Custom Flex PCB: The Ultimate Guide


Oakley Mae

Home » Blog » Flexible PCB » Custom Flex PCB: The Ultimate Guide

Modern electrical projects are complex, thus requiring complex circuitry involving custom flex PCB.

A good example is the smartphone that you can hold comfortably in your hand but still process an immense amount of information. 

A custom flexible PCB has small electronic components and conductive metal strips like copper printed on flexible insulated materials.

Surprisingly, you can fold the PCB without damage and use it to integrate components while saving space.

Therefore, understanding these circuit boards is critical for designing and manufacturing reliable devices. 

This article provides important information relating to custom flex PCBs. Let’s get started!

Table of Contents

What’s A Flexible PCB?

Flexible PCB in a smartphone

(Flexible PCB in a smartphone)

As their name suggests, flexible PCBs are circuit boards you can bend or fold to fit into an electronic device. 

Generally, flexible PCBs are defined by distinctly patterned circuitry and components with a malleable base material.

Apart from flexibility, these PCBs are also known for high durability and ease of installation. 

Surprisingly, flexible PCBs find applications in most electronic devices, including wearables, televisions, smartphones, and medical equipment.

Must-Know Design Considerations for Custom Flex PCB

Engineer working on PCB designs

(Engineer working on PCB designs)

Abiding by the following considerations will help you design a reliable and efficient custom flex PCB:


We normally design every flexible board with a calculated bend radius.

This radius depends on the material flexibility and the number of PCB layers.

Surprisingly, the PCB bendability defines the operation score of the circuit board.

Therefore, bendability is a major factor in applications that require high flexibility. 

Bend Radius Features

We have features like mounted components, slots, and cutouts that shouldn’t be found on the bend radius.

Therefore, you must consider the stressed features and bend radius while designing the PCB and allocating features. 


You should choose the right materials to achieve the specific flexibility you want. Generally, custom flexible PCBs use low to moderate-dimensional stability materials.

Therefore, you should always use materials that sustain the PCB shape and size without affecting flexibility.

However, you might be forced to modify slightly to stabilize the material on your PCB. This includes inserting anchors and spurs. 

Trace Routing

Whether experienced or beginners, designers sometimes find it hard to accomplish complex circuitry on the PCB.

Generally, a higher bend radius introduces less stress on the circuit board.

As a requirement, components and vias should go through the low-stress regions for circuit board design safety. And this is where trace routing comes in.

Trace routing prevents electrostatic discharge in the circuit board and, in the process, eliminates possible short circuits. 

Flex Circuit Board Layer Stacking

Flexible PCBs involve stacking together multiple layers. Therefore, you need to implement strategic stacking, where you stack most layers at the center to eliminate cases of layer slippage. 

Delamination Risk

Sometimes, you might experience detachment or delamination of layers in PCB applications and fabrication. Consequently, it leads to circuitry damage and, in worst cases, the entire circuit board fails.

To eliminate delamination, we recommend proper solder paste application practices. Moreover, you can introduce features like anchors for a more reliable circuit board. 

Considerations While Choosing The Best Custom Flexible PCB Supplier

Circuit board manufacturing

(Circuit board manufacturing)

The world is full of custom flexible PCB suppliers and manufacturers. So how do you identify reliable PCB suppliers? Check out the top considerations below: 

Modern Equipment

Reliable custom FPCB suppliers invest in modern equipment and the latest technology to offer customers high-quality flexible PCBs. They aim to increase efficiency and, at the same time, maintain product quality. 

Some of the equipment your potential supplier should have includes imaging equipment, surface finishing tools, board testers, and drilling tools. 

Professional and Qualified Technicians

We all understand the complexity of the flexible circuit board manufacturing process. The process involves many steps before you get the final PCB; not just anyone can do it.

Therefore, there is a need for skilled technicians who will produce high-quality circuit boards that function as needed. 

These same technicians will offer customer support services if you encounter challenges using your circuit board.

If your potential supplier doesn’t have competent technicians, you better find a better alternative. 

Supplier Quality

The quality of the flexible circuit board should be your first consideration. Therefore, choose a PCB supplier depending on the product quality they offer. 

Generally, a quality PCB should have a high-density design, high conductivity, long-term durability, and high-speed communication lines.

If possible, you can do an E-test to inspect the product quality. 

Standards and Certifications

The best flex PCB manufacturers and suppliers always comply with ISO, IPC, and UL guidelines.

However, you must ensure your potential supplier has the required certifications and follows the set standards. For example, pay attention to the UL 94V-0 fire-resistance certification. 

Ability To Deliver Your Required PCB Shape

We like custom flexible PCBs since they can fit many applications.

The supplier you select must be able to provide the PCB in the form you need.

Surprisingly, PCBs are available in different sizes and shapes. For example, flexible medical equipment PCBs differ from those we use in wearables. 

PCB Price

The cost of circuit boards varies with the design standard and quality.

It’s common to find factors like base material and solder mask changing from one PCB to another.

This will automatically affect the circuit board’s final price. 

Therefore, find a good balance between cost and quality without compromising one for the other.

However, the best supplier should provide a quality PCB at an affordable price. And if cost is not an issue for you, don’t hesitate to invest in a high-quality flex PCB. 

Ability To Test The Circuit Board

Circuit board testing helps to guarantee the integrity and functionality of the flex PCB. If you ignore the testing phase, you might buy a non-functional PCB or one that won’t serve you for long.

Therefore, you should only consider suppliers that test their circuit boards before rolling them out. 

This way, you’ll be assured of getting a circuit board that will serve you for many years without failure. 

Advantages of A Customized Flexible PCB

A thin, flexible PCB

(A thin, flexible PCB)

The customized, flexible PCBs offer several benefits you’ll never find in other circuit boards. Check them out below:

  • They save space: Surprisingly, flexible circuit boards have only about 10% of the weight and space of traditional circuit boards. Therefore, they present excellent packaging and installation freedom. Also, their small weight makes them perfect for developing lightweight products like wearables. 
  • They’re flexible: This characteristic gives you the power to reduce the overall mechanical footprint. You can bend them to fit in tighter spaces, thus perfect for developing compact electronics. 
  • Works in high temperatures: Unlike FR-4 circuit boards, flexible circuit boards work well in very high temperatures. Moreover, they’re resistant to gas, acids, and oils. 
  • The thin PCBs partly contribute to the circuit board’s bending abilities. For example, a normal 2-layer flexible circuit board is 4.4-10 mils thick. 
  • Maximum reliability: A custom flex PCB requires fewer interconnects, translating into fewer solder joints and contact crimps. Therefore, it doesn’t have many possible sources of failure, thus improving reliability. 
  • Cost saving: This results from reduced material and packaging demands. Moreover, it’s caused by lower parts replacement costs and fewer assembly errors, thus limited repairs. 
  • Enhanced capabilities: Flexible PCBs work well with almost all components and connectors. Additionally, they function well in extreme conditions. 


Why buy a custom flexible PCB?

First, custom flex PCBs work well under extreme conditions like high temperatures.

Also, they’re highly flexible, thus fitting into tighter spaces and saving space. 

Moreover, these circuit boards need fewer interconnects translating into fewer contact crimps, connectors, and solder joints.

Therefore, they won’t present as many potential sources of failure as traditional PCBs. 

What can you do with a custom flex PCB?

Most importantly, you can bend and fold a custom flex circuit board to fit into almost any application you need. Surprisingly, these circuit boards find application in limitless applications, including the following:

  • Military
  • Consumer electronics
  • Aerospace
  • Transportation
  • Communications
  • Medical equipment
  • Industrial applications


Many modern electrical projects have adopted complex circuitry with custom flexible PCB.

Surprisingly, these PCBs present many benefits, including saving space, high reliability, and enhanced capabilities.

Moreover, they find applications in various uses, including communication, medical, and consumer electronics.