What two days can establish. That the equipment exists and is running, that the process route is complete in one building or honestly described as split, that the lot in progress carries a work order you can trace, and that the people running the line can answer a technical question without fetching a manager. That is a lot — it removes the category of supplier that is a broker with a rented conference room.
What it cannot establish. Yield on your stack-up, on-time delivery across a year, financial health, labour compliance, or whether the engineer who qualified your process will still be employed in eighteen months. A visit is a point measurement; those are trends.
The one rule that makes the visit work. Bring the documents with you — quotation, drawing, certificate numbers, the company’s own website printout — and compare them on site. A visit without the paperwork is a tour with better lighting.
Ask for these by e-mail, in writing. What you receive, and how fast, is the first datapoint of the audit — before you have left your desk.
| Document | What it is for | What a poor answer looks like |
|---|---|---|
| Business licence copy | Match the legal name and USCC to the entity that will invoice you | A licence for a different company, or a scanned photo with the USCC unreadable |
| Certificate numbers | ISO 9001, IATF 16949 if automotive, UL file number — with the issuing body | Certificate PDFs with no numbers, or numbers you cannot find in the registry |
| Process capability sheet | Layer count, minimum line/space, copper weight, board thickness range, maximum panel size | A marketing PDF with adjectives and no numbers |
| Equipment list | Drill, plating, AOI, electrical test, impedance test — by brand and count | A list with no model numbers, or equipment the plant no longer runs |
| Your quotation, on their letterhead | The numbers you will check against the shop floor | Numbers that change between the e-mail version and the visit |
| Site address in Chinese | Give it to the driver; compare it to the licence and to the website | An address that differs from the licence — this happens more than you would expect |
Address mismatch is a real finding, not a detail. In this directory, one plant’s registry address has moved twice in fourteen months while the group’s own contact page still prints the pre-2025 address, and the English business directories copied the old one. Another plant had no website at all and its registered domain resolved only for mail. If the address on the licence, the website and your invitation are three different places, resolve that before booking the flight — the difference is often a sales office versus a factory.
Walk it in process order, in one direction, without skipping. If the plant cannot give you a continuous route, ask which steps are done elsewhere and by whom — that answer is one of the most useful things you will learn all day.
| Station | What to look for | What to ask |
|---|---|---|
| Goods-in and material store | Laminate stored flat, on racks, with grade and date marked; copper foil sealed | Which laminate brands are in stock, and which one is on my quotation? |
| Inner-layer imaging and etch | Clean-room discipline, film registration, etch line running or idle | What line/space is routine here, and what is the limit you quote reluctantly? |
| Lamination / press | Press cycles logged, build-up sheets posted, coupons retained | May I see the build-up sheet for the last lot of a 6-layer board? |
| Drilling | Drill count and brands, tool-life records, stack height | How many spindles, and what is the smallest via you drill in production? |
| Plating and PTH | Line chemistry logs, thickness measurement records | How is plated thickness verified, and how often? |
| Outer-layer, soldermask, legend | Registration accuracy, mask thickness, cure records | Which finishes run in-house, and which are outsourced? |
| Surface finish | Whether the finish on your quotation is actually installed here | Is ENIG in-house, or sent out? If sent out, to whom? |
| Electrical test | Flying probe or fixture, net coverage, pass/fail records, rework loop | What is the test coverage on my board, and where does a failure go? |
| Final inspection and packing | Lighting, AVI/AOI, sampling plan, vacuum packing | Which acceptance class is applied, and who signs the release? |
| Despatch | Finished goods labelled with lot numbers, shipping marks, carton counts | Who prepares export documents, and under which entity? |
At each station, one question does more work than any other: “show me the record for the last lot.” Not the procedure — the record. A factory that can produce a filled-in record within a minute is running a system. A factory that produces a blank form is running a template.
Photograph numbers and dates, not machinery. Machinery photographs all look the same and prove nothing.
This is where a factory’s real capability shows. Flying probe with a queue and a rework loop beside it means boards are actually tested. A test room with one machine and no queue, in a plant claiming high volume, means testing is sampled — ask what the sample is.
Watch an inspector work for two minutes. Which defects do they look for, and against which standard? If the answer is “whatever the customer complained about last time”, there is no acceptance class in force, whatever the quotation says.
Every factory has one. Ask what the scrap rate was last month for a board like yours, then ask to see the record. A plant that tracks scrap by lot can answer in a minute; a plant that does not will answer with a percentage that has no source.
Secondary containment, labels, and a manifest for waste leaving the site. This is where environmental findings originate — a provincial enforcement notice in this directory recorded copper discharge at 347 times the standard at a plant that had been operating for a decade.
Cartons, shipping marks and a packing list tell you who the plant actually ships for. Ask to see one shipping mark from last week — not because it names your competitor, but because it shows the plant exports in its own name rather than through a trader.
The most common gap between a visit and reality is that the board you saw is not the board you will get. Three checks close most of it:
Bring these four numbers to the plant and check them on site. Any gap is a question, not necessarily a deception — but a gap you did not check is a gap you will discover in production.
| On the quotation or website | Where to check it on site |
|---|---|
| Layer count and capability ceiling | The build-up sheet at the press, and the work orders in progress |
| Monthly capacity (m² or panels) | Finished-goods movement and the number of shifts actually running |
| Certification scope | The certificate wall — read the scope line, not the logo |
| Headcount | Count workstations on the floor against the insured headcount in the registry |
One number is worth calculating on the plane home: square metres of board per insured employee. In this directory’s twelve profiled plants the range runs from about 1,000 to about 13,500 m² per person-year — a thirteen-fold spread inside one Chinese prefecture. A capacity claim outside that range is not necessarily wrong, but it needs an explanation you heard in person.
Write it the same evening, before the impressions fade into politeness. Eight lines:
One full production day is enough to walk the route and watch a shift change; two days lets you see a different product run the second morning and compare. Less than one day means you see the conference room, one clean line and a sample wall — a presentation, not an audit.
Things that carry a date or a number: work-order cards, panel labels, AOI defect maps, calibration stickers, finished-goods labels, and the certificate wall with numbers legible. Machinery photographs prove nothing.
For the walk-through, often not — process steps are visible and equipment is labelled in English. For the questions that matter, yes: what a work-order card means, why a lot is on hold, how scrap is recorded. Without translation you are auditing the sales team, not the factory.
Yield on your stack-up, on-time delivery across a year, financial health, labour compliance, and whether the engineers who qualified your process will still be there next year.
After the quotation and before the production order. The visit is where you check whether the quotation was written for the plant you are standing in — visiting before you have a quote gives you nothing to compare against.
This checklist describes what to look at, not what a given plant will show you. It does not replace a formal process audit against a customer-specific standard, and it is not a substitute for first-article inspection: a visit verifies that equipment exists and runs, and a first article verifies that it runs on your design.
The estimates in section 6 come from the twelve published profiles in this directory and are stated as ranges, not benchmarks. Where this guide and a plant’s own documentation disagree, the documentation wins and the disagreement is the finding. Last reviewed 1 November 2026.