Capacity is the one thing every supplier claims to have and almost no supplier will quantify. Ask an account manager whether there is room for a quarterly volume and the answer is yes. Ask what that means in panels per week, on which line, with what changeover allowance, and what happens if a larger customer arrives in July, and the answer becomes a conversation about relationships.
This guide is about converting that conversation into something you can rely on. It covers what a factory can genuinely commit to and what it cannot, the two different things buyers mean by "capacity", the seasonal calendar that decides whether your commitment survives the year, the clauses that make a commitment enforceable, and the verification that tells you whether the commitment was kept.
What a Factory Can Actually Commit, and What It Cannot
Before negotiating a reservation it helps to know which constraints are real. A PCB and assembly factory has three separable capacity models, and only one of them is usually worth reserving.
- Fabrication capacity, measured in panels. Driven by drilling, plating and lamination. Reservation here means panel area per week on a specific technology — layer count, copper weight, minimum drill. It is the most meaningful commitment for a bare-board programme, because the constraint is machine hours with a long queue.
- Assembly capacity, measured in placement hours or boards per shift. Driven by the number of SMT lines, the placement rate of the bottleneck machine, and — critically — changeover time. This is what a supplier usually means by "we have capacity", and it is the least stable commitment, because a high-mix line's capacity is mostly a function of how many products are queued on it.
- People and test capacity. Hand assembly, inspection, test, conformal coating and box-build are labour-bound. A supplier can reserve line hours and still fail to deliver because the test bench or the coating operator is shared across ten customers.
A commitment that names only the first two is incomplete. The practical specification should also state the downstream constraint: how many units per week can pass final test and packing on the reserved volume, not just how many can be placed.
Two Things Buyers Mean by "Capacity Reservation"
The confusion that sinks most capacity discussions is that the same phrase covers two different commercial arrangements with completely different obligations.
| Arrangement | What the supplier gives up | What the buyer must give |
|---|---|---|
| Scheduling priority | Queue position only; no line is held | Nothing structural — this is a courtesy, not an asset |
| Hard reservation | Actual machine-hours or panel area held idle if unused | A minimum monthly take-or-pay volume, or a standing charge |
| Material reservation | Laminate and components bought against forecast | Forecast liability, cancellation windows, sometimes prepayment |
Most "reservations" offered to a mid-size buyer are the first row presented in the language of the second. That is not necessarily dishonest — a supplier with a healthy book genuinely does give regular customers priority — but it has no legal content. If nothing is being held and nothing is being paid for, there is nothing to enforce in a shortage.
A real hard reservation is priced. The supplier is declining other work to hold the slot, so a take-or-pay floor or a standing charge is the fair structure: you pay for capacity whether or not you use it, and in exchange it is there when you need it. Buyers who are unwilling to pay for reserved capacity should not expect to receive it in the quarter when everyone else wants the same machine.
The Calendar That Decides Whether the Commitment Survives
Capacity commitments fail on a predictable calendar, and a reservation negotiated without reference to it is a document written for the wrong months. In the Shenzhen and Pearl River Delta manufacturing base, three periods dominate the year.
- Chinese New Year, late January to late February. The single largest disruption. Assembly lines run far below normal for two to four weeks around the holiday, with labour returning gradually rather than on day one. Anything promised for delivery in the two weeks before and four weeks after CNY is at risk regardless of what the reservation says. Our Chinese New Year sourcing guide covers how to pre-build against it.
- The Q3 pre-peak squeeze, roughly July to September. Western retail customers ramp for the fourth-quarter selling season, and the same factories are filling consumer-electronics orders. This is the period when a soft scheduling priority evaporates and a hard reservation earns its cost.
- Pre-holiday export congestion, October to mid-November. Capacity is often available but shipping is not. A board that ships on time but sits in a port for three weeks has the same effect as a late build. That is a separate planning problem, covered in the Incoterms and shipping guide.
The practical implication: the reservation should be written with the calendar in it. A commitment of "X panels per week" with no statement about CNY and no peak-season priority is a commitment for February and October, when capacity is plentiful, and for nothing when it matters.
What to Ask Before Signing a Commitment
Seven questions separate a real commitment from a polite one. The answers should be specific enough to write down in the agreement itself, not paraphrased in a follow-up email.
- How many panels per week, at which technology? Layer count, maximum copper weight, minimum mechanical drill, surface finish. A reservation for 6-layer 1 oz boards does not transfer to 12-layer 2 oz, and the supplier's constraint is per technology family.
- Which line, and what else runs on it? The material point is not the line number but what share of the line's scheduled time is contractually yours and what share is shared with other programmes.
- What changeover allowance is included? On a high-mix line, a stated weekly quantity is meaningless without stating how many changeovers per week it assumes. Two products running alternate weeks deliver materially less than one product running continuously, and the changeover reduction techniques that close the gap are usually the cheapest capacity a supplier can add.
- What is the reallocation rule? The question that decides everything in a shortage: if another customer needs the same slot, who wins, and what notice must you receive? A commitment with no stated rule is a commitment to be asked nicely.
- What happens if the buyer falls short of forecast? Take-or-pay terms, shortfall charges, and the grace period before they are applied. This is the price of the reservation and should be negotiated explicitly rather than discovered on an invoice.
- How is material secured against the reserved volume? Reserved machine hours with unreserved laminate is not a reservation — it is a placeholder. Ask how much of the committed volume is covered by material already bought or on order, and at what lead time.
- Does the commitment survive a technology change? A design revision that adds two layers or moves to a heavier copper weight resets the capacity question. The agreement should say so, so the conversation happens once at the start rather than per revision.
Factory reality: the commitment that holds in practice is rarely the largest one. A supplier who states a smaller number with a stated reallocation rule and a named peak-season priority will beat one who agrees to a round figure with no conditions, because the second number was never a forecast of anything.
Verifying the Commitment Was Kept
A capacity agreement without measurement drifts within two quarters, usually without anyone deciding to break it. Three indicators are enough, and all of them can be derived from records the buyer already has.
- On-time delivery against the commitment, by month. Not against the supplier's own promised date, which is itself an output of available capacity, but against the date the reservation implied. A commitment of panels per week translates into a latest ship date; measure against that.
- Reserved-versus-actual utilisation. If you reserved 20% of a line and consistently used 8%, you are overpaying and the supplier knows it — which weakens your position when you later need to raise the floor. Right-size the reservation annually rather than letting it slide.
- Exceptions with reasons. Every missed week should carry a coded reason: material, machine, labour, quality hold, or another customer taking precedence. A pattern in the codes is the real signal — repeated "labour" in the first half of a month points at staffing, while repeated "other customer" means the reallocation rule is not being applied.
These numbers should be reviewed with the supplier on a schedule, not during a crisis. A quarterly capacity review that puts delivery performance, utilisation and forecast variance on one page turns the agreement from a document into a working relationship — and it is also the moment to raise a forecast change before it becomes a shortage. Where the constraint turns out to be a single component rather than line time, the mitigation toolset is different and is covered in our component shortage mitigation guide.
Where Reservation Sits Among Your Other Leverage
Capacity reservation is one of three related commercial mechanisms and is often the wrong one to reach for first. Distinguishing them prevents overpaying for the wrong guarantee.
- Blanket order with scheduled releases. Commits volume and price over a period, with delivery dates released call-off by call-off. It secures pricing and gives the supplier a forecast to build against; whether it secures capacity depends entirely on whether the reservation language is in it. The trade-off is covered in blanket orders versus spot buys.
- Consignment or vendor-managed stock. Moves inventory to the supplier's premises or a hub near you, which protects against demand spikes but not against line-time scarcity. Useful where the risk is demand volatility rather than capacity, as set out in VMI and consignment stock.
- Dual sourcing. A second qualified supplier is the only true insurance against one factory's capacity failure, and it costs qualification time plus a split volume. Whether the insurance is worth the cost depends on what a stockout costs you, which is the subject of dual sourcing strategy.
Most programmes need one hard mechanism and one soft one: a reservation or blanket schedule with the supplier who carries the majority, and a qualified second source that can absorb a defined emergency share. Buying both from the same supplier is not diversification regardless of how the paperwork reads.
At Huaxing PCBA, capacity commitments are quoted in panels per week against a named technology and stated in the quotation, with the changeover assumption, the reallocation rule and the CNY window written into the same document. 8 SMT lines and 32-layer fabrication capability mean the constraint can be named rather than implied, and monthly delivery-versus-commitment reporting is issued with the shipment documentation. Send your forecast and technology mix for a capacity quote, or ask an engineer which of your volumes can realistically be reserved before the Q3 window.
