According to PCB Trace, the electronic industry classifies printed circuit boards as different types that include single-, double-, and multi-layer boards of rigid, flexible, rigid-flex PCBs, and metal clad PCBs. For instance, flex PCBs for creating soft light strips are very common.
LED light strips are a popular decorative feature that has benefited from technological advancements. By making them flexible, these LED strips are very convenient for the purpose of lighting and decoration. To make efficient use of flexible LED light strips, it is necessary to understand the structure of flexible boards and their role in the LED strip.
Flexible PCBs
Flexible printed circuit boards, or flexible circuits, are a special type of boards that can bend to any shape. Mostly applicable for high temperatures, they are also useful for high-density applications. The substrate material in flexible PCBs is transparent polyester or Polyimide. These can withstand high temperatures and very suitable for soldering LEDs on them.
Flexible PCBs for LED Strips
LED strips are basically individual circuit boards with electrical interconnections. Flexible PCBs comprise most of such strips, with SMD LEDs mounted on them. In other words, the flexible PCB forms the substrate on which manufacturers mount SMD LEDs. Besides providing a flexible structure, the substrate material also helps in dissipating the heat generated by individual LEDs when operating.
The high flexibility of the LED strips allows stringing up the strip into any shape. LED strips are commonly available in 5-meter long reels. There are various types of circuits available for LED strips:
Single Layer Flex PCB
The single-layer flex PCB has only a single 1-oz conductive layer on a substrate base. The conductive circuit has a protection of solder mask along with a silkscreen layer. The bottom surface does not have any conductive layer. The single layer flex PCB feels very light.
A single layer flex LED PCB constitutes:
- Substrate — This is the base material forming the PCB. Polyimide is the most common materials that manufacturers use for making substrates. Polyimide is highly stable and can withstand high temperatures.
- Conductors — The conducting layer is made of copper foil, bonded to the Polyimide base. Manufacturers use chemical etching to create the necessary electrical circuit by removing unwanted copper.
- Protective Finish — These are coverlays or overlays to protect the conductive electrical circuit.
- Adhesive Material — Epoxy resin or Polyethylene acts as the adhesive material that manufacturers use to bond the above layers together.
Double Layer Flex PCB
Unlike the single layer board, a double layer flex PCB has two conductive layers on either side of a substrate base. The two conductive layers make it thicker, heavier, and more durable than a single layer flex board.
With more conductive layers, a double layer flex PCB can carry higher currents, while dissipating more heat. Although the single layer flex PCB is cheaper for LED strip lights, a double layer flex PCB offers better light output, as it can use brighter LEDs because of higher heat dissipation capability. The thicker board improves the stability and the strip has a longer lifespan.
A double layer flex LED strip PCB constitutes many layers:
- Top silkscreen layer showing position of various electronic components
- Top protective layer as coverlay or overlays, highly reflective
- Top 35 µm conductive layer for mounting electronic components like LEDs and resistors.
- Substrate layer as the core material
- Bottom 35 µm conductive layer
- Bottom protective layer as coverlay or overlays
- Adhesive layer for mounting the strip
- Protective liner for adhesive layer
Copper Weight in Flex LED Strip PCBs
The choice of copper forms the key aspect of any electronic printed circuit board. Although manufacturers have largely standardized the purity and quality of copper that they use in electronic circuit boards, they have the freedom of selecting its thickness. They specify the thickness of copper in ounces, based on weight of copper necessary to cover a unit square foot of the board.
For LED strips, it is important to pay attention to the copper thickness on the board. As current consumption depends on the power of the LEDs in the strip, higher power LED strips may use copper thickness equivalent to 2, 3, or 4 ounces. Although thicker copper reduces the flexibility of LED strips, it has certain advantages:
- Larger current handling — Manufacturer can use LEDs of higher wattage that need higher current to operate efficiently.
- Better heat dissipation — Thicker copper helps in faster heat dissipation. This is helpful as LEDs of higher wattage will also generate more heat when operating. Faster and better heat dissipation improves the performance of the strip, thereby increasing its lifespan.
Application of Flex LED Strip Lights
Flexible LED strip lights are very popular as it is possible to apply them not only to curved surfaces, but also to any nonlinear surface. Their ease and ability to conform to any type of turn increases their popularity, without requiring cutting them into segments and using connectors to rejoin the segments.
The compact size, high brightness and low power consumption of the flex LED strip lights makes them popular in many lighting applications like in bars, homes, architectures, restaurants, and shop displays. Manufacturers offer many types of color LEDs mounted on the same type of flexible PCB.
Advantages of Flex LED Strip Light PCBs
High Flexibility
Because of the flexible nature of the substrate material in the PCB, the strip light PCB has high flexibility. This allows applications of the LED strips to a variety of complex environments. The high flexibility of the strip light allows changing its angle at any corner.
Lightweight and Ease of Mounting
As flex PCBs are lighter than their rigid counterparts, they do not require any complex method of mounting them. Securing them with double-adhesive tape is enough for most applications.
Limited to Lower Wattage Output
Although flex LED strip light PCBs are good in heat dissipation, their thermal performance is still poor compared to metal core PCBs. Consequently, it is not possible for manufacturers to use high-power LEDs in strip light flex PCBs.
Conclusion
With more than two decades of experience in manufacturing different types of printed circuit boards, PCB Trace is an expert in manufacturing various types of flexible boards. All our boards use excellent substrates that maintain stable performance under any operating conditions. Whether it is for medical, lighting, or military applications, our high quality flexible boards retain their flexibility even after undergoing heat curing processes.
