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I have STM32's NUCLEO-F302R8 board. The manual is given here. I couldn't find any PCB design file for this board so that I can open it in KiCad, Eagle,etc..

From the manual I couldn't figure out the resistor sizes on the bottom layer for the solder bridges SB51, SB56, SB46, SB52:

enter image description here

How can I infer those resistor sizes?

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    \$\begingroup\$ SB = solder bridge. It’s not a resistor. Size is “appropriate” for making a solder bridge. Do you have any pre-defined in your library? \$\endgroup\$
    – winny
    Jun 19 at 16:50
  • \$\begingroup\$ I mean the resistor size for that solder bridge. \$\endgroup\$
    – GNZ
    Jun 19 at 16:53
  • \$\begingroup\$ @winny Do you have the PCB file for this board? I couldnt find anywhere. \$\endgroup\$
    – GNZ
    Jun 19 at 16:54
  • \$\begingroup\$ 0402? Normal resistor footprints comes with solderstop mask to prevent the very thing you are trying to achieve. \$\endgroup\$
    – winny
    Jun 19 at 16:54
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    \$\begingroup\$ Their cad resources page has a link to the gerbers: st.com/resource/en/board_manufacturing_specification/…. I didn't follow it, but that should give you footprints. \$\endgroup\$
    – TimWescott
    Jun 19 at 17:05

2 Answers 2

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The CAD files that @TimWescott referenced contain the PCB layout (in the schematic zip, not necessarily where you would expect it). As typical for ST, they are in Altium.

The footprints look like this:

enter image description here

Outer copper dimensions are 100 mils x 40 mils. So maybe an 0805 would be appropriate.

enter image description here

Of course if you're doing a few by hand all you need is a soldering iron and some solder. Lead-free will work even better than nice 63/37 solder.


(below does not relate to your eval board)

I note that a Nucleo board I happen to have in front of me at the moment (G071RB) has jumper dimensions that are hard metric and a bit smaller (2.4mm x 1mm) and they bridge them with 0603 zero-ohm resistors. Unusually, they mask the pad off partially with solder mask (i.e. the pad is partially solder-mask defined). Probably some compromise to allow the boards to be reliably machine-assembled with zero-ohm 0603 parts- so the asymmetric pads don't pull the resistor to one side when the solder is molten and look bad or maybe even tombstone.

enter image description here

enter image description here

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  • \$\begingroup\$ Is there any reason that first footprint you show doesn't have the soldermask opened between the pads? You would think you'd want that with a solder bridge. \$\endgroup\$
    – Hearth
    Jun 19 at 19:34
  • \$\begingroup\$ @Hearth They put paste on all the pads so probably appropriate. On the second one they only put paste on the pads that were populated with 0 ohm resistors. \$\endgroup\$ Jun 19 at 22:22
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A solder bridge is either a blob of solder across two specially shaped pads, or a 0-ohm resistor, also called a jumper. That's it!

The name of the thing itself tells you what to use to short it: solder :)

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  • \$\begingroup\$ I actually tried this and soldering with a a blob of solder was much easier to forma bridge than using such tiny zero ohm resistors. I first tried the zero ohm resistor but failed it was super difficult to hold it tight. Finally I gave up and did solder blob between the pads. \$\endgroup\$
    – GNZ
    Jun 20 at 16:51

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