Thermal Clad PCB
The demand for high-power output is increasing in today’s industry. The high-power electronics generate a lot of heat which, if not managed properly, leads to damage to components or the whole circuit. So, a high-power electric circuit requires effective thermal management and that’s where Thermal Clad PCB comes into play.
Thermal clad PCBs use aluminum or copper as a metal core for heat dissipation which results in a longer lifespan of the PCBs. The metal core offers a low thermal resistance path for heat to flow from high-power components. The standard printed circuit boards do not have a specific mechanism to handle high temperatures and power levels so they cannot be used in such applications.
The thermal management capability of the thermal clad PCBs depends on various factors like the thickness of the metal core, the thermal conductivity of the metal core material, and the dielectric’s thermal conductivity. These PCBs provide an effective solution for applications that need efficient heat dissipation, high temperature, and high power performance. Their effective thermal management, mechanical stability, and reliability make them the best choice for high-power electronics.
What is a Thermal Clad PCB?
A thermal clad PCB also called insulated metal substrate PCB (IMSPCB) or metal clad PCB (MCPCB) is a type of PCB that uses a metal core material such as aluminum or copper for heat dissipation. The metal-clad printed circuit board is used in applications that require efficient heat dissipation like LED lighting, motor controllers, inverters, automotive electronics, power supplies, motor controllers, and more.
Thermal-clad printed circuit boards contain a metal core, dielectric material, and top & bottom copper foil. The metal core is the most important layer in a thermal clad PCB as it provides the low resistance path to heat to dissipate from high-power components on the PCB. The metal core is made of a material with high thermal conductivity like copper or aluminum.
The dielectric material is present between the metal core and the top copper layer. It is usually made of epoxy resin or polyimide, which provides electrical insulation between the copper layers and the metal core. The top & bottom copper layers are used for placing the components and routing of the circuitry.
During operation, the high-power components on the MCPCB generate heat. This heat flows to the metal core through the dielectric material. The metal core acts as a heat sink – absorbs all the heat from the components on the thermal PCB and dissipates it into the surroundings. This process increases the lifetime of the components and the PCB, which is not the case if you use traditional printed circuit boards.
Bergquist is a US-based company that invented thermal clad PCBs in the 1960s. Bergquist MCPCB is one of the best metal PCBs used in various electronic applications to provide efficient heat dissipation and extended lifetime. Henkel is a well-known brand of industrial and consumer businesses, found in 1876. Henkel acquired Bergquist on September 1, 2014 and now offers technological solutions for electronics using Bergquist thermal management products like Bergquist TCLAD and more.
Components of a Thermal Clad PCB
A metal PCB can contain various electronic components like resistors, transistors, capacitors, ICs, diodes, and more. The value, size, and other characteristics of all these components depend on application requirements and need proper consideration for better thermal management. While these are the common components that you can find in any standard PCB as well, here are the main components of a thermal clad PCB.
1. Metal Core Layer
The metal core layer or metal core substrate is the most crucial element of a thermal clad PCB. The electronic components on the PCB generate heat and the metal core substrate provides the thermally conductive path to dissipate all the heat in the surroundings to keep the components and PCB, cool and safe. Before moving on, you should know what is a good thermal conductor. A good thermal conductor is a material that can effectively transfer heat from one point to another.
The metal clad printed circuit board can contain different metal core layers like aluminum, copper, stainless steel, copper-invar-copper (CIC), and more. The most commonly used materials in a metal clad PCB are aluminum and copper.
An aluminum core PCB is more cost-effective than a copper core PCB but copper has a higher thermal conductivity than aluminum so it can be used in applications that require most-efficient thermal management. Before designing a PCB, it is important to select the right core material depending on the requirements of the system.
The metal core substrate in a thermal clad PCB has various advantages over a traditional PCB including effective thermal management, mechanical stability & rigidity to the PCB, and EMI/RFI (electromagnetic interference/radio-frequency interference) shielding.
2. Dielectric Layer
The dielectric layer is sandwiched between the metal core layer and the copper foil layer. It provides electric insulation between the metal core layer and circuitry on the PCB. The dielectric material also plays a vital role in thermal management by facilitating the flow of heat from the electronic components to the metal core layer.
The dielectric layer in a thermal clad PCB is usually made of a material that is highly conductive and offers good mechanical strength. The most common materials used as a dielectric layer in a metal PCB include epoxy resins, polyimide, ceramics, and BT (Bismaleimide Triazine). These materials have high thermal conductivity and can efficiently transfer the heat from the components to the metal core layer.
The thickness of the dielectric material can affect the thermal performance of the PCB so it is important to choose the right thickness depending on the requirements. A thinner dielectric material is vital for a quick heat transfer between the layers but it can decrease the electric insulation between the metal core and the circuitry on the PCB. Thus, the thickness of the dielectric material must be chosen wisely to meet the thermal and electrical requirements of the PCB.
Kinds of Thermal Clad Printed Circuit Board
Thermal clad PCBs have various kinds, each having its own advantages, disadvantages, properties, and features. Here are the most common kinds of MCPCBs.
1. Single Layer Thermal Clad PCB
Single-layer thermal clad PCBs have a metal core, dielectric material, and a single layer PCB of circuitry on one side of the board. They have a high thermal conductivity, which allows them to transfer heat quickly and efficiently. These PCBs are useful for low-density designs where thermal management is crucial but circuitry is quite simple. They are used in various applications including relays, LED lighting, sensors, audio equipment, and automotive electronics.
2. Double-Sided Thermal Clad PCB
These PCBs have a metal core, a dielectric material, and circuitry on both sides of the board. Double-sided thermal clad PCBs are often used for applications where power density is higher and circuitry is relatively more complex. The metal core provides efficient heat dissipation to ensure the long-term reliability of the circuitry. These PCB are used in different applications like traffic systems, industrial controls, HVAC Systems, UPS systems, line reactors, and regulators.
3. Multi Layer Thermal Clad PCB
A multi layer MCPCB has multiple layers of circuitry, a metal core, and a dielectric material. The multiple layers of circuitry are sandwiched between the insulation layers. These PCBs provide the benefits of space and weight. They are compact-sized and used in applications where space is limited and require efficient heat dissipation. Multi-layer thermal clad PCBs are used in various applications including satellite systems, atomic accelerators, heart monitors, file servers, and more.
4. Chip-on-Board Thermal Clad PCB
Chip-on-board (COB) thermal clad PCB takes advantage of both COB technology and TCPCBs. In COB thermal clad PCB, a semiconductor chip is directly mounted on the metal core material, which provides quick and efficient heat dissipation for the chip. The chip-on-board metal clad PCBs have a high thermal conductivity, compact size, and longer lifetime. Some of the main applications that use these PCBs include automotives, high-power LED lighting, street lighting, power supply, and agriculture lighting.
Design Considerations of Thermal Clad PCB
Designing a thermal clad PCB requires a thorough consideration of various elements for effective heat dissipation and reliable operation of electronic components. The metal clad PCB specifications and design vary depending on the specific application. Here are some factors that you should keep in mind before designing MCPCB:
1. Material Selection
Material selection is the most crucial part of designing a thermal PCB. You should consider various factors before selecting all the components. The metal core material and dielectric material should be given high priority during the selection process. Aluminum and copper are the two most commonly used metal core materials in the world. Manufacturers can pick any one of them or other materials like stainless steel based on the application’s requirements.
Likewise, you can use different dielectrics to fulfill your needs. Make sure to consider both the thermal and electronic demands of the application before selecting a dielectric material.
2. PCB Size and Shape
The size and shape of the PCB can have an impact on the thermal conductivity and reliability of the PCB. A large PCB with more surface area can dissipate more heat quicker than a small PCB with a low surface area. But the size should also fit the available space of the application.
Usually, square and rectangular-shaped PCBs are preferred because they are easier to manufacture. Square or rectangular-shaped PCBs can easily be stacked, aligned, and processed in automated machines, which increases their output and lowers the cost. They are also easier to assemble and are better for thermal management.
3. Layer Stackup
In a TCPCB, you should optimize the layer stack up of the board to get efficient heat dissipation. To achieve this, you should place the metal core layer as close as possible to the components that generate high heat.
4. Copper Thickness
The thickness of the copper layer on the top of the PCB can impact the thermal performance of the PCB. If you use a thicker copper layer, it will help in dissipating the heat more efficiently but it will also increase the overall cost of the PCB. So, you should carefully select copper thickness to achieve optimal thermal conductivity without putting much load on the overall cost of the metal PCB.
5. Components Placement
Component placements on the board is another crucial aspect in the designing of the PCB. The components that generate more heat should be placed in the center and near the metal core layer for fast heat dissipation. You should also keep the components that generate more heat away from the sensitive components to avoid any damage.
6. Thermal Pads and Vias
What is thermal pad in PCB and what does it do? Thermal pads and vias can greatly enhance the thermal performance of the PCB. Thermal pads assist in dissipating the heat efficiently by providing a direct path for heat transfer from the component to the metal core. These holes also decrease the thermal resistance between the components and the thermal damage to the components – improving the overall performance of the PCB.
7. Traces
Increasing the width of the traces can improve the heat dissipation efficiency of the PCB. So by using more copper, you can enhance the thermal conductivity of the PCB.
8. Thermal Management Simulation
Before starting the manufacturing process, you must use thermal management simulation software to analyze the working and thermal performance of the board under different conditions. It will help you predict and optimize the thermal performance of the PCB before manufacturing it – saving time and cost in the development process.
Thermal Properties of Thermal Clad PCB
The thermal properties of clad PCB are crucial for their efficient performance and reliability. The followings are the most important characteristics of a thermal clad PCB.
1. Thermal Resistance & Impedance
What is thermal resistivity and thermal impedance of metal PCB? The thermal resistance of metal clad PCB & the thermal impedance of metal PCB determine how much the PCB resists the flow of heat. The thermal conductivity of the metal core layer, dielectric material, and the thickness of each layer affects the thermal impedance of the thermal clad PCB. The lower the thermal impedance of the PCB, the more quickly it will transfer the heat away from the components generating heat.
2. Thermal Conductivity
Thermal conductivity determines the capability of a material to conduct heat away from the heat-generating component. The metal core material and the dielectric material tell the thermal conductivity of thermal clad PCB. A copper core thermal PCB has a higher thermal conductivity than an aluminum core thermal PCB, which means it will dissipate the heat more efficiently.
3. Thermal Expansion
This property is a measure of how much a certain material will contract or expand with the temperature changes. The thermal expansion coefficient (CTE) of a thermal clad PCB depends on the CTE of components used in the PCB, mainly the metal core and dielectric material.
To prevent the stress on PCB during the changes in temperature, it is critical to match the CTE of metal core material and dielectric material. Otherwise, it can cause delamination, cracks, and other damage to the PCB.
Benefits of Thermal Clad PCB
Due to their excellent performance, thermal clad PCBs have become the first choice of PCB manufacturers for high-power and high-temperature applications. They offer huge benefits over traditional FR4 PCBs. Keep reading to find out the main advantages of thermal clad PCBs.
1. Excellent Thermal Performance
The rapid growth in high-power applications like LED lighting, automotives, power electronics, and more have raised concerns about heat dissipation. The standard FR4 PCBs cannot dissipate the heat efficiently from the components, which results in damage to the components and the circuitry. Thanks to the excellent thermal performance of metal core PCBs, now this is no more a problem.
The metal core material of the thermal clad PCB efficiently absorbs the heat from the components and dissipates it to the surroundings. It results in lower temperatures, enhanced performance, and improved reliability of the PCB.
2. Enhanced Power Handling Ability
High-power electronics require an effective system to perform well. If the thermal management of the PCB does not match the requirements of the components, the PCB will overheat and all the components will be damaged. The improved thermal performance of thermal clad PCBs allows them to handle high-power levels without overheating or degrading.
Thermal clad PCBs dissipate the heat efficiently and keep the temperature in control, which makes them ideal for high-power applications.
3. Design Flexibility
There are various kinds of metal core materials and dielectric materials available in today’s market. It gives design flexibility to the MCPCBs. Depending on the requirements and specifications of the application, you can easily find the right metal core material and dielectric material. It also helps you to optimize the thermal and electrical performance of the applications.
4. Improved Strength and Stability
The metal core material and dielectric material in metal clad PCBs help in increasing the overall strength and lifetime of the PCB. The optimized CTE value and thermal performance of these PCBs allow them to handle overheating problems and decrease the risk of delamination or cracks with the change in temperatures.
5. Compact Size and Reduced Weight
Thermal clad PCBs usually have lower weight and size than standard PCBs because the metal core layer in these PCBs dissipates the heat efficiently and there is no need for additional components like heat sinks or fans.
The metal core material also enhances the mechanical stability of the PCB, which greatly reduces the chances of warping or cracking during thermal cycling. This allows the manufacturers to use thinner and more lightweight dielectric layers, which further decreases the overall weight and size of the PCB. This is crucial for applications with size and weight limitations like aerospace, automotive, and portable electronics.
Thermal Clad PCBs Challenges
While thermal clad PCBs offer a lot of benefits, there are some challenges that designers and manufacturers need to consider. Below are some of the major metal core PCB challenges.
1. Plated Through Hole (PTHs)
Making the right holes is one of the main challenges that manufacturers face in the production of metal core PCBs. The thermal expansion and contraction of metal core material in these PCBs can put heavy stress on the PTHs, which can cause barrel cracking, separation, or PTH deformation. This can affect the reliability and overall performance of the PCB.
To minimize the stress on the PTHs, the manufacturers need to choose the right design and manufacturing techniques to produce thermal clad PCBs that are highly reliable and efficient in heat management in power electronics applications.
2. Same Thermal Expansion (CTE) Properties
Understanding the thermal expansion properties of various materials used in the PCB is critical. If the thermal expansion coefficient of the metal core layer is different from other layers of the PCB, it can cause mechanical stress on the PCB, which can lead to deformation or breakage.
Designers should select materials with similar thermal expansion coefficients to overcome this problem. Using smaller footprints or decreasing the number of through holes can highly reduce the stress on the PCB.
3. Extremely Tight Tolerances
The tight tolerance of a PCB ensures that the components fit properly, the single transmission is accurate, and the PCB meets specific performance requirements. It can be challenging to achieve due to the different thermal expansion and contraction rates of the metal core to the other layers of the PCB. This makes it difficult to maintain precise tolerances and dimensions.
To achieve the desired tolerances, designers should use advanced design and manufacturing techniques with attention to detail throughout the manufacturing process.
4. Cost
Thermal clad PCBs are more expensive than the standard FR4 PCBs. It is mainly due to the additional materials and processes involved in designing and manufacturing the MCPCBs. But keep in mind that these PCBs have a longer lifetime and are more reliable than standard PCBs and in the longer run, these PCBs have a clear edge over conventional printed circuit boards.
Applications of Thermal Clad PCBs
Thermal clad PCBs are lightweight, compact, robust, and have excellent thermal performance, that’s why they are used in high-power electronics. The followings are the main applications of a thermal clad PCB.
1. LED Lighting
In high-power electronics, the performance and lifetime of the LED lights depend mainly on how well LEDs are managed thermally. Thermal clad PCBs have become the ideal choice for LED lighting, as the metal core layer absorbs the heat from components and dissipates it efficiently. This results in low operating temperatures of the PCB, full brightness, and improved overall performance.
2. Power Electronics
Power electronics applications like motor controllers, power supplies, amplifiers, gaming consoles, home automation systems, and battery management systems generate a lot of heat during their operation. Metal PCBs play a vital role in their smooth and long-time operations. These PCBs can quickly and efficiently dissipate heat and keep the components cool to enhance their performance.
Thermal PCBs are also crucial for power conversion systems like DC-DC converters and inverters. During voltage conversion from DC to DC or Dc to AC, these systems generate a lot of heat which can damage the equipment if not managed properly. Thermal clad PCBs offer excellent thermal management in these systems by transferring the heat away from the components to the metal core material, which dissipates it efficiently. This allows for higher power densities and better usage of available space.
3. Automotives and Aerospace
Automotive and aerospace applications require PCBs to operate efficiently in extreme temperatures and harsh environments. In addition to that, there are space and weight constraints in these industries. Thermal clad PCBs can easily withstand harsh weather conditions. They are also available in compact sizes and have low weights, which make them an ideal choice for automotive and aerospace applications.
4. Solid State Relays
Solid-state relay applications include HVAC systems, robotics, and industrial automation. These applications require high reliability, fast switching, effective thermal management, and low power consumption. Thermal clad PCBs act as heat sinks, dissipating all the heat away from the power electronics through the metal core layer.
In addition to providing effective thermal management, thermal clad PCBs offer a stable and low impedance ground plane that decreases EMI (Electromagnetic Interference) and improves the electrical performance of the solid state relay.
5. Renewable Energy
Renewable energy systems depend heavily on power electronic systems for better and more reliable conversion, control, and distribution of electrical power. Thermal management is critical in these systems to avoid overheating, enhance efficiency, and increase reliability. Thermal clad PCBs are the ideal solution for thermal management in power electronic systems, such as solar inverters, power distribution systems, and wind turbine control systems, in renewable energy applications.
Conclusion
Thermal clad PCBs are a better solution for heat dissipation in power electronics applications. Thermal clad PCB benefits include enhanced efficiency, high power density, mechanical stability, design flexibility, and great reliability. The metal core material in the clad PCBs keeps the components and circuitry safe, increasing the performance and lifetime of the applications.
These PCBs can pose several challenges to the designers and manufacturers, like material selection, copper thickness, plated through holes, tight tolerances, and more. Designers need to use advanced processes and techniques to overcome these challenges. Despite the challenges, thermal clad PCBs are becoming an increasingly popular choice for a wide range of applications like LED lighting, automotive, motor controls, renewable energy, aerospace, and more.
Their advanced thermal management capabilities enable them to manage heat in power electronics systems, which improves the performance and lifetime of the applications.
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