EMS–TRADE Electronics export trading
Send us your specSend spec
A macro view of an impedance-controlled board cut edge under laboratory light, the copper and dielectric layers reading as fine alternating bands

Service 04 · technical assessment · written by engineers

A written plan from engineers,
not a sales reply.

A supplier's reply arrives as a list of standard codes. Without someone who knows what each one governs, the list is unreadable.

Send us your drawing and BOM What you receive
Own factory
45,000m²
Our own PCB & PCBA factory in Bao’an, Shenzhen — the engineering baseline
Fabrication
1–58 layers
Multilayer and HDI boards, assessed by the engineers who build them
Own people
500+
Staff in that one plant, never counted among the 24 partner sites
Laboratory testing
$300–1,500
Per item for typical CE or FCC scope, contracted and paid by the buyer

01The fear

Nobody technical on my side
can read their answer.

3 error typesall readable in the scope clause
A single technical drawing sheet on a pale surface with a pen, folding dividers and one teal sticky tab FEAR-01

Category error

A process standard quoted as an acceptance standard, a personnel certificate quoted as a factory qualification.

process vs acceptanceperson vs plant
A blank unmarked form on a clipboard with a pen, abstract ruled lines and empty tick boxes FEAR-02

Scope error

A standard quoted without the thickness, the class or the version that makes it mean anything.

UL 94 without a thicknessno class stated
A finished populated board assembly standing on edge with a matte black heatsink and a row of connectors FEAR-03

Omission

No class was ever written into the purchase order, so the factory built to its own default.

PO says nothingfound at inspection
A dim clean room bench with an oscilloscope, a bench power supply, a board assembly under a magnifier and a sealed sample bag FEAR-04

And it looks reassuring

A long list of standard codes reads as thorough. Three error types account for most unenforceable claims.

long listno applicability

02Deliverable · the written assessment

Signed by an engineer,
and yours to keep.

6 partsthe report is issued to you

Third-party evidence is the buyer's own verification, not ours: you choose the laboratory and you contract it.

A macro view of an impedance-controlled board cut edge under laboratory light, the copper and dielectric layers reading as fine alternating bands
DOC-01 The assessment. Every claim in the supplier's reply mapped to the document that actually governs it — and the ones that do not apply, marked.
A single technical drawing sheet on a pale surface with a pen, folding dividers and one teal sticky tab
DOC-02 The class decision. The correct acceptance class for your product, with the reasoning and the exact wording to put on your purchase order.
A production panel of identical boards held in a white inspection fixture with gold pads and a teal solder mask
DOC-03 The optimisation plan. Substitution candidates, cost and class trade-offs, and the parameters where tightening the requirement buys nothing.
A blank unmarked form on a clipboard with a pen, abstract ruled lines and empty tick boxes
DOC-04 The gaps list. Tests, declarations and market approvals still missing for your destination, each one with an owner.
An engineering bench under an inspection lamp with a finished board assembly, a magnifier arm and sample connectors
DOC-05 The scope statement. What the assessment does and does not cover, so nobody reads it as an approval it is not.
A dim clean room bench with an oscilloscope, a bench power supply, a board assembly under a magnifier and a sealed sample bag
DOC-06 The laboratory pathway. Samples submitted under your name, the report issued to you, typically $300–1,500 per item.

03Reference · the document family

Five documents,
five different jobs.

revision dates matterthe user defines the class
A finished populated board assembly for a power supply lying flat on a white engineering bench beside a digital caliper STD-01

Acceptability of the assembly

Revision J, March 2024, 430 pages. This is what an inspector works from — and the class inside it is yours to name.

IPC-A-610JRev J, March 2024
A close view down one SMT line with pick-and-place heads and feeder reels in strict alignment STD-02

The soldering process

Revision J, March 2024, 116 pages. A process document, quoted constantly as though it were an acceptance document.

J-STD-001JRev J, March 2024
A production panel of identical boards held in a white inspection fixture with gold pads and a teal solder mask STD-03

The bare board

Revision M, May 2025, 212 pages: bare-board acceptability. Board requirements live in the 601X documents, and quoting one does not invoke the other.

IPC-A-600MRev M, May 2025
A finished populated board assembly standing on edge with a matte black heatsink and a row of connectors STD-04

Rigid and flexible qualification

The rigid-board specification runs 80 pages. Flex and rigid-flex sit in a separate document, Revision F, released 2026-08-25.

IPC-6012FIPC-6013F, 2026-08-25
Four finished rack-mount network switches in a row with closed faceplates and empty port cages STD-05

Rework, modification and repair

Revision D, December 2023, 286 pages. Rework has its own document; writing “rework permitted” without naming it leaves the method to the line.

IPC-7711/7721DRev D, December 2023
An engineering bench under an inspection lamp with a finished board assembly, a magnifier arm and sample connectors STD-06

What the acceptance document excludes

IPC-A-610J §1.1 gives no criteria for cross-section or X-ray inspection. BGA void judgement is written against IPC-7095 instead.

§1.1 excludes itIPC-7095 governs voids

04Decision layer · the class

Where the class decision
changes the money.

industry guidancenot IPC text
A production panel of identical boards held in a white inspection fixture with gold pads and a teal solder mask CLS-01

Class 2 is the volume default

About 70% of global assembly volume, and the class a factory uses when the purchase order says nothing.

≈70% of volumeindustry guidance
An engineering bench under an inspection lamp with a finished board assembly, a magnifier arm and sample connectors CLS-02

Class 3 costs more

20–40% added assembly cost, associated with 8–15% defect rates against 2–5% for Class 2.

+20–40% cost8–15% vs 2–5% defect
Four finished rack-mount network switches in a row with closed faceplates and empty port cages CLS-03

The criteria you can inspect

Class 2 needs solder wetting on at least 75% of the pad; Class 3 needs a 100% fillet and 75% hole fill.

≥75% wetting100% fillet, ≥75% fill≤1.56 vs ≤0.78 µg NaCl eq./cm²
A close view down one SMT line with pick-and-place heads and feeder reels in strict alignment
Fig. A The envelope the class has to match. Our own line works to 1–58 layers, 0.1 mm trace and space, 0.2–3.2 mm board thickness, 0.15 mm minimum drill and 1–8 oz outer copper — so the assessment is written by engineers who run the same numbers.

05Inputs · what we need from you

Four inputs,
and the review can start.

4 inputsthen a written assessment
A single technical drawing sheet on a pale surface with a pen, folding dividers and one teal sticky tab IN-01

The drawing set

Fabrication drawing, assembly drawing and the layer stack-up, at the current revision.

A blank unmarked form on a clipboard with a pen, abstract ruled lines and empty tick boxes IN-02

The BOM

Manufacturer part numbers, approved alternates, and any second-source you will accept.

A macro view of an impedance-controlled board cut edge under laboratory light, the copper and dielectric layers reading as fine alternating bands IN-03

The supplier's reply

The answer as you received it, badges included. We will mark which parts are unusable and why.

Two finished industrial computers standing side by side on a pale bench, one fanless with heatsink fins and one rack-mount IN-04

The market and the volume

Destination market, annual volume, and the approvals the product must hold there.

06Where it fits

The assessment is
the first written answer.

6 services1 contract

No partner factory is named on this page. Naming one would read as an endorsement; every partner is listed on the network pages.

07Start

Send us your drawing, BOM and target market.

The fuller the package, the faster the review. A photograph of a board takes longer than a drawing set.

Recorded. An engineer will reply.

Written technical assessment, from eric@dfshk.cn.

Book a factory visit eric@dfshk.cn · +86 152 3512 7440