Both rigid and flexible printed circuit boards (PCBs) are used to connect electronic components in a variety of consumer and non-consumer devices. As the name implies, rigid PCBs are circuit boards built on a rigid base layer that cannot be bent, while flexible PCBs (also known as flex circuits) are built on a flexible base that can be bent, twisted and folded.
Although both traditional PCBs and flexible PCBs have the same basic purpose, it is important to note that there are many differences between them. Flexible circuits are more than just bent PCBs; they are manufactured differently from rigid PCBs and have various performance advantages and disadvantages. Learn more about rigid PCBs vs. flexible PCBs below.
What is the difference between rigid PCBs and flexible circuits?
Rigid PCBs, often referred to simply as PCBs, are what most people think of when they imagine circuit boards. These boards use conductive tracks and other components arranged on a non-conductive substrate to connect electrical components. On rigid circuit boards, the non-conductive substrate usually contains glass that enhances the board and gives it strength and stiffness. Rigid circuit boards provide good support for components and offer good thermal resistance.
Although flexible PCBs also have conductive traces on a non-conductive substrate, this type of board uses a flexible base material, such as polyimide. The flexible base allows flexible circuits to withstand vibration, dissipate heat and fold into various shapes. Due to their structural advantages, flexible circuits are increasingly used in compact and innovative electronics.
In addition to the material and rigidity of the base layer, significant differences between PCBs and flexible circuits include
l Conductive materials: Because flexible circuits must be bent, manufacturers may use softer rolled and annealed copper instead of conductive copper.
l Manufacturing process: Instead of using solder resist film, flexible PCB manufacturers use a process called overlay or cover layer to protect the exposed circuitry of flexible PCBs.
l Typical cost: The cost of flexible circuits is usually higher than that of rigid circuit boards. However, because flexible PCBs can be mounted in compact spaces, engineers can reduce the size of their products, resulting in indirect cost savings.
How to choose between rigid and flexible PCBs
Rigid and flexible circuit boards can be used for many different products, although some applications may benefit more from one type of board. For example, rigid PCBs make sense in larger products (such as TVs and desktop computers), while more compact products (such as smartphones and wearable technology) require flexible circuits.
When choosing between rigid and flexible PCBs, consider the needs of your application, the industry’s preferred board type, and the potential profitability of using one or the other type of effect.