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It can provide electromagnetic compatibility (EMC) compliance by shielding and or suppressing electrical and electrostatic emissions (reducing EMI electro magnetic interference).
READ THIS article on ground planes:
http://www.elmac.co.uk/pdfs/Lord_of_the_…
http://en.wikipedia.org/wiki/Electromagn…
A ground plane adds shielding, forms constant impedance transmission lines along the trace paths and reduces emissions and improves immunity.
Two layer boards are cheaper than 4 layer or multi layer boards so its easy and cheap to use one side of a two layer PCB as a ground plane.
READ THIS article on ground planes:
http://www.elmac.co.uk/pdfs/Lord_of_the_…
http://en.wikipedia.org/wiki/Electromagn…
A ground plane adds shielding, forms constant impedance transmission lines along the trace paths and reduces emissions and improves immunity.
Two layer boards are cheaper than 4 layer or multi layer boards so its easy and cheap to use one side of a two layer PCB as a ground plane.
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Traces on each side of the board can have capacitive coupling to each other. If the signals on one, other or both have fast voltage swings, this can couple into the other trace as noise. Putting a ground plane in between these traces eliminates this possibility, as the coupling is instead shunted to ground.
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The earth side of a circuit may have to take a large current flow - so using the whole side will prevent damage to the board if a large current does flow.