Go Down

Topic: Questions and questions to make the jump from schematics to PCB (Read 1 time) previous topic - next topic

amundsen

Hello,

I have  made my first try into translating a schematics into a PCB.

I'd be interested in having comments and suggestions to improve the design. The files were made with Fritzing.

Besides the schematics, you can see a picture for the first design (with two layers) then two pictures corresponding to the two layers from latest design with a smaller footprint (please note the decoupling capacitors were forgotten in first design).

I would like to have some answers about these specific points:
1. When a trace must be connected to several components (e.g. ground) is it a good practice to put the solder point of one component in the path to another one rather than to create direct connections to each component ?
2. What about angles ? I have avoided many right angles but is it really mandatory ?
3. How close may I put a soldering hole close to the board's edge ?
4. What space should I leave between a hole to tie the board with a screw and a hole for soldering ?
5. May I put traces under ICs or IC sockets ?

Thank you in advance.


jtw11

Quote
1. When a trace must be connected to several components (e.g. ground) is it a good practice to put the solder point of one component in the path to another one rather than to create direct connections to each component ?


Watch this thread re point 1. http://arduino.cc/forum/index.php?PHPSESSID=2b7d9401741b53072561456f5c04f041&topic=141589.0

amundsen

I understand it's important to have a star grounding scheme to avoid ground lifting but in other situations may I daisy chain components or should I avoid it too ?

retrolefty


I understand it's important to have a star grounding scheme to avoid ground lifting but in other situations may I daisy chain components or should I avoid it too ?


Daisy chaining the ground side of lots of push buttons is OK, also for a string of LEDs it shouldn't be a problem. It's high current drawing devices and anything wired to analog input pins that really should have separate ground returns to a single 'star' point in your power distribution system.

Lefty

ivanseidel

1. When a trace must be connected to several components (e.g. ground) is it a good practice to put the solder point of one component in the path to another one rather than to create direct connections to each component ?
Good Question =]

2. What about angles ? I have avoided many right angles but is it really mandatory ?
Avoiding RIGHT angles is always mandatory for me, but using "45" degree angles is always good, but, not better than curve lines. But, if you search for designs, curved lines are used a lot on HIGH power circuits (so that current doesen't creates a joule effect on corners, and get hot), and in HIGH speed communication protocols, like the USB (notice on the arduino DUE, there is a "wave" made with the D+ and D-, pin where data from usb comes and goes).
I use without any problem 45 degree angles (also known as "chamfer"?)

3. How close may I put a soldering hole close to the board's edge ?
This depends on each company.  Itead specify a minimum of 1mm (if i'm remembering well), from any hole/cooper/anything to the board edge... keep in mind, that this is something to "prevent" future problems like wear on the edges.

4. What space should I leave between a hole to tie the board with a screw and a hole for soldering ?
Remember to things on this:
The hole of the screw, and also the HEAD of the screw... put a margin of 2mm and everything is fine...
Also, remember this: If you use a power plane on the bottom of VCC and one in the top of GND, then BE CAREFUL to remove all the cooper around the hole, so that if the screw scratches the solder mask, the screw will not "connect" the circuit with VCC and GND...

5. May I put traces under ICs or IC sockets ?
Shure! just remember to follow the company guide lines (specifications). Itead needs an "8mil" minimum trace width, and 8mil minimum relief (distance from anyother thing). If, the trace can pass between two pins of the IC, and keep that minimum 8mil, it's ok =]

Go Up