We want to extract BF3 and we would also would like to know the capacitive coupling to conductors near BF3. By requesting a "proximity net" we are telling NETEX-G to find any metal that intersects the expansion region, grab it and collect it into a single net -- which is called in the output proximity_Net0. Normally any field analysis tool will "ground" all conductors in the proximity net to calculate capacitance.

Extract by Node Name - I entered BF3. NETEX-G will find the net that BF3 sits on and extract that net.

Proximity - I checked proximity net and selected a file name BF3+prox.txt. This will contain the net associated with BF3 and the proximity_Net0 net.

Expansion Distance - I entered .250 (mm). So my selected net will be swelled up by .250 mm on all sides and then all of the other nets will be examined

Results

Two files will be generated. The file called proximity_test.txt contains all of the nets that were isolated in the design. (there were 280 separate nets in this package.)This can be useful for some applications but for our full wave analysis it is too much data. The file called BF3+prox.txt which was created by the extract directive contains only two nets: The net associated with BF3 and the proximity net.

Here is an excerpt from the BF3+prox.txt file:

LIBRARY BF3+PROX_0.NTX unit:MM grid:1000000
NET Net77  C3 4240000 21260000 3  BF3 6820000 17420000 1
BOUNDARY 3 0
3806140 22123520
3806632 22117263
3808098 22111159
3810500 22105360
.
.
6191258 19088607
6192489 19104250
ENDEL
ENDSTR
NET Proximity_Net0
BOUNDARY 1 0
6862454 17772668
6861690 17762960
6862613 17751227
6865361 17739784
6869865 17728911
6876014 17718876
6883658 17709926
.
.
.
ENDEL
ENDSTR

Notes:

Line 1 gives the database units and grid resolution. Divide the coordinate integers by 1000000 to get MM.

Line 2 is the requested net. It has an arbitray net name, Net77 since I did not enter any net labels. It also indicates that nodes BF3 and C3 are touching this net (C3 is on the bottom; you can tell by the stackup number 3.)

Line 3 starts a conductor boundary. The 3 following the boundary indicates it is on stackup layer 3 (the bottom). A boundary is closed with the ENDEL statement.

If a net is fully routed (i.e. it starts on the top and ends on the bottom of the package) it must have at least three boundaries.

the proximity net however many have as few as 1 boundary and there is no real upper limit to the number of boundaries in it.

NET77 and the various pieces of conductor that intersect it's expansion region.

Next Up: Neighbor Nets ....

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