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6 layer pcb stack

Rajinder

Jan 30, 2016
568
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Jan 30, 2016
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568
Hi all,
I have a coupe of questions:
i have a 6 layer pcb, the stack up is as follows

layer 1 - component (smd and through-hole) + tracking of analogue signals
layer 2 - gnd
layer 3 - inner track for digital signals i.e. spi, i2c
layer 4- inner track for digital signals i.e. spi, i2c
layer 5 - power i.e. 5v and 3v3
layer 6 - tracking low frequency signals - led driving

ideally i wanted to layer 4 as another gnd layer but couldnt do this due alot of componenets that needed to be tracked.

Please could some one explain if i need to stitch areas of copper to 0v from layers 4 and 6?
please could someone explain the difference between 1oz and 2oz copper i.e. what it means in terms of pcb design

thanks in advance
 

(*steve*)

¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
Moderator
Jan 21, 2010
25,510
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Jan 21, 2010
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25,510
1 oz copper is 1 oz per square foot. 2 oz copper is twice as thick and can this carry twice the current.
 

AnalogKid

Jun 10, 2015
2,884
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Jun 10, 2015
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2,884
Thicker copper has lower resistance for the same trace width, and can carry more current for the same temperature increase. There are online calculators for this. It is not a linear relationship because thicker copper also has more overetching or etch undercut, which decreases the effective cross-sectional area.

Thicker copper also has a different characteristic impedance for stripline and microstripline designs, and there are online calculators for this. In general, very high frequency designs such as gigabit Ethernet perform better with thinner copper layers, such as 1/2 oz.

ak
 
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