Aug 13, 2019|General
Every electrical engineer will at some point have to design a printed circuit board, and for the novice PCB designer, this process can seem somewhat intimidating. Understanding the basics is critical to designing PCBs, so this article will cover the fundamentals of PCB creation. We’ll go over the most critical design steps, as well as essential rules of design for beginners.
With a little bit of patience and practice, you’ll be well on your way to creating your first PCBs. Let’s get started.
How to Design PCBs
Before we get into the PCB design process steps, we must first answer one critical question: what is a PCB?
A PCB, or printed circuit board, is a small green board made out of precious metals that connects all the electrical components essential to the proper functioning of an electronic device. The PCB manufacturing process includes various steps and generally requires printed circuit board manufacturers to bring the final vision to life.
The first of the PCB design steps is perhaps the most crucial of them all: determining why you need a PCB. What problem are you trying to create a solution for? What is the aim of this PCB? Without a clear objective, it’s impossible to build the right answer, so take time to understand your needs.
Once you’ve identified the problem, you should also determine what you’d like the product’s final concept to be. Some key parts of the final concept include:
* Design features
* Required functions
* Required performance functionality
* Rough final dimensions
The next step is to plan the layout, and the idea here is that you start to conceptualize how everything will work. This phase can be a simple as sketching out your design on a piece of paper. You can also use a breadboard, which is a simple plug-and-play board that is perfect for testing components and prototypes, before moving on to the schematics part of the process.
Bill of Materials
As you’re creating the PCB schematics (which we’ll get into in the next section), you should also create the bill of materials or BOM. The BOM is a list of needed material that’s chosen by making sure the materials satisfy individual requirements, like the maximum operating voltage requirements and tolerance criteria.
Once the material has been chosen, the list should be kept up-to-date with the schematics, and it should include the following info:
* Reference designators
* Manufacturer part number
* PCB footprint
You’ve identified the solution and planned the layout. Now it comes time to build out the schematics of your PCB. The PCB schematics are essentially a blueprint that shows how all the components are connected and how they function. They are your roadmap to a successful PCB.
The most productive way to create PCB schematics is through the use of PCB design tools, of which there are many. PCB design tools make the whole process a little easier by allowing you to see how everything will work before it comes to life.
Using a trace width calculator is very helpful in fleshing out the details of the inner and outer layers. These programs also help you adhere to PCB layout design rules and understand any design limits.
Creating schematics that are complete and accurate is vital to the success of your PCB because they include all the design information that ensures that the circuit works effectively.
Now comes the fun part: after creating the blueprint, which only tells us which components are connected, it’s time to decide where those components actually go.
To determine the best placement, you should create an outline with your ideal component placement before putting anything on the board. This outline will be based on a few factors, such as component function, thermal management, and how much electrical noise they generate.
The placement should be as follows: connectors, power circuits, sensitive and precision circuits, critical circuit components, and finally, everything else. Once they are put in place, you should make sure to review the placement to ensure it’s correct, as well as make any changes needed to optimize the PCB’s performance.
Insert Drill Holes
There are some other key ideas to keep in mind when inserting components.
The first is that edge components should be inserted first. When we say edge components, we’re referring to USB ports, power jacks, etc. These components must be inserted first because their position is determined by the device the board will be placed in and is therefore inflexible.
The second key idea is that the largest components must be inserted next since they affect what needs to be placed around it.
And here are some final tips to remember:
* Don’t separate compatible parts
* Placement should minimize length between components
* Placement should also reduce cross-crossing of air wire connections between them
* Make sure to leave room between components
* Avoid overlapping parts since they’ll need room for assembly
The last step is to route the connections between various parts. Routing the connections turns all the components into copper traces. These copper traces connect the prototype to connections that carry current, allowing them to function.
Four different routing methods allow you to carry out this process: manual trace placement, follow-me router, connection machine, and autoroute. Each of these methods is used in different situations.
Before you can consider your PCB done, the final step is to review the design to make sure that everything is working as it should be. Doing so consists of a final electrical test that confirms the PCB’s functionality and whether it performs as the schematics indicate it should. If it does, give yourself a big congratulations: you’ve just created your first PCB!
And one last thing: when it comes to creating PCBs, there is no right or wrong answer about how to place your parts. Instead, there are varying degrees of optimization that a little practice will reveal, so take some time to understand how everything works and enjoy the process.