PCB Fabrication Specifications: What the Shipment Document Package Has to Prove

"Conforms" is a verb with no object

Open the box. On top, in a plastic sleeve, there is a sheet headed *Certificate of Conformance*. It carries your part number, a quantity, a date, a signature, and one sentence: the product supplied conforms to the applicable drawings and specifications.

Read that sentence as a lawyer would and it says almost nothing.

*Which* drawings. *Which* revision. You sent a fabrication drawing in March, answered three engineering queries in April, and approved a stackup change in May. The board that shipped was built to something. The CoC does not say which something.

*Which* units. The CoC lists a quantity. The pallet has four boxes. If one box was built two weeks later from a different material lot, nothing on the paper tells you that, and nothing on the boxes tells you either.

This matters on exactly one day: the day something fails in the field and you need to know whether the failure is confined to one lot or spread across the whole delivery. On that day, a CoC that cannot point at a specific revision and a specific set of units is not evidence. It is stationery.

The fix is not a better certificate. It is four things the purchase order has to require, because none of them appear by default.

Clause one: the declaration has to name a revision

A conformance statement is only as strong as the document it points to. So the PO has to force the pointer to be explicit.

Require that the CoC carry the document identity the buyer controls: the fabrication drawing or specification sheet number *and* its revision, plus the revision date. Not "per customer specification." Not "per PO." The actual revision string you released.

Three things follow from that, and all three are the point:

• If the supplier writes a revision you do not recognise, you have caught a drift before it becomes a field problem.
• If the supplier writes the revision you expect but the board does not match it, your claim has a target. The declaration is wrong, in writing, signed.
• If the build spanned a revision change — common on repeat orders — the supplier now has to say so, because one CoC cannot honestly name two revisions.

Add one more line to the requirement: approved deviations must be listed on the CoC by their own reference. Every real build accumulates them. A waiver granted by email, an engineering query answered with "acceptable as-is," a one-time concession for a material substitution. If those live only in a mailbox, then in eighteen months the board in your hand conforms to a specification it visibly violates, and nobody can explain why. Listed on the CoC, each deviation becomes part of the declared configuration.

What this costs the supplier: nothing except discipline. What it costs you to skip: the ability to say which specification the goods were supposed to meet.

See binding the fabrication specification sheet into the quote for the upstream half of this — fixing the revision *before* the order is placed. This clause is the downstream half: making the shipment point back at it.

Clause two: the lot number has to work in both directions

Traceability is not a number on a form. It is the ability to go from a form to a board, and from a board back to a form. Most document packages only do the first, badly.

So specify both directions explicitly.

Paper to product. The CoC and the packing list must carry a lot or batch identifier, and that identifier must appear on the outside of every carton it covers. One lot per carton, or a clear carton-to-lot map when a carton is mixed. If the delivery contains more than one lot, require separate CoCs or a CoC that breaks the quantity down by lot. A single certificate covering an unspecified mixture is the failure mode you are trying to design out.

Product to paper. This is the half that gets skipped. Require a board-level marking that lets you recover the lot from a bare board that has been out of its box for a year — sitting in a failed unit on a customer's bench, with no carton and no paperwork anywhere near it.

Specify the marking as a requirement, not a preference, and specify it as three decisions you make rather than three defaults you inherit:

• What it encodes. A date code, a lot code, a serial, or a combination. Decide what you actually need to resolve later.
• Where it goes. A designated area on the board, or the panel border — and if the border, understand that the marking leaves with the border at depanel, which defeats the whole clause. Put it on the board.
• How it is applied and whether it survives. Legible after the finish, after assembly, after cleaning. A marking that is unreadable once the board has been through reflow is a marking you will not have when you need it.

IPC-1710 covers supplier declaration and traceability practice, and IPC-6012 addresses board marking and identification. Reference them by name in the PO if you want a common vocabulary, but do not assume referencing a standard chooses these three things for you. It does not. You choose them, or they get chosen for you by whatever the shop already does.

One pointed question for the supplier: *given a single bare board and nothing else, can you tell me its production lot?* If the answer involves a spreadsheet lookup from a code that is actually printed on the board, that works. If the answer is "it would be on the box," you do not have traceability. You have packaging.

Clause three: name the upstream lots that have to travel with the goods

A board's identity is not only its own lot number. It inherits identity from the things it was built out of, and those inheritances are where recalls either stop or spread.

Decide, before the order, which upstream lots have to be named in the document package. The candidates:

• Base material. Laminate and prepreg, by manufacturer and material designation, with the material lot. If you qualified a specific laminate — and if you did, it is because the alternatives were not equivalent for your application — then a CoC that names only "FR-4" has not told you whether you got what you qualified. IPC-4101 gives the specification sheet framework for base materials; name the designation you approved, and require it on paper.
• Surface finish. Which finish, and the chemistry or process lot where the supplier tracks it. Finish-related problems — solderability complaints, discoloration, pad defects appearing weeks after receipt — concentrate in process windows. Without the finish lot, every such complaint spreads across your entire delivery because you cannot prove it does not.
• Subcontracted operations. If any step was outsourced, say so and identify the step. You do not need the subcontractor's internal records; you need to know that a step left the building, because that is where a lot boundary you did not know about got created.
• Material compliance. RoHS, REACH, or whatever regime applies, as a declaration referencing your part number and this shipment — not a generic statement about the supplier's business. IPC-1752A exists as a standard format for material declarations; asking for it by name saves a round of reformatting later.

Two warnings on how to ask for this.

Ask for what you can act on. Every additional item on this list is real work for the supplier and real cost somewhere. If you are never going to open the material lot field, do not require it. A document package nobody reads trains both sides to treat the paperwork as theatre, and then the one field you genuinely needed is also wrong.

Require it on the same page, or require the cross-reference. Material certificates arriving as four separate PDFs with no shared lot number are four documents about nothing in particular. The whole value is the join. Either the CoC carries the upstream lots, or the CoC names the documents that do and those documents name this shipment's lot. State which arrangement you want.

For the stricter version of this — the qualification-stage document set rather than the per-batch one — see qualification documents for automotive HDI and heavy copper RFQs. That is a one-time approval package. This clause is about what has to repeat on every delivery.

Clause four: delivery timing, format and recipient

The last clause is the dullest and the most frequently violated: *when does the package arrive, in what form, to whom.*

A document package that arrives three days after the goods is a document package you have already failed to use, because incoming inspection has either happened without it or stalled waiting for it.

Specify four things:

• Timing. Documents accompany the shipment, or they are transmitted before arrival. Pick one. "Available on request" is not a delivery term — it means the paperwork gets generated after you ask, which is exactly when its independence from the problem under investigation disappears.
• Form. Hard copy with the goods, electronic to a named address, or both. Electronic-only is fine and often better, as long as the shipment carries enough marking to connect the boxes to the file.
• Recipient. A role or an address that still exists when the person who placed the order has moved on. Documents sent to an individual's mailbox are documents your organisation does not have.
• Completeness as a receiving condition. State that an incomplete package is a receiving exception. Not a rejection of the goods — that is disproportionate and will be ignored — but a documented exception that holds the lot in quarantine until the paperwork is right. Without this, the pressure to get parts to the line will override the paperwork every single time, and the gap will only surface months later.

Then connect it to what happens next. Your incoming inspection and acceptance plan should treat the document package as one of the things being inspected, with a stated disposition when it is wrong. And where you have required a first article, the first article inspection report and release terms define a separate, one-time document set — do not let it stand in for the per-lot package, because it covers one build and you are buying many.

Putting the four clauses into PO language

Keep it short enough that a buyer will actually paste it, and specific enough that it constrains something. The structure that survives review:

1. Required documents. List them by name: certificate of conformance, packing list, and whichever upstream declarations clause three selected. Do not write "standard quality documents."
2. Declaration target. The CoC shall identify the fabrication drawing or specification number and revision, with date, and shall list all approved deviations by reference.
3. Lot identification. The CoC and packing list shall state the lot identifier; the identifier shall appear on each carton; where the shipment contains multiple lots, quantities shall be stated per lot.
4. Board marking. Boards shall carry a permanent, legible marking encoding [what you chose], located [where you chose], readable after surface finish and assembly processing.
5. Delivery of documents. Documents shall [accompany the shipment / be transmitted prior to arrival] to [named recipient] in [format]. An incomplete package shall be recorded as a receiving exception.
6. Change notification. Any change to the specification revision used for production, or to any named material or finish, shall be notified before shipment.

Point six overlaps deliberately with change control. If you have repeat orders, the mechanism belongs in its own terms — see change control terms for heavy copper repeat orders — and the CoC then becomes the per-shipment confirmation that nothing moved since the last approval.

What PCB168 can supply under these clauses follows the scope published on its capabilities page, with the specific document set confirmed at engineering review and order confirmation. The point of this article is the asking, not a claim about any one supplier's filing cabinet.

Supplier answers and what to ask next

Four responses you will get, and the follow-up that makes each one useful.

"We provide a CoC with every shipment."

Ask to see a redacted example from a past order. You are checking one thing: does it name a revision and a lot, or is it a template with your part number dropped into it. This takes a supplier five minutes and tells you more than any questionnaire.

"Everything is traceable in our system."

Ask what reaches *you*. Internal traceability is the supplier's asset and does not help you resolve a field failure on your own bench. The question is which identifiers cross the boundary onto paper and onto the board.

"We can add board marking, it will affect the layout."

Correct, and this is a real engineering input, not an obstacle. Give the marking a location in your data package the same way you give a logo one. Decided late, it lands wherever there is room — which is often the panel border, which disappears at depanel.

"Material certificates are available on request."

Decide now whether you want them per shipment or not at all. "On request" means at the moment you request them, someone will go looking — and a certificate retrieved after a problem has been reported is a weaker document than the same certificate filed on arrival.

One closing distinction worth holding onto. None of this makes the boards better. A document package does not improve a single hole or a single pad. What it does is preserve your ability to say, later and with evidence, *which* boards and *why* — and that ability has a shelf life. It is established at the moment of shipment or it is not established at all. Methods of PCB quality inspection tell you whether this batch is good. The document package tells you, a year from now, which batch you were holding.

If you want the document set defined before you place an order, send your drawing, specification revision and marking requirement through the quote request and raise the document package as an explicit line item. What is in scope is described on the capabilities page.

FAQ

Is a certificate of conformance the same thing as a test report?

No, and conflating them is the most common gap in a document package. A CoC is a statement: the supplier declares that the goods meet the named specification. A test report is data: measured or observed results from a specific inspection or test. A CoC can be issued without any attached data, which is normal and acceptable — but it means the CoC alone does not tell you what was checked. If you need the data, require the report separately and require it to carry the same lot identifier, so the two documents join up.

What should the CoC point at if we never issued a formal specification sheet?

Then it points at the most specific thing you did issue: the fabrication drawing, with its revision. If you issued neither, the supplier's own quotation or internal build file becomes the de facto specification, and you have no controlled document to claim against. That is the real problem to fix, and it is an upstream one — fix the specification binding at quotation, then this clause has something to reference.

Our boards are too small for a lot marking. What then?

Then the identity has to live at the next level up, and you have to say so deliberately rather than discover it later. Options: marking at the array or panel level with a stated rule that arrays are not broken before assembly; a marking on the smallest practical unit of packaging with a requirement that the unit is not mixed; or acceptance that traceability resolves to a shipment rather than a lot. All three are legitimate. What is not legitimate is specifying a board marking the board cannot carry and letting the shop silently resolve it.

Do we need material certificates on every shipment?

It depends entirely on whether you would act on them. If your application qualified a specific laminate and a substitution would matter, yes — and name the material designation in the PO so the certificate can be checked against something. If you buy general-purpose boards and would never open the file, requiring it adds cost and teaches both sides that the paperwork is decoration. Decide once, per product, rather than copying another programme's requirement list.

The goods arrived and the paperwork is wrong. Can we reject the shipment?

Commercially that depends on your terms, but treating a paperwork defect as grounds to reject conforming goods is usually disproportionate and will not hold up in practice. The more effective mechanism is the one described above: define an incomplete or incorrect document package as a receiving exception that quarantines the lot until corrected. That keeps the pressure on without stopping your line, and it creates a record — which matters, because a supplier whose document exceptions recur is telling you something about process control well before it shows up in the boards.

How long should the supplier retain the underlying records?

This is a term to negotiate, not a universal number, and it should be driven by your product's service life and any regulatory regime you fall under. Ask the question explicitly at supplier selection and write the answer into the agreement. The failure mode to avoid is assuming a retention period exists because a standard was mentioned somewhere — if the period matters to you, it belongs in your contract in your words.

Does the document package change for assembled boards versus bare boards?

Yes, and the two should be specified separately rather than assumed to merge. An assembled board inherits the bare board's identity plus component lot and process identity, so the document set grows and the lot boundaries multiply. If you buy turnkey, state which level each identifier resolves to — otherwise the assembly lot will be fully traceable while the bare boards inside it are a mixture nobody recorded.