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68 DESIGN007 MAGAZINE I APRIL 2023 watches, tablets, cameras, printers, and lap- tops. ey are a fundamental requirement for implanted miniature medical devices such as pacemakers, cochlear implants, and implanted defibrillators. Complex multi-PCB assemblies interconnected with wires or cabling are oen redesigned with rigid-flex PCBs to improve reliability and reduce weight and space. is is the catalyst for many military and aero- space products being designed with rigid-flex. One example is a single-use smart bullet that can change its trajectory if its intended target moves. e introduction of small-outline and sur- face mounted semiconductors ushered in a revolution of miniature repackaging. ink Sony Walkman vs. a typical boom box. For years, flexible PCBs were relegated exclusively to replacement of multi-wire cables. Who would not recall the presence of a flexible flat cable connected to the head of a dot matrix or impact printer. e head would bob back and forth across the paper while the cable dynami- cally flexed and provided a more reliable inter- connect between printer head and mother- board. e introduction of rigid-flex was not quite the same level of game-changer as surface mounted packages due to its somewhat limited application and cost differential. We shouldn't expect a new collection of desktop PCs to be designed with rigid-flex motherboards as a means to reduce cost. However, miniatur- ized and reliable technology such as pill cam- eras, foldable cellphones or implanted medi- cal devices would not exist without rigid-flex technology. We'll pick this up this discussion with Part 2 in the next issue of Design007 Magazine. DESIGN007 Mark Gallant is a senior product marketing man- ager for Downstream Technologies. stackup commonly varies greatly across the entire PCB. ere may be areas of rigid-flex, flex only, various combinations of rigid and flex layer count, and so on. ere is also rigidized flex where blank FR-4 or other rigid materials are selectively bonded to flexible substrates to provide stiffness. e rigid stiffener material rarely has conductors present. Rigid vs. Flex and Rigid-flex Rigid PCBs are a foundational technology in today's electronic products. Rigid PCBs offer mechanical integrity, electrical conduc- tivity and reliability, but are limited by their two-dimensional profile. eir flatness limits designers to two dimensions which severely limits design flexibility, especially as electronic devices decrease in size. Flexible PCBs are bent to take advantage of a three-dimensional space, while also accommodating components. Flex- ible PCBs enable maximal utilization of space to package electronics but at a premium cost compared to conventional PCBs. Rigid and flexible PCBs are present in many electronic products. However, some applica- tions benefit more from one type of circuit board. Rigid PCBs make sense for products such as televisions, desktop PCs, Blu-ray play- ers, and other larger electronic products. Flex- ible PCBs are present in smartphones, smart Rigid PCBs offer mechanical integrity, electrical conductivity and reliability, but are limited by their two-dimensional profile.