What Is the Aluminium Layer of a PCB?

Aluminium is among the most important metals on earth. It’s used in various industries and applications, including aircraft parts, furniture, and sporting equipment. However, did you know it’s also used to create aluminium substrate PCBs – one of the most important components of modern electronics?

In this post, we’ll discuss the design, function, benefits, and drawbacks of a PCB aluminium substrate. 

Understanding the Aluminium Layer of a PCB – The Key Component of an Aluminium Substrate PCB

Traditional printed circuit boards generally employ fiberglass or a plastic substrate to power electronics, including:

• Computers
• Smartphones
• Industrial machinery
• Automobiles, etc.

In contrast, an aluminium substrate is one that replaces the non-metal substrate with a metal one or combines fiberglass and aluminium. Aluminium boards offer a unique list of benefits, which we’ll discuss in a separate section. 

However, their core function is to provide mechanical support and a conductive pathway for electrical conductions between multiple components while enhancing heat dissipation. In other words, they’re much more suitable for applications requiring superior thermal management. 

Structure of PCB Aluminium Substrate

Aluminium PCBs, or Aluminium-based copper-clad laminates (CCLs), closely resemble FR4 PCBs in their structure. These PCBs comprise a four-layered structure featuring:

• An aluminium base layer
• A copper foil layer 
• An aluminium base membrane
• A dielectric layer 

The foil layer in Aluminium PCBs made from copper is notably thicker, ranging from 1oz to 10oz, providing a higher capacity to carry current. The dielectric layer, with a thickness between 50μm and 200μm, conducts heat, making it well-suited for thermal applications.

The PCB’s third layer comprises the aluminium substrate, enabling high thermal conductivity. This feature enhances the PCB’s ability to dissipate heat effectively.

Finally, the base membrane or fourth layer serves a protective function by safeguarding the aluminium surface against scraping and undesired etching. This membrane comes in two types: one suitable for temperatures below 120 degrees and the other designed to withstand higher temperatures, up to 250 degrees (anti-high temperature).

How Aluminium Substrate PCBs Are Manufactured

Manufacturers create Aluminium PCBs by applying a layer of dielectric material onto an aluminium sheet. They then add a thin layer of copper to form the circuit and create a circuit pattern using a photosensitive resist and etching to remove excess copper. Finally, they apply a solder mask to protect the circuit and add labels through silkscreen printing. 

Types of Aluminium Substrate PCBs

Different types of aluminium PCBs are designed to cater to specific complexity and thermal management requirements. The simplest among them is the one-layer aluminium PCB with a single component mounting side. In this configuration, the circuit is directly etched onto the copper layer of the aluminium laminate board. As electronic components generate heat, they transfer from them to the copper layer to the polypropylene (PP) layer, ultimately dissipating into the aluminium layer.

Moving to a slightly more complex design, the two-layer aluminium PCB with a single component mounting side features two copper and corresponding PP layers. This arrangement enhances the PCB’s capacity for more intricate circuits. Heat dissipation follows a sequential path, moving from the components to the first copper layer and then to the first PP layer. Subsequently, it travels to the second copper layer, then to the second PP layer, and finally reaches the aluminium layer.

When a single-sided PCB falls short of accommodating the necessary circuitry, the two-layer aluminium PCB with dual component-mounting sides becomes relevant. Like a two-layer FR4 PCB, this design introduces resin, filling the space between plated through-holes (PTHs). The heat transfer process in this configuration occurs stepwise, moving from the components to the copper layer, then to the PP layer, and ultimately dissipating into the aluminium layer.

The four-layer aluminium PCB with dual component-mounting sides emerges as a solution for applications demanding even greater complexity. This design provides increased circuit density, featuring two copper layers and corresponding PP layers. However, its thermal conductivity is lower compared to single-layer and two-layer counterparts. The heat dissipates from the components to the outer copper layer, then to the first PP layer, followed by the second copper layer, the second PP layer, and finally into the aluminium layer.

The Most Common Applications of an Aluminium Substrate PCB

A PCB aluminium substrate is commonly used in:

1. LED Lighting

Aluminium substrate PCBs are most commonly used in LED lighting. Their superior thermal conductivity ensures effective heat dissipation to avoid failure and improve the durability of the lighting system. In other words, aluminium is why modern LEDs last much longer than traditional lighting. 

• Power Supplies

Electronics manufacturers use aluminium substrate PCBs in invertors, generators, and power converters. These applications generate a lot of heat. As a result, the aluminium layers in the PCB prevent overheating to ensure stable operation. 

• Automotive Systems

Aluminium substrate PCBs are wildly popular in the automotive industry. They’re used to reduce the weight of electronic systems in vehicles and equipment. Their flexibility also allows manufacturers to improve space efficiency and add more electronic components. 

• Consumer Electronics

Aluminium substrate PCBs are now commonly found in modern consumer electronics, especially high-end variants. Examples include computers, tablets, HiFi equipment, gaming consoles, etc. Manu manufacturers have even used aluminium to shrink their products to improve portability and overall handling. 

• Renewable Energy Systems

Finally, aluminium substrate PCBs are used in renewable energy system components, including wind turbine controls and energy storage systems. These expensive systems mandate the use of top-shelf circuitry. Hence, manufacturers spare no expense to ensure optimal efficiency with minimum failures. 

• Communication Devices

Aluminium substrate PCBs are crucial in communication devices, including smartphones, routers, and network equipment. The thermal efficiency of aluminium substrates ensures that these devices can handle the heat generated during prolonged operation, contributing to their reliability and longevity.

• Aerospace Electronics 

Aluminium is incredibly light. Hence, it’s the go-to material for aircraft construction and electronic system design. Manufacturers use aluminium substrate PCBs to connect avionics systems, communication devices, and navigation equipment to maximize performance. 

• Solar Panels

Aluminium substrate PCBs are used in solar inverters and charge controllers. These PCBs integrate various electronic components, ensuring efficient solar power conversion from DC to AC to operate standard electronic equipment in homes and other buildings.

• Medical Devices

The healthcare industry is among the latest industries to adopt aluminium substrate PCBs. Today, these hdi printed circuit boards are used in patient monitoring systems, imaging devices, and diagnostic equipment, to name a few. Equipment reliability is one of the most crucial performance metrics in healthcare environments. Hence, the industry has switched to these variants to minimize failure during crucial procedures. 

1. Industrial Controls

Aluminium substrate PCBs are also used in industrial control systems, where robust performance is essential in challenging environments. These PCBs improve the reliability of control panels, PLCs (Programmable Logic Controllers), and other industrial automation equipment, improving the overall plant efficiency. 

Key Benefits and Drawbacks of PCBs with Aluminium Layers

Below are the key advantages and disadvantages of PCB aluminium substrate:

Benefits

1. Low Aluminium Sourcing Cost

Aluminium is among the most abundant metals found on earth. Therefore, it’s more cost-effective to mine and refine. As a result, many manufacturers actively use it instead of copper and other suitable metals for PCB substrates. 

• Recyclable

Unlike many metals, aluminium is non-toxic. More importantly, it’s recyclable, meaning manufacturers can extract aluminium from waste and use it again to make aluminium substrate PCBs. 

• Heat Dissipation

The key advantage of using PCB aluminium substrates is improved thermal management. Electronics are incredibly vulnerable to damage and failure in high temperatures. Hence, aluminium offers a viable heat transfer solution, making it useful for applications like LED lighting and industrial machinery. 

• Enhanced Durability

Aluminium is stronger and more durable than ceramic or fiberglass. As a result, many modern manufacturers use it to make higher-quality printed circuit boards less susceptible to accidental breakage at any stage of their lifecycle, from manufacturing to distribution and everyday use. 

• Lightweight

Industrial machinery, aircraft, and other electronic equipment can be incredibly heavy, weighing thousands of pounds. Hence, using aluminium instead of fiberglass or copper is a smart way to reduce the weight significantly without compromising strength and thermal resilience. 

Drawbacks

1. Higher Manufacturing Costs

Although aluminium is relatively easy to procure, the manufacturing process of aluminium substrate PCBs is incredibly complex and expensive compared to traditional PCBs. Therefore, these variants typically cost more. 

• Limited Material Compatibility

Ensuring the aluminium base works well with other PCB materials can be challenging. The problem lies in differences in how materials expand when heated, which might lead to troubles like delamination (layers coming apart) or cracking.

Conclusion

Due to their superior heat dissipation capabilities, aluminium PCBs excels in applications like high-power LED lighting and automotive electronics. Despite these benefits, they come with higher costs, limited layer options, and potential challenges related to the differing thermal expansion of materials, which may result in issues like delamination or cracking. Manufacturers strive to balance their thermal advantages and these considerations when opting for aluminium substrate PCBs and rigid flex pcb.

Also read: How Photoelectric Effect Impacts p-n Junctions