Is there a "standard" resistor/capacitor footprint?

[Aaron_Brice]

Thanks everyone. Think I’ll just copy the footprint from the adafruit eagle schematic, which seems to be 0603 for most resistors and capacitors, and then 0805 for 10uF capacitors. My plan is to have JLCPCB assemble a handful of boards that work perfectly without any rework needed.

[BobZ]

@buzmeg

One of those considerations used to be that the voltage rating on 1206/1210 was vastly better than small footprints at the same price. New technology, however, seems to have rendered the DC Bias differences moot–a capacitor now has the same DC Bias characteristics at the same voltage rating regardless of footprint.

I intentionally ignored DC bias effects when I made my comparison. Generally the larger capacitors had higher voltage rating (such as 250V) so capacitance would drop less at a given voltage such as 20V. You could alternately choose a more stable, lower K dielectric for which I did not compare.

When I look at recommended layouts (when that is critical) in IC app notes they often do not indicate the chip sizes. If I estimate based on scale with the IC I come up with some very small chips.

FWIW I like this chip, but see the sample layout from the DS for the LM5155:

My best guess for CF is that it is an 0201.

@buzmeg

New technology, however, seems to have rendered the DC Bias differences moot–a capacitor now has the same DC Bias characteristics at the same voltage rating regardless of footprint.)

Skeptical. Can you link to one or two examples?

[buzmeg]

You are correct; I was in error.

Bias no longer correlates to Voltage Rating. Footprint, however, still makes a big difference.

1.0uF–uniformly 50% derating @ 3V from 6-16V:

https://www.murata.com/en-us/products/productdetail?partno=G…

https://www.murata.com/en-us/products/productdetail?partno=G…

https://www.murata.com/en-us/products/productdetail?partno=G…

100nf–uniformly 2% derating @ 3V from 6-16V:

https://www.murata.com/en-us/products/productdetail?partno=G…

https://www.murata.com/en-us/products/productdetail?partno=G…

https://www.murata.com/en-us/products/productdetail?partno=G…

[BobZ]

@buzmeg

Bias no longer correlates to Voltage Rating. Footprint, however, still makes a big difference.

Good point! Yes I think the higher voltage ratings IN A GIVEN CASE SIZE mainly have (or just guarantee) better dielectric (quality & uniformity) so that it can withstand more voltage stress without breakdown failure.

[jarfriede]

As a former long time Eagle user, I would highly recommend taking an online KiCAD class (I did one on Udemy) and redraw the schematics from scratch. Eagle has a completely different workflow when it comes to libraries. I have found I can complete a board in much less time than I could with Eagle.

Also, I upgraded to KiCAD 9 but it broke my libraries so I went back to 8. The “Fabrication Toolkit” plugin makes working with JLCPCB a piece of cake.

[Aaron_Brice]

@jarfriede

As a former long time Eagle user, I would highly recommend taking an online KiCAD class (I did one on Udemy) and redraw the schematics from scratch. Eagle has a completely different workflow when it comes to libraries. I have found I can complete a board in much less time than I could with Eagle.

Yes, good advice. I originally did the import from eagle, but there were a couple of small things that didn’t look right (some test points labeled ${TP_SYMBOL} or something like that for example) that made me think there were other details that might not be correct and I wasn’t expert enough to verify them, so better to start from scratch and use the eagle schematic as a reference to adding symbols from the kicad library.