Custom Ultra Thin LED Flex PCB: The Ultimate Guide


Oakley Mae

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Lately, we have seen an increase in custom ultra-thin LED flex PCB development.

Generally, these circuit boards involve adding light-emitting diodes on ultra-thin PCBs.

They find everyday use in applications and devices that require high flexibility and be lightweight. 

Some of the common applications include wearable lighting products like riding safety lamps.

However, few understand the benefits, design, and other critical information about custom ultra-thin LED flex PCBs. 

If you fall under the above category, this article is here to give you all the insights. Let’s get started!

Table of Contents

What’s A Custom Ultra Thin LED Flex PCB

As the name suggests, these are ultra-thin flexible circuit boards having light-emitting diodes.

Therefore, these circuit boards can bend and fold without breaking or getting damaged. 

A custom ultra-thin LED flexible circuit board is designed with a polyimide substrate, copper layer, and insulating layer.

Also, an adhesive between the copper layer and polyimide substrate offers a strong connection. 

Since they’re very thin and highly flexible, thus occupy less space than thick circuit boards. 

Benefits of Custom Ultra Thin LED Flex PCB

There are several ways you’ll benefit from using a custom ultra-thin LED flex PCB: 

Reduced Material Costs

Most circuit boards sometimes use expensive components like copper or gold and silver.

In the case of ultra-thin LED flex PCBs, you’ll use fewer such components.

Consequently, the production and handling costs will reduce. 

Compatible with Cutting-Edge Methods

While designing and fabricating custom ultra-thin LED circuit boards, you can use cutting-edge technologies like direct laser imaging.

Fortunately, you can employ this technology with exact procedures and caution to avoid errors and harming your board. 


You can host the custom repeating routing pathways on an extra ultra-thin PCB.

This way, you’ll have low service calls thanks to the excellent dependability brought by each board. 

Better Defense

While designing custom ultra-thin LED flex circuit boards, polyimide materials are placed over the conductive materials to offer protection.

Therefore, your circuit board is free from physical damage, such as scratches.

Moreover, they can function under extreme conditions like vibrations and high temperatures without affecting performance. 

High Ductility and Low Mass

As their name suggests, these circuit boards are flexible and built with thin materials.

Therefore, they have high flexibility and low mass. This characteristic reduces the impact and stress on the solder joints. 

Also, it enables the board to withstand extreme conditions like vibration and acceleration.

Without high flexibility and low mass, vibration and acceleration could easily translate into the destruction of solder joints. 


Finally, custom ultra-thin LED flex PCBs are robust and can withstand most flexing cycles.

In short, they won’t get damaged even if you were to fold them extremely. 

Applications of Custom Ultra Thin LED Flex PCB

A smartwatch

(A smartwatch)

To begin with, we understand that flexible circuit boards can bend and fold without damage.

Therefore, we can only expect ultra-thin LED flex circuit boards to possess even more and better flexibility.

Consequently, you can use these circuit boards in tight spaces and design compact electronics. 

As highlighted, a custom ultra-thin LED circuit board attaches LEDs to flexible circuit boards.

Therefore, you can use them to make lightweight, compact electronics.

For this reason, you’ll find these products in wearable lighting like riding safety lamps and head-mounted miner’s lamps. 

How To Make Custom Ultra Thin LED Flex PCB

PCB-making process

(PCB-making process)

Regardless of the type of custom ultra-thin LED flex PCB you want to design, you’re going to follow the following steps: 

  • Ultra-thin LED flex PCB design: The first step is to create a design as per your electronic application requirements. You can seek help from professionals to help develop designs like lighting color change, switching frequency, and induction color change. 
  • Circuit board manufacturing: This step involves prototyping and actual production of the circuit board. Therefore, you must approach a reliable PCB manufacturer to do this for you. 
  • Electronic components sourcing: Next, you can source the different components, including LEDs. 
  • Ultra-thin LED PCB assembly: Assemble the ultra-thin flexible PCB LEDs according to your requirements. This is where wire bonding, flip chip, and tape automated bonding come in. Finally, you can complete the process by taking further steps like thermal aging, IC programming, and functional testing. 

Mounting LEDs on Ultra Thin Flex PCB

Two pieces of LED flexible PCB

(Two pieces of LED flexible PCB)

There are three methods you can use to mount your LEDs to a custom ultra-thin flex circuit board: 

  • Wiring Bonding: This method connects circuit boards and components using bonding wires. The most common materials are gold, silver, aluminum, and copper. In most cases, the wires have a diameter of at least 10µm. Although gold was the most common wire bonding material in the past, it’s slowly being replaced with copper thanks to its low cost. 
  • Tape automated bonding (TAP): This method links semiconductor chips on your ultra-thin PCB to conductors in polyimide or polyamide film carriers. The advantage of this method is that you can fully automate it. Additionally, it produces very light and thin circuit boards. However, using this method, you’ll need specific machines to mount your LEDs. 
  • Flip Chip: Finally, you can use the flip chip method to connect your LED to the circuit board using solder bumps deposited on the chip pads. The resulting product conducts heat better, allows high-speed signal, and reduces inductance. 

Ways of Drilling Microvias While Fabricating Custom Ultra Thin LED Flex PCBs

Microvias form an essential element of custom ultra-thin LED flex circuit boards.

Therefore, you should drill them with the best techniques for results. We have three micros via drilling techniques: 

Plasma Etching Technique

This method involves shooting a high-speed plasma stream in pulses at a circuit board.

The techniques can facilitate drilling a 75µm hole diameter on a 25µm material.

However, the plasma etching method is expensive, making it the least used technique for drilling microvias. 

Photo-via Drilling Technique

This method employs phot-imaginable and lithography patterning dielectric material.

We can credit this technique for advancing custom ultra-thin LED flex circuit boards. 

The method has a hole size of about 25µm for diameter and depth.

However, due to the unique dielectric material in use, this method is expensive. 

Laser Drilling Technique

With laser drilling, you drill through holes by pulsing focused laser energy on the circuit board.

The diameter of the holes can be as small as 50µm.

However, if you require a larger hole, move the laser around the popped hole until you create the diameter you need. 

Generally, the main factors controlling laser drilling are the substrate material, energy density, wavelength, and substrate thickness. 


What’s the difference between single-sided and double-sided custom ultra-thin PCB?

As their names suggest, a single-sided ultra-thin PCB has conductive copper and components on one surface and conductive wiring on the other.

Surprisingly, single-sided PCBs are the most common options thanks to their simplicity. They find applications in printers and calculators. 

On the other hand, a double-sided ultra-thin PCB has a bottom and top layer. Therefore, they have conductive copper and components on both layers.

These circuit boards allow for complex circuitry without point-to-point soldering. 

Are ultra-thin PCBs better?

Ultra-thin circuit boards have unique applications where they function better than other PCB types.

These PCBs are very thin and flexible, thus best for tight space designs.

Also, since fewer materials are used, it’s cheaper to design ultra-thin PCBs than thicker flexible circuit boards. 

Can you design custom ultra-thin flex PCB?

Absolutely! You can design a custom ultra-thin flex circuit with the required skills and experience.

Such skills and experience could take you years to acquire.

Since these circuit boards have a complex manufacturing process, they’re mainly designed by professional designers and engineers. 


Custom ultra-thin LED flex PCBs are ultra-thin circuit boards with light-emitting diodes.

They find significant applications in wearable lighting products like riding safety lamps.

Designers prefer using these circuit boards due to their robustness, high flexibility, and low mass. 

We hope we have answered your questions about custom ultra-thin flex PCBs.

And if not, contact us for further assistance.