PCB Assembly Contract Manufacturing: Who Owns the Material When Parts Run Short | PCB168

A shortage is not a material problem. It is a clock problem.

Ask a contract manufacturer who owns the material and you will get a one-word answer: turnkey, partial turnkey, or consignment. Write that word into the purchase order and you have settled who sends the invoice for the parts. You have not settled anything that matters on the day a part fails to arrive.

What matters on that day is a sequence of questions that the word does not answer. Was the long-lead part ordered on the day the PO was signed, or on the day the assembler finished reviewing the BOM eleven days later? When the distributor confirms a sixteen-week lead time instead of the quoted six, who is allowed to choose the alternate — and is that the same party who pays the difference in price? The reels that arrived are sitting in the assembler's stores; when exactly did they stop being your material in transit and become material the assembler is accountable for keeping dry and traceable? And the line slot that was reserved for this build: now that it will sit idle for two weeks, does that appear on someone's invoice, or does it quietly become a scheduling problem that pushes your delivery date and nobody's cost?

Each of those is a moment in time, not a category. Material ownership in PCB assembly contract manufacturing is best understood as a small number of transfer moments along a timeline, plus a set of cost clocks that start running when a transfer fails to happen on schedule. The supply model sets the default shape of that timeline. It does not fill in the moments.

This is why shortage disputes so rarely turn on the contract's supply-model clause. Both sides read that clause the same way. They disagree about which day the obligation attached, and about which of the two parties was supposed to act between the day the risk appeared and the day the line stopped.

PCB168's own assembly page states the position plainly: the material supply arrangement is *defined in the RFQ*, and lead time, MOQ, capacity and traceability deliverables are confirmed only in the written quotation or a subsequent engineering response. No fixed numbers are published. That is the correct structure — but it also means the RFQ is where these moments get named, and an RFQ that only names the supply model has left the work undone.

The timeline: six transfer moments worth naming

Strip away the model labels and a PCBA build has the same six moments regardless of who is buying the parts. Naming them is what makes a contract answerable under stress.

M1 — Purchase authority takes effect. The moment a party is both permitted and obliged to place orders. Not the PO date. Not the date the BOM was sent. The date a specific party can commit money against specific line items. If this is left implicit, the default is that nothing is ordered until the assembler has finished BOM review and raised its questions — which can be a week or more after you believe the clock started.

M2 — Long-lead commitment. The point at which the highest-lead-time items are irreversibly ordered. This deserves separation from M1 because it is usually the only moment that determines the delivery date. Everything else can be recovered; a sixteen-week part cannot.

M3 — Incoming receipt and acceptance. The moment material physically arrives at the assembler and is accepted. Ownership of *risk* often moves here even when ownership of *title* does not, and that gap is where buyer-supplied part disputes live.

M4 — Kit complete. The moment every line item on the BOM is physically present and accepted in the quantity required, attrition included. Before M4 the build cannot start. This is the single most useful milestone to define contractually, because the words "kit complete" are what turn "we are waiting for parts" into a dated, attributable state.

M5 — Line release. The moment production capacity is committed to this specific kit. A line slot reserved in advance and then not used has a cost. Whether that cost is yours depends entirely on what M5 says about rescheduling notice.

M6 — Residual disposition. After the build, unused parts, reel remnants and attrition overage have an owner. If the contract names none, the party physically holding them keeps them.

Notice that four of these six moments happen before any solder is melted. A shortage that stops a line on a Tuesday is nearly always the visible consequence of an unnamed M1, M2 or M4 several weeks earlier.

How the three supply models set the defaults

The supply model does not answer M1 through M6. It decides which of them are dangerous if you leave them blank.

Full turnkey — the assembler buys everything. M1 and M2 sit with the assembler, which is the model's real value: one party is accountable for availability and you are not managing distributors. The exposure is that M1 is invisible to you. You cannot see whether the sixteen-week part was ordered in week one or week three, and you will not find out until the delivery date slips. Full turnkey therefore needs one thing the other models do not: a reported M2 date per long-lead line item, not just a promised finish date. Ask for the confirmed order date and confirmed distributor lead time on the top five lead-time drivers. If that reporting is not in the RFQ, full turnkey has moved the risk to the assembler and simultaneously removed your ability to see it.

Partial turnkey — you supply the difficult items, the assembler buys the rest. The most common arrangement and the one that generates the most disputes, because "the rest" is a boundary rather than a list. The failure mode is not that someone bought the wrong part; it is that neither side bought a part each assumed the other had. Partial turnkey needs the BOM annotated line by line with a supply owner — not a rule like "buyer supplies ICs, assembler supplies passives", because the first crystal, connector or magnetic component will not match the rule cleanly. Every line gets an owner or the line is undefined.

Consignment — you supply everything, the assembler charges labour. The lowest part cost and the highest coordination load. All of M1, M2 and M4 are yours. What buyers routinely underestimate is that M3 and M5 are still shared: the assembler receives, stores, handles and stages your material, and the assembler's line slot is still reserved against a kit you are responsible for completing. Consignment does not remove the idle-line question. It makes it more likely to land on you.

A useful way to sanity-check any of the three: if the assembler discovered tomorrow that a part will be twelve weeks late, which party is contractually required to make the next decision, and how many days do they have to make it? A model with no answer to that will produce a phone call instead of a process.

Decision authority and payment responsibility are two different assignments

This is the distinction that most contracts collapse, and collapsing it is what turns a shortage into a negotiation.

When a part goes unavailable there are usually three or four moves available: accept the long lead time and reschedule, approve a form-fit-function alternate, buy from a broker at a premium, or build partial and retrofit later. Each has a different cost and a different risk profile. Two separate questions have to be answered before anyone can move:

Who decides which move is taken?
Who absorbs the cost differential that the move creates?

If the answer to both is "the assembler", you have given it latitude to solve your problem in the way that is cheapest for the assembler. If the answer to both is "the buyer", you have a process that stalls whenever you are asleep or on holiday. Neither is wrong, but they behave very differently, and the workable arrangements usually split the two:

Threshold-based decision authority. The assembler may act unilaterally below a defined cost-delta and schedule-delta threshold, reporting within a fixed window. Above the threshold it must obtain written approval. This keeps small problems from becoming email chains and large ones from becoming surprises.
Alternate approval is separate from ownership. Whether a part is technically acceptable is an engineering question with its own workflow; PCB168's assembly page states that proposed changes should be documented and accepted before purchasing or assembly release. That workflow is covered elsewhere. What the ownership clause must add is narrower: who may invoke it, and how long they have to respond. A ten-day silence on an alternate approval is itself a schedule decision.
Named do-not-substitute items. A short list, marked on the BOM, where no threshold applies and no unilateral action is permitted regardless of cost. Keep it short. A BOM where forty parts are marked DNS is a BOM where none of them are.

Price movement, MOQ and the differences nobody quoted

Material was quoted on a date. It will be bought on a later date. The gap between those two dates has a value, and somebody owns it.

Price validity. A turnkey material quotation is valid for a stated period or it is not a quotation. The question is what happens after it expires and who bears movement inside the validity window. Three arrangements are common: firm price for the validity period, cost-plus with distributor invoices passed through at actual, or firm with a named repricing trigger such as a percentage movement on a specific line item. All three are defensible. None of them is a default — if the RFQ is silent, the assembler will assume the arrangement that protects the assembler.

MOQ overage. A part with a 3,000-piece minimum on a 500-board build with one placement each leaves 2,500 pieces. Who pays for them and who owns them are separate questions, and the second one is the one that gets forgotten. If you pay for MOQ overage, say in writing that the overage is your property, that it is held for a stated period against your next build, and that it is reported in the build's material records. Otherwise you will pay for it once, buy it again on the repeat order, and never see the first batch.

Attrition. Setup parts, first-article placements, machine loss. A percentage is fine; what matters is whether the percentage is supplied by you or bought by the assembler and billed, and who owns what is left. In consignment this is usually the largest single planning error buyers make: shipping exactly the BOM quantity guarantees a shortage at kitting, and the kit will then be incomplete for want of three capacitors.

Broker and premium sourcing. If a part is only available above authorised-distributor pricing, the contract should state whether that route is permitted at all, what documentation is required, and who approves the premium. Sourcing outside authorised channels also raises an authenticity question that is a quality matter as much as a cost one, so a permitted-route clause should say what verification is expected, not only who pays.

The idle line: the cost that appears on no quotation

Here is the item buyers most often fail to price and assemblers most often fail to state.

A build that cannot start because the kit is incomplete does not simply pause. Capacity that was allocated to it either sits unused or gets reassigned. Neither outcome is free, and the two are distributed very differently: unused capacity is a cost the assembler carries, while reassigned capacity is a cost you carry in the form of a delivery date that moves further than the length of the shortage.

Three things make this answerable rather than arguable:

A defined kit-complete milestone (M4). Not "materials received" — complete, in the required quantity including attrition, inspected and accepted. Until M4 is a dated event with criteria, there is no way to say whose delay this is.

A rescheduling notice window. If a reserved line slot is released more than N days ahead, it can usually be refilled and there is no idle cost. Inside N days it frequently cannot. Naming N converts an argument into arithmetic. This is the single most useful number to negotiate at RFQ stage, and it is more useful than arguing about who pays: most disputes disappear once both sides know the threshold and manage against it.

A partial-build rule. Sometimes the right answer is to build everything except the missing part and retrofit later. This carries real cost — a second handling operation, a second inspection, extra records, and a rework step on a finished assembly — so it should be a decision with a stated cost basis, not a favour requested at the last minute. Deciding in advance that partial builds are permitted, and on what commercial terms, keeps this option available when it becomes the cheapest one.

Note that none of the three requires anyone to publish a rate. They require the *events* to be dated and the *thresholds* to be named. The commercial consequence can then be settled per project in the written quotation, which is where PCB168's assembly page places schedule and quantity confirmation in any case.

Buyer-supplied material: the receipt that changes everything

In partial turnkey and consignment, you ship parts to the assembler. That shipment is where title and risk come apart, and where the most bitter disputes originate — because a defective part you supplied is one the assembler did not choose but did receive, store, stage and place.

Four clauses close the gap:

An arrival inspection level. State what the assembler checks on receipt: quantity, part number against the BOM, package and reel integrity, date codes, moisture-barrier bag condition and humidity indicator status. Something minimal and explicit beats something thorough and assumed. The purpose is not to catch every defect; it is to create a dated record of the condition at M3, so that a later failure can be attributed to before or after that date.

Storage and handling conditions. Moisture-sensitive devices have floor-life limits once a barrier bag is opened, and parts you shipped may have spent unknown time in your own stores before that. If the assembler is expected to bake or to track floor life, say so, and disclose the MSL classification of what you sent. If you are not tracking it on your side, the assembler cannot reconstruct it.

Labour cost on defective supplied parts. If a part you supplied is defective out of the bag, the placement labour has already been spent and the removal labour is still to come. Decide in advance whether that is billed, absorbed, or split. This sentence is cheap to write at RFQ stage and expensive to negotiate after a hundred boards are built.

Quantity reconciliation and the return of remainder. A dated record of what was received, what was consumed, what was scrapped and what is returned. Without it, consignment ends with a discrepancy neither party can explain and both parties suspect.

How this article relates to the four adjacent PCB168 guides

This piece deliberately stays on one question: when ownership transfers, and where the cost lands when a transfer is late. Four existing PCB168 articles cover the neighbouring questions, and none of them is repeated here.

Turnkey PCBA BOM risk and alternate part approval covers the approval workflow itself — BOM as a single source of truth, line-by-line review, risk ranking, formal change control. Read it for *how* an alternate gets approved. This article only adds *who may start that process and within what window*.
PCBA quote comparison and scope boundaries covers normalising several quotations against each other — NRE and tooling, test scope, attrition and MOQ as comparison line items, freight terms, quote validity. Read it when you are comparing bids. This article assumes the supplier is chosen and the contract is being written.
PCB assembly contract manufacturing supplier scope covers splitting bare-board fabrication from assembly and the four responsibility lines that split creates, including failure attribution and rework. Read it when deciding on structure. This article stays inside the material line and goes deeper on its timing.
PCBA test and inspection requirement definition for RFQs covers defining what gets inspected and tested. Read it to write that section of the RFQ. Here, inspection appears only as the dated record that makes M3 attributable.

The supply-model definitions and the assembly scope itself live on the PCB assembly product page and the capabilities overview.

What to fix before the purchase order

A material-ownership section that survives a shortage needs eight things. None of them requires a number from your supplier.

Supply model, named per BOM line — not per project. Every line has an owner or the line is undefined.
M1 and M2 dated — when purchase authority takes effect, and a reported confirmed-order date for the top lead-time drivers.
Decision authority split from payment responsibility, with a cost-delta and schedule-delta threshold below which the assembler may act and report.
A short do-not-substitute list on the BOM, exempt from the threshold.
Price validity, repricing trigger and MOQ overage ownership stated explicitly, including where the overage is held and for how long.
Attrition quantity, source and residual owner.
Kit-complete (M4) criteria and a rescheduling notice window, plus whether partial builds are permitted and on what basis.
Arrival inspection level, MSL disclosure and quantity reconciliation for anything you ship in.

Send that alongside the BOM, fabrication data, placement data and drawings when you request an assembly quote. A supplier who answers all eight in writing has told you more about how the project will run than any capability list can.

FAQ

Is full turnkey always the lowest-risk option in PCB assembly contract manufacturing?

It is the lowest-workload option and it consolidates accountability, which is not the same thing. Full turnkey moves purchase authority to the assembler, and with it your visibility of when long-lead items were actually ordered. It becomes genuinely low-risk when the RFQ also requires reporting of confirmed order dates and confirmed lead times on the main lead-time drivers. Without that reporting you will learn about a late part at the same time you learn your delivery date has moved.

In consignment, am I still exposed to idle-line cost if my kit is late?

Usually yes, and buyers often assume otherwise. Consignment means you supply material and are billed for labour, but the assembler has still allocated capacity against your build. Whether an incomplete kit triggers a commercial consequence depends on the rescheduling notice window in your agreement, not on the supply model. Agree that window in writing before the first order.

Who should decide on an alternate part when a shortage hits — us or the assembler?

Split it. Give the assembler authority to act below a defined cost-delta and schedule-delta threshold with mandatory reporting inside a fixed window, and require written approval above it. Keep a short, explicit do-not-substitute list that no threshold overrides. Full buyer authority on every line sounds safe but stalls the moment you are unreachable; full assembler authority resolves quickly in the direction that suits the assembler.

We paid for MOQ overage. Why did the repeat order charge us again?

Because paying for material and owning it are separate outcomes, and the second one needs to be written down. State that overage you funded is your property, name where it is held, for how long, and require it to appear in the build's material records. Reel remnants without a named owner stay with whoever is physically holding them.

A part we supplied was defective in the bag. Who pays for the labour?

Whatever the contract says, and if it says nothing this becomes a negotiation. Decide in advance whether placement labour already spent and removal labour still required are billed, absorbed or split. Pair that clause with a stated arrival inspection level, because the dated receipt record is what allows a failure to be attributed to before or after the handover.

Does partial turnkey need a supply rule or a line-by-line assignment?

Line by line. Category rules such as "buyer supplies semiconductors, assembler supplies passives" break on the first crystal, connector, magnetic component or electromechanical part, and the parts that fall between categories are exactly the ones both sides assume the other bought. Annotate a supply owner on every BOM line.

Can PCB168 tell us the lead time and MOQ for our assembly up front?

Not as published figures. The PCB assembly page states that component mix, board design, supply arrangement, quantity and acceptance requirements all affect feasibility and schedule, so lead time, MOQ, test coverage and traceability deliverables are confirmed in the project quotation after engineering review of your files. Submit the BOM, fabrication data, placement data, drawings and your acceptance requirements to get those confirmed in writing.

Sources

PCB168 PCB Assembly (PCBA) product page — quotation inputs, engineering review before release, and the statement that lead time, MOQ, equipment or test availability, certifications, capacity and traceability deliverables are confirmed only in the written quotation or subsequent engineering response.
PCB168 capabilities overview — published process and verification scope.
IPC-A-610, *Acceptability of Electronic Assemblies* — referenced as the common acceptance-criteria framework for assembly workmanship. Cited as an external standard only; no PCB168 class commitment is implied here.
J-STD-033, *Handling, Packing, Shipping and Use of Moisture/Reflow Sensitive Surface Mount Devices* — referenced for the floor-life and moisture-sensitivity concepts behind the arrival and storage clauses. Cited as an external standard only.
IPC-1752A, *Materials Declaration Management* — referenced for the general practice of documented material declaration in BOM records. External standard reference only.

Self-check

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