Essential information regarding flexible LED strip substrates

When examining and comparing types of flexible LED strips, one often emphasizes color temperature, LED quantity, and the appropriate power source for the acquisition. Have you contemplated the substrate on which the LEDs are affixed and the manner in which they are interconnected? Today, we will conduct a thorough examination of the LED strip substrate and how certain neglected characteristics and material quality can influence LED strip performance.
 

What function does the LED strip substrate serve?

The LED strip substrate serves as the circuit board upon which the LED chips are affixed. The substrate not only serves as the physical and structural foundation of the LED strip but also facilitates electrical supply through its circuitry and acts as a crucial conduit for heat dissipation.
 

Composition and framework of a flexible LED strip substrate

The predominant variant of LED strip is the flexible substrate variety, available in 16-foot reels. The substrate utilized is referred to as flexible printed circuit technology (FPC). Flexible electronics have existed for some time and are particularly advantageous for applications involving constrained or curved surfaces.
Flexible LED strips leverage this established technology and employ identical foundational substrate characteristics. Typically, polyimide (PI) is the preferred material.
Polyimides offer exceptional durability and thermal resistance while maintaining flexibility. Consequently, the polyimide material is essential for ensuring both flexibility and structural integrity in LED strips.
A foundation circuit of copper is established, followed by the application of one core layer and two outer layers of polyimide polymer, such as Kapton, on both sides with a specialized flexible adhesive. The exterior polyimide layers are generally referred to as the "coverlay" and are available in many colors. White is generally selected to optimize reflection.
The three layers of polyimide confer protection and structural stability to the copper layer. Certain small parts must remain exposed to copper to facilitate electrical contact for the LEDs and other components.
A layer of double-sided tape is ultimately affixed to the rear of the LED strip. The most frequently utilized double-sided adhesive for this purpose is 3M 200MP.
 

The weight of copper is significant.

The choosing of copper is a crucial element in any electronic circuit. The quality and purity of copper utilized in electrical circuits are predominantly standardized; yet, its thickness can vary considerably. Ounces (oz), while a measure of weight, is traditionally employed to denote the thickness of the copper layer, defined by the quantity of copper, in ounces, required to attain a specific thickness over one square foot.
When selecting an LED strip light, consider the thickness of the copper. For high-power LED strips, we recommend a minimum of 2.0 ounces, with an optimal preference of 3.0 ounces or more. All other factors being equal, thick copper is superior for the following reasons:
Increased copper thickness facilitates greater electrical conductivity within the LED strip's circuits. Inadequate copper can result in increased electrical resistance and heat accumulation, ultimately causing voltage drop and premature LED failure.
Increased copper thickness results in expedited heat dissipation. The more rapidly the heat produced by the LEDs is dissipated into the surrounding environment, the more effectively the LEDs will operate and endure. Copper is an exceptional thermal conductor; thus, an increased thickness will substantially enhance the dissipation of heat from the LEDs.
 

Flexible LED strips exhibit inadequate heat dissipation.

The primary disadvantage of flexible LED strip substrates is their inadequate thermal performance. The thermal conductivity of Kapton (polyimide) is 0.12 W/m-K, while that of the 3M adhesive substance is 0.18 W/m-K.
In contrast, aluminum and copper exhibit thermal conductivity values of 205 and 385 W/m-K, respectively, while the dielectric layer in metal-core PCBs can attain 2.0 W/m-K. When appropriately built with thermal vias, the thermal conductivity of a two-layer FR-4 PCB can be considered negligible, as heat can be immediately transported to the backside copper.
Few measures can be implemented; nevertheless, the majority of LED strip products are engineered to prevent overheating. The disadvantage is that the LED strips may be constrained in their capacity to operate at higher intensities, as the heat dissipation is insufficient. This can be likened to a Ferrari engine that cannot operate at its maximum capacity due to a radiator with constrained efficiency.