Hello everyone
How can I solder a wire into this tiny through-hole? There are no visible copper traces connected to it on either side of the PCB. However, the hole appears on both sides of the board, and the two holes are electrically connected. What's the proper way to solder a wire to it?

 

If there are no traces connected to it, why do you want to attach a wire to it??

 

There are no visible copper traces connected to it

In image *30 there appears to be a narrow trace going south to the big hole.

 

Check continuity, if @Alec_t is right !

 

It looks like he peeled external copper layer and wants to connect to vis because it ties to tracks on inner layers. The via seem to be .006" - .008" at most. This requires steady hand, ver fine wire (awg30..awg42) and then fixing the connection with drop of solder mask

 

If there are no traces connected to it, why do you want to attach a wire to it??

This is the power button board of a laptop. This pad has no visible trace on either the top or bottom layer of the PCB. However, the board is clearly a multilayer PCB, and this pad carries a constant 3.3V. When the power button is pressed, it momentarily connects this pad to ground, which turns the laptop on.

 

In image *30 there appears to be a narrow trace going south to the big hole.

No it doesn't have any trace either the top or bottom layer of the PCB other layers perhaps

 

It looks like he peeled external copper layer and wants to connect to vis because it ties to tracks on inner layers. The via seem to be .006" - .008" at most. This requires steady hand, ver fine wire (awg30..awg42) and then fixing the connection with drop of solder mask

Yes, that's what I've been trying to do. Unfortunately, the via is extremely small, and its annular ring is so narrow that it just won't accept solder. Even with a fine SMD soldering tip and flux, I haven't been able to solder a wire to it.

 

Is there no other place on the board where it may come to the surface and connect there?

 

Yes, that's what I've been trying to do. Unfortunately, the via is extremely small, and its annular ring is so narrow that it just won't accept solder. Even with a fine SMD soldering tip and flux, I haven't been able to solder a wire to it.

that exactly is the problem. stop using fine tip. use big fat tip...

the whole point of soldering is heat transfer. you need to heat both sides to temperature above melting point of the solder.

that via has such tiny surface it is hard to get any heat to it. and when soldering iron has fine tip, its ability to deliver heat is already compromised. fine tip freezes easily. btw. the only reason fine tips exist is to avoid disturbing nearby parts when things are packed densely. but there is nothing near that via, nearest feature is several millimeters away so stop shooting yourself in the foot and get the big tip.

clean the via mechanically using needle to make it shiny, dig into center to remove then use very fine wire. and... do not start by soldering it to via. first solder the wire to wherever the other end need to go, then secure it with a drop of glue or masking tape or whatever.... then gently bring the free end of the wire to the via, apply flux to cover the via and wire end you wish to connect to it. then crank up the temperature of your gun way up, put big blob of solder on wide tip of your solder gun. and then go for it...!

 

That appears to be a via not a pad. If it is, it is in a trace. Clean the copper and solder to the trace being careful not to overheat it.

 

This is the power button board of a laptop. This pad has no visible trace on either the top or bottom layer of the PCB. However, the board is clearly a multilayer PCB, and this pad carries a constant 3.3V. When the power button is pressed, it momentarily connects this pad to ground, which turns the laptop on.

Look at your first photograph, the through hole copper connects to R154 and perhaps more, it's covered in green dye so is not obvious.

 

I usually run small wires through via's when repairing something like that.

If having trouble getting heat to it then add flux to the via, then put a big blob of solder on your iron, you iron tip doesn't need touch the via, the heat will transfer through the blob of solder and the flux will keep the solder flowing smoothly.

 

Looks like it’s a tiny via connected to an inner-layer trace. You can use a very fine wire and solder it carefully to the exposed copper around the via. Just be careful not to damage the small copper ring.