And finally, to make this comment more useful, so I don't hemorrhage my 33 points of karma: If you've ever wanted to gracefully rework SOICs, QFPs, etc., invest in a good hot air system with appropriately-shaped spreading tips. Amazon has a basic kit for $139: http://www.amazon.com/X-TRONIC-Digital-Rework-Soldering-Stat...
Do not use ChipQuik. It's expensive, unnecessary, and messy.
 Metcal enthusiasts, before you have a heart attack, recall that Radio Shack sells disposable lightsabers for $7.99.
I believe it should be a sin punishable by death to abuse a soldering iron like that.
1) The solder should always be convex, not concave. It's not that way in the illustrations. A concave ball, as sometimes shown, may be a good connection to the pad, but a cold joint to the wire. It'll work, for a bit, but may eventually fail.
2) Always, always, always keep the tip tinned (covered with a thin layer of solder). The solder acts as a thermal conductor between the iron and the joint, which lets the joint heat up much more quickly. It also prevents the iron from oxidizing. If you don't do this, the iron will oxidize, and you will no longer be able to tin it.
3) Feed the solder into the joint, not into the iron. That tells you the joint is hot enough.
4) Temperature controlled iron makes a huge difference. Weller WES51 is the minimum you should use ($90 or so). More expensive irons in the Weller line don't make a big difference. Metcals are nicer, but wicked expensive.
Citizen Engineer is a comic book / zine / electronics kit. Unfortunately, they haven't released a volume 2 yet.
Once you get used to doing it right, desoldering braid is awesome. I never did get the hang of those squeeze bulbs, though. The braid was always so much easier to use.
The trick with desoldering is that sometimes you need to add more solder before you can remove it. If a joint won't desolder, the easiest solution is to add a bit more solder until it balls up, then suck it all away with a spring-loaded solder pump.
I find desoldering braid a bit tricker, but the secret there is to prime the braid with a bit of solder to improve heat transfer before holding it to the joint.
I've actually done more desoldering than soldering and I would have gone crazy if I had tried to do it that way. I find braid to be the easiest method by far, but that's just personal preference. I'm sure there are people other than me who can get the suction devices to work well and who don't have to buy braid all the time.
One thing that's rarely mentioned in soldering tutorials is temperature. With good temperature-controlled soldering stations like the Weller WES51 available for <$100, I'd be hard-pressed to recommend skimping on a cheap pencil iron. Trouble is, I've seen very little discussion about what temperatures to use for particular types of solder.
I put this question to one of the EE lab instructors at my university. Their choice is 700-750F for standard 60/40 solder. I use 750F at home with good results.
You need higher temperatures for lead-free solders, which is one of the reasons I avoid them.
One of the amazing side effects of technical comic guides are that small children, who are not really the target audience, end up picking these up and learning things like Physics, Database Design, and now Soldering.
My opinion differs on soldering irons. I find that cheap electric soldering pens tend to give me poor results. For someone starting out I think this could be discouraging. Radio shack has a cheap butane pen that works much better for me. It does cost slightly more, but I find it is usable on a wider range of projects and can even heat shrink tube in a pinch.
It doesn't cost much to get a great iron.
For electronics, use a soldering station, which is basically an iron that's stabilized and allows you to control the temperature.
Or use a soldering gun, but this is a bit of an acquired skill, and tends to fry sensitive CMOS devices (or anything that doesn't like EM fields and pulses). I still prefer the gun for regular components, but I'm probably old school.
Another tip: when in doubt, put a little rosin on the pad and lead before soldering them, even though the alloy is supposed to contain rosin already. Again, this reduces the risk of a poor contact.
Never use cheap unstabilized soldering irons - those are only for rough jobs like soldering the lid on a tin can, and then just use the biggest iron you can find. For electronics, only use stabilized (regulated) irons (soldering stations), that allow you to finely tweak the temperature. Working at the right temperature is crucial; too hot and you burn components and oxidize pads before they get soldered; too low and again you may burn components because you're fiddling with the iron too long; or you make weak unreliable contacts. You'll figure it out with experience.
I actually prefer to use a soldering gun instead of an iron for anything except very sensitive multi-pin components that don't like EM pulses. Again, it's a bit of kung-fu to know when to push the trigger and when to release it; essentially, your brain becomes the thermal stabilizer. :) You need to "wax on, wax off" many hours before you obtain the skills, but then it's awesome. The gun allows you to do neat tricks like transport large drops of solid rosin, because you heat it up or cool it down instantly, as needed; a station, OTOH, is always at the same temperature.
Heating up both lead and pad at the same time is crucial. It bears repeating - crucial. Push the iron or gun against both parts. Don't push too hard, but make sure the thermal contact is good and firm.
Whether you wait 1 second before touching the heated pad+lead with the alloy, or you don't wait, depends on the technique. Whether you wait 1 more second before you retract the iron, or you don't wait, again depends on the technique. But once the liquid alloy has spread out, pull the iron at once, don't tarry. Then blow air over the hot area.
Nail clippers work just fine for cutting leads.
Sometimes you don't want to solder components too close to the PCB. This is true for those resistors, transistors, etc. that dissipate a lot of heat while working. Give them some breathing room. In general, don't push 3-pin components (such as transistors) too close to the PCB; when they begin to resist, you need to stop pushing. But soldering them might be tricky if they're not sitting stable in that position.
All that stuff about toxic metals and rosin fumes - I should probably be a brain dead zombie by now, I never washed my hands afterwards. Rosin smells kind of nice actually, similar to incense, but breathing the smoke directly is not pleasant; I doubt the smoke is more toxic than any other kind of smoke.
Finally: 2 hands are sometimes not enough. It helps if you're an octopus.
In other words, make sure you have some way of moving the fumes out of your workspace, preferably having a wide open area, and or a fume extractor (Weller makes a great one).
With proper technique, rosin is highly effective as flux.
Once I did a trial with aspirin instead, out of curiosity, but that stuff is devil's brainchild. It's very effective, it allows you to solder stuff on oxidized surfaces without problems, but the fumes will burn your nose, throat and windpipe - and maybe lungs too if you breathe deeply, which is pretty hard because you start coughing immediately. It's acid smoke, very corrosive. I tried it, then refused to use it again.
"Then blow air over the hot area."
I'm no expert, but I've always heard this is a bad idea. (A "cold solder joint")
If failure is absolutely no option, then hold the lead on the other side of the PCB (between the soldered area and the component) really tight with some mini-pliers, to prevent too much heat from reaching the component (some heat is leeched by the mini-pliers). But this is very tricky. Sometimes I also keep a finger on the component, to remove some more heat, but I got burned more than once, since I was daydreaming instead of paying attention. As a teenager, my finger tips were always burned from the rather brash soldering technique I was using. I'm a little more cautious now.
Blowing before you remove the iron is a bad idea - if not for making bad contacts (once the liquid has managed to wet the lead and the pad all around, there's no risk of cold joint anymore), then at least because there's a risk you may blow the liquid alloy away. :)
Cold solder joints can often be recognized if you know how to "read" the shape of the solidified alloy. It's not a foolproof technique, but it does reveal the more egregious mistakes. If the alloy makes a round cone-like shape, uniform, symmetric, without interruptions, if the alloy seems to "merge" into the pad and the lead (or seems to "wet" both surfaces), as opposed to appearing to repeal the metal ("non-wetting" material) then chances are the contact is good.
I've been soldering for years, and just once I thought "you know, I'll just solder right here on the carpet. I'll be careful not to knock the iron over," instead of moving to my work desk. I melted a hole in the carpet.
1) Always tin the tip before soldering and tin it again before you put the soldering iron in the stand. This prevents oxidation of the tip.
2) Put some flux on the joint before soldering or desoldering. Always use a flux made for electronics, not the kind used for plumbing.
3) If the tip of the iron gets too much oxidation on it, you can generally restore the tip (do this when the tip is cold) by putting a bit of ammonia-based brass or silver polish on it and scrubbing it a bit with some steel wool and then wiping with a clean rag.
4) Whenever working with wire leads, tin the wires first before setting up the joint.
I don't know that it'll be all that useful, but I'll share some of what I've learned.
The key goals in an engineering environment are:
1.) You don't damage boards. No lifted pads, no torn barrels, etc. Ever. Unless you mean to (and sometimes you do, to make salvaging a pristine part easier.)
2.) You don't damage components while removing them unless you mean to (and you often will, to protect the board.)
3.) Your soldering is functional. When you are doing quick iterations, and noting the effects of whatever rework you've just performed, you need certainty that your circuit is actually what you intended.
With a Metcal (or equivalent) and one fine tip, one broad tip -- you can remove or install pretty much any surface mount leaded component -- from a 0402 resistor to a large fine pitch TQFP. This sort of thing is common. You can also remove and or install pretty much any through hole component, up to large connectors. I'm going to talk mainly about removal, because it's not talked about as much (as it should be) and it's the more difficult side of things.
1.) small 2 lead discretes -- easiest with tweez pencil, grab it, solder flows on both ends, pick up, easy. generally you'll want to keep the part handy as you may go back to it, often just solder the resistor or cap to some other pad nearby, tombstoned. If you have only one iron, and say you're removing a 0402 -- easiest is to add solder to both ends of it and dance the iron back and forth rapidly to the leads. If the thermal reliefs are decent (as they should be for a 0402) it will tombstone itself and come right up.
2.) soic -- easiest with two irons (perform the below at the same time on both sides), but if you've only one, no problem. Take a SOIC16, 8 pins a side. Flow much solder down one side, bridging all pins. With any tip you'll be able to slide back and forth, causing all 8 leads to become molten. You want to use enough solder to bridge REALLY well. Insert tip of tweezer or dental pick under body near molten side and lift slightly. DO THIS VERY GENTLY. If all of pins aren't actually molten, and you pry on it, you will lift pads. It takes very, very little pressure. Once one side has lifted slightly, go to the other side and do the same thing. Now your SOIC is sitting above the board on both sides, sitting on solder piling. Take some solder braid and wick the solder from underneath the pins. Your SOIC will come loose, and you can clean it and the pads up with wick. SOIC is good for reuse, no lifted pads. If you did this with one iron and had to slightly lever the part, reform the leads slightly using tweezers.
3.) TQFP fine pitch -- It's always best to have all the right tools, my guide is how to do it when you don't have the right tools -- but need to do it anyway, and still pull it off. These are tricky.
With 4 irons (2 people) I've performed the solder bridge method, works well. Just flow all pins and remove part. With 1 guy, one iron, it can be done but you'll have to reform some leads when you're done. What you want to do is use fine tweezers or dental pick, and you're going to heat up one pin at a time and use the tip of the tweezer or pick to pluck the pin forward, lifting it up. You want to really heat up the pad, make sure solder is fully molten. Adding some flux is a good idea. Fine pitch pads with tiny traces are notoriously difficult to rework without lifting pads -- because people don't heat enough before yanking. You will probably lose some no connect pads using this method, tough not too.
You want to use this method on as few of the pins as possible, as its the most dangerous method. I cant stress enough, HEAT before applying any upward pressure. You want to work yourself into position to use the solder bridge method.
Do the above on two opposing sides (sides A and C). Just work your way down and do all the pins on both sides. Make sure all pins you think are free really are -- go through with wick and suck up the solder under the leads you've lifted. With two sides lifted you're back to a SOIC essentially..use the solder bridge method to lift sides B and D.
I've done many dozens of large TQFPs this way, with one iron, with no lifted pads. If can be done, just be very careful and take your time.
4.) Large through hole things with many pins (connectors, power bricks, etc) --
discretion is the better part of valor. If you are dealing with something with many through hole pads that touch heavy ground or power planes on multiple pins -- your best bet is to destroy the part. Trying to solder suck or wick out power and ground pins with a single iron is sometimes just impossible to do -- you will be at it for a long time, until the pads finally falls apart and you lose the annular ring, and your board is damaged.
If you only have one or two pins connected to a plane -- and all the rest are signals pins -- then clear the signal pins using wick/sucker, and then try to heat the reaminder of your plane pins at once. If you can get them all to flow, you can just yank the part out -- and THEN clear those plane connected pins.
If your part doesn't lend itself to this -- get out the dremel tool or the cutters and go to work on the part, systematically chopping or cutting it down until you are left with nothing but the pins in the holes....then simply heat the pad and pull out the pins with tweezers. THEN clear the hole. It is almost always the right choice, I've seen more boards destroyed by people trying to remove large through hole connectors and power bricks, when preserving the part was not a necessity. Know the goal -- if the part can go, then chop it out in little chunks. Not only the right thing, but kind of fun, too.
OK, that's all I can type for now -- I'm sure everyone has their pet methods and whatnot, and there are always caveats. I think its good to have the tool bag to perform "down and dirty". Honestly most places I've been, that's all there is or is time for.
I was trying to desolder a damaged mini usb port on my wifes mp3 player. heat, wiggle, heat, wiggle, pull... broke the traces. I should have cut the offending part down first to avoid damaging the board.