I’m in the process of doing a layout which will have a stacked mezzanine daughter board on top of the main board I’m laying out. It will use standard 0.1" vertical unshrouded headers. So alignment of all the connector through holes is nessesary. This is a multi page schematic with extensive use of hierarchical sheets and global labels to partition the design within the same project.
I have two separate schematic symbols with corresponding related footprints created for Main board and Daughterboard. My basic quandary now is how to exactly position the two footprints so that the two boards line up in Pcbnew with the proper connectors and 3D view of the connector from the library. I have the following:
NPTH, Mechanical holes in my mainboard footprint representing the standoffs and various mounting holes including the NPTH holes for the daughterboard mounts. I did not have any reference holes in that mainboard footprint but rather manual located the connector footprints in the PcbNew layout. Since these connectors were also on my schematic they have themselves separate footprints and I need a way to make sure all three are aligned. I did it manually once and probably already disturbed them which is why I’m looking to “do it another way”.
I have an imported DXF file saved as a footprint for the daughter board but it is missing all of the drill holes as part of the import. It does have an outline and some trace information so it is still useful.I have added the NPTH mounting holes to this foot print. Having already gone through the hassle of locating KiCAD Git library connector footprints onto the mainboard PCB corresponding to the daughterboard referenced connectors. I have probably moved them during the layout so before I try to place them accurately again I’m looking if there is not a better way to do this.
There are probably multiple ways to do it with pros and cons so was just looking at some feed back for how best to do it.
Is it best to put NPTH holes/connector into both footprints and just align them in Pcbnew (albeit with double holes for the NPTH’s). I don’t know if this creates an issue or not or If it simply means I pay for a second drill hole into the air made by the first drill holes at the same location (a non issue).
At this point I’m thinking I should:
1.) build my daughter board footprint to include reference “Through-holes” for all the headers that will go on that board.
2.) build the main board footprint to include reference through holes also with Through-hole or NPTH holes that I can use to align the two boards.
3.) Finally I would have connector foot prints that I would locate using these reference holes on teh other two board prints and the 3D files would still work as they are referenced to the connector footprints and not the board footprints.
What this approach amounts to is uses duplicate reference holes in the various foot prints and using that to align the foot prints. I get a positive visual feedback the alignment is correct and I don’t have to worry about anything being shifted and not being obvious.
So this is boiling down to how best to maintain alignment between 3 different footprints in the same Mezzanine PCB design (Main board, daughter board and connector in the same Pcbnew layout).
A secondary question is I’m assuming the edge cuts should only be in the layout and not in any of the other footprints.
I’m just not to anxious to go through the process as an experiment if someone already has been through it and has a way that works. Otherwise my design is progressing well other than these types of issues.
Jim
