difference between flex and rigid-flex PCBs
Rigid and flexible printed circuit boards (PCBs) both connect electronic components in various consumer and non-consumer devices. However, they differ from each other in many ways. While rigid PCBs are built on a solid base layer and cannot bend, flexible circuit boards can be bent or twisted into a variety of shapes to fit the end application. This flexibility allows them to save space and reduce the overall size of a device. Additionally, flex and rigid-flex circuit boards are much more resistant to damage and vibrations than rigid PCBs.
Rigid flex PCBs have a combination of both rigid and flexible sections, with plated through holes (PTH) connecting the two. They are often used in applications that require high reliability and durability, such as aerospace and military equipment, medical devices, automotive electronics and industrial machinery. They are also useful in applications where there are physical constraints and a need to be able to adapt to changes in environment.
flexible pcb are made by laminating a transparent film, such as polyimide or polyimide and FR4, onto copper. The copper is then etched to leave the specific PCB pattern. The final product can be a single or double-sided, or even a multi-layer design. The choice of the film thickness is important as it can influence the cost of the flex PCB. Generally, a thinner film is cheaper than a thicker one.
What is the difference between flex and rigid-flex PCBs?
When designing a flex circuit board, it’s essential to consider the different mechanical and electrical specifications. For instance, selecting an excessively small bend radius can cause sign integrity issues. It’s also a good idea to avoid creating large gaps between traces, as these can become weak points and cause soldering problems. Additionally, it’s a good idea to choose a conductive material that is durable and has good thermal properties.
It’s crucial to work closely with a PCB manufacturer during the design process, as there are some significant differences between rigid and flex PCB fabrication. Flex PCBs are more complex to make than rigid ones, and they require specialized handling, etching and soldering processes. Additionally, they must be designed using a rigid-flex layout system that takes into account the rigid and flex parts of the board.
The cost of a flex circuit board is usually higher than a rigid one. This is because flex manufacturing involves more steps and uses more materials. According to a video from Epec Engineered Technologies on Youtube, there are 8 steps in manufacturing a rigid PCB and 17 in a flex PCB.
Additionally, the flex PCB may have additional special requirements such as adding adhesive tape to specified areas to help the design adhere to surfaces or other materials, or shielding to prevent electromagnetic interference (EMI). These extra steps and the use of more materials can increase the cost of the flex circuit board.