Just a quick question. I am trying to make an LCD Shield from my Arduino, and am having problems trying to got the solder to stick to the freetronics protoshield PCB. I have cleaned it as best I can. I am using a decent Proxxon soldering bolt with solder that has worked good for me in the past any tips on how I can get it to stick. It wont bond to the PCB only the wires
Any tips will be greatly appreciated
Flux! (One word answer)
Cleaning the board with, say, alcohol or Windex won't be enough-you're not really worried about finger greases here. What you're worried about is oxidation. Solder bonds to metal, but not metal oxides. Gold doesn't oxidize readily, but other compounds found on circuit boards, like copper and nickel, do so readily. I assume that your solder has a flux component, but stubborn joints often need a little more flux than what is embedded in your solder (usually <5%, probably closer to 2%). A flux pen should be a part of every soldering tool set.
The ProtoShield product uses a gold-based plating system, and claims features like "The PCB surface is gold-plated for maximum durability" and "Gold plated PCB: solders easily and very resistant to corrosion." However, that's not the whole story. Gold is great because it doesn't oxidize readily, but it has the problem that it dissolves in solder, and then reacts to form compounds mainly AuSn4, which weaken the solder joint.
Joint weakness is a problem primarily for processes which put the gold on in thick layers - "Immersion gold" - because there's more gold to dissolve and form those intermetallics which weaken the joint. This would be a concern if you were using surface mount connectors, or something which did not go through the board, but the sheer bulk of your solder joint should make this less problematic. If you're reworking the joint, make sure you have it quite clean, as the residue is damaging to your joint.
The dissolving property is a problem for plating processes which put the gold in a very, very thin layer - "ENIG", or electroless nickel immersion gold - which means that all of the gold dissolves in less than one second, and you're really soldering to the thicker nickel plating below, and using the gold to protect the nickel, like galvanized steel. This is gaining popularity in big production systems, which rarely need to do rework, and the reduced need for flux from plating with gold makes the process easier. The gold will be gone if you try to do rework, so you'll need to use flux with your solder on the nickel surface (which isn't that big a deal). I'm guessing that this is your problem.