We have become dependent on the tremendous benefits of electronics in making our lives more convenient. Some very familiar examples include mobile phones, computers, lighting, transportation and many more. The demand for smaller, faster and increased functionality triggered many improvements in the design of various electronic systems. Potential risks stemming from design enhancements include the likelihood of increased thermal problems and higher power densities. One of the effective approaches to address thermal issues is the use of Metal Core PCB.
The market forecast for Metal core PCB looks positive as there is a projected growth in the demand for this type of PCB. This discussion is confined to the definition, advantages and applications of it.
What is a Metal Core PCB?
As the name suggests, a metal core PCB is a category of PCB that has a metal substrate. Metal Core PCB (MCPCB) can also come in different configurations such as single-layer, double-layer and multi-layer MCPCB. This PCB type is mainly used in high-current applications like LED, power controls and inverters. Metal is a better conductor of heat than other types of materials such as polymers and ceramics. So this material is often used by lots of metal core PCB manufacturers. This gives metal core PCB an advantage in dissipating heat.
The typical structure of an MPCB includes a thick metal core, an insulating layer and copper foil, with the metal core acting as a mechanical support and heat spreader. The insulating layer can be organic or inorganic insulation layers which can be done through lamination or anodization processes. The copper foil acts as the interconnection layer where the circuit pattern is found.
What is the Base Material of a Metal Core PCB?
Now, let us jump into the main question: what is the base material of a metal core PCB? There are two most used metal core PCB materials due to their favourable thermal and electrical conductivity. These are copper and aluminium base metals. More details are expounded below for each type of MPCB
- Copper Metal Core PCB: Copper Metal Core PCB is superior to aluminium core PCB in terms of thermal conductivity. This poses a great advantage for very compact systems with high switching frequency and power that need mitigation for heat dissipation. These systems utilise copper metal core PCB than any other PCB. Low-cost FR4 can be used as insulation material and the drilling process can be utilized to form thermal vias on the PCB.
- Aluminum Core PCB: With the advantage of cost, weight and availability, aluminium metal core PCB is a more widespread option for this type of circuit board. Milling is also easier for aluminium MPCB than copper. Aluminum has a coefficient of thermal expansion that is close to that of copper making it a preferred choice if dimensional stability is needed. It is also third in terms of metal core PCB material abundance on Earth thus, cheaper than most metals. Aluminium metal core PCB can be anodized to form an insulating oxide layer.
What are the Benefits of Metal Core PCB?
In metal core PCB material selection, several factors are taken into consideration to qualify the right core material that will best fit the intended performance and reliability of the device. So it gets popular in the metal core PCB manufacturers. Metal core PCB is a good option for many applications as it exhibits positive characteristics as specified below.
- Thermal Management: One of the major reasons why metal core PCB is a top choice for some PCB applications is due to thermal management. High junction temperature resulting from an increase in power density severely impacts the lifetime and performance of components. Heat must be dissipated away from the electronic components to secure the reliability and functionality of devices.
- Dimensional Stability: Metal core PCB also exhibits good dimensional stability. This means that its structure does not change significantly because of external factors such as high temperatures. This is because of the closely matched coefficient of thermal expansion of the material combination in an MPCB.
- Better Electrical Performance: Better electrical performance is a consequence derived from having effective thermal management of metal-core printed circuit boards. As an example, the efficiency of LED lighting is directly affected by the operating temperatures.
- Longer Service Lifetime: Specifically for LED applications, metal core PCBs can draw the heat away from the chip during the conversion of power to heat. Without efficient thermal dissipation, devices may encounter premature failure from excessive stress.
What are the Applications of Metal Core PCB?
The many advantages of metal core PCB are the very reasons why it is a popular option for a wide array of applications. Some of these applications include:
- LED Lighting: As iterated earlier, thermal management is especially important for LED applications. Metal core PCB allows heat to be dissipated well which helps improve optical efficiency and luminance of LED and lighting applications.
- Energy and Power Applications: Power modules used as converters in energy and power applications make use of metal core PCB which serves as a heatsink during operation. MPCB enables optimum performance while maintaining the temperature of the overall system. It is also used for renewable energy sources like photovoltaics for inverter technology.
- Automotive Systems: Metal core PCB is utilized in Electronic Control Units (ECU) of cars. As vehicles are also heavily equipped with lighting for warning and indicator signs, metal core PCB is used for the LED boards for better thermal management. Other automotive parts like navigation and sensor systems use MPCB.
How are Metal Core PCBs fabricated?
MPCB is also fabricated in almost similar steps as traditional PCB except that some parameters such as in drilling, will vary due to different metal core PCB material properties. Lamination is done to complete the dielectric, metalcore and copper layer stack-up, followed by an etching process to remove unwanted copper from the circuitry. As earlier mentioned, there are other methods as to how the dielectric layer or insulating layer is added such as anodization and deposition processes.
Drilling is then performed to incorporate holes and vias on the PCB. Holes are plated with conductive metals to form the circuit path. Copper circuitry is protected from oxidation through the solder masking process. The exposed copper pads go through surface finishing techniques such as organic solderability preservative (OSP) and immersion finishes to promote adhesion during succeeding soldering processes. Finally, silkscreen is done to generate labels and traceability information on the metal core PCB.
