Chapter 7
Autorouting and Autoplacement
7-4
ni.com
connections. 10 prioritizes parts with the highest ratio of
connections to total pins. A high part pin factor value usually
results in a better distribution of nets than a low value. However,
high values may cause excessive placement area fragmentation on
high-density layouts by placing small parts prematurely and
preventing you from placing larger ones later on.
•
Segment Fit
—Use to control the extent to which the autoplacer
puts parts with equal lengths side by side. Placing parts with
similar lengths beside each other results in neater and more
professional looking board layouts. It may also improve the
routability of the board by aligning the parts with bus connections.
However, for high-density boards with few bus connections,
aligning parts with similar lengths will not necessarily produce
better routing results. Enter a number from 0 to 10. If you enter 0,
there is no segment fit preference, so the autoplacer will not place
parts with similar lengths beside each other. 10 indicates a strong
preference for aligning parts with equal edge lengths, so the
autoplacer will place parts with similar lengths beside each other
whenever possible.
5.
In the
Parts
area:
•
Part Rotation Mode
—Determines how much the autoplacer is
able to rotate through-hole technology parts when placing them.
In general, when you restrict part rotation, you simplify your part
placement, consume less CPU time, and create a layout that is
easy to change later. However, when you choose unrestricted part
rotation, you may end up with a much more efficient board layout
than you would get with no part rotation. Select one of:
None
, for
no rotation;
90 Deg
, for 90 clockwise rotation of all autoplaced
parts;
0 or 90 Deg
, to have parts either not rotate, or rotate
90 clockwise;
90 Deg Steps
, to have parts rotate either 90, 180, or
270 degrees clockwise.
•
SMD Mirroring
—Lets you place surface mounted devices
(SMDs) on both the top and bottom sides of a board and relax the
part spacing. You can place SMDs on both the “parts” and the
“solder” sides of your boards using mirroring mode. Select
Yes
to
allow mirroring of all SMD parts or
2-Pin Parts On
ly
to allow
only SMD parts with two pins to be placed on the solder side of
the board.
