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Rigid PCB vs. Flexible PCB

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.

Factors That Affect the Cost of Rigid PCBs

There are three main factors that impact the cost of rigid-flex PCB:

  1. Materials: The raw materials used to manufacture rigid-flex PCBs tend to cost more than traditional PCB materials. While these boards use common materials such as copper foil, they also incorporate no flow prepregs, flexible copper-clad laminates and thicker polyimide films.
  2. Assembly: Because there are separate components and complex steps required, the assembly process costs more.
  3. Manufacturing yield: To manufacture rigid-flex boards, specialized equipment and software tools are needed, which impacts the final cost.

How to Reduce the Cost of Rigid PCBs

There are various ways to lower the cost of your rigid-flex PCB, including:

  • Minimize the amount of circuit layers
  • Choose materials carefully
  • Reduce the thickness of the materials
  • Simplify the configuration
  • Tailor the design process

What Are Flex PCBs?

Flex PCBs use a flexible base material for the circuit connection. These circuit boards work well in a variety of industries and environments ranging from consumer electronics to medical systems to automobiles. Regardless of where they are used, they can simplify component assembly, support higher circuit densities and reduce wiring errors.

Factors That Affect the Cost of Flex PCBs

Like the rigid-flex boards, the cost of flex PCB is affected by three main factors:

  1. Size: Most commonly, the cost for a flex PCB is based on the price per square inch. The standard size is 12” x 24” and 18” x 24″. If a larger size is needed, it will likely cost more.
  2. Circuit construction: The fewer circuits in a panel, the lower the cost will be. If your flex PCB’s circuit construction requires additional steps such as folding or adding a stiffener attachment, the price will increase.
  3. Volume: When ordering a low volume quantity of flex PCBs, you may notice a charge to help cover overhead and engineering costs.

How to Reduce the Cost of Flex PCBs

There are various ways you can reduce the cost of your flex PCB, including:

  • Reduce the number of layers
  • Reduce the thickness of layers
  • Minimize the panel space
  • Choose materials such as the laminate and finishes carefully

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.

In addition to the right circuit boards, you also need to choose the right supplier. At Millennium Circuits Limited, we provide rigid PCBs, flex PCBs and Rigid-Flex PCBs for more than 600 customers across multiple industries. Learn more about our PCB capabilities and contact us for a quote today.