The prior things your eyes captured while choosing flexible LEDs are the color, temperature, quantity, and assembly method. However, have you ever wondered how these LEDs are integrated into the board and how the connections are formed? Well, this article answers all your questions in detail about the substrate in LED strips, their quantity, material, and specifications.
Role of Flexible LED PCB Strip
The Light-emitting diode strip substrate is a type of circuit board on which the chips of LEDs are mounted. It gives a physical structure to the LED strip. Moreover, it also supports transferring current through all the LEDs while clearing paths for dissipating heat at the same time.
Structure & Materials of Flexible LED PCB
Flexible substrate LED strip is one of the famous types of LED strips. These strips are sold in the form of 16-foot reels. Generally, the FPC type of substrate is used in these flexible LED strips. However, it is widely used in flexible electronic devices, especially with curved and tight spaces.
Flexible LED ribbons used the same substrate-type technology as FPC. Likely to FPCs, polyimide is used as a substrate to make the circuit board. Other than flexible features, polyimide offers phenomenal thermal conduction and durability. That is why polyimide is an essential material for making LED strips for both the structural integrity and high performance of the LEDs.
First, a copper layer is applied, which acts as the base of the circuit. Then a core layer is covered with two external polyimide layers on the sides of the board by using a special adhesive. The outer layer of the polymer is referred to as the overlay. It also comes in various colors. Generally, white color is ideal for enhancing reflectivity.
The outer three layers protect the core copper layer and maintain its structural integrity. However, there are still some areas where copper layers must be exposed to make the connection between the components. In the end, a double-sided adhesive tape layer is placed on the back side of the LED circuit. 200MP 3M adhesive is used as a double-sided tape for this.
Choosing copper is one of the challenging parts of any circuit. The purity and quality of copper used in circuits matter for standardized purposes. However, the thickness of copper is really what matters the most. Generally, an ounce is used as a measuring unit for the thickness of the copper layer in the circuit board.
Therefore, when choosing materials for making LED circuits, ensure to look out for the thickness of copper first. If you’re going to build a high-power light-emitting diode circuit, then look for copper thickness of 2 to 3 ounces or above. Here are some practical reasons why the thickness of copper matters a lot.
- Thicker copper allows a large amount of current to pass through them and then all across the LED circuit. An inadequate amount of copper also leads to higher power resistance which raises the heat level. This leads to a dropping in voltage and damages the LED sooner.
- It also dissipates heat faster than other thermal conductors. The faster the heat transforms into a safe place, the better the circuit will perform. Moreover, it not dissipates heat but also protects the LEDs from getting heated up.
Flexible LED PCB – Poor Heat Dissipation
The biggest disadvantage of flexible LEDs is the poor thermal conduction ability. However, if we calculate the number of thermal conductivity, flexible LED strips only have 0.12 W/m-K polyimide and 0.18 W/m-K adhesive double tape.
If we compare the thermal conductivity between copper and aluminum, then it is much higher in copper than in aluminum which is 385 and 205, respectively. The dielectric can reach up to 2 W/m-K. If it is designed with through-hole techniques, then the thermal conductivity of two integrated layers of FR4 PCB can be ignored easily. It is because the heat is transferred to copper through the backside directly.
There’s nothing you can do much, but mostly the LED strips are designed in such a way that they don’t heat easily. We can blame LEDs’ ability to run that way because thermal dissipation cannot be done faster. You can also take it as a Ferrari whose running potential is limited due to the less effective radiator.
- However, the best possible way to overcome the thermal issue is simply to switch your circuit to traditional FR4. To do this, you have to say goodbye to the flexibility feature. But you can get enhanced thermal conductivity if it is what you want the most.
- Make sure to check the thickness of copper traces. There is a high chance of using a lot of currents here when the temperature rises due to circuit resistance.
- If the thickness of copper is a bit challenging, then you can also reduce the number of LEDs on the strip. This could also work.
- On the other hand, if your motive is more brightness in one strip rather than thermal conduction, then increasing the number of LEDs in parallel forms enhances the brightness.
Flexible LED PCB Strip Design Fabrication Process
Flexible LED PCBs are easy to make; you just have to follow the following steps, and your flexible LED PCB strip is ready to go.
1. Flexible LED PCB Design
First of all, make a design of a flexible printed circuit board according to the product’s requirements. If you are unsure about your design, then you can get help from online PCB design software. You can share your design with them, and a community of experienced designers will be ready to give you their precious feedback.
2. Flexible LED PCB Manufacturing
Choose the method of printed circuit boards according to your design and the requirements of the product. Make sure whether you want a single-layer PCB or a multi-layer. Check the copper thickness and the method of mounting.
3. Electronic Components Sourcing
The third step is essential in the circuit board. Placing the components in the right position at the right angle with the right mounting adhesive. As you already noted, which component and which adhesive is used, then just mark the position of the components and place them carefully.
4. PCB Assembly
Then start the assembly process of LED strips onto the circuit board.
5. PCB LED Strip Assembly
After the successful assembly of LEDs, the strip onto the surface of the circuit board, the PCB goes through test phasing, where thermal conductivity, its functionality, and IC programming come.
Flexible LED PCB strips are flexible LEDs that are made on flexible boards rather than conventional rigid aluminum boards. It is widely used in many products that are prone to harsh environments and tight spaces. The only downside of the flexible LED PCB strips is the poor dissipation of heat.