Rigid Flex Manufactured
Rigid flex is a type of printed circuit board that incorporates both rigid sections and flexible segments, creating a single- or double-sided board that can be curved or bent into the desired shape for assembly and use. A variety of devices, including mobile phones and tablets, utilize rigid flex PCBs for their flexible connections. They are also used in medical, military and aerospace equipment such as cameras and missile guidance systems, and in automotive components like dashboard displays, sensors and driver assistance systems.
A key advantage of rigid flex is the ability to eliminate the need for exposed interconnections by routing critical signals on inner flex layers surrounded by ground planes, which reduces interference and allows signals to travel further, improving reliability. The encapsulated construction of rigid flex circuits also offers improved resistance to environmental threats such as moisture and dust.
Despite the benefits of using rigid flex PCBs, they do require special fabrication techniques to ensure their quality and durability. This includes the selection of the right materials for both rigid and flex sections, as well as understanding their unique mechanical properties and testing their performance. In addition, there are certain design factors that can significantly influence a rigid flex’s manufacturing costs.
The layered structure of rigid flex boards requires special attention to alignment and registration. This is especially important for the flex section, which must be able to bend and withstand constant stress without losing connection and signal integrity. To achieve this, manufacturers must make sure the flex and rigid sections are properly aligned before lamination.
How Is Rigid Flex Manufactured?
To create the flex layer, a flexible polyimide or liquid crystal polymer (LCP) film is laminated to a copper foil. This process is known as cladding. The fabricator may use adhesive for the cladding or utilize adhesiveless methods such as sputtering to deposit copper directly onto the surface of the film. The clad flex layer is then imaged and chemically etched to create the desired circuit patterns. Once the flex and rigid sections are imaged and etched, they are laminated together under controlled temperatures and pressure conditions.
For the final step in fabricating a rigid flex, holes to pads and vias are usually mechanically drilled. The flex and rigid sections are then drilled with precision drilling systems that can accommodate different hole sizes. Depending on the design, laser drilling can be employed as well. This technique uses Excimer lasers for ultra-small holes and CO2 lasers for medium and large holes.
After the mechanical drill steps, a cover lay is applied to protect the rigid flex from harsh environments and chemicals. Manufacturers often use a cyanoacrylate adhesive for this step. Once the cover lay is applied, the production panel can be cut into individual flex boards by either hydraulic punching for high-volume production or by using a specialized blanking knife for prototypes and small-scale production runs. Choosing the right method can save time and money in this final step of manufacturing.