An LED is an electronic component commonly known as a light-emitting diode that converts electricity into light energy. As LED is a complex component, it demands a special circuit board to fulfill the criteria of uninterrupted performance. The LEDs produce excessive heat, operate high currents, and require a sturdy base to be laid on and for mechanical support. Hence, not every PCB is suitable for LED dominant circuits. It is the reason why the LED industry requires specific and dedicated boards.
Now that you have an idea of the requirements of an LED PCB. Let's summarize: What is an LED PCB? Nothing special, a PCB with high-current and good thermal stress compatibility to dissipate heat generated by the LEDs at a faster rate and tolerate high-current without creating issues like leakage of current.
There is a list of substrates (core materials) that meets the requirements of an LED PCB. Though selecting a substrate roughly is not good as it influences the mechanical and thermal properties of the circuit board. Whenever deciding on a material for LED PCB, the least two things to focus on are the glass transition temperature (Tg) and the heat conductivity of the material. Now let's discuss some mainstream LED PCB materials with wide applications in the LED industry.
Thermal conductivity: 0.25 W / m∙K
Glass Transition Temperature Tg: 140-190℃
FR4 is the standard glass-fiber, fire retardant PCB substrate. And it is suitable for a range of LED circuits. The price of FR4 is lower than the cost of many other substrates. But concerning the criteria of LED PCB, FR4 is not a suitable material for circuit boards with intense functions; because it has a lower thermal conductivity, which makes heat dissipation harder, which can raise issues like heat damage in the circuit board and affect the components.
Thermal conductivity: ≥1.0 W / m∙K
Glass Transition Temperature Tg: 70-130℃
CEM-1 is a paper-based substrate and has similar properties to FR4. Many LED circuits require a single-layer circuit board; in that case, CEM-1 proves a good material and provides a balance of thermal conductivity and cost of the PCB.
Thermal conductivity: ≥1.0 W / m∙K
Glass Transition Temperature Tg: 70-130℃
CEM-3 belongs to the same family as CEM-1 and is considered the perfect replacement for FR-4. In terms of mechanical strength, CEM-3 is more robust than FR-4, helps to manage physical load and provides great support to the circuit.
Thermal conductivity: 88 to 251 W/m∙K
Glass Transition Temperature Tg: 500K or 226℃
Aluminum is the most commonly used metal-based substrate. The thermal conductivity of aluminum is as close as that of copper. Further, aluminum is capable of handling high currents and tolerating mechanical and thermal stress. Aluminum, due to its excellent qualities of heat dissipation and current handling, is the most desired material for LED PCBs as it satisfies the reliability scale for LED circuit boards and ensures the fastest heat dissipation without heat sinks.
Thermal conductivity: 398 W/m∙K
Glass Transition Temperature Tg: 634K or 360℃
Copper is the most expensive and high-quality material. Copper has the highest heat dissipation and current handling capacity among all substrates. But the cost of copper is higher than all the other base materials, which makes copper an ideal but not a budget-friendly material. However, if the circuit design demands copper as the core material, go for it.
Thermal conductivity: 321 (AIN) and 325 (BeO) W/(m·K)
Glass Transition Temperature Tg: 242–286 °C
Ceramic base PCB materials include materials like aluminum nitride and beryllium oxide. These materials take the heat from its source and transfer it through the board to increase the dissipation rate and protect the LEDs and other components from heat damage. Like aluminum-backed PCBs, ceramic PCBs are also an affordable option with good electrical properties and load-bearing capacity. Ceramic PCBs are robust against PCB cracks and can handle current leakage gracefully.
LED PCBs are playing a significant role in the lighting industry. In previous years, appliances are getting more dependent on LED technology for light as it reduces energy consumption and is proven environmental-friendly.
Not only in the lighting industry, LED PCBs have applications in automation, telecommunications, medical, and printing & Scanning industries; their roles may vary depending on the specifications of the devices, but the purpose is to provide a rigid heat-compatible PCB.
The advantages and disadvantages are two things that elaborate on an object and help in determining whether it is suitable for you or not. So, here we are throwing light on some pros and cons of LED PCBs.
LED PCBs have numerous advantages over standard PCBs. Let's discuss some of them.
The LEDs are two terminal semiconductors that convert electricity into light. This conversion of electricity into light produces a generous amount of heat that can damage the LED itself, otherwise other components or even the circuit board. To tackle excessive heat-generating issues, LED PCBs use a very high thermal conductive material as the base of the PCB so that it can take out the heat from its generating place and dissipate it throughout the board to maintain the temperature and increase the dissipation rate. It is the most apparent quality of an LED PCB and makes it stand out from other general PCBs.
LED PCBs usually have LEDs surface mounted on them, and as we know, LEDs operate a variety of current ranges from 1 to 20mA. To handle such high current LED PCBs are designed with many good features and the best possible material to avoid current related issues.
LED PCBs have a higher tolerance against rapidly changing temperature and bear neglectable damage due to heat even after years.
LED PCBs are widely used in open areas like parks and streets for lighting, where they expose a lot of dust and moisture. Hence, LED PCBs provide dust and moisture resistance to increase the lifespan of an LED circuit and delay the maintenance time.
Two types of LEDs are available, surface mount and through. Through-hole LEDs are easy to assemble on the circuit board. Whereas surface mount LEDs have a complex assembling process because the components require a specific temperature to be sold properly. A slight change in the temperature can cause damage to the LEDs and raise issues like the disassembly of signal traces, which can spare a whole PCB.
The semiconductor used in the LED decides its color. But in other cases, a constant high temperature has some influence on the color of the LED. For example, LEDs under high operational temperatures usually get dim. The only way to preserve the color of the PCB is to maintain a suitable temperature.
The excess heat in the LED PCBs affects the lifespan of LEDs and PCBs. Common issues raised in a lighting device due to heat include a burnt LED which causes an open circuit.
There are a few techniques to reduce LED PCB temperature. They mainly include
Aluminum has the second highest thermal conductivity in the PCB substrates. Binding a single-layer, 2-layer or 4-layer PCB with an aluminum base boosts the heat dissipation and helps maintain a tolerable temperature.
The heatsink works the same as an aluminum-backed PCB. Usually, the heatsinks use aluminum or copper as they both have excellent thermal conductivity. Heatsink absorbs the heat generated by the LEDs and spreads it on a larger area to fasten up the dissipation rate. Utilizing a heatsink is a reliable way of reducing PCB temperature.
The power driver generates a lot of heat, so separating it from the main PCB can help reduce the LED PCB temperature.
The larger the area, the faster heat will dissipate. Increasing the gap between LEDs on the PCB may aid heat dissipation and prevent the formation of a thermal bridge.
You can use any SMD or through-hole LED in your PCB. However, the packaging does affect the characteristics of the circuit board. SMD LEDs are nowadays widely used in multiple devices and performing well. But there are some limitations that SMD LED comes with itself. For example, SMD LEDs can not tolerate high-current; they are fragile and usually have strict soldering requirements.
Whereas in terms of lifespan, SMD LEDs have a longer life and produce a brighter light than LEDs.
LED lighting offers charming features from commercial and residential perspectives. The rapidly growing technology and increasing demand for low energy consumption emphasize the use of LED as LED lighting meets the criteria of the modern age. LED lighting has a list of benefits, such as
LED lights have a longer lifespan and last up to 25 years longer than incandescent lighting.
Unlike fluorescent lamps, LED lighting does not require a high temperature to provide maximum performance. Even LED lighting performs better in cold surroundings; as in this case, they do not experience heat, the biggest rival.
LED lighting consumes massively low energy. The energy consumption of LED products is as less as about 75% of incandescent lighting.
LED PCBs use semiconductors which are neither toxic nor require special handling afterlife. Hence, LED PCBs are more environmentally friendly than typical fluorescent and mercury vapour lighting, which uses mercury as a part of the lamp. Mercury is not an eco-friendly material and requires careful handling when they reach the end of its life, which is impossible. Hence, LED lighting is an eco-friendly option to avail.
Aluminum is the second highest thermal conductor after copper but is also lower in cost than copper. The aluminum has an excellent ability to handle high currents and resist PCB cracks. That is why aluminum is the most desirable material for LED PCBs.
A PCB engineer should consider several factors while designing an LED PCB. From materials to design techniques, these factors could be anything, but the main thing is that they affect the performance of the circuit board. A well-designed PCB with possibly the best materials guarantees a foolproof performance and a longer lifespan.
The materials used in a PCB should work together to achieve primary tasks such as mechanical support and heat dissipation. There is a wide variety of base materials available for LED PCBs. But by considering the outcomes that an LED PCB demands from the material, we find aluminum the best option to choose as it helps dissipate heat at the fastest rate and has other excellent features too.
The material selection for the circuit board may vary depending on the specifications of the circuit. Hence, it is necessary to consider all aspects of LED PCB design when selecting the material for the PCB. Otherwise, later the material could raise unwanted issues during assembling, manufacturing and working.
The LEDs convert 70% of energy into heat and only 30% into light, which make thermal management a big deal. The heat produced by LEDs results in a change in color of the light, a change in intensity of light and a cut down of the life span of LEDs. Poor thermal management also affects the PCB. Thus, a proper way to manage and dissipate excessive heat is necessary to maintain the performance of LEDs and PCBs. There are several ways of thermal management in an LED PCB. For example, we can use aluminum material, heatsinks and other design techniques to manage most of the heat.
Trace routing is the most significant part of the PCB design; it ensures a non-interrupted and proper connection among all the components. An appropriate trace width with a perfect gap between the traces prevents signal traces from overheating, blocks cross talk and reduces electromagnetic interference among the signals.
The finish protects the outer circuit layer from the environment and ensures smooth soldering. The selection of finish involves several factors, including the operating environment of the PCB, required quality and budget of the project.
In LED PCBs, metal cores provide exceptional strength and heat transfer properties to keep the temperature of the circuit board low. Metal cores do not allow through hole components because the leads of the components can touch metal and cause shorts. On the other hand, the LEDs are widely available in SMD packaging, which makes metal core a good option for LED PCBs.
Glass epoxy is a low price material used for PCB cores. As long as the budget is not a concern, using a metal core is a better option as it has a higher thermal conductivity than the standard glass epoxy material.
PCB designing is the foremost step of the LED PCB manufacturing process. In this step, the designers conclude the material, designing pattern and manufacturing process for the LED PCB.
LED PCB manufacturing follows the procedure of standard FR-4 PCB manufacturing. If the PCB requires an aluminum base, the manufacturer bound a standard manufactured PCB with the aluminum core to boost the heat transfer and provide additional mechanical support to the circuit.
Aluminum-backed LED PCB requires very attentive testing. At NextPCB, we perform several tests on LED PCBs to guarantee the delivery of a high-quality circuit board.
There are two types of PCB assembling available, through-hole and Surface mount. The through-hole assembling is inappropriate for metal base PCBs because the leads can touch the metal surface and create shorts in the circuit. Surface mount assembling is a complex assembly and requires special conditions. At NextPCB, we provide Through-hole SMT and mixed assembling of every type of PCB, including LED PCBs.
The number of layers in an LED PCB is an important factor to consider. LED PCB is complex and requires specific input to provide the required output. Analyzing the right number of layers is significant to prevent cross-talk, electromagnetic issues and overheating of signal traces.
To get the maximum lumen out of an LED, use high-quality LEDs and keep the temperature as low as possible to keep the LEDs bright for longer.
LED PCBs require faster heat dissipation to reduce the temperature of the PCB and prevent components from heat damage. To meet the dissipation requirements, LED PCBs use metal bases and heatsinks. Aluminum as the base material boosts heat transfer.
The demand for LED PCBs is increasing as they provide high performance and help increase the lifespan of LED devices.
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