prevent delamination in rigid flex
Rigid flex is often used in mobile phones, tablets and other handheld devices because of its bending capabilities. However, like any other PCB, it can suffer from delamination, which occurs when layers separate or detach from the rest of the circuit board. This can be a major issue when it comes to the safety of these electronic products. The good news is that this problem is avoidable with proper design and manufacturing practices.
Delamination in rigid flex is usually caused by mismatched thermal expansion between different layers or insufficient material compatibility. The best way to prevent these issues is to follow rigid-flex PCB design guidelines and manufacturing techniques that minimize stress, and ensure that the materials have similar CTEs.
Another important factor is to use the correct pad sizes for a given bending radius. This is crucial because pads are where the stresses of flexing and bending are concentrated. Pads should be sized so that the spacing between them does not exceed twice the bend radius. This will prevent the copper from being pulled up by the bending force, which can cause a failure in the board.
How do you prevent delamination in rigid flex?
A third critical factor is to ensure that all rigid areas are the same thickness. This is because if the rigid areas are made of a different thickness than the flexible sections, it can result in a z-axis difference in expansion that could cause delamination or intermittent faults post-soldering.
Finally, it is crucial to ensure that the flex circuit has enough structural support through the utilization of stiffeners. These are usually created using additional polyimide film with adhesive or an adhesive-less process. These stiffeners are then printed with a solder mask and cured via UV exposure. It is also a good idea to utilize a teardrop configuration when changing the width of traces that link to pads and vias in order to help prevent potential stress concentrations at these points.
To conclude, there are many things that can be done to prevent delamination in rigid flex. A few examples of these preventative measures include designing the PCB to minimize stress, choosing compatible materials with low CTEs, maintaining strict temperature and pressure control during manufacturing, creating a controlled environment, and following proper storage and handling techniques. When all of these factors are combined, they can lead to high-quality rigid-flex PCBs that can withstand sudden shocks and vibrations as well as hundreds of thousands of bending cycles without failing.
While it may be tempting to choose cheaper alternatives to rigid-flex PCBs, doing so will only cost you more in the long run. Cheaper, lower-quality alternatives will likely cut corners during design, fabrication and assembly, leading to thermal issues, electrical performance issues and a shorter lifespan for the final product. This is why it is always better to invest in quality rigid-flex PCBs from the start, which will save you significant unplanned costs and headaches in the future.
