Used in Rigid Flex PCBs
A rigid flex PCB is a multilayer printed circuit board that includes both rigid and flexible sections. These boards use a sandwich-like construction, with multiple double-sided copper layers separated by bonding sheets called prepreg. These PCBs are commonly found in devices such as computers, tablets, mobile phones and GPS trackers.
Rigid flex offers the best of both worlds – the strength and durability of rigid PCBs with the added flexibility of a bending section. This makes them ideal for a wide variety of applications, from medical imaging equipment and handheld monitors to military missile guidance systems, automotive radar and aircraft flight control systems.
The conductive copper used in rigid flex can be either electro-deposited or rolled. In the latter case, manufacturers will often treat the copper conductor with a layer of polyimide, which acts as an insulator. This will also help prevent the copper from oxidizing, and it will enhance the adhesion between the copper and the base flex material. This layer is known as a coverlay.
In addition to the coverlay layer, rigid flex PCBs typically use an epoxy-based material called a solder mask that covers the copper, as well as other elements of the assembly. The surface finish of the copper traces will depend on the application and can vary from basic etching to the use of electron beam lithography.
Another common component of a rigid flex circuit board is a thermal management layer. This helps disperse heat generated by the electrical current flowing through the conductive copper, which can otherwise cause thermal stresses that may lead to premature failure in the finished device. This is especially important in rigid flex circuits that have a significant bending radius or are subject to repetitive flexing.
Materials Used in Rigid Flex PCBs
Finally, the rigid flex circuit board will include plated through holes (PTH) and mounting components to connect the flexible and rigid sections of the assembly. These are essential to ensuring that the connections between the two types of metal are stable, and they also play an important role in maintaining the structural integrity of the rigid-flex PCB as it is assembled and deployed.
Rigid flex circuit boards are built using high-quality materials to ensure their reliability and longevity. Cheaper alternatives may seem appealing, but cutting corners in the design, manufacturing and testing of these circuits can result in poor quality and performance that could compromise the safety and reliability of your product. In the long run, you’ll save time and money by investing in a rigid-flex PCB that is designed and constructed to last.
Rigid-flex PCBs (Printed Circuit Boards) combine the best of both rigid and flexible circuits, offering a unique blend of benefits for various advanced applications. The materials used in rigid-flex PCBs are critical to their performance, reliability, and adaptability in complex electronic devices. Here is an overview of the primary materials used in the construction of rigid-flex PCBs:
The flexible sections utilize flexible polyimide films, which are known for their excellent flexibility, thermal stability, and electrical insulation properties. Polyimide is preferred due to its high dielectric strength, low thermal expansion, and ability to withstand high-temperature processing steps, such as soldering and lamination.
