An Inside Look at Flex PCBs for Wearable Technologies

Wearable technology has become an increasingly vital device category in the last few years, thanks in large part to the popularity of fitness trackers such as Fitbit, Jawbone, and smartwatches like the Apple Watch and Pebble. As the demand for smaller, lighter products increases, flex PCBs are often the best candidates for fulfilling all of these technical requirements.

Let’s look at applications in the medical sector for a moment to understand the scale of this opportunity. According to a June 2015 report from Global Industry Analysts, the U.S. market for wearable medical tech alone is projected to reach around $4.6 billion in value by 2020. The main drivers of this trend include not only the growing number of patients with conditions such as diabetes, but also what the study’s researchers called “developments in flexible electronics to benefit innovation in wearable devices,” i.e., more capable modern flex PCBs.

Still, many companies have limited experience when it comes to flex PCBs. From selecting materials to getting finer lines and traces, coming up with a top-notch flex PCB for a wearable application, whether in medical or some other vertical, can be challenging both for the designer and the supplier. What can be done to ensure that your flex PCBs properly support wearables in a rapidly growing market?

The challenges and requirements of flex PCBs for wearable technology

In a recent interview, flexible circuits expert Vern Solberg touched upon some of the top emerging use cases for wearables, including functional devices designed for military personnel and medical professionals, such as heart monitors. Moreover, he noted that flex PCBs were evolving so that they could be used in the medical industry for applications including medicine delivery systems and wristwatches that can keep tabs on circulatory and respiratory system data and send it to the wearer’s cardiologist.

As far as the flex PCBs within these devices go, Solberg explained that the small scale required by common flex applications means that everything inside is becoming tinier, which can create some significant challenges in the PCB process.

“[The flex PCB teardowns I have seen are] shrinking everything,” he said. “So they are challenging the supplier to perhaps go to finer lines and spaces, thinner copper, thinner base material, and all of this really has to do with the application. They absolutely need a very thin, very small form factor, and so they are pushing the limits of what the supplier can build.”

Along similar lines, Solberg acknowledged that “non-mainstream” copper was becoming more common in flex PCBs as a way to work around some of the limitations of traditional alloys. For example, even copper with a decent bend radius may become more brittle over time, resulting in microcracks. Some companies have actually turned to buildup copper instead of rolled copper (which requires a direction of the grain) to address such issues while also getting finer lines and traces. Solberg stated that it is not clear whether rolled or buildup copper was ultimately more robust.

Flex PCBs are bound to keep pushing the envelope as wearable applications become more advanced and widespread. To get started on your path to an optimal design, contact Sierra Circuits today and also be sure to look at our many flex PCB resources.

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