Electronic Design - The basis of metal core PCB design and manufacturing

Metal core PCBs are not very common in consumer products, but they abound in industry, aerospace, lighting systems, power electronics, and other fields that require high reliability. High-power systems generate a lot of heat, and the heat needs to be quickly removed to prevent component failure. Similarly, low-power systems may be exposed to high heat, and the heat needs to be quickly removed to prevent damage to circuit boards and components.
Metal core PCB design (including DFM) follows many of the same basic design rules as typical PCBs on FR4. If you want to design a new product in any of the above areas, you may need to use a metal core board to control the temperature. In this article, I will briefly introduce the structure of metal core PCB and some important design points to consider before planning to use metal core PCB design. These boards carry special manufacturing requirements, but a suitable design company can help meet these requirements and ensure that the PCB can be mass-produced.
Application of metal core PCB design
Metal core PCBs can find their place in almost any application that generates a lot of heat when the device is running. These plates are not an ideal substitute for ceramics because they are a lower cost option, and they provide higher thermal conductivity to remove heat from important components. They are often a starting point when looking for circuit boards for systems with strong heat dissipation capabilities. Some applications of metal core PCB include:
LED lighting unit: usually a board with high-power LEDs is manufactured on a metal core PCB. These boards provide a solid base for high-power LEDs (SMD and through-hole) while dissipating high heat into the metal core board.
Power conversion and management: Hybrid vehicles, industrial equipment, base station telecommunications equipment and municipal power distribution systems all operate at high power. In these fields, metal core PCBs are common.
Solar energy equipment: Solar energy equipment needs to be particularly rugged and run at high temperatures and high DC voltage/current. Similar PCB designs can be implemented in geothermal facilities.
Military (for example, submersibles, airplanes): Metal core PCBs can quickly dissipate heat, keeping electronics away from electronic equipment that may be located near high heat sources such as engines or exhaust systems.
In many other areas, high reliability and structural rigidity are also crucial, which makes metal core boards an excellent choice. Once you start to study the stacking and layout requirements of these boards, it becomes less obvious how to actually design them. Can multi-layer metal core boards be made? Can it be double-sided? How to deal with vias in the manufacturing process? These are all important issues related to the DFM of metal core PCBs.

DFM for metal core PCB
As with other PCB boards, if you want to ensure a successful manufacturing run, you need to follow specific DFM guidelines. The process used for metal core boards is different from the typical PCB stacking process involving glass woven laminates, so they tend to adopt different DFM rules. The figure below shows a typical stack of a double-sided metal core PCB.
Please note that the stack can be technically adapted as a multilayer board, where the metal core has multiple dielectrics on each side. Or, you can make the circuit board single-sided, leaving the back of the metal core exposed. When designing a metal core PCB, the following are the manufacturing points that need to be paid attention to:
Metal core ground
The metal backing on the PCB can work like a large ground plane or a large heat sink. If the board needs to use a high-speed/high-frequency circuit board module, using the back metal plate as a larger ground plane can provide some shielding. If a power plane is used on the board, it can also provide some plane capacitance.
In addition, the metal core can be used as a large heat sink, especially if it is exposed. The latter aspect is very useful when the board needs to be installed near a high heat source. In this case, when connecting the top side to a standard power supply, it is best not to ground the back side. This prevents ground loops. This will also dissipate the heat directly into the very large heat sink, which helps to reduce the surface temperature.
Hole on single panel
The hole can be placed on the metal core PCB, either as a mounting hole, or as a standard through hole on a double-sided board. If holes are only used to mount through-hole components on a single panel, these holes should not be plated to prevent short circuits. This is done by drilling holes in the mounting holes and filling the holes with non-conductive epoxy or gel. Then, plug the hole so that it can be installed on the upper level.
Hole on double-sided board
In a double-sided metal core PCB, some components may be installed on both sides, and plated vias need to be placed between the signal layers. Pre-drilling - insulating filler - re-drilling - electroplating process to form plated through holes, so some difficulties will be encountered in manufacturing. This process will take additional time and cause additional costs, but it is designed to prevent shorting through vias. In the PCB layout, it is best to use anti-pad to indicate the area around the via that needs to be filled with insulating filler material. Make sure to adjust the size of the via solder mask to comply with the IPC-2221 standard.
DFM is not much different from standard PCB in other aspects of metal core PCB design, although CAD tools are not used to design these circuit boards. The front end of power electronic equipment needs to follow some small rules, especially IPC-2221 (creep and release rules), as well as other standards for defense and aerospace