Rigid-Flex Printed circuit board Design: Features and Design Guidelines. This information will discuss what rigid-flex Printed circuit boards are, the advantages of making use of them, and the rules for designing with them for an application. In electronics, we sometimes face seemingly new technologies that have roots in the past. Rigid-flex PCB technologies trace back somewhere around Half a century to the need to replace wiring harnesses in spacecraft. The initial commercially available mobile computer (which weighed a little over 25 pounds!) used rigid flex pcb cost technologies. Today, laptop computers, wearable technologies, medical devices, test equipment, and satellites are a few of the applications that count on rigid-flex PCBs.
What Is a Rigid-Flex PCB? With a rigid-flex PCB, flexible circuit substrates and rigid circuit substrates are laminated together. Rigid-flex PCBs cross the boundaries of traditional rigid PCBs as well as the unique properties of flex circuits designed to use high-ductility electrodeposited or rolled annealed copper conductors photo-etched onto a flexible type of insulating film. Flex circuits include stackups created from a flexible polyimide like Kapton or Norton and copper laminated together through heat, acrylic adhesive, and pressure.
As with conventional PCBs, it is possible to mount components on both sides of the rigid board. Because of the integration that takes place between rigid and flex circuits, a rigid-flex design does not use connectors or connecting cables involving the sections. Instead, the flex circuits electrically connect the program together. The absence of connectors and connecting cables accomplishes a number of things:
Enhances the ability in the circuit to deliver signals without loss
Accommodates controlled impedance
Eliminates connection problems including cold joints
Frees space for other components – Every rigid-flex PCB is split into zones that feature different materials and varying layer counts. Rigid zones might have more layers than flexible zones, and materials shift from FR-4 to polyimide in transition zones. Complex designs often transition from rigid to flex and returning to rigid many times. Because these intersections occur, the overlap of rigid-flex materials requires keeping holes out of the transition zone to keep integrity. Furthermore, many rigid-flex designs include stainless steel or aluminum stiffeners which provide additional support for connectors and components.
Different Design Rules Affect Rigid-Flex PCB Design – Different challenges cancel out the versatility and suppleness that enable you to build three-dimensional designs and products. Traditional flex pcb material PCB designs allowed one to mount components, connectors, as well as the chassis for the product to the physically stronger rigid portion of the assembly. Again, when it comes to traditional designs, the flexible circuit only served as an interconnect while decreasing the mass and improving the effectiveness against vibration.
New product designs in conjunction with improved flex circuit technologies have introduced new design rules for rigid-flex PCBs. Your design team presently has the liberty to set components on the flexible circuit area. Combining this freedom having a multilayer approach to rigid-flex design allows you and your team to build more circuitry to the design. However, gaining this freedom adds several challenges in terms of routing and holes.
Flexible circuits always have bend lines affecting routing. Because of the potential for material stress, you cannot place components or vias close to the bend line. And also when components are properly located, bending flex circuits places repeated mechanical stresses on surface-mount pads and thru holes. Your team is able to reduce those stresses by making use of through-hole koqcyp and also by bolstering pad support with a lot more coverlay to anchor the pads. As you design your trace routing, follow practices that reduce stress on your circuits. Use hatched polygons to keep flexibility when carrying an electrical or ground plane on the flex circuit. You should utilize curved traces instead of 90° or 45° angles and utilize teardrop patterns to alter trace widths.
Teardrop patterns as used for trace-to-trace connections. These practices decrease stress points and weak spots. Another best practice distributes stress across traces by staggering the very best and bottom traces for prototype pcb assembly. Offsetting the traces prevents the traces from laying over each other within the same direction and strengthens the PCB. You must also route traces perpendicular towards the bend line to minimize stress. When moving from rigid to flex and returning to rigid, the amount of layers from one medium towards the other may differ. You can use trace routing to incorporate stiffness towards the flex circuit by offsetting the routing for adjacent layers.1,2,5,6.