How to choose a soldering iron

What a soldering iron is for is clear from its name – for soldering, that is, connecting metal parts using a fusible alloy (solder). But there is no universal soldering iron. It will not work with the same tool to repair the radiator and solder the microcircuit to the board. How to choose the most suitable soldering iron for your tasks – in this article.

The task of the soldering iron is to warm up the solder and the parts to be joined to a temperature at which the solder will remain liquid. It is necessary for the solder to wet the parts in a molten state, otherwise the connection will be fragile. Hence, the basic requirements for a soldering iron follow – the size of the tip and the power of the soldering iron must correspond to the material and size of the parts to be soldered. The rest of the characteristics of soldering irons rather affect the usability of the tool in various conditions.

Soldering iron specifications
Appointment

Soldering irons for burning, strictly speaking, are not soldering irons. Most burners are unsuitable for soldering – a thin arc tip is not wetted with solders and cools quickly in contact with metal parts.

 

There are universal soldering irons with interchangeable tips and temperature control. At high (300-700 ° C) temperatures with a thin tip installed, they can be used to burn patterns on wood or leather, and at low temperatures (200-300 ° C) – for soldering electronic components.

For conventional soldering irons, the optimum temperature range is 250-350 ° C, they are intended only for soldering.

Power

The larger and more massive the parts, the larger the tip of the soldering iron should be and the more powerful it should be. And when soldering small parts, excess power can damage, leading to overheating of the parts and damage to them. Therefore, the power of the soldering iron is selected based on the type of parts to be soldered:

5-25 W are optimal for soldering electronic components on printed circuit boards and connecting thin low-voltage wires with a cross section of up to 0.1-0.2 mm 2 or less;
25-45 W are suitable for soldering power electronic components with large (from 0.5 mm 2 ) leads and connecting electrical wires with a cross section of 0.2-1 mm 2 ;
60-100 W – a soldering iron with this power is convenient to use for connecting wires of household electrical wiring for various purposes with a cross section from 1 to 10 mm 2 ;
100-200 W will be required for soldering high-voltage wires of large cross-section and for connecting wires with current-carrying buses;
200-500 W is the power of soldering irons used for soldering large parts when repairing radiators, metal containers and utensils.
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Most soldering irons have a 220 V electrical network .

There are also miniature models powered by the USB connector. They are compact, lightweight and safe. If you accidentally burn the power cord with a red-hot sting, there is no longer any risk of electric shock.

Where there are no outlets, alternative types of power supply can be used: batteries and gas. Cordless soldering irons are convenient, but their power is usually low: 6-8 W, they are suitable only for soldering miniature parts and thin wires. In addition, the stock of accumulators or batteries “charged” into the handle of the soldering iron is enough for 10-15 minutes of operation, no more.

Gas soldering irons can have a higher power and (in the presence of gas cartridges for refueling), the duration of their operation is practically unlimited. But you need to get used to working with a gas soldering iron. Hot air and sometimes open fire are emitted from the nozzles of the gas soldering iron burner. If the installation takes place in a cramped environment, it will be difficult to work with it.

Maximum heating temperature

It affects the ability of the soldering iron to work with various solders. The temperature of the tip should be 60-100 ° C higher than the melting point of the solder. At a higher temperature, the solder will be covered with a film of oxides, which prevents a good connection of the parts.

up to 250 ° C, the soldering iron tip heats up when soldering electronic components sensitive to overheating using the Rose alloy (POSV-50 solder, melting temperature 90-94 ° C);
250-350 ° С – the optimal maximum temperature for soldering most of the electronic components with the most popular POS-60 and POS-61 solders (melting temperature 190 ° С);

There are already a lot of 350-450 ° C for soldering electronic components, this temperature is used for repairing radiators, dishes and parts made of galvanized iron with pure tin, POS-30, POS-30, POS-90 solders (melting temperature 220-265 ° C);
450-600 ° C are used for brazing aluminum with refractory solders such as VPT-4, VPT-3, PA-2 and others (melting temperature – 400-530 ° C);
temperatures above 600 ° C are rarely used – for brass, bronze and copper-nickel alloys brazing with refractory solders with a melting temperature of 600 ° C.
On soldering irons with heating temperature control ( power control ), you can set a certain temperature, above which the tip will not heat up. This is especially important when working with miniature components of modern printed circuit boards: due to their small size, they quickly overheat and can fail. And in general, temperature control expands the capabilities of the soldering iron.

But keep in mind that the temperature on soldering irons is pretty rough. For finer tuning, it is better to use a soldering station . In addition to the ability to accurately set the temperature, soldering stations can have many other useful options: indication of the current temperature, built-in hair dryer, board heater, etc. For soldering microelectronics at a professional level, you should focus on soldering stations.

The warm-up time determines how many seconds after turning on the soldering iron tip heats up to the set temperature. The smaller this parameter, the better – a high heating rate not only saves time, but also ensures that the temperature of the tip will quickly recover from contact with cold parts.

Heating element type

The gas heater is used on gas soldering irons – the tip is heated by the burning gas.

 

Nichrome spiral is used in classic electric soldering irons . When current passes through a wire wound on a sting, it heats up, transferring heat to the sting.

The ceramic heating element is a ceramic tube containing a film heater. This design provides a minimum of heat loss, so this soldering iron heats up faster.

But soldering irons with a ceramic heater are afraid of shocks and falls – the element can break, while the heater located in the thickness of the ceramic breaks and stops working.

The pulsed heating element does not operate continuously, but pulses – usually when a button is pressed. There are two types of soldering irons with a pulse heater:

Actually, they are pulsed, the sting of which is an arc made of wire, which heats up under the influence of the current passing through it. Such soldering irons are quite safe (the tip is hot only during soldering) and convenient, due to the very fast heating of the tip (2-3 s), but they are poorly suited for soldering microcircuits.
The tip temperature is not adjustable and can be high for soldering thin joints. In addition, the tip itself is energized, which can damage low-voltage microelectronics.
Soldering irons with a spiral heater, capable of briefly increasing the power of the heating element by pressing a button on the body. Such a soldering iron will be convenient when soldering small “delicate” parts. In high power mode, you can quickly melt a large drop of solder, and the low temperature of normal mode will protect parts from overheating.
Just do not take the indicated maximum power of such soldering irons seriously. With a rated power of 30-130 W, it will work at 130 watts for a few seconds, after which it will take several minutes of “rest”, and it is unsuitable for soldering large parts.
The shape of the tip affects the convenience of performing certain types of soldering work.

The tip of the “cone” type is convenient for through mounting (and dismantling), but it does not hold the solder well, therefore it is less suitable for surface mounting. It is almost impossible to collect excess solder with such a sting. In addition, the low heat capacity (especially in highly pointed “cones”) and a small contact spot make it difficult to warm up large contacts and drops of solder.

A wedge tip is more versatile – it has a high heat capacity, touching with a wide edge allows you to warm up large areas, and when rotated by 90 °, the contact patch is greatly reduced and allows you to work with microcircuit leads and thin tracks of high-density printed circuit boards.

 

In addition to these forms of tips, which are considered the most common, there are many specialized ones – “microwave” designed for soldering SMD components, knives of various shapes for cutting plastic, curly tips for decorative work, etc.

The ability to change the tip increases the versatility of the soldering iron, allowing you to choose the most suitable for a specific situation. In addition, the stings fade over time and their replacement becomes a necessity.

Applications of the soldering iron
A 25-50 W soldering iron with a wedge-shaped tip will be useful in the “arsenal” of any craftsman. They can repair the wiring and solder the burned out part.

 

Soldering microcircuits and electronic components to printed circuit boards requires a soldering iron with a fine tip and temperature control .

A battery powered soldering iron and gas soldering iron can help with repairs in a power outage. For “delicate” work, a more versatile option would be a set of a soldering iron powered by USB and a power bank .