Ultra-Thin LED Flexible PCBs


Oakley Mae

In some of our lighting applications, we see a significant shift towards light-emitting diodes (LEDs) and ultra-thin LED flexible PCBs.

For example, most light bulbs for home and automotive are LED lights.

Surprisingly, they consume less power and don’t generate as much heat as filament lamps. 

Now that the LEDs solve our lighting problems, we must pair them with equally capable circuit boards.

And none can compete with the ultra-thin LED flexible PCB. In today’s piece, we’ll examine why they pair best with our LEDs.

Table of Contents

What Are Ultra-Thin LED Flexible Circuit Boards?

Ultra-thin LED flexible circuit boards are thinner PCBs than most boards and are generally manufactured with LEDs.

Additionally, they are lightweight and have a high tolerance to vibrations. 

However, you must be careful when installing them, as they can tear if you stretch them beyond their capability.

Reasons for Using Ultra-Thin Flexible PCBs for LEDs

An ultra-thin flexible PCB for LED applications

(An ultra-thin flexible PCB for LED applications)

There are many reasons why we use ultra-thin flexible PCBs for LEDs. First, the PCBs are lightweight, making them suitable for LED applications, whereby the weight is a consideration.

For instance, some portable medical devices need to be lightweight, and it would be unwise to use heavier circuit boards. 

Second, some LEDs generate heat that may affect the conductivity of the PCBs.

To counter such, manufacturers prefer ultra-thin LED PCBs as they have polyimide covers instead of solder masks

Third, ultra-thin PCBs can withstand strenuous flexing over a long time.

Such is beneficial, especially if you want to reduce the number of times that you service the circuit board.

Fourth, flex circuits’ low bulk and great flexibility are beneficial when dealing with strong vibrations. 

Types of Ultra-Thin Flexible LED PCBs

Rigid-flex PCB with rigid parts for mounting

(Rigid-flex PCB with rigid parts for mounting)

Manufacturers differentiate ultra-thin PCBs into four main categories as follows: 

Ultra-Thin Flexible PCBs

The ultra-thin flexible PCBs are the most common flexible in most light-emitting diode strips.

The reason is that they have excellent flexibility and unrivaled vibration resistance.

And as LED lights tend to be durable, blending them with flexible PCBs creates a long-lasting lighting system.

Moreover, they have a high density to accommodate many LEDs. 

Rigid-Flex PCBs

Rigid-flex PCBs combine the features of flexible PCBs with those of rigid circuit boards.

In other words, they have sections that are flexible and others that are rigid. 

Generally, the rigid sections aid in hard mounting the boards, whereas the flexible regions allow the PCB to assume three-dimensional configurations.

Furthermore, there are vibration-resistant zones for the most demanding industrial tasks. 

HDI Flexible PCBs

HDI flexible PCBs are resourceful in areas where the other flexible boards may prove insufficient.

They incorporate microvias to offer better layout design and construction options.

Besides, HDI technology offers enhanced dependability, better electrical performance, and access to advanced IC package utilization despite using smaller materials. 

Chip-On-Board (COB) Flexible PCBs

COB flexible PCBs allow manufacturers to mount LED chips directly onto the flexible substrate.

Consequently, they eliminate the need for a separate LED package that relies on the PCB.

If you’ve come across a high-density LED system, chances are that it was a Chip-On-Board (COB) flexible PCB. 

Material for Ultra-Thin Flexible PCBs

An ultra-thin flex PCB with an optical sensor

(An ultra-thin flex PCB with an optical sensor)

Common materials for manufacturing ultra-thin flexible PCBs include: 

Polyimide is a material that manufacturers use to construct layers and coatings that protect PCBs. Furthermore, it has high-temperature resistance and flexibility making it suitable for manufacturing high-heat LED circuit boards. 

Polyester: Polyester is low-cost material manufacturers use in applications where flexibility is important. However, due to its lower temperature range, it finds use in applications that don’t generate a high temperature. For instance, we use it in low-power LED applications. 

Liquid Crystal Polymer: We use the material for high-density interconnects applications.

The material has high-temperature stability and low water absorption rates. 

Adhesives: Adhesives attach bending pieces to ensure they can withstand three-dimensional flexing. 

Advantages of Ultra-Thin Flexible LED PCBs

An engineer testing a LED board voltage

(An engineer testing a LED board voltage)

Ultra-thin flexible PCBs work best in certain environments that may not suit rigid PCBs.

But that’s not to mean that you can’t use them interchangeably.

Device manufacturers prefer ultra-thin flexible PCBs for the following advantages:

Lower material costs

Ultra-thin PCBs use fewer copper conductors and other materials than standard PCBs.

Consequently, they are cheaper to produce in large quantities.

Furthermore, the ability to produce small flexible PCBs offsets the initial manufacturing costs. 


Ultra-thin flexible PCBs are more flexible that other PCBs due to their thinness.

Therefore, you can twist, fold, and bend them to fit into irregularly shaped spaces.

Moreover, you won’t fear damaging the coverlays or copper traces while doing so. 


If you need an LED lighting system in a device where weight is important, use ultra-thin flexible PCBs.

For instance, they are ideal for wearable devices such as LED watches. 

Better Signal Integrity

Ultra-thin LED PCBs follow the contours of the product or installation surface.

As a result, they reduce signal trace lengths leading to less signal loss.

Moreover, ease of installation reduces electromagnetic interference, lowering signal integrity. 


What is the minimum thickness of a flexible PCB?

PCB manufacturers make flexible PCBs to be thinner than rigid circuit boards despite the fact they have adhesive polyimides and stiffeners.

Generally, their minimum thickness may be around 100 microns (0.1mm) for the single-layer designs.

Additionally, they can be as thin as 200 microns (0.2mm) for double-layer boards. 

Nevertheless, some manufacturers push the limits even lower with flexible PCBs with a thickness of 50 microns (0.05 mm) or less.

But remember, the thinner the board is, the more delicate it gets to manufacture and maintain. 

Why are Flex PCBs so expensive?

First, flexible circuit boards go through a very complex fabrication process than rigid ones.

It isn’t easy to produce a very thin circuit that can fold without breaking, but it still offers the best functionality. 

Also, we noted that flexible circuit boards use more expensive materials than rigid circuit boards.

In most cases, you must use expensive thicker polyimide films and flexible-clad laminates.

This forces some manufacturers to add rigid materials to flexible PCB to lower fabrication costs.

Consequently, they form rigid-flex circuit boards which combine the characteristics of rigid and flexible circuit boards. 

Generally, you’ll find flexible circuit boards more expensive to manufacture than rigid or rigid-flexible boards. 

Can I make a custom LED PCB?

Yes! It’s possible to make a custom LED PCB at home.

However, we recommend that you first acquire the right tools and equipment. Moreover, you should understand the design standards and rules.

If you ignore these standards, you might design a circuit board that won’t work well in your electronics. 

Also, it would be best to learn how to use the available PCB design software.

Some of the best software we recommend include Altium and EAGLE.

The good is that the software works almost the same, and understanding one can help you work with the other well.

Final Remarks

Every design engineer understands that flexible PCBs are the future of electronics.

They are designed with excellent features like resistance to vibrations that you’ll never find in rigid options.

Also, you can design these circuit boards to be small and thin, thus fitting in different electronics and saving costs. 

Nowadays, most LEDs feature ultra-thin flexible PCBs.

We can attribute this to them being lightweight and long-lasting.

Always feel free to use an ultra-thin flexible PCB for your project.