Are you interested in designing a PCB for your project? Do you want to learn the procedures, the techniques, the guidelines & the tools for designing a PCB ? Or are you looking to acquire practical skills to enhance your expertise and knowledge in electronics?, then this blog is for you. We give you an introduction on the topic as well as pointers to learn them. We discuss,

• What is PCB design?
• Alternate methods
• PCB structure
• Why learn PCB design?
• What we offer?
• Summary
  

What is PCB design?

What is a PCB?
All electronic products use a board to mount and interconnect the electronic components
according to a circuit which is specific to the product. This board is the PCB aka printed circuit board.

What is PCB design?
PCB design is the process of turning an electronic circuit into a format that could be interpreted by the PCB manufacturers for fabricating the PCB. This is done with the help of computers & EDA software tools.

What is PCB made of?
A PCB is made from copper clad laminates. Copper cladding could be present on one side or both sides of the insulating dielectric substrate. Depending on the materials used for the dielectric substrate and the ways of laminating and connecting the conductive material there are different variants of PCB boards. Manufacturers fabricate the PCB according to the circuit specified, the material specified & the number of layers specified in the design.

When is PCB designed?
A PCB could be designed during prototyping, the final stage or even as revisions of the final product. The design of the PCB has a strong impact on the mechanical and electrical performances of the final product.

Who designs the PCB?
For some designers, the PCB design is easy but for many others the process of designing and laying out a PCB can be a very daunting task. Companies usually have their own dedicated PCB design departments. For simpler and low performance circuits, a quick design could be done by anyone in the development team who has a basic know how of using the software tools. However complicated designs involving hundreds of components and thousands of tracks that meets a whole host of physical and electrical requirements warrant a great deal of knowledge, talent & patience. To make matters even worse, PCB traces have resistance, inductance, and capacitance, just like a circuit. All these affect the performance in case of high speed digital, RF & analog circuits. A poor design ignoring these elements will render the PCB useless. Proper PCB design is very often an integral part of a product design. In PCB design, there are many rules as well as good practices to be followed. PCB design is a highly creative process. No wonder why PCB layout is considered as an art work by many designers.

Alternate methods

Before delving deeper into PCB design, let's take a look at some of the  alternate or earlier methods used in implementing the circuit connections.

Point to Point Wiring
This was a widely used method for connecting electronic components before PCB. Electronics devices were constructed with component leads soldered directly to each other. Connecting components in this way means there is less distance between them and therefore less resistance in the circuit. Since the signal does not have to travel as far, it results in the cleanest and strongest signal path possible. For this reason, some Hi-Fi audio equipment and amplifiers are still built using point-to-point style wiring. The major downside of this method is the layout looks complicated. Its hard to maintain or rework on such a layout.

Tag board, Turret board, Eyelet board
To overcome the complex layout of point to point wiring , terminal strips were designed. Here the components are laced through or laced around metal terminals that come on either strips or boards. Everything is then connected with wires to where they need to go. The layouts look more uniform and also decreases production time. This method is used even today in certain cases like prototyping where only a few components are used and also in power electronics where the components are bulky and serviceability is a major requirement. The disadvantage is it cannot be automated. All soldering work has to be done by hand.

Strip board
Its a generic board used in implementing circuit connections. It has wide parallel strips of copper cladding running in one direction all the way across one side of the substrate. The strip has holes with a spacing of 0.1 inches/(2.54 mm). Strip board is also known by the name vero board. Strip board is mainly used in prototyping as well as in some cases, as final PCB if the component count is very few. Strip boards are available in various dimensions. They are very economical.

Perf board
Perf board is a variation of the strip board. It is also known as DOT PCB. Here each hole is electrically isolated from each other. This method also cannot be automated. All soldering work has to be done by hand.

The years before CAD
Paul Eisler is credited with the invention of the printed circuit board. He was an Austrian inventor born in Vienna. Eisler patented a method of etching copper circuits onto a layer of copper foil laminated to a non-conductive base. This was in the 1940s. Towards the end of 1950s printed circuit boards became mainstream with the transistor radio. Printed circuit boards of those times were designed by hand without the use of computers until about 1980s. How did they do it? A host of tools were needed before embarking on a PCB design in those days such as a drafting table, a light table, mylar sheets, pencils, templates and a few more. The first step was to draw the schematic. The schematics were drawn by electronics draftsmen who were specialized in the trade. The drawn schematics were checked for accuracy and passed onto the layout designer. The layout designer had a booklet of component decals to be used for the layout. It was either sticker or sometimes had to be drawn by hand. These decals were used for standard component packages and dimensions. After the component layouts were done, the wiring is done using coloured pencils. Once the layout is complete, photograph of each layer is taken and send to the manufacturer for fabrication. The period before CAD was a tough one. This method was tedious and costly. Once CAD took off, manual drawing became obsolete.

PCB structure

A PCB consists of a blank base material also known as the substrate or core or board. A blank base material coated with copper on one or both sides is known as a copper clad board. The substrate is usually 1.6mm thick. Other common thicknesses include 0.8mm and 2.4mm. There are many types of PCB substrate material. The most common one is a standard woven epoxy glass material known as FR4. Higher grade base materials like Teflon are also available, but are only used for designs that specifically need them. Cheaper grade materials like phenolic base and CEM-1 are used when cost is a factor. However they are not suitable for fine tolerance designs. The dielectric constant of the core is an important parameter. It is used for calculating high speed transmission line parameters and other effects. An FR4 PCB can typically have a dielectric constant ranging from under 4, to almost 5. A multi-layer board is made up of various individual boards separated by Preimpregnated Bonding Layers, also known as “prepreg”. The prepreg and core are two different parts of the PCB. The core is the FR4 material with copper traces on one or both sides. The prepreg bonds two copper layers together or binds one copper layer and a core. In doing so it retains the separation between the two materials being bonded. The prepreg material is impregnated with a resin, where the resin is hardened but left uncured. Two cores could be stacked on each side of a prepreg laminate. On exposing the stack to heat causes the resin to begin bonding to the adjacent layers.

Why learn PCB design?

• PCB is the backbone of all electronic devices. So for an Electronics/Electrical engineer this is a must have skill set.
• As a PCB designer you will be dealing with some of the most advanced software of the trade.
  
• This is a skill set that requires multidisciplinary knowledge. The board must fit within the box. Dimensions are the key here. The dimensions of the board, the box, the screws, the connectors all matters.
  
• High speed board design is considered by many as an art. This is a skill set in high demand.
• PCB designer is highly responsible for the product's electrical and high speed performances. High responsibility means highly rewarding too.
• Signal Integrity, EMC and regulatory compliance are some of the challenges that a PCB designer has to face on a regular basis. Only by having a deep knowledge on the subject matter, some creative skills in routing and patience they can be solved.
• Students choosing a career in circuit designing and product making should learn PCB design. Above all this is a very satisfying and an enjoyable job.
  

What we offer?

So how do you design a PCB?
What are the tools used?
How do you choose the parameters for design?
How do you design a multi layer PCB?
How do you employ EMC design techniques in PCB design?

We at CODECIRCUITRY offers the course "Learn PCB Design and Layout Techniques" for you to get started in PCB design.  This course covers all these topics. The is course is a blend of both theory and practicals. This is a step-by-step course on printed circuit board design with information suitable for beginners. This course is for anyone who wants to design printed circuit boards on their own. Knowledge in basic electronic theory is a prerequisite to fully grasp certain concepts.

The entire course is divided into 7 modules. Module 0 to Module 6.

• Module 0 is an introductory topic that introduces you to this course. There is one more session in this module which lists the FAQs.
  
• Module 1 to Module 3 are categorized into several sub topics. And each sub topic is divided into several video sessions. At the end of each sub topic there will be a quiz of 5 MCQs, reviewing the learning from all the video sessions under a specific sub topic. Similarly each module ends with a module test. This will be a test of around 15 MCQs. Also at the end of each module , there will be a self assessed assignment for you to work on. The purpose of these assignments is to make the student explore certain things on their own. Hints are provided on how to complete the assignment.
• Module 1 introduces the components and tools used in PCB designing. There are 3 subtopics in this module. Topic 1 discusses Component mounting & soldering technologies in detail. Topic 2 discusses component packaging elaborately. All commonly used packaging types are discussed. The 3rd topic is about EDA tools commonly used for the designs. Here we design our first PCB using ExpressPCB software.
• Module 2 is where the practicals begin. This module is divided into 2 topics. Topic 1 discusses schematic design. Details regarding project creation and using the tools in KiCAD schematic editor is discussed first . Schematic guidelines are discussed next. And then 3 exercises are done with varying complexities. Topic 2 discusses PCB layout design. Following the same approach as the previous one, first details regarding project creation and using the tools in KiCAD layout editor is discussed . PCB layout guidelines are discussed next and then the layout design of the 3 exercises we did in the previous topic are completed here. In addition to these, several corrections/additions and advanced methods are done in subsequent video sessions to reinforce the learning. Finally we generate fabrication output for PCB manufacturer. By the end of module 2, you should be able to do PCB designs on your own.
• In Module 3, some advanced topics are discussed. The topics discussed in this topic will take your understanding on the subject to a whole different level. This is a very important module. Module 3 is divided into 2 topics. The first topic discusses EMC, ESD and circuit protection. This topic is divided into several sessions with each session detailing the guidelines to be followed for achieving EMC compliance, protecting the circuit and improving the high speed performances of the PCB. Discussions on ground planes and mixed signal routing are also done. In the second topic emphasis is given for advanced routing techniques such as differential pair & BGA package.
• Module 4 is where the final project is presented. A 4 layer PCB design is done as project, specifically we design a carrier board for Raspberry Pi compute 3 module.
• Module 5 is the final test module. There will be around 60 questions in MCQ format.
• Module 6 is the summary module, where the course is concluded with details on how to advance the knowledge and skill after course completion.

Expected outcomes include the following:

• Expertise in KiCAD open source PCB design tool.
• Capability in designing a PCB on your own.
• Sound experience in multi-layer PCB designs.
• Sound understanding of schematic and layout design guidelines.
  
• Quintessential knowledge in signal integrity & EMC challenges.
  
• Good exposure to advanced topics like mixed signal design, BGA & differential pair routing.
  

Summary

PCB Design is an interdisciplinary skill involving both mechanical and electrical domains. At one point you might be measuring the dimensions. At another instant you possibly could be calculating the impedance or current flow or temperature rise. Some consider PCB design to be an art. Designers try to express them by placing the components aesthetically. You should be very creative and technically sound to make the PCB aesthetically pleasing as well as highly functional. The process of transforming an idea into a PCB architecture has several stages with well defined steps. Each new PCB is an opportunity to be creative as well as improve your technical skills . Our course aims to equip you with technical knowledge on PCB design, help you build multi layer PCB and thus launch yourself to a platform from where you could explore the advanced concepts on your own. We welcome you to join our course "Learn PCB Design and Layout Techniques".