Quick question. I'm trying solder some wires onto the 5 pads (top right of board) in the image. What's the best way to achieve this? I cant get the solder to stick to the board and I have no flux. I have to be careful because there's components on the other side.
I tried to use pin headers on a breadboard, and rest them on, but their not the standard sized pins.
Here's an image:
These look like gold-plated pads, but it's hard to tell due to the poor quality of the picture.
Gold solders very easily, as does any other metal that will be the surface of a pad on a PC board with about that color. Having no flux is no exuse. Get some. Actually any reasonable solder for electronic purposes will have flux core, so you don't really need anything more for this problem. Still, it's not a bad idea to have some flux around for general use.
By using solder with flux (however you achieve that), it should be easy to solder small wires to the pads. I'd probably use small 30 gauge "wire wrap" wire.
With the updated picture, I think it's even more likely those are gold-plated pads. Again, gold is very easy to solder to.
Make sure to strip the insulation from the wire only a short way, not more than the diameter of a pad, prefereably a bit less. Be extra careful that the uninsulated part of the wire doesn't extend past the edge of the pad it is soldered to. That prevents it from shorting to other wires or that strip above the top of the pads. This is all quite doable.
Those gold plated pads are very well suited for the solder to stick on. They just can't get to it.
From the looks of it, I'd guess the manufacturers have used a protective coating (if I'm not mistaken, its called conformal coating). They do this to protect the pads and soldering joints from oxidation or short circuit or any other reason you could think off. The downside to this that you can't do rework easily.
There is a solution (chemical) to remove this this layer, but since you mentioned that you don't have flux with you, I think its safe to assume that you don't have this either. Your best bet is to take a knife and scrape of the upper layer on the pads alone. Be very careful as you may easily damage the pads. You just have to make enough room for the solder to stick.
Another way would be to take a lot of solder on the iron and place it on the board for some time (exactly enough time) so that the heat from the iron melts away the coating. The second method needs a lot of soldering skills (if you have not done some reasonable SMT level soldering don't do this) as you can damage the board or the surrounding components due to overheating just as easily.
