How Well Do You Know About Aluminum PCB

Introduction to Aluminum PCB

Aluminum PCB is a Printed Circuit Board that contains a thin layer of conductive electrical insulator material. They are also known as Aluminum base, Aluminum clad, IMS (Insulated Metal Substrate), MCPCB (Metal Clad Printed Circuit Board), Thermally Conductive PCBs, etc. Aluminum PCBs were developed in the 1970s, soon after which their demand increased dramatically. The first application was their use in Amplification Hybrid Circuits. Currently, they are being used at a much larger scale and it is important for us to know about Aluminum PCB and their importance in the community.

Every flexible and unbending printed circuit board (PCB) design is different. It is 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 operative in many applications. Aluminum PCBs consist of a copper-clad laminate that delivers high performance, metal-based, including excellent electrical insulation and thermal conductivity.

Specs and Tolerances

Outerlayer Trace / Space.003″ / .004″
Innerlayer Trace / Space.003″ / .004″
Minimum Drilled Hole.0059″
Standard Drilled Hole.010″
Drill Aspect Ratio15:1
Minimum Pad Size.008″
Minimum Feature to Edge.010″
Minimum Core Thickness.002″
Controlled Depth DrillingYES
Sequential LaminationYES

How is Aluminum PCB Made?

Aluminum printed circuit boards consist of metal-based seals covered by copper foil circuit layers. They are made of alloy plates that are a combination of magnesium, aluminum and silumin (Al-Mg-Si). Aluminum PCBs deliver good thermal potential, electrical insulation, and high machining performance, and they are different from other PCBs in numerous important ways.

Base layer

This base consists of an aluminum alloy substrate. The use of aluminum makes this type of PCB a brilliant choice for through-hole technology that will be discussed later in this article.

Thermal insulation layers

This is a critically important module of the PCB. It contains a ceramic polymer that has excellent thermal resistance, viscoelastic properties and defends the PCB against mechanical and thermal stresses.

Circuit layer

This layer contains the copper foil mentioned previously in this article. Mostly, PCB manufacturers use copper foils extending from one to ten 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 amplified heat. PCBs with improved thermal resistance extend the life of your finished product. A skilled manufacturer will provide you with heat mitigation, superior protection and part reliability.

The Evolution of Printed-circuit boards

PCBs are relatives to the electrical connection systems introduced in the 1850s, in which metal strips or rods connected large electric components installed on wood bases. Over time, wires connected to the screw terminals replaced the metal strips and metal chassis used in place of the wooden bases.

While these were definitely 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 wanted 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

Structure of Aluminum PCBs

Aluminum PCBs are actually quite similar to FR4 PCBs. The basic structure of Aluminum PCBs is four layers. It consists of a dielectric layer, copper foil, an aluminum base layer, and an aluminum base membrane.

• Copper Foil Layer

The used copper layer is relatively thicker than normal CCLs (1oz to 10oz). A thicker layer of copper means a larger current carrying capacity.

• Dielectric Layer

The Dielectric layer is a thermally conductive layer and is around 50micrometer to 200micrometer thick. It has a low thermal resistance and it is suitable for its application.

• Aluminum Base

This third layer is the aluminum base that is made up of aluminum substrate. It has high thermal conductivity. Aluminum Base Membrane Layer

The aluminum base membrane is selective. It plays a defensive role by keeping the aluminum exterior safe from unwanted etching and scraping. It is of two types i.e. around 250 degrees or lower than 120 degrees (anti-high temperature)

Types of Aluminum PCBs 

LED and Power converter companies are so far the largest users of aluminum PCBs. However, radio frequency (RF) and automotive companies also make use of this type of printed circuit board. Single-layer construction is more common because it is simple, but there are other configurations offered.

Flexible Aluminum PCBs

Flexible dielectrics are a fresh development in Insulated Metal Substrate (IMS) materials. The materials feature ceramic fillers and polyimide resin and provide greater electrical insulation, thermal conductivity, and flexibility. When used with flexible aluminum materials (such as 5754), the PCB can be angled and formed to eliminate costly items such as cables, fixtures, and connectors. Though the materials are flexible but designed to bend and stay in place forever. They’re not meant for applications that require the materials to flex frequently.

Hybrid Aluminum PCBs

With the hybrid aluminum PCB, a non-thermal material is managed and thermally fused to the aluminum base material. Normally, a two-layer or four-layer circuit board made from straight FR-4 is used. Fusing this layer to the aluminum base with thermal dielectrics dissolves the heat, acts as a heat shield and increases inflexibility. Other benefits of a hybrid aluminum PCB include:

Better thermal performance compared to standard FR-4 products

Less expensive construction compared to PCBs made of all thermally conductive materials.

Eliminates related assembly steps and costly heat sinks.

Useful enough to be used in RF applications, where lost features can be enhanced by a surface laver of PTFE

Better thermal act compared to standard FR-4 products

Through-Hole Aluminum PCBs

In highly complex structures, a single layer of aluminum can form the central core of a many-sided thermal structure. In through-hole 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.

Manufacturing Difficulties of Aluminum PCBs

The manufacturing process for nearly all-aluminum PCBs is basically the same. Here we will discuss the main manufacturing processes, the problems and their solutions.

1: Copper Etching

pcb copper etching

The copper foil used in Aluminum PCBs is moderately thicker. If the copper foil is over 3-oz however, the etching requires width settlement. If it is not according to the demand of the design, the trace width will be out of tolerance after etching. That is why the trace width compensation should be designed accurately. The etching factors need to be controlled during the manufacturing process.

2: Solder Mask Printing

solder mask printing

Due to thick copper foil, there is a difficulty in solder mask printing of aluminum PCB. This is because; if the trace copper is too thick then the image etched will have a large difference between base board and trace surface and solder mask printing will be quite difficult. Therefore, the two-time solder mask printing is preferably used. The solder mask oil used should be of decent quality and in some cases, the resin filling is done first and then solder mask

3: Mechanical Manufacturing:

The mechanical manufacturing process involves molding, mechanical drilling, and v-scoring, etc. Which is left on internal via. This tends to decrease electrical strength. Therefore, the professional milling cutter and electric milling cutter should be used for low-volume manufacturing of products. The drilling parameters should be adjusted to prevent burr from generating. This will help your mechanical manufacturing.

Classification of Aluminum PCBs

Aluminum PCBs are essentially divided into three categories.

1. Universal Aluminum PCB: dielectric layer used here is made up of epoxy glass fiber pre-preg.

2. High-frequency Aluminum PCB: the dielectric layer is composed of polyolefin or polyimide resin glass fiber pre-preg.

3. High Thermal-Conductive Aluminum PCB: the dielectric laver is made up of epoxy resin. The resin used must have a high thermal conductivity

Benefits of Aluminum-Based Printed Circuit Boards

Metal core PCBs have a unique set of advantages compared to other base materials.

Less expensive

Aluminum is native to a variety of climates so it’s easy to mine & refine. This makes it significantly less costly to mine and refine than other metals. By extension, the manufacturing costs related to 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 recyclable, non-toxic metal. From the producer through to the end purchaser, using aluminum in PBCs contributes to a healthy planet.

Better heat transfer

High temperatures are the reason for heavy damage to electronics. Aluminum conducts and transfers heat away from dangerous parts to minimalize damage to the printed circuit board.

Very durable

Aluminum is tougher and more durable than base materials like fiberglass and ceramic. It is very well-made and reduces accidental breakages that can occur throughout the manufacturing process, and during handling and everyday use.

Lightweight

Because of its durability, aluminum is very lightweight. It adds resilience and strength to PCBs without adding additional weight.

Even though lighting projects and power converters are the largest users of metal-based PCB’S, there are many different users. It may benefit from the aluminum-core PCB material. Every Aluminum core PCB supplier should help their customers assess their needs for insulation and thermal control.  Aluminum Core PCB’s are classically used with Black or White solder mask.

Performance of Aluminum PCBs

Dimensional Stability

Aluminum PCBs display dimensional stability & steady size. For example, when they are heated from 30-140 degrees, their dimensions only had a change by 2.5%-3.0%.

Thermal Dissipation

The performance of aluminum PCBs while dissolving heat is quite well as compared to ordinary FR4 PCBs. For example, a FR4 PCB that is 1.5mm thick will have a thermal resistance of 20-22 degrees per watt while an aluminum PCB 1.5mm thick will have a thermal resistance of approximately 1-2 degrees per watt.

Thermal Expansion

Every substance has its own coefficient of thermal expansion. The CTE of copper(18ppm/C) and aluminum (22ppm/C) is fairly close. Since aluminum PCBs work well in terms of Thermal dissipation, they do not have severe contraction or development issues. They work exceptionally and are durable plus reliable.

Aluminum PCB Applications

Aluminum back PCBs are perfect for situations where thermal heat dissipation requirements are very high.

PCBs clad with aluminum is more operative at directing thermal energy away from printed circuit board components, therefore, it provides better temperature management for PCB designs. Aluminum-backed designs can be as much as 10 times more effective 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.

1. 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 of aluminum designs allow the density of LEDs in the PCB structure to be higher and for the mounted LEDs to operate at higher currents while staying within specified temperature tolerances.

2. Aluminum-backed PCBs also allow reduced safety margins with power LEDs compared to conventional PCB design.

The lower operating temperature of the LEDs in design means the LEDs can operate for longer periods of time before they fail.

3. Other applications for aluminum PCBs include power supplies, high-current circuitry, motor controllers and automotive applications.

Aluminum core PCB materials are very operative in thermal heat dissipation applications that include 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 heat sinking and forced air, which eventually lowers the design cost. Just about any design that can be made better by improving thermal conduction and temperature control is a candidate for an aluminum-backed PCB.

Aluminum base PCBs consist of aluminum backing whereas traditional PCBs use a fiberglass substrate (FR4 is standard), standard circuit layers and thermally conductive dielectric 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 dependably increase shelf life and durability of design through associated reductions in failure rates and temperature control.

Aluminum designs also deliver low thermal expansion levels than other PBS designs and better mechanical stability.

4. Complete list of aluminum core PCB applications:

• Medical: Operating room lighting, Surgical lighting tools, High power scanning technology. and Power converters.

• Consumer: Street lighting, Traffic control lighting, Interior building lights, Landscape lighting, and Camping gear.

• Power Modules: Including solid-state relays, converters, bridges and power rectifiers.

• Telecommunications: Including high-frequency amplifiers and filtering appliances.

• Power Supply: Such as switching regulators and DC/AC converters.

• Automotive: Including power controllers. lighting, and electronic regulators.

• Computers: Such as CPU boards, floppy drives and power devices.

• Audio Devices: such as input and output amplifiers and power amplifiers+Office Automation, such as electric motors and drives.

MOKO Technology delivers hi-tech printed circuit board technology and is a leading manufacturer of aluminum core PCBs. We use front-line technology to provide well-manufactured PCBs that meet our customer’s rigorous specifications. Get to know more about us if you’re looking for aluminum PCB!

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