PCB or Printed Circuit Board is a mechanical assembly that consists of etched copper patterns laminated with layers of fiberglass used to rigidly mount electronic parts that all contribute to the total functionality of the entire board. Specialized electronic engineers make use of Computer-Aided Software (CAD) to design the board overlay and dictate its functionality. Below are some of tips to ensure a functional printed circuit board: And more tips are given at www.pcbnet.com.
General Design Tips
When finding a CAD package, always consider a few important points and not only the price:
- Satisfied customers: How many people have bought it and are still using it?
- User-friendly: If it’s hard to use, you won’t use it.
- Capability: Programs tend to limit the design in aspects such as the number of layers, components and size.
When starting out in the field of PCB fabrication, always check and compare with the work of other people. Start out simple and once you’re comfortable, slowly stretch your comfort zone.
Schematics are always important. Making a board without schematics is like looking for a restaurant in the middle of the city without a map.
Always add accessible test points for troubleshooting.
Place functional parts and components only on the top side of the board unless it’s absolutely necessary to use the two sides. This allows for a simpler circuit that should bring about fewer problems.
Place all the components that should be in specific locations. This includes switches, heat sinks, mounting holes, LEDs, connectors or any other items mounted to an external location.
Parts connecting to each other should be placed closer to one another. Ensuring this makes the PCB fabrication process much easier.
Arrange integrated circuits to a maximum of two orientations: right or left, and up or down.
Polarized parts such as diodes and electrolytic caps should have positive leads in the same orientation.
Leave generous space between integrated circuits for traces. This will make soldering a breeze.
Print the layout in the same size as the desired board and place the components on top of the layout paper just to check if they match.
The width of the tracing lines are important as the larger the width, the lower the resistance. This would reduce the thermal strain caused by dissipation. The table below is a rough guide on how wide a signal trace should be for certain amounts of current:
0.010″ – 0.3 Amperes
0.015″ – 0.4 Amperes
0.020″ – 0.7 Amperes
0.025″ – 1.0 Amperes
0.050″ – 2.0 Amperes
0.100″ – 4.0 Amperes
0.150″ – 6.0 Amperes
Always take into consideration that heat degrades performance and may even damage the circuit if not well dissipated. Always add heat sinks in areas where you expect greater thermal activity and keep critical parts of the circuit away from heat sources.
Always use vias, plated-through holes, or feed-through holes, to move signals from one layer to another.
As a general practice in PCB fabrication, one side of the board should have vertical traces and the other side should have horizontal traces. For multilayer boards, use alternating patterns to ensure continuity.
It’s common practice to avoid 90-degree signal traces; restrict them to alternating 45-degree angles with a short leg in between.
Always check your work and check every routing to verify that nothing is missing or mistakenly wired. This is easily done by running through the schematics one connection at a time. Metal components such as connectors, batteries, crystals, switches, and heat sinks can cause shorts when placed above traces.
Quite possibly, this final tip is the most important of all – double-check your work. Always remember that design is half the work when it comes to PCB fabrication and any defects here will ripple across the finished product.