How to Design and Manufacture Custom Electronics

In 2018, I embarked on a project to build an IoT sensor platform. It started with an idea, and two years later, it became a real working device manufactured at scale.

This post presents a workflow for rapid design and prototyping of electronic components, along with pointers for transitioning to mass production.

Defining Success Criteria

Define a clear, verifiable set of criteria of how your product should perform. This includes functional requirements such as, “The product shall have a speech interface,” and non-functional, such as “Must run off 230V and 120V AC power”. Make the criteria quantifiable so it can be validated. Consider ways to automatically test your designs.

Be careful not to do any actual design when defining these; they are strictly to set boundaries.

Iterating Approaches

Once the boundaries are defined, it’s time to figure out what goes in the box. By this stage, you’ll likely have some design in mind. For complex projects with many potential solutions, challenge your team to create multiple designs. It’s easy to arrive at a local optimum with a greenfield design. Iterate. Strive to shed complexity.

For instance, our product’s initial prototype used an x86 PC board, the next iteration had an embedded ARM system running Linux, and the final product had no operating system, just an SoC running our code on bare hardware.

Picking Components

For simple projects, a quick way to find and prototype components is to use a ready-made board designed for the Arduino or Raspberry Pi. They can be found on Amazon or from places like adafruit. The added benefit is that they will often include a ready to use driver and a schematic.

For more sophisticated designs, you’ll need to dig deeper. In our case, we had to find an ADC chip that had a high sampling rate and a low noise floor.

Sites like Digikey and Mouser offer convenient filtering tools to narrow down your search.

A product data sheet is a trove of vital information. It will define performance characteristics and interface nuances. Be ready to read and understand every last word. For some components, this will be the only source of help.

Once a few candidates have been shortlisted, the next step is to test. A quick way to do this is with evaluation boards. Most part manufacturers offer these. They encapsulate the chip with everything it needs to run (such as power and IO interfaces) and provides simple software to test its performance.

We set up a test environment where we could plug in evaluation ADC boards to a signal generator and capture results in a consistent, repeatable way. We evaluated a few candidates until we found a chip that matched our desired performance.

Designing Your Board

Now that you picked the components, it’s time to integrate them into a design. There are two steps here: designing the schematic and laying out the actual PCB. There are several tools to accomplish this; some are proprietary such as Altium or Autodesk EAGLE, others open source like KiCad, yet others are vertically integrated with the PCB manufacturer like EasyEDA.

After evaluating a few packages, we settled on EasyEDA as it is feature-rich, free, web-based, and, made producing prototypes easy.

One thing to keep in mind is that most design tools have a finite library of components. This is because the software must know the footprint of each piece. Specialized or new parts will likely be missing. Fortunately, Digikey and Mouser will let you download models that can be imported into the design software. Search engines such as SnapEDA let you find community made models.

Design for Manufacturing

An essential consideration for building things at scale is logistics. Having to wait for parts to arrive from different suppliers or using parts with limited availability can introduce significant delays.

When designing your PCB and picking components:

• Minimize the number of suppliers.
• Avoid components that are nearing their End-of-Life.
• Make sure the components are available where the final assembly is performed (some parts from Mouser or Digikey are not available in Asia).
• Use surface mount components (SMT) as a through-hole assembly is more labor-intensive.
• Be mindful of manufacturing tolerances. Pick and place machines are not always perfect; leave enough space between components.

Manufacturing Boards

We live in genuinely amazing times when a PCB can go from being on screen to being in your hands within a few days. Multiple services will let you submit a design on Friday and deliver a ready-to-use board the following Wednesday. You can use a tool like PCBShopper to find PCB manufacturers.

Since we used EasyEDA, we relied on JLCPCB exclusively for PCB printing and assembly with great results.

Assembly

Populating a PCB with components, especially at low volumes, used to be a tedious process involving hand soldering or using a reflow oven.

Many PCB printing services now offer automated SMT assembly for a few bucks (provided your components are available in their stock.) In the case of JLCPCB, not all parts are available for automated SMT assembly, so your results can vary.

If you have to manually place a component during testing, consider using a larger version in the pre-production board to make it easier to assemble. Reduce manual assembly as much as possible as it is a potential source for defects.

Testing and Iterating

Once you receive your first test PCB, you should be prepared to make adjustments. Include test points so you can validate individual modules of your PCB. This will greatly simplify troubleshooting. You can also add jumpers to bypass sections.

Test points are also useful during mass production when a board is placed into a specially made jig to automatically check for defects.

Find a testing methodology that lets you save the results of each revision, so you will quantifiably track progress.

Conclusion

Building and manufacturing electronics is easier and more accessible than ever before. Even low volume manufacturing of custom electronics is now cost-effective. With powerful compute modules available at low cost, there are endless possibilities for new devices to perform previously impossible things. What will you build?

Please leave a comment below and thanks for reading!