EMC vs EMI

EMC: Electromagnetic Compatibility, the ability of a product to coexist in its intended electromagnetic environment without causing or suffering functional degradation or damage.

EMI: Electromagnetic Interference, a process by which disruptive electromagnetic energy is transmitted from one electronic device to another via radiated or conducted paths (or both).

FR4_Flame Retardant 4

A standard epoxy-glass PCB material.

Advantages

~ It meets the requirements of Underwriters Laboratories UL94-V0, which exhibits flammability characteristics that are self-extinguishing.

~The cheaper alternatives have higher dielectric losses at high frequencies.

~ It absorb more moisture

~ Provide less strength and stiffness.

~ Assuming a rise/fall time >1 ns, trace lengths up to 10 inches can be supported for data rate of 150 Mbps.

Minimum Trace Width

As a general rule of thumb, the minimum Route Trace Width is 1.0 mm/A.

For a 1.0 oz/ft2 of copper thickness which is commonly applied on most applications.

But if the parameters change, Used a PCB Trace Width Calculator to achieved a trace width that can handle a certain amount of current.


recommended site:
http://circuitcalculator.com/wordpress/2006/01/31/pcb-trace-width-calculator/
http://www.mcuexamples.com/PCB-Trace-width-calculator.php

it requires several parameters, including the operating temp range, maximum current which will flow through the trace, copper thickness, etc.

EMC model elements

A Noise source, a source that generates an electromagnetic perturbation,


A victim (sinc), an electronic device that receives a perturbation which causes dysfunctionalities,


A coupling path, a medium that transmits energy from the noise source to the victim.

Voltage Isolation Requirements


Table B: Basic and Reinforced Isolation Requirements
Common differences between basic and reinforced isolation requirements for various standards.
See specific standard for your system as requirements may vary slightly.




Safety Extra-Low-Voltage—A voltage less than 30 VRMS (60 VDC)


Hazardous—A voltage greater than 30 VRMS (60 VDC)

Basic Insulation—A single-level of protection against electric shock.
See Table B.

Reinforced/Double Insulation—Two-levels of protection against electric shock.
See Table B.

Creepage vs Clearance

Creepage is the separation between two PC board solder eyes as measured along the surface of the board.
Clearance denotes the shortest distance between two conductive parts as measured through the air.





Artwork by Melinda Vaughan, National Instruments.

Pollution Degree

It is the end environment in which an end system is used. Table 1 summarizes the different pollution degrees.


Pollution Degree 1: No pollution or only dry, nonconductive pollution occurs. The pollution has no effect.


Pollution Degree 2: Normally, only nonconductive pollution occurs. Temporary conductivity caused by condensation is to be expected.


Pollution Degree 3: Conductive pollution or dry nonconductive pollution that becomes conductive due to condensation. This is to be found in industrial environments or construction sites (harsh environments).


Pollution Degree 4: The pollution generates persistent conductivity caused by conductive dust, rain, or snow.


Table 1 lists pollution degree definitions.

(AN583)add table 1