A concise overview of what the Printed Circuit Board (PCB)

Introduction

The PCB is commonly known as the 'Printed Circuit Board', 'Printed wiring boards', or 'Printed wiring cards'. PCBs are fabricated to mount essential electronic components to design a circuit for a typical device and application. The PCBs are made from a combination of varied types of PCB-making material and electrical components. PCB components consist of the capacitor, inductors, resistors, diodes, sensors, etc. The material used for making PCB boards comprises non-conductive materials like plastics, copper, fiberglass, composite epoxy resins, etc. PCBs vary in shape, size, layers, and dimensions.

Most of the PCBs are rectangular shaped and even round shape boards, the shape, and sizes of PCBs allow more surface. The common PCB layers include the substrate layer, solder mask layer, copper layer, and silkscreen layer. The components are mounted through either SMD (surface mount method) or the through-hole methods. To hold and connect the circuits, components like transistors, resistors, and IC (Integrated circuits) the conductive paths are written and printed on the boards. It also offers mechanical support and a route for the current to flow to its electronic parts. The colors of PCB are termed PCB color codes, which include white, blue, black, yellow, red, etc. The solder mask color does not affect the performance of the PCB.

Different types of PCB

The common types of PCBs are enlisted as follows:

1. Single Layer PCB

It is the simplest to design and manufacture also it is a low-cost PCB. It is one layered PCB that consists of a base substrate (fiberglass) and another single side and conductive (copper) layer. Holes are not plotted on the board for the electronic components. They are mostly used in many complex electronic devices like vending machines, stereo equipment, printers, etc.

2. Double Layer PCB

Double-layered PCB consists of one conductive layer and above the other non-conductive substrate layer on the reverse side, that is both the top and bottom layers. These types of PCBs are used in complex circuits, and they are used in lighting and car dashboards like better advanced electronic systems.

3. Multi-Layer PCB

The multi-layered PCB contains 3 or more conductive layers, the PCB is made using the 'Sandwiched model' which consists of many double-sided conductive layers separated by an equivalent number of insulating material sheets. These sheets are bonded and laminated together underneath high pressures. Multilayer PCB has increased functionality in the applications like medical equipment, computers, complex circuits and devices, and also in GPS trackers too.

4. High-Density Interconnect (HDI) PCB

These are recent new kinds of printed circuit boards. HDI PCBs are compact and have fewer layers as compared to multi-layer PCBs. HDI PCB holds the advantage of precision-based manufacturing technology to pack most of the functionality it can into a little space. That is done with the help of multiple conductive layers, laser drilled tiny vials, fine lines and tolerances, and advanced laminate materials. It can adapt to the complex routing of high pin count chips and other high-tech miniaturized components. They are mostly used in the latest technology systems like smartphones and game consoles.

5. High-Frequency PCB

This type of PCB is concerned to design by itself and also facilitates signals over 1 GHz to up to 100 GHz (gigahertz). These PCBs can be flex or rigid type of PCBs having a high frequency, they are mostly used in HDI(High-Density Interconnect) technology. According to the type of applications, the high-frequency PCB may need the use of controlled impedance and advanced laminate materials. These sorts of PCBs are used in telecommunications, military and aerospace applications, automotive, and RF microwaves.

6. Rigid PCB

Rigid PCBs can either be single-sided, double-sided, or multilayered. They are solid, flexible, cost-effective, and hard-wearing. They are made from various layers that are joined together using heat and an adhesive. Rigid PCBs are used in terms of the components that remain fixed in products and industries.

7. Flexible PCB

Flexible PCBs also known as Flex PCBs or Flex circuits are particularly designed to fit into the product or a device. They are light, usually thin, and can perform exceptionally well in contoured shapes and little spaces. This type of PCB does not utilize fiberglass for the substrate layer of the board. It is due to the material used being very rigid to ensure PCB is flexible and long-lasting. Plastics are used like Kapton, a polyimide material, for the substrate layer.

8. Rigid-flex PCB

It is a mixed form of PCB having combined elements of rigid and flexible circuit boards. Rigid-flex PCBs are designed in 3D. This allows the board to be flexed and twisted into a desirable shape. It can be curved, folded, continually flexed, or in flexed shape during the manufacturing process. These boards are thinner than existing PCBs. Due to thin copper layers and adhesive-less laminates, a rigid-flex PCB is a thin, small, and light solution.

9. LED PCB

It is a type of PCB which is mainly designed and used for a wide array of lighting modules and their applications. During the process of manufacturing the LED PCB, several LEDs are mounted to the PCB, which forms a complete circuit. Numerous industries use LED PCBs for controlling lighting systems. They are used in automotive lighting, street lighting, work lamps, and torches.

10. Blank PCB

It is an empty circuit board as per its name which is free from any electronic components that are installed to create a functional circuit board. It is also known as a 'copper-clad circuit board' due to its visible layers of copper. This PCB is not only entirely made of copper, but also other materials like silicon that are used in the process of creating the PCB durable and sturdy. This type of board provides that an efficient and adequate flow of energy is there when the components are placed on the board.

11. Dotted PCB

It is also known as Zero PCB or DOT PCB and also as Perfboard. It is a thin, all-purpose, rigid sheet board that has pre-drilled holes with a solders pad for each spot of the metal like the copper clad board. The components are mounted and later soldered using a soldering gun with and without using strand wire. The benefit of this PCB is that the short circuit is avoided.

Procedural making of PCB

It typically takes 40-50 days to make the PCB. The manufacturer uses a particular printer called a plotter, which creates a photo film on PCB to print circuit boards. The PCB-making process goes as follows:

Design and get the output of the PCB layout.
From the layout file to the film of making PCB.
Printing the internal layers of PCB.
Extracting the undesirable copper.
Optical inspection and alignment of the layer.
Bond and layer-up of PCB.
Drilling.
Copper deposition and plating procedure.
PCB outer layers imaging.
Plotting and final etching.
Application of solder mask.
Surface finishing of PCB.
Profiling and route out.
Electrical test for reliability.
Visual inspection and quality assessment.
Packaging and delivery of the PCB (Final stage).

Software used for PCB Designing

There are different types of PCB design software such as Eagle, OrCAD, KiCad, Proteus, Altium, and many more.

Conclusion

The current market is getting much faster and more advanced in terms of surface mounting technology in different electronic boards. In terms of power, surface, and fabrication capabilities, laminate materials, and certification to meet the quality, precision, and performance the PCBs are demanded in industries as per the requirements.