Even as a part-time nerd you will not really get around the soldering iron in the long run. At the latest, when the first test circuit on the breadboard has worked well and you want to take the next circuit evolutionary step, it’s time to swing the soldering iron.
As a child, I had terrible respect for this thing for a long time. It’s hot, it stinks and smokes and as a layman you always have a kind of bad conscience about what you’re doing right now.
I still have respect. I think that is quite appropriate. Because when soldering you can still break a lot. Both on your own body as well as in the circuit to be built or repaired.
When soldering, it is therefore much on the dosage. Because it’s not just the temperature must be right, also some components may not be heated too much. At the same time, however, there must be enough temperature to connect the component electrically – and often mechanically enough – to the carrier board (PCB). This also includes the right solder, which should be applied sufficiently. But again it makes the dosage: too little and the component falls off. Too much the component holds great but there may be short circuits.
You see, there are a few pitfalls waiting for you. To give you an easy introduction to the world of soldering you will find below a few tips for the right choice and the correct handling of the soldering iron.
Hints for our lovely english readers: Basically, many of the articles on Nerdiy.de are translations from the original german articles. Therefore, it may happen here and there that some illustrations are not available in english and that some translations are weird/strange/full of mistakes or generally totaly wrong. So if you find some obvious (or also not obvious) mistakes don't hesitate to leave us a hint about that in the comment section.
Also please don't get confused, that instead of a "dot" often a "comma" is used as decimal separator. 🙂
- 1 Safety instructions
- 2 Affiliate links / advertising links
- 3 Requirements
- 4 Safety
- 5 Construction and correct posture of the soldering iron
- 6 Soldering iron vs. soldering Station
- 7 Soldering with hot air
- 8 Power of the soldering iron
- 9 Duration of soldering process
- 10 Solder/solder what makes sense, what is allowed and how much is needed
- 11 The right pad
- 12 PCB holder, third hand and Co.
- 13 Temperature is important, too much is bad
- 14 Cleaning the soldering iron
- 15 Cover critical posts
- 16 Clean the solder joints after soldering
- 17 General procedure during soldering
- 18 Simple exercises and tips
- 19 Solder SMD and THT components
- 20 Loosen/remove soldered components and clean contact points
- 21 Additional information
I know the following hints are always a bit annoying and seem unnecessary. But unfortunately, many people who knew it "better" from carelessness lost their eyes, fingers or other things or hurt themselves. In comparison, a loss of data is almost not worth mentioning, but even these can be really annoying. Therefore, please take five minutes to read the safety instructions. Even the coolest project is worth no injury or other annoyance. https://www.nerdiy.de/en/sicherheitshinweise/
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Additional information about different soldering techniques can be found in the following articles.
Electronics – Solder SMD parts by hand
Electronics – Solder THT components by hand
In the following list you will find all the parts you need to implement this article.
In the following list you will find all the tools you need to implement this article.
Words about security are often overlooked because security measures are always accepted as necessary only if one has already been injured. To prevent this from happening, here are a few admonitory words. 🙂
When soldering, there are basically three and a half serious dangers:
1. The tip of the soldering iron gets very hot. This produces temperatures of 200-500 ° C. So here is a significant risk of burns. So make sure you do not touch the tip and the associated metal parts. Also take special care not to leave the (hot) soldering iron with children alone. Especially forbidden things make children often curious.
2. The hot tip is not only a significant injury potential. This can also trigger fires. Never leave the switched on/hot soldering iron unattended. Under favorable conditions, a fire can spread so far within a minute that it can not easily be extinguished.
3. The normally used solder contains a flux flux. This is necessary/useful because it favors the bonding process of the solder with the metals of the respective contact surfaces. Sometimes, however, it can also happen that the solder “splashes” so parts of it fly uncontrollably. So take care that during the soldering process you do not have any sensitive parts (such as a smartphone display or bare skin) in the vicinity that could be damaged. A goggle is annoying but at the same time much less annoying than a serious eye injury.
3.5. During the soldering process, and especially during the melting of the solder, various fumes and gases are produced. Make sure that these gases are either vacuumed or the room where you work is well ventilated. The best is a combination of both. During soldering you can also try to blow away the ascending solder smoke. In any case you should avoid inhaling the soldering smoke.
Construction and correct posture of the soldering iron
A soldering iron is actually always based on the same principle. A simple soldering iron that can be operated even via USB is displayed in the following picture.
The tip of the soldering iron is at the foremost end. It is mostly interchangeable and available in different sizes and shapes. So there are tips that are very suitable for soldering SMD components and also tips with which gutters can be soldered. 🙂
The tip of the soldering iron is also usually specially coated so that the solder on this – at least something – sticks. For this purpose, the tip should also be cleaned well before each soldering. But more on that later.
2. Heating cartridge
Immediately after the end comes another metallic tube. This usually includes a heating cartridge and a temperature sensor, both of which are thermally coupled to the tip of the soldering iron. This ensures that the metal tube, cartridge heater, temperature sensor and tip always have the same temperature. With the help of the temperature sensor, the temperature of this (heating) unit with many soldering irons is precisely controlled down to a few °C.
The handle allows you to neatly guide the tip of the soldering iron. It insulates from the high temperatures of the heating unit and is usually made very grippy by a rubberized surface. The handle is also the only part of the soldering iron you should touch.
4. Connection cable
The connecting cable hangs as a more or less annoying appendage at the other end of the soldering iron. For this purpose, the soldering iron is supplied with the necessary energy to bring it to the desired temperature. Often, this also sends the current values measured by the temperature sensor back to the soldering station. Here you should always make sure that the line is not kinked or knotted. Besides, she should not come into contact with the hot soldering tip.
Posture of the soldering iron:
The posture of the soldering iron is actually quite easy. Hold this like a pen you want to write with. Keep it as far as possible at the front of the handle of the soldering iron. Of course, make sure that you do not accidentally touch the hot tip of the soldering iron.
Soldering iron vs. soldering Station
The “soldering iron vs. solder station” question can not be answered so flat. In most cases, a normal soldering iron is enough. If you already have a soldering iron at home and only occasionally use it to connect leads, for example, you do not need to buy a new soldering station. Most advantages of soldering stations usually only become apparent when you regularly use a soldering iron or want to handle more specialized tasks.
The big advantages of a soldering station compared to a standalone soldering iron are:
- The soldering iron (hand pieces) are often lighter
- The connection-wires are longer and more flexible, making it easier to work with
- The temperature can be set (more precisely)
- Display of the current temperature is possible
- Earthing connection for protection against ESD is possible
- Many soldering stations have an integrated (stable) holder for the soldering iron incl. a holder for a cleaning sponge
You see, these are not all “killer arguments” against the soldering iron. Only in the case that you want to solder components that have very critical temperature requirements, it may be necessary to buy a soldering station with adjustable temperature. In most other cases, the soldering station is simply the more luxurious version of a soldering iron.
Only with special (very small) SMD components you will need a soldering iron with a very fine tip. Due to this possibly forced new investment, most land at the latest at a soldering station.
Soldering with hot air
In addition to soldering with a soldering iron (also known as contact soldering), there is also the option of soldering components with hot air. The entire component, including the circuit board, is heated, and the previously applied solder or solder paste merges with the circuit board and the component.
This is mostly used when soldering SMD parts. Information on this can be found in the article Electronics – Solder SMD components by hand
Power of the soldering iron
In addition to the adjustable temperature range or the temperature of the soldering iron and the power is a factor not to be neglected. While the temperature indicates how hot the tip or the (thermally) bonded solder/soldering pad/component/line becomes, the power (figuratively) indicates how quickly this “heat” can be replenished.
Because basically any metal part, which is thermally conductive connected to the tip of the soldering iron, the heat from the tip. The larger this part is (for example, a large mass area) the faster this heat is dissipated. If this happens faster than the soldering iron is able to track the heat, the tip and thus also the parts to be soldered no longer reach the desired temperature.
In this case the component to be soldered acts like a heat sink for the tip of the soldering iron. If the power of the heat sink (ie the ability to emit heat energy) is now greater than the thermal energy supplied to it (by the soldering iron), the coupled system of soldering iron and heat sink becomes colder overall and not warmer.
You can tell quite quickly that the solder at the tip of the soldering iron melts very well, but then very badly connects to the component or conductor/solder pad. This is because the soldering iron fails to heat the trace/solder pad fast enough to the melting temperature of the solder. In this case, often only helps to put on more power(https://www.youtube.com/watch?v=YQwYNca4iog). But sometimes you are lucky and it is enough if you increase the target temperature of the soldering iron something. Implied you have the opportunity to adjust the temperature and the components used tolerate the higher temperature.
Duration of soldering process
In short, a soldering process should always be as short as possible but as long as necessary.
So you should avoid frying components. If you are unsure about the temperature of the component you are using, you can also take a look at the relevant data sheet. There, the permitted temperatures are listed with the respective action times. If in doubt, let the component between the “soldering” just cool down a little before you start the next attempt.
You should also be careful with solder pads on printed circuit boards (PCBs). These can be detached from the circuit board due to high and long-acting temperatures. Again, help: If in doubt, let everything cool down a bit, get a fresh coffee and then try again. 🙂
Solder/solder what makes sense, what is allowed and how much is needed
Lot – or colloquially also solder or solder wire called – is in the soldering principle “the adhesive” to connect two other metals together. Of course, the principle of soldering and gluing is completely different, but it illustrates quite well what the solder is needed for soldering. Ideally, a good solder joint will result in two metal parts (e.g., two cable ends) being electrically and thermally (sometimes mechanically) connected together stably.
In order for the solder to fulfill its connecting task, it must first be heated. For this it is important that the melting temperature of the two metals to be joined (e.g., two cable ends) is lower than that of the solder. This reduced melting temperature is achieved by a special mixture of different metals – also called alloy. The molten solder then flows into all the cracks between the metal parts and connects them together. This is where the name “soldering tin” comes from, because many solder alloys often contain much of the metal tin.
Thus, we already come to the first important property of the solder: the alloy. Because this determines an important property of our solder: the melting temperature.
The composition of the solder is always indicated but unfortunately only a bit “encrypted” readable. Some examples:
This information is used to indicate the composition of the particular solder. The abbreviated name of the element or metal followed by the relative quantity is always specified first. For example, if you have a solder marked with Sn60Pb40, it means that it is 60% tin (Sn) and 40% lead (Pb). Sometimes the second relative quantity is omitted. This means that the latter element meets the remaining quantity. For example, Sn60Pb40 is the same as Sn60Pb.
Another property of the solder is the diameter. Especially for the soldering of very small components as with SMD components, it makes sense to use a very fine solder wire. In order to be prepared for most soldering operations, it is often sufficient to have a normal and a very fine soldering wire in stock.
A “very fine solder wire” would be a diameter of 0.3-0.5mm.
A “normal solder wire” would be a diameter of ~ 1mm.
Another important feature you should consider when buying solder is that it is provided with a flux soul. In principle, a solder wire is not a “wire” but a “tube” only in a very small and therefore poorly visible scale. This tube is filled with flux inside, which improves the flow properties of the solder. Without this flux – which often evaporates completely during soldering – the solder would flow much worse between the metals to be joined and connect to them. So always make sure that the solder you use also contains some flux.
In the following a close-up of the flux medley soul in a solder wire.
The amount of solder is similar to the duration of the soldering operation. The quantity also applies here “as much as necessary but as little as possible”. In productions, one tries to keep the amount of solder used as low as possible, as the costs are kept as low as possible. This argument is usually not so critical for the home user, but you should still handle the soldering tin on the local craft table if possible sparingly. But how do you determine the perfect amount of solder?
This can best be explained by a few examples and pictures. These can be found in the section “Examples of bad and good solder joints” below and in the articles Electronics – Soldering SMD components by hand and soldering Electronics – THT components by hand.
The right pad
One thing I personally still find important is the pad used. During soldering, sometimes the board, vias and other points are heated so much that the underlying surface is quickly damaged.
You should therefore make sure that you do not use an easily combustible or deformable pad made of plastic or similar. Also, a metal backing is not always suitable because it could extract heat from the soldered point on your PCB.
So, if you do not have any extraordinary ESD protection requirements for your project, I recommend a simple solid wood panel. Of course it is not really flammable, but until such a wooden plate burns you have to leave the (switched on) soldering iron unattended for a very long time. And that’s something you should not do in general. 🙂
PCB holder, third hand and Co.
Often it is also recommended that you should clamp boards and Co. during the soldering process in special brackets or otherwise lock. But these brackets are not really convincing. At least not for soldering components on a circuit board. Often, the brackets make the handling of the board more complicated than without a bracket. Because to solder components you have to put them first from the top through the board in order to solder them from the other side. This has the consequence that you constantly have to remove and reinsert the board from the holder.
How it is easier with “home remedies” is described below.
In my opinion, a piece of Sticky-Tape is best for attaching components to a printed circuit board before soldering.
Simply insert the component at the desired position from above through the PCB and attach it with a small strip of adhesive tape.
Then you can turn the PCB over and solder the component contacts to the PCB.
If someone needs a “third hand” when soldering, I recommend the following. The big advantage of this is that you can clamp them to the table top edge. Thus, the holder does not fall around and offers much better grip than the freestanding brackets.
Temperature is important, too much is bad
The right temperature is a bit of a double-edged story. Of course, this must be high enough to melt the solder. Without molten solder, the solder does not work.
The disadvantage of the high temperature, however, is that it also transfers to all metals during the soldering process, which are connected during the soldering process. For example, if you want to solder an SMD component to an SMD pad, both the solder and the SMD component and the SMD pad are heated to the set soldering temperature during the soldering process.
Some components can handle this “thermal load” (high temperature effect) well, some less. All in all, it is advisable to keep the soldering process as short as possible but as long as necessary.
Often you will find information about the maximum permitted soldering temperatures in the data sheets of the respective components. For example, the following two pictures are excerpts from the datasheets of the WS2812B RGB LED’s.
Cleaning the soldering iron
An important prerequisite for a successful soldering process is a clean tip of the soldering iron. Especially when it comes to filigree soldering as SMD soldering you should make sure that your soldering tip is cleaned before each soldering.
Soldering and flux residues, which make the transfer of heat and sometimes even the view of the “operating area” more difficult, are quickly eliminated by previous soldering operations.
There are basically two options for cleaning the tip.
The first possibility is a damp sponge where the residues can be removed at the top. Pull the soldering iron a few times from front to back over the moistened sponge.
The second option Consists of so-called “dry cleaners” which are very reminiscent of metal rinse sponges. In these, the soldering iron is simply dipped two to three times in the interwoven metal fibers until the tip is clean.
IMPORTANT: The tip of your soldering iron is specially coated, so you should never treat it with sandpaper or a file when it is cold. Otherwise it may happen that you remove/damage the coating and then the solder no longer holds at the top.
Cover critical posts
In some cases, it may be useful to tape certain unused parts on the board. This protects your sensitive other components from solder or flux splashes. Which in the best case look ugly and in the worst case can cause short circuits and destroyed components.
Almost every tape is suitable for this. If you want to play it safe, it is recommended to use “Kapton tape”. This is temperature resistant and can easily be detached again.
Clean the solder joints after soldering
After soldering components to printed circuit boards, residual flux often remains in the form of dark yellow/brown impurities. These are not tragic from the mechanical and electronic side but often look ugly or unprofessional.
But there is an easy way to remove them. The impurities are easily dissolved by alcohol. Just put a drop of isopropanol on a cotton swab or cloth and remove the contaminants.
General procedure during soldering
Electronics – Soldering of SMD components by hand and Electronics – soldering of THT components by hand is described in detail in the soldering of THT (ie “through-hole”) and SMD components. In general, however, each soldering process can be divided into the following steps.
- Determine the maximum soldering temperature of all components involved in the soldering process and (if possible) set the soldering iron.
- Heat soldering iron and clean tip.
- Provide suitable solder – adapted to the size of the solder joint.
- Mechanically connect the components to be connected (if possible). So position with holding aids or adhesives so that the metal surfaces to be soldered are in contact with each other.
- Apply some solder to the tip of the soldering iron. This later facilitates the heat transfer from the top.
- If possible, hold the point of the soldering iron against both metal surfaces so that both are heated simultaneously.
- Put so much solder on the heated metal surfaces – not only at the top of the soldering iron – to melt until both metal surfaces are extensively connected.
- Remove soldering iron and allow solder, component and circuit board to cool down.
Simple exercises and tips
Extend and connect is the “daily bread” in many craft work. In principle, required cables are almost always too short. 🙂 So here comes a little guide on how to connect or extend lines quickly.
Option 1: You have enough guidance available
With this option, you have enough line available and can strip both ends of each about 2cm. This option is mechanically somewhat more stable and also easier to perform than the following variant.
Option 2: You have little length available
Often it is unfortunately so that you do not have enough wire or cable available to strip the ends each 2 cm. Especially in the case that a line in a device is broken, there is often not enough line available to connect the line ends as described in option 1. So here’s a way with which you can connect even very short line ends together.
Important rule when connecting lines:
The soldered surface should always be larger than the cable cross section to avoid too high transition resistances.
Connect pads to breadboard:
Before the first prototype on a custom printed circuit board or individual circuits are often built on breadboard. Breadboard boards are printed circuit boards on which holes are arranged in a grid. Often at a distance of 2.54mm which equals 0.1inch. This is the quasi-standard pitch for many components.
The nice thing about breadboards is that on the underside of the board (ie the copper side) connections between solder points or components can be made very fast. For this purpose, in principle, a “solder sausage” is placed over the route to be connected.
How you can do this is described in the following pictures.
Components with very large contact surfaces (eg XT60 connector):
The disadvantage of soldering with very large metallic surfaces is that it takes a very long time to bring them to the desired temperature. In addition, the heat supplied is also dissipated very quickly. It can take a long time to heat these parts to the desired temperature. Sometimes you even do not make it, because this (for example, a large ground plane of a board), dissipates the heat faster than you can feed them over the soldering iron.
As a small example Here’s a guide on how to solder leads to XT60 connectors. These connectors are often used in remote controlled devices. The big advantage of these is that they can transmit a continuous current of 60A, which is not uncommon with larger multicopters. Disadvantage is that it is more difficult to solder due to the massive plug contacts and the massive leads to connect both together.
The difficult thing is that you can not or only very difficult tin both contact surfaces individually and then solder. It usually takes a long time to reheat the already tinned (and solid) contact of the XT60 connector and connect it to the connection cable. The trick is to heat the massive contact (in this case, the XT60 connector), tin it and then let it cool down only when it has already been merged with the connecting cable.
First, clamp the XT60 connector in such a way that you have both hands free. For this purpose, a vise or a third hand is quite good.
Examples of bad and good solder joints:
Various solder joints in a THT component:
In the following you see a pin header/pin header in which various errors were made when soldering the pins.
First, second and 4th were not soldered / forgotten
3rd and 5th was only partially soldered. Solution: Heat again and add a little more solder
6. Good solder joint
7. Good solder joint
8. Too little solder: Solution: Heat again and add some solder
9. Too little solder and only partially soldered. Solution: Heat again and add solder
10. Good soldering a little more solder would not hurt
11. Too much solder. Solution: Vacuum/remove solder with desoldering pump or soldering wire
12. Cold solder joint. Solution: Heat again and if necessary add some solder
Bad solder joints on SMD components:
Especially with SMD components in which the contact surfaces are often on the side and at the bottom of the components, it is not always easy to see whether the components are soldered properly. Sometimes, however, a close look is enough – if necessary with a magnifying glass, a microscope or a magnifying camera.
Solder SMD and THT components
You probably have it. already noted: About the soldering one can really write a lot. And because the soldering of SMD and THT components also differs again, both are described in the following separate articles.
Loosen/remove soldered components and clean contact points
Just as there are when soldering components with circuit boards, cables and Co., there are also some things to consider when soldering and removing already soldered components. Especially if you want to explode old devices or still want to use the components a few things have to be considered. More information can be found in the following article.
I hope everything worked as described. If not or you have any other questions or suggestions, please let me know in the comments. Also, ideas for new projects are always welcome. 🙂
P.S. Many of these projects - especially the hardware projects - cost a lot of time and money. Of course I do this because I enjoy it, but if you appreciate it that I share these information with you, I would be happy about a small donation to the coffee box. 🙂