of the lot was inspected, and who breaks a tie between your inspection and the supplier's. The class gives you a scale. Those four give you a scope. Without the scope, two correct inspectors can reach different verdicts on the same board, which is what a dispute usually is.

Who decides between rework and scrap if the PO is silent?

The supplier, under their internal procedure, because somebody has to decide and the PO did not name you. That is the default you inherit by omission. Two of the four available dispositions — accept-as-is and sort — change what you receive relative to what you specified, so those in particular should be written as buyer-only decisions. Write a disposition matrix with one named decider per category and a notification window attached to each.

How many times can a solder joint be reworked?

There is no universal number, and an article is the wrong place to get one. The appropriate limit depends on the component and its termination style, the board construction, and the thermal profile used for reprocessing. What belongs in your PO is the requirement that a limit be agreed and recorded, plus what happens when it is reached — scrap, or escalation to you. Settle the value with your assembler in the engineering review, where the specific build is in front of both parties.

Does accepting one batch as-is weaken our position on later batches?

It should not, but it will if the concession is written loosely. Grant it for one identified batch, state the reason, and include an explicit sentence that the concession does not amend the acceptance criteria and sets no precedent. The risk is not the concession itself; it is that a condition waived twice starts being treated as the working standard by the people on the line, reasonably, because that is what the pattern told them. Also keep it separate from your warranty terms — a concession waives your right to reject that batch, not whatever your liability provisions say about field failures.

Can we tell on arrival whether a batch was reworked?

Only if you required it. Reworked units arrive indistinguishable from untouched units unless identification is a stated requirement — by serial, by packing position, or by a lot sub-code — and unless the records identify which units were reprocessed. This is cheap to require in the PO and effectively impossible to reconstruct afterwards, which matters if the programme carries field reliability obligations and you later need to correlate behaviour with rework history.

Why does this change the price we are quoted?

Because it makes the requirement quotable. "High quality workmanship" is priced by each supplier against their own assumption, and the lowest number generally belongs to whoever assumed the least inspection and the most unilateral disposition authority — a difference that does not appear in the quotation document. Written criteria and a disposition matrix make two quotations comparable on the same basis. Some line items will become visible that were previously carried by you as risk rather than priced by the supplier.

Related links

• Defining PCBA test and inspection requirements before you get quoted
• PCB assembly service
• Quote request