I goofed and didn't notice this until the board was already fab'd and assembled. The board is an RF amplifier; the portion I have pictured is a part of the DC control pat (so no RF is nearby but we're talking 100MHz-1GHz so it's surely floating everywhere). See the possibly disastrous screenshot marked by 'missing a via here'. (The fab removed by hand the huge trace to nowhere, before anyone asks). I really need to be more careful with altium's polygon pours…
I'm really kicking myself right now about this stupid error, it's a 20 board run and money is really tight; I'm in academia, so these boards are not getting remade. The problem is C18 is a 100nF bypass cap for a high speed op-amp. It seems to me that without a via to the ground plane, theres only that ultra tiny slice of the pour connecting it to a via 'very far' away. I might be wrong, but from everything I've read, the cap might as well not even be there because the inductance will be so large. I don't have the boards back yet, so the fab might even have eliminated that small trace entirely! It's only a few mils thick.
Maybe I'm being overly worried, as I don't yet know if this will cause issues. But is there anything I can do 'by hand' to improve the decoupling? Would soldering a small wire to ground be effective? I guess my main concern is oscillation with RF signal floating around everywhere; the op amp I'm decoupling is the LME49990, and I've seen this thing oscillate when bypass caps arent placed right.
Best Answer
Drill a small hole that will allow you to simply run a free thin piece of wire from the ground plane on the opposite side of the board to the capacitor.
Stripped wire-wrap wire works well. It's 30 AWG, so the hole that you drill can be very small.
Use a Dremel tool in a drill press if you have such available - I routinely drill #78 holes reliably without breaking the bits.
Your can modify all of your boards in fairly short order.