ECR, ECO and ECN
Companies use these names differently, and some treat ECN and ECO as the same thing. The common pattern:
| Document | Purpose | Typical source |
|---|---|---|
| ECR, engineering change request | Proposes a change and the reason for it | Engineering, quality, the factory or a component supplier |
| ECO, engineering change order | Defines the approved change: what, which items, from when, at what cost | The product owner’s engineering team, with the factory’s input |
| ECN, engineering change notice | Tells everyone who must act on the approved change | Engineering or document control |
The label matters less than the discipline: every change to a released design goes through a request, a decision and a recorded notice, and the factory works only from the released revision.
What a change order should contain
- Description of the change and the reason for it
- Affected part numbers, drawings, BOM revision (from and to), firmware versions and test programs
- Effectivity: the date, lot or serial number from which the change applies
- Disposition of existing material on order, in stock, in work in progress and in finished goods: use as is, rework, scrap or return
- Cost impact: tooling changes, NRE, unit price, obsolete inventory, and who pays for each
- Validation needed: which tests are repeated, whether samples are rebuilt, whether certification is affected
- Approvals from engineering, quality and the factory
Disposition and cost are where most disputes start. A change that looks small on a drawing can strand thousands of parts that were already bought.
Classify changes by impact
Not every change needs the same process. A simple two-level rule keeps small changes moving without letting large ones slip through:
- Minor: documentation corrections and changes with no effect on form, fit, function, safety, compliance, cost or appearance. Engineering approval and a notice are enough.
- Major: anything that affects those areas, or that the customer can see. Full review, validation evidence, updated samples and written approval from the product owner before the factory acts.
When it is unclear which class applies, treat the change as major.
Why changes get more expensive over time
Before tooling is cut, many changes are a drawing revision. After tooling starts, a change can mean steel modifications, another mold trial and new samples. After certification, some changes to radios, antennas, power circuits or enclosures can require re-testing or a filing with the certification body; see product certification planning. After production starts, every change also carries inventory and traceability cost.
That is why the design freeze points in the EVT, DVT and PVT sequence matter. A change after DVT needs a reason strong enough to justify reopening validation.
Changes that start at the factory
Change control works in both directions. A factory may want to substitute a component, switch a sub-supplier, move work to another site or adjust a process. Component makers also issue product change notices and end-of-life notices that flow down to your product.
The supply or quality agreement should require the factory to get approval before changing:
- Components, materials or approved manufacturers on the BOM
- Sub-suppliers of critical parts
- Production site, line or key equipment
- Process settings that affect form, fit, function or reliability
- Test methods, limits or test software
Unapproved changes are a frequent root cause in CAPA investigations, and change-control records are a standard item in a factory audit.
Traceability and reference samples
Every shipped unit should be traceable to the revision it was built at: hardware revision, BOM revision and firmware version, ideally by serial number. Without that, a field problem tied to one revision forces a much wider recall or retest than necessary.
When an approved change alters what a correct unit looks like, update the golden sample and inspection criteria at the same time, or the line will be checked against an outdated reference.
Where Zefinity helps
Running engineering changes between your team and the factory, including their cost and inventory impact, is part of NPI and technical project management and supplier coordination in Zefinity’s Launch service.
Frequently asked questions
What is the difference between an ECN and an ECO?
In the most common usage, the ECO is the approved change itself: what changes, which parts and documents are affected, when it takes effect and what it costs. The ECN is the notice that tells the factory, suppliers and internal teams about it. Some companies use the two names interchangeably, so check how your factory uses them.
Who pays for an engineering change?
It depends on the cause and the agreement. Changes you request are usually at your cost, including tooling changes and any parts made obsolete. Changes needed to correct the supplier's own nonconformity are usually at the supplier's cost. Write the rules into the supply agreement before production, including who pays for parts and finished goods that a change makes unusable.
Can a factory change components without the buyer's approval?
It should not, and the agreement should say so. Require written approval before any change to components, approved manufacturers, sub-suppliers, production site, key equipment, process settings or test methods. Unapproved substitutions are a common root cause of quality problems, and they are much harder to trace when nobody recorded them.