PCB design Tips

PCB design is a complicated work that is mastered by years of on-hand experience. This is due to the fact that electronic design inherently requires knowledge of many design areas. For example there are many choices of PCB laminates, conductors, number of planes etc that can be chosen according to the need of the product. Furthermore the design involves different types of electronics circuit- analog RF front end, digital, mixed type involving FPGA, microprocessors etc. Mechanical factors and environmental factors are other important design consideration. PCB designer face with these challenges with aim to produce cost effective and electrical, mechanical and environmental stable design.

Complete PCB design consideration can take complete book by itself, so it is not the intent here to discuss all the PCB design aspects but to provide concise part of important issues to be taken into account especially by beginners.

General Consideration and planning before starting PCB design:

1. Board size, the environment
2. Border lines 
3. Mechanical mounting within 25mm from edges
4. Connectors
5. Conductor dimension(Resistance, Capacitive coupling, Inductor coupling)

General consideration for component placement

1. Place mechanical mounting support, connectors, LED, heat sink
2. Divide the circuit into functional units and subunits
3. Place critical and larger components by adhering to the signal flow as much as possible
4. Place smaller components in between the larger components
5. Isolate inductive components, magnetic field generators, transformers from other components
6. Place high frequency component together
7. Avoid placing switch mode power supply near the ADC, DAC and analog circuitry
8. Use separate voltage regulator for analog circuitry
9. Be aware that PLDs and VLSI chips can generate switching current that infliterate into other components. Place bypass capacitors at their pins.
10. Orient Polarized Parts such as diodes and electrolytic caps in the same direction

General consideration for conductors

1. Determine the conductor dimension and spacing between them and other components
2. Conductor width and spacing cannot be smaller than 4mils(0.1mm)
3. Do not make conductors allow to make sharp angle bends
4. Draw tracks along Y-axis in component side and tracks along X-axis on solder side in a double sided PCB
5. Make the ground and power conductors width larger(Ground>Power>Signal)
6. Make ground conductor capacity such that it can withstand different power supply load
7. For high speed mixed circuitry use separate power and ground planes
8. Spacing between power and ground conductors should be large as possible to avoid cross-talk
9. Ground plane is necessary in all high frequency design