Apart from heat dissipation, metal core PCBs offer good mechanical strength and magnetic conductivity.
Whenever the circuit application belongs to the high switching power category, metal core PCBs are preferred.
One of the best practices in double-sided metal core PCB design is to apply an antipad to indicate the via-hole region that requires an insulating filter.
Selecting the appropriate PCB core depends on the working environment conditions of the PCB. One commonly used PCB core is FR4. FR4 material can't withstand high temperatures; they may melt off when exposed to heat. For high-temperature environments, metal core PCBs are more appropriate.
The thermal characteristics of metal core PCBs means that heat is easily dissipated and critical components continue working without any issues. Metal core PCB design guidelines are different from conventional FR4 design guidelines.
Metal Core PCBs
FR4 material fails to survive in applications where the circuit dissipates large amounts of heat. Choosing a metal core for the PCB helps to dissipate heat without damaging the circuit.
With a metal core, the PCB offers excellent heat conduction and the thermal management of the board is kept under control. The metal core diverts heat away from sensitive components to the heat sink areas or to less critical components. Apart from heat dissipation, metal core PCBs also offer good mechanical strength and magnetic conductivity.
The Structure of Metal Core PCBs
The figure below illustrates the metal core PCB commonly used in LED applications.
Single-Sided Metal Core PCB Material
Aluminum and copper are the base materials often used in metal core PCBs. In LED lighting applications and communication electrical devices, aluminum is used due to its cost-effectiveness. Even though copper showcases superior performance, copper is more expensive than aluminum.
Metal Core PCB Advantages
The metal core and thermally conductive dielectric materials aid in removing heat from the circuit board.
Compared to FR4 material-based PCBs, metal core PCBs offer robust thermal conductivity by using materials with high inter-layer insulation.
Metal core PCBs can withstand contractions and expansions due to temperature variations. The resilience of the circuit is enhanced by the thermal expansibility of the metal core PCB.
The strength and durability of metal core PCBs are greater, as they replace ceramics and fiberglass with metals. The chances of an accidental fracture of the PCB material during the manufacturing process i lower in metal core PCBs.
The properties of thermal conductivity and heat dissipation protect metal core PCBs from heat-induced distortions. Whenever the circuit application belongs to the high switching power category, metal core PCBs are preferred due to their minimal distortions.
Metal Core PCB Design Guidelines
Metal core PCBs are employed in various applications such as audio equipment, LED lighting systems, power regulators, heat sinks, relays, sensor systems, etc. When designing metal core PCBs, there are certain metal core PCB design guidelines to follow.
A metal core can act as a large heat sink or ground plane. When used as a large heat sink, the components and standard power supplies are mounted on the top side. By mounting these, the formation of ground loops is ruled out and the surface temperature is kept low due to the direct heat sink connection. It is better not to ground the metal core's backside when the metal core acts as a heat sink.
Usually, in high-frequency and high-speed circuits, the metal is used as a large ground plane. Metal core ground planes are capable of providing plane capacitance when there is a power-plane present in the board.
Single-Sided Metal Core PCB Holes
In single-sided metal core PCBs, through holes drilled for mounting components should not be plated to avoid short circuits.
Double-Sided Metal Core PCB Holes
Double-sided PCBs carry components on both sides, and plated vias are placed between signal layers. The plated-through holes are formed through the pre-drill-insulating filter and re-drill-plating process, which prevents shorting. The best practice is to apply an antipad to indicate the via-hole region that requires an insulating filter.
As you can see, metal core PCB design guidelines differ slightly from traditional FR4 PCB rules. Cadence OrCAD software can help you design metal core PCBs. Leading electronics providers rely on Cadence products to optimize power, space, and energy needs for a wide variety of market applications. If you’re looking to learn more about our innovative solutions, talk to our team of experts or subscribe to our YouTube channel.