Rule category: Routing
Rule classification: Unary
This rule specifies fanout options to be used when fanning out the pads of surface mount components in the design that connect to signal and/or power plane nets. Fanout essentially turns an SMT pad into a thru hole pad, from a routing point of view, by adding a via and connecting track. This greatly increases the probability of successfully routing the board, as a signal is made available to all routing layers instead of just the top or bottom layer. This is particularly needed in high-density designs where routing space is very tight.
Auto- chooses the style most appropriate for the component technology and in order to give optimal routing space results.
Inline Rows- fanout vias are placed within two aligned rows.
Staggered Rows- fanout vias are placed within two staggered rows.
BGA- fanout occurs in accordance with the specified BGA Options.
Under Pads- fanout vias are placed directly under SMT component pads.
Disable- do not allow fanout with respect to the SMT components targeted by the rule.
In Only- fanout in an inward direction only. All fanout vias and connecting track will be placed within the component's bounding rectangle.
Out Only- fanout in an outward direction only. All fanout vias and connecting track will be placed outside of the component's bounding rectangle.
In Then Out- fanout all component pads in an inward direction to begin with. All pads that cannot be fanned out in this direction should be fanned out in an outward direction (if possible).
Out Then In- fanout all component pads in an outward direction to begin with. All pads that cannot be fanned out in this direction should be fanned out in an inward direction (if possible).
Alternating In and Out- fanout all component pads (where possible) in an alternating fashion, first inward then outward.
Away From Center- fanout for pads in each quadrant is applied following a 45° angle away from the component's center.
North-East- all pads, in each quadrant, are fanned out in a North-Easterly direction (45° anti-clockwise from the horizontal).
South-East- all pads, in each quadrant, are fanned out in a South-Easterly direction (45° clockwise from the horizontal).
South-West- all pads, in each quadrant, are fanned out in a South-Westerly direction (135° clockwise from the horizontal).
North-West- all pads, in each quadrant, are fanned out in a North-Westerly direction (135° anti-clockwise from the horizontal).
Towards Center- fanout for pads in each quadrant is applied following a 45° angle toward the component's center. In most cases, uniformity of direction will not be possible due to required fanout space already taken by another pads' fanout via. In these cases, fanout will occur in the next available direction (North-East, South-East, South-West, North-West).
Close To Pad (Follow Rules)- fanout vias will be placed as close to their corresponding SMT component pads as possible, without violating defined clearance rules.
Centered Between Pads- fanout vias will be centered between the SMT component pads.
All rules are resolved by the priority setting. The system goes through the rules from highest to lowest priority and picks the first one whose scope expression matches the object(s) being checked.
During interactive routing and autorouting.
(CompPinCount < 5).
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