Box Build Assembly: An OEM Guide to Scope and RFQs

By Meco Engineering Team · Published: 24 February, 2026 · Updated: 12 October, 2026 · 10 min read IATF 16949:2016

A finished electronics product is more than a board in a housing. Someone must confirm that the enclosure fits, cables reach without strain, fasteners receive the correct torque and the completed unit passes the tests that matter to its intended use.

Those tasks are easy to miss when an OEM asks three suppliers for a “box build quote” without defining the same scope for each. One supplier may price assembly labor only. Another may include sourcing, test fixtures, inspection and packaging.

This guide helps you define the work before you compare quotes. It covers the handoff from PCBA to final assembly, the choice between consignment and turnkey supply, and the documents needed to make a quote useful.

If you are ready to evaluate Meco as a supplier, see our contract assembly services. This article focuses on the decisions you should make first.

What belongs in a box build?

Scope varies by product. A typical build may combine a PCBA, enclosure, fasteners, cable assemblies, connectors, switches, displays and labels. The work can also include installing software or firmware, testing and final packing, but these steps must be specified and agreed for the project. Do not assume every box build quote includes them.

The enclosure is part of the engineering decision. A sheet-metal housing may suit a low-volume industrial product without requiring an injection mold. A molded plastic housing may suit a product whose volume justifies tooling. Either choice affects mounting features, cable routing, finish, inspection and assembly sequence.

Write down the handoff point for each component. For example: does the OEM deliver tested PCBAs, or does the box build supplier also manage board sourcing? A clear boundary prevents the same task from being priced twice or missed altogether.

PCBA versus box build: where is the handoff?

Printed circuit board assembly (PCBA) places and joins electronic components on a board. Box build integrates that board with the enclosure and other product-level components. A supplier may provide either service or both. Meco’s PCB design and assembly capability covers the board side of that decision.

The handoff is especially important when two companies do the work. Agree how boards arrive, how they are identified, what incoming inspection applies and who investigates a failure found after final assembly.

Consignment or turnkey: who buys the parts?

In a consignment model, the OEM supplies some or all components. This can work when the OEM already has approved electronics or controlled suppliers. It also means the parties must agree how shortages, damaged parts, substitutions and unused inventory are handled.

In a turnkey model, the manufacturer sources the agreed components as well as assembling the product. This can reduce the OEM’s purchasing workload, but the quote must specify approved parts, alternates, lead times and responsibility for long-lead stock.

Many programs are mixed: an OEM may supply a proprietary PCBA while its partner sources the enclosure and hardware. Define the split line by line in the BOM. For a deeper explanation of these commercial models, read our guide to contract assembly.

What drawings and BOM data does an OEM need?

Start with a controlled BOM: part numbers, descriptions, quantities, approved manufacturers where applicable and revision levels. Mark every line as OEM-supplied or manufacturer-sourced. State whether alternates need written approval.

Add enclosure CAD files, dimensioned drawings, a PCBA outline and mounting details, cable drawings or pinouts, assembly instructions and label artwork where relevant. If the fit between the board and housing is critical, identify the controlling dimensions rather than expecting the supplier to infer them from a model.

Finally, provide a forecast or expected batch sizes, target delivery location, packaging requirements and a list of acceptance records. A working sample can help explain the intended result, but it should not replace controlled drawings and pass criteria.

Specify functional testing before quoting

“Fully tested” is not a test plan. State what must be checked at board level, during assembly and on the finished product. Depending on the design, checks may include connector continuity, power-up, display and control operation, communication interfaces, mechanical fit and labeling.

For each check, specify the test method, pass or fail limit, sampling plan and required record. Identify who supplies any software, fixtures or reference units. If firmware installation, burn-in or an automated functional-test fixture is needed, ask the supplier to confirm its scope and price rather than treating it as a standard inclusion.

Decide what must be traceable

Traceability can connect a finished unit to its PCBA revision, incoming component lots, assembly instructions and inspection results. The required depth depends on the product and the OEM’s quality system. Decide whether the deliverable is a batch record, a serial-level history or both.

Ask how nonconforming units will be identified and kept apart from accepted units. Also agree which reports are required at first article and which must accompany routine shipments. Meco supports first article inspection, material records and lot or serial traceability; the exact deliverables should be written into the project requirements.

What drives box build cost?

Assembly time is only one line. The larger cost drivers are the number of unique parts, sourcing responsibility, enclosure tooling, cable complexity, build time, test coverage, fixtures, inspection, packaging, order volume and component availability.

A design change can move cost between lines. For example, reducing fastener types may simplify procurement and assembly, while adding a product-level test may increase immediate cost but make acceptance more repeatable. Ask suppliers to state their assumptions so you can compare quotes on the same basis.

Compare the delivered cost per accepted unit. Include tooling and test-fixture charges, recurring assembly costs, expected rework treatment, packaging and delivery terms. Do not compare a labor-only quote with a fully sourced and tested build as if they cover the same product.

This is a planning framework, not a quotation or legal or customs advice. Project pricing and delivery terms require a review of the actual design, volumes and destinations.

OEM box build RFQ checklist

Before sending the RFQ, confirm the following:

1. Scope: State whether the quote covers PCBA, enclosure production, final assembly, testing, labeling and packaging.
2. Supply model: Mark each BOM line as consigned or supplier-sourced, including approved alternates.
3. Technical files: Include controlled CAD, drawings, board information, cable details and assembly revisions.
4. Test plan: Define methods, pass criteria, sampling, fixture responsibility and required results.
5. Quality records: Specify incoming inspection, first articles and lot or serial traceability.
6. Commercial inputs: State batch sizes, forecast, target date, delivery location and packaging requirements.
7. Open decisions: Ask each supplier to list exclusions and assumptions beside its price.

That checklist makes it easier to compare bids and to carry the approved scope into production. If the requirement is a complete manufactured product rather than assembly alone, distinguish that wider scope from the box build in your RFQ.