LED Printed Circuit Board (PCB) – Everything You Need to Know – NextPCB
Introduction
The LED, or light-emitting diode, is a remarkable electronic component that transforms electricity into light energy. With its unique characteristics, the LED requires a specialized circuit board to ensure uninterrupted performance. These components generate significant heat, demand high currents, and rely on a robust base for mechanical support. Not every PCB is suitable to accommodate LED-dominant circuits. This is why the LED industry requires specific and dedicated boards.
Understanding LED PCB
What exactly is an LED PCB? In essence, it is a circuit board designed to meet the specific criteria of high-current and thermal stress compatibility for efficient heat dissipation and prevention of current leakage issues. LED PCBs serve as a reliable foundation for LED systems to deliver optimal performance.
Materials for LED PCBs
Choosing the right substrate or core material for LED PCBs is crucial, as it directly impacts the mechanical and thermal properties of the circuit board. Two key considerations when selecting materials for LED PCBs are the glass transition temperature (Tg) and heat conductivity.
Let’s take a closer look at some popular materials used in LED PCBs:
FR4 PCB Raw Material
Thermal Conductivity: 0.25 W/m∙K
Glass Transition Temperature Tg: 140-190℃
FR4 is a standard glass-fiber, fire retardant PCB substrate suitable for various LED circuits. While FR4 comes at a lower cost compared to other substrates, it may not be ideal for circuit boards with demanding functions. Its lower thermal conductivity poses challenges in heat dissipation, potentially leading to heat damage and component issues.
CEM-1 PCB Raw Material
Thermal Conductivity: ≥1.0 W/m∙K
Glass Transition Temperature Tg: 70-130℃
CEM-1 is a paper-based substrate with properties similar to FR4. It is a good choice for single-layer LED circuit boards, offering a balance between thermal conductivity and cost-effectiveness.
CEM-3 PCB Raw Material
Thermal Conductivity: ≥1.0 W/m∙K
Glass Transition Temperature Tg: 70-130℃
CEM-3, belonging to the same family as CEM-1, is an excellent alternative to FR-4. It provides enhanced mechanical strength, effectively managing physical load and offering robust support to the circuit.
Aluminum PCB Material
Thermal Conductivity: 88 to 251 W/m∙K
Glass Transition Temperature Tg: 500K or 226℃
Aluminum is the most widely used metal-based substrate for LED PCBs. With thermal conductivity close to that of copper, aluminum excels in heat dissipation and the ability to handle high currents. It can tolerate mechanical and thermal stress, making it an optimal choice for LED PCBs as it ensures rapid heat dissipation without the need for heat sinks.
By carefully selecting the appropriate material for LED PCBs, manufacturers can optimize the performance, reliability, and longevity of LED systems.
Copper Core PCB Material:
With a thermal conductivity of 398 W/m∙K and a glass transition temperature (Tg) of 634K or 360℃, copper stands as the most exquisite and expensive material. It boasts the highest capacity for heat dissipation and current handling among all substrates. However, its cost surpasses that of other base materials, positioning copper as an ideal but not budget-friendly choice. Nevertheless, if the circuit design necessitates copper as the core material, it is recommended to proceed with it.
Ceramic Base PCB Material:
Ceramic base PCB materials encompass options like aluminum nitride (AIN) and beryllium oxide (BeO). These materials effectively extract heat from its source and transfer it through the board, enhancing the dissipation rate and safeguarding LEDs and other components against thermal damage. Similar to aluminum-backed PCBs, ceramic PCBs provide an affordable alternative with excellent electrical properties and load-bearing capacity. They exhibit remarkable resistance to PCB cracks and gracefully manage current leakage.
Applications of LED PCB:
LED PCBs hold a significant role in the lighting industry. Over time, appliances have increasingly relied upon LED technology for illumination due to its energy-saving attributes and proven environmental friendliness. LED PCBs also find applications in automation, telecommunications, medical, and printing & scanning industries. Their specific roles may vary based on device specifications, but their purpose remains consistent – to deliver a sturdy, heat-compatible PCB.
Advantages and Disadvantages of LED PCB:
Analyzing the advantages and disadvantages helps determine the suitability of an object. Let’s shed light on some pros and cons of LED PCBs.
Advantages of LED PCB:
LED PCBs offer numerous advantages over standard PCBs. Let’s explore a few of them.
Superior Heat Conductivity:
LEDs, as two-terminal semiconductors converting electricity into light, generate significant heat that can potentially damage not only the LEDs themselves but also other components and the entire circuit board. To effectively manage excessive heat, LED PCBs employ highly thermally conductive materials as their base, facilitating heat dissipation throughout the board and thereby maintaining an optimal temperature. This feature distinguishes LED PCBs from ordinary PCBs.
Enhanced Current Handling:
LED PCBs are engineered to handle the varying current ranges (1 to 20mA) associated with surface-mounted LEDs. They incorporate robust features and top-notch materials to mitigate any issues related to current flow.
Effective Thermal Stress Management:
LED PCBs exhibit heightened tolerance for rapid temperature changes, ensuring minimal damage caused by thermal stress, even over prolonged periods of use.
Resistant to Moisture and Dust:
Given their wide application in open environments such as parks and streets, where they are exposed to substantial amounts of dust and moisture, LED PCBs are designed to be resistant to these elements. This resistance significantly extends the lifespan of LED circuits and reduces the frequency of maintenance.
The Main Disadvantages of LED PCB (The Challenges of LED Lighting)
Assembling of Components
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.
Change in Color
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 lifespan of the PCB and LED
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.
Methods to Reduce LED PCB Temperature:
There exist several approaches to lower the temperature of LED PCBs. These techniques are as follows:
Integration with an Aluminum Base:
Incorporating an aluminum base in a single-layer, 2-layer, or 4-layer PCB greatly enhances heat dissipation capabilities, effectively maintaining an optimal temperature.
Utilization of Heatsinks:
Similar to aluminum-backed PCBs, utilizing heatsinks composed of aluminum or copper with superior thermal conductivity aids in absorbing the heat generated by the LEDs. By spreading the heat across a larger area, heatsinks expedite the dissipation process and serve as a reliable means of reducing PCB temperature.
Isolation of Power Driver:
Given the substantial heat produced by power drivers, separating them from the main PCB is advisable to alleviate the temperature rise of the LED PCB.
Maximization of Heat Radiating Area:
Increased surface area directly correlates to a faster heat dissipation rate. Hence, widening the gap between LEDs on the PCB promotes superior heat dissipation while inhibiting the formation of thermal bridges.
Integration of Surface Mount Design (SMD) LEDs:
While any SMD or through-hole LED can be employed in the PCB, the packaging of the LEDs does influence the characteristics of the circuit board. SMD LEDs have gained popularity due to their widespread usage in diverse devices. However, it is worth noting that SMD LEDs have limitations, such as their sensitivity to high currents, fragility, and specific soldering requirements. Despite these limitations, SMD LEDs offer an extended lifespan and produce brighter light compared to standard LEDs.
Advantages of LED Lighting:
LED lighting encompasses captivating benefits from both commercial and residential perspectives. The rapid advancement of LED technology and the increasing demand for energy-efficient solutions have propelled LED lighting to prominence. The advantages of LED lighting are as follows:
Extended Lifespan:
LED lights exhibit an impressively long lifespan, often lasting up to 25 years longer than incandescent lighting.
Optimal Performance in Cold Environments:
Unlike fluorescent lamps, LED lighting performs exceptionally well in cold surroundings. They do not rely on elevated temperatures to deliver maximum efficiency, making them superior to their counterparts.
Reduced Power Consumption:
LED lighting demonstrates monumental energy savings, consuming merely a fraction of the energy used by incandescent lighting—typically around 75% less.
Environmentally Friendly:
LED PCBs, employing non-toxic semiconductors, offer an eco-friendly alternative to conventional fluorescent and mercury vapor lighting. Mercury, commonly found in traditional lamps, poses environmental hazards, requiring specialized disposal methods. In contrast, LED lighting mitigates these concerns, promoting a greener and more sustainable lighting solution.
Why Aluminum is the Most Widely Used Metal in LED PCBs
Aluminum, being the second most thermally conductive metal after copper, is widely chosen for its exceptional heat dissipation capabilities and cost-effectiveness. Its ability to handle high currents and resist PCB cracks makes it the most desirable material for LED PCBs.
Consideration Factors in Designing an LED PCB
When designing an LED PCB, there are several factors that must be taken into consideration. These factors, ranging from material selection to design techniques, play a crucial role in determining the performance and longevity of the circuit board. A meticulously designed PCB, utilizing top-notch materials, ensures flawless performance and an extended lifespan.
Choice of Materials
The materials used in an LED PCB should work collectively to fulfill essential tasks such as providing mechanical support and efficient heat dissipation. While there is a wide range of base materials available for LED PCBs, aluminum stands out as the ideal choice due to its superior heat dissipation properties and other remarkable features. However, careful consideration must be given to selecting the appropriate material for the specific circuit requirements, as it can have implications during assembly, manufacturing, and operation.
Thermal Management
Thermal management is of utmost importance in LED PCBs as LEDs primarily convert energy into heat rather than light. Insufficient thermal management can result in altered light color, decreased intensity, and reduced LED lifespan. Effective thermal management techniques, such as using aluminum materials and heatsinks, are essential to dissipate excess heat and maintain optimal performance.
Trace Routing
Proper trace routing is a critical aspect of PCB design as it ensures uninterrupted and reliable connections among the components. Adequate trace width and spacing prevent signal traces from overheating, minimize cross talk, and reduce electromagnetic interference.
Surface Finish
The selection of an appropriate surface finish is crucial to protect the outer circuit layer from environmental factors and facilitate smooth soldering. Factors such as the operating environment and project requirements need to be considered when choosing the surface finish.
Metal Core
Metal cores in LED PCBs provide exceptional strength and efficient heat transfer properties, ensuring low circuit board temperatures. However, care must be taken with through-hole components, as their leads may cause shorts by coming into contact with the metal. SMD LEDs are often preferred for metal core PCBs due to their compatibility.
Standard Glass Epoxy
Standard glass epoxy materials are a cost-effective option for PCB cores. However, for optimal thermal conductivity, a metal core is recommended over standard glass epoxy materials.
Manufacturing Process of LED PCBs
PCB Designing
The PCB designing stage is crucial as it establishes the material, design pattern, and manufacturing process for the LED PCB. Utilizing tools like Gerber viewers aids in previewing and verifying designs, ensuring the desired wiring layout and functionality.
PCB Manufacturing
LED PCB manufacturing follows standard FR-4 PCB manufacturing procedures. If an aluminum base is required, the manufacturer attaches an aluminum core to a standard PCB to enhance heat transfer and provide additional mechanical support.
PCB Testing
Thorough testing is essential for aluminum-backed LED PCBs. At NextPCB, we conduct comprehensive tests to ensure the delivery of high-quality circuit boards.
PCB Assembly
There are two types of PCB assembly available: through-hole and surface mount. Through-hole assembly is unsuitable for metal base PCBs due to the risk of lead contact with the metal surface causing shorts. NextPCB provides through-hole SMT and mixed assembling services for all types of PCBs, including LED PCBs.
Important Considerations
Number of Layers
The number of layers in an LED PCB is crucial to prevent signal interference, electromagnetic issues, and overheating of trace paths. Analyzing the appropriate number of layers is essential for optimal performance.
Enhancing Lumens
To maximize the lumen output of an LED, high-quality LEDs should be used, and efforts should be made to maintain a low temperature, ensuring bright and long-lasting LED performance.
Our LED PCB Board Capabilities
Our LED PCBs are designed to effectively manage thermal issues, including heat dissipation and prevention of thermal bridges. We prioritize manufacturing quality to minimize performance issues resulting from manufacturing faults.
Supported LED PCB Materials at NextPCB
NextPCB offers a range of LED PCB materials, including FR4 PCB raw material, CEM-1 PCB raw material, CEM-3 PCB raw material, aluminum PCB material, copper core PCB material, and ceramic base PCB material.
In conclusion, LED PCBs require efficient heat dissipation to reduce temperatures and protect components from heat damage. Metal bases and heatsinks are utilized to meet the dissipation requirements, with aluminum being the preferred material for its excellent heat transfer properties. The increasing demand for LED PCBs stems from their high performance and ability to extend the lifespan of LED devices.
