As I managed to do create a holly grail of electronics - double sided PCB without any vias, only remaining step was to get it made.
Usually this would consists of uploading board gerbers to OSH Park and getting payment sorted out. However, this time I was greeted with error: "I can't find a drills file". Mind you, this was expected since I really didn't have a drill file, but unfortunately this wasn't a warning I could skip. So I contacted support.
I really didn't expect any quick answer since I raised ticket on December 31st after 16h PST. Surprisingly I got the solution almost immediately. It wasn't possible to upload design without drills but Dan (yep, Laen doesn't handle support any more) suggested a file with drill locations all falling outside of board. Their filtering process would then remove those as invalid and my drill-less board would be ready for manufacturing.
While this solution was acceptable for one-off job, it got me thinking whether there was something a bit more elegant and less error-prone if I create some bigger board in the future. To solve it properly I had to have a drill file without any drills. To the Excellon specification!
With a bit of testing, I got to the minimum of content that OSH Park parser would still consider a valid drill file. It is essentially just defining one drill tool, selecting it for work and then finishing script without ever drilling a hole:
M48
INCH
T01C0.0394
%
T01
T00
M30Empty drill file is available for download.
Haha, generating profit out of drilling with minimum effort, perfect optimisation.
If there are no drills, then there’s no bottom layer either, I assume. Either that, or you’ve put two completely independent circuits on each side of the board and are using double-sided reflow. Or am I missing something?
All components were on a single side (top). It just ended up that I was able to get all interconnects without going to the other side. On other side I did have some copper but just for decorative purposes (golden bear) so bottom signal layer was present.