Aluminum PCB has come in vogue in last decades, essentially because of its splendid properties in all aspects including electric performance, heat dissipation capability, electromagnetic shield, and good dielectric strength. Aluminum PCB referred as metal base PCB, is a type of PCB which consists of copper clad laminated and thin dielectric and thermally conductive, and laminated between copper foil and metal base.
Concept has aroused, where a lot of heat is generated it is required dissipate the heat, and at the same time force cooling cannot be employed since it create noise, vibration and energy requirement as well. Any other method of heat dissipation would make the cost higher and also difficult to employ because of space limitation.
Therefore in order to achieve this metal core structure is required to be provided. Therefore a thermally conductive and electrical insulator metal layer is provided in between to serve the purpose. Here Aluminum comes into picture which can withdraw heat from the system.
The circuit is etched over the copper foil by usual mechanism and the metal base allows the heat to dissipate and dielectric serve as insulator.
And all these properties make Aluminum PCB’s has been employed over range of fields eg. Light emitting diode, television, automobiles, air conditioning units, aerospace industry, medical equipments, telecommunication etc.
As far as the manufacturing process is concern it shears similarity with the normal PCB such as etching of copper coil, protection of aluminum board from etching.
Firstly such PCBs were used in integrated circuits. Recent years the use of Aluminum PCB because of its advantages has been spread in range of areas. Therefore, it is important to give the explanation regarding its properties and unique features so that its use can be emphasized in the years to come in range of fields. Now they are being used at a very large scale due to which it is necessary for us to have an idea of Aluminum PCBs.
- a) Structure: - The aluminum PCB has lamellar structure. Four layers are sandwiched in this structure viz. Copper foil layer, dielectric layer, Aluminum base, and Aluminum membrane.
The peel-off strength of the copper coil is required to be improved, therefore before putting into the structure it is chemically oxidized and then plated with zinc or brass. Copper is used to provide the conducting path which is laminated on the substrate material.
Second comes to the dielectric layer, which is usually thermally conductive with very low thermal resistance, which is the core technology of aluminum PCB’s. It has the ability to sustain the mechanical and thermal stresses.
Aluminum base layer is essentially a aluminum substrate. It should have high thermal conductivity and suitable for mechanical manufacturing processes.
Aluminum membrane gives protection from etching agent. An aluminum design also has better mechanical stability and lower thermal expansion coefficient compare to other materials.
A thin dielectric layer which is essentially electric insulator but thermally conductive is laminated between copper foil and metal base. The copper foil is etched into the circuit pattern and metal base withdraws heat.
The manufacturing process certainly has some difficulties. First one is with the copper etching. In Aluminum PCB it is relatively thicker. The etching is required to be controlled during manufacturing. Related to thick copper foil there is a difficulty of solder mask printing. It actually distorts the etched image.
The manufacturing involve drilling, molding etc, this all can change electrical and thermal properties.
Main purpose of all PCB’s is almost same, provide heat dissipation solutions for the applications involving high temperature. Based on the purpose what it is actually going serve, and type of construction an aluminum PCB has like the type of material, dielectric layer etc. PCB’s have three categories
- Universal Aluminum PCB
- High thermal conductive PCB
- High frequency and Microwave Aluminum PCB
All the benefits should give in comparative view with FR4 PCB. Here some benefits are enlisted below
- It has superior characteristics of heat dissipation.
- The dielectric used are has higher thermally conductive compare to the conventional adhesive, and with less thickness.
- Size of PCB reduces considerably.
- Thermal transfer is more beneficial compare to the conventional one in rigid PCB.
- Aluminum also has low cost which makes it economical in most of the applications.
- Non-toxic nature of aluminum makes it environment friendly.
- Aluminum has more strength and durability than fiberglass and other ceramics. Also the weight of aluminum is very less.
- Thermal energy transfer is more efficient and reliable.
Although power converters and light emitting diode (s) are the largest users of these PCB. Automobile industries are also looking to get advantages of this system. There are other varieties also which are involved in various applications for example Flexible Aluminum PCBs, Hybrid Aluminum PCBs, Through-Hole Aluminum PCBs. Simple design and low thermal impedance of the dielectric out performs all other PCB insulators for high temperature operating systems.
These products basically used in high power switching applications. The aluminum design can operate under very high current. Automobile industries can go far ahead to utilize such technology. It is basically made up of high performance and low cost material. The heat dissipation mechanism makes it perfect to maintain the overall temperature of the system. Nowadays, Aluminum PCB is regarded as the solution to high power and tight tolerance applications. Some applications are enlisted below
Audio Device: I/o amplifier, balanced amplifier, power amplifier.
Power supply: Switching regulator, DC/AC converter
Communication electronic equipment: High frequency amplifier, transmitter circuit
Automobile: Electronic regulator, power supply control, ignition.
Computer: CPU board, floppy disk drive, power supply devices.
Power modules: Inverter, solid state relays, rectifier bridges.
Lamps and lighting: energy saving lamps,
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