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 Experiences in PCB Design Flows 

Last post Tue, Dec 17 2013 8:31 PM by ScottCad. 1 replies.
Started by yf1990 18 Nov 2013 06:32 PM. Topic has 1 replies and 761 views
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  • Mon, Nov 18 2013 6:32 PM

    • yf1990
    • Not Ranked
    • Joined on Tue, May 28 2013
    • Saint-Etienne, Loire
    • Posts 5
    • Points 170
    Experiences in PCB Design Flows Reply

    Hello everyone,

     

    I would like to get some advice from experienced users (professionals or regulars) in PCB Design flow, especially in complex PCB boards.

    I already made PCBs, following the "basic" design flow as shown in this picture :

     

     

    But now I'm starting to make larger PCBs which are more complex, and I have some questions in the PCB Design step (red rectangle of the previous picture), especially in the "Trace Routing".

    For example, I draw the schematics of a complex board and do the simulations, then I design the Layout to finally have something like this :

     

     

    And I wonder to know the "Correct Flow" to design the layout correctly :

    After placing the components, should I start with routing the "signals nets", and then routing the "Power nets VCC_5V, VCC_3.3V, ...", and finally do a ground plane with all GNDs ?

    Or is it necessary to route all the nets at the same time, hoping having something correct ? 

     

    Thanks for your help !

     

    Yoann 

     

     

     

    • Post Points: 20
  • Tue, Dec 17 2013 8:31 PM

    • ScottCad
    • Top 50 Contributor
    • Joined on Sat, May 26 2012
    • Roswell, GA
    • Posts 191
    • Points 3,145
    Re: Experiences in PCB Design Flows Reply

    Hello, The biggest challenge most PCB designers face on larger boards that contain many nets is laying out the board so there is minimal crossing of ratsnest. I have designed many boards both large and small and typically placment of components to minimize crossing nets is about 60% of the work load.

    The actual routing is the easy part really. It is kind of like joing the dots in an old game. The routing of any net can go very smooth if the placement is done well.

    For power and ground nets you have to consider a little more. Looking at your design you should consider how many layers the board will span. If it is a 4 layer board you could use the inner layers for power planes or trace routing too so in general the routing of power and grounds on larger boards comes down to how many layers the design will need to route all the traces.

    On a multi layer design with inner planes available most designers will fan out component leads for power and grounds and then seed a
    suitable via to the planes. When all the power and grounds are routed in normal routing of the signal nets would be the next step.

    There is not really a right and wrong way to go about it, Key thing would be to look at the placement and see what will work best.

    Main things to consider in advance are.

    Component Count
    Physical Board Size
    Layer Count
    Placement of Parts
    Routing
    Manufacture

    Hope this helps

    Scott

    • Post Points: 5
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Started by yf1990 at 18 Nov 2013 06:32 PM. Topic has 1 replies.