Aluminium core PCBs are printed circuit boards in which the core of the PCB is a metal layer. Typically, this metal core is aluminium, since it is the cheaper option, but other materials could be used as copper or other metal alloys that would increase the performance in terms of thermal dissipation, but also the price. Other benefit of the aluminium with respect the other metal cores is the weight, that is much lower.
These aluminium core PCBs can be single layer (only substrate above the metal laminate) or multilayer, one or more layers in the top and/or bottom of the metal core. Typically, the substrate that is combined with the metal core is FR4.
Between the metal core and the FR4 an insulation layer is placed with a very high conductivity in order to have a very low thermal resistance, and in this way, the heat from the components is easily conducted from the components to the metal core.
Aluminium core PCBs advantages/disadvantages
These printed circuit boards were developed to have the possibility to improve the heat dissipation over typical PCBs when high power consumption components or many dissipating ones are placed over the PCB.
Below, the main advantages of these aluminium PCBs are shown:
The main advantage of aluminium core PCBs is the improvement of the thermal dissipation of the PCBs and all the components that compose the electronic circuit.
This thermal dissipation improvements allows the designer to have higher power dissipation components in a lower size than with typical PCBs.
The PCB will be more robust than with typical FR4 PCBs, especially when low thickness PCBs are used thanks to the stiffness of the aluminium.
The reliability of the electronic circuit will be better since the power dissipation will be better and the temperature of the modules will be lower, at the same ambient temperature, than if a typical FR4 PCB was used.
For very high power consumption circuits based on FR4 PCBs that will require baseplates, radiators or fans, the use of metal core PCBs could avoid the use of these baseplates, radiators or at least, reduce the size of them, and also the fans could be avoided.
If heatsink/radiators are required, the thermal resistance connection between the PCB and the heatsink will be reduced and the thermal conduction improved. In this way, the components over the PCBs will be cooled down in a better way.
High power amplifiers or transistors with metal pads for the ground pads can be placed directly over the aluminium core to improve the power dissipation.
Many times, the size of the PCB can be reduced and in this way the size of the module. This is because for a good thermal performance, when using a typical FR4 PCB, the high power consumption components must not be placed close to each others. When using metal core PCBs this is not a problem since the heat is spread to the metal core and not to the other components.
The metal core can also be used to reject electromagnetic signals from the top to the bottom of the PCB.
The insulation layers between the metal layer and the FR4 helps to improve the mechanical stress of the board at different temperatures.
Some disadvantages of this kind of PCBs with respect typical FR4 PCBs are:
Aluminium core PCBs will be more expensive than typical FR4 PCBs.
The weight of the metal core PCBs will be higher than typical PCBs.
When components are required to be placed in the top and bottom of the PCB, the complexity of the PCB increases when it is required to interconnect electrically the top and bottom layers.
Aluminium core PCB characteristics
Different thickness of the aluminium core can be selected, typically between 0.4 to 2.4 mm.
Different FR4 layers can be placed in the top or bottom of the metal core, with different substrate and copper thickness to have the final stack up you will need.
Aluminium core PCBs applications
This kind of PCBs has many applications but the most important ones are stated below:
LED applications. Since the LEDs release a lot of heat, the circuitry used need to have a very good heat dissipation.
3D printer heated beds. The power consumption of these modules is very high but also the required size is small. For this reason. for this application aluminium core printed circuit boards are typically used.
Power supplies, AC/DC converters and regulators. Due to the efficiency of these components they typically present a high power consumption in small sizes.
Digital electronics including FPGAs, ADCs, DACs, etc or even CPUs
Audio devices that used power amplifiers.
Telecommunications applications for high power amplifiers.
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