Every rigid and flexible printed circuit board (PCB) design is different, customized to meet the board’s purpose. The same is true for the PCB base material — fiberglass is a popular base material, but aluminum-based PCBs are also very effective in many applications. Aluminum PCBs consist of a metal-based, copper-clad laminate that delivers high performance, including excellent thermal conductivity and electrical insulation.
Millennium Circuits Limited, located in a Harrisburg, Pennsylvania, is a leading provider of a wide range of printed circuit boards, including metal-base or metal core aluminum PCB’s for the automotive, aerospace, consumer products and medical industries. Here’s our take on the uses and benefits of aluminum-based PCBs. Get Pricing and Lead Time
An aluminum PCB is a metal-based board and its structure is divided into three layers:
Aluminum printed circuit boards are also known as metal base PCBs, and are comprised of metal-based laminates covered by copper foil circuit layers. They are made of alloy plates that are a combination of aluminum, magnesium and silumin (Al-Mg-Si). Aluminum PCBs deliver excellent electrical insulation, good thermal potential, and high machining performance, and they differ from other PCBs in several important ways.
The base layer consists of an aluminum alloy substrate. The use of aluminum makes this type of PCB an excellent choice for through-hole technology, discussed later in this article.
The thermal insulation layer is a critically important component of the PCB. It contains a ceramic polymer that has excellent viscoelastic properties, great thermal resistance, and defends the PCB against thermal and mechanical stresses.
The circuit layer contains the copper foil mentioned previously. Generally, PCB manufacturers use copper foils ranging from one to 10 ounces.
The dielectric layer of insulation absorbs heat as current flows through the circuits. This is transferred it to the aluminum layer, where the heat is dispersed.
Achieving the highest light output possible results in increased heat. PCBs with improved thermal resistance extend the life of your finished product. A qualified manufacturer will provide you with superior protection, heat mitigation and part reliability. At MCL, we hold ourselves to the exceptionally high standards your projects require.
Types of Aluminum PCBs
Power Converter and LED companies are by far the largest users of aluminum PCBs. However, automotive and radio frequency (RF) companies also make use of this type of printed circuit board. Single-layer construction is popular because it is simple, but there are other configurations available. Get Pricing and Lead Time
Flexible Aluminum. Flexible dielectrics are a recent development in Insulated Metal Substrate (IMS) materials. The materials feature polyimide resin and ceramic fillers, and provide superior electrical insulation, flexibility, and thermal conductivity. When used with flexible aluminum materials (such as 5754), the PCB can be shaped and angled to eliminate costly items such as fixtures, cables and connectors. Beware, though: the materials are flexible but designed to bend and stay in place permanently. They’re not meant for applications that require the materials to flex regularly.
Hybrid Aluminum. With this option, a non-thermal material is processed and then thermally fused to the aluminum base material. Most commonly, a two-layer or four-layer circuit board made from conventional FR-4 is used. Fusing this layer to the aluminum base with thermal dielectrics dissipates heat, increases rigidity and acts as a heat shield. Other benefits of a hybrid aluminum PCB include:
- Less expensive construction compared to PCBs made of all thermally conductive materials
- Better thermal performance compared to standard FR-4 products
- Eliminates costly heat sinks and related assembly steps
- Versatile enough to be used in RF applications, where loss characteristics can be enhanced by a surface layer of PTFE
Through-Hole Aluminum. In highly complex constructions, a single layer of aluminum can form the central core of a multilayered thermal construction. With this type of PCB, the aluminum is pre-drilled and the hole is back-filled with dielectric before the lamination process. Next, thermal materials (or sub-assemblies) are laminated to both sides of the aluminum with thermal bonding materials. After lamination, the assembly is thru-drilled in a manner similar to a multilayer PCB, and the plated through-holes are then passed through the clearances in the aluminum to provide electrical insulation.
Benefits of Aluminum-Based Printed Circuit Boards
Less expensive. Aluminum is indigenous to a variety of climates, so it’s easy to mine and refine. That makes it significantly less expensive to mine and refine than other metals. By extension, the manufacturing costs associated with products using aluminum PCBs are also less expensive. Aluminum PCBs are also a less expensive alternative to heat sinks.
Friendly to the environment. Aluminum is a non-toxic, recyclable metal. From the manufacturer through to the end consumer, using aluminum in PBCs contributes to a healthy planet.
Better heat transfer. High temperatures are the cause of heavy damage to electronics. Aluminum conducts and transfers heat away from critical parts to minimize damage to the printed circuit board.
Very durable. Aluminum is stronger and more durable than base materials like ceramic and fiberglass. It is very sturdy, and reduces accidental breakages that can occur throughout the manufacturing process, and during handling and everyday use.
Lightweight: Considering its durability, aluminum is very lightweight. It adds strength and resilience to PCBs without adding additional weight.
We like our clients to be as informed as they can about the different types of products we offer at MCL. Even though power converters and lighting projects are the largest users of metal-based PCB’S, there are many different uses. LED PCB manufacturers make up the majority of metal-based circuit boards, , it may benefit from the advantages of aluminum-core PCB material. Every Aluminum core PCB supplier should help their customers assess their needs for thermal control and insulation. Aluminum Core PCB’s are typically used with White or Black solder mask and MCL has a specific White mask for LED applications.
Basics of Heat Transfer
At a basic level, a discussion about heat transfer includes two topics: temperature and heat flow. Temperature represents the level of thermal energy that’s available, while heat flow represents thermal energy movement from one place to another.
Microscopically, thermal energy is directly related to a molecule’s kinetic energy. The greater the temperature of a material, the greater the thermal agitation of its molecules. It’s normal for areas that contain a lot of kinetic energy to pass it along to areas with less kinetic energy.
There are some material properties that effectively modulate heat that’s transferred between two areas at different temperatures. These include thermal conductivities, material densities, fluid velocities and fluid viscosities. Together, these properties make resolving many heat transfer problems pretty complicated.
The Mechanisms of Heat Transfer
Heat transfer mechanisms can be grouped into three broad categories:
Conduction. Areas that have more molecular kinetic energy will send their thermal energy to areas that have less molecular energy. This occurs through a direct collision of molecules, known as conduction. In metals, some of the energy transported from one area to another is also carried by conduction-band electrons.
Convection. When heat is generated in an electronic device, it’s transported via conduction to an area
where it is then transferred to a fluid. That process is convection, and the fluid can take the form of a gas such as air or conventional water.
Radiation. All materials give off thermal energy in amounts that are determined by temperature. When the temperatures are uniform, the radiation flux is in in equilibrium between objects, and there is no exchange of thermal energy. This balance changes when temperatures vary and thermal energy is transported from areas of higher temperatures to those of lower temperature.
The Evolution of Printed Circuit Boards
PCBs are kin to the electrical connection systems introduced in the 1850s, in which metal strips or rods connected large electric components installed on wooden bases. Over time, wires connected to screw terminals replaced the metal strips and metal chassis used in place of the wooden bases. While these were certainly important technological advances, the systems were too large to meet the growing need for smaller, more compact designs demanded by products that used circuit boards.
This demand inspired Charles Ducas of the United States to develop a stencil with conductive inks that could “print” electrical paths directly on insulated surfaces. He submitted a patent on the process in 1925, giving birth to the phrases “printed wiring” and “printed circuit.”
1943 saw the development and patenting of a method to etch conductive patterns (circuits) onto a layer of copper foil, which was fused to a non-conductive base material reinforced with glass. The technique, developed by Paul Eisler of the United Kingdom, gained widespread popularity in the 1950s with the advent of transistors for commercial use. Until that time, vacuum tubes and other components were so large that only traditional mounting and wiring methods were required.
Transistors changed everything, however — components shrunk in size considerably, and manufacturers sought to reduce the overall size of their electronic packages by switching to PCBs.
The introduction of through-hole technology and its use in multi-layer PCBs in the 1960s resulted in increased component density and tightly spaced electrical paths, and started a new era in PCB design. In the 1970s, integrated circuit chips become foundational to printed circuit board design.
Aluminum PCB Applications
Aluminum back PCBs are ideal for situations when thermal heat dissipation requirements very high. PCBs clad with aluminum are more effective at directing thermal energy away from printed circuit board components therefore provide better temperature management for PCB designs. Aluminum-backed designs can be as much as ten times more efficient than fiberglass-backed designs when it comes to removing thermal energy from circuit board components. The much higher thermal dissipation rate allows higher power and higher density designs to be implemented.
Aluminum-backed PCBs are used more than ever for applications of high power/high thermal heat dissipation. Although they were originally designed for high power switching supply applications, aluminum-backed printed circuit boards have gained popularity in LED applications, including traffic lights, automotive lighting and general lighting. The use aluminum designs allow the density of LEDs in the PCB design to be higher and for the mounted LEDs to operate at higher currents while staying within specified temperature tolerances.
Aluminum-backed PCBs also allow for decreased safety margins with power LEDs compared to conventional PCB design. Lower operating temperature of the LEDs in a design means the LEDs can operate for longer periods of time before they fail.
Other applications for aluminum PCBs include power supplies, high-current circuitry, motor controllers and automotive applications. Aluminum core PCB materials are very effective in thermal heat dissipation applications that involve high-power surface mount integrated circuits. Because of the high level of thermal dissipation associated with aluminum-backed PCBs, circuit board designs can be simplified. Aluminum PCBs eliminate forced air and heat sinking, which ultimately lowers the design cost. Just about any design than can be made better by improving thermal conduction and temperature control is a candidate for an aluminum-backed PCB.
While traditional PCBs use a fiberglass substrate (FR4 is standard), aluminum base PCBs consist of an aluminum backing, thermally conductive dielectric layers and standard circuit layers (a thin PCB bonded to the aluminum backing). As a result, the circuit layers can be just as complex as the layers mounted on traditional fiber PCBs.
Aluminum-backed PCBs can reliably increase durability and shelf life of a design through temperature control and associated reductions in failure rates. Aluminum designs also deliver better mechanical stability and low thermal expansion levels than other PBS designs.
Here’s a more complete list of aluminum core PCB applications:
- Telecommunications, including high-frequency amplifiers and filtering appliances
- Power Supply, such as switching regulators and DC/AC converters
- Automotive, including electronic regulators, lighting and power controllers
- Computers, such as CPU boards, floppy drives and power devices
- Power Modules, including converters, solid-state relays, power rectifiers, and bridges
- Audio Devices, such as input and output amplifiers and power amplifiers
- Office Automation, such as electric motors and drives
- Consumer: Street lighting, Traffic control lighting, Interior building lights, Landscape lighting, and Camping gear.
- Medical: Operating room lighting, Surgical lighting tools, High power scanning technology, and Power converters.
Millennium Circuits Limited delivers state-of-the-art printed circuit board technology, and is a leading manufacturer of aluminum core PCBs. We use cutting-edge technology to provide precision-manufactured PCBs that meet our customer’s rigorous specifications. We produce nearly 250,000 square feet of PCBs every month, so we know printed circuit boards!