A few years ago, my son gave me a build-it-yourself kit that, once completed, was a simple little black box. No kidding, this little box had nothing on it except for a toggle switch. The hilarious thing though is that when you throw the switch, a little arm pops up out of the lid and flips the switch back so the lid will close again. That’s really all it does—open, close, and then repeat. I still laugh every time I flip the switch.
Interestingly enough, I realized that this little box was perhaps the first electronic enclosure I ever built. We PCB designers are often so focused on the minute details of the electronics that we design that it is easy to forget that they must all go into something. Fortunately, there are assembly houses that specialize in building boxes, chassis, and enclosures for electronics. Let’s take a moment here to look closer into the box build assembly process so that you can see precisely what these manufacturers can do for you.
What You Need for the Box Build Assembly Process
To get your electronics enclosure—or box—built, you first must find a contract manufacturer that specializes in this capability. There are many manufacturers that will build a box for you, but for the best results, you should look for a CM that has experience in building all of the components of your electronic device.
With a CM that can build the entire product, you won’t have to worry about trying to coordinate your product between multiple vendors. In addition, having your entire product built by one vendor means that the individual components, such as the circuit boards and wire harnesses, will be built to work together.
Once you have settled on a CM for your project, you will next need to send your instructions for building the box to the CM. These should include:
- Bill of materials (BOM)
- Electrical schematic
- Assembly drawing(s)
- Wire list(s)
- Test specification
- An example (golden) unit if available
Your CM can probably build the box with only a bill of materials and an electrical schematic, but these may be lacking important information. This could result in a lot of questions from them and many meetings to understand your needs. In the end, it is always better to give them as much information as possible.
The key is to be prepared to work together with your CM throughout the box build process. You will want to ensure they have all of the information that they need to successfully build your project.
Your Contract Manufacturer’s Process for Box Build Assemblies
A box build assembly at VSE.
Now that your CM is prepared to build your project, here the general process that happens. Typically a box build will contain printed circuit board assemblies (PCBAs), wire harnesses, point-to-point wiring, and the mechanical structure of the box. Building all of this together is like making a layered cake, and the order of how all of these pieces are structured is critical to the success of the project. They’re usually completed like this:
- Build and test all of the PCBAs used in the device.
- Build and test all of the device cables and wire harnesses.
- Cut, strip, and label the ends of the individual wires in preparation for their assembly.
- Start the assembly of the box build from the bottom, and work up through each level. This will include bolting parts together, seating and interconnecting circuit boards, and connecting all of the wire harnesses and point to point wiring.
- Incorporate customer manufacturing and workman specifications into each level of the assembly.
- Inspect each level of the assembly for required labels, wire routing, screws with critical torque specifications, and continuity test points. This becomes especially important for areas of the product that will not be accessible after the next level of assembly.
- Continue through each level, or layer, of the assembly.
- Conduct a final inspection prior to installing the covers of the assembly.
- Test the device and record the results.
Although some simple box builds may satisfactorily pass their final test with a simple PASS/FAIL, a quality CM will usually gather more information than that. They will usually work with the test fixture and specifications you submit and develop a more comprehensive test procedure. Although this costs the CM in extra, up-front preparation, it will usually pay great dividends at the conclusion of the project by helping to reduce errors and returned materials.
Having Your PCBA CM Build Your Electronic Enclosures
A box build assembly at VSE.
Having your printed circuit board assembly contract manufacturer build your circuit boards and your box build together will save you much more than just time and expense. With all of the different pieces of your final product being built to fit together under one roof, you will realize a much higher level of quality in your build. It can be very easy for something as simple as a rotated connector to be missed in the data exchange between vendors. This often results in a connector not fitting in the final build, which will set your project back significantly in its delivery schedule.
At VSE, we are a single-source vendor solution for your PCBAs and electronics box builds. In addition to testing each system component for individual functionality, such as the circuit boards, we will also be testing them again combined in the completed system. This gives us the unique ability to completely test and debug your system.
You also won’t have to worry about managing information, specifications, parts, and materials between vendors, because we will be handling all of that for you. With our adherence to copy exact rules, we will not make changes in your documentation without first working with you. This will ensure your final box build has a full and accurate “as-built” set of documentation, allowing you to track the true and current built state of your device.
