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  • Writer's pictureFlex Plus Tech team

Why do we need attach aluminum sheets to flex circuit board?

In circuit board factories, we often see aluminum sheets attached to flexible printed circuit of different shapes. This is a common process. Usually, an adhesive is used to precisely attach the aluminum sheet to the circuit board. This process can be completed with the assistance of a special jig. Its main purpose is to enhance heat dissipation, provide mechanical support, and improve overall reliability. Aluminum sheets have good thermal conductivity and mechanical strength, and are often used as stiffener materials for flexible PCB. It can improve the heat dissipation performance of circuit boards and prevent damage under high temperature or mechanical stress. This type of flexible printed circuit is commonly used in automotive lights.

flex pcb with aluminum sheet

What is the role of flex circuit board with aluminum sheets in automotive lights?


  • Increase heat dissipation performance

Headlights, especially LED headlights, generate a large amount of heat during operation. Excessive temperature can affect the performance and lifespan of electronic components, therefore effective heat dissipation measures need to be taken. Aluminum can quickly transfer heat from a heat source, reducing the temperature of circuit boards and electronic components. Through aluminum plates, heat is more effectively distributed to larger area or transmitted to radiator or the metal parts of the vehicle body, thereby improving the overall heat dissipation.


  • Provide mechanical support for flexible circuit board

Although flex PCBs have good flexibility, their mechanical strength and stability are poor, and they are prone to damage or deformation under external forces. After adding aluminum plates, the flex PCB receives additional mechanical support, improving its rigidity and avoiding damage caused by vibration and impact. Aluminum sheets can also help fix the shape of the flex PCB, keep it stable during installation, and ensure that the position and function of the circuit board in the headlight are not affected by the outside.


  • Improve reliability

In the car usage, headlight has to undergo different environmental conditions like high temperature, low temperature, humidity, vibration and impact. Aluminum sheets can not only assist in heat dissipation and mechanical support but also act as a shield to the circuit board from external interferences such as electromagnetic interference or physical damage. The aluminum sheets enhance the life of the circuit boards as well as that of headlights by improving heat dissipation and strengthening their mechanical strength thus improving their reliability and stability.


Headlight Flex PCB, aluminum PCB
Headlight Flex PCB

How do we choose the thickness of Aluminum Sheets?

High power LED headlight generates huge amounts of heat hence usually need aluminum sheets with moderate thicknesses for effective cooling. For instance, 1.5mm or 2mm thick aluminum sheets are sufficient for this purpose due to adequate heat capacity and thermal conductivity which they possess. Thick aluminum sheets can absorb and store more heat, delay the speed of heat transfer to the environment, and effectively prevent component overheating. For low-powered headlights or those with less heat discharging requirements, one should select a thinner aluminum sheet which may be 0.8mm thick or 1mm thinness. Thin aluminum helps in cutting material costs and process difficulties, and is suitable for projects with tight budgets.


Why do we paste aluminum sheets on flex PCB instead of using aluminum PCB directly?


automotive light flex pcb, flex pcb with aluminum  sheet, Aluminum heat sink
Flex Plus's FPCB for automotive lighting

The main considerations for pasting aluminum sheets on flex PCB are as follows:

  • Weight and thickness restrictions: A whole piece of aluminum material is usually thick and heavy, which may not be suitable for lightweight electronic devices and applications requiring thin designs. Flexible circuit boards themselves can meet the strict requirements of modern electronic devices for volume and weight with their thin and flexible characteristics. By pasting aluminum sheets on flexible substrates, excellent thermal management capabilities and mechanical strength can be provided while maintaining a thin and light design.


  • Cost-effectiveness: Using a whole piece of aluminum material to make a substrate is expensive and the processing process is complicated. In contrast, aluminum sheet-pasted flex PCBs use a combination of film substrates and aluminum sheets, which can not only reduce manufacturing costs, but also enable more flexible processing and customized designs during the production process to adapt to different application requirements.


  • Flexibility and adaptability: Aluminum-coated flexible printed circuit maintain the original softness and bendability of flexible printed circuits while enhancing their mechanical strength and thermal management capabilities by adding aluminum sheets. This makes it suitable for a wider range of application scenarios, such as devices that need to be bent frequently or subjected to mechanical shock, while a whole piece of aluminum may not meet these needs.


  • Technical advantages: Aluminum-coated flexible printed circuits use advanced lamination technology and composite material processing technology to effectively manage the heat generated by the device while maintaining stable circuit connections and signal transmission. This makes it outstanding in high power density and high frequency applications, making it an ideal choice for many advanced electronic products.


This solution allows to combine the adaptability of Flex PCB to the requirement of heat dissipating, providing an innovative solution for modern electronic devices. If you have any questions or needs in this regard, please feel free to contact Flex Plus at any time. Our technical team has professional knowledge to answer your questions and help you find the circuit board that suits your needs.

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