Basic Knowledge of Aluminum PCB

What is aluminum PCB

Aluminum PCB

Introduction to Aluminum PCB

Aluminum PCB is the most common circuit board among metal PCBs. The aluminum substrate is a metal-based copper clad laminate with good heat dissipation function. Generally, a single panel is composed of a three-layer structure: a circuit layer (copper foil), an insulating layer, and a metal base layer. Because the aluminum PCB has a heat dissipation layer, it has a good heat dissipation function, which can effectively reduce the component’s operating temperature and extend the service life of the product.

The working principle of aluminum PCB

Aluminum PCB

First, the surface mounts the power device on the circuit layer. The heat generated during the operation of the device will be quickly transferred to the metal base layer through the insulating layer. Then the metal base layer transfers the heat out to realize the heat dissipation of the device.

The structure of aluminum PCB

Copper foil layer: The copper layer used is thicker than standard copper-clad laminates. A thicker copper layer means greater current-carrying capacity.

Dielectric layer: The dielectric layer is a thermally conductive layer with a thickness of about 50μm to 200μm. It has low thermal resistance, so it is suitable for its application.

Aluminum substrate: The third layer is an aluminum substrate, which is made of aluminum substrate. It has a high thermal conductivity.

Aluminum-based film: Aluminum-based film is optional. It has a protective effect by protecting the aluminum surface from scratches and unnecessary corrosion.

 

Advantages of aluminum PCB

The advantages of aluminum PCB

Compared with traditional FR-4, aluminum PCB can minimize thermal resistance. Therefore, aluminum PCB has excellent thermal conductivity. Compared with thick-film ceramic circuits, its mechanical properties are excellent. In addition, aluminum PCB has the following unique advantages:

Heat dissipation

The heat dissipation capacity of aluminum PCB is much better than that of standard PCB.

Durability

Aluminum PCB provides higher strength and durability. Compared with PCBs based on ceramics and glass fibers.

Convenience

Aluminum PCB is lighter than standard PCB.

The assembly process of aluminum PCB is more manageable than standard PCB.

Environmental protection

Aluminum PCB is environmentally friendly. It is non-toxic and recyclable and will not cause any harmful effects on the environment.

Quality

Aluminum PCB meets RoHs requirements; it is more suitable for the SMT process.

The use of aluminum PCB can reduce the thermal expansion and shrinkage of PCB components.

Assembly cost

Aluminum PCB reduces the assembly of heat sinks and other hardware (including thermal interface materials); reduces product volume.

Aluminum PCB can reduce hardware and assembly costs; optimize the combination of power circuits and control circuits.

 

Types of aluminum PCB

Flexible aluminum PCB

Aluminum PCB

The flexible aluminum PCBde1 dielectric is the latest development of insulating metal substrate materials. The material features ceramic filler and polyimide resin and provides higher electrical insulation, thermal conductivity, and flexibility. When use it with flexible aluminum materials (such as 5754), we can tilte and shape the aluminum PCB to eliminate expensive items such as cables, fixtures, and connectors. Although these materials are flexible, we can bent and remain them in place permanently. They are not suitable for applications that require frequent bending of the material.

Mixed aluminum PCB

Aluminum PCB

Using hybrid aluminum PCBs, we can manage non-thermal materials and thermally fuse them to aluminum substrates. Generally, a two-layer or four-layer aluminum PCB made of straight FR-4 is used. Fusion of this layer and thermoelectric medium to the aluminum PCB substrate can dissolve heat, act as a heat shield and increase flexibility.

Other benefits of mixed aluminum PCB include:
  1. Compared with PCBs made of all thermally conductive materials, the hybrid aluminum PCB structure is cheaper.
  2. Mixed aluminum PCB eliminates related assembly steps and expensive heat sinks.
  3. We can use mixed aluminum PCB for RF applications. In these applications, PTFE surface laver can enhance the lost function
  4. Compared with standard FR-4 products, mixed aluminum PCB has better thermal performance

Through-Hole Aluminum PCB

Aluminum PCB
In highly complex structures, a single layer of aluminum can form the central core of a multi-faceted thermal structure. In a through-hole aluminum PCB, drilling the aluminum before the lamination process and then use a dielectric to backfill the hole. Next, laminating the thermally conductive material (or sub-assembly) to both sides of the aluminum PCB through a thermal adhesive material. After lamination, the components are drilled like a multilayer PCB and then plated through holes are passed through the gaps in the aluminum PCB to provide electrical insulation.
 

Classification of aluminum PCB copper-clad laminates

Aluminum PCB copper-clad laminates are divided into three categories:
 
General-purpose aluminum PCB copper-clad laminate, the insulating layer is composed of epoxy glass cloth bonding sheet;
High heat dissipation aluminum PCB copper-clad laminate, the insulating layer is made of high thermal conductivity epoxy resin or other resin;
Aluminum PCB copper-clad laminate for high-frequency circuits, the insulating layer is made of polyolefin resin or polyimide resin glass cloth bonding sheet.

 

The main use of aluminum PCB

Aluminum PCB
  • Lighting products: high-power LED lighting products.
  • Audio equipment: preamplifier, power amplifier, etc.
  • Power equipment: DC/AC converters, rectifier bridges, solid-state relays, etc.
  • Communication products: high-frequency amplifiers, filter appliances, and transmission circuits.
  • Office automation equipment: motor drives, etc.
  • Automobiles: electronic regulators, igniters, power controllers, etc.
  • Computer: CPU board, floppy disk drive, power supply equipment, etc.

 

Difficulties in manufacturing aluminum PCB

The manufacturing process of almost all aluminum PCBs is basically the same. The main discussion here is the manufacturing process, difficulties, and solutions of aluminum PCB.

Copper etching:

The copper foil used for aluminum PCBs is relatively thick. However, if the copper foil exceeds 3 ounces, the etching requires width compensation. If it does not meet the design requirements, the trace width of the etched aluminum PCB will exceed the tolerance range. Therefore, we should accurately design the trace width compensation of aluminum PCB. The etching factor needs to be controlled during the manufacturing process.

Solder mask printing: 

Due to the thick copper foil, the solder mask printing of aluminum PCB is complex. This is because if the trace copper of the aluminum PCB is too thick, the etched image will be very different between the trace surface and the substrate, and the solder mask printing will be difficult. Therefore, it is necessary to use two solder mask printing. The solder resists oil used should be of good quality. In some cases, the resin is filled first, and then the aluminum PCB solder resist is filled.

Mechanical manufacturing: 

The mechanical manufacturing process involves mechanical drilling, forming, and v-scores, etc. These processes are left in the internal vias, which tends to reduce the electric strength. Therefore, we should use electric milling cutters and professional milling cutters to produce aluminum PCBs in small batches. And we should adjust the drilling parameters to prevent the aluminum PCB from producing burrs. This will help your machinery manufacturing.

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