Advice on How to Design a PCB Layout
Fri, Jan 17, 2020
As with any technical operation, there are good and bad ways to design a product. In this article, you will learn some of the best ways to design a printed circuit board layout.
USE PARALLEL ROUTING FOR DIFFERENTIAL SIGNAL TRACES
When designing your layout, you need to be sure that your differential signals, which are usually there to increase dynamic range, are parallel to one another. When they are not parallel to one another and don’t go on a similar path, noise is distributed unevenly.
DECIDE PROPER LINE WIDTH BY CURRENT FREQUENCY AND SIZE
Printed circuit boards are known for these super small pathways or lines that are used to connect components to one another. Electricity currents travel along these pathways to these different components.
If the lines on your printed circuit board are not large enough for the number of electrical currents moving along those paths, it can cause the circuit board to overheat. As a result, the overheated circuit board could catch on fire and potentially render the device circuit board was made unusable.
During the design process, use a formula to calculate the appropriate width for your printed circuit board.
KEEP HEAT SPOTS IN MIND
While heat is being discussed, it is important that you keep in mind how much heat one area of the printed circuit board can actually take before issues arise. This will influence how many components you add to the circuit board as well as their locations.
To understand potential hot spots, you will need to understand the thermal resistance of the circuit board. That means you have to learn how much heat will increase per Watt of power depending on the circumstance. One way to allow for heat dispensation is by adding a heat sink or fan to keep your circuit board cool enough to perform its functions.
DO A TEST RUN
After you have your initial design idea, print out your design on a piece of paper. Be sure your printed design is the actual size of your final product. Then, take your components and lay them out on the board. This will help you to avoid complications when you have the board designed.
Make the necessary adjustments before pathways are carved and components are attached.
KNOW HOW TO ETCH YOUR SPECIFIC TYPE OF CIRCUIT BOARD
There are two main types of printed circuit boards: small printed circuit boards and high-density interconnector printed circuit boards.
For smaller circuit boards, the design is printed onto transfer paper that is stuck onto a plate of sanded copper. Technicians then run the copper plate through a laminator between five to seven times to heat it up. The plate is then put into a cold bath where the technician then waits for the paper to float off.
The copper is then placed into an etching solution for 25 to 30 minutes. The copper dissolves around the design. Technicians wipe the coper clean with water and rubbing alcohol. They then drill the holes in the board.
For high-density interconnector printed circuit boards, the process is done by a light beam or tiny drill. This process is largely automated and is used to make really fine lines and pathways. This is usually for a more complex device like a smartphone, gaming system, or television.
SOLDER COMPONENTS FROM SMALL TO LARGE
Soldering components to such a small board can be difficult, especially when you put the larger components on the board first.
Instead, start by soldering the smaller components so you can easily move around the board with your soldering gun. One smaller component you may start with is the Surface Mount Devices. End by attaching larger components like terminal blocks and capacitors.
LEAVE SPACE BETWEEN COMPONENTS
Since components are now a topic of discussion, you must make sure that you leave some space between your components.
You will be working with a small amount of space and will likely have to jam your components pretty close together for everything to fit. However, you don’t want to be in a situation where you attach these components only to find you cannot attach or route wires.
This could make all of your work in designing and creating your printed circuit board completely useless. This is why it is important to print out your design and lay your components on top. This simple process can keep you from messing up your printed circuit board, make adjustments and you will see that your wires can spread out and easily conform to the board when you leave more space.
CHANGE WIRING DIRECTIONS BETWEEN LAYERS
Especially with HDI PCBs, you will find that a lot of circuit boards are actually layered. This is to assure that all of the pathways can do their job without trying to force all of the pathways onto one small board.
Wiring can be difficult. If you wire all of your layers in the same direction, it can make the wiring bulky, leaving little room for crossovers. However, if you alternate the directions in which you are wiring, the wires can easily cross over or under one another.
DESIGN YOUR POWER TRACES DIFFERENTLY
Power traces are important parts of circuit boards, especially in power circuits. If you fail to make these traces wide enough, you could experience malfunctions in your printed circuit board. These particular issues can lead to overheating and can cause your circuit board to catch fire while a device is in use.
There are several online calculators that can assist you in determining the right power trace size for your circuit board.
Designing and creating a printed circuit board is simple if you know the basics of design and some design concepts. The most important thing you can do is make sure that you avoid any mistake that will cause your printed circuit board to become defective.
Heat distribution and a good bit of planning and layout time are essential in the creation of a PCB.
To learn more about PCB layout, Click here.