The term ‘PCB’ breeds confusion because most people think of a rigid printed circuit board. However, PCBs can refer to a rigid PCB or a flexible PCB. The flex circuit is another name of the flexible printed circuit board. They have many other names, such as flex boards, flexible printed circuit boards, flexible circuit boards, and the like. Recently, engineers are calling them as flexible electronics. Flex circuits are gaining a lot of popularity because of their properties. It is possible to bend, twist, fold, or shape them into limitless configurations. In the end, both rigid and flex PCBs serve the same purpose. They connect several electrical and mechanical components.

The use

Now you have to understand when to use a rigid PCB and when to stick to a flexible PCB. Of course, the rigid ones cost less than flex circuits. Then again, the cost of ownership and the application can determine how much you have to spend. There are instances where the use of flex circuits can reduce the costs you incur. If you wish to understand the total cost of ownership, then you must acknowledge a few facts. Flex circuits eliminate the need for several components like connectors, wire harnesses, and other circuit boards. If you speak to flexible circuit board manufacturers, then they will say the same thing.

Similarities and differences

The flexible circuit board manufacturers follow specific design-related rules while producing them. They ascertain the minimum sizes of holes, trace widths, minimum space, minimum distances to board edges, and more. They also consider the use of copper and overall design thicknesses. Apart from that, manufacturers use specific processes that they share between rigid and flex PCBs. These process steps include drilling and plating of holes, vias, development, photo imaging, and the etching of copper traces. They also have to consider pads, plates, outlines, and heating of the circuit boards for moisture removal. It is the point in the manufacturing process where the rigid PCBs go to the soldering station. On the other hand, flex PCBs make their way to the coverlay station.

Overlaying of flex circuits

Overlay or coverlay of flex circuits is a lamination process. With it, the manufacturers encapsulate and protect the external circuitry of a flex circuit. The coverlay film of a flex circuit is quite similar to a rigid PCB’s solder mask. However, there is only one significant difference. The coverlay film of a flex circuit is flexible, but a solder mask isn’t. In most cases, the coverlay film is a polyimide film coated with a thermoset adhesive. The thickness of the film ranges between 0.0005 inches and 0.005 inches. The typical thickness range generally remains between 0.001 and 0.002 inches. Manufacturers laminate polyimide and adhesive using heat and pressure.

To conclude

Indeed, both rigid and flexible circuits serve the same purpose. They connect various electrical and mechanical components. Both these components have their unique objectives in different gadgets. Some of the rules followed during the production of rigid and flex PCBs are the same. In spite of everything, flexible PCBs require additional manufacturing process steps. You may think that flex circuits are costly. However, you can’t decide that until you consider the total cost of ownership and the implementations.

Resource : https://www.playbuzz.com/capeltechnology10/the-difference-between-flexible-pcbs-and-rigid-pcbs