Flexible PCBs Handle Aging and Degradation
As the demand for flexible PCBs grows so too does the need to develop solutions that ensure a long term life for these complex circuits. The challenge lies in understanding the different factors that contribute to the longevity of flex pcbs and identifying methods to identify the failure points when they do fail.
To achieve a longer lifetime it is important to design a flex circuit with thicker copper traces which are more resilient to bending than thinner ones. The other key factor is to avoid stress points which are areas where the wide and narrow traces transition in a sharp way. This is a common weakness in many PCB designs, but it can be easily avoided by using fillets or by making the change in width gradual rather than abrupt.
Another factor that contributes to the longevity of a flex pcbs is the choice of materials for both rigid and flex portions of the board. The thermal expansion of different materials can lead to problems if they are not matched properly, so it is important to use compatible materials for both. This will minimize the impact of varying expansion rates and will help keep the traces on both sections of the board aligned with each other.
How Flexible PCBs Handle Aging and Degradation
For example, if a flex PCB is being used in a device that will be twisted repeatedly it is best to use a higher-grade FR4 thickness for the rigid portion of the board and a softer-gold coating on the conductive layers in the flex section. This will allow the flex section to stretch and bend without experiencing a degradation in performance.
In addition to selecting the right materials for the rigid and flex portions of the circuit it is also important to route the traces perpendicular to the bend line. This will eliminate the stress that can result in cracking of traces when a flex PCB is bent. This can be done by routing the traces through vias or plated through holes.
It is also important to use a small pitch between the traces and to have no overlapping of the trace lines. This reduces the likelihood of a short between two adjacent traces, which can cause a loss of electrical connectivity.
The aging and degradation of a flex PCB can be influenced by the way it is handled in a product, so it is important to have a system for inspecting and analyzing the results. Having a system like this will be crucial for future development of reliable flexible flex circuits that can handle the rigors of consumer products and medical devices. With the advanced CAD features and automated drawing tools found in Altium Designer, designers can create a robust, high-performance flex pcb that will last a long time. Start your free trial of Altium Designer today!