Aluminum PCBs

Characteristics and Applications of Aluminum PCBs

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Aluminum PCBs are a type of metal-based copper-clad laminate known for their excellent heat dissipation properties. A typical single-sided aluminum PCB consists of three layers: the circuit layer (copper foil), the insulation layer, and the metal base layer. For high-end applications, double-sided designs are also available, featuring a structure of circuit layer, insulation layer, aluminum base, insulation layer, and another circuit layer. In rare cases, multilayer boards are used, combining standard multilayer boards with insulation layers and aluminum bases.

Advantages of Aluminum PCBs

  1. Eco-Friendly: Aluminum is non-toxic and recyclable. Its ease of assembly also contributes to energy savings. For PCB suppliers, using aluminum supports environmental sustainability.

  2. Heat Dissipation: High temperatures can severely damage electronic components, so using materials that aid in heat dissipation is prudent. Aluminum effectively transfers heat away from critical components, minimizing its detrimental impact on the circuit board.

  3. Enhanced Durability: Aluminum provides a level of strength and durability that ceramic or fiberglass substrates cannot. It serves as a robust base material, reducing the likelihood of accidental damage during manufacturing, handling, and everyday use.

  4. Lightweight: Despite its remarkable durability, aluminum is surprisingly lightweight. It adds strength and resilience without adding significant weight.

Applications of Aluminum PCBs

  1. LED Lighting: The primary application of aluminum PCBs is in LED lighting. LEDs generate significant heat during operation, and the excellent heat dissipation properties of aluminum PCBs ensure the stable functioning of LEDs, thereby enhancing the lifespan and reliability of the lighting fixtures.

  2. Automotive Electronics: With the increasing degree of automotive electrification, the number and density of electronic components in vehicles are rising. The lightweight nature, excellent thermal management, and electrical performance of aluminum PCBs make them an ideal choice for automotive electronics.

  3. Renewable Energy: Aluminum PCBs play a crucial role in renewable energy sectors like solar and wind power. For example, solar panels need to efficiently convert solar energy into electrical energy, and the superior heat dissipation of aluminum PCBs helps maintain the stable operation of solar cells.

  4. Power Electronics: In power electronic devices such as inverters and converters, the use of aluminum PCBs ensures stable operation under high power densities.

  5. Industrial Automation: In industrial automation control systems, the high reliability, stability, and excellent electrical performance of aluminum PCBs make them the preferred material for critical components.

Applications of Aluminum PCBs

Manufacturing Process of Aluminum PCBs

  1. Mechanical Processing:

    • Drilling: While aluminum PCBs can be drilled, any burrs on the edges of the holes are unacceptable as they can affect the withstand voltage test.
    • Milling the Outline: Milling the outline is challenging. Punching the outline requires high-quality molds, which is a critical aspect of aluminum PCB production.
    • Punching: After punching the outline, the edges must be very neat, free of any burrs, and the solder mask layer on the edges should remain intact. Punching involves intricate techniques such as using a blanking die, ensuring the board does not warp more than 0.5% after the process.

  2. Avoid Scratches on the Aluminum Base:

    • The aluminum base must remain untouched throughout the process to prevent discoloration or blackening due to chemical exposure or handling. Any damage to the aluminum base is unacceptable, as re-polishing is often not permitted by customers. Protective measures, like passivation or applying protective films before and after hot air leveling (HASL), are essential to prevent damage.

  3. High Voltage Testing:

    • Aluminum PCBs for communication power supplies require 100% high voltage testing. Customers may specify either DC or AC testing, with voltages typically around 1500V or 1600V for durations of 5 to 10 seconds. Any dirt, burrs on holes or edges, jagged lines, or damage to the insulating layer can cause fires, leakage, or breakdowns during these tests. Issues such as delamination or bubbling during high voltage testing are grounds for rejection.

Aluminum PCB Manufacturing Specifications

  1. Copper Foil Thickness:

    • Aluminum PCBs are often used for power devices with high power densities, so the copper foil is typically thicker. For copper foil thicknesses of 3oz or more, the etching process requires precise line width compensation in the engineering design to ensure that the etched line width remains within tolerance.

  2. Protection of the Aluminum Base:

    • During the PCB manufacturing process, the aluminum base must be protected with a protective film to prevent damage from chemical exposure, which can tarnish the surface. This protective film is prone to damage, requiring careful handling and placement of the boards in racks throughout the process.

  3. Milling Tools:

    • Milling tools used for fiberglass boards (FR-4) have lower hardness, whereas those for aluminum PCBs require higher hardness. The milling speed for fiberglass boards is relatively high, but it must be reduced by at least two-thirds when milling aluminum PCBs.

  4. Cooling During Milling:

    • For milling fiberglass boards, the machine’s built-in cooling system is typically sufficient. However, when milling aluminum PCBs, additional cooling, such as applying alcohol to the milling bit, is necessary to dissipate heat effectively.