There's a lot of good advice in these posts, but there are are a couple of things I think need saying again anyway:
- If you can't see what you are doing, you can't solder. It's just impossible. I know, I've tried from time to time. Never works.
- You need a temperature controlled soldering iron to make good a consistently reliable joints. Too hot won't work, and too cold won't work either.
Having repeated that, I'll make some specific comments on what you wrote:
MichaelMeissner:
Ok, I've just ruined another board at my attempts at through hole soldering. I was trying to solder the Adafruit i2c backpack for the 8x8 led matrix, and it doesn't work when I attach it to the Uno. A few rows of lights turn on, but they don't seem to be controlled by the program. I assume I made accidental solder bridges or melted circuitry in the PCB.
Assume? If you can see properly what you have done, you don't have to assume. If there is a solder bridge, you will see it. See point 1.
MichaelMeissner:
Part of it is at 57, I'm having to switch between reading glasses and distance glasses (in addition to using the magnifying glass on the third hand jig).
Forget the magnifying glass on the third hand jig. You need stereoscopic magnified vision, for depth perception. If your strong reading glasses don't do the job, you need a visor or loupe or similar, just as BareMetal describes. Point 1 again.
MichaelMeissner:
Part of it is eye/hand coordination.
If you can see, your hands will steady. Ask any surgeon. Refer point 1.
MichaelMeissner:
Part of it is either the iron is not hot enough or it is too hot, and I melt some of the substrate on the protoboard/pcb.
Point 2.
MichaelMeissner:
Part of it is I don't have a dedicated soldering area, and I need to move stuff to do soldering, so I put off doing it. Part of it is I just don't have the patience to do it enough to get better at it.
Once you have the precursors to success in place, you will start succeeding. Absolutely 100% confident of that promise. And you will start enjoying it. You don't need patience when you are enjoying yourself. You only need patience to endure frustration.
MichaelMeissner:
I've tried several times to pick up the skill, but for whatever reason, I seem to have a block on getting the skill.
I believe your "block" is primarily conceptual. See below.
MichaelMeissner:
What other options are there for attaching header pins or using a protoboard? I'd like to keep the price down to about $50 (US).
Very few options, realistically. But for $50 I believe you you can get a pretty decent controlled temp iron. Point 2.
MichaelMeissner:
As I use hot-glue guns for quick crafting, I'm struck that something like a hot-glue gun for soldering would be nice. Ideally, it would have a heating element in the gun that melts the solder, and a tip that dispenses a fixed amount of liquid solder (with possibly an option to dispense a stream of solder to make solder bridges). Ideally you would have several tips that were different sizes with a center portion where the solder doesn't go. You would clip the wire to a small amount, put the gun over the wire, dispense the solder.
Actually, this is the part I really wanted to comment on.
This idea of a "solder as glue" is intuitively appealing, but anyone who has learnt anything about soldering will know why this just can't work. And the reasons for this are important and fundamental to understand.
Solder sticks to hot metal, not cold metal. This means you have to heat the joint before you apply the molten solder. This is counter-intuitive, but until you can get this trick of "heat the work, not the solder" straight, you will be soldering badly.
Solder also will not stick to oxidised metal. Problem is, an oxide layer will start forming within seconds of cleaning to bare metal. What to do? The answer is flux, which deoxidises the metal at the same time you are creating a joint.
But here's the rub: flux burns quickly at the soldering temperature of the iron (what do you think that smoke is?). After a few seconds, the blob of solder on the end of your iron isn't going to stick to anything, unless you apply more flux.
So solder is not like hot glue. You need heat and flux ->on the joint<- for the solder to stick. Unlike glue, a blob of molten solder presented to a cold joint sans flux will not work.
So the recipe is a) apply iron to joint for a few seconds (like, between 2 and 5 seconds -- not long) to get things hot. b) then touch the end of your fine multi-core solder to the joint near the tip of the iron sitting on the joint -- ideally the solder should melt and flow to form a nicely fluxed joint almost immediately. c) if the solder doesn't melt immediately, touch the tip briefly with the end of the solder to get things started.
See how little solder you get away with to get a fully covered joint. Less is more. It's easier to add a bit more solder to a joint than to remove too much. Gradually acquire the skill of making surface tension and capillary action work for you.
MichaelMeissner:
Or perhaps a little pot/heater to melt the solder (much like doing lead molds), and then I would use a small paint brush to attach it to the part being soldered.
And solder is not at all like paint either (as I hope by now you might appreciate.)
People who can solder say soldering is easy, but actually it's not easy. Sure, it's easy once you know how to think about things in the right way, but in the beginning it's all quite counter-intuitive. Starting out many years ago, I made bad joints with too much solder for far too long because I was learning by trial and error, didn't think I needed better tools, and I don't think I really believed what a lot of the old experienced guys writing in magazines would say. "Heat the work, not the solder? That doesn't sound right. Humbug." But when you shake off the inevitable beginner's misconceptions, then suddenly it really does become easy. Do it for a while, and you will have trouble remembering what it was that made it hard when starting. 