How thin can rigid flex boards be?
rigid flex boards
Rigid flex boards provide designers with complete design freedom as well as a space and weight saving solution. They can be bent, twisted or formed to minimise size and shape for the product they are being used in, helping to save space and improve the structural integrity of the end product. They are also less susceptible to failure in environments that experience high mechanical stress.
As a result, these types of PCBs have become the go-to choice for many electronic products and are used extensively in areas like aviation, space and the military. They can be used to connect, power and control electronic devices, sensors, actuators and other electronic equipment. To meet the needs of these different environments, there are several factors that determine the standard thickness of a rigid flex board, including the mechanical requirements of the device and manufacturing capabilities.
A Rigid flex boards can be made of several different materials, including FR4, epoxy glass, polyimide, polyamide and other types of composite materials. The material choice depends on the type of environment the PCB is going to be used in, with FR4 being a popular option as it is low cost and has good electrical performance. However, if the board is going to be exposed to high temperatures, it may need to have a higher thermal conductivity to dissipate heat effectively.
How thin can rigid flex boards be?
The copper layer on a rigid flex PCB is generally only 1.4 to 2.8 mils wide. Increasing the copper thickness would increase the cost of the PCB, so it is important to take into account the overall design requirements when determining the target thickness.
Another factor to consider when designing a rigid flex PCB is the amount of bending it will be subjected to. This will help to ensure the circuit board can withstand the required level of mechanical stress without failing or becoming damaged. The copper will stretch if the circuit board is subjected to too much bending, so it is important to design the board with a sufficient bend radius.
It is also important to follow strict flex circuit board design guidelines to prevent a range of common failure modes such as broken copper traces, cracked vias and deformed stiffeners. The first key design rule is to avoid creating stress points. These are places where the copper is expected to experience a significant change in size, such as a sharp transition from wide to narrow traces. These areas are more likely to break than a gradual transition and should be avoided.
Other important flex PCB guidelines include the use of rounded corners and avoiding the use of solid polygons in areas that are expected to be bended, as these will have a lower tear resistance than hatched polygons. Also, it is important to avoid vias being placed too close to the stiffener edge. This reduces the risk of them cracking during bending, which could lead to shorts. Lastly, it is essential to have the right hole-to-copper clearance, which is typically 8 mils.