Oct 20, 2026Sourcing Guides
PCBA Manufacturing in China: What to Verify Before the First Production Run
A BOM can look complete and still leave a first run exposed. The checks we would run before releasing a PCBA order, from alternate parts to the payment gate.
A BOM arrives as a spreadsheet with a board tab, a parts tab and a test-notes tab. The quote comes back cheaper, with part numbers swapped and nothing in the notes to say so. The bare board is quoted by one supplier, the assembly by another, and each assumes the other is covering the gaps. The first run is where those assumptions meet.
The people behind B&C Sourcify work out of Shenzhen and came up through a family sheet metal business, with mold work and circuit-board assembly on the same supply chain today. The sequence before a first production build is fixed: BOM revision, the bare-board and assembly boundary, first article and frozen programs, solder and test records, packing spec, and the payment gate behind change control.
The BOM Revision Is the First Gate
A BOM without a revision number is a moving target. The quote looks settled, the parts list behind it does not, and the first run is where the difference lands. So the first document we ask for is the revision the quote was built on, not the quote on its own.
What has to be on that revision: manufacturer part number, package, quantity and approved alternates. Alternates belong on a list with its own revision, not in a salesperson's memory. Before production, the engineering review should cover component availability, so the BOM that reaches the line is one that can be bought at the quantity ordered.
No substitution runs on a verbal yes. An alternate needs the part number it replaces, the reason, written approval and a check against the approved sample. Before mass production, two physical samples are signed, stamped and sealed, one held at the factory and one with us, and that is the reference a substitution is measured against.
Lot codes belong in the same conversation. If a supplier swaps a part, the lot record is what lets you say which units carry it later.
Ask these before the quote is accepted: which revision the price is built on, which alternates are approved, who signs a substitution, and which lot codes will ship. Same spec with no part number behind it is not an answer. Closest available with no approval is not one either.
The order should carry the revision and the alternates list, with a named signer for any change. The route from a first drawing to a production line has its own playbook. The checks here stop where the BOM is released.
Where the Bare Board Ends and the Assembly Begins
The same BOM can go out under turnkey, consignment or mixed terms, and the price means something different in each. Under turnkey, one supplier buys the bare boards and components and builds the assembly. Under consignment, material you or another factory supplies arrives at the assembler's door. Mixed orders split the material between the two, and that split is where first-run arguments begin.
The first thing we ask for is a map of the stations. The service flow runs PCB fabrication, SMT, through-hole and box build, and each station can sit inside this quote or outside it. A quote that leaves box build out is not a bad quote. It is a bad quote when nobody says what it leaves out.
Incoming material is the next line to draw. Who buys the bare boards, who buys the components, who inspects what arrives, and who carries a defect found at incoming? If a panel arrives bent and the assembler finds it, the answer decides whose claim it is. The test specification has the same owner problem. An assembler can run a test, but someone has to define what passing means.
The engineering review before production is where the boundary either closes or stays open. DFM, component availability and test coverage get settled there, and a review that ends with questions has settled nothing. The handover point follows the same map. Ask where responsibility starts and where it stops, station by station.
Ask which stations the price covers, who inspects incoming material, and where the warranty starts and stops. Which risks you accept is your commercial call. The answers above belong in the order, not in a call.
The service flow, from PCB fabrication to box build, is set out here (/industry/pcba-electronics-manufacturing-services). Single-product electronics builds have their own guides; this piece stays at the PCBA order gate.
What the First Article Record Has to Prove
A first article is not a sample sent to show that one board works. It is the record of the build that the rest of the run gets compared against. Read as a sample, it proves one board can be made. Read as a record, it proves the process was defined before the run started.
The record should name what was released: the BOM revision, the PCB revision, the stencil revision, the placement program version, the test procedure and the firmware version where firmware is part of the build. Measurements belong on it, the positions of defects belong on it, and so do the signatures.
Freeze the stencil and the placement program first. After that point, a change becomes a change order; a later section here covers the mechanics. A run that starts on one program and finishes on another has no first article at all. It has two builds and one document that describes neither.
Compare the record against the documents: a revision on the record that does not match the order is a gap. Compare it against the approved sample, the physical reference for acceptance. The pre-shipment comparison of PCBA solder joints is a later checkpoint, and it does not stand in for the first article. One asks whether the process was set up correctly. The other asks whether the run held.
When the record arrives, what we read first is which revisions were used, who signed it, and what changed after the signature. If the answer to the last one is nothing, ask to see the program version and the stencil label. A photo of a board with no revision trail is a picture, not a record. First article passed, with no measurements, is a sentence, not a record.
The order should name the revision set: which BOM, which board, which stencil, which program, which test procedure. Then the first article has something to be measured against.
Solder Joints and Functional Test: Evidence a Buyer Can Read
Two records carry this part of the order: the solder-joint record and the functional test record. Both have to be readable by someone who was not on the line, and the reader is a buyer on another continent.
The solder-joint record should say what was inspected, who inspected it, what the inspection was measured against, and where defects were found. Visually checked and a signature is not that record. Where rework happened, the retest sits beside it. A repaired joint that was never retested is an open question with a shipping date attached.
The functional test record has the same shape. What does the test exercise, what are the pass and fail limits, which serial numbers went through it, and what happened to a unit that failed the first time? Powered functional testing is part of our PCBA service, and the record is what makes the test worth running.
Coverage is the other half of the question. Before production, the engineering review should settle which functions the test covers and which it leaves to inspection, so nobody assumes a power-on check proves a display or a connector. Saying it powers on is not a functional test. It is a power supply check with a good outcome.
We ask for one passing record and one failing record. The passing one shows what a release looks like. The failing one shows what the test can catch and what happened to the board afterwards. Factory QC sits on a separate line, and it answers a different question from this one.
The order should name the records: a solder inspection record, a retest record for every reworked board, and a functional test log by serial number.
ESD and Packing: What the Order Must Say
ESD is a handling discipline before it is a bag. A board that leaves the line healthy and arrives with a dead input may have been damaged in handling, bagging or stacking, not in the design.
We ask for the packing specification, not the word anti-static. Which bag, whether a moisture barrier goes around it, how much desiccant, how the edges and connectors are protected, how high a carton stacks, what the label says, and how many units go in each carton. Any board that ships with a plug or an accessory gets those specifications on the same line.
The sealed sample and the pre-shipment comparison hold the packing spec in place. The sample shows what good packing looked like when it was signed off. The comparison, where appearance, material, dimensions, solder joints and plug or fitting specifications are checked item by item, shows whether the carton matches it. A packing spec that nobody checks is a preference.
Moisture is the part buyers forget. A board in a sealed bag with no desiccant, or in a barrier bag that was opened and closed again, may have lost most of its moisture protection. The bag only looks like protection.
Ask which parts on the board are ESD-sensitive, what the packing sequence is, and who signs the packing spec. Refuse anti-static with no bag specification, and refuse boards loose in a carton with a sheet of bubble wrap laid on top.
The packing spec belongs in the order as a line with its own revision, the way the BOM has one.
ECN and the 30/70 Gate: Change Control Meets Payment
An ECN is a controlled change, and an email is not one. The document has to answer which BOM revision the change lands on, which stencil or program version it replaces, what happens to the boards already in process, and who absorbs the scrap or the rework the change creates.
Effectivity is the word that decides it. A change takes effect from a defined point: a revision, a lot, a date or a serial range. Without that point, two versions live under one part number and nobody can say which units carry the old design.
Verification comes next. When a change reaches the board, the stencil or the program, the order should get a delta first article: the same record as the original run, but on the changed build, so the difference is documented instead of assumed.
The commercial side meets the same gate. Terms are a 30% deposit and a 70% balance tied to the inspection result, and credit terms are not offered here. The pre-shipment comparison that releases the balance has to name the revision it inspected and the approved sample it was measured against. A lot that mixes two revisions needs a written disposition, not a verbal note, saying what happens to each part of it.
We ask which revision this lot is, from which date or lot the change applies, what happened to work in process, and who signed the delta first article. The effectivity rule belongs in the order as well: no change without a revision, an effective point and a named approver.
The checks that happen on the ground around the supplier, from background checks to loading supervision, sit on our sourcing page (/b2b-sourcing).
Open With the BOM You Are About to Release
Bring the revision you intend to release, the split between bare board and assembly, the test requirements and the status of the approved sample. Send all of it to (/contact-us). We read an order the way we read a first build, and what comes back is a first-run verification plan and a quote for the build. Our service is for brands, distributors and importers with yearly purchases of USD 10,000 or more, and our contracting entity is Dore Technology Co., Ltd.
