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I´m relativ new to PCB designing and therefore I have two questions. I started to design a simple 1-Layer PCB with a circular shape. In the Internet I found that a wire must not be "too long" elsewhere I have to use a wider wire.

1-Question 1: In my case I have + and - close to each other and then a wire that goes across the entire circle to link them. The radius is 20 mm with 100 mA Current, thikness 35µm. Is 0,3 mm for the wire enough? I used this calculator: http://circuitcalculator.com/wordpress/2006/01/31/pcb-trace-width-calculator/

2-Question 2 When I want to connect a Component, should I go directly or use a 45° ? I hope the pics can clarify my questions

enter image description here

I find always IPC-610A Norms but when I google them they cost too much for a student :(

I hope that my questions are clear. I´ll be happy with any suggestion I get :)

Thank you in Advance

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    \$\begingroup\$ #2 is better, from a manufacturing point of view. You want to avoid acute angles because of acid traps. \$\endgroup\$
    – Lior Bilia
    Commented Mar 24, 2016 at 10:24
  • \$\begingroup\$ Thank you for your answer :) An Electronics technician told me once you should not make a 90° angle after a long wire, in my case I have a circular wire with 70 mm, so there won´t be Problems using Proposition 2? \$\endgroup\$
    – sofiane1925
    Commented Mar 24, 2016 at 10:58
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    \$\begingroup\$ The 90° angle is an old myth that keeps staying alive. If it's true, then you can't use a connector, hole mounted components, or a via. Obviously all of this works well even in high speed designs. \$\endgroup\$
    – pipe
    Commented Mar 24, 2016 at 13:21
  • \$\begingroup\$ @pipe It is not a myth, it was a real thing and was very critical. Nowadays it's less risky to have 90 degree angles or smaller, but it is still not good practice. There are ways to minimize these 90-degree angles, like teardrops. Many real professionals have been using those since the invention of PCBs to avoid the issues with trapped etchant \$\endgroup\$
    – DerStrom8
    Commented Mar 24, 2016 at 13:37
  • \$\begingroup\$ In general, the narrower the trace, the more you need to worry about acid traps. But I definitely recommend you avoid acute angles and use teardrops just so other people don't question/comment on your design. It is easier to add them than explain why you didn't. \$\endgroup\$
    – user57037
    Commented Mar 24, 2016 at 16:13

2 Answers 2

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In regards to question 1, I use this calculator to determine a general recommended trace width: http://www.4pcb.com/trace-width-calculator.html . It is based on IPC2221, which is the international standard for PCB design.

In regards to question 2, definitely use proposition 2. As Lior Bilia mentioned, you should always avoid acute angles as they can act as acid traps, which will cause deterioration over time. If acid is trapped it'll eat away at the copper trace potentially causing issues down the road. Keep it head on, and use the teardrop feature (shortcut T-E) to round off the 90-degree corners where the trace meets the pad. This ensures that no acid can be trapped, and is just good practice.

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  • \$\begingroup\$ Acid traps are no longer a problem, PCB manufacturing technology has moved away from that. \$\endgroup\$
    – pipe
    Commented Mar 24, 2016 at 13:24
  • \$\begingroup\$ Thank you for your suggestion and for the calculator, I think i´m safe with 0.3 mm. For the tear drops I googled itand it seems that it´s used with Drilling so for THT pads. I forget to say that I only have smd components (due to manufacturing price later if I want a sample). So Teard drops is to be used with tht, right? \$\endgroup\$
    – sofiane1925
    Commented Mar 24, 2016 at 13:29
  • \$\begingroup\$ @pipe So does it means that I can use configuration 2 without worrying about the length of my wire? \$\endgroup\$
    – sofiane1925
    Commented Mar 24, 2016 at 13:31
  • \$\begingroup\$ @pipe You are correct in that PCB manufacturing has come a long way and most do not use acids, but it is still good practice to avoid acute angles nonetheless. Some manufacturers, especially cheap Chinese ones, may still use etchants so it's better to plan for the worst case. It's just good practice. \$\endgroup\$
    – DerStrom8
    Commented Mar 24, 2016 at 13:32
  • \$\begingroup\$ @sofiane1925 no, you are not correct. Teardrops can be used on any pads (TH or SMD) as well as where two traces meet in a "T" or where a trace necks down. Here is the dialog from Altium for adding teardrops: s27.postimg.org/g55fbvqab/Teardrops.png . I mentioned the shortcuts, but seeing as you're new to Altium I realize you might not know what that is. Pressing "T-E" is equivalent to opening the "Tools" menu and selecting "Teardrops". Whenever you see an underlined letter in a menu title or menu item name, you can simply type the underlined letter and it will select that item. \$\endgroup\$
    – DerStrom8
    Commented Mar 24, 2016 at 13:35
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The choice between both prepositions depends on what kind of trace this is and whether or not you intend to etch the board yourself or have it manufactured. If it's a simple DC line, with no particularly sensitive signal and you use a board manufacturer: GO nuts, angles don't matter that much.

If you're dealing with any kind of digital signals or any RF stuff, you have to keep in mind that what you drew is essentially a stub. If that's a foreign term to you: stubs are like discontinuities in your trace impedance, if you'd have to translate it to water in a tube, what you're doing is making the water go around a sharp bend, which creates turbulence. You probably already know this "electrical turbulence", just look at all the ripple and ringing on your typical scope trace.

General rule of thumb when you lay out your traces: imagine you're laying out pipes which carry water and you want as little turbulence as possible. There's a BUNCH of scenario's the turbulence won't make any difference, but it's a nice way to think. A great signal integrity expert once said: BE the signal!

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  • \$\begingroup\$ Thank you for your answer. I deal with normal DC signals, two Condensators in parallel and bunch of resistors and other basic components. Like I said basic PCB with no RF or something that must keep its Integrity (Thank God). Just Voltage and current that must be delivered to all components. Only thing the Plus goes across the circle, and everytime I must have a 90° to connect components. That´s what I feared, to have electrical Problems after a while (heat or Stress ...). My PCB must run for two weeks in the Lab to be validated so I can´t really pass of contraints. I hope it´s clear \$\endgroup\$
    – sofiane1925
    Commented Mar 24, 2016 at 14:09
  • \$\begingroup\$ I don't exactly understand why you need a 90° to connect your components? But anyway, I think you're fine either way. If it's your first realy PCB and you haven't bitten off more than you can obviously chew, you can get away with a crapload of bad practises. About the validation: will the environment be particularly hot? If not, refer to what I've said before: you can get away with A LOT. \$\endgroup\$
    – ByteMe
    Commented Mar 24, 2016 at 15:13
  • \$\begingroup\$ I don´t need 90°, I only want to have a fluid circulation of current, like you described it with pipes and water. For the environment I have no idea. The idea is to conceive a PCB Board that works under "all" circumstances, and not only a specific one. \$\endgroup\$
    – sofiane1925
    Commented Mar 29, 2016 at 7:00
  • \$\begingroup\$ A PCB that works under all possible circumstances is not really possible. You can make something that will be great for hot environments, you can make something that will work on the north pole or you can simply make something for room temperature(however arbitrarily you may define that). When designing without specific constraints: try to follow best practises, the moment you hit a problem (size constraints or what have you), most of the time you can make the trade off and go for whatever is practical. Best practise in your case is option number 2, because you are making a 90° bend anyway. \$\endgroup\$
    – ByteMe
    Commented Mar 30, 2016 at 14:27

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