Flexible PCBs: Enabling wearable technology | Global Sources

by Vianie Li & Cecile de Veyra

Wearable electronics have come a long way from calculator wristwatches in the late 1970s to today’s current crop of fitness bands, smart watches, glasses, jewelry and clothing, and medical devices. They have increased in functionality, with some configurations that can be implanted or skin-mounted, and continue to do so while continuing to trend toward further miniaturization.

Making all this achievable is flexible PCB technology. Also called flex circuits or prints, they are thin, light and pliable, and can reduce the number of connectors, minimizing space, weight, assembly and maintenance time, and overall costs. Because of these qualities, they can withstand vibrations and bending without performance degradation, in addition to having enhanced resistance to very high and low temperatures, moisture and corrosion.

With the fast development of 5G communications and the Internet of Things, wearables have become a sizeable market that is still expanding. They were valued at $27.91 billion in 2020 and are projected to reach $74.03 billion by 2026, according to Mordor Intelligence.

Based on data from Huaon, a specialist research firm from China, global shipments of wearables totaled 533.6 million units in 2021, posting a jump of nearly 20 percent YoY, and are expected to go up to 637.1 million in 2024. Smart watches had the most impressive performance, reaching 128 million units in 2021 from 21 million in 2016 and registering 43.55 percent CAGR.

In China, wearables shipments also rose significantly, hitting 140 million units in 2021 or increasing by 27.3 percent YoY, according to Huaon. In-ear devices accounted for 78.98 million units, smart watches 39.56 million and smart bracelets 19.1 million.

Demand for wearables is expected to rise further, which will fuel growth of the flexible PCB sector worldwide. Huaon projects flex circuits will be in the scale of $28.7 billion by 2025, more than double their market size in 2019 which reached $13.8 billion. In China, this is expected to increase shipments for wearable devices by 15 to 20 percent.

This upbeat outlook for the category is encouraging Chinese manufacturers of flexible PCBs to expand their product ranges, currently dominated by single- and double-sided types while kinds with up to four layers are also widely used.

Suppliers interviewed by Global Sources expect that four or more layers will be popular in the years ahead. Two of them, Jiangxu Zhihao Electronic Technology Co. Ltd and DNC Precision Co. Ltd, already have four-layer units in their catalogs.

New rival technologies

Considered an ideal alternative are polymer nanomaterials, which are “mechanically flexible, conductive, biocompatible, and capable of self-healing,” according to Akanksha Urade in an editorial posted on AZoNano. “Conductive polymers include polyacetylene (PA), polyaniline (PANi), polypyrrole (PPy), polythiophene (PTh), and poly (3, 4-ethylenedioxythiophene) : polystyrenesulfonate (PEDOT:PSS) and dielectric polymer includes poly vinyl alcohol (PVA), polydimethylsiloxae (PDMS), polylactide (PLA), polycaprolactone (PCL).”

Further developments in this sphere, called flexible electronics, will definitely benefit the medical world, which “will witness many innovative devices such as electronics skin, flex circuits in contact lenses, and health monitors in the near future.”

Until then, industry analysts are confident that flexible PCBs will remain first choice in the wearables market in the short term.

Mainstream flex circuits

Flexible PCBs that can be sourced from Chinese manufacturers include single-sided to four-layer variants. They typically have 0.2mm minimum hole size, 1oz copper and 1.4mm board thickness. Materials used such as polyimide, copper and adhesive are sourced domestically.

Custom specifications are widely accommodated, products based on which account for 20 to as much as 50 percent of total shipments. To cater to a more diverse range of requirements, suppliers will develop flex circuits that are ultrathin but have higher than four layers.

Most companies offer CE-approved, UL-listed and RoHS-compliant products.