Why PCB Prototyping and Testing Matters: A Real-World Product Development Example

When developing or improving an electronic product, it can be tempting to think that a small PCB change should be relatively straightforward.

If the enclosure isn't changing, the majority of the electronics are staying the same and the new components appear to fit, why would you need to prototype the whole product again?

A recent project at Bates Product Design provided a good reminder of exactly why thorough PCB testing and physical prototyping are so important — even when making what appears to be a relatively small change.

Improving USB-C charging compatibility

We were working on the second iteration of an existing product. The main objective of the redesign was to improve the device's USB-C charging compatibility.

The original product would reliably charge from 5V 3A USB-C chargers, but newer USB-C fast-charging power supplies have become increasingly common. The product needed to be updated so that it could reliably charge from a much wider range of USB-C power supplies, rather than requiring users to have a particular type of charger.

This required changes to the charging electronics and PCB.

While making those changes, we also wanted to improve the mechanical reliability of the USB-C charging port. The connector is a part of the product that receives regular physical use, so selecting a stronger connector made sense as part of the redesign.

We therefore selected a new USB-C connector and updated the PCB to accommodate it.

On paper, the change looked straightforward.

The new connector was suitable for the application, the PCB footprint was correct and the electrical requirements had been addressed. The enclosure itself wasn't being redesigned, so there didn't initially appear to be a significant mechanical risk.

There was, however, a subtle difference between the old and new connectors.

The new connector was slightly different in its shape and overall dimensions.

That difference wasn't particularly obvious during component selection, and because the enclosure was remaining unchanged, it wasn't identified as a problem during the initial manufacturing review either.

It was only when we built the physical prototype that we discovered the issue.

The problem appeared during assembly

When the new PCB was installed into the existing enclosure, the slightly different geometry of the charging connector caused it to catch against the enclosure.

This meant that the PCB couldn't simply be installed in the same way as the previous version. As force was applied during assembly, that force was transferred into the USB-C connector and its connection to the PCB.

The result was a failure that we hadn't anticipated from the PCB design alone.

The charging connector was pulled away from the PCB, taking part of the top layer of the board with it.

Interestingly, the connector had been selected partly because it was mechanically stronger than the previous version.

The problem wasn't that the new connector itself was weak. The problem was that its slightly different geometry created an interaction with the existing enclosure that hadn't previously existed.

This is a good example of why looking at individual components in isolation isn't always enough.

A PCB doesn't exist in isolation

When designing a PCB, it's natural to focus on the electronics first.

• Does the circuit work?

• Are the components correct?

• Is the footprint suitable?

• Does the charging circuit behave as expected?

These are all important questions, but they are only part of the overall product.

The PCB also has to physically work within the product around it. It needs to interact correctly with the enclosure, connectors, fixings, cables, buttons, batteries and other components. It also needs to accommodate the way the product is actually assembled.

In this case, the electrical design was doing what we expected. The new connector was suitable for the PCB and achieved the required design objectives.

The problem only became apparent when the PCB, connector and enclosure were brought together as a complete assembly.

That is something that can be difficult to identify from a schematic or PCB layout alone.

Why physical prototyping is so valuable

This is where physical prototyping becomes particularly important.

At Bates Product Design, we consider prototyping an important part of the product development process, rather than simply a final step before manufacturing. Our wider development process includes design, engineering, prototyping and manufacturing, allowing potential issues to be identified and addressed before production.

A prototype allows you to test the assumptions made during the design process.

In this case, we could physically assemble the revised PCB into the existing product and see how the new connector behaved.

That immediately exposed an issue that wasn't obvious from the individual component specifications.

It also allowed us to understand the failure properly.

The problem wasn't simply that the connector had come away from the PCB. We could see that the geometry of the new connector was causing interference with the enclosure, which was creating an excessive mechanical load during assembly.

That distinction is important because it means the underlying cause can be addressed rather than simply repairing the damaged board.

Small changes can create unexpected problems

This is particularly relevant when working on an existing product.

There can be a tendency to think that because you're only changing one component, the risk associated with that change is relatively small.

In reality, a product is a system of interconnected parts.

Changing one component can affect something that hasn't been changed at all.

A different connector can affect the enclosure clearance. A slightly taller component can interfere with another part. A different battery can change the mechanical layout. Even a small change to the PCB can affect cable routing, assembly or how forces are transferred through the product.

The fact that the enclosure hasn't changed doesn't mean that the enclosure isn't affected by a PCB revision.

In our case, the enclosure was exactly the same as before. The change was entirely on the PCB and charging connector, yet the interaction between the new connector and the existing enclosure became the source of the problem.

Finding a problem in a prototype is a success

It can be frustrating when a prototype doesn't behave as expected, but this is actually one of the most valuable outcomes of prototyping.

The purpose of a prototype isn't simply to prove that the design works. It's also there to show you what you haven't considered. In this case, the prototype allowed us to identify the problem before production. We could investigate what had happened, understand the interaction between the connector and enclosure and make the necessary changes to the design.

Finding that issue at this stage is significantly better than discovering it after hundreds or thousands of products have been manufactured.

A problem identified during prototyping can often be solved through a relatively simple design change. The same problem discovered during production could potentially result in rework, wasted components, changes to the assembly process, production delays or products failing in the hands of customers.

Testing should reflect the real product

One of the key lessons from this project is that PCB testing shouldn't only mean testing the electronics. Of course, the electrical performance needs to be checked. In this case, that included making sure the redesigned charging system could achieve the intended USB-C compatibility. But the physical product also needs to be tested as an assembly.

• Can the PCB be installed correctly?

• Does the connector clear the enclosure?

• Does anything catch during assembly?

• Are excessive forces being applied to the PCB?

• Does the connector remain secure?

• Does the product behave as expected once all of its components are assembled together?

• These are questions that become much easier to answer when you have a physical prototype in your hands.

Prototype, test, learn and improve

The outcome of this project wasn't simply a better charging system. It was also a reminder of the value of testing the complete product whenever a change is made

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The original objective was to improve USB-C charging compatibility and allow the product to work with a wider range of modern USB-C power supplies. Alongside that, we wanted to improve the mechanical reliability of the charging port.

The PCB redesign addressed the electrical requirements, while the prototype exposed an unexpected mechanical issue with the new connector. That's exactly what we want a prototype to do. It is much better to discover a problem while you are still developing the product than to discover it once the product is in production.

At Bates Product Design, we work across product design, engineering, PCB and electronics design, prototyping and manufacturing, so we can consider these different aspects of a product together rather than treating them as separate stages.

The lesson is simple:

Don't underestimate a small design change.

Even if the electronics are correct, the component is suitable and the enclosure is unchanged, bringing everything together physically can reveal problems that aren't obvious on a screen.

Good product development is an iterative process:

Design → Prototype → Test → Learn → Improve → Repeat.

And sometimes, the most valuable thing a prototype can tell you is that something you thought would be fine actually isn't.