Box build assembly, from working boards to a finished unit

A screw the driver cannot reach, a cable with no route, a gasket that can go in two ways: each one costs time on every unit. Our engineers find these in a DFM review while the enclosure is still a model. The DFM services page explains how that review fits into the design phase.

Our engineers also review the test plan early. A functional test needs a fixture and a pass definition, and both take longer than people expect. The pass definition is set before the demo build, and the fixtures are built before PVT, so the test you approve at PVT is the test every production unit gets. Box build is one of the nine processes the Shenzhen factory runs in-house: SMT, bare PCB fabrication, injection molding, CNC machining, sheet metal, die casting, stamping, box build and test. The engineers who reviewed your assembly stay on the project when it reaches the line, and nothing moves to a new supplier between pilot units and volume. The factory assembles the boards on 8 automated SMT lines before they reach the box build line. Our engineers attend the EVT, DVT and PVT builds in person, so questions on the line get answers the same business day. We sign your NDA before the first call, and project files live in private project storage. One reviewed record holds the boards, the made parts, the bought parts and the build itself, and it shows the critical path while you can still change it.

In a box build, quality covers the whole unit. The Shenzhen factory holds ISO 9001, so the build runs under a certified quality management system. Assemblies inside the unit are built to IPC-A-610, and Class 3 applies when you state it with the order. Harnesses are built to IPC/WHMA-A-620. At volume, each production batch is compared with the golden sample you signed after PVT. The sign-off record lists the design revision, the BOM, the firmware release, the measured values and the cosmetic limits, judged under set light at a set distance. When a result drifts from the reference unit, an engineer reviews the drift before the next batch runs.

Per-unit records: firmware test results are kept for each serial number. Test fixtures: functional test stations run your test sequence, the same one at each build stage. Named standards: ISO 9001 at the Shenzhen factory, IPC-A-610 for electronic assemblies and IPC/WHMA-A-620 for harnesses. Your tooling: fixtures and test stations you pay for belong to you, and you may move them to another factory.

A BOM that covers the mechanical parts as well as the electronics: enclosure, fasteners, gaskets, labels and packing. A 3D model of the assembly. Drawings for every custom part. Assembly instructions with torque values. And a test definition that states what the test proves and what counts as a pass.

The test definition is the item most often missing. Functional test is a declared assembly need. But what the test proves, what the fixture is and what counts as a pass all come from you. Agree them in the free engineering review. Finding out at first article that nobody defined them costs far more. If you have no test plan yet, our engineers can write one from your product requirements and review it with you before the fixture is built.

Because a board has one supply chain and a box build has many. The unit cannot be assembled until the slowest item arrives. That item is often a custom mechanical part or a molded enclosure with its own tooling lead time. A board that is ready early is worth little if the enclosure is not.

Make-or-source preference is a declared field with four settings, and traceability and the alternates policy are declared beside it. With the made parts, the bought parts and the build on one reviewed record, the critical path is visible while it can still change. Production molds are cut after DVT closes the design, so plan the enclosure tooling into the schedule from the start. Our engineers check parts availability and alternates before the schematic is drawn, and again for the mechanical parts before the enclosure is released. A long-lead connector, display or battery found at that point is a design choice you can still change. Found at the first production order, it is a delay you must accept. The review lists each long-lead item with the date it must be ordered to meet the build.

Design for assembly means a product that takes few steps to build and is hard to build wrong. Fewer parts, fewer fasteners, features that fit only one way, and room for the tool to reach each fastener. Every part you remove cannot go missing, go in backwards or arrive at the wrong revision.

Do it before the enclosure tooling is committed. After that point, changes stop being cheap. Declare the project phase (concept, prototype, pilot or production), so the review addresses the decisions that are still open. Our engineers repeat the DFM review at the later stage gates, so late changes are checked against the line too. Typical findings are simple: four screw sizes reduced to one, a snap fit that replaces two fasteners, a keyed connector that cannot be plugged in backwards, or a label moved to a face the operator can reach. Each one removes a step from every unit you build.