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What is a Box Build Assembly?

PCB box build assembly

Manufacturing involves many moving parts and coordination among multiple vendors. However, when you’re making the move to scale or you’ve decided its time to put a board into volume production, certain manufacturers can offer multiple services to help you reduce the logistical workload. One of these service levels is a box build assembly service, where the manufacturer delivers a complete electronics assembly in a box that is immediately ready to use.

A box build assembly service isn’t the right path for all products, and different electronics manufacturers have varying capabilities in this area. Some offer a complete package while others require working with a vendor or partner to coordinate all aspects of the design package. Depending on the services you need, you could receive a

What is a Box Build?

If you look at a manufacturer's website, they will sometimes describe a box build assembly as a system integration, meaning they try to bring as many parts of the system into the assembly as possible. Box build assembly involves assembling both the PCBA and the “box” (or enclosure) in which the product will be packaged. These assemblies are an option for volume production after the board has been prototyped, tested, tested for EMC, and and qualified against any other relevant regulations.

Some of the components that go into a box build include:

  • Connectors, including modular connectors like D-shells
  • Custom cable assemblies and wiring harnesses
  • Batteries, either as the main or backup power source
  • A custom or off-the-shelf enclosure
  • Heat sink attachments with a thermal interface material
  • Other attachments to the board, like brackets or standoffs
  • Other attachments to the enclosure, such as fans

Different manufacturers offer different capabilities and service levels in these areas. Some of these components may need to be procured from vendors or partners, while some can be purchased off-the-shelf. As a designer, it’s important to work with the assembler to determine which of these components needs to be procured from a distributor and which can be custom-built.

Custom Enclosures

This is normally where all the focus lies for box build assemblies. Custom enclosures for a box build assembly are overwhelmingly made from sheet metal. This is because sheet metal is easy to cut and fold into an enclosure, yet it will give you something very durable. It can also be drilled to provide inlets for cables or connectors.

Sheet metal fabrication is a low-cost option for a box build assembly.

Sheet metal box build assembly

All Off-the-Shelf Components

The simplest path forward involves total use of off-the-shelf components to build the enclosure, construct the cable assembly or wire harness, and assemble everything in the box. There are small metal and plastic enclosures that can be purchased from electronics distributors, and they can be quickly machined to provide inlets for cables and panel-mount or board-mount connectors. At moderate volume (100’s of units), you will start to see a volume discount on those enclosures. The same applies to other parts like connectors, cabling, and mechanical parts like screws or brackets.

Enclosure box build assembly

Example off-the-shelf enclosure from Molex.

Firmware in a Box Build

If you look at the above list, you will see all the physical and electronic components that will typically go into any assembly, including box build assemblies. That list is the first place to start looking into the physical components you will need to create a box build.

One area of a box build assembly that can be overlooked is firmware or OS installation in a memory chip or on the device’s processor. Many devices offer some level of computational power and will require firmware to function. As part of a box build assembly, firmware can be integrated into the box build assembly in three ways:

  1. Some distributors will flash your firmware onto a memory chip when you order from them. Those chips will arrive at the assembler and will be placed in your box build.
  2. You can order and flash the memory or processor on your own, and then send these off to your assembler.
  3. Some box build assemblers offer firmware flashing and/or testing services. You have the option to provide your binaries and the assembler will build a fixture for on-the-line flashing.

box build assembly

You may need to provide pre-flashed memory for your product to your box build assembly provider.


In summary, if you want to receive a ready-to-use assembly from your manufacturer, and you want to cut down on vendor logistics, then a box build assembly service might be for you. Depending on the capabilities of the manufacturer and their vendor partners, you could have multiple options for enclosures, ranging from simpler plastic enclosures to custom sheet metal enclosures. It’s also possible to work with a 3rd party enclosure design and production facility that can deliver the custom enclosure to your box build assembly house, and the assembler will do the integration.

Based on the costs involved and the level of automation involved in the box build, this route can be very useful for moderate volume production or short runs that will not go to mass market. A box build is also easy to prototype on your own and transition into production, and the tooling cost is extremely low compared to injection molded plastic or extruded aluminum enclosure manufacturing.

When you need to design a PCB for your next prototype, box build assembly, or high-volume product, make sure you use OrCAD from Cadence to specify your design requirements and create your PCB layout. OrCAD includes the industry’s best PCB design and analysis software. OrCAD users can access a complete set of schematic capture features, mixed-signal simulations in PSpice, and powerful CAD features, and much more.

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