The 5 PCB Design Golden Rules for Medical Device Rapid Prototyping

This article was originally published by Alvaro Rios, Head of Engineering - Medical Devices. This is an updated version.

At Focus, our Medical Devices hardware team, led by Julián Evia, works every day on pushing the boundaries of what's possible in implantable and wearable electronics. Over time, we've learned that when it comes to rapid prototyping of medical devices, success doesn't just come from technical expertise, it comes from discipline, collaboration, and good practices that make iterations faster and more reliable.

Together with Julián, we've tackled it all: rigid-flex PCBs for neurostimulators with many stimulation and sensing channels, miniaturized boards for insertable devices, and PCBs that power automated test equipment for manufacturing and development. But above all, we've specialized in speed—executing dense 8-layer designs that must be ready for manufacturing in no more than one or two weeks.

Validating a design idea through a prototype PCBA, whether it's a stimulation circuit, an AFE, the robustness of a PMC, or the efficiency of a wireless power transfer receiver, has often been essential to complement simulations and calculations, giving us empirical evidence of how things really work. Over time, beyond formal review processes, training, and work instructions, we've concluded that the following five rules are indispensable both to onboard new collaborators and to remind ourselves of what matters most when building hardware.

Treat Your Libraries as Sacred

If there's one thing that can make or break a prototype, it's library management. Inconsistent symbols or footprints don't just cause mistakes, they cascade into mechanical misfits, DFM issues, and even test failures.

That's why at Focus, we treat libraries as our most valuable asset:

• We enforce IPC-compliant footprints to guarantee compatibility with industry standards.
• All components go through peer-reviewed creation and updates, ensuring accuracy and traceability.
• Libraries are kept under version control in repositories, so every collaborator works with the same trusted source of truth.

This discipline pays off in faster iterations, fewer last-minute surprises, and greater reproducibility across projects. In medical device prototyping, where compliance and reliability are non-negotiable, solid libraries are the real foundation of every PCB.

Collaborate with the Mechanical Team from Day One

Imagine if, after testing and validating a PCB electrically, it doesn't fit in its enclosure or isn't capable of attaching a mechanical part in the correct position. We cannot stress enough how important it is to avoid this nightmare scenario.

In medical device prototyping, the mechanical and electronic worlds are inseparable. A PCB that works electrically but fails mechanically can stop a project in its tracks. That's why we emphasize early and constant collaboration with the mechanical team.

Some of the most common issues we've seen, and actively prevent, include:

• Vertical clearances: For example, when a charging or telemetry coil sits inside the case of an implant, the height of components must be carefully managed to avoid unwanted pressure on the coil once the device is sealed.
• Connector placement: If cable connectors are not right-angle, mechanical pressure from the case can damage solder joints or stress components.
• Electrode connections: precision up to μm is needed for correct alignment of the feedthrough connectors. Getting the mechanical team's input early on can save the project from small but catastrophic mistakes.
• Flex bending: Flexible sections of the PCB must be designed with their bending radius and strain points in mind, otherwise assembly can introduce cracks or early failures.

Rapid prototyping is not only about making boards, it's about de-risking the entire system. That's why we always plan for:

• Dedicated PCB builds for fitting tests, ensuring electronics and mechanics integrate smoothly before committing to final revisions.
• Rapid prototyping of metallic parts, including titanium enclosures for implants. With today's suppliers, especially specialized vendors in China, it's possible to receive custom titanium prototypes in just a matter of days.

Become a Jedi Master of DFM, DFA, and DFT

It may seem like deep Design for Manufacturing, Assembly, and Test (DFM/DFA/DFT) reviews only become critical once you're planning hundreds or thousands of units. But in reality, overlooking these aspects during rapid prototyping can make scaling, or even achieving manufacturability in the first place, nearly impossible.

This is especially true for miniaturized implantable devices, where physical constraints push designs to their limits. A poor decision on pad sizes, via ratios, or component accessibility can transform a feasible prototype into something that's almost impossible to manufacture reliably.

That's why, even at the earliest prototyping stages, we approach DFM/DFA/DFT with technical fluency:

• Ensuring enough test points and access for equipment.
• Using teardrops, controlled annular rings, and balanced pad connections to prevent defects like tombstoning.
• Plan panelization strategy early to reduce scrap and enable repeatable pick & place.
• Define controlled impedance stackups from the first prototype to avoid costly redesigns and compliance issues later.

By embedding manufacturability and testability from day one, we save time, money, and endless debugging later, while laying a realistic path for scaling.

Mastering Your CAD, Unlocking Rapid Prototyping

In rapid prototyping, true speed and reliability come from mastering your CAD environment. At Focus, we push Altium Designer to its full potential, not only by using its intuitive built-in features such as the Layer Stack Manager or the Release Manager, but also by integrating advanced capabilities like differential pair and impedance control and high-density via management for rigid-flex designs.

Beyond the standard toolset, we develop custom scripts that automate repetitive and error-prone tasks:

• library component revisions
• schematic and ERC validation
• BOM consistency checks
• silkscreen placement optimization

These scripts can even be integrated into a CI/CD server, ensuring that every commit or special condition automatically triggers the necessary design checks. Building the right infrastructure around the CAD environment, and making sure it runs smoothly across projects, becomes essential to achieve short, fast iterations with minimal room for error.

Combined with version-controlled libraries and integrated MCAD-ECAD workflows, as we mentioned before, this ensures every prototype is not just faster to produce, but also more reliable and ready for scale.

Embrace an Iterative Design Review Process

Even if it's the fastest rapid prototyping cycle in the world, never skip a review. At Focus, we've long adopted a collaborative hardware workflow where every project lives in Bitbucket repositories and all changes go through pull requests as part of a standardized peer review process. Each new circuit and feature gets its specialized review.

Reviews are not a single event, they are iterative and layered:

• Breaking down designs into small schematic and PCB modules for targeted feedback.
• Performing functional reviews of each circuit block.
• Performing non-functional reviews for implementation flaws.
• Running deep manufacturing file reviews, where tools like Altium Draftsman outputs become essential reviewer interfaces.

These are just a few of the things we've learned over the years. We'd love to hear about other experiences and any good practices to follow or bad habits that should be avoided.

Let's keep talking about the art of designing PCBs!