Another PCB Fab Thread

Does that make you an older Brit? I don't do much pcb design, but I find mil sizes for tracks nice. But for everything else in pcb design, mm is the only way - it is the standard unit for parts, boards, holes, thicknesses, etc.

Yes, I do as much as possible. The problem comes from the small differences when using convenient sizes rather than exact equals. For example trace and space in mils are low, often single digit numbers, 6/6 is not uncommon. In metric that would be 0.1524/0.1524 which I would round down to 0.15/0.15 which helps in routing with many metric parts (aren't they all metric?) This should be perfectly manufacturable on any 6/6 process. Many PCB vendors check the design files with a program which flags many errors. So standardizing on metric would be big help.

That's a *big* problem with unit conversion. Inch to metric always converts exactly and with few additional digits because 1 inch = 25.4 mm. But 1 mm = 0.03937007874016... inches. The layout program I use internally uses nm because of this problem. Unfortunately it only allows mils to be used for trace widths.

I'm fine with giving up Mils for trace width/space. I'd happily give up ounces for thickness too. 1 oz = 0.035 mm. Is that really so hard?