It's not a problem, especially with those little 0-ohm resistors - I've stuck one on the left hand side.
Would it be sensible to stick one on the right, jumping over the output trace too? Kinda forms a ground loop, but I don't know if that's something to worry about at the PCB level. (This is a simple buck converter, cribbed from a datasheet, operating somewhere around 10-100kHz, if that's relevant).
I guess what I'm asking is whether it's generally a Good Idea to join ground islands up everywhere you can fit another jumper, or whether it's unnecessary.
(I'm guessing there's no huge difference between jumping a trace over the ground vs. jumping the ground over a trace. Or is there?)
How are the +12/Gnd and +5/Gnd connections made?
I would put the pads for both a little inside the border of the board so the Gnd can be continuous around the perimeter of the board.
I.e. next to C3 on one side and next to C2 on the other.
You're right, this isn't the best example as the layout could be fixed easily; I'm really just trying to understand the principles. Say you've a complex design with many Ground islands that need to be connected together, is it best to bung jumpers everywhere, or should you keep a single path between islands (ie avoid making lots of ground loops).
On single sided, can be difficult to keep them all connected.
Use a double sided board, and let the back side be the common point. Drill thru, drop in a pin and solder to both sides. Probably solder the back first.
CrossRoads:
On single sided, can be difficult to keep them all connected.
Use a double sided board, and let the back side be the common point. Drill thru, drop in a pin and solder to both sides. Probably solder the back first.
Yes, one way to go, double sided board isn't prohibitively expensive and you
get a continuous groundplane. If you have through-hole components though
you'll have to mill out some islands on the groundplane side...
Alternatively with single sided / SMT you want to make ground links low-inductance
if possible, so use wide 0R resistors (1210) - these are also long enough to
bridge traces so everything can be single sided with luck.
The resistors aren't a bad idea if carefully placed. Also the 2512 sized ones are even bigger than 1210. However, the idea of just buying a double sided board and only etching the top makes a lot of sense since you are doing only SMD. Through hole, its actually quite easy to 'mill' out the area using a larger drill bit and just spinning it against the board in a drill, without trying to push through the board. However, just keep in mind it will be mildly difficult to solder to the ground plane as it is a massive heatsink (relative to what you are soldering).
My experience with soldering to a large plane is that it gets real messy, I'm so happy I found the "heat-pad' option in eagle: it makes a small peninsula around your soldering point, with connectors all around to the plane. You can use that on the backside of the PCB, but you will have to etch it then. In practice I tend to use large (3612 metric) 0 ohm resistors.
Thanks for the creative answers! A proper ground plane would be best, but it's not possible (or practical) for some of my circuits.
I'll stick jumpers everywhere I can.
MarkT:
Alternatively with single sided / SMT you want to make ground links low-inductance
if possible, so use wide 0R resistors (1210) - these are also long enough to
bridge traces so everything can be single sided with luck.
Yep - I love the 1210 size ones, cos you can jump over three tracks if you're careful:
(excuse the dodgy soldering, this is an old board and I've got a lot better since then)
Didn't think about the inductance thing, though; I'll stick with the 1210s rather than 0805s in that case.
(excuse the dodgy soldering, this is an old board and I've got a lot better since then)
Nicely done. I'm saving that image to show people at http://generatorvermont.com where we just got a nice Roland CNC router that I bet can make nice SS boards,
