On 03:02 PM 19/05/2002 -0700, Embedded Matt said:
>I'm working on laying out my first board with power
>planes and I have a few questions.
>
>1. I placed an arc on the plane (my board is circular)
>to form a circle all the way around the edge of the
>board.  The idea is to keep the plane away from the
>edge of the board.  The assigned net for the arc is
>"No Net".  Is this the correct procedure for keeping
>the plane away from the edge of the board?

Yep.


>2. The arc is 50 mils wide.  Since I placed the arc
>directly on top of the board outline, I expect to get
>25 mils of clearance from the board edge to the plane.
>  In general, is that enough clearance?

Yep


>3. I have split the plane into multiple nets.  The
>tracks that indicate the boundaries are 45 degree and
>90 degree tracks.  Recall I have an arc on my board
>edge.  Because the 45/90 tracks and the arc are not
>"compatible", the tracks extend outside of the arc to
>avoid tiny slivers of plane near the board edge.  Is
>there a better way to do this?  For example, can I
>define the regions with mostly 45/90 tracks but add an
>arc at the board edge to complete the region?  Will
>the way I have done this likely confuse the board
>house?

I assume you are placing a "split plane" on the power plane layer.  Is this 
correct?  You should be. I am not sure if split planes can have arcs but 
they may well be able to do so. In which case you can use the Shift-Space 
while placing the split plane to change to arc placement mode. If you do 
want to persist with the 45 and 90 degree tracks then as long as you 
document what you have done there should be no issue.  The other method of 
making it more obvious what you are intending would be to use the 
"any-angle" track mode and place a number of shorter segments around the 
boundary of the plane pull-back arc you placed earlier.

If you are not placing a split-plane entity to make your plane split then 
you should be *unless* both sides of the split plane are the same net and 
you are really not splitting the plane but in fact attempting to guide 
plane currents.

Split planes allow section of the power plane to be at different voltages - 
is this your intention?

Ian Wilson


>I'm using Protel 99 SE sp6.
>
>Thank you,
>Matt
>
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