Archive of the former Yahoo!Groups mailing list: Homebrew PCBs

Sweet!

Here's a tip: you know the track-to-track spacing is 20 mil (you did say
10/10 pattern, yes?). Given that, you can calculate the actual DPI of
the photo (about 4300 dpi for the spot I was measuring). Also measure a
track, and you can compute the actual track width (about 9.2 mil in some
spots, 7.1 in others).

But simply measuring pixels-of-copper vs pixels-of-space should
tell you how close to "perfect" you are.

Your ohms are a little high, some things that might cause that:

∗ pinholes cause "necks" in the copper which add resistance

∗ cleaning/scraping/sanding the copper might thin it somewhat

∗ thinner traces on average would increase it

If you just go by the ohms ratio, it says your average trace width is
18/23 ∗ 10 = 7.8 mil, which sounds close enough.

Did you measure the high ohms between the two tracks?


Also, if you have a flatbed scanner, they're often useful for
high-accuracy PCB scans.