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Step 3The method
If you have a decent iron, the right solder and a cleaning scour you are halfway there now you just need to pay attention to a couple of importnt points and you will get good solder joints.
Modern soldering iron tips tend to have special coatings, this is good because it prevents the oxidising as quickly as they used to. This coating is the reason I say you should never file or sand your tip to clean it, once you start that down that route, you will probably have to keep doing it every so often and the tip will be worn out quite quickly. If you look after the tip, it will last a long time.
Now this oxidisation happens quickly when the tip is hot, you can see it because the tip goes from shiny silver to dark and dull, it actually goes quite grey in colour and can almost become black. Now the problem is this layer of oxidation reduces heat transfer. Some people don't realise just what an effect this has and keep trying to solder with the iron in that state. The problem is, you will struggle to make a single solder joint with a tip like that. The secret is to clean it before every joint. Well sometimes you can do a few joints straight after each other and I would usually at least do both wires of a resistor for instance, but you can't just keep soldering without cleaning the tip.
Now cleaning can just mean wiping the tip on your scouring pad a couple of times, so no big deal. But if the irons been sitting for a few minutes you need to go a bit further. You need to clean and then 'tin' the tip. The 'tinning' prevents the oxidation of the tip and to do it the tip needs to be hot and clean. So you pick up your hot iron, wipe the tip on the scouring pad a few times and then immediately melt solder onto the tip to tin it. Don't be shy with the solder, it's cheap and it will drop of the tip as you do it, but some will stick, kind of 'paint' the tip with solder and then wipe the excess on your scour, then do your solder joints straight away. If you put the iron down for a minute after tinning it, you will probably just need to wipe it on the scouring pad again and then you can solder. But wait too long and you will need to clean and tin it again. This is why it's a good idea to load a board up with say all the resistors and then solder them all in at once instead of putting one in, solder it, put the next one in etc. That way you can do a few joints, wipe clean and do a few more etc. By the way, you should tin a new tip the first time you use it, before the iron gets hot for the first time the tip will be shiny, it heats up and starts going dark, clean it and tin it.
It's not really that difficult and with practice it will become second nature, you will get to know when you need to tin the tip and when you can get away with just wiping it. Be careful though wiping it enough will always clean it, but it shoud be shiny after wiping it, or it will oxidise very quickly. Now that tip refresher I mentioned is great for this, instead of tinning the tip the long way, you just dip it into the solid refresher, it melts and cleans and tins the tip instantly and you just give it a quick wipe on the scourer and keep going. I find the tip refresher lasts longer between tinning than using solder, so its worth the little bit it costs. Plus it lasts for a long time. Check the close up picture of the tip, the top one is oxidised the one below is after tinning, it should look like this whenever you go to solder.
Now the idea with soldering is you want to get both of the things you are joining hot enough and then introduce solder. Don't load up the tip with solder and try to transfer it to the joint. You should touch both pieces you want to join with the tip at the same time and hold it there for a couple of seconds to allow them to heat up. Now the best way to work out what you should be heating is to remember a simple rule.
Solder will always flow towards heat.
So hold your iron on the join for a second or two, then introduce solder into the join, it will melt when it touches the iron, as soon as you see the solder flow into the joint, lift the soldering iron away. Don't jerk it away, just lift it off.
Now to do this well you need to have everything secured in place so you can hold the iron in one hand and the solder in the other. No balancing tricks (until you know what your doing and can get away with it). This requires having everything held in place by its own weight or under tension or with a clamp, or whatever, no chasing parts around the bench with a hot iron.
By the way, check the pictures I put on this step of an example joint, it should look something like this (not great as I was trying to take pictures at the same time) it should have a slight concave to the solder join and be smooth. In the second picture you can kind of see how I'm holding the tip onto the copper pad and also against the resistor lead close to the pad. Notice the size of tip I'm using, it's the standard tip the iron comes with, not exceptionally fine. But this isn't a large component, its a small (1/4 watt) resistor.
To sum up: keep the tip clean and tinned for every joint, solder always flows to heat.
Modern soldering iron tips tend to have special coatings, this is good because it prevents the oxidising as quickly as they used to. This coating is the reason I say you should never file or sand your tip to clean it, once you start that down that route, you will probably have to keep doing it every so often and the tip will be worn out quite quickly. If you look after the tip, it will last a long time.
Now this oxidisation happens quickly when the tip is hot, you can see it because the tip goes from shiny silver to dark and dull, it actually goes quite grey in colour and can almost become black. Now the problem is this layer of oxidation reduces heat transfer. Some people don't realise just what an effect this has and keep trying to solder with the iron in that state. The problem is, you will struggle to make a single solder joint with a tip like that. The secret is to clean it before every joint. Well sometimes you can do a few joints straight after each other and I would usually at least do both wires of a resistor for instance, but you can't just keep soldering without cleaning the tip.
Now cleaning can just mean wiping the tip on your scouring pad a couple of times, so no big deal. But if the irons been sitting for a few minutes you need to go a bit further. You need to clean and then 'tin' the tip. The 'tinning' prevents the oxidation of the tip and to do it the tip needs to be hot and clean. So you pick up your hot iron, wipe the tip on the scouring pad a few times and then immediately melt solder onto the tip to tin it. Don't be shy with the solder, it's cheap and it will drop of the tip as you do it, but some will stick, kind of 'paint' the tip with solder and then wipe the excess on your scour, then do your solder joints straight away. If you put the iron down for a minute after tinning it, you will probably just need to wipe it on the scouring pad again and then you can solder. But wait too long and you will need to clean and tin it again. This is why it's a good idea to load a board up with say all the resistors and then solder them all in at once instead of putting one in, solder it, put the next one in etc. That way you can do a few joints, wipe clean and do a few more etc. By the way, you should tin a new tip the first time you use it, before the iron gets hot for the first time the tip will be shiny, it heats up and starts going dark, clean it and tin it.
It's not really that difficult and with practice it will become second nature, you will get to know when you need to tin the tip and when you can get away with just wiping it. Be careful though wiping it enough will always clean it, but it shoud be shiny after wiping it, or it will oxidise very quickly. Now that tip refresher I mentioned is great for this, instead of tinning the tip the long way, you just dip it into the solid refresher, it melts and cleans and tins the tip instantly and you just give it a quick wipe on the scourer and keep going. I find the tip refresher lasts longer between tinning than using solder, so its worth the little bit it costs. Plus it lasts for a long time. Check the close up picture of the tip, the top one is oxidised the one below is after tinning, it should look like this whenever you go to solder.
Now the idea with soldering is you want to get both of the things you are joining hot enough and then introduce solder. Don't load up the tip with solder and try to transfer it to the joint. You should touch both pieces you want to join with the tip at the same time and hold it there for a couple of seconds to allow them to heat up. Now the best way to work out what you should be heating is to remember a simple rule.
Solder will always flow towards heat.
So hold your iron on the join for a second or two, then introduce solder into the join, it will melt when it touches the iron, as soon as you see the solder flow into the joint, lift the soldering iron away. Don't jerk it away, just lift it off.
Now to do this well you need to have everything secured in place so you can hold the iron in one hand and the solder in the other. No balancing tricks (until you know what your doing and can get away with it). This requires having everything held in place by its own weight or under tension or with a clamp, or whatever, no chasing parts around the bench with a hot iron.
By the way, check the pictures I put on this step of an example joint, it should look something like this (not great as I was trying to take pictures at the same time) it should have a slight concave to the solder join and be smooth. In the second picture you can kind of see how I'm holding the tip onto the copper pad and also against the resistor lead close to the pad. Notice the size of tip I'm using, it's the standard tip the iron comes with, not exceptionally fine. But this isn't a large component, its a small (1/4 watt) resistor.
To sum up: keep the tip clean and tinned for every joint, solder always flows to heat.
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