I would increase the diameter of the vias to 0.9mm or 1.0mm (better). I assume you are having these wave soldered? If so, request that the vias be left open (ie not covered over with solder mask as is becoming more common now). The vias will *mainly* fill with solder during the wave soldering process which will carry a lot more current for you.
For your tracks - why not open up the solder mask on the bottom side so the track receives a coating of added solder during the wave soldering process. This also aids in reducing the operating temperature of the track as it can dissipate the heat to the air much faster. You can also open up the top side solder mask & paste mask & "grid" a pattern of "squares" across the surface to increase the current capability of the top tracks.
No wave soldering. Planning on reflow for the surface-mount components, then hand-soldering for the few through-hole components. This is not something that is going to be mass-produced.
I suppose if I really wanted the vias to be solder-filled, I could maybe do it with reflow by leaving them unmasked and adding a dot for each on the paste layer. Would that work? No idea how much paste each via would need relative to it's diameter, though.
This is actually my second revision of the board, and on the first I did actually have it with the tracks un-masked and coated with solder, but that was only because I was being tight-fisted and didn't want to pay for 2 oz copper for the prototype boards.
I would prefer not to solder coat, as there is a component that has to sit partially over the tracks, and it sits wonky because of the uneven surface.
The current will take the shortest path until the track (or via) heats & the resistance goes up. The current will then select the next lowest resistance path.
Ah, I see. Makes sense.
So, what's the chip footprint thingy? Just something off to the side? Not carrying much current?
What's the current coming from? The oblong hole, a THT pin? Why not connect the trace directly up to it, no vias necessary?
It's a 1206 resistor. That and other components just out of shot are a divider/protection/filtering for an input to the micro for detection of when power is applied to that track.
The current is coming from the oblong THT pin on the left. Yes, you may be scratching your head wondering why I don't connect the trace up directly.
It's a question of ease of serviceability and access. That pin (as well as others) is a fixed part of the assembly to which the board is attached. The board is installed by dropping it over the pins and soldering it down. Once installed, there is no physical access to the bottom side of the board.
Through experience with my first prototype, where these through-holes are plated, I have found that it makes the board a real bitch to de-solder. The pins are part of what are effectively copper bus bars, and thus a large heatsink. Every time de-soldering I have failed to avoid ripping out at least part of the plating of most holes.
By having these pins soldered only on a single side - the accessible top side - it becomes a piece of cake to remove the board.