Part One: What is Aluminum PCB?
Aluminum substrate is a type of metal-based copper-clad board with excellent heat dissipation functionality. Generally, a single-sided board is composed of three layers: the circuit layer (copper foil), the insulating layer, and the metal base layer. For high-end applications, there are also double-sided designs with a structure of circuit layer, insulating layer, aluminum base, insulating layer, and circuit layer. A small number of applications involve multi-layer boards, which can be created by bonding ordinary multi-layer boards with insulating layers and aluminum bases.
Single-sided aluminum substrate: It consists of a single layer of conductive pattern layer, insulating material, and aluminum plate (substrate).
Double-sided aluminum substrate: It involves two layers of conductive pattern layers, insulating material, and aluminum plate (substrate) stacked together.
Multi-layer printed aluminum circuit board: It’s a printed circuit board made by laminating and bonding three or more layers of conductive pattern layers, insulating material, and aluminum plate (substrate) together.
Divided by surface treatment methods:
Gold-plated board (Chemical thin gold, Chemical thick gold, Selective gold plating)
Part Two: Aluminum Substrate Working Principle
Power devices are surface-mounted on the circuit layer. The heat generated by the devices during operation is rapidly conducted through the insulating layer to the metal base layer, which then dissipates the heat, achieving heat dissipation for the devices.
Compared to traditional FR-4, aluminum substrates can minimize thermal resistance, making them excellent conductors of heat. Compared to thick-film ceramic circuits, they also possess superior mechanical properties.
Additionally, aluminum substrates have the following unique advantages:
- Compliance with RoHs requirements
- Better adaptability to SMT processes
- Effective handling of thermal diffusion in circuit design to reduce module operating temperature, extend lifespan, enhance power density and reliability
- Reduction in assembly of heat sinks and other hardware, including thermal interface materials, resulting in smaller product volume and lower hardware and assembly costs, and optimal combination of power and control circuits
- Replacement of fragile ceramic substrates for improved mechanical durability
Part Three: Composition of Aluminum Substrates
1. Circuit Layer
The circuit layer (typically using electrolytic copper foil) is etched to form printed circuits, used for component assembly and connections. Compared to traditional FR-4, with the same thickness and line width, aluminum substrates can carry higher currents.
2. Insulating Layer
The insulating layer is a key technology in aluminum substrates, serving primarily for adhesion, insulation, and heat conduction. The insulating layer of aluminum substrates is the most significant thermal barrier in power module structures. Better thermal conductivity of the insulating layer facilitates the diffusion of heat generated during device operation, leading to lower operating temperatures, increased module power load, reduced size, extended lifespan, and higher power output.
3. Metal Base Layer
The choice of metal for the insulating metal base depends on comprehensive considerations of factors such as the metal base’s coefficient of thermal expansion, thermal conductivity, strength, hardness, weight, surface condition, and cost.
Part Four: Reasons for Choosing Aluminum Substrates
1. Heat Dissipation
Many double-sided and multi-layer boards have high density and power, making heat dissipation challenging. Conventional substrate materials like FR4 and CEM3 are poor conductors of heat and have inter-layer insulation, leading to inadequate heat dissipation. Aluminum substrates solve this heat dissipation issue.
2. Thermal Expansion
Thermal expansion and contraction are inherent to materials, and different substances have different coefficients of thermal expansion. Aluminum-based printed boards effectively address heat dissipation issues, easing the problem of different material thermal expansion on the board’s components, improving overall durability and reliability, especially in SMT (Surface Mount Technology) applications.
3. Dimensional Stability
Aluminum-based printed boards are notably more stable in terms of dimensions compared to insulated material printed boards. The dimensional change of aluminum-based printed boards or aluminum core boards, heated from 30°C to 140-150°C, is 2.5-3.0%.
4. Other Reasons
Aluminum-based printed boards have shielding effects, replace brittle ceramic substrates, are suitable for surface mounting technology, reduce the effective area of printed boards, replace components like heat sinks to enhance product heat resistance and physical properties, and decrease production costs and labor.
Part Five: Applications of Aluminum Substrates
1. Audio Equipment: Input/output amplifiers, balanced amplifiers, audio amplifiers, pre-amplifiers, power amplifiers, etc.
2. Power Equipment: Switching regulators, DC/AC converters, SW adjusters, etc.
3. Communication Electronic Equipment: High-frequency amplifiers, filter devices, transmission circuits, etc.
4. Office Automation Equipment: Electric motor drivers, etc.
5. Automotive: Electronic regulators, ignition systems, power controllers, etc.
6. Computers: CPU boards, floppy disk drives, power units, etc.
7. Power Modules: Inverters, solid-state relays, rectifier bridges, etc.
8. Lighting Fixtures: With the promotion of energy-saving lamps, aluminum-based substrates are widely used in LED lights.
Post time: Aug-09-2023
