Metal Core PCB means the core (base) material for PCB is the metal, not the normal FR4/CEM1-3, etc., and currently, the most common metal used for MCPCB manufacturers are Aluminum, Copper, and steel alloy. Aluminum has good heat transferring and dissipation ability, but yet is relatively cheaper; copper has even better performance but is relatively more expensive, and steel can be divided into normal steel and stainless steel. It is more rigid than both aluminum and copper, but its thermal conductivity is lower than theirs too. People will choose their own base/core material according to their different applications.
Generally speaking, aluminum is the most economic option considering its thermal conductivity, rigidness, and cost. Therefore, the base/core material of a normal Metal Core PCB is made of aluminum. In our company, if no special requests, or notes, the metal core refer will be aluminum, then metal backed PCB will mean Aluminum Core PCB. If you need Copper Core PCB, Steel Core PCB, or Stainless steel core PCB, you should add special notes in the drawing.
Sometimes people will use the abbreviation “MCPCB”, instead of the full name of Metal Core PCB, Metal Core PCBs, or Metal Core Printed Circuit Board. And also used different word refers to the core/base, so you will also see the different names of Metal Core PCB, such as Metal PCB, Metal Base PCB, Metal Backed PCB, Metal Clad PCB, Metal Core Board, and so on. The metal core PCBs are used instead of traditional FR4 or CEM3 PCBs because of the ability to efficiently dissipate heat away from the components. This is achieved by using a Thermally Conductive Dielectric Layer.
The main difference between an FR4 board and a metal based PCB is the thermal conductivity of dielectric material in the MCPCB. This acts as a thermal bridge between the IC components and the metal backing plate. Heat is conducted from the package through the metal core to an additional heat sink. On the FR4 board, the heat remains stagnant if not transferred by a topical heatsink. According to lab testing an MCPCB with a 1W LED remained near an ambient of 25C, while the same 1W LED on an FR4 board reached 12C over ambient. LED PCB always is produced with an Aluminum core, but sometimes steel core PCB also be used.
Advantage of metal backed PCB
1. Heat dissipation
Some LEDs dissipate between 2-5W of heat and failures occur when the heat from a LED is not properly removed; a LED’s light output is reduced as well as degraded when the heat remains stagnant in the LED package. The purpose of an MCPCB is to efficiently remove the heat from all topical ICs (not just LEDs). The aluminum base and thermally conductive dielectric layer act as bridges between the ICs and the heat sink. One single heat sink is mounted directly to the aluminum base eliminating the need for multiple heat sinks on top of the surface-mounted components.
2. Thermal expansion
Thermal expansion and contraction are the common nature of the substance, different CTE is different in thermal expansion. As their own characteristics, aluminum and copper have a unique advance to normal FR4, thermal conductivity can be 0.8~3.0 W/c.K.
3. Dimensional stability
It is clear that the size of the metal based PCB is more stable than insulating materials. The size change of 2.5 ~ 3.0% when Aluminum PCB and aluminum sandwich panels were heated from 30 ℃ to 140 ~ 150 ℃.