Hot Search Terms
Hot Search Terms

PCB Design Layout and Routing Tips

Nov 24 - 2023

PCB Design Layout and Routing Tips

If PCB layout and wiring are not proper, it often leads to abnormal and unreliable circuit operation. This article lists some points that should be noted in the actual PCB layout and wiring to help make your PCB project more accurate and reliable.

Size of the alignment

The copper wires on the PCB board have impedance, which also develops to mean that one carries on connecting the wires on the circuit design diagram will have voltage drop, power consumption, and temperature rise when the current can flow through it on the actual board plan.

PCB design engineers usually use the length, thickness and width of the wire to control its impedance. Resistance is a physical property of copper, the metal used to make PCB wires. Since we can't change the physical properties of copper, let's control the size of the wire.

The thickness of PCB alignment is measured in ounces of copper. If we spread an ounce of copper evenly over an area of 1 square foot, the thickness is one ounce of copper, which is about one thousandth of an inch. Many PCB designers use 1oz vs 2oz Copper, but many PCB manufacturers can provide 6 ounces of thickness. Note, however, that it is difficult to lay down thick copper in many situations where accuracy is required, such as where pins are close together. It is a good idea to consult with the PCB manufacturer at the design stage to find out their production capabilities.

You can determine your thickness and width by using a "PCB line width calculator", which you can set to increase the temperature by 5 degrees Celsius. Of course, if you have enough board space, wiring is easy and you can use wide wires as not to increase the cost of low impedance.

If your board is multilayer, the temperature of the outer alignment will definitely be lower than the inner layer because the heat from the inner layer has to go through long paths of internal alignments, vias, material layers, etc. to dissipate the heat.

Loops must be as small as possible

Loops, especially for high frequency loops, should be as small as we possibly can. Smaller loops are analyzed to have relatively low inductance and resistance. Placing the loop above the ground plane will also further develop a lower inductance. Smaller loops reduce the high frequency operating voltage spikes that can be caused by the following formulas:

Small loops can also reduce external interference caused by inductance at certain nodes, or signals broadcast at nodes that can affect other circuits. Except, of course, for antennas used for wireless communications. While building an operational amplifier, make the loop as small as possible to prevent noise coupling into the circuit.

Layout of decoupling capacitors

Decoupling capacitors should be placed as close as possible to the "power" and "ground" pins of the IC to maximize decoupling efficiency. Placing capacitors too far away introduces stray inductance, which can be reduced by creating more vias between the capacitor pins and the ground plane.

Kelvin Connections

Kelvin connections are very useful measurements. Kelvin connections must be in place to minimize stray resistance and inductance. For example,pcblink how to test pcb board with a multimeter, a Kelvin connection for a current sensing resistor should be placed on the resistor pad, not anywhere along the wire. Although it may not seem to make a difference on the schematic if the connection is placed on the resistor pad or at any point, because the actual wiring is inductive and resistive, failure to use the Kelvin connection may invalidate your measurements.

Keep digital and noise signal lines away from analog signals.

Parallel wires or conductors will socially form a capacitance, and two wires in close proximity will be able to capacitively couple the signal on one wire to the other, especially for high frequency signals. Therefore, we need to keep signals with high operating frequency and strong noise as far away as possible, and students need to have a low-noise alignment.

PCB ground is not ideal

The "ground" on the PCB is not an ideal conductor. Be careful to keep noisy areas away from signals that need to be quiet. We should make the ground as large as possible (as low impedance as possible) to carry the flowing current. Whenever possible, place the ground layer below the signal lines to reduce wiring impedance.

Size and number of vias

Through-holes have inductance and resistance. If you need to run wires from one side of the printed circuit board to the other and require low inductance or resistance, you can use multiple via holes. Large through-holes have low resistance, which is especially useful when using grounded filter capacitors and high current nodes. You can use a through-hole sizing calculator to calculate through-hole parameters.

Using PCB Heat Dissipation

Place extra copper around surface mount components to provide additional surface area for more efficient heat dissipation. The datasheets for some devices (especially power diodes and power MOSFETs or regulators) will explain how to use the PCB surface as a heat sink.

Heat Sinks

Vias can be used to move heat from one side of the PCB to the other, especially useful when the PCB is mounted on a heatsink on a chassis where we can carry out further enhancement of heat dissipation. Larger vias are more effective than smaller vias in transferring heat; multiple vias are more effective than one in transferring heat and by lowering the operating ambient temperature of electronic components. Lower working as well as temperature control helps students to improve the reliability of the management system.

Wiring and mounting hole distance

On PCBs, it is important to leave enough space between wiring or large floor areas and mounting holes to avoid the risk of electric shock. Soldermask does not allow for reliable insulation, so be sure to pay attention to the distance between copper and any mounting hardware.

Thermal Components

Thermal components must be kept away from devices that tend to generate heat. Thermocouples and electrolytic capacitors are both sensitive to heat, so the proximity of a thermocouple to a heat source can affect temperature measurements, while the proximity of an electrolytic capacitor to a heat-generating element can shorten its life. The main components that generate heat are bridge rectifiers, diodes, MOSFETs, inductors and resistors. The amount of heat depends on the current passing through these devices.