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I'm new to prototyping with perf board (Proto board) and was wondering if I could solder over the solder mask to another hole instead of using wires to provide something for the solder to stick to.

(Here is a photo of my board)

enter image description here

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    \$\begingroup\$ I personally prefer using wires since it produces less residue, less toxic gas and consumes less solder. With some patience, you can cut the wires and shape them using tweezers in beautiful shapes. \$\endgroup\$ Commented Feb 23, 2023 at 20:58

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This is called "bridging" the solder pads, and is frequently done unintentionally by clumsy solderers. It's possible to do it intentionally with enough solder, though that will depend on the spacing of the pads, their shape, and the quality of the underlying solder resist.

To make this work best, add a generous amount of solder to both pads, make sure both blobs are melted, and then drag them together with your iron tip. Once the bridge starts to form, and provided the pads aren't too far apart, surface tension will pull the two blobs together into one.

If the pads are too far apart, though, a small (0.1"-0.2") piece of stripped wire can help "guide" the solder between the two pads. The wire does not need to push through the holes; it can just sit on top of the pads. You can use longer pieces of wire to make a bus across a whole row of pads.

In circuits that are designed to be intentionally bridged with solder blobs, you will often see pads that look like this: Why would I use triangular solder jumper pads?

Once you get the solder bridge to stick, it's generally as good as any other perfboard connection. (Which is to say: not great, but functional for low-speed or DC signals.)

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Setting the soldering iron to lower temperature makes it easier to bridge the connections.

You might unintentionally open a bridge at a later stage of building the board, so I'd stick with the wire.

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All of the "can I do this" answers depend on your quality standards, which can range all the way between hobbyist project for fun up to IPC class 3 or anywhere in between. Obviously for a hobbyist or quick & dirty prototype purposes, pretty much anything goes - I personally know and use numerous such dirty tricks, much to the dismay of the IPC certifying teacher. It isn't meaningful to answer the question assuming anything else but high quality standards, however.

Assuming a professional context "by the book" then:

  • No, you should not bridge across the solder mask between two plated holes, because that is impossible to do with a correctly wetted solder joint. The distance is deliberately picked so that two holes won't short by accident.
  • Bridging on a through-hole board should always be carried out on the component side, never the solder side. This is to avoid "hidden surprises" but also to prevent shorts.
  • Ideally the bridge should be formed by something like component (header strip etc) or a wire with insulation.
  • All bridges/connections on a PCB must be tightly secured close to the PCB itself. Big loops are unacceptable. Non-isolated bridges hanging in the air like in the pic are unacceptable. In the case you use some non-isolated wires for such a bridge, it needs to be mechanically secured so that it can't get pressed against anything by accident.
  • Through hole pins should be cut on the solder side at (iirc) 1.5mm from the PCB before soldering.
  • Cold joints as the lower two on 'M' and 'O' on the pic are unaccepable. Numerous joints look questionable and wouldn't pass inspection.
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