How to choose a soldering iron and what to look for

What kind of soldering irons are there?

Soldering irons vary in heating, design and purpose. There are both gas and arc ones. But it is electric soldering irons that have gained the greatest popularity. In this article we will look at different types of soldering irons and soldering stations, and their features.

We will mainly consider tools for soldering electronic circuit boards, rather than water pipes and massive structures.

Types by heater type

The heater is the most important element of a soldering iron; carefully study it when choosing a tool. There are gas and electric heaters. The former do not require connection to any networks, but during operation they emit fumes that are harmful to health. In addition, they are not suitable for small jobs - radio amateurs are better off choosing a soldering iron with an electric heater. Now they are much more widespread than gas ones and are made from a variety of materials. For example:

• Made from an alloy of chromium and nickel (nichrome)
  - in the shape of a spiral. Inexpensive, reliable, durable, but they take quite a long time to heat up before use. Overall this is a good option for home use.
• Made of ceramics
  - has a straight shape. It is more expensive and very fragile, requiring careful handling. At the same time, it heats up much faster than the nichrome spiral analogue.

For soldering at home, you can also choose soldering irons with a pulse or induction heater. The first ones are optimal: strong, durable, heat up quickly, but are quite expensive. The second ones are generally practically professional. They are placed on blowtorches and stations.

Copper and “eternal” stings

Before reviewing the soldering irons themselves, you need to give a general idea of ​​the main types of tips and their differences.

There are copper tips, and so-called non-burning “eternal” tips.

Features of copper tips

Copper tips are the most common type of tips. However, today they are losing ground to other types of stings. Let's look at the pros and cons of copper tips.

Pros of copper tips:

• Low price;
• Available at any radio store;
• They heat up faster and lose heat more slowly;
• Copper blades are low maintenance. They can even be cleaned with files;
• Copper tips can be machined, i.e. give them shape with a hammer;
• They make it easier to start your journey in soldering.

And yet, the disadvantages of copper tips are quite critical:

• A meager set of stings in shape and size. Even if you find a thin copper tip. then it will quickly lose its shape;
• There is also the need for tinning before work. It's not difficult, but it takes time;
• Copper tips quickly lose their shape due to high temperatures and need to be replaced.

Care of copper tips

It's time to forget about cleaning the tip with wooden planks. For these purposes there are sponges and copper shavings.

Caring for these stings is simple. Excess solder and soldering flux residues can be removed with a damp sponge. And with the help of copper shavings you can remove both excess solder from the tip and carbon deposits from its surface.

As a last resort, you can process the surface of the copper tip with a file.

You can also give them the desired shape using a hammer and anvil.

They are easily deformed by light blows with a hammer.

Copper tip tinning

Before you start soldering, the copper tip must be tinned, i.e. Cover the work surface with a small layer of solder.

Without tinning the copper tip, soldering will be difficult.

Leading fireproof tips

This is a type of tip (they are also called “eternal”) that does not need to be tinned before starting work, does not lose its shape, and can be used for years. They have a special coating, usually a thin layer of nickel alloy. These types of stings have their own significant advantages and disadvantages.

Advantages of fireproof “eternal” stings:

• Can be used for a long time;
• There is no need to tin them;
• Wide variety of different shapes and sizes;
• High-quality tips keep their proper shape for a long time.

Flaws:

• It is strictly forbidden to clean such tips with a file, needle files or sandpaper. You risk destroying the non-burnable surface of the sting. An exception is copper shavings for cleaning carbon deposits and excess solder;
• The tip gives off heat quickly and gains it more slowly, unlike a copper one (strongly dependent on the design of the tip and the soldering iron as a whole);
• Very easy to care for. Beginners may have difficulty with them;
• Non-burnable surfaces are easily corroded by soldering acid;
• It is more difficult to get used to them after copper stings.

Caring for unburnt tips

Non-flammable tips cannot be handled or cleaned with any tools.

You can clean the surface of the tip from excess or old solder with a damp sponge.

The sponge should not be too wet, otherwise there will be splashes and steam. You can remove oxides and excess solder from the tip with copper shavings. Copper shavings do not damage the coating of the tip.

But the main thing to remember is one rule - there should always be solder on the tip. The exception is when you need to remove excess solder from the board or parts.

We removed the braided solder from the board contacts and immediately applied new solder to the surface of the tip.

Solder on the tip protects the working surface from strong oxides that arise during soldering due to air.
If the tip is covered in oxides, then solder will stop sticking to its surface. It can be re-tinned, and even restored using a sting activator. Read more in this article. If you had to solder with acid, then immediately after work clean the tip with a sponge or shavings to remove solder, and cover the tip with fresh solder. It is also unacceptable to mechanically process a non-burnable tip or shape it with a hammer (as is done with copper tips).

In terms of a number of advantages, “eternal” stings are in the lead. Just one good quality tip can be used for years, and it will be like new. But not everything is as simple as it might seem at first glance.

Planned sharpening of the soldering iron

In order for the tool to properly fulfill its main purpose, it must be periodically sharpened. The planned procedure involves the following points:

• To sharpen the tip, it is best to use a standard file, which should be held at an angle of 40˚.
• The edge must be left a little blunt, its width should be at least 1 mm.
• If the tip is completely new, then you can use fine sandpaper. These manipulations will help remove patina (a kind of copper oxide that has a characteristic green tint).
• If the craftsman is not satisfied with the factory method of sharpening, then you can remove the tip and forge it yourself, giving it the shape of a curved blade. This procedure has a huge advantage - after treatment, the metal is less susceptible to the negative effects of corrosion.
• If you need to give the tip a finished look, then you can process it with a regular file with a fine notch.

Conditional separation of instruments

All tools (no matter for what job) can be divided into three conditional groups:

1. Tools that require experience to operate. They do not tolerate mistakes, and give a false idea of ​​the craft;
2. Tools that don't require much experience. They will help you learn this or that job, and tolerate the mistakes of beginners;
3. Professional tools that are too good for beginners. They require a lot of experience to realize their rich potential in work, but can also help in training.

Now let's look at examples of soldering irons and soldering stations.

Design varieties

By design, there are three types of soldering equipment:

• Traditional rod
  - the simplest design in the form of a straight rod 15-20 cm long. Convenient for small jobs, for example, soldering microcircuits, wires and radio components.
• Pistol
  - a more complex design in the shape of a pistol, in which the working element is located at an angle. This makes it more convenient to repair lamps and other medium-sized objects.
• Soldering stations
  are the largest, most powerful, professional models for working with large objects, for example, metal or plastic containers, etc.

For almost all jobs around the house, the most affordable rod equipment will do just fine.

The simplest nichrome and EPSN soldering irons

The most popular soldering irons are nichrome soldering irons with copper tips without a temperature controller.

These are old Soviet soldering irons and EPSN. They work very simply.

The nichrome spiral heats up from the electric current passing through it (usually a mains voltage of 230 V). And it heats up the soldering iron tip.

Soldering irons with this design have been around since the dawn of electronics. They are still ideal for soldering wires and simple DIP mounting of large parts on boards. And also for soldering radiators and cooling systems.

Conventionally, 60 years ago they produced more soldering irons. Not every KT315 could withstand huge stings that heated up to 380 ℃. Radio amateurs soldered as best they could. Someone assembled a temperature controller using triacs. And someone wound copper wire over the tip, having previously tinned the edge of the wire. And in this way an even smaller tip was obtained, which was heated from the main one to acceptable temperatures.

These soldering irons are already obsolete. Yes, they are still being produced, but this is due to their cheapness and simple assembly. Of course, modern soldering irons are much better than their previous generations, but due to their features and capabilities, they are poorly suited for thin SMD soldering.

The tip of such soldering irons is usually secured with bolts or nuts with bushings. The advantages of such soldering irons:

• Low price;
• Sold in any store for radios, electricians and apartment repairs;
• They are ideal for soldering wires and large DIP pins.

However, in current realities, such soldering irons have significant disadvantages:

• Even the smallest soldering iron (25 W) overheats boards and parts. It is necessary to assemble an additional temperature regulator to reduce the temperature at the soldering iron tip;
• There is no grounding;
• As a rule, such soldering irons are powered directly from the mains and are not controlled by anything. Yes, you can buy a soldering iron powered by 40 V with a step-down transformer, but the price will be higher;
• Lack of even the simplest temperature display, not to mention calibration;
• Poorly suitable for fine work;
• It takes a very long time to heat up and cool down (heating time can reach 10 or 15 minutes depending on the size);
• Poor selection of stings due to mounting and heating.

Slightly improved soldering irons of this type are currently being produced, but they are not far removed from their ancestor. All the same copper tips, all the same simple design.

The more power a soldering iron requires, the larger it will be. A 25 W and a 100 W nichrome soldering iron differ in size by almost 3 times.

An example of a SPARTA soldering iron. Copper tip, coated. Burns out. Suitable for soldering wires and DIP parts for the first time. The price is only 150 rubles, and a soldering iron stand is also included (albeit very fragile). Copper tips for nichrome soldering irons are of poor variety. Usually these are conical, flat and wave-type stings. All copper tips are solid, i.e. they are heated by a nichrome thread from the outside, not from the inside.

Also, copper tips for such soldering irons can be produced with a special coating, which slightly extends the service life of the copper tip (but not for long). Should beginners buy these soldering irons? Yes, at least because of its price and for the sake of the first experience. You can simply desolder parts with such a soldering iron, solder wires, or assemble simple radio sets. Enough for the first 10-15 hours of practice. These soldering irons are cheap, reliable and simple. And are available in any radio parts and repair stores. You can solder wires and pipes (with high-power soldering irons), but nothing more. This option is not suitable for fine work. Modern electronics are much more complex, so the requirements for installation and soldering irons have changed.

The main thing is to take a soldering iron with a wooden handle, and no more than 25 W. A wooden handle heats up less and does not smell as strong as a plastic one. And it is advisable to assemble a temperature regulator for such a soldering iron. You can take, for example, an EPSN soldering iron.

Basic materials and tools for making a sting

Before you start working, it’s worth finding out what to make a soldering iron tip from. Such items include:

• copper tube with a diameter of up to 8 mm;
• copper wire or brass rod with a diameter of up to 4 mm.

For direct manufacturing you will need the following tools:

• ruler;
• bench vise;
• hammer;
• soldering iron;
• hacksaw for metal;
• taps and dies for thread cutting;
• file;
• knife sharpener;
• pliers.

Modern soldering irons are already soldering stations

What is a soldering station? This is not necessarily a soldering iron + soldering iron set. It can be one soldering iron, but with regulation, configuration, control and temperature indication. Modern soldering irons can fit all this right into the handle. Therefore, such soldering irons can be considered stations. But due to the more familiar format “just a soldering iron and a power cord from it”, it is still perceived as an ordinary soldering iron, and not a station.

A soldering station doesn't have to be expensive. It may even be cheaper than some soldering irons. Further in the article there will be examples of such conventional “soldering stations”. As modern electronics installation has become more complex, the need for different types of tips and temperature control has increased.

Requirements for soldering irons for soldering radio components

To choose a high-quality soldering iron for specific purposes, you need to take into account all the features of the chosen direction. Working with microcircuits is somewhat different from soldering pipes, wires and various contacts. All this is displayed on the tool that is required to perform this procedure.

Different types of soldering iron tips

When considering options for which soldering iron to choose for soldering radio components for beginners, you should pay attention to the following requirements:

• Shape of the sting. When working with radio engineering and electronics parts, you need a soldering iron to have a conical tip. This form is best suited for working with small contacts. Thanks to this approach, it is much easier for the master to desolder microcircuits and solder them in the right place, which are the main operations using this tool.
• Tip material. It is best to choose ceramic models, as they help protect sensitive products from static voltage. Copper varieties are also used and are quite practical, but you have to work with them more carefully. Ceramic blades are easier to clean and get ready for use faster.
• Power regulator. When considering which soldering iron is best to choose, you should pay attention to modern models with a power regulator. This allows you to select the necessary characteristics of the tool for a specific type of work. Thanks to this, you can perform many types of procedures with one soldering iron.
• Compact size. Small models are much easier to control when working with microcircuits. Thick tips, even if they have the desired shape, will not allow for delicate work. Accordingly, a small, lightweight model with a fine tip would be an excellent choice.
• Availability of additional buttons. Buttons for increasing the soldering temperature, which are found on pulse models, as well as in other varieties. They help save energy when working.

Various models of soldering irons

Requirements for modern soldering equipment for 2022

If you are going to solder boards or repair electronics, then the soldering irons and stations are required to:

1. Availability of temperature control with stabilization, indication and adjustment functions;
2. Various fireproof “eternal” stings in shape and size;
3. Sleep and temperature memory functions (so as not to keep the soldering iron constantly on, thereby saving electricity and reducing the load on the tip);
4. Good characteristics of temperature stability on the tip.

Currently, not all soldering irons meet the requirements presented. Let's look at popular soldering irons and stations among radio amateurs and electronics engineers.

Soldering tool

Let's consider the tool that you need to purchase to start amateur radio activities, for mounting/dismantling electronic components.

Nippers (side cutters) - they are required for work; they are convenient for molding excess leads, biting off and stripping excess leads.
Pliers – for crimping/pressing elements of radio electronics. If the pliers have an extended working part, they can be used as tweezers. It is very convenient if you need to pull something out from the board, tighten something, hold a nut or bolt. A technical scalpel with replaceable blades (some use medical or knives) for stripping wires, more expensive than varnish, cutting. A desoldering pump, which is a reverse-action syringe.
If the syringe squeezes out, then this one, on the contrary, retracts. For removing excess solder from contacts and contact tracks, desoldering elements. For the same purposes, you can use a special copper braid, which absorbs molten solder under the action of capillary forces. Braid is a disposable item that runs out and is thrown away (you can’t clean it). Unlike a desoldering pump, which can be disassembled and the solder can be taken out, screwed back on, and used again. Those. This is a universal, reusable tool. If you soldered something wrong, you can remove the soldering and re-solder everything again. There is an electric desoldering pump, which is somewhat reminiscent of a soldering iron and is powered from a 220W network. It is mounted on a pin soldered to the printed circuit board and, under its heat, melting the solder, draws it into its body. But for beginners, a braid and a regular desoldering pump will suffice. This set is necessary and mandatory for use to begin soldering work in amateur radio practice; you cannot do without it in any repair, especially when assembling your own construction kits and complex devices.
The third hand (mechanical hand, holder) is a kind of assistant, we recommend it for use. Consists of: • a tripod, which includes crocodile clips, in which you can clamp the conductor so as not to hold it with your hand. • a small bath in which you can put rosin or solder. • soldering iron holder The tripod of this hand is comfortable, rotates in all directions, and is adjustable in height.

Soldering irons 900 series

The next most popular are CXG soldering irons with HAKKO 900 series tips.

The most popular were the 900M. The sting sizes are given below (sometimes they may differ, especially Chinese copies). These are the most popular fireproof stings. They are sold in almost any radio store, not to mention AliExpress.

The variety of shapes allows you to perform a wide range of tasks for soldering boards and radio components (DIP, SMD and BGA). Numerical and letter designations are practically not mentioned. Typically, stings are named by their visual shape (cone, hatchet, flat, etc.). Compared to conventional tips for nichrome soldering irons, the 900M tips are hollow (empty inside, because they are put on the heating element).

Attaching the tip to the heating element of the soldering iron differs from simple nichrome ones. Here the tip is secured with a nut and bushing.

Installed on a huge number of soldering irons of different stations. For example, on Lukey HAKKO 702, 936, 902, 701, 8586, etc. In addition to Lukey, there are different copies of the station under other names.

However, despite all the advantages, this type of tip has a serious drawback - the gap between the heating element and the tip itself.

But first, let's look at examples of soldering irons with such tips. They are also different.

Soldering iron with blue handle SumSour 220 V from AliExpress

This is practically the most common soldering iron. Usually sold as a kit with soldering tools like this:

Power 60 W. Power supply: 220 V. Temperature adjustment is carried out by turning the potentiometer from left to right. Features a typical 900M series blade mount.

This soldering iron doesn't even have a thermocouple to measure and control temperature. This is an example not from the series of “soldering stations”. This soldering iron only has power control and a power indicator. That's all. There is no real regulation here, much less control and stabilization of the temperature on the tip.

Power adjustment is carried out by changing the position of the potentiometer, which in turn regulates the BT136S triac. And BT136S supplies voltage to the heater.

These soldering irons are sold individually and in sets. It is not recommended to buy sets due to low-quality components. An example of low-quality components from a typical set:

Tweezers are curved. Low quality solder. Even the stings burn out quickly. Yes, stings from AliExpress can also be of good or terrible quality.

The tips from this set quickly lose their shape after a few days of use. The tip in the photo example on the right lasted more than 7 years.

Therefore, soldering with the tips included in the soldering iron kit is not recommended.

The only thing that is really good in this set is a thin copper wire for jumpers, a sponge for cleaning the tip from solder, and a stand for the soldering iron (although it is also flimsy).

Pros of SumSour 220 V from AliExpress:

• Low cost;
• The popular 900M series tips are used;
• There is an indication of inclusion;
• There is power adjustment.

Serious disadvantages of the soldering iron:

• Mediocre build quality due to cheaper production;
• No grounding;
• Not heat resistant wire;
• No temperature control. The temperature is regulated by a triac. There is no thermocouple that would measure temperature in this soldering iron;
• The problem with overheating of the tips from the point above;
• Slow heating of unburnt tips of the 900M series (this is a common problem for all soldering irons with such tips, but here without a thermocouple everything is much more serious);
• There is no temperature display, not to mention sleep mode and other useful and mandatory functions of modern soldering irons.

This soldering iron can solder wires, DIP chips, SMD parts and even BGAs, but it is absolutely not suitable for beginners. Without experience and practice, you can stumble upon serious shortcomings of such a soldering iron. It doesn’t even make sense to buy it for such quality, not to mention sets.

If you already have such a soldering iron, then be sure to buy a new set of high-quality fireproof tips for it. And if possible, it’s better to buy another soldering iron.

Soldering irons GS90D

These are no longer just soldering irons, but full-fledged stations. Available in different capacities.

The control and display board of the GS90D is located in the handle itself. Temperature adjustment is carried out using buttons.

The GS90D is better, and on average 3 times more expensive, than the blue handled SumSour soldering iron shown above, but it still has the same tip problem of the 900M series.

Pros of the GS90D:

• Availability of temperature indication;
• Good adjustment;
• Uses the popular 900M series tips;
• Heat-resistant wire (at first glance this is a trifle, but sometimes due to carelessness you can accidentally burn the wire and not notice it in time. Here the wire is protected from such cases);
• There are additional functions.

Minuses:

• Not the best thermal stabilization;
• Overpriced.

Of course, this soldering iron goes to a new level compared to the simplest ones, but it is not the best choice for beginners. It just doesn't hold the temperature well and has the disadvantage of the 900M series tips.

Soldering station Lukey 702

Popular soldering station Lukey 702 among radio amateurs and electronics engineers. The station's soldering iron is a clone of Japanese HAKKO soldering irons. In general, in other Lukey models the soldering iron is the same as in the 702 (there may be differences in the type of heater, but more on that below). The station has a soldering gun, which makes soldering any components much easier. This is a significant plus. This station also has a soldering iron with 900M series tips. As you can see, this iron has more internals than the SumSour 220 V. 5 wires are connected to the station from the soldering iron. The first two are a thermocouple for controlling and measuring temperature, the other two are a heater. The fifth wire is ground.

Grounding allows you to reduce the risk of damage to the chips on the board by static electricity, which can appear on the soldering iron tip or even on the station itself.

The temperatures of the hair dryer and soldering iron are adjusted using buttons.

There is a soldering gun and a soldering iron that can be used to perform 90% of soldering work and replacing display modules or back covers of smartphones and tablets.

In addition, the hair dryer has replaceable nozzles for different sized jobs. From the soldering gun the following are connected to the station: a thermocouple, a heating element, a turbine, grounding and a reed sensor. The reed sensor responds to a magnet that is installed in the hair dryer stand. Need to put your hair dryer into standby mode? Just place it on the stand with a magnet. The hair dryer will begin to cool down quickly and go into standby mode. And if you need the hairdryer again, you just need to take it from the stand. The hair dryer will begin to heat up to the temperature at which it was placed on the stand. On the other hand, this station has a number of disadvantages that can be problematic for both beginners and experienced electronics engineers. Let's look at the pros and cons of the station.

Pros of 702 station:

• There is a soldering iron with 900M type tips and a hair dryer;
• It is possible to change the nozzles on the hair dryer and the tips on the soldering iron;
• Easy adjustment of temperatures and air flow;
• Thermal stabilization and temperature control;
• Automatic shutdown of the hair dryer (there is a reed switch in the handle of the hair dryer that turns off the hair dryer if you put it on the stand);
• Digital temperature display;
• Fast heating;
• It is possible to calibrate the temperature.

On the one hand, this is a good price-quality station for a small workshop for repairing equipment. But it is outdated and has a number of disadvantages:

• There is no automatic shutdown of the soldering iron;
• Still the same problem with 900M tips;
• High price;
• Without disconnecting from the network, the station can turn on itself;
• Not heat resistant wires.
• Terrible PS/2 connector on the soldering iron;
• A large hair dryer with a lot of vibration in the body due to the turbine.

If desired, you can reflash the Lukey 702 using a programmer, improving the operation of the station.

Disadvantages of 702 station and its improvements

The problem with wires is that they are not heat resistant. You can melt them by mistake or accidentally. Connecting a soldering iron leaves no room for improvement. It is made through a PS/2 connector, which can be found on old computer keyboards and mice. If the mount for the computer is not critical, then for the station everything is in vain. The connector is not fixed by anything, and can often simply fall out when working with a soldering iron.

And the hair dryer cannot be disconnected from the station if it is not needed (and if it breaks, it will be more difficult to replace it with a new one). In other analogue stations there is practically no such defect. So, should we take station Lukey 702? There are two options. Either take 702 and improve it, or take a similar station that will have these shortcomings corrected.

For example, this Eruntop 8586 station has power off buttons (not to be confused with regular power off buttons, which do not disconnect the station from the network). And overall it is much cheaper. Although it does not have a soldering iron temperature indicator.

And in general, the analogues look more compact than the original 702 station itself. From the point of view of circuitry, they are identical (except for the control function for adjusting the air flow. It is digital. Although this is even more convenient.

Or here is an example of a station that is a close analogue of 702.

Therefore, the purchase of station 702 is in question. You will overpay for the brand and popularity of the station, although you can buy exactly the same modified station. And of course, the connectors for connecting a soldering iron and hair dryer to the station may differ.

There are also options with compressor control of the hair dryer. This hair dryer is lighter, it produces less vibration and noise, however, due to the compressor, the station itself is large, and the hair dryer cannot be disconnected from the station. And the compressor at the station is very noisy.

If you still decide to buy a 702, then remember that it must be turned off from the network after use. Or install a plug with an off button. There is a design flaw in the station. Even if you turn off the soldering gun from the front button, and it is on the stand, it may turn on spontaneously due to the failure of the triac. Such cases have already happened. The hairdryer just caught fire. The on and off buttons on the front side of the station do not turn it off from the network. Therefore, the station must be disconnected from the network if you are finished soldering.

An example of modification of the Lukey 702 soldering station:

Problem with 900M series tips

The main problem with these tips is the presence of a large empty space between the heating element and the tip itself. There are several possible solutions.

Reducing the gap

You can move the heating element, fill the gap with sand in empty places, or pick up a small nut on the tip of the heating element.

Or you can even move the heating element closer to the tip. Although these solutions, to put it mildly, are not very good. If you need a different type of tip, you will have to install everything again. By the way, the heating element itself is very fragile. Such modifications can easily damage it.

You can also replace the old nozzle with a new one, which is smaller in size. This will allow you to reduce the distance between the heating element and the tip.

Installation of a ceramic heater

There are two types of heating elements. These are ceramic and nichrome. Ceramic heats up faster and holds the temperature better. But it's more expensive. It’s true that simply replacing a nichrome heating element with a ceramic one will not work. Firstly, they have different temperature sensors. Secondly, you will have to calibrate the station. Well, the final touch is the need to replace the operational amplifiers that amplify the data from the temperature sensor. The sensor values ​​for nichrome and ceramic heaters will be different. For one, the sensor can be made using a thermocouple, and for the other, using a thermistor. This is a significant difference.

In the Lukey 868 station, Japanese ceramic heaters were installed in the soldering irons, and in the Lukey 702, Chinese nichrome ones were installed. They are not compatible without additional changes to the circuits.

Station calibration

Many stations have a calibration function. There is software calibration where you can adjust the station’s custom temperature to the real one. And there is the usual setting using potentiometers. Such potentiometers are installed on boards.

Temperature meters are needed to calibrate the station. Without them, it will not be possible to accurately calibrate the station. Of course, you can set it approximately to the melting temperature of the solder, but this will not be as accurate as checking with another independent temperature measuring device.

Working together with a soldering gun

Using a soldering gun you can stabilize the soldering temperature of the soldering iron. It is enough to simply heat the soldering area with a hairdryer at 100-150 °C with medium air flow. This method allows you to avoid the appearance of large drops of solder on small contacts (especially when soldering any connectors, such as micro usb)

Use of copper tips

Alternatively, you can use copper tips. They heat up faster than non-burnable ones.

You can choose an identical copper tip in shape and size exactly the same as the non-burnable one. Installs exactly the same as fireproof.

Although this option is not ideal. Yes, such tips are in demand, but copper tips lose their shape during operation. Of course, they are not as expensive as fireproof ones, but this is still not a solution. They also need to be tinned constantly before work. And modern stings have long ceased to be consumables. And changing the shape is a very critical parameter, especially if you solder every day. And finding really good copper tips on AliExpress is quite problematic. The problem with the 900M stings has been resolved in the next generation.

What criteria should you pay attention to when choosing a soldering iron?

A soldering iron is a relatively small tool designed for soldering small parts and wires. The scope of its application is quite extensive. If, for example, a person is a car enthusiast, then it will be useful for soldering twists. An electric soldering iron can also be useful for repairing pots. But how to choose a soldering iron?

You must approach the purchase of a device responsibly, having studied the relevant characteristics

When it comes to a tool, you need to have a clear idea of ​​what it is and what it consists of.

The average finger tip consists of a handle, an apron, special holes, a body, a heater, a connecting screw and a tip. Each of these details plays a special role and you need to pay attention to them. Therefore, when it comes time to choose a soldering iron, you need to pay attention to all these details (what it is made of, what functionality, company or country, manufacturer, etc.).

For soldering different materials and their sizes, the corresponding modification of the device is used

In addition, when choosing a soldering iron, you should take into account the purpose for which it is purchased and build on this. But there are a couple of general criteria that you should pay attention to when choosing this tool.

One of the main parameters that plays the most important role during operation is the power and size of the equipment.

For your information. You should not start from the assumption that the larger the soldering iron, the better it is.

If an electric soldering iron is intended for use at home, then it is not advisable to choose its power more than 40 watts. A parameter that is too large will only be reflected on the electric meter, but in fact will heat the air, and not those small parts that are found in home repairs.

People often pay attention to the range of attachments included. It is recommended to purchase a soldering iron with a large number of attachments. This will increase its versatility in operation and improve the functionality of the products being repaired.

The tip size adjustment function will be useful if you often have to “climb” into hard-to-reach places. Over time, the sting becomes smaller. This is due to the fact that when soldering, the working cylinder becomes jagged or becomes smaller. Therefore, the size adjustment function will come in handy. At any time, the ground tip can be made a little larger or, if necessary, reduced to the desired size.

The material with which the nozzles are covered plays an important role. If the steel nozzle is not coated, the solder will stick to it. After the work done, it is very difficult to get rid of it. Therefore, it is simply necessary to pay attention when purchasing to the presence of a protective non-stick coating. Most often, Teflon is used as a coating. It has a shine, so it will immediately catch your eye when you buy it.

Note! The ideal option (however, the most expensive) is an all-copper tip. Although it is softer and wears off faster, it transfers more heat, heats up faster and interacts well with solder materials.

The type of soldering iron should be determined in advance, before purchasing. The result of the work depends on the type of soldering equipment. If you choose incorrectly, you can damage the product. The most popular and effective is the electric soldering iron. It is popular for its versatility and combines the criteria necessary for work.

The most famous option is electric

The material from which the handle is made affects not only the design of the device, but also ease of use. This is one of the most important criteria. It is recommended to purchase soldering irons with a handle that can withstand high temperatures. The most popular material is wood. The wooden model is light and does not deform when the instrument is heated.

Additional Information. It is not recommended to buy an electric soldering iron with plastic handles; they cannot withstand high temperatures and overheat.

The ideal option would be a ceramic look. A handle made of this material is dielectric, does not get wet and will not melt from high temperature, which is typical for other types.

Soldering iron power

The intensity of heating of the surface on which the work occurs depends on the power of the soldering iron. Here, too, a lot depends on the goal. For example, when soldering microcircuits, an electric soldering iron with a power of up to 25 watts is ideal. A parameter exceeding this threshold may harm the electrical microcircuit.

If a soldering iron is needed when soldering thick wires, then it is recommended to purchase a tool with a power of 40 watts or more.

Important! It is not recommended to use a soldering iron with a power less than recommended (for example, when soldering thick wires, you should not use a 25 Watt electric soldering iron when 40 Watt is recommended). The material will not heat up to the required temperature. At best, the soldering will be weak, and at worst, it will not exist at all. Also, if the power exceeds the permissible one, the material will heat up faster than required, and soldering time will take no more than three seconds.

If possible, it is recommended to buy a soldering iron with adjustable power.

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The power regulator, located on the device or nearby, will be a good help in working with different thicknesses of metal.

Temperature control methods

When working with a soldering iron, it is important to monitor the temperature of the tip. If overheated, the soldering may be faulty (internal cavities, not melting, but sticking of solder). There are three ways to regulate the temperature of an electric soldering iron:

• Using a switch is the simplest and most accessible option for adjusting the power of heating equipment. This method involves cyclically switching the current supply, which will lead to a change in temperature from the maximum to the minimum value.
• A simple and practical way is to use a dimmer. There are a number of soldering irons with built-in adjustment. These elements are called dimmers. The device is a device that limits the flow of electricity into the soldering iron. Temperature regulation in the tip occurs due to a voltage drop in the dimmer.
• Using control units is an expensive, but most accurate method of adjusting the heating power of a soldering iron. More complex devices have control systems. We are talking about soldering irons with a power supply. The current source contains a control system. The block does not take up much space; it is located in the handle of the electric soldering iron itself.

The tip is one of the important parts of the entire apparatus

Tip material

One of the important parts of a soldering iron is the tip. This simple metal cylinder is where all the work happens. There are many materials from which tips for an electric soldering iron are made. But it’s better to purchase proven ones, based on reviews from experts and other users.

The most popular one is a copper tip. The most popular material for making soldering iron tips. It is one of the most optimal due to its thermal conductivity and heat capacity. This is a huge plus for those who work with large objects, since the copper tip remains warm for a long time. The tip is also universal. You can solder almost anything with it. But you should work with microcircuits carefully. The main disadvantage is that when exposed to high temperatures, the tip oxidizes. When cleaning it, the size of the tip can decrease quite significantly.

For your information. One of the cheapest options is a rod with tinning of nickel and silver

The tip is made of copper, but is plated with either nickel or silver. This is done in order to protect the tip from rust and burning. The main disadvantage of this version of the tip with nickel is that the solder is very poorly retained on the surface.

Ceramic models are expensive. The tip itself is made of metal, but the body is ceramic. Ceramics conduct and retain heat well. In addition, the heating rod is not afraid of rust, but is prone to cracks when dropped or hit.

There are also composite stings. This option consists of several materials. For example, the tip has a steel core, itself is made of copper, and the coating is made of silver.

Additional Information. For home use, it is best to purchase a soldering iron with replaceable tips.

The correct shape of the tip of the device has the greatest influence during operation

Shape of the tip

Everyone would like to have one universal remedy for everything, but, unfortunately, this does not happen. Each type of soldering must have its own tip. Of course, there is a universal modification called a cone, but when working with it it will not be as convenient and effective as we would like. This is why it is worth buying soldering irons with replaceable tips.

The sting-cone is a universal attachment, which is why it is included with almost all types of equipment. Due to its size, it retains heat perfectly, which cannot but please those who deal with large objects. But for the same reason it can completely ruin fragile work. It has a cone-shaped shape, hence the name of the same name.

For your information. The sting-needle is the most unfortunate and ineffective option, according to experts.

It has a cone-shaped shape, but is slightly smaller and pointed towards the end, resembling a needle tip. Due to its size, it does not retain heat. This leads to the fact that even a small amount of solder will not melt.

Tapered and beveled shapes are most popular due to versatility and practicality.

The wedge tip, due to its design, holds solder perfectly. Just like the cone-shaped version, the size is a huge plus. Due to its shape it has excellent thermal conductivity. Many experts claim that this type of tip is more versatile than is commonly thought.

The bevel sting is rare. This tip has a cylindrical shape with a bevel of 45 degrees. The effectiveness of the sting directly depends on its size. For example, when working with microcircuits, it is recommended to use a smaller tip than the standard one. It copes well with the tasks due to its heat capacity, which is ensured by the shape and flatness on the bevel side.

Microwave sting is rare. In simple terms, it is a more advanced version of the beveled model. The difference is in the cut on the side of the sting. In the case of a microwave tip, there is a depression in the bevel. When using this tip, you won't have to remove excess solder, which is a huge advantage. This advantage is very necessary for professional soldering. It is not necessary to purchase such a tip for home use.

The knife-shaped sting has the shape of a knife. It accumulates and retains heat better than other types, which makes it a favorite. Due to its shape, it accommodates a larger amount of solder compared to other nozzles. Ideal for through-hole installation. Otherwise, problems may arise. Not suitable for soldering small parts.

Equally important is the ease of holding the device.

Soldering iron handle material

The soldering iron handle is also an important component. On the shelves you can most often see electric soldering irons with wooden models. Wood material does not transmit electricity, does not heat up, does not deform under the influence of high temperatures, and does not deteriorate due to pressure changes. The same cannot be said about other materials.

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Plastic is quite popular because it is cheap. This handle becomes deformed after prolonged use. When exposed to high temperatures, the material may melt. This will lead to the replacement of the handle, since it is inconvenient to work on a damaged instrument.

But in the case of glass, everything is simpler. When exposed to high temperatures, glass surfaces release sodium ions, resulting in sufficient conductivity of electricity. In addition, with sudden temperature changes, the glass handle may burst.

For your information. Based on all these facts, we can conclude that wooden handles are the safest.

Gun shaped models are ideal for soldering work

New generation of tips – T12 cartridges

The new generation of stings is structurally different from those presented above. It's not even a sting anymore, it's a cartridge.

It is even incorrect to simply compare the 900M tip and the T12 cartridge.

A single T12 housing contains both a thermocouple and a heating element.

A correct comparison of T12 with 900M blades would be like this. T12 tips do not have such a gap between the tip itself and the heating element. This will allow you to achieve the best contact between the heating element and the tip itself.

There are only 2 wires coming from the cartridge itself. This is both a heater and a temperature sensor. The 900M from Lukey 702 has separate wires for the heating element and temperature sensor.

The tip itself is made of copper inside and covered with an alloy on the outside.

Of course, T12 tips (cartridges) will cost more (especially original ones) than 900M. One cartridge will cost approximately the same as a whole set of different types 900M! But do not forget that the T12 cartridge is both a heating element and a temperature sensor. And all this in one building!

Let's compare different types of tips in one photo: And of course, T12 tips have a wider selection of a wide variety of tips. No 900M tip can achieve exactly the same miniature tip as the T12 and still maintain its performance.

Now let's look at a typical T12 soldering iron.

Externally, it looks like a soldering iron with 900M tips. Of course, the cartridge (tip) changes differently. Simply unscrew the nut and sleeve and you can change the cartridge. To completely disassemble you need to unscrew the base of the handle.

There is nothing inside except the contacts for connecting the T12 cartridge and the switch (vibration sensor).

But where is the grounding? This soldering iron does not have it. Those. The station itself to which this soldering iron is connected is grounded, but the soldering iron itself is not grounded. There are different soldering irons and T12 stations. Somewhere there is a grounding of the soldering iron, and somewhere there is not.

The SW-200D ball switch (vibration sensor) allows you to put the soldering iron into sleep mode.

You stop using the tip, put it on a stand, and the temperature on the tip automatically decreases to room temperature. This is economical, convenient and protects the tip from unnecessary excess heat. And the most important thing is that you can use any stand. This is a ball sensor. It only reacts to prolonged inactivity. The same reed sensor in a soldering gun on a Lukey 702 will turn on only when a magnet approaches, i.e. when you place the hair dryer on the stand with a magnet. And here, while the soldering iron is in operation, it periodically moves, and the ball sensor does not put the soldering iron into sleep mode.

T12 cartridges heat up faster, transfer heat better, and are much better at soldering, unlike the above-mentioned soldering irons. Pins with T12 cartridges have deservedly gained fame as very high quality and the best of their kind among repair shops and radio amateurs.

Finding something better in terms of price and quality is currently simply unrealistic. If there is something better, it is only ten times more expensive.

Among the disadvantages of T12 soldering irons, we can highlight the wear of contacts in the body. Those. Over time, when cartridges are frequently replaced, the contacts may begin to lose contact with each other. To a large extent, everything depends on the type of soldering iron body. There are plastic cases for 500 rubles, and there are metal ones for 2,000.

Now let's look at a soldering station based on T12.

Soldering station Quicko T12-952

One of the best T12 stations.

There is a power off button and a standard network cable connection. There is also a 24 V power supply option instead of mains power. If necessary, the fuse can be changed without disassembling (although it is better to look at the station board for faults if the fuse does blow).

A display with the main menu is installed. Lukey 702 doesn't have nearly as much information about the station. When you press the encoder (temperature regulator) for 2 seconds, a menu of settings and additional functions will appear. You can set the auto-shutdown time of the soldering iron and adjust the temperature. increase the voltage, find out the firmware version, turn off the sound notification, etc. A whole mini PC!

Among the shortcomings of the station, you can cancel the lack of grounding of the soldering iron and the lack of Russian language in the menu and settings.

KSGER T12 FX9501

This is basically the same station, but it has different firmware and a different developer.

You can even select the type of tip used, the time, and even set a password for the station (although why do you need to set a password for the soldering station?).

This station has a soldering iron grounding.

The entire T12 station in one handle

There are T12 stations with a control board directly in the soldering iron handle.

True, for such a soldering iron you will need a 24 V 72 W power source.

T12 DIY KIT

Or you can even assemble the T12 station yourself without a display, only with a temperature indicator. And it will even have an automatic shutdown of the soldering iron thanks to the SW-200D ball vibration sensor. The following KIT DIY kits are sold: And in general, the station will be several times cheaper than ready-made options. True, for the station to work you will need a power supply. In the ready-made versions of T12 Quicko T12-952 and KSGER T12 FX9501, the power supply is already inside the case.

Universal temperature stabilizers

Of course, quality material alone is not enough. It is necessary that the optimum temperature is maintained at the tip of the sting itself. It is for these purposes that a special sensor can be installed in his body. This option is considered optimal in situations where it is necessary to maintain a constant temperature in the soldering zone. These tools are especially important in cases where you need to work with elements that are sensitive to overheating. In this case, the technician can set the tip temperature to a higher temperature than the melting point of the solder.

A specialist can work without fear of damaging parts. In addition, most designs use fairly simple schemes when the temperature is set in advance and does not require constant monitoring. It is also worth considering that the regulator can be installed in a housing or placed in a separate unit. This does not affect the quality of work at all.

Today, there is a certain category of radio amateurs who most prefer their own tools, including tips for soldering irons. Most often, after trying many different options, the master chooses a specific tip or tries to make it himself.

Originally posted 2018-07-04 08:13:06.

T12 competitors

In addition to the T12, soldering irons and stations similar in concept are produced. Some of them are superior to any T12, but their price is several times higher.

TS100

Miniature and powerful soldering iron. The entire control unit is located directly in the soldering iron handle.

Combines the most important advantages of T12. And this soldering iron can be flashed and further configured via USB.

TS80

Even smaller and better TS100. It will be especially useful for those who repair equipment on the road. There is a grounding connection for the soldering iron. The disadvantages include the high price and crude firmware.

Is the TS100 AND TS80 worth buying for beginners? More likely no than yes. The price is several times higher than that of any fully equipped T12 station. In addition, some of its functions are useless for beginners.

And why do you need mobility, fine-tuning and compactness if a beginner is just learning to solder and learning the basics of electronics?

Final Recommendations

So, which soldering iron option is the best choice for the home? It depends on what exactly you plan to solder with it. For microcircuits, small radio components and printed circuit boards, pulsed or spiral devices with a power of up to 30 W are suitable. For soldering wires, large radio components, repairing lamps and most home electrical work, it is more convenient to use different types of electrical rods with an average power of about 60 W. Equipment at the level of 100 W or more will be required to repair metal products. And in general, it is better to buy a good electric rather than a gas model, rod (straight) or pistol design.

A little more about originals and copies

A set of original tips sometimes costs almost as much as a full-fledged station. And this is the price of quality. Few copies can come close to the original in terms of characteristics. However, even the lowest quality copies can be soldered.

Yes, copies of tips and other components for soldering irons will not be equal to the originals.

On the other hand, you can buy the original later, when you learn how to solder copies, which are several times cheaper in price. The money saved can be spent on radio components, screwdrivers, multimeters and other necessary things.

And a copy is not a fake. The fake will repeat everything, right down to the name (Lukey 702 is a copy of HAKKO, but is called and assembled differently).

Selecting a soldering iron tip

Another important element of a soldering iron is the tip. This is the main part, which, in fact, is driven around the work area. When choosing equipment, consider three parameters that describe the tip.

• Material.
  The most common base metal is copper. It conducts heat well, but without an additional protective layer it quickly oxidizes. Powder scale is easy to clean off, but it will have to be done constantly. The problem is solved by a coating made of aluminum or - even better - nickel. Such models practically do not oxidize and are suitable for the smallest jobs.
• Form.
  The tip can be flat or tapered. The second type is now the most common, because it allows for point touches in the most delicate, small works. But for coarser soldering, for example, when repairing a tank or pan, a flat tip is more convenient. You can additionally buy a set of several stings of different sizes and shapes.
• Thickness.
  For most jobs, the optimal thickness of a flat tip or the diameter of a cone-shaped tip is 3 mm. If it is less, the tip will quickly become unusable and simply wear out. If more, it will be too large and inconvenient, especially for small jobs. Thicker tips are needed for repairing large metal items.

Thus, for soldering microcircuits it is better to choose a soldering iron with a nickel-plated tip in the shape of a cone, 3 mm thick. There are also regular and heat-resistant models. Heat-resistant models are better able to withstand high temperatures during long-term continuous operation.

Professional equipment

Professional equipment costs tens of times more than their cheap analogues and copies. At first glance it may seem that this is an unnecessary overpayment of money, but this is not so. In service centers, where the average day of soldering can be 6 or 7 hours in one day, this difference can be quickly noticed. Speed, quality and temperature control are important here. Radio amateurs, in principle, have little need for such equipment. In assembly shops or service centers they can solder as many boards and parts in one day as a radio amateur could not solder in several months. This is not a reproach towards radio amateurs, but rather an explanation that for a hobby, professional equipment at a price of 50,000 and 100,000 rubles will be excessive, and amateur radio practice will not reveal even part of the potential of such equipment (not to mention the payback).

ATTEN ST-862D and Quick 861DW

There is no point in even comparing Lukey 702 with these stations. These stations have a hairdryer power of 1 kW. These stations also have angled attachments for hair dryers, which are convenient to work with under a microscope. A real battle of the titans.

JBC and HAKKO

Soldering stations from this company, as well as from the Japanese HAKKO, do not give a chance to either the Chinese T12 or the Chinese TS. Only the price for them can even reach 600,000 rubles. Thermal tweezers, attachments for any microcircuits, convenient and thoughtful ergonomics and the highest quality. It doesn’t even make much sense to consider them, since beginners don’t even need such stations in theory.

Bottom and top heating

Also, do not forget about the lower and upper heating (IR heating). Without them, it will not be possible to efficiently solder massive BGA chips. And soldering a huge number of identical boards using solder paste using only one hair dryer is quite a task. You can read more about this in the article about soldering.

Thermopro is not cheap equipment, but first you can assemble your own bottom heating using available components.

How much does a soldering iron for microcircuits cost in stores and online?

This type of tool is quite difficult to find on sale. Tips are most often sold for conventional soldering irons, which can also be used to solder microcircuits. But if you want to purchase a separate device for these tasks, then look better and you will see that they are still on sale. The cost of such devices starts from 300 rubles, for very simple devices for home and infrequent use, and can reach about 6-8 thousand rubles for equipment designed for professional use.

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Whether to choose a ready-made soldering iron for microcircuits or to make one yourself is up to everyone to decide for themselves. Sometimes it is enough to change the tip in your existing soldering iron to a thinner one or a more convenient shape. Any job requires its own tool, and the work of dismantling or installing microcircuits requires a special soldering iron, which in skillful hands will ensure high-quality contact of the microcircuit with the board tracks, and cleanliness, beauty and, most importantly, normal operation of the installed device.

Bottom line

There are dozens of types of stations and soldering irons. And in general, for beginners there is an opportunity to quickly learn professional soldering on budget equipment.

What to choose

For beginners, you can buy a regular nichrome soldering iron. You can solder boards with it, desolder parts, and assemble radio sets. Available at any household. store. Learn how to handle such a soldering iron and care for the tip. Enough for 10 hours of practice. You can solder homemade printed circuit boards. And with such a simple nichrome soldering iron, you can start your journey in electronics repair, for example, by resoldering transistors and failed electrolytic capacitors.

Next are two options. Or buy T12 right away, and then buy a hairdryer separately for it, or instead of T12, Lukey 702 (or its equivalent). These two options will cover all your amateur (and even professional) soldering needs. Of course, it’s better to immediately take the T12, since the 702 and its analogues have outdated tips like 900M, which you need to get used to. But the kit includes a soldering gun, with which you can solder microcircuits and change modules on smartphones.

Is it possible to assemble a station or soldering iron with your own hands at home?

The soldering iron itself is unlikely, but the station is quite good, especially the bottom heating.

You can change the firmware, do voice control, whatever. Even modding the station by changing the color of the temperature indicators. But making a homemade hairdryer, soldering iron or tips is already unrealistic. There are ready-made options for any price and need. It’s difficult to make something new, especially if you don’t have a metal processing machine and the necessary workpieces.

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Soldering of massive parts

Finally, we'll briefly talk about soldering parts with high heat capacity, such as cable joints, tanks or cookware. The requirement for the immobility of the joint is most important here; large parts are pre-connected with clamps, small parts with lumps of plasticine; before soldering the joint, it is grabbed pointwise in several places and the clamps are removed.

Massive parts are soldered as usual - first, solder at the joint, then fill the seam with liquid solder. However, special solder is used for these purposes, usually refractory and capable of maintaining high tightness, as well as withstanding partial heating well.

When soldering like this, it is extremely important to keep the parts well heated. For these purposes, the soldering seam is heated with a gas burner immediately before the soldering site, and a massive copper hatchet is used instead of a conventional electric soldering iron. It is also constantly heated in the flame of a burner, simultaneously wetting it with solder, and then the joint is filled, partially melting the previous seam by a few millimeters.

A similar heated soldering technique can also be used when working with a regular soldering iron, for example, when soldering thick cable cores. The sting in this case acts only as an operational tool for carefully distributing the tin, and the main source of heating is a gas burner.

How to solder pipes

Copper pipes are soldered using a high-temperature method with any hard copper solder with activated flux paste, which does not require removal of residues. Next, there are 3 options:

• In copper (brass, bronze) couplings - soldering fittings.
• With full distribution.
• With incomplete distribution and compression.

Soldering copper pipes into fittings is more reliable than others, but requires significant additional costs for couplings. The only case when it is irreplaceable is a drainage device; then a tee fitting is used. Both soldered surfaces are not tinned in advance, but are coated with flux. Then the pipe is inserted into the fitting, securely fixed and the joint is soldered. Soldering is considered complete when the solder stops going into the gap between the pipe and the coupling (0.5-1 mm is needed) and protrudes outward as a small bead. The fastener is removed no earlier than 3-5 minutes after the solder has hardened, when the joint can already be held by hand, otherwise the solder will not gain strength and the joint will eventually leak.

How pipes with full distribution are soldered is shown on the left in Fig. The “distributed” soldering holds the same pressure as the fitting one, but requires additional pressure. special tools for unrolling the socket and increased solder consumption. Fixing the soldered pipe is not necessary; it can be pushed into the socket with a twist until it jams tightly, so soldering with full distribution is often done in places that are inconvenient for installing the clamp.

Soldering copper pipes

In home wiring made from thin-walled pipes of small diameter, where the pressure is already low and its losses are insignificant, soldering with incomplete expansion of one pipe and narrowing of the other may be advisable, pos. I on the right in Fig. To prepare the pipes, a round stick made of hard wood with a conical tip of 10-12 degrees on one side and a truncated-conical hole of 15-20 degrees on the other, pos. II, is sufficient. The ends of the pipes are processed until they fit into each other without jamming for approx. by 10-12 mm. The surfaces are tinned in advance, more flux is applied to the tinned ones and they are connected until they jam. Then they heat until the solder melts and prop up the narrowed pipe until it jams. Solder consumption is minimal.

The most important condition for the reliability of such a joint is that the narrowing must be oriented along the flow of water, pos. III. Bernoulli's school law is a generalization for an ideal fluid in a wide pipe, and for a real fluid in a narrow pipe, due to its (liquid) viscosity, the maximum pressure jump shifts opposite to the current, pos. IV. A component of pressure force arises, pressing the narrowed pipe against the distributor, and the soldering turns out to be very reliable.