Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

PCB Layout Help

  1. Mar 28, 2006 #1
    Alright, so I made my first PCB using CIRCAD '98. I went through it a couple times, found a couple overlapping traces, but I always miss something.

    I was wondering if you guys wouldn't mind taking a look at it before I send it off to be printed.



    Thanks a lot.
  2. jcsd
  3. Mar 28, 2006 #2


    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    I've never used CIRCAD, but any PCB layout program worth its salt will do automatic Design Rules Checking, which will find problems like overlapping traces. Does CIRCAD?

    - Warren
  4. Mar 28, 2006 #3
    Doesn't look like it. I went through the menu and help. Considering the last update for this program was moving from DOS to Windows I don't think it has many functions at all.

    It certainly wasn't my choice to use this program, from talking to other Engineers I've heard Eagle come up a few times. However, profs insisted that the PCB layout be constructed using this dinosaur program. Probably for the very reason that it doesn't have automatic error chcecking and other such functionalities.
  5. Mar 28, 2006 #4
    not trying to insult you but the layout is very sloppy. the fat trace comming off the collector of q1 to close to that border trace (that serves no purpose) and might not etch right, q2 is shorted. and their are design rules about when to use angles and one trace is leading off to nowhere. i'd find a book on pcb design and buy a tape mask kit and etch a few boards for practice.

    i can't find any good tutorials just this http://en.wikipedia.org/wiki/PCB_layout_guidelines

    btw that board should be 1/3 of the size it is.
    Last edited by a moderator: Mar 28, 2006
  6. Mar 28, 2006 #5

    Thanks, I just fixed those problems

    And no offense taken, actually that is exactly what I wanted to hear. I'm really not too concerned with design etiquette, I'm sure I've followed none of it, I simply need it to work. Although, I think I will take you up on your advice, I would like to be able to create a professional looking PCB. I know this first one certainly won't be the last.

    Aha; at least the size isn't my fault, profs set the board size!
  7. Mar 28, 2006 #6
    i'd just like to add some more points, when you design a pcb you have to be aware of how thick the board should be to support the weight of the components and if it will be double sided or multilayered, have a ground plane and thru hole plating. the different types of celuliod and fiberglass types. the ounces of copper per side as it dictates the width needed for high current and minimum space for proper etching. the space between traces as it relates to arcing for high voltage and crosstalk. the length of traces as it relates to things like propagation delay for digital and inductance with rf designs.

    also ic's should be all facing in the same direction, same with signal transistor , all small signal parts. the exception would be things that dissapate heat or need heatsinks.

    lots of things to consider.
  8. Mar 28, 2006 #7


    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    The most popular packages in industry are Protel, Pads, and OrCAD Layout.

    The http://www.geda.seul.org/ project has a free PCB layout tool, but I haven't used it.

    - Warren
  9. Mar 29, 2006 #8


    User Avatar
    Science Advisor
    Gold Member

    Shoot. I use to lay them out 2 to 1 on mylar using Bishop Graphics products. Only double sided however.
  10. Mar 29, 2006 #9


    User Avatar
    Gold Member

    There is no C5 on the schematic and there is one on the board. Q2 and Q3 do not agree between the board and the schematic; on the schematic R8 is hooked to Q2 but on the board it is not. There is no power supply bypass capacitor ANYWHERE on the schematic or the board. More important than obeying 'guidelines' when it comes to PCB layout. The opamp should have bypass capacitor right close to it on the board.
  11. Apr 3, 2006 #10
    If you are looking for a powerful free PCB layout program, I recommend Eagle by cadsoft. It is very powerful and not that hard to learn. The first PCB I ever made with it turned out really nice and I was impressed with the results. It also has many design rules that you can implement and doing things like a copper pour is very easy. As an example I'll attach the PCB I made. I had no experience with PCB's prior to this, and during a 2 weeks period of learning I came up with this. My technique was to route some of the more important traces and some power traces manually and then use the autorouter for the rest. After the traces were routed, I would turn and move components to prevent "spaghetti" traces and make the runs as short as possible. I also tried to make as neat as I could within my constaints, but personally functionally is more impostant than looks. It may not be up to the standards of some of the engineers on here, but I think half the battle is in the software you choose.

    Last edited: Apr 3, 2006
  12. Apr 4, 2006 #11
    Indeed, I would have much preferred to have used Eagle; I have been messing around with it recently--building my own amplifier for fun, it's gonna be huge. Unfortunatly, this was for a class and I had very little freedom.

    Anyway, thanks for you help everyone, the PCB worked out fine.
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook