Box Build Assembly

Defining Box Build Assembly

A box build involves all electronic assembly features except the manufacturing of the printed circuit boards (PCBs). It can be termed as a subgroup of electromechanical assembly (EMA). EMA itself is also known as the integration of systems. Some of the processes involved in box build assembly are the fabrication of the enclosures, cable routing and connections,  Assembly of Electronic Components and electronic components installation.

Integration of Systems

Systems integration is a name given to various electronic assemblies such as PCB assembly integration with sub-assemblies and modules, design of enclosure and chassis, thermal considerations, and cabling and wiring. All these processes are performed through specialized machinery, and various tests are performed.

Electromechanical Assembly

All the electronic assembly stages that require both electrical and mechanical processes to complete a task are collectively called electromechanical assembly. Usually, the term box build is used to summarize the complex process of putting together the many elements inside a single, ready-to-go package. Linking separate elements to build a reliable package that can withstand extreme conditions is the challenging task of the Electronic Manufacturing Service (EMS) industry. The EMS company’s experience and services are vital in deciding the quality of the final product.

Process of Box Build

The box build approach is unique to each project and, at each level, will require different degrees of sophistication. It may involve merely placing within an enclosure a printed circuit board assembly. It may include the complicated task of linking an assembly to a display of the user interface.

Box Build Assembly Services

The EMS must know all the essential details of the entire product assembly to produce a suitable box build assembly. An EMS provider may offer the following services for box building. High-level system assembly

  • Final product assembly
  • Sub-assemblies within the final product
  • Product packaging
  • Package labeling
  • programming, uploading firmware, installing software.
  • Product configuration and testing
  • Storage and warehousing
  • Fulfillment of the order
  • After-sales repair and support

Characteristics of a Good Box Build Assembly

A suitable EMS provider should offer box build service for various PCB assembly technologies such as Through-Hole Vs Surface Mount Assembly. The provider must be able to check and guarantee the quality of components within the system. Specialized machines and automation enable the production of box build assemblies with perfect specifications and without human errors. For modern box build assemblies, the service provider must have advanced component management to assemble the complex box build assemblies.

Consider Box Build during PCB Design Stage

The essential components of Device Integrations are enclosures and casings. Enclosures can be made up of many materials such as plastics, metal, metal alloys, and combinations of plastics and metals. There are many viable off-the-shelf options, mostly with lower unit costs and no restriction on minimum orders.  But the ready-made choices are not specific, the parts do not match properly, and a producer may change or remove the product.  Only custom-made enclosures will satisfy the need to fit PCBs safely alongside other electronics, components, wiring, and exhaust fans.

As plastics and polymers are more widely used, an EMS supplier must consider the variations between materials and production methods.  For example, ABS is only ideal for indoor conditions since it can be affected by excessive sunlight exposure, while ASA+PC resists elevated temperatures and extreme conditions.  New techniques may integrate soft-touch textures and paint, such as the MS-MMM molding process, preventing the need for multiple material suppliers.  It is the role of an EMS supplier to pass on this information to the customer beforehand.

In box build assemblies, metals are often incorporated. The materials are precision-fabricated. To safeguard both the packaging and components from weather, decay, corrosion, conductive or harmful particles of dust, water, and general pollution, coatings can be required.  Automated machines are used to add protective coatings on the chosen board and components to increase performance and reduce errors.



The cable and wiring sophistication will differ significantly between Device Integration projects, from a few striped, twisted, and tinned wires to complicated bundles of thousands of wires and a plethora of terminations.  Most projects include various lengths of customized wiring, distinctive colors, special pin-outs, unique identifiers, advanced connectors, etc.  Modern automatic cut and strip cabling machines can handle complicated low-volume wire straps as well as assemblies of medium-volume cables. Ensure that the EMS provider offers supply chain traceability to know where the materials are being sourced from.

Customization for Ready-made Boxes

Often users prefer to use readily accessible Off-The-Shelf modules such as boards, controllers, HMIs and monitors, power supplies, etc. Using pre-tested sub-assemblies helps reduce production costs and time, but many compromises on functionality have to be made. Using both COTS and custom-builds to better suit the client’s current and potential needs, significant device integration initiatives take a mixed approach. Some level of customization is still required in using COTS modules. An EMS supplier should have the expertise of incorporating COTS modules into larger systems.

Mechanical Components

Sometimes, the box builds assemblies need to consider electromechanical assemblies that include mechanical switches, electronic controls, gears, rollers, etc. these moving components are naturally more complex to integrate. Conflict is regularly discovered with other components, especially from various suppliers.  An EMS supplier has to have a full understanding of the demand for global components.  To boost the design stage’s speed, it should be able to use computerized modeling of CAD /CAM equipment and provide a well-equipped testing area, including microscopes and electrical measuring instruments.

Selection of an Appropriate Box

When choosing an enclosure for your box building assembly, you effectively have two options: an off-the-shelf version or something more tailor-made. There are plenty of suppliers to choose from if you opt for the COTS option, selling standardized enclosures made up of various materials having different finishes. An off-the-shelf enclosure becomes a good option when the following parameters are essential.

  • Cost-effectiveness
  • No limit on the number of orders
  • Improved accessibility

You may be restricted to a certain extent, though, as the casing will not have been built for your particular application. Also, it is crucial to ensure that you select a model that will comfortably match your PCBs. When the portions of the front and back are connected, external electronics such as LCDs, linking wires, fans, LEDs, etc. are not trapped.

If the design would allow you to conduct regular maintenance or repair is another aspect to consider. No one wants to see a product become redundant because the repair services and upgrades are too expensive to carry out. It is an excellent option to soak test or stress screen the box builds to ensure it will survive the extreme condition under which it would be put throughout its lifespan.

Many of the difficulties mentioned above will not be applicable if you want to use a bespoke enclosure since it would be built according to your requirements. Your PCBs will easily fit into place.  All interior objects would have enough space to prevent pressure on each other. The bespoke enclosures would have been built with the right characteristics to withstand the environmental condition that the enclosure is designed for.

A variety of possible issues can occur, however.  For example, a customized casing is going to be pricy, sometimes involving high upfront costs. After initial purchasing from a retailer, it should be made sure that the retailer continues to manufacture this particular casing for a stated time period. While Designing and manufacturing your box build, keep the third-part sourcing of electronic components in mind to ensure that the electronic parts required for your assembly remain accessible during your product’s lifespan.

Besides, to prevent misunderstanding at the product’s designing and development stage, a full collection of specifications and diagrams for the enclosure must be made, with appropriate tolerance thresholds and specific instructions when it comes to quality requirements.

Documentation and Changelog

Inadequate documentation and unavailability of information management trigger delays in assembling the box and also contribute to a faulty product being made. It may be tempting to let documentation slip on the back burner occasionally, so you have to make documentation a priority. Revision control and maintenance of BOMs, CAD sketches, Gerber reports, applications and all other information and data should be appropriately stored. The changes that occur in the development must be governed by a strict engineering change note (ECN) procedure. When you have a detailed changelog for reference, it’s much simpler to find challenges, and you are sure to save precious time and resources in the procedure. For illustrations and texts, the labels should be drawn clearly. The enclosures and casings should have well-specified tolerances and finishes.  Leaving these items subject to under specified can lead to quality management problems later on.


Testing is not anything that you can perform as an extra option, but rather it should be at the center of the manufacturing stage. It is preferred to perform testing at every possible step of the box build assembly. Testing offers you the confidence that when your client gets the device out of the packaging, the finished product works as intended. The expectations of the customers must be satisfied.

You may need to perform a soak test or stress screening of your box build assembly, as explained earlier.  And you need to test the specific PCBs as well. The boundary check, in-circuit test (ICT), and flying probe are common testing techniques for PCBs and box build assembly.  When deciding which choice better fits your requirements, the complexity of the offering, the market, and your budget would all be considerations, and there are pros and cons of both approaches.

The additional test can also be performed, such as powering up the final product to see if it works. Box building assembly may differ in its sophistication. Still, there are many fundamental issues that OEMs encounter again and again, irrespective of how many parts make up the individual product.  It would help if you took several precautions to guarantee that there will be no complaints before the product reaches the consumer, from sourcing an enclosure to paperwork and changelog and testing.

Streamlining the Box Build Assembly Process

To fast track the development process of box building, the following information must be provided to the box build assembler.

Design Specifications

The design specifications include product measurements such as the weight and size of the assembly. This knowledge provides the EMS with the appropriate information to decide how the units will be treated during the full assembly stage in box production. The information about the dimension is necessary for storing, packing, and transporting the end product.

Bill of Materials (BOM)

Perhaps the most significant piece of data given to an EMS supplier is the bill of materials. The BOM allows the EMS to grasp all the significant components and resources that need to be collected. Each element on a bill of materials has a particular function, procurement method, and related expense. The EMS will be able to predict development problems and develop contingency strategies with a well-crafted BOM.

3D CAD Model

The box build assembly needs to visualize the end product. Computer-aided design (CAD) applications are available that can provide visualization opportunities for three-dimensional (3D) models. Computerized sketches and models may also be translated into build instructions through this 3D CAD software that can minimize the time it takes to assemble a box build.


An EMS will also take the basic prototype of a client and produce several identical assemblies quickly. With limited information, highly trained electromechanical assemblers will also duplicate a full box building.

Testing Use Cases

During box development and assembly, customers can determine which checks have to be conducted. Visual evaluation, factory acceptance monitoring, and essential practical assessments are some of the testing use cases.  Final electrical testing of the box build assembly can be performed using the earth bond test and the flash test.

Packaging and Shipping Info

It will include valuable planning details to decide how the box building assembly would be packaged and delivered. This information helps the EMS to make choices on how the units will be handled to maximize box build speed in the full box build assembly stage.