Author Topic: Design rules and gotchas for PCBWay?  (Read 1442 times)

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Offline paulca

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Design rules and gotchas for PCBWay?
« on: February 13, 2018, 01:25:37 am »
So I'm building up to my first board and was wondering if anyway has any tips for design rules for PCBWay to remain within their tolerances or other gotchas.

I am using Kicad.
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Offline 8086

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Online rx8pilot

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Re: Design rules and gotchas for PCBWay?
« Reply #2 on: February 13, 2018, 12:52:33 pm »
For the most part - they will tell you if something violates the rules - as a nice safety net.

The rules posted above should allow you to stay out of trouble. I have done 5/5mil traces and 10mil drills on quite a few designs the PCBway fabbed. No problems. 40mil text is generally rather sharp, could probably go quite a bit smaller if needed.
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Offline paulca

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Re: Design rules and gotchas for PCBWay?
« Reply #3 on: February 13, 2018, 06:54:39 pm »
To be honest the whole "mil" thing had me confused for a while.  Because we tend to talk in millimetres and sometimes even call them "mils" or "millis".

I don't think my board comes close to the capabilities.  I just used the KiCad defaults.

I have to take another run through it and double check footprints against actual components and tidy up the default silkscreen on the default footprints, it looks like a mess.
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Offline fourtytwo42

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Re: Design rules and gotchas for PCBWay?
« Reply #4 on: February 13, 2018, 07:06:11 pm »
I don't think my board comes close to the capabilities.  I just used the KiCad defaults.
Be careful to check, I think the default T&G is to small and also the default via annular ring is to small.

A mil is a thou :)
 

Offline martinator

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Re: Design rules and gotchas for PCBWay?
« Reply #5 on: February 13, 2018, 07:20:29 pm »
Anybody have any recommendations for Kicad defaults?
It's not easy trying to work out what to use, those trace calculators don't make any sense to me and the internet doesn't offer Kicad specific suggestions that I can just plug in.
 

Offline marshallh

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Re: Design rules and gotchas for PCBWay?
« Reply #6 on: March 14, 2018, 01:38:40 pm »
Increase the internal clearances, especially on polygons to traces (assuming 4 layer)

For example, if they quote 6mil trace/space on the internal layers best up to 7 or 8 if possible. I saw yield improvements after I did this (we're talking about 4-5 units per 100)

Avoid running small traces next to large polygons or pours. Hairline shorts can occur, increase the clearance slightly if possible.

No pcb company is perfect, I've had egregious failures with PCBway just like every other shop. But honestly as PCBway uses different production lines or outsources to different fabs (not sure which it is) the exact fab you get will depend on  luck of the draw.
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Offline Bassman59

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Re: Design rules and gotchas for PCBWay?
« Reply #7 on: March 14, 2018, 03:06:20 pm »
Anybody have any recommendations for Kicad defaults?
It's not easy trying to work out what to use, those trace calculators don't make any sense to me and the internet doesn't offer Kicad specific suggestions that I can just plug in.

I honestly don't remember what Kicad uses for default design rules, but the thing is that there's no such thing as a universal default.

Your design rules are based on several criteria. The trace width and separation rules are driven mainly by the pitch of the parts you are using on the board. Of course, these rules are also determined by your fab house's capabilities. For example, Seeed has 6 mil trace and space (0.154 mm) as their standard, you can pay more for 5/5 and 4/4. (Other houses do 3/3 and smaller, for a lot more money!)

Another consideration is voltage drop and power handling in the traces. 6/6 is fine for digital stuff from a microcontroller, but not good for driving motors or TECs. Kicad's PCB calculator can tell you the necessary trace width for given current and conductor length.

And remember, you don't need to have all traces conform to one design rule. Your digital traces can be 6/6, analog (op-amp, etc) traces can be 10/6 and power can be as wide as necessary.
 


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