Medical PCB: Class 3 Circuit Boards Used in Medical Electronic Devices

Medical devices and equipment have advanced in power and functionality over the years. The underlying technology that supports this advancement is in the circuitry. While they accommodate more components and electrical pathways, medical PCB have shrunk. How is this possible? We will look at these circuit boards in detail, including design tips for your project. Let's get started!

What Are Medical PCBs?

Medical PCBs are circuit boards used to run the circuitry of electrical equipment used in the medical industry. As medical equipment becomes more computerized, complex, and compact, they require boards with high-density circuits.

Therefore, a medical printed circuit board should pack electronic components and connections in a compact space while maintaining reliability. So, most of them are HDI (High-Density Interconnect) PCBs.

A high-density PCB

Also, most medical devices do not conform to the usual designs. Therefore, their PCB size and shape should match the device, meaning most PCBs for critical medical equipment are flex or rigid-flex.

A flexible PCB

Benefits of Medical PCBs

Mobile Health

Medical devices like fingertip pulse oximeters and blood glucose meters have enabled mobile healthcare in people’s homes, the streets, and medical camps in remote areas. You can even buy such devices and keep them at home for personal use because they are affordable, easy to carry, and easy to use.

A portable pulse oximeter

Health Record Management

Medical PCBs have introduced health record digitization, which has simplified record keeping and patient data access on the fly. Previous manual record-keeping made it difficult to access a patient’s medical history to help in accurate current and future treatments, resulting in high mortality rates.

Wireless Communication

Medical systems and devices currently use wireless communication to send data to mobile phones or servers for remote diagnosis. A doctor can learn about a patient’s condition remotely, with the implanted device sending data for critical monitoring.

Wearables

Devices like smartwatches, fitness trackers, blood pressure monitors, and ECG monitors can monitor the health state of patients, footballers, athletes, and regular people in general, giving real-time feedback to the user or medical officers.

Data-Based Drugs

Since medical PCBs make it easy to monitor, gather, and analyze patient data, the pharmaceutical industry can easily produce the drugs required in the market at the required rate.

Applications of Medical PCBs

• Cardiovascular medical equipment (defibrillators, pacemakers, heart monitors)

A pacemaker

• Medical imaging systems (ultrasonic equipment, MRI, CT scans)
• Blood glucose monitors
• Body temperature monitors
• Electrical muscle stimulation equipment
• Medical instruments for collecting research data and test results

Requirements For Medical PCBs

Electrical

Medical PCBs require processing and amplification at extremely low voltages (microvolts), so the electrical design must reduce leakage currents in bias circuits, include proper grounding, shielding, and filtering, prevent digital switching noise in analog sections, and have a layout/stack that maximizes signal integrity.

Component derating, EMI and ESD control, isolation barriers, spacing, and safety are also important factors.

Mechanical

The PCB should have conformal coatings to prevent surface-mount cracks, solder joint strengtheners, zero fragile chip packages like BGA, and thermal management features to keep the operating temperatures low.

Manufacturing

Medical boards should be built using biocompatible PCB laminates, component leads, solder masks, adhesives, and surface finishes. Hygiene and cleanliness are also important to prevent circuit contamination that can affect the board’s performance and reliability.

Developing modern electronics for medical applications

Before the board leaves the factory, it must undergo AOI, solderability, peel, ionic contamination, micro-sectioning, TDR, flying probe, and X-ray testing for internal features.

Regulatory

Countries and regions have different regulatory measures for electronic device production, which must be met to sell devices with medical PCBs there. Some common ones include UL, IEC, CE, FDA, and ISO (quality management).

Medical PCB Technologies

As medical devices advance, they contain at least one of the following technologies.

IPC Class 3

Class three boards for high-performance electronic products should have no downtime. Reliability is a critical factor here, meaning medical PCBs should have the following features.

• Zero annular ring breakouts
• 1-mil minimum plating in the thru-holes
• Tight tolerance on conductor width and spacing

Via-in-Pad/ HDI

A high-density interconnection makes it possible to reduce the printed circuit board size.

5-mil Spaces/Lines and Below

IPC class III needs minimum line width reduction during processing. So, the medical PCB manufacturer should have laser-direct imaging and other such equipment to achieve the required production yield.

An MRI scanner

Laminate Requirements

FR-4 is the most typical PCB laminate. But medical boards are not like the usual PCBs. Therefore, you require an Electronics Contract Manufacturer (ECM) with expertise in ceramic, polyimide, Teflon, and other high-quality materials that meet the board's unique requirements.

Free PCB DFM Devices

DFM (Design for Manufacturability) compiles all PCB layout topologies to minimize issues during fabrication and assembly. Doing DFM before making prototypes is essential to avoid returning to the drawing board.

A blood sugar monitor

Tips for Medical PCB Design and Assembly

Consider these factors if designing medical devices with PCBs.

Safety First

Medical devices might get exposed to extreme temperatures, liquids, or shock in their operating environment. For instance, implantable devices like pacemakers live inside the human body. Any malfunction caused by this exposure can be catastrophic.

A pacemaker placement in the human body

Additionally, these devices need to be easy to disinfect and clean. So, they should have an enclosure material that can withstand ozone cleaning and disinfectants.

Stainless steel is the most typical material used for this task. The enclosure or coating should also protect the PCB from dust, contaminants, corrosion, moisture, and salt spray.

Lastly, there is the noise emission issue. Critical devices, such as pacemakers, should not experience interference.

Comply with the Standards

As stated earlier, medical equipment and devices fall under class 3 electronics. So, they must adhere to strict standards.

Besides looking for a manufacturer who can meet all class 3 requirements, it is vital to keep detailed records of test and inspection processes. You can use FDA or ISO standards as benchmarks for this process.

If you rely on your ECM to do the record-keeping, ensure they are capable and can handle the process. Remember that these record-keeping mandates are open-ended and might require you or your ECM to keep them for long periods.

Other quality standard requirements include installation, operation, and process qualification. For instance, if fabricators move machines physically within their premises, they must re-qualify them in their new locations. Why? They must prove nothing changed and the manufacturing process runs just as or better than before.

A PCB assembly line

Most ECMs like taking shortcuts here to cut costs. So, it would be best if you vetted PCB manufacturers to get a reliable ECM that builds consistent quality products.

Be Ready To Live With Obsolescence

Reliable PCB fabricators should predict component obsolescence using component database software like SiliconExpert and always be on the lookout for component availability changes, especially for life-saving products.

A CT scanner

If you find out at the last minute that a component has gone obsolete and the device requires a significant design change, you might have to go through the approval process again. And as you know, approval from federal agencies takes time.

Thru-Hole or SMT?

Knowledgeable and experienced medical-grade PCB manufacturers will implement the right technology that meets your needs. Most modern PCB designs use SMT electronic components to create compact boards.

Thru-hole and SMT components on a PCB

However, thru-hole assemblies are critical for power requirements and connectors due to their physical strength. So, the manufacturer should implement the best technology that suits each board section.

How Small Can You Go?

The general trend with electronic devices is shrinking. Therefore, your contract manufacturer should build compact packages that fit in tiny equipment.

And they should have the required machines for placing components on compact boards. But there are limits. For instance, considering surface-mounted parts, the smallest package in the market currently is 0.25 mm × 0.125 mm.

Since there are multiple factors to consider, you should get a reputable, skilled, experienced, and trustworthy PCB manufacturer.

Challenges for The Medical Industry and Medical PCBs

Anything related to the medical industry is highly regulated globally because human life is paramount. This places a big challenge on PCB manufacturers, who must adhere to high safety standards while ensuring the boards are reliable and exhibit consistent quality.

To meet the required regulatory standards, your PCB manufacturer must go through method validation, where the manufacturing process must be approved after inspections.

High-precision robots in a PCB production factory

These fab houses must also undergo a facility approval process, which ensures all the equipment is in order, properly maintained, and calibrated.

Parts limitation is a big issue in this industry because the boards require precise parts and materials to deliver the required performance.

Overall, the production costs of medical PCBs are higher than those of making regular boards because of the three factors above, which creates another challenge: cost. These costs are unavoidable, so the end product will have a relatively high price.

Considerations for Manufacturing Medical Equipment PCBs

• Assess and plan the lifespan of medical devices during PCB design
• Plan quick timelines for product launches because the market is competitive
• Do a detailed corner case evaluation during the medical device's operation
• Put user safety as the primary concern during the design, fabrication, and assembly of medical PCBs
• Ensure the PCB meets all medical industry and regulatory standards
• Output consistency is vital when designing monitoring or diagnostic medical electronic devices
• Usability is crucial to consider when designing implantable or wearable devices
• Understand the effects of the debris left behind by medical devices and follow up with the required maintenance steps

Types of Medical PCB Assembly We Can Offer

Single Layer Medical PCBs

These circuit boards have one copper layer mounted on a single substrate layer, forming the most basic circuit board. They are cheap to make but only have a small circuit that can handle non-complex tasks.

Double Layer Medical PCBs

Double-layer PCBs can accommodate double the circuit the single-layer type can accommodate, which means more components to handle more complex functions.

Multiple Layer Medical PCBs

With at least three copper layers, multilayer boards are the most complex and expensive but can host large circuits to run multiple complex, high-speed, high-frequency functions.

Multilayer PCB structures

Rigid Medical PCBs

These boards cannot flex or stretch and are the most common type of circuit board in general. However, they have limitations because they might not fit in wearables that wrap around the wrist or circuits that must fit in tight spaces.

Flexible Polyimide PCBs

Medical devices with small form factors benefit greatly from developing flexible PCBs because they can fit into tight spaces.

Polyimide is an excellent choice for the PCB substrate because it is flexible, thermally stable, chemical resistant, and has the required tensile strength to make the circuit durable.

Flexible Metal Clad PCBs

These circuit boards are the high-power versions of the flexible polyimide type because they can handle higher power levels due to the metal’s quick heat dissipation properties. Typical applications include surgical scanning and lighting.

Rigid-Flex PCBs

Some medical devices, like wearables, might need a hybrid PCB setup. In this setup, the chip and critical components reside in a rigid PCB behind the display panel, while the rest of the circuit is in a flexible board around the wrist.

This design creates a more robust device that can handle complex tasks while being compact and flexible.

A flexible PCB

Ceramic PCBs

Ceramics in PCBs is more thermally conductive than metal because it doesn’t require an insulation layer.

The material also has a low CTE, making ceramic PCBs ideal for medical devices operating in high-temperature areas.

Chemical resistance and high-frequency performance are some of the ceramic’s strong suits.

HDI Microcircuits

These multilayered PCBs deliver incredible performance in tiny form factors because they host multiple components. They are common in wearables and hearing aids.

Why Choose OurPCB as Your Medical PCB Manufacturer

Medical PCBs require special care during production and assembly, and we emphasize the electrical, mechanical, manufacturing, and regulatory requirements to ensure you get the best high-quality medical PCBs for your project, products, and customers.

We also have highly skilled personnel who ensure these requirements are met when making either of the PCB types listed above.

Wrap Up

There you have it! Medical PCBs have grown in complexity to enhance the performance of modern medical equipment. So, you must adhere to strict safety and industry standards to ensure the devices are safe for internal and external human body use.

We hope the tips above will help you in the medical PCB design and assembly process. You should consider us for your ECM. Contact us for further information about your PCB.