Fundamentals of Printed Circuit Board
We live in a world driven by technology and use them in nearly every
aspect of our daily lives. We tend to depend on smart electronic devices to
make our lives easier, organised and better connected. Needless to say, all
these electronic devices are designed over a Printed Circuit Board (PCB). PCB
Design Services is a product design process involving high-level engineering
tools for board design.
PCB Design is the point in a design stage at which all the design decisions
made earlier come together and where unforeseen problems related to
performance, power distribution analysis, signal integrity, thermal analysis
and noise mismatching make themselves known and have to be resolved.
What is a PCB or
printed circuit board?
Printed Circuit Board is a critical component in electronics that enables and integrates all the electronic circuits/components of a design. These boards are used in various electronic products – from Smartphones, Smart Tabs, Reader, Camera Devices, Access Controller, Infotainment Systems to Medical devices, Industrial equipment, Automotive Electronics, Radars, Defense, Military and Aerospace equipment and all other computing systems.
Printed circuit boards were initially developed during World War II for military applications. Over the years, this technology was adopted by electronic manufacturers enabling them to offer cost-effective, compact, and power-efficient solutions.
The printed circuit board is made up of a thin layer of conducting
material, usually copper films printed over a non-conducting layer known as
substrate. These substrates are made up of special materials which do not
conduct electricity. The most commonly used substrates are Resins, Fiberglass,
Epoxy Glass, Metal Board, Flame retardant (UL94-V0, UL94-V1) and Polyimides.
Fundamentally PCBs are single layer, double layer, and multi-layer. The
layer classification of Printed Circuit Boards is based on the number of
conductive layers present in the PCB. The below figure shows the cross-section
of various types of PCBs.
Typically, there are two different methods for mounting components on a Printed Circuit Board – through-hole and surface-mount. In the through-hole method, the components consist of thin leads that are pressed through tiny holes in the board on one side and soldered on the other side. The through-hole method is mostly used because of the mechanical stability it provides to the components. In the surface-mount method, the terminals of every component are soldered to the same surface of the Printed Circuit Board directly. Mostly surface-mounted components are small and have a tiny set of solderable pins or Ball Grid Array (BGA) on the component.
PCB Material
Classifications
A PCB is broadly classified into three different categories:
1. Rigid PCB
2. Flex PCB
3. Rigid-Flex PCB
Let’s have a look at these categories in detail:
1. Rigid PCB
Rigid PCB, as the name suggests, is a solid, inflexible PCB which cannot
be twisted or folded to fit into a specific mechanical enclosure. The Rigid PCB
which is also known as the Standard PCB is made up of resin and glass along
with copper foils which are generally known as Laminates.
These laminates come with specific thicknesses to form a standard double-sided
PCB, i.e., 0.4mm, 0.6mm, 0.8mm, 1.2mm, 1.6mm, 2.4mm, etc. Multiple sheets of
these laminates are used along with pre-preg to form a multi-layer design.
Rigid PCBs are the cheapest PCBs. These are also known as the
traditional PCBs and are more widely used in various electronic products. The
best example of a rigid PCB is the computer motherboard. Some of the solid PCBs
that we see in our daily lives are washing machine, refrigerator, telephones,
and calculators.
A simple construction of the double-sided PCB and multi-layer PCB are
shown below:
Benefits of Rigid Printed Circuit
Boards:
o Cost-Effective
solution
o Rugged and
reliable
o High-density
circuits
2. Flex PCB
As the name suggests, the Flex PCB is a flexible PCB that can either be folded or twisted to form a specific shape. The flexible nature of these PCBs helps in accommodating a complex PCB in a smaller form factor thereby reducing the product size. The clutters within a given frame, replacing a wires/cables with a simple flex PCB. The substrate in the Flex PCBs is made up of thin insulating polymer films or polyimides similar to the Rigid PCBs. The key objective of Flex PCBs is to improve the bend and make the product compact and flexible with a lesser layer count. The thickness of the copper foils and the polyimides are made thinner to achieve the flexibility of the product. . “The thinner the copper foil, much reliable is the Flex PCBs.” A Stiffener/Backer is attached to the Flex PCBs to prevent plate buckling and support for components.
Ideally,
Flex PCBs are a great choice for designing PCBs of high speed and controlled
impedance. These PCBs are widely used in aerospace, military, mobile
communications, computers, digital cameras and more.
Benefits of Flex PCBs:
o Allows
bending and folding to fit into an arbitrary shape
o The thin
and lightweight enables a substantial reduction in packaging size
o Flexibility
makes it easier for installation and service
o Effectively
reduce the volume of the product
o Suitable for miniaturized and high-reliability electronic products.
3. Rigid-Flex PCBs
Rigid-flex PCBs are circuit boards that use a combination of both Rigid
and Flexible board technologies in a given design. Typically, Rigid-Flex boards
consist of multiple layers of Rigid and Flex on a PCB, that are interconnected
within a 3D Space. This combination enables efficient space utilization as the
flex part of the circuit can be bent or twisted to achieve the desired shape of
the mechanical design.
Similar to the Rigid PCBs, standard FR4 layers merged along with
polyimide layers, usually in the centre, are used to form a Rigid-Flex PCB.
Rigid-Flex PCBs are most commonly found in devices were space/weight are major
concerns, such as smartphones, digital cameras, USB, CT Scanners, Pacemakers,
and automobiles.
Benefits of Rigid-flex PCBs:
o Rigid-Flex
PCBs enable design freedom, space minimization, weight reduction, that will
eventually reduce the packaging requirements significantly
o Integrates
both rigid and flexible circuits to minimize interconnects
o Dynamic
and flexible and fits into smaller spaces
o Suitable
for high-density, miniaturized and high-reliability electronic products
o Flex
circuits eliminate wire routing errors
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| BACK SIDE CONTROLLER BOARD PCB |
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| FRONT SIDE CONTROLLER BOARD PCB |
So, there you have it. The basics of PCB and it’s classification.
Ref:-
1. Mistral Solutions Pvt. Ltd
2. https://www.tempoautomation.com/blog/
3. https://jayconsystems.com/circuit-board-design/