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A bare multilayer board standing on edge on a pale bench, its copper and dielectric layers reading as fine stripes along the cut edge, with a caliper and a drawing behind it

Resources · engineering note · PCB & PCBA

The spec sheet:
what to send us.

Send seven things and a quotation becomes comparable. Here is every field, what it changes, and the numbers the network's board sites build to.

Send us your spec PCB fabrication & PCBA
Layers
1–58
Published envelope of the network's board sites
Trace and space
0.1mm
4 mil. Finer than that is quoted case by case
Hole position
±0.075mm
Finished hole: PTH ±0.08 mm, NPTH ±0.05 mm
DFM review
24h
Free, published by a network PCBA site

01The pack

Seven files. Then three quotes become comparable.

Gerber RS-274XExcellon drillNative source welcome

Every quotation answers the same seven lines, so the difference between them is price rather than paperwork.

What a complete pack contains
FileWhat it decidesAccepted form
Gerber and drillCopper, mask, holesRS-274X plus a separate Excellon drill file
Fabrication drawingOutline, holes, tolerancesDimensions, hole table, tolerance callouts
StackupLayer orderFixed, or the fab's standard build stated
Impedance scheduleControlled netsNet names, target, tolerance
BOMWhat gets placedManufacturer and part number per line
Assembly drawingOrientation and torqueDesignators, polarity, keep-outs, labels
Class and testWhat counts as a passNamed class, and AOI, ICT or FCT

Scroll the table sideways

A dimensioned engineering drawing on a pale sheet with a mechanical pencil and a pair of dividers beside it
Fig. 01The drawing carries the dimensions, tolerances and notes the Gerber cannot.
A dimensioned drawing, a populated green circuit board, a sealed bag of fasteners and a dark ring binder laid out on a pale bench
Fig. 02Drawing, board, hardware, records — the four parts of one pack.
A dimensioned drawing squared to the frame with a digital caliper, a set square and three machined sample parts
Fig. 03One pack, three quotations that can be read line by line.

02Day one

Manufacturing data, not a picture.

Min trace 0.1 mmMin drill 0.15 mmAnnular ring 0.15 mm

A screenshot, a PDF plot or a three-dimensional render cannot be fabricated from. Five things can.

A dimensioned technical drawing on a white sheet with a black pencil and a pair of dividers beside it
Fig. 04The fabrication drawing. Outline with dimensions, hole table, material, finish, thickness and tolerance callouts.
01 Manufacturing data Gerber (RS-274X) or the native source, plus a separate Excellon drill file.
02 The stackup Layer order, dielectric thicknesses, material — and whether it is fixed or the fab's standard build.
03 Impedance, in writing Which nets, which target, which tolerance. Left blank, the fab builds to its default.
04 A contact in your hours A two-day silence on an engineering change is the most expensive delay on this list.
A magnified cross-section of a multilayer board showing alternating copper and dielectric layers and a plated through-hole barrel
Fig. 05The stackup is a physical object: layer order, dielectric thickness and copper weight.
Two people at a white table reading a dimensioned drawing, one holding a pen over the sheet
Fig. 06An engineering-change question answered inside your working day, through the language bridge.

03The build table

The nine-line build table.

1–58 layers0.2–3.2 mm1–8 oz outer copper

Copy this table into your RFQ unchanged, so every quotation answers the same lines.

What our board sites quote against
LineValue or range
Layers1–58
Base materialFR-4 standard; high-Tg FR-4, aluminium and Rogers-class laminates on review
Thickness0.2–3.2 mm in standard steps; ±10% at 1.0 mm and above, ±0.1 mm below
Copper weightOuter 1–8 oz (35–280 µm); inner 1–4 oz
Trace and space0.1 mm (4 mil) minimum; finer is reviewed case by case
Drill and ring0.15 mm minimum drill; 0.15 mm annular ring; PTH ±0.08 mm, NPTH ±0.05 mm
Surface finishHASL leaded or lead-free, ENIG, OSP, hard gold, immersion silver, immersion tin, ENEPIG
Impedance controlControlled, for example ±10% on named nets
Board size and array600 × 1200 mm single and double-sided; 560 × 1150 mm multilayer; V-cut, stamp holes, tab routing

Scroll the table sideways

A gloved hand holding a polished cross-section of a multilayer board under magnification, the plated barrel and copper layers in focus
Fig. 07Layers, copper and thickness are read off a cross-section.
A production panel of twenty identical green circuit boards held in a pale inspection fixture
Fig. 08Panelisation: V-cut, stamp holes, tab routing, and the board gap.
Four identical green circuit boards standing in a black tray beside a small hinged enclosure, a white box and a blank tag
Fig. 09Array and board size decide how the line handles it.

04What each field changes

Four fields buyers leave blank.

FinishMask and legendImpedanceArray

A blank line is where the cheapest quotation hides its substitution.

Field, what to write, and what it moves
FieldWhat you writeWhat it changes
Surface finishENIG, HASL leaded or lead-free, OSP, immersion silverShelf life, joint strength, cost per panel
Solder mask and silkscreenColour, and whether silkscreen is required at allInspection readability and a cost line
Impedance controlNets, target, toleranceWhether coupons are tested, and how the stackup is built
PanelisationV-cut, stamp holes or tab routing, and the gapDepanel stress, handling and material use

Scroll the table sideways

A green production panel on a conveyor entering a placement machine, with a reflow oven and two operators in the background
Fig. 10The array decides how the line handles the panel.
Rows of component reels feeding a line of placement machines receding down a bright assembly hall
Fig. 11The finish decides how the paste wets.

05The BOM

Part numbers, alternates, and what may not be substituted.

MPN per lineTwo alternates75,000 CPH line

A BOM of values is a schematic. A BOM of manufacturer part numbers is a purchase document.

A microscope objective, a sealed bag of teal desiccant beads with a blank label, and a plain white box on a pale bench
Fig. 12Moisture sensitivity and floor life belong on the BOM, not in a phone call after the reels are open.
01 Manufacturer and part number One per line. A value alone cannot be bought, and a package alone cannot be quoted.
02 Two approved alternates Named on every critical line before the order, not chosen at the reel.
03 The no-substitution list Say which lines and why: a comparator, a reference, a footprint, a qualification-critical part.
04 Long-lead items At the top of the RFQ with the lead time stated, not discovered in week three.
Three long rows of identical placement machines seen from a raised viewpoint on a pale factory floor
Fig. 13Minimum component size belongs to a machine, not to a building: a 75,000 CPH line places 0201 and 01005.
A black finned heatsink assembly with a machined bracket and five connectors, photographed square to the camera
Fig. 14Mechanical parts are BOM lines too: heatsink, bracket, connector, fastener.
Sites behind these numbers
Saturn PCBAWhale PCBAUppcbaKingdta

06Assembly and test

The assembly drawing, and the test you want.

AOIICT needs test pointsX-ray points to IPC-7095

Test definition is part of the specification. AOI alone, AOI plus ICT, and AOI plus functional test are three different orders.

A test bench with an oscilloscope, a bench power supply with coloured terminals and a small board on a dark mat under a lamp
Fig. 15Functional test cannot be invented at the factory.
01 The assembly drawing Reference designators, polarity, orientation, conformal-coat keep-outs, heatsink order, torque values, label placement.
02 ICT needs test points Designed in at layout. Asking after the Gerbers are frozen costs a redesign.
03 X-ray is not an A-610 criterion IPC-A-610J section 1.1 excludes cross-sectional and X-ray criteria; BGA void acceptance points to IPC-7095 and your specification.
04 Write the revision, not the word IPC-A-610J (March 2024, 430 pages) for acceptance; J-STD-001J (March 2024, 116 pages) for the process.
Two hands in white sleeves working on a green circuit board with tweezers under a magnifier lamp, six connector samples laid out below
Fig. 16A free DFM read before the order is the cheapest engineering hour you will buy.
A four-shelf rack unit, two machined quick disconnects, a sealed enclosure, a small panel and a coiled security cable in one row
Fig. 17Box build adds its own drawing: what is fastened, in what order, to what torque.

Ask for a written technical assessment against the pack before you place the order.

07Acceptance class

Name the class. IPC assigns that decision to you.

IPC-A-610JRev J, March 2024430 pages

The standard's own sentence: the user is responsible for defining the product class.

Class 2 and Class 3, where they differ
ItemClass 2Class 3
IPC's category nameDedicated service electronic productsHigh performance / harsh environment electronic products
Through-hole wetting (industry guidance)At least 75% of the pad100% fillet wetting, at least 75% barrel fill
Ionic contamination (industry guidance)At most 1.56 µg NaCl eq./cm²At most 0.78 µg NaCl eq./cm²
Inspection coverage (industry guidance)AOI plus samplingAOI plus 100% inspection, full traceability pack
Assembly cost against Class 2 (industry guidance)Baseline+20% to +40%
Published defect band (industry guidance)2–5%8–15%

Scroll the table sideways

Two hands measuring a machined part with a digital caliper above a blank inspection checklist, a bagged sample and a white glove
Fig. 18The class decides coverage, records and price.
A fan of blank checklist sheets with empty tick boxes beside a pen, reading glasses and a small green circuit board in a tray
Fig. 19A first-article report should print its class. If it does not, ask which one was applied.
Two machined metal fittings and a drilled block on a pale bench above two blank sheets of paper and a pen
Fig. 20Written as a clause: built and inspected to IPC-A-610 Class 3 acceptance criteria.
A test rack of finished TFT and OLED display modules in a bright inspection room, every screen lit to the same flat grey field
Fig. 21Every unit powered and looked at is what 100% inspection coverage means in practice.

IPC's wording for Class 2: continued performance and extended life are required, uninterrupted service is not, and the end-use environment would not cause failures.

IPC-A-610 is an acceptability document, not a certificate scheme, and Class 3 is not a military certification.

08The IPC document set

One word, five documents, five lifecycle stages.

DesignBare boardProcessAcceptanceRework

Asking for "IPC" without saying which stage is the most common spec-sheet failure.

Which document governs which stage
StageDocumentWhat it governs
DesignIPC-2221 and IPC-7351Footprints and land patterns
Bare boardIPC-6012F and IPC-A-600MPerformance and appearance of the board itself
ProcessJ-STD-001JMaterials, methods and process control
AcceptanceIPC-A-610JWhat passes: joints, placement, cleanliness, coating
Rework and repairIPC-7711/7721DWhether rework is allowed at all, and to which class

Scroll the table sideways

A closed grey notebook with a fountain pen and a brass rule lying beside it on a white surface
Fig. 22Name the revision in the purchase order, not the family of standards.
The locking bars and hinges of a closed container door with a teal seal through the handle and a document pouch
Fig. 23Rework is a permission, not a default, and it is written into the order.
Three open power supplies standing in front of three open cartons with a clipboard and a pair of white gloves
Fig. 24Every stage produces a record. Ask for the record, not the standard's name.

Revisions as of this writing: IPC-A-610J (March 2024, 430 pp) · J-STD-001J (March 2024, 116 pp).

Also IPC-A-600M (May 2025, 212 pp) · IPC-6012F (80 pp) · IPC-7711/7721D (December 2023, 286 pp).

09Commercial data

Five lines that turn a unit price into a landed cost.

VolumeMarketIncotermHS heading

A pack that stops at the Gerber gets a unit price. These five lines get a landed cost.

An open container with its doors folded back at a loading bay, a steel ramp in place and four palletised cartons waiting beside it
Fig. 25Name the buying term. Our default is FOB Shenzhen; FCA when the container is stuffed inland.
01 Annual volume, first order, and lead time Two numbers, separately. The year buys material; the first order buys tooling and setup.
02 Target markets A US, EU or China-domestic launch is a different test programme.
03 Landed cost and term Give a landed-cost target, not only a unit price. We do not quote EXW.
04 The heading behind your HS code Bare board 8534.00; computer assemblies 8473.30; communications 8517.79; standalone-function boards 8543.70.
05 The rebate line No electronics rebate rate is stated here. Confirm yours with your own broker.
Two rack-mount units standing in front of an open wooden crate with white foam blocking and a document on the lid
Fig. 26Send the boxed dimensions with the board data.
Two workers in blue overalls loading a palletised carton into a container at a warehouse bay
Fig. 27Four headings, four landed costs.

On China the Section 301 stack totals 37.5%; Section 232 semiconductors at 25% has covered 8473.30 since 15 January 2026.

10Questions

The four that arrive with the pack.

Same-day technical readDFM within 24 hNo MOQ at two sites

Short answers, and the reasoning behind each one.

Q1 Can I send a PDF instead of Gerbers? For a DFM opinion, yes. For fabrication, no: send RS-274X plus the drill file.
Q2 Is Gerber enough, or do you want the source? Gerber, drill and the fabrication drawing build the board. The source shortens any change.
Q3 What if I do not know which class I need? Say what the product does and where it is used, and ask for both classes priced side by side.
Q4 How fast can a quote come back? With a complete pack the technical read is same-day; free DFM review is published at within 24 hours.
A warehouse aisle between tall racking loaded with palletised cartons, a teal guide line running down the floor
Fig. 28Finished goods wait on a rack, and the pack is what releases them.
A clipboard holding a blank ruled grid with empty tick boxes, a rolled drawing, a black pen and a green clip beside it
Fig. 29A checked pack is a short quote. A partial pack is a list of questions.
A white meeting table with two chairs, a closed laptop, a small circuit board in a tray and a notebook, beside a tall window
Fig. 30Where the class gets decided: with the buyer, before the order, not at the tester.

11Start

Send us the pack.

Seven files and one line of commercial data. We will read it and say what it builds to.

Recorded. An engineer will reply.

Written technical assessment, from eric@dfshk.cn.

Book a factory visit How to vet a Chinese electronics supplier eric@dfshk.cn · +86 152 3512 7440