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4 Layer PCB First Time

zquinn3

 Hi Guys,

 

I am new to both OrCAD/Allegro and 4 Layer PCB's. I'm having a tough time using the Spectra auto router to properly place via's in my design. Do I need to make and specify special via's when creating a multilayer board. I looked in costraint manager, and the default via doesnt quite look right.

 

Any advice would be great - Thanks so much! 

  • Hossein1357

     If you are new to Capture I recommend you to go to Capture Help-> Learning OrCAD Capture first. If you have some experiences with capture and only new to Allegro, then you can start with Allegro tutorials which you see its folder in prograqm menu of Windows start. You can use available via or create your own one according to your manufacturer/board specification. Anyway, after creating your own via using Pad Designer, you need to specify its path in Allegro.Go to Setup-> User Prefrence->paths in Allegro PCB and give the directory for pads, shapes and symbols in Paths->Library->padpath & psmpath. Then, you can set the via which Router uses in Setup->Constraints->Physical. Select All Layers from Physical Constraint Set and then you can select via for your routing layers.

    Hope this will help

    Hossein

  • zquinn3

     Hi Hossein,

     

    Thanks for those tips. I have made new via's, and they are imported into Allegro correctly. I have told "Constraint manger" to use certain via's for certain nets, but I dont believe this is happening properly. For example, I have a 3.3V net that run across the length of my board. If I drop a via (connecting my top layer to my 3.3V plane) should'nt this rat disappear and show as "routed"?

  • zquinn3

     Is the attached the proper way to make a via connecting Top, Bottom, and a plane called "power"?

  • Hossein1357

    You should be sure that you have defined power plane in Setup->Cross-section and also defined an outline for it. To define Power plane go to Setup->Outlines->Plane Outline. There, you can assign nets to your layers as well as voltage to them, before closing the box - take care not to close the box!. - draw the shape in a plane. This way you can divide your plane to various Power nets -+3.3V, +1.8V,..- Be sure to place components of the same voltage in an specific area then you can draw a plane in that are and assign that power net to it.  

     

  • VincentS

    This is how I make vias and they can be used with any stackup :

     

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