• Skip to main content
  • Skip to search
  • Skip to footer
Cadence Home
  • This search text may be transcribed, used, stored, or accessed by our third-party service providers per our Cookie Policy and Privacy Policy.

  1. Community Forums
  2. Allegro X PCB Editor
  3. How to control "Same net spacing" constraint rule value...

Stats

  • Replies 10
  • Subscribers 160
  • Views 5498
  • Members are here 0
More Content

How to control "Same net spacing" constraint rule value of overlap rate?

ichliebedich
ichliebedich over 4 years ago

Hi All

If I actvate the same net spacing rule at the analysis mode, the same nets between Via and Shape keep the distance per overlap rate.

as I know from the test, the via only applied the rule with same net shape under 50% overlap rate.

but I want to keep short net the via with shape even under 30%. (see below)

of course it is working without activating same net spacing rule, but I have to keep on the rule..

how can I control the rate value of this?

regard

  • Sign in to reply
  • Cancel
Parents
  • Lock2002
    Lock2002 over 4 years ago

    It uses the exact center of the via or pin. once you cross that it either voids or floods. So you're stuck with 50% 

    • Cancel
    • Vote Up 0 Vote Down
    • Sign in to reply
    • Cancel
  • ichliebedich
    ichliebedich over 4 years ago in reply to Lock2002

    doesn't it have any function to control the percentage? or is there other alternative way?

    • Cancel
    • Vote Up 0 Vote Down
    • Sign in to reply
    • Cancel
  • jc teyssier
    jc teyssier over 4 years ago in reply to ichliebedich

    I do not think so: it is not a percentage: if the shape reach the via origin (even if not centered i gues, make no sense in this case)  then it will be connected. If not reaching, it is voided.

    What you have to do is to modify shape boudary to englobe the via (at least via origin)

    • Cancel
    • Vote Up 0 Vote Down
    • Sign in to reply
    • Cancel
Reply
  • jc teyssier
    jc teyssier over 4 years ago in reply to ichliebedich

    I do not think so: it is not a percentage: if the shape reach the via origin (even if not centered i gues, make no sense in this case)  then it will be connected. If not reaching, it is voided.

    What you have to do is to modify shape boudary to englobe the via (at least via origin)

    • Cancel
    • Vote Up 0 Vote Down
    • Sign in to reply
    • Cancel
Children
  • ichliebedich
    ichliebedich over 4 years ago in reply to jc teyssier

    thank you I haven't notice that mechanism !  I found alternative way which modify the shape to cover the orgin like below

     

    • Cancel
    • Vote Up 0 Vote Down
    • Sign in to reply
    • Cancel
  • jc teyssier
    jc teyssier over 4 years ago in reply to ichliebedich

    Be aware that you obtain smalls acid traps at via/shape intersection now.

    • Cancel
    • Vote Up 0 Vote Down
    • Sign in to reply
    • Cancel
  • Wild
    Wild over 4 years ago in reply to jc teyssier

    I believe there is a misconception in the industry about acid traps.  Experts such as Lee Richey have been stating that Acid Traps have not been an issue since the early 2000's.  I would recommend a conversation with you fab house to double check this.

    See here for an article on this and the 90 degree bends (Taken from "Right the first time" - great read), Speeding Edge.  I also believe I have seen this topic discussed in Dr. Howard's tutorials.

    More info here: https://resources.altium.com/p/slaying-900-right-angle-bend-dragon

    I know it's an altium_crap site, but good information can also come from the "dark side: Slight smile

    • Cancel
    • Vote Up 0 Vote Down
    • Sign in to reply
    • Cancel
  • jc teyssier
    jc teyssier over 4 years ago in reply to Wild

    Well, some of my design have required/expected life more than 30 year in uncontroled environment. Some of them are for security. I can not have a  risk with acid still eating copper. And avoideing acid traps is verry easy.

    • Cancel
    • Vote Up 0 Vote Down
    • Sign in to reply
    • Cancel
  • Wild
    Wild over 4 years ago in reply to jc teyssier

    When I stared my carer at Bell Labs in 1986, we saw issues with acid traps, so I am not denying that this was a problem.  However in the late 190's - early 2000's the manufacturers that (Lucent Power Systems) we used never had issues.  This was alluded to in the articles I referenced.  I am not saying that it is not good practice to avoid the sharp corners, but rather I suggest that users talk with their fab house and not blindly follow rules that may not be an issue.  Did you read the article?

    • Cancel
    • Vote Up 0 Vote Down
    • Sign in to reply
    • Cancel
Cadence Guidelines

Community Guidelines

The Cadence Design Communities support Cadence users and technologists interacting to exchange ideas, news, technical information, and best practices to solve problems and get the most from Cadence technology. The community is open to everyone, and to provide the most value, we require participants to follow our Community Guidelines that facilitate a quality exchange of ideas and information. By accessing, contributing, using or downloading any materials from the site, you agree to be bound by the full Community Guidelines.

© 2025 Cadence Design Systems, Inc. All Rights Reserved.

  • Terms of Use
  • Privacy
  • Cookie Policy
  • US Trademarks
  • Do Not Sell or Share My Personal Information