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26 The PCB Magazine • June 2015 laptops, tablets, etc. So, too, are wearable elec- tronics becoming categorized, not so much by function as by proximity to the user. Wearable electronics are designed into many forms for body adaptation such as a wristband, apparel, footwear, jewelry, patches, earwear and eyewear. The proximity of the wearable electronic to the user is often categorized into three areas reflect- ing the level of body contact by the product: close to the body; on the body; and in the body. Figure 2 depicts the wearable electronics body contact level and type of product per category. With any new technology, eventually cer- tain standardizations become clear. The de- velopment of technology building blocks has enabled some manufacturers to develop smart component strategy and accelerate their time to market for certain products. In creating a wearable electronic product, seven technology building blocks are consid- ered: security and computing; sensors and actu- ators; human machine interface; connectivity; smart software; battery and power; and flexible technologies and miniaturization. Figure 3 de- picts the technology building blocks for wear- able electronic products. Flexible Technologies Flexible interconnect technologies and component miniaturization are enabling the wearable electronics market. The vast majority of wearable electronic products have printed circuits or printed electronics. There is a distinct difference between these interconnect technol- ogies. The choice of a printed circuit versus a printed electronics technology in a wearable device is driven by form, fit, function and cost. The design and material combinations thereof can thus provide rigid, flexible and/or stretch- able electronic solutions. Rigid PCBs, flexible printed circuits (FPCs), and rigid-flexible circuits (RFPCs) are consid- ered printed circuit technologies. PCB, FPC and RFPC are primarily fabricated using conven- tional methods of circuit formation of electri- cal interconnect features by etching copper sheet and lamination with dielectric materi- als [6] . High-density interconnects (HDI) and ev- ery-layer interconnect connection (ELIC) PCBs combined with FPCs form a complex RFPC are more recent technologies that have enabled higher functionality demanded of advanced smart connected wearable devices [7] . Figure 4 ENABLING SMART WEARABLE TECHNOLOGY continues Figure2: Proximity categories of wearable technology. (courtesy of Multek Technologies ltd.) FeAtuRe