Considerations for Flexible PCBs
During the design phase of a flexible PCB, it’s essential to consider all aspects of the board and how it will fit into the device it will be embedded in. This includes the overall dimensions, materials and components. It’s also important to account for the amount of flex that the board will undergo in its lifetime, as well as the amount of strain it may experience during assembly and use. A flexible PCB that can withstand multiple bending cycles and a high degree of stress will have a longer lifespan than a more rigid version.
The first step in designing a flexible circuit is to determine the number of layers required for the circuit. Ideally, the number of layers should be as low as possible for cost reasons. A flex PCB with more than two layers is usually more expensive to fabricate, and this will increase the overall thickness of the board. The layer count will influence how many plated through holes can be placed on the board. Choosing an appropriate size for the copper plating via holes is essential to maintain good connectivity throughout the circuit.
Another key consideration is the choice of substrate material. This should be based on the requirements of the specific application, such as maximum bending radius, temperature range and chemical resistance. The fabrication process used for the board will also affect its properties, including flexibility and strength. It’s also important to consult with your flexible pcb board fabrication partners early in the design process to discuss which material is best for your specific application and fabrication method.
Design Considerations for Flexible PCBs
To avoid snags and catches in the manufacturing process, it’s a good idea to incorporate a “keep-out” area around all areas that will be cut or routed, such as traces, pads, vias and drill holes. This area will be clearly labeled and will serve as a safety margin. This will help prevent accidental cuts and routes that can cause a loss of functionality or even circuit failure.
It’s also a good idea to stagger the thickness of the copper traces in the circuit to minimize stress on them. This will allow the traces to better resist the stress that can be caused by continuous bending and repeated flexing.
Lastly, it’s crucial to leave adequate space for heat dissipation in the flex circuit. This will ensure that the traces don’t become too hot, which can damage them and reduce their longevity. It’s also a good idea to place thermal reliefs anywhere a through-hole component connects to a power or ground plane.
One of the most common mistakes in flex circuit designs is assuming that all substrate materials are the same. This can lead to unrealistic expectations and a lot of wasted time and money. It’s important to consult with your flex PCB fabricator early in the design process and test prototypes of the flex circuit on different materials. This will help you understand how they work in different applications and will give you an advantage when selecting the right material for your application.