IllustrationAn engineering change order (ECO) is the approved instruction to change a released design. It lists what changes and why, which part numbers and file revisions move, when the change takes effect, what happens to existing stock, and who signed off. An ECR proposes the change, and an ECN tells the factory and suppliers to act.
Every hardware product changes after its first build. A part goes out of stock, a test finds a weak joint, or a firmware fix changes how the radio wakes up. The engineering change order is how a team makes those changes on purpose, with the factory and the documents moving together. This guide covers the ECR, ECO and ECN, the ECO package for an electronics product, FCC impact, and change control by stage.
This is an engineering summary and not legal advice. Sources are listed at the end.
What is an engineering change order?
An engineering change order is a numbered, approved record that moves a design from one revision to the next. Once a design is released to a factory, nobody edits the files in place. A change goes through a request, an impact check, approval and a notice, and the ECO is the record in the middle that holds the actual change.
A factory builds from the files it was sent. An ECO gives the change one number and one set of files, so the line, the test station and the buyer work from the same revision. When a field failure appears a year later, the ECO history tells you which serial numbers have which board, firmware and enclosure.
ECN vs ECO vs ECR: what is the difference?
The three documents are steps in one flow. The ECR asks, the ECO defines, and the ECN tells people to act. Usage varies. Some companies call the order itself an ECN, so write your terms down.
| Document | Question it answers | Who usually writes it | What comes out |
|---|---|---|---|
| ECR, engineering change request | Should we change this, and what would it touch? | Whoever finds the problem: test, the factory, support or a supplier notice. | The problem, a proposed fix and a first list of affected items. |
| ECO, engineering change order | Exactly what changes, from which revision to which, and when? | The engineer who owns the design, with review from test, manufacturing and compliance. | An approved, numbered package of revised files. It authorizes the new revision. |
| ECN, engineering change notice | Who needs to know, and what must they do now? | The change owner or document control, after approval. | A notice to the factory, suppliers and internal teams, with the ECO number and effective point. |
A supplier's product change notification (PCN) is a fourth document that often starts the flow. It comes from a part maker to you, and it can force an ECR on your side. More on that below.
What goes in an ECO package for an electronics product?
A connected device adds boards, firmware, test programs and a radio to the usual parts list. A complete package for one change looks like this.
| Item | What it holds | Why it matters |
|---|---|---|
| Header | ECO number, title, owner, date, status and the ECR it answers. | One number the factory quotes on build records. |
| Reason and evidence | The failure, test result, cost target or supplier notice that started it. | The record explains the change years later. |
| Affected items | Every part number, assembly and document that moves, each with its old and new revision. | A missing row is how an old drawing stays in use at the line. |
| BOM delta | Lines added, removed or changed, with manufacturer part numbers and approved alternates. | The buyer and the assembler order from this, so it has to match the files. |
| PCB files | Gerbers or ODB++, drill files, fab drawing, assembly drawing, pick-and-place and stencil data at the new revision. | Each shop needs the set that matches the BOM revision. |
| Firmware | Version number, build ID or hash, release notes, the programming image and an updated SBOM. | The line flashes what the ECO names, and field units can be traced to a build. |
| Mechanical | Changed 3D models and drawings, and any tooling or fixture change. | A mold change has its own lead time and may need new samples before the cut-in. |
| Test and inspection | New test limits, test program version, fixture changes and inspection criteria. | If the test still checks the old design, a bad unit can pass. |
| Compliance check | A written answer on whether the change touches the radio, RF exposure, labels or the FCC ID. | Some changes need a filing or a new grant before the product is marketed. |
| Effectivity and disposition | When the change cuts in, and what happens to stock, work in progress and units already shipped. | Without it, old and new parts mix on the line. |
| Approvals | Who signed, in which role, on what date. | Proof of review before anyone built it. |
Keep each ECO to one problem. A small order is easier to review, test and roll back.
The BOM sits at the center of most changes. How to structure it, set alternates and track lifecycle status is covered in bill of materials for electronics. The firmware and SBOM side, including what a handover should contain after each change, is in the SBOM and source-file handover checklist.
How should an engineering change notice reach the factory and suppliers?
The engineering change notice turns an approved ECO into action. Send it to everyone who touches an affected item: the board house, the assembler, the molder, the packaging vendor and anyone who holds stock.
Set the effective point
State when the change cuts in: a date, a lot or a serial number. A serial number is the easiest to trace in the field. Record the first serial number the factory builds at the new revision.
Decide what happens to old stock
Choose use as is, rework, return or scrap for parts and units at the old revision. Decide separately for loose parts, work in progress, finished stock and shipped units.
Verify the first units at the new revision
Check the first units after the cut-in against the changed drawings and test limits before the line runs at volume. See first article inspection for how that check works.
Supplier notices run the other way
Part makers send their own change and discontinuance notices. TI says its notices comply with J-STD-046 and include the reason for the change, the affected products, qualification results, a sample date and a projected production shipment date. TI says its discontinuance process follows J-STD-048 and allows 12 months for the last order and six more months to take final delivery, with an accelerated schedule possible in rare cases (TI, as of November 2026). Espressif publishes its notices on a PCN page with a subscribe option. Recent entries include ESP32-C5-WROOM-1U BOM Updates and Product Label Change for Espressif Products, both released in 2026 (Espressif PCNs, as of November 2026). Subscribe for each critical part, and route every notice to someone who can open an ECR.
When does a change touch your FCC authorization?
47 CFR 2.1043 sets which changes to a certified radio device need a new grant, which are permissive, and who may make them. The table summarizes the rule text as of November 2026 (47 CFR 2.1043, eCFR).
| Change | What the rule or FCC guidance says | What to do in the ECO |
|---|---|---|
| Firmware change that does not affect RF emissions | 47 CFR 2.1043(a) says such software changes need no additional filings and may be made by parties other than the grant holder. | Confirm the build leaves power, channels and data rates alone. Keep the diff on file. |
| Change to frequency-determining or stabilizing circuitry (including clock or data rates), multiplier stages, the basic modulator, or maximum power or field strength ratings | The rule lists these as changes that need a new grant of certification, except as provided in 2.1043(b)(3). | Treat as a new certification project until your test lab says otherwise. |
| Other electrical or mechanical change, such as layout near the radio, a part swap, an antenna or an enclosure change | Allowed when it does not affect the characteristics reported to the FCC, or as a permissive change. Class I does not degrade them and needs no filing. Class II degrades them but still meets the rules, and needs test results and FCC acknowledgment before marketing. | Ask the lab which class applies. FCC guidance is in KDB 178919. |
| A replacement part that is not pin-to-pin compatible | KDB 178919 includes Notification 202109-001, which says the FCC lab may give case-by-case guidance on such parts changes. | Raise it with the lab before you lay out the new board. |
| A new model name or FCC ID | 2.1043(d) says a change in identification needs a new application. When the reported characteristics do not change, the abbreviated procedure of 2.933 may be used. | Decide model naming before the first grant if you can. |
Watch the conditions. Any change made by a Covered List entity, or one that would make the device Covered Equipment, needs a new grant. Permissive changes must not change the identification. Class I and Class II changes may only be made by the grant holder, except as the rule specifies. If your product relies on a module's grant, only the module's grantee can make those changes under that grant. A grantee filing a non-permissive change must also state whether it goes into all units or only units built after authorization, which is your ECO's effectivity field.
FCC guidance is KDB 178919, with a permissive change policy (D01, version 06) and an FAQ (D02, version 01) (FCC KDB 178919, as of November 2026). We could not open the attachments, so this guide summarizes only the rule and the KDB publication page. Ask your test lab which class a change falls into, and file the answer with the ECO. If your own change process also uses the labels Class I and Class II, say in each ECO which scheme you mean.
How strict should change control be at each development stage?
Heavy process on a first prototype slows learning. Loose process in production mixes revisions. Scale it with the stage.
| Stage | Change control | Why |
|---|---|---|
| Works-like prototype | Light. The engineer keeps a change log in the repository and tags each build. | Speed matters most. Record changes so test results can be traced. |
| First custom PCB (EVT) | Revision letters on schematic, layout and BOM. A short ECR and ECO note for each board spin. | Several people now build from the files, so board and files must match. |
| Design validation (DVT) | Formal ECOs with test, manufacturing and compliance review. | A change after certification testing can put the result in question. |
| Pilot and small batch | Full ECO package with effectivity, disposition and ECNs to every supplier. | Real units reach users, so traceability by serial number starts to matter. |
| Production | Every change through the same process, plus supplier notices. | Changes now come mostly from parts, cost and field data. |
Draw the line at the first build someone outside engineering relies on, such as certification testing or a pilot. From then on, every change goes through an ECO. What each build is for is covered in EVT, DVT, PVT: what you get at each gate. For how the stages fit together in a gated project, see our development process.
What should you ask your hardware team about change control?
Ask these before the first pilot build, and keep the answers with the project documents.
- Who owns the change process, and where do ECRs, ECOs and ECNs live?
- Does every board, firmware image and enclosure carry a revision we can read on the unit?
- Which BOM lines sit in the radio path, and who checks a change to one against the FCC grant?
- Who holds the FCC grant, and so who can file a Class II permissive change?
- How do we set the effective point: by date, by lot or by serial number?
- Which test limits and fixtures change, and who re-runs the first article check?
- Do we receive the updated source files and SBOM after each approved change?
Questions about engineering change orders
What is the difference between an ECN and an ECO?
Usually the ECO is the approved order that defines the change and its files, and the ECN is the notice that tells the factory, suppliers and internal teams to act on it. Some companies use ECN for the order itself, so write your own definitions into the process document.
Is an engineering change notice the same as a supplier PCN?
No. Your ECN goes from you to your factory and suppliers. A product change notification (PCN) goes from a part maker to its customers. TI says its notices follow J-STD-046 and list the reason, the affected products, qualification results and the projected production shipment date (TI, as of November 2026). A PCN on one of your parts often starts an ECR on your side.
How could Duobay help with design changes?
Duobay develops custom devices: electronics, firmware, enclosure and, as an option, the app, with samples and small batches. The work runs in gates you can exit at any point, and source files are assigned to you at every paid gate. Initial calls are free. Tell us about your device.
If you are planning a device and want change control set up from the first custom board, tell us about your device.
Sources. All pages accessed November 6, 2026. Rules and supplier policies change, so read the current versions before you decide.
- 47 CFR 2.1043, Changes in certificated equipment, eCFR, up to date as of November 4, 2026 (link)
- FCC Office of Engineering and Technology, KDB 178919, Section 2.1043 Permissive Changes, publication page (link)
- Texas Instruments, Product change notification (PCN) (link)
- Espressif, PCN listing page (link)
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