Author Topic: Couple questions on standard design practice.  (Read 1360 times)

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Offline Dan MoosTopic starter

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Couple questions on standard design practice.
« on: November 21, 2018, 05:37:07 pm »
I'm doing a project that is mostly standard pdip style components. My first question is, what trace size/spacing is standard for such a thing? It will be 4 layers, with the internal layers being ground and Vcc. No real size limitation on board dimensions, but obviously the more compact the better.

Next, drill sizes. Are they part of the footprint in me EDA (KICAD)? Is there a resource out there with suggested drill sizes for various common parts? Honestly, the drill sizes are the thing I'm most paranoid about messing up. My project is a VGA controller done with all 7400 logic, so my board size is almost certainly too big for the super cheap deal most places offer. That and it being 4 layers.

I'm fine with a couple failed attempts, but wanna play to win!
 

Offline Bassman59

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Re: Couple questions on standard design practice.
« Reply #1 on: November 21, 2018, 06:07:13 pm »
I'm doing a project that is mostly standard pdip style components. My first question is, what trace size/spacing is standard for such a thing? It will be 4 layers, with the internal layers being ground and Vcc. No real size limitation on board dimensions, but obviously the more compact the better.

Minimum track width and space has always been based on what your PCB fab house can do and at what cost. If you're using DIP then it's likely you aren't trying to squeeze a bunch of traces in tiny areas. 15 mil traces are probably fine. Whatever works, really.

Quote
Next, drill sizes. Are they part of the footprint in me EDA (KICAD)? Is there a resource out there with suggested drill sizes for various common parts? Honestly, the drill sizes are the thing I'm most paranoid about messing up. My project is a VGA controller done with all 7400 logic, so my board size is almost certainly too big for the super cheap deal most places offer. That and it being 4 layers.

The drill sizes are baked into the footprints. If you're using the standard Kicad 5.0 libraries, the sizes for the pin holes are correct. I honestly haven't seen a fab house publish a list of their standard drill sizes in ages.
 

Offline Siwastaja

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Re: Couple questions on standard design practice.
« Reply #2 on: November 22, 2018, 09:18:03 am »
Drill sizes are always in your IC datasheet, there is the recommended footprint. If not, it's a separate document from the same manufacturer.

Always double-check with the actual datasheet for the actual part you are using; don't assume a similar part has the same measurements (even though a DIP IC should be a fairly reliable standard). Never trust a library footprint coming with the EDA tool, or downloaded from the 'net. They are wrong more often than they are correct, which may sound insane, but that's the way it is.
« Last Edit: November 22, 2018, 09:20:01 am by Siwastaja »
 


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