Flexing Fatigue Prevented in Flex Circuits
Flex circuits are made with rigid areas that connect to other components and the flex sections. The flexible sections of the PCB are typically soldered to these rigid sections using a special process. These connections create a rigid-flex board, which is designed to handle high-speed flexing, but may also experience some stretching and twisting.
In these dynamic applications, flex boards are subject to stresses that can cause damage to the copper conductors. When this happens, the copper can fracture and break. Fortunately, this can be prevented by following the PCB design guidelines for flex circuits that are discussed in this article.
One of the most important factors in preventing flexing fatigue in a flex circuit is to avoid tight bend radiuses. These sharp angles increase the stress on a circuit and reduce the longevity of its lifespan. Instead, a more gradual and larger curve should be used when making a bend. This will protect the traces from damage and extend their life.
How is Flexing Fatigue Prevented in Flex Circuits?
It is also important to keep the flex area free of vias and pins that could be damaged during bending. These should be anchored by the mask or coverlay to prevent them from peeling off of the flex layers. Also, plated through-holes should not be placed in or near areas that are expected to bend. If this isn’t possible, the PCB editor should be set to allow via placement only in stationary areas of the flex.
Another way to prevent flexing fatigue is by using a cross-hatched copper pattern for the reference planes on a flex circuit. This will not only improve flexibility, but it will also help to prevent interference between signal traces and the reference plane. This is because the cross-hatched pattern will help to absorb any radiated energy from the signal traces.
The final thing that can be done to prevent flexing fatigue in a flex PCB is by not placing the conductive tracks close to each other. This will reduce the amount of pressure on them when they are bent, which will prolong their life and make them more durable.
In the automotive industry, flex circuits play a crucial role in modern vehicles, where space is often limited, and reliability is paramount. These circuits are used in a variety of applications, including airbag sensors, dashboard displays, and engine control units. Their ability to withstand temperature fluctuations, vibration, and moisture makes them an ideal choice for automotive electronics, where reliability is critical for safety and performance.
While it’s possible to build a flex PCB from almost any stackup, it’s important to consider how many times the circuit will be bent. This will determine the material thickness and how thick it should be, as well as the etch yields needed for the circuit. Also, it’s important to choose the right materials for the flex and rigid-flex sections to ensure they will be able to stand up to repeated flexing and bending. With a little bit of extra effort, it is easy to prevent flexing fatigue in a PCB and provide the reliability necessary for dynamic applications.
