Tips for Designing a Medical Device PCB

April 12, 2021

Designing a medical device printed circuit board (PCB) is not easy. Even medical equipment manufacturers need to invest large amounts of money on research and development in order to develop state-of-the-art prototypes. 

Competition is fierce, and clients demand the best from their electronic devices. Here, we will provide some tips that are used by medical equipment manufacturers in order to design cutting-edge PCBs for life-saving medical devices.

Modifications Are Normal

Everything will likely not go according to plan during the first spin. All traces should be available from the topmost layer. If they are not accessible, then they will be hard to solder to. They will also be hard to cut if they are not accessible from the top layer. In fact, you will run into issues with scraping away the solder mask as well.

Test points and vias should be noticeably large. It is more than likely that you will need to solder jumpers to them at some point, so it is best to play it safe and ensure that they are sufficiently large before you start working on them.

Components should not be placed too close to one another. Tightly spaced components will make it hard for you to make modifications if needed. When you are working on your layout, feel free to take up the entire board, as the extra space will make it easy to make adjustments.

Make Your Board User-Friendly

If your board is not easy to debug and test, then you will run into problems in the future. We would suggest that you add several test points. You may want to add them to the output of your power supply. Your signal traces may also benefit from a few test points.

Place some test points on the side of the board as well. Ensure that they are affixed to the side of the board that is exposed while the board is set in the assembly. By doing so, you will be able to run tests with ease.

Give Your Old Circuits a New Lease on Life

You may have a sub-circuit from an older design that would work wonders on your present project. You can give it new life by reusing it for your current project. For instance, power supplies can usually be transferred from one design to another with relative ease.

Some designers prefer to work from scratch, but why not save money and time by recycling old circuits from previous designs?

Play it Safe

You may run into a sub-circuit or component that you may need, but are not sure of yet. For example, you may think that an RC low-pass filter may work well at a given analog input, but you are not 100% certain.

In such a scenario, you may want to consider leaving it out for the time being and instead place a zero-ohm resistor in place of a bona fide resistor. By doing so, you will avoid the problem of having an exposed or open circuit.

Copper Is Gold

Copper is a god-send when designing medical device PCBs. We would suggest that you place a ground plane on all of the layers. Your ground planes should also be attached together using a myriad of vias.

Ground planes should be dichotomized if you are working with both digital and analog sub-circuits on your board. Splitting them will help reduce the amount of noise that the digital circuits will relay onto your analog variants.

Design for Serviceability

While you are working on your boards, you will be re-routing ad nauseum. While you delve into the minutia of component placement and routing, it is easy to forget the elements that are most apparent to the individuals who will actually be assembling your medical device.

Perhaps, you may be one of the people involved in the assembly, dismantling, and re-assembly of the device in question, but it is easy to forget to design for serviceability and ease of assembly. For example, you should ensure that the connectors are arranged in such a manner that a person can easily use their hands to reach into the assembly in order to mate the connectors to their cables.

If you have pads that are affixed to ground fills, then they should have thermal relief connections in order to facilitate solderability. A 3D model of your board should also be exported so that you, or someone else, can perform a virtual fit test.

Safety Should Be Your Top Priority

Medical device assemblies may be exposed to a plethora of different materials including, but not limited to, extreme temperatures, shock, and toxic liquids. Many medical devices will also be implanted into the patient’s body. At the very least, they will be placed on the patient’s body, so a malfunction can prove fatal. The last thing you want is a medical malpractice lawsuit on your hands.

The pandemic that hit 2020 has also increased the need and demand for optimal hygiene, and medical devices are no exception. The medical device PCBs that you design should strongly consider the need for cleanliness.

Medical devices must be easy to disinfect and clean, as most will be used on a daily basis. Stainless steel is commonly used in order to enclose medical devices, as it is easy to clean. Conformal coating is another viable option, as it will protect against saline spray, corrosion, dust, moisture, and contamination.

You also need to consider interactions with other medical devices when designing your PCBs. For example, noise emission may cause design issues down the road, and you do not want your medical device to interfere with someone’s pacemaker.

Circuits Central

If you would like to learn more about medical equipment manufacturers and PCB tips for medical devices, then please visit Circuits Central at our website. We can also be reached at 1-888-821-7746 for a free, no obligation quote and consultation.

Circuits Central has extensive experience in manufacturing medical imaging, healthcare, laboratory research, monitoring and communication, and chemical analysis equipment.

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