Bending Radius in PCB Design and Assembly Design
During the design phase of a flex circuit, there are several factors that influence its flexibility. For example, the choice of material can impact its bendability, as well as component placement and layout. But one of the most important considerations is the bending radius, which should be identified and defined early in the process. This ensures that the flex circuit is capable of a given amount of bending without damaging its copper layers. The minimum bending radius is defined by IPC-2223 and can be calculated based on the number of layers in the PCB.
Flexible printed circuit boards (PCBs) offer a variety of advantages over traditional rigid PCBs, including the ability to fit in smaller enclosures and reduce manual routing time. They can also be used in a wider range of applications. However, excessive bending can lead to mechanical stress or damage the copper traces and components. This can compromise the integrity of signals and overall performance. Fortunately, by adhering to manufacturer guidelines, using mechanical design software, and performing a bend test, designers can minimize the risk of failure in the field.
A common mistake is focusing on the thickness of the materials and ignoring the bend radius. While thinner materials are more flexible, they’re also less durable and are more likely to experience mechanical stress due to repeated bending cycles. Therefore, a good rule of thumb is to use a thickness that’s twice as thick as the minimum bending radius.
The Role of Bending Radius in PCB Design and Assembly Design
The bending radius can be determined by dividing the total board thickness in half and then calculating the distance between the center of the copper layer and the edge of the board. For a single-layer construction, this is usually around 2X, but it can be as high as 6X for two-layer flex PCBs. For dynamic designs that undergo repeated bending, it’s best to keep the copper layer as close to the neutral bend axis as possible for maximum durability.
There are many factors that can affect the bending radius of a flex circuit, and each must be considered in its own unique context. The type of flex PCB, the number of layers, and the copper weight are some of the most important variables. The bending radius should be larger than the shortest trace length, and it’s preferable to have a smooth, curved surface rather than sharp corners that can cause strain.
In addition, the minimum bending radius should be large enough to accommodate the desired application height. This is especially important for dynamic flex circuits, which may be subject to hundreds of bending cycles over the course of their lifetime. To achieve this, it’s recommended to use a double-sided flex pcb design & assembly and to stagger the conductors on the different layers for greater bending efficiency. Additionally, it’s a good idea to avoid using plated through-holes in the bending area and to limit the number of holes in the conductive areas. This can help to improve the bending capacity of the circuit by up to 50%.
