The Working Principle of Aluminum Substrate

1. Working Principle of Aluminum Substrate

Surface-mounted power devices are mounted on the circuit layer, and the heat generated during device operation is quickly conducted to the metal substrate through the insulation layer, and then the heat is dissipated by the metal substrate, thereby achieving heat dissipation for the device.

Compared with traditional FR-4, aluminum substrates can minimize thermal resistance, making them have excellent thermal conductivity. Compared with thick film ceramic circuits, they also have extremely good mechanical properties.

In addition, aluminum substrates have the following unique advantages:

a. Compliance with RoHS requirements.

b. More suitable for SMT processes.

c. Reduction in assembly of heat sinks and other hardware (including thermal interface materials), reducing product size, hardware, and assembly costs; optimizing the combination of power circuits and control circuits.

d. Replacing fragile ceramic substrates to obtain better mechanical durability.

2. Composition of Aluminum Substrate

a. Circuit Layer

The circuit layer (generally using electrolytic copper foil) is etched to form a printed circuit, used for device assembly and connection. Compared with traditional FR-4, with the same thickness and line width, aluminum substrates can carry higher currents.

b. Insulation Layer

The insulation layer is the core technology of aluminum substrates, mainly serving bonding, insulation, and thermal conduction functions. The insulation layer of aluminum substrates is the largest thermal barrier in power module structures. The better the thermal conductivity of the insulation layer, the more conducive it is to the diffusion of heat generated during device operation, which is beneficial for reducing the operating temperature of the device, thereby achieving goals such as increasing module power load, reducing volume, extending life, and improving power output.

c. Metal Substrate

The choice of metal for the insulated metal substrate depends on factors such as the coefficient of thermal expansion, thermal conductivity, strength, hardness, weight, surface condition, and cost of the metal substrate.

3. Performance of Aluminum Substrate

a. Heat Dissipation

Currently, many double-sided and multilayer boards have high density and power, making heat dissipation difficult. Conventional printed board substrates such as FR4 and CEM3 are poor conductors of heat and have interlayer insulation, making it difficult for heat to dissipate. Local heating of electronic equipment cannot be ruled out, leading to high-temperature failure of electronic components, while aluminum substrates can solve this heat dissipation problem.

b. Thermal Expansion

Thermal expansion and contraction are common properties of materials, and the thermal expansion coefficients of different materials are different. Aluminum-based printed circuit boards can effectively solve heat dissipation problems, thereby alleviating the thermal expansion and contraction problems of different materials of components on the printed circuit board, improving the durability and reliability of the entire machine and electronic equipment, especially solving the thermal expansion and contraction problems of SMT (Surface Mount Technology).

c. Dimensional Stability

Obviously, the size of aluminum-based printed circuit boards is much more stable than that of insulating material-based printed circuit boards. Aluminum-based printed circuit boards and aluminum-core boards have a size change of 2.5-3.0% when heated from 30°C to 140-150°C.

d. Other Reasons

Aluminum-based printed circuit boards have shielding effects; they replace brittle ceramic substrates; they confidently use surface mount technology; they reduce the truly effective Warea of printed boards; they replace heat sinks and other components, improve product heat resistance and physical properties; they reduce production costs and labor.