I suck at placing and routing PCB's, please help improve

[Z80]

Hi all

First of all, this stuff is only a hobby for me, I don't do PCB's as a pro by any means. Occassionally I need to make a PCB at amateur level and I use Protel. Why Protel? Totally random choice, just got familiar with it.

Anyway, I realize that I totally suck at it. My PCB's look like crap, the connections are nonoptimal, critical traces run around the PCB, DRC gives errors etc. I never seem to reach a good place/route compromise. When I think I've got it, I realize that I missed some ground connection that ruins everything, or something else...

So this has to improve somehow. Either I have to take a methodological approach, either switch to another software, or God knows what else.

Please advize. Any hint, tutorial, remark would be helpful.


Thanks
Z80

 

[House_Cat]

Here is a basic approach for a hobby project layout. The same general approach would be followed for a commercial layout, with the addition of layout simulation and analysis. There is no "one size fits all" set of rules for layout - there are too many variables that depend upon the type of circuit you are routing. The following just outlines the basics that get you "in the ballpark".

A good PCB layout starts with a good schematic. Lay out your schematic so that related components are grouped logically, and interconnects are as short and direct as possible.

Next, put all the components on the PCB without connections. Use the schematic as your guideline to group them together. Believe it or not, the best PCB component layout will be close to the way your schematic is laid out. Depending on the EDA software you are using, the components may be automatically placed on the board for you when you import the netlist. If that is the case, take the time to arrange the components manually - there is NO automatic placement program that works as well as the human brain. You import your netlist to the board to give you a "ratsnest" of connection lines to assist in the following steps.

Now, look at your schematic and identify the most critical signal paths. Try connecting them manually on the PCB - move the parts around to get the best layout for both the parts and the critical signal traces.

Try the next most important signal traces. Move things around to get the best compromise. Repeat the process as you work down the list of signals in order of importance and sensitivity. Keep in mind that every signal is a complete loop that consists of the trace you are placing, and the return path through the power supply (usually ground side) connections. The idea is to keep the critical loops as direct and small as possible.

Now you can either set up your autorouter and let it do its job, or you can manually route. If you manually route, you should place all the power and grounds, then route the remaining signals. If you autoroute, you should manually place and lock your critical signal traces first. When the autorouter finishes, you will have to finish powers and grounds, plus any signals that the autorouter couldn't complete within the rules you established.

You can now do a final design rule check (DRC), and adjust anything that doesn't meet requirements.