Aluminum PCBs are printed
Circuit Boards which contain a thin layer of conductive dielectric material.
They are also known as Aluminum Clad, Aluminum base, MCPCB (Metal Clad Printed
Circuit Board), IMS (Insulated Metal Substrate), Thermally Conductive PCBs etc.
Aluminum PCBs were developed in the 1970s, soon after which they’re
applications increased dramatically. The first application was their use in Amplification
Hybrid Integrated Circuits. Now they are being used at a large scale due to
which it is necessary for us to have an idea of Aluminum PCBs and their
Structure of Aluminum PCBs:
Aluminum PCBs are aluminum
based CCLs (CCL is a type of base material of PCBs). AluminumPCBs are actually
quite similar to FR4 PCBs. The basic structure of Aluminum PCBs is four
layered. It consists of a layer of copper foil, a dielectric layer, an aluminum
base layer and aluminum base membrane.
· Copper Foil Layer: the copper layer used is
relatively thicker than normal CCLs ( 1oz-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 50μm to 200μm thick. It had a low thermal
resistance and it suitable for its application.
· Aluminum Base: The third layer isthe
aluminum base which is made up of aluminum substrate. It has a high thermal
· Aluminum Base Membrane
Layer: Aluminum base membrane is selective. It has a protective role by keeping the
aluminum surface safe from scraping and unwanted etching. It is of two types
i.e. Lower than 120 degree or around 250 degrees (anti high temperature)
Performance of Aluminum PCBs
· Thermal Dissipation: the performance of
aluminum PCBs while dissipating heat is quite well as compared to ordinary FR4
PCBs. For example, a FR4 PCB that is 1.5mm thick will have thermal resistance
of 20-22 degrees per watt whiles a aluminum PCB 1. 5mm thick will have a
thermal resistance of 1-2 degrees per watt.
Expansion: each substance has its
own coefficient of thermal expansion. The CTE of aluminum (22ppm/C) and copper(18ppm/C)is
quite close. Since aluminum PCBs work well in terms of Thermal dissipation they
do not have severe expansion or contraction issues. They work excellently and
are durable and reliable.
· Dimensional Stability: aluminum PCBs show dimensional
stability and stable size. For example, when they are heated from 30-140
degrees, their size only had a change by 2.5%-3.0%.
· Others: Aluminum PCBs can be
used in power device surface mount technology. They are effective for use in
circuit design because of their performance in terms of thermal expansion of
circuit design. They help to prolong products shelf life and product power
density. They are also extremely reliable. They can help to shrink the overall
volume of the product and is also a cheaper option. They show electromagnetic shielding
and high dielectric strength.
Classification of Aluminum PCBs: Aluminum PCBs are
essentially divided into three categories.
1: Universal Aluminum PCB: the dielectric layer
used here is made up of epoxy glass fiber pre-preg.
2: High Thermal-Conductive Aluminum
dielectric layer is made up of epoxy resin. The resin used must have high
3: High-frequency Aluminum PCB: the dielectric layer is
composed of polyolefin or polyimide resin glass fiber pre-preg.
Manufacturing Difficulties of Aluminum PCBs:
The manufacturing process
for nearly all aluminum PCBs is essentially the same. Here we will discuss the
major manufacturing processes, the difficulties and their solutions.
1: Copper Etching: the copper foil used in Aluminum
PCBs is comparatively thicker. If the copper foil is over 3oz however, the
etching requires width compensation. If it is not according to the demand of
the design, the trace width will be out of tolerance after etching. Therefore the
trace width compensation should be designed accurately. The etching factors
need to be controlled during manufacturing process.
2: Solder Mask Printing: due to the 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 trace surface and base board and solder mask printing will be difficult.
Therefore, the two-time solder mask printing is used. The solder mask oil used
should be of good quality and in some cases the resin filling is done first and
then solder mask.
3: Mechanical Manufacturing: the mechanical manufacturing process
involves mechanical drilling, molding and v-scoring etc. which Is left on
internal via. This tends to reduce electrical strength. Therefore, the electric
milling and professional milling cutter should be utilized for low-volume
manufacturing of products. The drilling parameters should be adjusted to
prevent burr from generating. This will help your mechanical manufacturing.
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manufacturers in Shenzhen, China. Built over 2400 sqm of land, this company
specializes in manufacturing high-quality PCB’s (Printed Circuit Boards) in low
price. These boards are custom designed according to your needs. Just looking
at the “product categories” PCBgogo specializes in, we realize how much they
have expanded over the years. These categories include data communication,
optical networking, medical treatment, industrial control, aerospace/military
etc. just to name a few.