Both rigid and flexible printed circuit boards (PCBs) serve to connect electronic components in various consumer and non-consumer devices. As the names suggest, a rigid PCB is a circuit board built on a rigid base layer that cannot bend, while a flexible PCB, also called a flex circuit, is built on a flexible base capable of bending, twisting and folding.
Though traditional and flexible PCBs both fulfill the same basic purpose, it’s important to note that they have many differences. Flexible circuits are more than just PCBs that bend — they’re manufactured differently from rigid PCBs and offer various performance benefits and drawbacks. Learn more about the properties of rigid PCBs versus flexible PCBs below.
HOW ARE RIGID PCBS AND FLEX CIRCUITS DIFFERENT?
A rigid PCB, usually known simply as a PCB, is what most people think of when they imagine a circuit board. These boards connect electrical components using conductive tracks and other elements, which are arranged on a non-conductive substrate. In a rigid circuit board, the non-conductive substrate usually contains glass, which reinforces the board and gives it strength and rigidity. A rigid circuit board provides great support for components, as well as decent thermal resistance.
Though a flexible PCB also features conductive tracks on a non-conductive substrate, this type of circuit board uses a flexible base material like polyimide. The flexible base allows flexible circuits to withstand vibration, dissipate heat and fold up into various shapes. Because of their structural give, flex circuits are increasingly used in compact and innovative electronics.
Besides base layer material and rigidity, notable differences between PCBs and flex circuits include:
- Conductive material: Because flex circuits have to bend, manufacturers may use more flexible rolled annealed copper instead of electro-deposited copper as a conductive material.
- Manufacturing process: Instead of using a solder mask, flexible PCB manufacturers use a process called overlay or coverlay to protect a flexible PCB’s exposed circuitry.
- Typical cost: Flex circuits typically cost more than rigid circuit boards. However, because of their ability to fit in compact spaces, flex circuits allow engineers to shrink the size of their products, leading to indirect savings.
HOW TO CHOOSE BETWEEN A RIGID AND FLEXIBLE PCB
Rigid and flexible circuit boards find use in many different products, though some applications may benefit more from one type of circuit board. For example, rigid PCBs make sense in larger products, such as televisions and desktop computers, while flexible circuits are required for more compact products, such as smartphones and wearable technology.
When choosing between a rigid PCB and a flexible PCB, consider your application’s demands, your industry’s preferred circuit board type and the effect using one type or the other could have on profits.