Connectors Get Smaller, Tougher for Wearables
Wearable electronics - whether they are smart watches, smart glasses, personal health monitors, or electronics embedded in clothing - continue to be one of the biggest sectors driving demand for miniature connectors that are able to withstand the rigors of a wide range of environments. Connector suppliers have responded with parts that tolerate extremes of temperature, humidity, and moisture while providing tiny form factors that are able to reside within cleverly packaged electronic devices.
The wearables market is booming, with sales expected to grow from $20 billion in 2015 to almost $70 billion in 2025, according to market research firm IDTechEx. The sector includes devices such as glasses, jewelry, headgear, belts, armwear, legwear, skin patches, exoskeletons, and e-textiles, with healthcare as the dominant sector for these products, merging medical, fitness, and wellness.
“For wearable medical devices, demand appears to be consistent and growing moderately,” said Hank Mancini, marketing manager for Affinity Medical Technologies. “Most of the connectors that we have designed are for ambulatory monitoring devices. Each new device tends to be smaller than previous generation devices, which makes connector design more challenging.”
Many connectors are already available for wearable electronics. A recent paper titled “The Challenges of Wearable Electronics,” by Nick Langston, head of TE’S Wearables Lab and Manager of Business Development and Strategic Partnerships for TE Connectivity, noted that a number of connector solutions exist for smart watches – micro USB connectors, board-to-board connectors, board-to-flexible printed circuit connectors, card connectors, battery connectors, and custom cables to name a few.
But with space inside wearable electronics at a premium, specialized solutions such as molded interconnects that integrate circuit traces, shielding, and ground planes, are needed.
Smaller connector sizes are a must in the medical industry. At the same time, the influence of consumer electronics is being felt in medical connectors. “Smaller connectors designed to look more like the ones used in consumer devices are very popular,” said Mancini. “Smartphones has had a major impact on design expectations for wearable devices and the connectors associated with those devices.”
The boom in wearable connectors has benefitted makers of board-to-board and board-to-flex connectors, according to Langston. “Board-to-board and board-to-flex connectors have been popular in wearables from the start,” he noted. “They enable connections between the display, sensors, power and data modules. The Apple Watch, for example, has five different internal connectors – six if you include the proprietary watch strap connection point.”
TE Connectivity offers connectors with spring finger contacts that save space in wearable electronics.
TE Connectivity has developed a line of spring finger contact connectors that provide grounding between a device and a printed circuit board (PCB). According to Langston, these connectors enable the user to have the number of contacts in the locations they desire in a range of heights. “Because of the overwhelming need to miniaturize electronics, there is a driving need to design in connectors with as few pins as possible. No one wants to use an eight-pin board-to-board connector when they only need to connect four pins.
Other examples include new designs from Neoconix and Panasonic. Neoconix offers its LPM (Low Profile Mobile) family of standard connectors, which offer a mated height of 0.28 mm. The connectors come in 19 configurations with 12 to 84 positions, and use the company’s PCBeam technology that combines high-speed signal and power connections within the same connector. The connectors are suited for fitness trackers, virtual reality glasses, and other portable/wearable electronics.
Panasonic recently expanded its B01 series board-to-flexible printed circuit connectors for high current battery applications in wearable electronics and other small mobile devices. The connectors offer a 0.6- or 0.8-mm mated height and require a 2.40 x 4.45 mm footprint for the socket and 3.76 mm for the header. A removal force rating of 10 N helps maintain a high-reliability connection.
Future Challenges
The continued emergence of small textiles and e-textiles will challenge connector suppliers as the requirement for washability increases, said Langston. He also expects the emergence of new battery technologies to drive a new generation of connector requirements. Companies like imprint Energy are already working on thin, printable battery technologies that would require a new type of low-profile connector.
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