PCB assemblies are ordered by sending the supplier the Gerber files, BOM, CPL, quantity, assembly notes, testing requirements, and approval rules before production starts. The supplier then checks the files, reviews component availability, confirms SMT and through-hole requirements, quotes the build, and waits for buyer approval before assembly.
The ordering process becomes difficult when the buyer sends a BOM without placement data, a CPL without rotation notes, or Gerber files that do not match the board revision. A good assembly supplier will slow down for file review before building because one wrong polarity mark or unmatched footprint can turn a simple SMT order into rework.
What Happens Before a PCB Assembly Order Is Placed?
Before a PCB assembly order is placed, the supplier should review the bare board files, component list, placement file, assembly notes, quantity, and test expectations. This review confirms whether the project is ready for quotation or whether the buyer needs to clarify missing details.
The practical order path is simple: submit files, receive questions, confirm substitutions and process scope, approve the quote, review the sample or first article when needed, then move to production. If your project is not ready for mass production, a Prototype PCB Assembly path is usually safer than rushing directly into volume.
Which Files Are Needed to Order a PCB Assembly?
To order a PCB assembly, you normally need Gerber files, a BOM, a CPL or pick-and-place file, assembly drawings or notes, quantity, testing requirements, and any component sourcing rules. Each file answers a different production question.
| File | What it controls | Buyer check |
|---|---|---|
| Gerber | Bare board manufacturing and reference layers | Revision matches the BOM and CPL |
| BOM | Component sourcing and assembly cost | MPN, package, quantity, substitutions |
| CPL | XY location, rotation, and board side | Rotation and polarity are correct |
| Test notes | Inspection and functional validation | AOI, X-ray, ICT, functional test scope |
How Do BOM, CPL and Gerber Files Work Together?
The BOM tells the supplier what parts to place, the CPL tells the machine where and how to place them, and the Gerber files show the PCB layout those parts must fit onto. These files must describe the same board revision.
If the BOM says a component uses a 0603 package but the footprint on the board is 0402, the order cannot be trusted. If the CPL rotation is wrong, polarized parts can be placed incorrectly. If the Gerber files are from a previous revision, even a correct BOM may not match the actual PCB.
What Should the Supplier Check Before Quoting?
Before quoting a PCB assembly order, the supplier should check BOM risk, component availability, package compatibility, polarity, placement data, board finish, assembly side, and inspection requirements. This protects the buyer from a quote that looks complete but leaves production risks unresolved.
For SMT-heavy projects, the supplier should also review fine-pitch parts, BGA packages, moisture-sensitive components, special reels, and any parts that need X-ray or functional testing. If the design uses BGA, the quote should mention whether BGA Assembly inspection such as X-ray is required.
Turnkey vs Consigned Assembly: Which Ordering Path Fits Your Project?
Turnkey assembly means the supplier sources components and assembles the boards; consigned assembly means the buyer supplies some or all components. The better path depends on component control, sourcing risk, schedule, and buyer responsibility.
Turnkey PCB Assembly can reduce coordination work because the supplier handles procurement and assembly together. Consigned assembly can work when the buyer already owns critical parts, restricted parts, programmed devices, or components with approved vendor control. Mixed sourcing is also common, but it needs clear responsibility for shortages and substitutions.
What Testing and Inspection Requirements Should Be Confirmed?
Testing requirements should be confirmed before production, not after boards are assembled. AOI, X-ray, electrical testing, programming, and functional testing all affect process time, fixture needs, cost, and acceptance criteria.
For standard SMT, AOI may be enough for many visible solder joints. For BGA, QFN, bottom-terminated components, or hidden solder joints, X-ray may be needed. Functional testing requires a test method, expected result, firmware or software when needed, and a decision rule for failed units.
What Can Delay a PCB Assembly Order After You Submit Files?
Most PCB assembly delays come from missing files, unavailable components, unclear substitutions, mismatched revisions, polarity questions, and unconfirmed test requirements. These issues are easier to solve before the quote is approved.
- BOM part numbers are obsolete or out of stock.
- CPL rotation does not match the assembly drawing.
- Gerber, BOM, and CPL revisions are inconsistent.
- Substitution rules are not approved.
- Testing requirements are added after the quote.
- Component packaging is not suitable for automated SMT placement.
How Should Buyers Review a PCB Assembly Quote Before Approval?
Before approving a PCB assembly quote, check whether component sourcing, SMT scope, through-hole work, inspection, testing, lead time, and responsibility for substitutions are clearly stated. Do not approve a quote just because the total price is low.
Review the quote line by line. Confirm whether the bare PCB is included, whether components are included, whether losses and spares are included, and whether the quoted lead time depends on component availability. If the quote does not mention the test scope, ask before production starts.
How QFPCB Supports PCB Assembly Ordering and BOM Review
QFPCB is a fit when a buyer needs PCB assembly support that connects BOM review, SMT process planning, testing scope, and production quotation. This is especially useful when the project has mixed sourcing, fine-pitch components, BGA parts, prototype builds, or unclear test requirements.
If you are preparing a PCB assembly order, send QFPCB your Gerber files, BOM, CPL, quantity, assembly notes, substitution rules, and test requirements at [email protected]. The team can review BOM risk, SMT process needs, inspection scope, and quotation assumptions before production. You can also start from the PCB Assembly service page or contact page when you need a formal RFQ path.
FAQ
Can I order PCB assembly without a CPL file?
It is risky. A CPL file tells the assembly team the XY location, rotation, and side for each part. Without it, the supplier may need to rebuild placement data manually, which increases delay and placement risk. If the board is simple, the supplier may help, but it should be confirmed before quoting.
Do I need Gerber files if I only want assembly?
Yes, the assembly supplier still needs Gerber files or equivalent board data to check pads, silkscreen, polarity marks, fiducials, tooling rails, and board revision. Even when the bare PCBs are supplied by the buyer, the assembly team needs layout context.
What is the difference between SMT assembly and PCB assembly?
SMT assembly is one part of PCB assembly. It places surface-mount components on the PCB, usually using solder paste, pick-and-place machines, reflow, and AOI. PCB assembly can also include through-hole parts, hand soldering, programming, testing, and final inspection.
Should I choose turnkey assembly for a first order?
Turnkey assembly can be easier if you want the supplier to source components and manage the build. For a first order, it works best when the BOM is complete and substitutions are allowed. If you own critical components or programmed parts, a consigned or mixed model may be safer.
