Solving Medical Device Design Issues with Flexible Printed Circuitry

Wearable and portable medical devices provide continuous real-time feedback, helping make telehealth possible. For example, sensors within wearable mobile devices can remotely monitor health indicators, such as blood glucose, blood pressure, heart rhythm, pulse and other vital signs. Technological advances have made it possible for designers to develop mobile medical devices that not only monitor but also diagnose and provide therapies within a patient’s own home—away from hospitals and other healthcare facilities

Next-gen mobile medical devices must be comfortable to wear and able to withstand the rigors of a patient’s everyday life. At the same time, they must transmit and receive accurate data. These requirements often conflict, creating significant design challenges. Below are three such issues engineers need to consider when designing today’s medical devices.

In order to promote patient use, devices need to be compact and comfortable. This, in turn, creates a need for lightweight circuitry that fits within tight spaces. For example, it must be able to bend or flex in order to maximize space and efficiency.

Flexible printed circuit (FPC) and flexible printed electronic (FPE) solutions are proven technologies from consumer electronics that have entered medical device designs. Because they help optimize space in tight packages, FPCs and FPEs are effective in products such as insulin pumps, wearable patient monitoring devices, portable defibrillators and continuous positive airway pressure (CPAP) machines, which are used to treat sleep and breathing disorders.

FPCs and FPEs are three-dimensional, so they can bend around packaging and fold to fit in miniaturized enclosures. Other advantages include flexible substrates with single-sided, double-sided and multilayer circuitry, which are ideal for high-performance signal and power connections. And as device package sizes continue to shrink, flex circuits must adapt. Incorporating features like blind and buried vias can help retain flexibility as the device package size continues to decrease.

In short, high-reliability flex circuits are excellent choices for small, lightweight designs with complex, high-density circuitry. Significantly thinner and lighter than traditional circuit boards, flex circuits make products lighter, contributing to patient mobility and comfort.

Rigid circuit boards containing woven glass fibers tend to result in signal loss. On the other hand, materials used in flex circuits, such as polyimide, help maintain signal and power integrity. For example, polyimide dissipates heat quicker, so the flex circuit requires less cooling to maintain signal integrity performance. Additionally, flex materials closely match thermal expansion rates, which makes them more reliable in hot and cold temperature extremes, the kind of fluctuations found in mobile healthcare applications.

A well-designed mechanical package that performs consistently, is mechanically sound and promotes airflow may include a wide variety of electronic components, including connectors, transmitters, receivers, resistors and capacitors. Unlike rigid circuit boards, which only allow circuit traces in the X and Y planes, flex circuits allow designers to route circuits along curved surfaces and in multiple directions on any axis.

Designing an effective package is a collaborative process involving device designers and their suppliers. Molex works with its customers to optimize signal strength and mechanical integrity with flex circuit routing.

Additionally, optimized package designs may call for “rigid flex” circuits, which include both rigid and flexible substrates laminated together in a single structure. For example, there may be a section of the device with several electronic components—resistors, capacitors, connectors, processors—that is rigid, but a flexible electrical “tail” leads from the rigid section, eliminating the need for an interface connector.

As medical technology continues to expand, digital connectivity will bring opportunities for device designers to build new devices that help reduce healthcare costs. It’s clear that flexible circuits will play a key role in that process. Molex has the expertise to help clients that are committed to delivering the next generation of medical diagnostic technology.

Learn more about Flexible Printed Circuits (FPC).