Flexibility of PCB Boards Affect Their Reliability
The flexibility of PCB boards plays a key role in their reliability. The materials and manufacturing processes used must be able to handle the stress of repeated bending, as well as thermal expansion and contraction. They also need to resist moisture, chemicals and mechanical shocks. In order to minimize the risk of failure in these challenging environments, advanced rigid-flex pcbs are engineered with strict reliability requirements. These requirements include rigorous material inspection and verification and strong design for manufacturability.
Rigid-Flex PCBs combine the benefits of both flexible and rigid circuit boards. The combination of flexible and rigid parts helps to reduce assembly time, increase design flexibility, and improve signal integrity. It can also help to eliminate connectors, which significantly reduces the number of points of potential failure. These factors increase the reliability of the PCB and the overall electronic device.
In general, flex circuits are more expensive to manufacture than rigid PCBs because they require additional materials like flexible substrates, adhesives and more layers of copper. The conductive copper on a rigid-flex pcb is subject to thermal expansion and contraction, which can affect the performance of the board. For example, high currents passing through a conductive copper plane cause the PCB to heat up and expand.
Repeated flexing and bending can cause the conductive copper on the flex circuit to fatigue, which can result in electrical defects. To prevent this, the conductive copper on a flex circuit needs to have a low coefficient of expansion and a robust adhesive, or it may fail under these conditions.
How Does the Flexibility of PCB Boards Affect Their Reliability?
Flex circuits also have a limited range of component compatibility because the thin layers of the substrate make it difficult to mount high-density surface-mount components. In addition, the flexible structure may limit the ability to support heavy components that can strain the circuit boards and potentially lead to mechanical failure.
To ensure the quality of a flex circuit, engineers must carefully consider the materials used and the manufacturing process. For example, the number and size of drill holes, and the tightness of the trace and space size will all impact the cost. Stiffeners are another significant factor, as they need to be thick enough to withstand the stress of bending and flexing. To keep costs down, designers can opt for standard FR-4 or polyimide, which are both more affordable than aluminum or stainless steel stiffeners.
A comprehensive electrical test and inspection of the flex circuit is essential to verify its functionality. This testing must encompass all aspects of the flex circuit, including continuity and short circuit detection, impedance testing, and functionality testing of individual features or components. It is also important to consider the location of plated through-holes and the production panel placement, as this can significantly affect the cost and efficiency of the flex circuit.
A flexible PCB can be a valuable option for a wide variety of applications. However, it is essential to understand its limitations and drawbacks so that you can weigh these against your unique project requirements.
