Soldering basics guide

[zlab]

Hello to everybody! In some other thread we discussed that it wouldn't be bad to make some sort of guide on basics of soldering. In advance, please excuse me for all the grammar, as English is far from my native language. Also apologies for maybe using  some American words, you know for us it is difficult to strictly use one accent when speaking English.

 

Through this thread i will try to explain some basic techniques through different topics of soldering. It should be helpful on the RCs and so as on the other repairs and DIYs  around your house. For now i had in mind those topics, we can add some latter if there will be an interest.

1. Understanding the soldering process

2. Tools and materials

3. Do's and don't s

4. Soldering the end of the wire

5. Soldering the wire to the connector

6. Soldering 2 wires together

7. Stupid exercise

 

Edited February 11, 2020 by zlab

[zlab]

1. Understanding the soldering process

About the deffiniton of soldering I recommend to read the first paragraph on the Wikipedia. https://en.wikipedia.org/wiki/Soldering

Soldering proccess that we will use is soft soldering, which requires the least temperature. You also have hard soldering proccess, where much higher temperatues are involved and is commonly used for hot water plumbing.

You have various different soldering materials, but for our applications we use Sn/Pb type solder.  Commonly used solder is 60/40 Sn-Pb, which means 60% Tin, 40% Lead. In European union the use of Lead in new devices is prohibited by the ROHS directive. I think that me speaking out loud of what i think about that, would be inappropiate as there are also children on this forum… Nowadays lead free electronics are way less reliable than the electronics made 20 or 30 years ago. I find a lot of failures in industrial electronics due to cracked soldering joints. It is very difficult to find a bad joint, as all the joints seems bad on first look.

Avoid lead free solder for all costs, get yourself a proper stuff to work with.

 

 

For the solder be able to stick to the base metal, it is very important that the surface is clean and unoxidized. Oxidation is the reason why the aluminium si that difficult to solder, because of the aluminium oxide formed on the surface. That is why we use bare copper and tined copper as normally (if not on excesive moist) the oxidation is very slow.

But some surface impurities are allways present, that is why there is allways flux involved in the soldering proces. Flux is a chemical agent that cleans the surface in the soldering process and also hepls to distribute heat on the working material. In most soldering wires, flux is allready present inside the soldering wire (if you will carefully cut it and look closelly, you will see it). We can use additional flux if we want (will be discussed latter).

 

 

Melting point of Sn/Pb solder is somewhere around 190°C. Yes it is that low. This means that there is absolutelly no point of turning your soldering station to the MAX, it won't do anything good.

Pick the right temperature for the application. I usually solder the PCBs on somewhere around 320°C, for some bigger components or if there are large areas of copper on PCBs i go to 350°C.

 

 

 

 

More to follow after the lunch.

Edited February 4, 2020 by zlab

[zlab]

2. Tools and materials

Many are in doubt what to buy and what to use for soldering. Well it sounds easy, soldering iron and solder right? We can always complicate things a bit.

On the picture you see the basic tools that i am using for this guide.

-Soldering station

-Solder

-Pliers and cutters

-Flux

-Rubber band

- Manual desoldering pump

 

There are no special jigs for the connectors used here. If you have one, then use it.

 

Soldering station

I intentionally choose to show this particular soldering station, even though i have way cheaper soldering irons and also way better ones.

This one is ERSA ANALOG 60A, it is somehow professional, but i choose to show it because this was my first soldering station. I bought it when i started high school, 17 years ago, saving money for it many many months. It is that old and never had any problems with it, i made all my electronic projects in high school, used it for many repairs latter and it is still in use.

If we sum it, new one is worth around  250-300€. It is 17 years old. It costed me less than 1,5€ per month, and i am sure that it will work for many years to come.

Tips are just amazing. I have new ones, but i choose to show you the tip that came with the soldering station and was in use all this time (you will see it latter on the pics and vids).

You can basically use any soldering iron you want. You can solder with the one for 15€ and with one for 1000€. It is HOW you will solder. I really recommend you a temperature regulated soldering iron, there is no need to be in the 300€ range, but let it be a decent semi-pro soldering station. I've heard HAKKO are good, haven't tried any so can't judge. We use mainly ERSA and WELLER.

 

Power counts, but it is not everything

You really want to avoid low power station (15W and so), look something in the 60W or more. 60W should do majority of work if the technique is correct.

When you start the soldering process the heat energy is transmitted to the solder and work piece.  Good temperature regulation will instantly increase the power on the heater to compensate the energy loss and try to maintain constant temperature. If the soldering iron is poorly designed, there is too much thermal resistance between the heater and the tip. This will result in tip temperature to fall to much and very difficult soldering of larger work pieces. This is a common reason that some cannot solder a particular connector and another guy has no problems with the same power but different soldering iron.

 

Ergonomics of the handle and the cable

 

For some quick soldering it doesn't really matter that much, but you still want a nice and light handle. When you solder more (few hours constantly) this really starts to get important. Badly designed soldering handles will make you tired and will heat up, which is really uncomfortable.

The cable should be light one, silicone insulation based. Not only that it is much easier to work with, it will also not burn your cable instantly if you accidentally touch it with the hot tip.

Things that makes an soldering station good:

 

Temperature regulation

As i said, it's good to have a temperature regulation. In the following topics you will see how bad it is to solder with too high temperatures. It will melt your connectors, damage your insulation, burn the flux, destroy the PCB and many other bad things.

There is no need to buy one with digital display just because it looks fancy. The pot knob works just fine, there is no need to adjust it in the 1°C tolerance.

 

Solder and flux

Some of that was already discussed in the 1st part of this guide. Again, avoid lead free solders. Best to start with is 60/40 Sn/Pb.

I use Stannol brand for many years now, it's good and available from local supplier.  What makes a solder a good one is its consistency and more importantly the flux that is used inside. Most of them are rosin based which is acidic when melted (to remove and prevent oxidation in soldering process) but inert when solidified. Avoid acidic fluxes are they will damage the PCB over time. The rosin one you can leave there and it wont do harm if solid.

Stick to branded soldering wire, where you can be sure what is inside. Another point of view on this is your health. You can never know what sort of chemicals will the chinese put in there and you will be in direct contact with fumes. Nevertheless avoid the fumes as they are always a bit toxic, you won't die from the connector or two, but if you do it 8h per day, every day, then it is smart to invest into some fume sucking and cleaning device.

Get yourself at least two different diameters of soldering wire. Here i use 1,0mm, which honestly is a bit small for those RC connectors and wires. Could be 1,5mm for this jobs. The other one shown is 0,5mm that i use for more precise soldering on the PCBs.

On the picture there is also additional flux. This particular one is intended for SMD soldering, but it's currently the only one in my hobby workshop. You will rarely need it, as for the wires and connectors , that one in the soldering wire should do the job.

 

Helpful tools and accesories

It's always good to have both hands free for soldering, right for the handle and left for the soldering iron (or vice versa if you are left handed). Latter when you have enough experience you can learn how to hold the workpiece and add solder with same hand (this also helps to build up your resistance to pain, as you will burn your fingers many time).

Use your imagination. Soldering jigs, third hands, vices, improvised holders, etc.

You can see on the picture an easy hack to hold something. Pliers and rubber band, as easy as it can get.

Edited February 4, 2020 by zlab

[zlab]

3. Do's and don't s 

 

Do it comfortable

I see many people holding the soldering handle extremely uncomfortable.  It is not a screwdriver, it's not a hammer and it will not run away from you. Hold it gently, with your fingers, there are no forces others than the weight of the handle involved in the soldering process.

Take a comfortable position on the chair and choose correct height. It doesn't help you if your back is in pain, neck twisted and fingers white.

 

 

 

Do not overheat

Putting the temperature to the MAX will do more harm than good. As we discussed, 350°C should be more than enough for most jobs. If you go to high with the temperature, you will experience problems with melted connectors and burned flux. If you burn the flux, it will not be able to perform its function and the result is a bad joint.

On the picture bellow you can clearly see the result of too high temperature/too long exposure to the heat. You can see the damaged connector and burned flux (it is the dark residue on the solder). When you will overheat the solder you will also experience problems with the solder sticking to the tip and not forming enough surface tension.

 

Use the right amount of solder

If there is not enough solder, the joint will probably mechanically fail in a short time. If you use too much, it will form a bubble which is there only to make it harder for the heatshrink to put over and also harder to inspect for joint defects.

 

Don't be afraid to heat

Some people could be afraid of that "DON'T OVERHEAT".  They are afraid of melting the connector or damaging the PCB and use too short time of heating the work piece. The result could be a cold joint. If you don't heat it enough, the joint will be mechanically and electrically bad. Not necessary to fail right away, but some vibrations will break it sooner or latter.

Watch how the solder flows and sticks to the surface, you will quickly see where is that point where the work piece gets the right temperature and the solder just flows everywhere.

On the picture there is a typical cold joint. You can clearly see that it just sticked on top of that wire and connector just like a chewing gum and waiting to fail.

 

 

Solder the workpiece

I have seen many people melting the soldering wire on the tip and than putting this on the work piece. This won't do anything. Only melt a small amount in the initial stage of the process, but later melt it on the workpiece itself. You will see it later on the videos. It will help to distribute the solder and flux.

 

Keep your tip wet

You want to keep your tip wet all the time, as this will prevent the tip from oxidation and increase it's lifetime. Right before you start to solder, clean that old solder away with the wet sponge.

 

Don't modify your tips

People have many ideas when it comes to modifing and repairing stuff. Don't grind your tips, that is a bad idea. Tips have a coating which is preventing it from oxidation. If it is damaged buy a new one. If you need a thinner one, buy a new one

 

Edited February 4, 2020 by zlab

[zlab]

4. Soldering the end of the wire

Soldering the end of the wire is the basic and the easiest job here. If you have the tip of the wire soldered it will help you later for easier soldering to the connector.

As you will see in the video i first add some solder to the tip to get the flux flowing into the wire. This will help to quickly transfer the heat through the rest of the area we want to solder. Later you can see that i don't add solder to the tip, but directly to the wire, because we want to solder that as quickly as possible, not to damage the insulation. As soon as the copper heats up enough, the solder will melt. If you cannot melt the solder like this, then you don't have enough power on the soldering iron/to much heat distribution from the iron.

You can see that i wait for the solder to simply flow to all the areas i want to solder.

Keep in mind that this is a 6mm2 wire (10AWG) and 60W soldering iron, thus it takes a little longer to do it.

 

 

 

DON'T use soldered wire for screw terminals!

I have seen many people to solder the end of the wire for the screw type terminals. There is just everything wrong with that and is prohibited on all power electrics in industry or at home. Because solder is relatively soft it will deform under the tension from the screw over time and cause a bad connection. The best scenario is a malfunction and the worst one is the fire...

Always use wire ferrules and appropriate crimping tool.

Edited February 11, 2020 by zlab

[zlab]

5. Soldering the wire to connector

This is where you really don't want to overheat. I will use XT60 and XT90 connectors. Base of this connectors is made from nylon. I don't know exactly which nylon, but keep in mind that PA6 has a melting point of 220°C and PA66 melts at around 270°C, so we are pretty close here to melt everything.

On the first video you can see XT90 connector and 12AWG wire. Again, i add solder first to the tip while holding it on the wire, and then adding solder directly on the wire. Because there is a lot of heat distributed on those pins it takes quite a long time to reach the temperature where the solder begins to melt. You can see, that i check it with the soldering wire and when it begins to melt on the connector it means that we reached the temperature there. Then the solder quickly flows to the pin itself. On the end i wait a second or two to be sure. Let it cool on the table, don't move the connector and wire, if the plastic started to soften around the pin, you will deform it and you have a bad connector. Just let it cool so the plastic around the pin hardens again and keeps it's original form.

 

 

If the wire is relatively thick for the hole in the connector pin, you will need to do it with the bare wire, so you can squeeze it in there.

On next video we have a XT60 connector and 6mm2 wire (10AWG).

You can see that i added some flux there for faster distribution of the heat. Yes it takes quite some time, but first the wire must heat up, as it is quite a lot of heat distribution there. I am always keeping the tip on the wire and not on the connector itself. This will help you not to damage the connector, as the temperature on the pin will be just right, when you see solder flowing there.

 

 

[zlab]

6. Soldering two wires together

Easy job that can be frustrating if you do it wrong. Twist the wires in the way that takes the least thickens, otherwise you will end up with fat joints.

Don't take the video for the reference, I'm sure that you can do it better. I was in a hurry and now i see that it really doesn't look good on the video 🤦‍♂️ Make it thinner and straighter.

 

 

[zlab]

7. Stupid exercise

When i started my high school i can say that i already had quite some practice with soldering. In the first year we had 4 hours per week for the practical part of the knowledge in the school's workshop. After many hours of basic drilling, grinding it was finally time for some soldering. I will never forget when the teacher said that we will do some soldering for the evaluation. I will never forget how stupid was that particular exercise to us.

 

So here you have it. The stupid exercise. You will learn how to hold your soldering iron for precise moves and how to hold it where it needs to be. It will also help you to build your pain level, as it will burn your fingers probably. You will learn, that even if it burns, you must  wait for the solder to solidify. When you do it, make the cube smaller. And then again, smaller than the previous one. With this you will learn how to heat just right, as if you will overheat, another joint will melt...

 

First find a solid copper wire. They are used for domestic installation in this part of Europe and i had some laying around. I used 1,5mm2 wire, which is around 16AWG.

Strip the insulation and make sure that you used a straight piece. Cut 12 pieces of same length, you can start with 5cm long pieces.

 

Then make a cube out of it.

 

 

 

 

That one was done in around 10 minutes, so don't take it for reference. Make it better. Watch for cold joints.

 

Edited February 11, 2020 by zlab

[GMballistic]

Fantastic that you're putting in all this effort @zlab to help show others some soldering techniques. 

 

Regarding jigs something very easy that I use is a small block of wood.

This is good for two reasons because firstly the wood doesn't draw heat from what you're soldering which is a problem when using anything metal and secondly it's good because you can drill holes in the wood to suit the type/size of connectors. 

 

Look forward to reading more. 👍

[Paul Busby]

Incredible post mate.

 

Actually made me feel a bit better about the way I have been doing things, as I often doubt my techniques when I see people give tutorials that show all these different ways.

 

I learned from the pros, I really shouldn't have in hindsight.

 

Definitely take a few things away from the lessons here and will save this as a solid reference for the future.

 

Edit - The Hakko 888 is a great high quality low cost station with temp control. Very comfortable iron.

Just watch out for fakes on eBay!

 

The standard tip is a bit pants for RC connectors but they're easy to change and only a few quid.

 

 

[shaunm]

Thankyou for your efforts I learned a great deal much appreciated!!

[Shergar]

Zlab, excellent advice  - I've not need to solder since the  last century, its nice to see some advice  that didn't start and end with buy a 1000W soldering sation from Hakko.

 

Now to melt my way through several XT connectors till I master things 🔥

[robertmurr]

Hi, what can you say about these Butane irons, is it a good choice if you need to solder wires without access to electricity, or is it better to take a battery?

[turok007]

23 hours ago, robertmurr said:

Hi, what can you say about these Butane irons, is it a good choice if you need to solder wires without access to electricity, or is it better to take a battery?

Hi  i use a solderpro 120  and it can do XT90 plugs easily   never had any problems

[Bert_w164]

Already said, but I'll echo it, leaded solder with a good flux core *really* makes a huge difference. Going from all sorts of non-leaded random solder to some branded Loctite leaded solder is a wholly different experience altogether.