Aluminum PCBs are one of the most popular metal core PCBs, which can be found in versatile applications. They have metal base and copper-clad laminates that offer excellent thermal conductivity and electric insulation. In this blog, we will discuss this critical PCB type in details, including its structure, manufacturing process, and applications. Keep reading to learn more.
What Is an Aluminum PCB?
An Aluminum PCB, also referred to as an Aluminum Base PCB, Aluminum Clad PCB, or IMS (Insulated Metal Substrate) PCB. It is a type of printed circuit board that uses an aluminum base layer instead of the traditional FR4 fiberglass material. It usually has a thick aluminum substrate, over which is a thermally conductive but electrically insulating dielectric layer upon which is disposed a copper layer used for circuit traces. The unique construction of aluminum circuit boards allows them to be very effective at heat dissipation, and therefore, they’re perfect for high power applications and other types of boards that generate a lot of heat, such as LED lighting systems, power supplies, and automotive electronics.
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)
Aluminum PCB Manufacturing Process: A Step-by-step Guide
Step 1: Design and Engineering
CAD software is used by Engineers to create PCB layouts which are then turned into Gerber files that contain complete circuit specifications.
Step 2: Base Material Selection
Choose appropriate aluminum alloys like 5052, 6061, or 7075 and clean the PCB surface very clean to eliminate the dirt and the oil so as to enlarge the bonding.
Step 3: Dielectric Layer Application
We then cover the aluminum surface with a layer of about 50 – 200 micrometers thick, the layer is thermally conductive, but electrically insulating.
Step 4: Copper Foil Lamination
High-quality copper foil is bonded to the dielectric layer at 150-180°C under controlled pressure.
Step 5: Imaging and Etching
The copper layer undergoes photoresist coating, UV exposure, and chemical etching to create the circuit pattern.
Step 6: Surface Protection
Circuits are then protected with a protective solder mask and components marked with a silkscreen printing.
Step 7: Mechanical Processing
The aluminum board undergoes precision drilling, hole plating, and panel separation into individual units.
Step 8: Quality Testing
All boards are tested by automatically operated inspection systems for electrical continuity, thermal resistance and dimensional accuracy.
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
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
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.
Benefits of Aluminum-Based Printed Circuit Boards
Metal core PCBs have a unique set of advantages compared to other base materials.
- Friendly to the environment
Aluminum is a recyclable, non-toxic metal. From the producer through to the end purchaser, using aluminum in PCBs 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
The aluminum material itself is very lightweight. It adds durability and strength to PCBs without adding additional weight.
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 thermal dissipation performance of aluminum PCBs 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 excel in thermal dissipation, they do not experience significant contraction or expansion issues. They are highly durable, reliable, and perform exceptionally well.
Aluminum PCB Applications
Here is a list of common 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: A Reliable Aluminum PCB Manufacturer
MOKO Technology is a trusted and innovative manufacturer specializing in high-quality aluminum PCBs. With years of experience and latest technology, we strive to constantly offer our customers durable, efficient and precisely manufactured PCBs that meet the most demanding specifications. Our aluminum core PCBs are designed to enhance thermal dissipation, improve performance, and extend the lifespan of electronic devices. No matter what industry you are in: LED, power converter, automotive or RF, we provide you with a solution that is customized to your needs. Don’t wait, get a quote now!
