Rigid Flex PCBs

Rigid flex circuit boards offer a wide range of benefits. Besides being highly customizable for a wide variety of applications, they also help manufacturers reduce costs and increase efficiencies in the production process. They also provide better thermal dissipation which can prevent overheating, thereby increasing the lifespan of electronic components. Rigid flex boards have a variety of uses, from consumer electronics to medical devices and aerospace equipment. Some of these devices, such as mobile phones and tablets, need rigid flex PCBs for their thin design.

Rigid-flex circuit boards have the ability to bend in various axes without damaging copper traces or other components. This capability is crucial for many commercial and industrial applications, such as vehicle infotainment systems and wearable electronics. They also allow manufacturers to produce smaller and more powerful devices with minimal space requirements. These benefits have fueled a significant rise in the demand for these advanced circuit boards.

However, creating a rigid flex board that can sustain repeated bending requires careful consideration of several design factors. For example, the flex board must have an adequate bend radius to avoid stress on the conductors. To achieve this, the flex circuit board’s design should incorporate a rigid section and a flexible section with a large enough gap to ensure that they do not intersect. The rigid sections of a flex circuit board can be strengthened by using stiffeners made of FR-4 fiberglass and pressure-sensitive adhesives.

How Thin Can Rigid Flex PCBs Be?

Another important factor is trace routing. It is important to route traces perpendicular to the bend line to eliminate stresses that can lead to breakage. It is also essential to design the traces with a minimum width of 0.3mm. Moreover, it is critical to consider the traces’ impedance at each bend point, as they will be subjected to different levels of stress depending on their location (flexible vs. rigid components).

For one- and two-layer flex circuits, the bend radius should be 6 times the thickness of the flexible section. For flex circuits with three layers or more, the minimum bend radius should be 12 times the thickness of the flexible section. The plated through-holes or vias on a flex circuit should also have adequate thicknesses to prevent stress cracking.

The most common reliability problems with flex and flex-rigid boards involve broken copper traces or cracked vias. The reason for this is that the traces are usually too thin and do not have sufficient adhesion to the polyimide coverlay. This can lead to failure when the flex or rigid board is mechanically stressed. For this reason, it is essential to choose a high-quality fabricator that follows the IPC 2223 Sectional Design Standard for Rigid Flex PCBs.

Another way to improve the durability of a flex or rigid-flex board is by adding adhesive tape to certain areas. This can be useful for mounting the PCB to a surface, and it can also protect it from electromagnetic interference. It is also recommended to perform a thorough electrical test after production to make sure nothing went wrong during manufacturing. This will also help you save money in the long run by avoiding expensive repairs and replacements.