Voiding and Connectivity
Voiding helps designers route on the ground/power planes by insulating signal nets automatically. You need to specify the ground/power planes to provide reference planes for transmission lines. In addition, it reduces the impedance of the power/ground supply network and EM noise.
The signals going through ground/power planes are also required to route between signal layers separated by the planes.
Die-to-Component Interconnect
Die-to-Component interconnect involves fanning out all of the die-to-component interconnections and routing to the destination component pin. Depending on the technology being implemented, this routing may take on different forms:
- Routing patterns for Quad Flat Packs (QFP) and Pin Grid Arrays (PGA) are typically a triangular fanout pattern from the bond wire pads coupled with an “any angle” connection to the component pin.
- Routing patterns for Ball Grid Arrays (BGA) are typically an intricate weaving of traces through the flip-chip pin locations to an edge pattern of vias coupled with an intricate pattern into BGA ball locations.
- Routing patterns are a result of an optimized usage of routing real estate, resulting in the minimum number of routing layers.
Interactive routing is more suited for intricate routing patterns.
ECAD systems offer a host of interactive routing capabilities that you can use to semi-automatically build fanout patterns and then complete with “any angle” routing.
Through graphical representations of connectivity lines and online design rule checking, routing efficiency is easily realized as manufacturing concerns are minimized.
Die to Die Interconnect
When routing among dies, you must identify critical signals (clock, high speed buses) and route them first. Once you have routed critical signals, you can run signal analysis. Then, model the actual routed traces. You can use the new interconnect delays to verify that the timing budget has been met. Finally, you can edit the routed traces to reach the desired level of signal integrity for the critical signals.
You must specify manufacturing rules prior to routing. These rules include:
- Spacing (by layer, if applicable)
- Line widths
- Line impedance
- Legal via selection
- Blind and buried via spacing
- Min/Max stagger size
Power and Ground Vias
You must also route power and ground via connections. Depending on the type of design, you may route them before or after you route the signals. You must consider the via type (blind, buried, through) and the specific plane to which they attach.
Related Topics
Die-to-Component I/O Net Assignment
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