IllustrationElectronic manufacturing services (EMS) companies build electronic products to a customer's design. They assemble and test circuit boards, program them, build them into enclosures and buy the parts. The customer supplies the design package and keeps the design. An EMS differs from an ODM, which sells designs of its own, and from a design house, which creates the design.
Every hardware startup reaches the point where someone has to build the product in volume. Most hand that work to an electronic manufacturing services provider. This guide explains what an EMS does, how it differs from an ODM and a design house, what files it needs from you, how new product introduction and pilot runs work, and what to check before you sign.
This is an engineering and sourcing summary, not legal advice. IPC standards are paid documents; the details below come from IPC's free guidance and table of contents pages and from the eCFR. All sources were read on November 12, 2026.
What are electronic manufacturing services?
Electronic manufacturing services is the contract manufacturing model for electronics. The customer owns the product and its design. The EMS turns that design into built, tested units, using its own lines, people and supply chain. People also call it contract electronics manufacturing, and the EMS a contract manufacturer.
The scope runs from bare board assembly to a finished, packed product. A board-only job delivers assembled PCBs. A box build adds the enclosure, cables, battery, labels and pack-out. Most providers also buy the parts, which makes them responsible for sourcing to your BOM and for proposing alternates when a part is short.
The EMS does not own your design. It does create things of its own along the way, such as assembly programs, stencils, test fixtures and work instructions. Your contract should say who owns those. The OEM vs ODM guide covers ownership in more depth.
EMS vs ODM vs OEM vs design house: who does what?
The four terms describe who creates the design and who owns it. The rows below are the usual patterns. A contract can change any of them.
| Model | Who designs | Who owns the design | What it does |
|---|---|---|---|
| EMS (contract electronics manufacturer) | The customer | The customer, for the product design. The EMS owns its own process files unless the contract says otherwise. | Builds, tests and ships to the customer’s design |
| ODM (original design manufacturer) | The ODM | Usually the ODM | Sells a design it already has, customized and branded for the buyer |
| OEM (brand owner) | In-house or through a partner | The OEM | Sells the product under its brand and carries the compliance duties |
| Design house or development partner | The design house | Set by the contract; can be assigned to the client | Delivers the design files and early builds, then hands off to production |
A common path for a startup is a design partner first and an EMS second. The design partner produces the schematics, layout, firmware, enclosure and test plan, and builds early units. The EMS then builds that design at volume. Duobay sits in the design-partner row. It is a development company that builds samples and small batches of 10–1,000 units, and it is not an EMS. For how small batches run with us, see how small batches run. For how firmware teams organize embedded programming, see Embedded Programming Workflow for Connected Device Firmware. For choosing between SWD and JTAG debug ports, see SWD vs JTAG: Debug Ports, Connectors and Probes.
What do EMS providers do?
IPC's 2026 guidance for printed board assemblies lists the process steps of a board build and the standard behind each one (IPC Standards Guidance for Printed Board Assemblies, 2026 revision, as of November 2026). Mapped to an EMS, the usual services are:
- New product introduction (NPI). A review of your files for manufacturability, a build plan and the first builds.
- PCB assembly. Solder paste printing, placement, reflow, through-hole soldering and inspection. IPC lists J-STD-001 for soldering requirements and IPC-A-610 for acceptability. See SMT PCB assembly for the steps.
- Programming and test. Loading firmware, then in-circuit, functional and RF tests as your test plan requires. See in-circuit test vs functional test.
- Box build. Enclosure assembly, cables and harnesses, labels and pack-out. IPC lists IPC-A-630 for enclosures and IPC/WHMA-A-620 for cable and harness assemblies.
- Coating, cleaning and rework. IPC lists IPC-CC-830 and J-STD-001 for conformal coating and IPC-7711/21 for rework, modification and repair.
- Supply chain. Buying parts, managing moisture-sensitive parts under J-STD-033, and tracing lots. IPC lists IPC-1782 for manufacturing and supply chain traceability and IPC-1752 for materials declarations.
What does an EMS need from you?
An EMS quotes and builds from a data package. A missing item turns into a question, a delay or a guess. The standards column comes from IPC's 2026 checklist (IPC guidance, as of November 2026); the rest is engineering reasoning.
| Item | What it holds | Related standard |
|---|---|---|
| Bill of materials | Manufacturer part numbers, quantities, reference designators and approved alternates for each line | See the BOM guide linked below |
| Board data | Gerber files or an intelligent data format, drill files, stackup and fabrication notes | IPC-2581 and IPC-2610 for data transfer and documentation |
| Assembly drawings and placement data | Top and bottom views, polarity marks, pick-and-place file, special process notes | J-STD-001 class for soldering requirements |
| Acceptance criteria | The workmanship class each assembly is built and inspected to | IPC-A-610, Class 1, 2 or 3 |
| Firmware and programming procedure | Released image, version, programming method and how to verify it on the line | Your release process |
| Test specification | What each station measures, pass limits, fixture drawings and test software | Your test plan |
| Mechanical and box build | Enclosure drawings, assembly sequence, torque, adhesive and label specs | IPC-A-630 for enclosures, IPC/WHMA-A-620 for cables |
| Packaging and handling | Pack-out, labels, serial numbers and handling of moisture-sensitive parts | J-STD-033 for moisture-sensitive devices |
The BOM is where most early questions come from: missing manufacturer part numbers, parts at end of life, and no approved alternates. Read the BOM guide before you send a quote request.
Pick the IPC class
IPC defines three product classes with rising performance requirements and testing and inspection frequency (IPC guidance, as of November 2026):
- Class 1, general electronic products. The major requirement is function of the completed assembly.
- Class 2, dedicated service electronic products. Continued performance and extended life are required, and uninterrupted service is desired but not critical.
- Class 3, high performance or harsh environment products. Equipment downtime cannot be tolerated and the product must work when required.
The acceptability standard on IPC's table of contents page is IPC-A-610J, dated March 2024. It supersedes revision H from September 2020 (IPC-A-610J table of contents, as of November 2026). Name the revision and the class on the drawing and the purchase order, so the EMS inspects to the same line you expect.
How do NPI and pilot runs work with an EMS?
The order below is typical. Names and gates differ by provider.
- Quote and DFM review. The EMS reads your package, flags parts and features that are hard to build, and prices the job.
- First build. A small run that proves the line can build and test the design. Check the first units with a first article inspection.
- Pilot run. A larger run on production fixtures and processes, which shows yield and test escapes. Sampling plans such as AQL are agreed here.
- Changes. Fixes found in the pilot go through an engineering change order, so both sides build the same revision.
- Ramp. Volume production, with the test plan, traceability and change control already running.
These steps line up with the EVT, DVT and PVT builds of a hardware program. See EVT, DVT and PVT for what each build should prove.
How do you choose an EMS provider?
Price per unit matters, and a low quote with weak test coverage can cost more in returns. Check these points:
- Quality system. Ask which quality management certification the site holds and see the certificate and its scope.
- Standards. Which IPC standards and revisions the line builds to, and whether operators and inspectors are trained on them.
- Test coverage. Which tests run on every unit, and which faults each one can and cannot catch.
- Traceability. Whether a serial number leads back to part lots, machine data and test results.
- Change control. How part substitutions are proposed and approved.
- Fit with your volume. A line set up for very large runs may not give a small order engineering attention.
Compliance stays with you. Under 47 CFR 2.909, the party that holds an FCC grant of certification is responsible for the equipment's compliance. If another party modifies the equipment without the grantee's authorization, that party becomes responsible (eCFR 47 CFR 2.909, as of November 2026). So an unapproved antenna or RF part swap at the EMS is a compliance problem as well as a quality one. Lock RF parts in the BOM.
What should you ask an EMS before you sign?
- Which IPC class will you build and inspect our boards to, and is it written on the purchase order?
- What does your NPI review cover, and what DFM report do we get back before the first build?
- Which tests run on every unit, and what share of the board does each one cover?
- Who designs, pays for and owns the test fixtures and programming jigs?
- How do you trace a unit back to component lots and process data?
- How do you handle part substitutions, and who approves them?
- Which changes trigger an ECO on our side, and which do you treat as process changes?
- What happens to our files, stencils and fixtures if we move production elsewhere?
Questions about electronic manufacturing services
What does EMS mean in electronics?
EMS stands for electronic manufacturing services, also written electronics manufacturing services. An EMS company builds electronic assemblies and finished products to a customer’s design: board assembly, programming, test, box build and parts purchasing. Contract electronics manufacturing is another name for the same model.
Does an EMS provider design the product?
Not as its core service. An EMS expects a finished design package. Many offer DFM reviews that suggest layout or part changes for their process, and some offer engineering services on the side. Agree in writing who owns any design work they do.
What IPC class should a consumer device use?
IPC describes Class 2 as dedicated service products where continued performance and extended life are required and uninterrupted service is desired but not critical (IPC guidance, as of November 2026). Many consumer devices fit that description. Class 3 is for products where downtime cannot be tolerated. State the class on the drawing either way.
Who is responsible for FCC compliance when an EMS builds the product?
For certified radio equipment, 47 CFR 2.909 makes the grantee responsible for compliance. A party that modifies the equipment without the grantee’s authorization becomes responsible for it (eCFR, as of November 2026). Building to your released design does not move that duty to the EMS.
How does Duobay relate to an EMS?
Duobay is a development company. Its Shenzhen engineering team designs the electronics, firmware and enclosure, and builds samples and small batches of 10–1,000 units. Firmware source and the SBOM are delivered to you, and source files are assigned to you at every paid gate, so the package an EMS needs is yours. We do not publish prices, and initial calls are free. Tell us about your device.
If you need the design, samples and a clean package an EMS can build from, tell us about your device.
Sources. All pages accessed November 12, 2026. Standards are revised, so confirm current revisions before you specify them.
- IPC (Global Electronics Association), IPC Standards Guidance for Printed Board Assemblies, 2026 revision (link)
- IPC, IPC-A-610J Acceptability of Electronic Assemblies, table of contents, March 2024 (link)
- eCFR, 47 CFR 2.909 Responsible party (link)
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