Multilayer Metal Core PCBs, also known as MCPCBs, are specialized circuit boards that combine the benefits of metal core construction with the advantages of multilayer design. These PCBs are widely used in applications that require efficient heat dissipation and high-density circuitry. In this article, we will explore the features, benefits, and applications of multilayer metal core PCBs.
What Is Multi-layer Metal Core PCB?
A multilayer metal core PCB, or MCPCB, is a type of printed circuit board that incorporates a metal core within its structure. Unlike traditional PCBs that use a non-conductive substrate, such as FR4, MCPCBs have a layer of metal, usually copper or aluminum, as their core material. This metal core provides several advantages, including improved thermal conductivity and heat dissipation capabilities.
Multi-layer MCPCBs consist of multiple layers, typically with two copper conductor layers on either side of the metal core. These layers are connected by a dielectric material, forming a sandwich-like structure. The metal core serves as a thermal insulator, efficiently dissipating heat generated by the components on the PCB. This is particularly beneficial in applications where thermal management is critical, such as in high-power LED lighting, power electronics, and automotive systems.
The number of layers in a multilayer metal core PCB can vary, ranging from two to several layers, depending on the complexity of the circuit design. The additional layers allow for more efficient routing and increased design flexibility. It is also possible to incorporate multilayer dielectric stacks on both sides of the PCB, further enhancing its functionality.
In terms of construction, MCPCBs require an additional pressing step to bond the metal core with the copper conductor layers. This ensures a secure and reliable connection between the layers. The thickness of the metal core material typically ranges from 1mm to 4mm, depending on the specific requirements of the application.
Overall, multilayer metal core PCBs offer unique characteristics, including superior thermal management capabilities, excellent heat dissipation, and improved reliability. They are widely used in various industries where thermal performance is crucial, providing a reliable and efficient solution for demanding electronic applications.
Benefits Multilayer Metal Core PCB
Multilayer metal core PCBs (MCPCBs) offer several notable benefits, making them a preferred choice in many applications:
1. Efficient Thermal Management: MCPCBs excel in thermal dissipation due to their metal core, which provides a highly conductive path for heat to dissipate. Unlike standard FR4 PCBs, MCPCBs do not require vias for thermal relief. The entire bottom side of the board consists of metal, enabling efficient heat transfer away from heat-generating components. This feature is particularly advantageous in applications where heat management is critical, such as LED lighting systems and power circuits.
2. High Thermal Conductivity: MCPCBs possess significantly higher thermal conductivity compared to traditional FR4 PCBs. Typically made from materials like aluminum, which has excellent thermal conductivity, MCPCBs can efficiently transfer heat away from sensitive components, preventing overheating and ensuring optimal performance.Due to the high thermal conductivity of aluminum, the dielectric layer in MCPCBs is deliberately kept very thin, usually ranging between 0.003 and 0.006 inches in thickness.
3. Enhanced Power Handling Capability: Due to their superior thermal management capabilities, MCPCBs can handle higher power levels and higher component density. The efficient dissipation of heat helps prevent heat-induced performance degradation or failure of components, allowing MCPCBs to support demanding electrical and electronic applications.
4. Reduced Drilling Requirements: MCPCBs require minimal or no drilling during the manufacturing process. Only a few larger holes are necessary for mounting purposes, simplifying the production process and reducing manufacturing costs.
5. Cost-Effectiveness: MCPCBs are often fabricated using aluminum, which is a cost-effective and readily available material. This makes MCPCBs a more affordable option compared to other high-performance PCB technologies, without compromising on thermal efficiency.
6. Longevity and Reliability: By effectively managing heat dissipation, MCPCBs contribute to improved circuit reliability and the longevity of electronic components. Controlling operating temperatures within acceptable limits helps prevent thermal stress and extends the lifespan of sensitive parts, reducing the likelihood of premature failures.
7.Design Flexibility: MCPCBs offer design flexibility, allowing for the integration of multiple layers and complex circuitry. This enables the creation of compact, space-efficient PCB designs without compromising thermal performance.
Structure & Base Materials for metal core PCB
The structure of a metal core PCB consists of several layers, each serving a specific purpose in the functioning of the circuit board. The primary components of a metal core PCB are:
1. Metal Core: The metal core is the central layer of the PCB and is typically made of copper or aluminum. The metal core provides mechanical strength to the PCB and acts as a thermal conductor, dissipating heat generated by the components on the board.
2. Dielectric Layer: The dielectric layer separates the metal core from the conductive layers. It is usually made of a thermally conductive material that also provides electrical insulation. The dielectric layer ensures that there is no electrical contact between the metal core and the conductive layers.
3. Conductive Layers: The conductive layers are typically made of copper and are located on either side of the metal core. These layers are responsible for carrying electrical signals and provide the necessary connectivity for the components on the PCB. The conductive layers can be patterned with traces, pads, and vias to create the desired circuitry.
4. Solder Mask: The solder mask is a protective layer applied over the conductive layers. It helps to prevent solder bridges and ensures proper soldering of components. The solder mask is typically green in color but can also be other colors depending on the application.
5. Silkscreen: The silkscreen layer is used to add component labels, part numbers, and other markings on the PCB. It provides visual guidance for component placement and assists in assembly and troubleshooting.
As for the base materials used in metal core PCBs, the following options are commonly utilized:
1. Copper: Copper is the preferred metal core material due to its excellent thermal conductivity and electrical properties. It provides efficient heat dissipation and is widely used in high-performance applications. However, copper is more expensive compared to other options.
2. Aluminum: Aluminum is an alternative metal core material that offers good thermal conductivity at a lower cost compared to copper. It is commonly used in applications where cost is a significant factor, such as consumer electronics and automotive lighting.
3. Alloy Substrates: Some metal core PCBs use alloy substrates that combine different metals to achieve specific properties. These alloys may provide a balance between thermal conductivity, cost-effectiveness, and mechanical strength.
The choice of base material depends on various factors, including the application requirements, thermal management needs, and budget considerations. Each material has its own advantages and limitations, and it is essential to select the most suitable option for the specific application to ensure optimal performance and reliability.
How to Build Multilayer Metal core PCB?
Building a multilayer metal core PCB involves several steps. Here is a general overview of the process:
Begin by designing the PCB using PCB design software. Determine the number of layers needed, the placement of components, and the routing of traces. Consider thermal management requirements and plan the layer stackup accordingly.
Decide on the layer stackup configuration, including the number of metal core layers, dielectric layers, and conductive layers. Specify the thickness of each layer and the material to be used.
Choose the appropriate metal core material, such as copper or aluminum, based on the thermal conductivity and cost requirements of your application. Select a suitable dielectric material with good thermal conductivity for the insulation between layers.
4.Preparing the Metal Core:
Start with a metal core sheet of the desired thickness. Cut the metal core into the required shape and size for the PCB. Ensure that the surface of the metal core is clean and free from any contaminants.
5.Prepreg and Copper Foil:
Apply prepreg, a layer of resin-coated fiberglass, to both sides of the metal core. Then, add a layer of copper foil on top of the prepreg. The prepreg acts as an adhesive layer and helps bond the copper foil to the metal core.
Place the metal core, prepreg, and copper foil layers together in a lamination press. Apply heat and pressure to bond the layers together. This process forms the multilayer structure of the PCB.
Drill holes through the entire stackup where vias and through-hole components will be placed. These holes will later be plated to provide electrical connections between the layers.
Electroplate the drilled holes with a conductive material, such as copper, to create plated-through holes (PTHs). This ensures electrical connectivity between the layers.
Apply a photoresist layer to the outer copper layers. Expose the photoresist to UV light through a photomask to create the desired circuit pattern. Develop and etch the exposed areas, removing the unwanted copper.
10.Solder Mask and Silkscreen:
Apply a solder mask layer over the conductive layers, leaving openings for component pads. Add a silkscreen layer for component labeling and other markings.
Apply a surface finish, such as HASL (Hot Air Solder Leveling), OSP (Organic Solderability Preservative), or ENIG (Electroless Nickel Immersion Gold), to protect the exposed copper and facilitate soldering.
12.Testing and Inspection:
Conduct electrical testing and visual inspection to ensure the PCB meets the required specifications and quality standards.
Finally, assemble the components onto the PCB using surface mount technology (SMT) or through-hole soldering techniques.
It is important to note that building a multilayer metal core PCB requires specialized equipment and expertise. Working with a professional PCB manufacturer or assembly service provider is recommended to ensure a high-quality end product.
Multilayer Metal Core PCBs offer a unique combination of thermal management and circuit density, making them ideal for various high-power and high-temperature applications. Their ability to efficiently dissipate heat and provide electrical insulation makes them suitable for industries such as automotive, LED lighting, power electronics, and telecommunications. With their exceptional performance and reliability, multilayer metal core PCBs continue to revolutionize the electronics industry, enabling the development of advanced and compact electronic devices.