Platform forum


JMFernandez , 04-13-2016, 06:50 AM

I have a question about GRIDS. I have been watching the videos of Schematic and hardware design course and the Switching power supply course. The recommendation is to use a grid of 0.1mm as a general rule. But what happens when you need to do a non-standard footrpint with dimensions like n*0.001mm or create a pcb with a specific shape?
What I do is to change the grid to create these strange shapes or components and use the 0.1mm grid always I can. I use 0.1mm grid to trace the tracks, place components and as I have said, I use 0.1mm always I can. Is this the right way? Any recommendation?

Thank you in advance!!
robertferanec , 04-13-2016, 09:04 AM
I use custom grids. Is this what you are looking for? See: Altium Designer – Define a Custom Grid under BGA
JMFernandez , 04-13-2016, 10:21 AM
Hello. Thank you for your help. I just asked which is the best form to make, for example, a footprint where the dimensions have values (n*0.001)mm. I mean, I should use a grid of 0.001 to draw this footprint and then, when I am doing layout, use a grid of 0.1mm? And, if the pcb has an irregular shape and some dimensiones have values (n*0.001)mm, should I use a grid of 0.001 to draw the pcb outline and then I can change grid and use 0.1mm to trace the tracks and place the components? As I am new in pcb design, I do not know if I can use different grids without problem.
mairomaster , 04-14-2016, 02:34 AM
You are pretty much doing the right thing.

Most of the time if you have a footprint with strange metric dimensions, it would be because it is designed in imperial. If that is the case, you can switch to imperial grid when creating the footprint (the key short cut is Q) and use mills instead of millimetres. However if the footprint just happens to be strange and designed in metric, you can just switch to a finer grid (often times 0.025 is enough but feel free to go lower than that). I would advice to stick to the Altium default grid sizes when possible and not use too fine grid if not necessary.

If you use an imperial footprint in a board which you design in metric, it should not be a problem as when you connect the pads of the footprint your cursor should snap to them (just make sure your snap is enabled), despite there centres not being on the grid perfectly.

Generally, I use 0.1mm - 1mm grid for placement of components (depending on how big they are) and 0.25 - 0.1mm for tracking (depending on how thick the tracks are). For board outline it's good to use some whole number sizes, since it just looks nice. Of course depending on mechanical limitations, you might need to use some specific number for that as well, which is not necessary a whole number in millimetres.
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