The NC Pin DFE rule checks for the NC pin connectivity.
Component pins that are not connected to any signal are treated as NC pins. If any
routed traces are connected to these NC pins, they may become good antennas. To
prevent this problem, the designer should compulsory connect those NC pins to
ground.
NC pin existence test
Item: Enter the item name.
Component Group: Select a target component group that has NC pins.
Connected Net: Select a net group to which the component’s NC pin should be
connected.
List NC Pin: The DFE lists all NC pins.
Include One pin net: DFE consider pin which does not have any connection to
other component even if which has connection to net as a NC pin.
Figure 1.
NC pin via exist test
Via on PAD near Conner: DFE checks if via exists on the first encountered NC
pin pad from each corner side of IC. If the first encountered NC pin pad
does not have via on pad, it reports as failed.Figure 2.
Result
PollEx DFE reports component pins have no connecting
information and displays a ground pattern to which the NC pins may need to be connected.
IC (Internally Connected) pin
An IC pin is connected internally.
The state of the pin might define the internal operation or a signal
might be output.
NC (No Connection) pin
An NC pin is not connected internally.
However, if it is connected, for example, to a signal wire, internal
noise will increase.
It is therefore recommended not to connect the pin to anything, or
to connect the pin directly to the power supply or ground.
NC pins may, as an exception, be connected internally. Therefore, be
aware of this when NC pins are connected to the power supply or
ground.
The part supplier may provide what to do with each NC pin.
When there are pins with no connection, the designer can get a stability of signal
against noise by connecting those pins to ground. Usually commercial (off-the-shelf)
components have no NC pins, however FPGA or ASIC may have them.
In some cases, the designer can remove NC pin to reduce manufacturing costs, however
it is not a good practice for manufacturing or EMI. To get better effect of
component, connect all NC pins to ground.Figure 3.