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56 FLEX007 MAGAZINE I JULY 2018 electronics to fit into a certain form. This is pretty common in handheld medical devices, robotics, unmanned vehicles, "pigs" that are designed to inspect pipelines for weak points, and wearable electronics. Figure 1 is one exam- ple of a motherboard, with plenty of room for components, but the electronics needed to fit within a specific form factor. One of the most often overlooked aspects of rigid-flex is that it often can cost a lot less than traditional packaging methods. Whenever you are considering a design with four or more rigid boards, it would be wise to at least con- sider rigid-flex packaging. It offers all of the advantages listed earlier for extreme high-reli- ability electronic packaging, and rigid-flex can also save money if you consider the total cost of packaging. When you have four or more hard boards connected with flex cables and connectors, or wire harnesses, or standoff connectors, the cost of the other packaging components begins to add up. At a certain point a rigid-flex design with the same capabilities will reach a tipping point where it is cheaper to build with rigid-flex than to build the fully assembled equivalent using conventional packaging. It also is much easier and faster to assemble. Rigid-flex boards are often provided in a rigid array that holds the board stable during assembly, which is then removed after assembly. It is very fast, very efficient, and doesn't require subsequent hand assembly. We see this frequently in cameras, robotic applications, insulin pumps, and other electronics where the designer needs to connect more than just a few rigid boards together. Some other advantages to using rigid-flex that are often forgotten are space and weight savings. Rigid-flex boards can be made very thin, often under .020", providing you with high-density connectivity at the lowest possi- ble weight. This makes it ideal for drones, avi- onics, and space flight applications. There is also an electrical advantage to using rigid-flex: As clock speeds get faster and faster, rigid-flex, with its integrated interconnect between rigid layers and flex, reduces noise loss (attenua- tion) by eliminating connectors, where much of the loss can occur. Designers have found rigid-flex packaging to be the right solution for ruggedized laptop computers, servers that require hot swappable daughter cards without shutting down, auto- motive LED electronics, and all manner of ruggedized industrial applications such as bar code scanners. Rigid-flex designs give the electronics design engineer a unique method of packaging, which is ideal in those applications where hardboards, flex circuits and their interconnections are not enough, and a greater reliability is required. FLEX007 Bob Burns is national sales and marketing manager for Printed Circuits. Figure 2: Rigid-flex is ideal for applications with four or more rigid boards and usually can reduce the cost of these designs.