Hello guys first of all i want to point that i dont have any experience about eagle and i am trying to design a pcb. It will be a commercial product so it needs to be perfect. I have finished my schematic design. There is no problem about that however i have some troubles in board part as you can guess. Firstly net class specifications i made, width 12mil,drill 20mil and clearance 12mil and i got 730 errors about them from drc checking. So what are wrongs with these numbers. What are the things i should be worry about when i am arranging them. In which case i should create more than one net class why ? Also question i want to make these holes in pcb. Because i just want to put 433 mhz rf module on it. So what should i put in the schematic to use them. These are not headers right ? Also i assumed that they are not just holes which you can make from board design or are they ?
i am using arduino nano in the project and all errors come from arduino part of the pcb is there anyone who knows net class specifications for arduino ?
You can edit design rules to prevent 4000 errors about holes being too big, etc. The DRC just compares against the rules you give it. You should check your PCB fab can manage the tolerances you put in the rules, then the DRC will make sure you haven't exceeded them.
If you need a custom part (a connector is just a part), just create one - lots of tutorials about this online. There may be something suitable already in the standard libraries, but you'll have to search about.
okay can you tell me what more about clearance,drill and width i will change them but what i need to care when i am changing them is there any optimum values for them. As i said all errors come from arduino nano so is it possible to find net graph values for arduino
The are just numbers - your PCB fabricator should have a specification of minimum drill, clearance, etc that they can make. The defaults in Eagle are pretty conservative.
DRC numbers come from your board house. Most have a .dru you can download.
If you import a layout made for a board house with better capabilities (smaller minimum clearance/etc), you will likely have to alter the layout to account for that.
All these numbers are better when they are big i mean should i use their maximum value i mean what is the difference when clearence is 12mil or 13mil and also for width and drill ?
Clearance is the distance between copper at different potentials. Basically the space around all copper traces, pads, whatever, which should not have another trace/pad that close to it.
12mil seems very large for clearance. 2-layer boards seem to be mostly around 6mil clearance and 4-layer boards smaller again.
You can't drill an infinitely small hole. 13 mil is a common size for really tiny holes. You can't fit anything down that hole except plated copper. No wire will fit.
If your board house is spec'ing 12 mil width or clearance, find a new board house. Even my bargain basement board house will do 6mil.
Look at File:Edit:Net Classes. There you can specify a default width, say 10 mil wide with 10 mil clearance and 12 mil for vias. You can define wider ones, say 20 mil for power, 10 mil clearance, and 24 mil for vias. Right click on the traces and under Property select the trace type you want.
"i dont have any experience about eagle and i am trying to design a pcb. It will be a commercial product so it needs to be perfect." Work with an engineer the first time. Download the DRU file and CAM file from someplace like iteadstudio. Run the Error checking on the schematic, fix those errors. On the board, select View:Grid and set the spacing to 2 mil. On the board, use the Polygon and draw polygons around the board dimension on the top & bottom layers. Right click and Name then GND. Run the Rats Nest and see what is left to connect. You may have to take narrower traces off PCB pins to connect to wider power traces. Run the Error checking on the board. Fix those errors. Work with an engineer the first time.
I don't use net classes unless I'm also using auto routing. For 90% of my boards, I route manually and everything is in the first net class.
"the first net class" If you are designing a board from scratch, I think the only net class that shows up is the default at 6 mil. If you doing a Save As of another board and deleting/adding components and ripping up traces to re-route, then I would expect to see more net classes to choose from.
I also heard that it is not good to import an arduino lay out directly ? What do you think about that guys ? Should i use arduino nano lay out ?
It depends on what you mean.
It is usually best to just buy the Arduino and solder it onto your board. Or put header pins on your board and plug it in like any shield. You only need an Eagle library that has the footprint of the Arduino board. Element14 has a good library that covers most Arduino variants.
If you want to just copy the Arduino layout and put it into your board, there's nothing stopping you, but then you will never know if your problems are caused by an incorrect copy or somewhere else on your board.