Most people that know circuit boards wonder about flexible PCB applications. With improvements in electrical systems, we’re looking at an area full of potential.
From the name, the flexible PCBs bend as you apply a force while retaining their functionality and reliability. But you may wonder why they are flexible.
Or what their uses are. We’re highlighting the types of flexible PCBs and some common applications. Read on.
Table of Contents
- Types of Flexible Circuit Boards
- Applications of Flexible PCBs
- Considerations for Selecting a Flexible PCB For a Certain Application
- Shortcomings of Flexible Circuit Boards
- Final Remarks
Types of Flexible Circuit Boards
(Flexible circuit board ribbon cable)
A common thing among flexible circuit boards is that you can fold them without breaking components or electrical traces.
However, some differences distinguish them into several groups. Here, let us look at the types of flexible circuit boards.
Single-Sided Flexible PCBs
The most popular and straightforward flexible printed circuit boards on the market. They have components and traces on one side while the other remains empty. Additionally, they have a single conductor layer atop a stretchable dielectric layer.
Moreover, single-sided circuit boards are the cheapest flex PCBs on the market as they are easier to manufacture.
If you need a simple, flexible PCB for your project, a single-sided flex should be your first choice. They are lightweight and durable, making them common circuit boards in small devices like calculators.
Double-Sided Flex PCBs
From the name, double-sided PCBs have prints on both sides of a dielectric layer. The two sides then connect through plated holes.
As a result, the boards have better circuit density and power-handling capabilities than single-sided flex boards. However, they are costlier to manufacture and assemble.
Multi-Layer Flex Circuit Boards
They are flexible circuit boards made according to IPC Type 3 standards of PCB manufacturing. Moreover, they have three or more flexible layers of conductors that manufacturers separate with insulating films.
On the outside, PCB manufacturers cover the layers with an insulating polyimide layer.
They also employ plated through holes to connect the electrical circuits on each layer. Furthermore, they are ideal for bend-to-fit devices only.
Moreover, they employ high-speed regulated impedance in a surface stripline or microstrip format.
Rigid-Flex Circuit Boards
Rigid-flex PCBs are flexible circuit boards made according to IPC Type 4 standards of PCB manufacturing.
They consist of two or more layers of conductive copper separated by flexible or rigid insulation materials.
They have plated through holes connecting the conducting layers in a multi-layer configuration.
Furthermore, manufacturers selectively add cover film layers to the board’s flexible areas. Consequently, they are ideal for bend-to-fit applications in military devices, among others.
Applications of Flexible PCBs
(A man using a printer in an office)
In Computer Electronics
One area where we use flexible PCBs is computer electronics. The category contributes the most sales of flexible PCBs in the current market. Every device you can think of, be it printers or scanners, has a flexible PCB.
With current technology trends calling for smaller devices, it’s only a matter of time before we witness massive uptake of flex PCBs. Moreover, they are durable and lightweight, making them ideal for portable devices like cameras and calculators.
In Automotive Industry
Weight is an important consideration when designing automotive electrical systems.
Engineers try to make some vehicles as light as possible by reducing the weight of PCBs and wire harnesses. And the best way to do so is to use flexible PCBs instead of the older rigid circuit boards.
Moreover, as vehicles advance and begin to have multiple sensors and electronics, there’s a need for reliable connections. Engineers would have to connect thousands of wires throughout the car without flexible PCBs.
Luckily, the flex PCBs allow for better thermal and vibration performance within the vehicle.
In Medical Devices
(Blood pressure monitors use flex PCBs)
Flexible PCBs have great use in medical devices due to their flexibility and reliability. Wearable devices are developing into a significant aspect of modern-day medical technology.
Moreover, the ability of flexible printed circuit boards to mimic human forms increases the devices’ durability.
Flexible printed circuits can withstand wear and tear in applications, including hearing aids, crucial sensors, and more. Consequently, they improve the performance and efficiency of these systems.
Other applications of flexible PCBs in medical devices include:
- Implantable devices like defibrillators and neurostimulators
- Wearable devices like ECG and blood pressure monitors
- Diagnostic equipment like CT scanners and MRI machines
- Surgical instruments like endoscopes and laparoscopes
- Drug delivery devices like insulin pumps and infusion pumps
Flexible PCBs have many smartphone applications due to their performance and low weight. First, smartphone manufacturers use them in smartphone displays, including AMOLED screens.
The flex boards give the engineers design freedom to curve the screens to suit customer preference. Second, we use flex PCBs in camera modules for compact design.
The design flexibility makes connecting the camera sensor to the phone’s main board easier. Additionally, other applications include use as antennae trace, flexible battery cells, and touch screen sensors.
Considerations for Selecting a Flexible PCB For a Certain Application
(A team of computer engineers discussing a PCB to work with)
Many PCBs around the globe suit certain applications rather than others. But first, you should consider whether you’re using it for a static or dynamic application. Static application or flex-to-fit application is when the board has minimal flexing movement.
Consequently, they only flex for easier installation. On the other hand, the dynamic application of flex PCB is in systems that flex daily. In today’s section, we consider what to consider before selecting a PCB for a certain application.
Material: Your choice of material for a flexible PCB will determine its weight and sometimes the overall performance. Some materials have excellent temperature range and chemical resistance, while others do not.
Circuit layout: Depending on the application, look for a flex PCB with a layout design that minimizes signal interference. Flex circuit boards are delicate, meaning that they have little manufacturing tolerances. Any design mistakes will affect their overall performance.
Environmental conditions: Always consider the environment to install your flexible PCB. By design, the circuit boards have different design parameters that suit certain environments and not others. For example, military vehicles use a flex circuit board with excellent thermal performance for reliability.
Shortcomings of Flexible Circuit Boards
(A flexible printed circuit board from the inside of headphones)
Some shortcomings of flex PCBs include the following:
- A High initial cost of design and manufacturing
- Flexible PCBs are difficult to change and repair
- The boards have size limitations
- They can easily get damaged when you handle them poorly
What’s the future of flexible PCBs
The future of flexible PCBs is bright, and we now witness a growing uptake of circuit boards. First, we expect advancement in material science that will lead to the developing of newer materials with better performance.
Additionally, materials like graphene will offer better conductivity and flexibility than most materials. Such advancements could open up new possibilities for using flexible PCBs in various applications.
Can I replace a rigid PCB with a flexible PCB?
Sometimes, you can replace a rigid PCB with a flexible one. However, it would be best if you considered the board’s design parameters and mechanical constraints.
Other factors include manufacturing constraints and environmental factors. Considering these aspects, you should clearly understand whether to replace one with the other.
PCB manufacturers are adopting flexible circuit boards in all spheres of life. Moreover, with the advancement in material science, we’re looking at better flex boards that may phase out some current systems.
But that doesn’t mean that rigid boards are no longer useful. Finding a balance between the two will improve performance and reliability.
Furthermore, look at a particular application before deciding which circuit board to use.