Modern PCBs come in all types of shapes, sizes, and materials to meet all types of requirements. While the cheapest and the most common PCB material, FR-4 is quite versatile and can handle most simple applications, but it is limited by its physical and electrical properties to be used on applications with specialised requirements. Therefore, other PCB materials are used for such specialized requirements. One such aspect where FR-4 is simply incompatible is High Power and High heat applications. For such applications, Metal Core PCBs are used. This article will give a brief idea of what metal core printed circuit boards are and when and why you should use them.

What are Metal Core PCBs?

Metal Core PCBs are special PCBs that have a metal-based substrate as the core of the PCB while having a conductive layer to connect components and circuitry. The metal core is separated by a dielectric layer for electrical insulation between the circuitry and the metal core. The primary purpose of using a metal core is to effectively dissipate heat or in other words, for superior thermal management which generally is either difficult or expensive to achieve with other non-metallic-based core materials like FR-4 or Polyimide.

Materials Used in Metal Core PCBs

Different types of applications demand different types of material of metal cores. Although there are not many options for materials for metal core PCBs the available options are mostly considered enough. The core of metal core printed circuit boards is generally made of –

• Aluminium – Aluminium is the most common material used for metal core circuit boards since aluminium is widely available, is easier to fabricate, cost-effective, light by weight and has excellent thermal conductivity.

• Copper – Copper-based metal core printed circuit boards have superior thermal conductivity than Aluminium PCBs but are significantly more costly and heavier. Copper-based metal core circuit boards are rather rarely used due to the cost, availability and difficulty in fabrication.

Properties of Aluminium and Copper Base Metal Core Printed Circuit Boards Are as Follows –

• Thermal Conductivity – is the ability of a material to transfer heat. It gives an estimate of the heat dissipation capability of the material. The higher the thermal conductivity, the better will be the heat dissipation. Higher heat dissipation may also cause difficulties in soldering and assembly.
  Copper Core PCB has a thermal conductivity of 385 W/m·K whereas Aluminum Core PCB has a thermal conductivity of 150–230 W/m·K 

• Density – The mass per unit volume of material, gives an estimate of the weight of a material. Copper has a density of 8.96 g/cm³ and Aluminium has a density of 2.7 g/cm³. Therefore Copper based Metal Core printed circuit boards are around 3 times heavier.

The question arises when should you choose copper-based metal and when should you choose aluminium-based metal core circuit boards? In most of the general metal core circuit board applications, aluminium metal core printed circuit boards are generally sufficient and get the job done for cheaper. However, for specialized applications and miniaturization of high-power electronics, copper metal core printed circuit boards are considered superior.

Why Use Metal Core PCB?

Metal core PCBs have quite useful properties that make them quite favourable for various applications, some of them are –

• Superior Thermal Management Capabilities – Metal core printed circuit boards have very good thermal conductivity when compared to other materials. In fact, metal core circuit boards have higher thermal conductivity than most PCB materials and high thermal conductivity is a prominent factor for choosing metal core circuit boards over other materials. Metal core printed circuit boards do not require heat sinks for heat dissipation and provide uniform heat dissipation to the components of the PCB. 

• Improved Reliability – In many applications, the components are sensitive to a phenomenon called heat accumulation, which may cause the reduction of MTBF or Mean time between failures, which is a critical factor for high-reliability applications. 

• Superior Mechanical Strength – Metal Core circuit boards have enhanced rigidity and durability due to the metal core in the PCB. Better mechanical strength usually results in higher durability and resistance to mechanical stress and jerks.  

• Cost Effective – The cost of the metal core circuit board (especially aluminium-based metal core printed circuit boards) is comparatively lower than other solutions. Materials with higher or comparable thermal conductivity (like ceramic PCBs) are much more expensive than metal-core circuit boards. Other solutions like heat sink increase the volume, BOM complexity and cost and do not provide uniform heat dissipation on the surface of the PCB. 

• High Availability – Although its availability of the fabrication and assembly of metal core printed circuit board may not be as vast as FR-4 but is appreciably good and is much better than other PCB materials like ceramic PCBs.  
• Environmentally Friendly – Metal core circuit boards are considered much more environmentally friendly for disposal than other materials like FR-4 since the metal core can be separated and recycled and the alloy used in the metal core is usually non-toxic. 

Application of Metal Core PCB

Metal Core PCB strikes a good balance between cost and thermal performance. This makes it suitable for various applications. Reliable PCB fabrication manufacturers can produce many kinds of metal-core circuit boards to fit into general applications. Some of them are –

• LED PCBs – Metal Core printed circuit boards are known for their expectational heat dissipation properties, which are required for some LED applications. High-power LEDs generate a lot of heat while in operation. At high temperatures, the performance and the lifetime of the PCB are reduced significantly, hence the generated heat is required to be dissipated quickly to minimize loss in efficiency or lifetime. Metal core circuit boards are most prominently used in headlights, industrial lighting and even consumer lightings.

• Power Electronics PCBs – Many PCBs handling high-power electronics incorporate components that generate high heat. The efficiency of components is reduced at high temperatures and prolonged exposure to high temperatures may also result in permanent damage to components. Therefore many power supplies, AC-DC converters use metal core printed circuit boards to dissipate heat away from components even at high loads 

• Automotive PCBs – Many automotive electronics operate in high temperatures and High heat environments and these devices are required to be highly reliable with very high MTBF. Therefore automotive systems like fuel systems, VCUs, and most dominantly in Automotives lighting like headlights and taillights.