Box Build Assembly — Your Design Built Into a Working Unit, From One

Who This Is For

EKINSUN is a custom parts manufacturer in China that also assembles complete electronic products from the customer's own design, from one unit: the PCB, the enclosure, the display, the battery and the cables put together into one working device, firmware flashed and tested before it ships. We build what you designed. We do not design it for you.

The usual situation: a hardware start-up, a design consultancy or a company's R&D team has a finished design and needs one prototype, or a handful, to show, to test or to send to a certification lab. Buying the bare boards, the SMT assembly, the housing, the screen, the cell and forty small parts from a dozen suppliers, then putting it all together, is the part that stops the project. We take the job from one unit, and the same files then carry on to batch production.

Any product built around a PCB fits: a handheld device, a controller, a sensor or IoT unit, a small instrument, a charging dock, a control panel.

What Goes Into the Unit — and Who Makes Each Part

Final assembly, firmware flashing and testing are done by EKINSUN. Turned and milled parts come from our own CNC factory; the other processes run at partner factories we work with.

Only part of the product to build? That works too: a PCBA fitted into a housing you already have, or a housing and wiring around a board you supply. For the enclosure alone, see custom enclosures and heatsink enclosures machined around your board.

How an Order Runs — and the Files to Send

A box build order runs in six steps, from your files to a tested unit:

1. You send the files and the quantity by email: one unit now, and what you expect later.
2. We check the BOM and the files before anything is bought or built.
3. You receive the quote and confirm turnkey or consigned components.
4. Boards, enclosure and parts are made or bought: bare PCB and SMT at partner factories, machined housing parts in our own CNC factory.
5. We assemble, flash and test each unit to your test steps; a test record can come with it.
6. The unit ships to you.

The files

A box build needs seven files:

• Gerber files (RS-274X) or ODB++ for every board, plus the drill file.
• BOM with manufacturer part numbers and quantities per board. Mark which parts may be replaced by an equivalent and which may not.
• Pick-and-place file (centroid, X/Y/rotation per component).
• Enclosure model as STEP, and a 2D drawing for machined parts.
• Assembly drawing or 3D assembly of the whole product: what goes where, screw sizes, cable routing, labels.
• Firmware file (.hex, .bin or .elf), the target chip and the programming method.
• Test steps: what to check on each unit and the values that count as a pass.

Send them by email to [email protected], with the quantity: one unit now, and what you expect later if a batch is likely.

Before Assembly: BOM and File Check

Every build starts with a check of the BOM and the files, and assembly begins only after that check. A part number that does not match its footprint, a board that does not fit the enclosure model, a part that cannot be bought: these are cheap to fix on paper and expensive to fix on a built unit.

Turnkey or Consigned: Who Buys the Components

Components for a box build are either bought by EKINSUN to your BOM (turnkey) or shipped by you (consigned); both routes are open, and you choose per project.

For consigned SMT parts, send extra quantity of the small passives (0402 and 0603 resistors and capacitors): the placement machine loses a few on every reel.

Firmware and Testing

Every unit is flashed with your firmware and tested before it ships. We load the file you send, power the unit up and run your functional test steps: the screen shows what it should, the buttons respond, the battery charges, the radio connects, the outputs read the values you specified. You write the test; we run it on each unit, and a test record can come with each unit. We do not change or write firmware.

From One Unit to Production

The first build is usually one unit, to prove the design works as a whole. Then a few units for testing and for the certification lab (in hardware teams often called EVT and DVT builds), then a batch. Each stage uses the same files and the same parts sources, so a revision only changes what you changed. You can ask for several quantities in one request, for example 1, 10 and 100 units.

The enclosure: prototype route and production route

For one unit or a few, a housing is machined from solid in our own CNC factory, with no tooling. For 10 to 100 plastic housings, vacuum casting from one master is often cheaper. At production volume an injection mould pays for itself and the housing is molded. Drawing the housing for the production route from the start makes the prototype a truer test of the final product. See vacuum casting, custom plastic parts and the injection molding cost calculator.

Machined parts follow the same rule as the rest of our work: from 1 piece, with the program kept for the next batch.

Lead Time and the Cost of One Unit

A box build has no fixed lead time: it depends on how complex the product is. A simple product can be assembled in about 15 days.

One unit costs more per piece than a batch because the setup is the same for one board as for fifty: the bare-board fabrication setup, the SMT setup, the CNC program for the housing. From the second build on, the setup is shared across more units and the unit price falls.

Shipping a Unit With a Lithium Battery

A lithium-ion cell built into a device ships by air as UN3481 (lithium-ion batteries contained in equipment). The courier needs the cell's UN38.3 test summary and a safety data sheet (SDS). If you consign the battery, ask your cell supplier for both; on a turnkey build, the cell we buy must come with both. Units without a battery ship as normal electronics.

What We Do — and What We Do Not

EKINSUN assembles, flashes and tests to a finished design; design, firmware writing and certification stay with the product owner.

Confidentiality

An unreleased product is the most sensitive file set a customer can send. Your files are used only for your build, and we sign an NDA before you send them if you ask. See NDA and confidentiality.

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Frequently Asked Questions