Design a PCB That Can Bend and Flex
Unlike a standard printed circuit board, an electronics board that is designed to bend and flex must follow different rules for design, materials and manufacturing. A flex circuit must be able to withstand a certain number of bend cycles. It must also be able to withstand stresses caused by the bending and flattening of the board during assembly and use. To achieve this, the design needs to be made of a flexible material that is durable enough to withstand these stress levels.
During the design process, engineers must decide whether their flex circuit is static or dynamic in nature. A static flex circuit will only be bent once and then installed, while a dynamic electronics board must be able to flex over and over again. The IPC standards do not offer clear guidelines for the optimum amount of flexibility required, and so, designers must use their own experience to determine how many bend cycles the flex circuit will need to be able to handle.
The maximum angle through which a flex circuit can be bent without damage is 90 degrees. This is possible with a properly designed circuit, but it is not recommended to bend the circuit more than this once. To ensure a safe and reliable design, engineers must minimize the thickness of the flex circuit in the area of the bend zone. This can be achieved by reducing the dielectric base layer thickness and the copper or conductive material layer thickness. Engineers should also be careful not to change conductor widths in the bend region, which could result in weak spots and increased stress.
How to Design a PCB That Can Bend and Flex
For the best flex circuit design, it is important to avoid hard right-angle track work, but when this is unavoidable, it is advisable to route the tracks with arc corner modes. This will reduce the tensile stress that is applied to the copper and help the circuit to resist deformation.
Plated vias are prone to cracking and breaking when they are placed in areas that experience frequent bending. To prevent this, the engineering team must utilize the PCB editor’s design rules to restrict via placement to nonflexing regions. This will protect the integrity of the flex circuit and avoid costly repairs. In addition, they should be sure to use teardrop (pad fillets) shaped vias instead of round ones in order to reduce the pressure that is applied to them when the circuit is bent.
Another important factor in a good flex circuit design is to avoid placing components near the edges of the board, which can cause the copper to break off and damage the traces. During the assembly and soldering processes, this can be extremely expensive. It is best to place components in the center of the board where they will not be subjected to any flexing. Additionally, it is a good idea to use hold-down tabs or anchors to assist with stopping the board from peeling. This will also allow the flex circuit to retain its shape when being bent or curved.
