SPECCTRA Routing Concepts

Router is neutral

• Only performs to meet constraint controls
• Define clearly all attributes for every net
• Quantitative reporting rather than visual review confirms route quality

Orthogonal routing

• All routing is based on Manhattan Lengths
• Mitering is post-route

All routing should be done simultaneously

• Pre-routes can be protected
• Optimum - no protected routing to allow max flexibility
• Critical and priority nets controlled by routing parameters

Preferences for specifying routing parameters

• Nets by Class
• Net individually
• Two-point connection (fromto)

Nets by width

• Can control width of segments (fromtos) in net

Directionality

• Alternate horizontal & vertical on adjacent routing layers
• Can affect how horizontal & how vertical

Power/ground fanout to planes

• Split planes
• Via types
• Decoupling caps
• Lengths of power/ground fanout to plane
• Via sharing

Blind and buried vias, Microvias

• Via-in-smd, strategies
• Techniques and tools

Via reduction

• Can specify total vias per net
• Can specify max vias per fromto

Recommended algorithms for smd designs

• Specify clearance between shielded net and shield
• Specify width of shield
• Shields and length controls cannot be simultaneously spec'ed for a net

Crosstalk control

• Same layer - adjacent net
• Adjacent layer - Z-axis parallelism
• Parallelism - geometric
• Noise coupling - true accumulated voltage without using models

Routing tradeoffs to modulate

• Directionality
• Vias
• Crosstalk
• Length

Diff pairs

• Same layer
• Adjacent layer - not yet

Analog routing

• Analog - yes
• RF - no

Daisy-chain (ECL) style routing

Ordering options

• Router does not consistently choose 'shortest-best' path
• Order class or net by ref des only
• Order class or net by ref des and pin
• Cannot approximate order - must be exact
• By source and termination only - can have multiple terminations

Split topology

• Can be specified as single daisy-chain

Stub

• Two vias required for no stub
• Small stub preferred

Nets by layer

• Can turn off outer layer routing
• Router will still automatically fanout smd to vias
• Can control maximum length to via for nets that don't route on outer layer
• Must explicitly assign specific layers for routing

Length control

• Min and max by net
• Min and max by fromto
• Matched nets or fromtos within a tolerance
• Cannot specify relational lengths as a variable
• Target value vs percent of Manhattan Length
• Use Manhattan Length as a sensitivity control
• Short, shorter, very short
• Apply max Manhattan Length to all nets

Clearances

• Specified edge-to-edge
• Can specify between different objects
• By layer
• Relational - class-to-class
• Class-to-itself
• Class-to-other

Shields

• Shield net is power net
• Open or closed segment - one via per segment

Mixed technology routing

• Special capabilities exist

Manufacturability management

• Built-in during routing setup

Testpoints

• Center to center spacing - not gridded
• Can use thru-hole pins
• Single-sided or clamshell capable
• Types of testable vias
• Full reporting - one per non-power net