Rigid-Flex Printed circuit board Design: Advantages and Design Best Practices. This short article will discuss what rigid-flex PCBs are, the advantages of using them, and the rules for designing with them for an application. In electronics, we sometimes encounter seemingly new technologies that have roots in the past. Rigid-flex Printed circuit board technologies trace back somewhere around Half a century to the need to replace wiring harnesses in spacecraft. The first commercially available mobile computer (which weighed a little over 25 pounds!) used rigid flex pcb manufacturers technologies. Today, notebooks, wearable technologies, medical devices, test equipment, and satellites are a few of the applications that count on rigid-flex PCBs.
What exactly is a Rigid-Flex PCB? Using a rigid-flex PCB, flexible circuit substrates and rigid circuit substrates are laminated together. Rigid-flex PCBs cross the boundaries of traditional rigid PCBs and the unique properties of flex circuits designed to use high-ductility electrodeposited or rolled annealed copper conductors photo-etched onto a flexible insulating film. Flex circuits include stackups made from a flexible polyimide like Kapton or Norton and copper laminated together through heat, acrylic adhesive, and pressure.
As with conventional PCBs, you are able to mount components on sides of the rigid board. Due to the integration that takes place between rigid and flex circuits, a rigid-flex design will not use connectors or connecting cables involving the sections. Instead, the flex circuits electrically connect the system together. The lack of connectors and connecting cables accomplishes numerous things:
Enhances the ability of the circuit to send out signals without loss
Accommodates controlled impedance
Eliminates connection problems like cold joints
Frees space for other components – Every rigid-flex PCB is split into zones which include different materials and varying layer counts. Rigid zones may 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 to rigid several times. Because these intersections occur, the overlap of rigid-flex materials requires keeping holes out of the transition zone to keep up integrity. Furthermore, many rigid-flex designs include stainless 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 which allow you to build three-dimensional designs and products. Traditional flex pcb china PCB designs allowed one to mount components, connectors, as well as the chassis to your product for the physically stronger rigid portion of the assembly. Again, with regards to traditional designs, the flexible circuit only served being an interconnect while decreasing the mass and boosting the potential to deal with vibration.
New product designs coupled with improved flex circuit technologies have introduced new design rules for rigid-flex PCBs. Your design team has the freedom to set components on the flexible circuit area. Combining this freedom having a multilayer method of rigid-flex design allows you and the team to construct more circuitry in to the design. However, gaining this freedom adds several challenges when it comes to routing and holes.
Flexible circuits always have bend lines which affect routing. Because of the prospect of material stress, you cannot place components or vias near the bend line. As well as when components are properly located, bending flex circuits places repeated mechanical stresses on surface-mount pads and thru holes. Your team can reduce those stresses by utilizing through-hole koqcyp and by bolstering pad support with additional coverlay to anchor the pads. As you design your trace routing, follow practices that reduce stress on your circuits. Use hatched polygons to keep up flexibility when carrying an electric power or ground plane on the flex circuit. You should utilize curved traces instead of 90° or 45° angles and utilize teardrop patterns to modify 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 top and bottom traces for pcb assembly meaning. Offsetting the traces prevents the traces from laying over the other person inside the same direction and strengthens the PCB. You need to route traces perpendicular for the bend line to reduce stress. When moving from rigid to flex and back to rigid, the amount of layers in one medium to the other may differ. You may use trace routing to add stiffness towards the flex circuit by offsetting the routing for adjacent layers.1,2,5,6.