home Plot

How to make a soldering iron with your own hands. Homemade soldering iron: diagram. Do-it-yourself soldering iron at home in different ways First, let’s look at how a soldering iron works

Many home craftsmen have already thoroughly studied how to make a soldering iron with their own hands and how to use it correctly. There are many options for making tools; you can even use improvised means to assemble them. The main thing is to know how the device works and understand what it is needed for.

The most difficult to manufacture at home is a miniature and low-power 12-volt soldering iron. However, you can make it with your own hands, but you need to have the appropriate skills and abilities.

Areas of use

Before you learn how to make a mini soldering iron, you need to understand what is it for. Such a device for home needs will never be superfluous. Using a homemade 12 volt soldering iron you can do the following:

Solder microcircuits of various home appliances.
Repair parts of micro-earphones.
Repair electronic watches.
Repair phone chargers and more.

Such a device is manufactured with the expectation that it will be powered not directly from the network, but through a 220/12 volt transformer.

What do you need for work?

Most materials and tools will not need to be purchased additionally, since home craftsmen will most likely have them at home. Working materials include:

If copper foil is not at hand, it can be replaced with foiled fiberglass laminate, which is often used in the production of printed circuit boards or circuits. But if they are not available, then you can buy everything in a specialized store for an average of 200 rubles. And to get another sheet of foil, heat the fiberglass laminate with a simple iron and pull it around the corner, first dividing it into thin plates, and wrap it around a round stick.

The key element of the design is a 220 to 12 volt transformer, through which the device will receive the necessary energy from the mains. Sometimes a device of the TVK-11OL brand is used, which can be pulled out of an old tube TV.

Required tools include:

pliers;
wire cutters;
tweezers;
rags;
stove (gas or electric);
plates or boards for washing with glue.

The process of assembling a mini soldering iron

Copper wire will act as a tip for a mini soldering iron. You only need 50 mm of it. Sharpen it into a dihedral angle on one side and tin the edges. This tip will be located inside the heating element.

Then make a special electrical insulating mass:

Mix talc and liquid glass (or silicate glue) together.
To prevent the mass from sticking to your hands, apply the insulation to the cylindrical surface with tweezers and sprinkle it with talcum powder.

Roll the foil into a tube about 35 mm long, which will serve as the base for the heating element. On one side, the soldering iron tip will be visible from under it. Cover the tube with insulating paste. Dry the wet applied mixture over the stove until it hardens completely. Then wind a spiral nichrome wire no more than 350 mm long onto the finished base. The turns should be laid carefully as close as possible to each other, and the upper and lower turns from 30 to 60 mm should be left as leads. Then cover the structure again with the electrical insulating mixture and dry it over the stove.

Bend the folded end of the wire back and press it firmly against the surface of the tube, then apply the mixture again. And only after this can the heating element of the structure be used.

Wire protruding from under the heating element need to be covered with electrical insulating mass. Don’t forget to check the quality of your work every time you use it.

When the base is completely covered with insulation, you can assemble the mini-soldering iron itself. The ends of the nichrome heater are connected to the handle; for this purpose, an electrical cord in heat-resistant insulation is pulled through the internal plastic cavity. Be sure to insulate and dry the exposed areas and place a tin protective casing on the heater and connect it to the handle. After this, the device is ready for use.

Homemade soldering iron from a resistor

To produce various instruments at home, amateurs often use all sorts of improvised means. A soldering iron based on a resistor is easy to use, reliable and simple.

As in the previous case, you will need copper and steel wire, as well as double-sided PCB. In addition to the previously listed elements, you will need a ballpoint pen for the case and a special resistor with a resistance of 5 to 10 ohms.

The algorithm of actions is as follows:

Then start assembling the structure. Place the current conductor from the spring onto the front cup and solder the current conductors to the textolite board. Install the tip by first covering it with ceramics or mica so that there is no access to current. Then solder the wires to the board. It is recommended to use a regulated device for the battery.

As for the features of using homemade mini-soldering irons, their application is no different from factory models. The only thing is that you can save your money. Thanks to such devices, you can do even miniature household soldering work yourself.

And today it’s time for a low-voltage review. According to the manufacturer's instruction manual S-Line, mini electric soldering iron ZD-20A with a supply voltage of 12 volts and a power of 8 watts, it is intended for assembly soldering of electronic equipment elements with tin-lead solders. AC voltage should be used for power supply. Protection class is second, working temperature of the soldering tip is 250-400 degrees, warm-up time is 3-5 minutes. To avoid overheating, it is recommended to turn it off for 15-20 minutes every 3-4 hours of operation to cool down. And finally, in order to avoid death, any repairs should be carried out in a specialized workshop.

I've been looking at this soldering iron for a long time. Last year, while assembling the power supply, I found a place on the front panel to install an RCA connector, a simple “tulip”, to connect it. And so, last weekend, deciding that the “bride” had gone on for too long, I went and bought it. Paid 140 rubles. I’ll say right away that the packaging with the soldering iron is nice - it’s nice to pick it up. The internal contents include the soldering iron itself and the instruction manual. There is only one instruction for the entire range of soldering irons produced by the company. The soldering iron has a length of 156 mm, the largest diameter is 16 mm, the tip length is 12 mm, the diameter is 0.5 mm. The plastic handle, where the fingers grip it, is additionally covered with a casing made of low thermal conductivity material. The power supply cable consists of two independent wires in a common polyvinyl chloride sheath. It is convenient to hold the soldering iron in your hand between the thumb and forefinger, supported from below by the middle finger, like a fountain pen. It weighs like a helium fountain pen.

The resistance of the heating element spiral that interested me turned out to be 104 Ohms.

After connecting to the power supply and setting the voltage to 12 volts, a more interesting parameter became known - current consumption, which amounted to 480 mA. Now you can find out the true power of this particular soldering iron:

P = U x I, P = 12 V x 0.48 A = 5.76 W

Now it will not be superfluous to find out how many degrees in general and in how many minutes the soldering iron tip can heat up.

Within three minutes, the tip was heated quite intensively and easily reached 240 degrees.

AC voltage recommended
for soldering smd the components of this will be quite enough, I will even say that more is not needed
if necessary, it is worth slightly raising the supply voltage, there will be 270 and 300 degrees.

I installed a plug on the soldering iron wires and tried to “get to know” the heating element. The simple (double “bite” with wire cutters) fastening of the heating element inside the casing was definitely disappointing. Further autopsy did not continue. The only identified drawback is the method of attaching the heating element, which will make it difficult to disassemble the soldering iron if it needs to be repaired or modified.

The soldering iron took its place. There is a handkerchief sealed with a standard-sized soldering iron, but it was not possible to do it carefully then, so I took it out and tested the operation of a mini soldering iron on it.

Video

The script of the “movie” is simple, the main thing here is different: it is immediately clear that this soldering iron is in the right place, the tip of the tip will “crawl” everywhere, it will not obscure the view of the component, will not overheat it, and will not move it from its place. In the attached archive, instructions for soldering irons of the ZD / TLW, WD series. In general, I’m happy with the purchase, I even got the mood to solder the shown board of the Eldorado metal detector. Previously I wanted to make a low-voltage soldering iron myself, but I did the right thing by buying it and I wish you the same, Babay.

Soldering iron 12 Volt is a low-voltage soldering iron, the heating element of which is designed for an operating voltage of 12 volts. A 12 Volt soldering iron is used to connect wires and parts of various kinds to each other using the soldering method.

The undoubted advantage of a 12 Volt low-voltage soldering iron, compared to a 220 V household soldering iron, is its low operating voltage and, therefore, known safety when performing work.
A 12 Volt soldering iron is widely used, for example, in radio engineering, when soldering radio elements to printed circuit boards. Its use here prevents damage to current-sensitive radio components and radio components. It is also convenient to use a 12 Volt soldering iron in a car, for example, when soldering wires, since in normal condition, the car’s battery is charged at about 12.6 Volts. In order to use a 12 Volt soldering iron directly in a car, you need an adapter, or adapter, which is usually inserted into the cigarette lighter. Special automotive soldering irons are used precisely for these purposes.

Features of soldering irons 30 W Rexant

Today, the main elements of the soldering iron are being modernized in order to improve their performance characteristics. Ceramic rods are increasingly being used instead of copper rods. This allows you to speed up the heating process of the device tip. There are other types of soldering tools: induction soldering iron and soldering iron with pulsed voltage supply, which differ in the method of heat transfer.

Soldering iron 12 Volt buy Today it is not difficult, there is a wide selection of these tools on store shelves and online stores. Anyone can choose an instrument to suit their taste. For example, a 12-volt Rexant soldering iron or soldering station includes a main unit that allows you to adjust the heating temperature of the tip, and the electric soldering iron itself is designed for a power of 8 W.

And in conclusion, it should be recalled that during the soldering of parts, solder smoke is released. This smoke contains lead and rosin vapors, which have an adverse effect on the human body. Prolonged inhalation of such smoke can lead to allergic and asthmatic reactions, or the so-called “soldering” disease. It is necessary to strictly observe sanitary standards and rules and ventilate rooms in which harmful vapors of solder and flux accumulate as often as possible. It is also not recommended to continuously solder for a long time.

Home (and not only) craftsmen are encouraged to assemble a soldering iron with their own hands, first of all, by economic considerations. It is, of course, better to buy a simple 220 V soldering iron for ordinary small soldering work. However, it is also possible to modify it without disassembling it in order to extend the life of the tip. But a 150-200 W “axe”, which can be used to solder metal water pipes, costs not 4.25, but ten times more. And not Soviet rubles, but evergreen conventional units. The same problem arises if you need to solder outside the reach of the power supply from a 12 V car or a pocket lithium-ion battery. How to make a soldering iron yourself for such cases, and not only such, is discussed in today’s publication.

What is smd

Sub Micro Devices, subminiature devices. You can clearly see the SMD by opening your mobile phone, smartphone, tablet or computer. Using SMD technology, tiny (perhaps smaller than the cut of a match) components without wire leads are mounted by soldering onto contact pads, called polygons in SMD terminology. The polygon may have a thermal barrier that prevents heat from spreading along the traces of the printed circuit board. The danger here is not only and not so much in the possibility of the tracks peeling off - the heat may cause the piston connecting the mounting layers to break, which will render the device completely unusable.

A soldering iron for SMD should not only be micro-power, up to 10 W. The heat reserve in its tip should not exceed that which the soldered part can withstand. But long-term soldering with a soldering iron that is too cold is even more dangerous: the solder still doesn’t melt, but the part heats up. And the soldering mode is significantly affected by the outside temperature, and the more, the lower the power of the soldering iron. Therefore, soldering irons for SMD are made either with a limitation of time and/or amount of heat transfer during soldering, or with operational adjustment of the temperature of the tip during the current technological operation. Moreover, you need to keep it 30-40 degrees above the melting temperature of the solder with an accuracy of literally 5-10 degrees; this is the so-called permissible temperature hysteresis of the tip. This is greatly hampered by the thermal inertia of the soldering iron itself, and the main task in designing one is to achieve the lowest heat time constant possible, see below.

It is possible to make a soldering iron at home for any of these purposes. Incl. and powerful for soldering steel or copper water pipes, and a fairly accurate mini for SMD.

Note: Actually, in a soldering iron, the tip is the working (tinned) part of its rod. But, since there are other different rods, for clarity, we will consider the entire rod to be a sting. If the working part of the soldering iron is mounted on a rod, it is called a tip. Let us assume that the tip with the rod is also a sting.

Simplest

Let's not get into the complications for now. Let's say we need a regular 220V soldering iron without any fuss. We go to choose and see that the difference in prices reaches 10 times or more. Let's figure out why. First: heater, nichrome or ceramic. The latter (not “alternative”!) is practically eternal, but if the soldering iron is dropped on a hard floor, it can break. The tip of ceramic soldering irons is necessarily non-replaceable, which means you need to buy a new one. And a nichrome heater, if the soldering iron is not forgotten to be turned on at night, lasts more than 10 years; with occasional use - over 20. And in extreme cases, it can be rewound.

The difference in price has now been reduced to 3-4 times, what else is the matter? In a sting. Nickel-plated copper with special additives is poorly dissolved by solder and burns very slowly in the soldering iron holder, but is expensive. Brass or bronze heats up worse, and it is impossible to solder SMD with it - the temperature hysteresis cannot be brought back to normal due to the thermal conductivity of the material being much worse than that of copper. The red copper tip is eaten by solder and swells quite quickly from copper oxide, but it is cheaper.

Note: a tip made of electrical copper (a piece of winding wire) is unsuitable for a conventional soldering iron - it quickly dissolves and burns. However, for SMD such a sting is just right, its thermal conductivity is the highest possible, and thermal inertia and hysteresis are minimal. True, you will have to change it often, but the sting is about the size of a match or less.

Burning and swelling of the red copper tip can be dealt with simply by being careful: after finishing the work and allowing the soldering iron to cool, take out the tip, peel off the oxide, tapping it on the edge of the table, and blow out the channel of the soldering iron holder. Solder dissolution is worse: sharpening the tip is often inconvenient and it quickly wears out.

You can make a soldering iron tip from ordinary red copper many times more resistant to the action of molten solder by not sharpening its working end, but by forging it to the desired shape. Cold copper can be forged perfectly with an ordinary metalworker's hammer on the anvil of a bench vise. The author of this article has had a forged tip in the ancient Soviet EPSN-25 for more than 20 years, although this soldering iron is in use, if not every day, then certainly every week.

Simple from resistor

Calculation

The simplest soldering iron can be made from a wire resistor; this is a ready-made nichrome heater. It is also easy to calculate: when the rated power is dissipated in free space, the wirewound resistors heat up to 210-250 degrees. With a heat sink in the form of a sting, the “wireworm” maintains a long-term power overload of 1.5-2 times; The temperature of the tip will not be lower than 300 degrees. It can be increased to 400, giving a power overload of 2.5-3 times, but then after 1-1.5 hours of operation the soldering iron will need to be allowed to cool.

Calculate the required resistor resistance using the formula: R = (U^2)/(kP), where:

R – required resistance;

U – operating voltage;

P – required power;

k – the above power overload factor.

For example, you need a 220 V 100 W soldering iron for soldering copper pipes. The heat transfer is large, so we take k = 3. 220^2 = 48400. kP = 3*100 = 300. R = 48400/300 = 161.3... Ohm. We take a 100 W resistor 150 or 180 Ohm, because There are no “wireworms” at 160 Ohms, this rating is from the range of 5% tolerance, and “wireworms” are no more accurate than 10%.

The opposite case: there is a resistor with a power p, what power can you make a soldering iron from it? What voltage should it be powered from? Let's remember: P = U^2/R. Let's take P = 2 p. U^2 = PR. We take the square root of this value and get the operating voltage. For example, there is a 15 W 10 Ohm resistor. The power of the soldering iron is up to 30 W. We take the square root of 300 (30 W * 10 Ohm), we get 17 V. From 12 V, such a soldering iron will develop 14.4 W, you can solder small things with low-melting solder. From 24 V. From 24 V – 57.6 W. The power overload is almost 6 times, but occasionally and for a short time it is possible to solder something large with this soldering iron.

Manufacturing

How to make a soldering iron from a resistor is shown in Fig. higher:

We select a suitable resistor (item 1, see also below).
We prepare the parts of the tip and fasteners for it. Use a file to select a groove on the rod for the ring spring. Threaded blind holes are made for the bolt (screw) and the tip, pos. 2.
We assemble the rod with the tip into the tip, pos. 3.
We fix the tip in the resistor-heater with a bolt (screw) with a wide washer, pos. 4.
We attach the heater with the tip to a suitable handle in any convenient way, pos. 5-7. One condition: the heat resistance of the handle is not lower than 140 degrees; the resistor terminals can heat up to this temperature.

Subtleties and nuances

The soldering iron described above made from 5-20 W resistors was made by many (including the author in his pioneer days) and, having tried it, they were convinced that it could not be used seriously. It takes an unbearably long time to heat up, and it only solders small things with a poke - the ceramic layer interferes with the heat transfer from the nichrome spiral to the tip. This is why the heaters of factory soldering irons are wound on mica mandrels - the thermal conductivity of mica is orders of magnitude higher. Unfortunately, it is impossible to roll mica into a tube at home, and rolling 0.02-0.2 mm nichrome is not for everyone either.

But with soldering irons from 100 W (resistors from 35-50 W) the matter is different. The ceramic thermal barrier in them is relatively thinner, on the left in the figure, and the heat reserve in the massive tip is an order of magnitude greater, because its volume grows by the cube of its dimensions. It is quite possible to qualitatively solder a joint of 1/2″ 200 W copper pipes with a resistor soldering iron. Especially if the tip is not prefabricated, but one-piece forged.

Note: wirewound resistors are available for dissipation power up to 160 W.

Only for the soldering iron you need to look for resistors of old types PE or PEV (in the center in the figure, still in production). Their insulation is vitrified and can withstand repeated heating to light red without losing its properties, only darkening as it cools. The ceramic inside is clean. But the resistors C5-35V (on the right in the figure) are painted, and so are the insides. It is completely impossible to remove paint from the channel - ceramics are porous. When heated, the paint becomes charred and the tip sticks tightly.

Soldering iron regulator

The example with a low-voltage soldering iron made from a resistor is given above for good reason. A PE (PEV) resistor from trash or from an iron market most often turns out to be of an inappropriate rating for the current voltage. In this case, you need to make a power regulator for the soldering iron. Nowadays it is much easier even for people who have the vaguest idea about electronics. The ideal option is to buy from the Chinese (well, Ali Express, otherwise) a ready-made universal voltage and current regulator TC43200, see fig. on right; it's inexpensive. Allowable input voltage 5-36 V; output - 3-27 V at a current of up to 5 A. Voltage and current are set separately. Therefore, you can not only set the desired voltage, but also regulate the power of the soldering iron. There is, for example, a 12 V 60 W tool, but now you need 25 W. We set the current to 2.1 A, 25.2 W will go to the soldering iron and not a milliwatt more.

Note: for use with a soldering iron, it is better to replace the standard TC43200 multi-turn regulators with conventional potentiometers with graduated scales.

Pulse

Many people prefer pulse soldering irons: they are better suited for microcircuits and other small electronics (except SMD, but see below). In standby mode, the tip of a pulse soldering iron is either cold or slightly warmed up. Solder by pressing the start button. In this case, the tip quickly, within a fraction of a second, heats up to operating temperature. It is very convenient to control the soldering: the solder has spread, the flux has been squeezed out of a drop, the button has been released, and the tip has cooled just as quickly. You just need to have time to remove it so that it doesn’t get soldered there. With some experience, the danger of burning a component is minimal.

Types and schemes

Pulsed heating of a soldering iron tip is possible in several ways, depending on the type of work and the requirements for workplace ergonomics. In amateur conditions, or for a small individual entrepreneur, a pulse soldering iron will be more convenient and affordable to make one of the traces. schemes:

With a current-carrying tip under industrial frequency current;
With an isolated tip and forced heating;
With a current-carrying tip under high frequency current.

Electrical circuit diagrams of pulsed soldering irons of the indicated types are shown in Fig.: pos. 1 – with a current-carrying tip of industrial frequency; pos. 2 – with forced heating of the insulated tip; pos. 3 and 4 – with a high-frequency current-carrying tip. Next, we will analyze their features, advantages, disadvantages and methods of implementation at home.

50/60 Hz

The circuit of a pulsed soldering iron with a tip under industrial frequency current is the simplest, but this is not its only advantage, and not the main thing. The potential on the tip of such a soldering iron does not exceed a fraction of a volt, so it is safe for the most delicate microcircuits. Until the induction soldering irons of the METCAL system appeared (see below), a significant part of installers in electronics production worked with industrial-frequency pulsers. Disadvantages - bulkiness, significant weight and, as a result, poor ergonomics: shifts last longer than 4 hours. workers got tired and started making mistakes. But there are still a lot of industrial-frequency pulsed soldering irons in amateur use: Zubr, Sigma, Svetozar, etc.

The device of a 50/60 Hz pulse soldering iron is shown in pos. 1 and 2 fig. Apparently, for the sake of saving on production costs, manufacturers most often use transformers on type P cores (magnetic cores) (item 2), but this is far from the optimal option: in order for a soldering iron to solder like EPCN-25, the transformer power needs 60-65 W. Due to the large stray field, the P-core transformer gets very hot in short-circuit mode, and the heating time of the tip reaches 2-4 s.

If the P-core is replaced with an SL from 40 W with a secondary winding made of a copper busbar (items 3 and 4), then the soldering iron can withstand hour-long work with an intensity of 7-8 solderings per minute without unacceptable overheating. To operate in periodic short-term short-circuit mode, the number of turns of the primary winding is increased by 10-15% compared to the calculated one. This design is also advantageous in that the tip (copper wire with a diameter of 1.2-2 mm) can be attached directly to the terminals of the secondary winding (item 5). Since its voltage is a fraction of a volt, this further increases the efficiency of the soldering iron and extends its operating time before overheating.

With forced heating

The circuit diagram of a soldering iron with forced heating does not require any special explanation. In standby mode, the heater operates at a quarter of the rated power, and when you press start, the energy accumulated in the capacitor bank is released into it. By disconnecting/connecting containers to the battery, you can quite roughly, but within acceptable limits, dose the amount of heat generated by the tip. The advantage is the complete absence of induced potential on the tip if it is grounded. Disadvantage: using commercially available capacitors, the circuit can only be implemented for resistor mini-soldering irons, see below. It is used mainly for occasional work on hybrid assembly boards that are not saturated with components, smd + conventional printed circuit boards in through-hole pins.

At high frequency

Pulse soldering irons at high or high frequencies (tens or hundreds of kHz) are very economical: the thermal power at the tip is almost equal to the nameplate electrical power of the inverter (see below). They are also compact and lightweight, and their inverters are suitable for powering constant-heat resistor mini-soldering irons with an insulated tip, see below. Heating the tip to operating temperature in a fraction of a second. Any thyristor voltage regulator 220 V can be used as a power regulator without modifications. They can be powered with a constant voltage of 220 V.

Note: for power over approx. A 50 W HF pulse soldering iron is not worth making. Although, for example Computer power supply units can have a power of up to 350 W or more, but it is almost impossible to make a tip for such power - either it will not warm up to operating temperature, or it will melt on its own.

A serious drawback is that the operating frequencies are affected by the influence of the tip’s own inductance and the secondary winding. Because of this, an induced potential of over 50 V may appear on the tip for a time of more than 1 ms, which is dangerous for CMOS components (CMOS). Another significant drawback is that the operator is exposed to a flow of electromagnetic field (EMF) power. You can work with a pulsed HF soldering iron with a power of 25-50 W for no more than an hour a day, and up to 25 W for no more than 4 hours, but no more than 1.5 hours at a time.

The simplest way of circuit implementation of a 25-30 W pulsed HF soldering iron inverter for ordinary soldering work is based on a 12-volt halogen lamp network adapter, see item. 3 fig. with diagrams. The transformer can be wound on a core of 2 K24x12x6 ferrite rings folded together with a magnetic permeability μ of at least 2000, or on an W-shaped magnetic core made of the same ferrite with a cross-section of at least 0.7 square meters. see Winding 1 - 250-260 turns of enameled wire with a diameter of 0.35-0.5 mm, windings 2 and 3 - 5-6 turns of the same wire. Winding 4 - 2 turns in parallel of wire with a diameter of 2 mm (on a ring) or braid from a television coaxial cable (pos. 3a), also paralleled.

Note: if the soldering iron is more than 15 W, then it is better to replace the MJE13003 transistors with MJE130nn, where nn>03, and put them on radiators with an area of 20 square meters or more. cm.

An inverter option for a soldering iron up to 16 W can be made on the basis of a pulse starting device (IPU) for an LDS or the filling of a burnt-out energy-saving light bulb, respectively. power (do not hit the flask, there is mercury vapor!) The modification is illustrated by pos. 4 in Fig. with diagrams. What is highlighted in green may be different in the IPU of different models, but we don’t care about it. We need to remove the starting elements of the lamp (highlighted in red in position 4a) and short-circuit points AA. We get a diagram of the poses. 4b. In it, a transformer is connected in parallel to the phase-shifting inductor L5 on one of the same rings as in the previous one. case or on W-shaped ferrite from 0.5 sq. cm (pos. 4c). Primary winding - 120 turns of wire with a diameter of 0.4-0.7; secondary – 2 turns of wire D>2 mm. The tip (pos. 4g) is made of the same wire. The finished device is compact (item 4d) and can be placed in a convenient case.

Mini and micro on resistors

A soldering iron with a heating element based on an MLT metal film resistor is structurally similar to a soldering iron made from a wire resistor, but is designed for a power of up to 10-12 W. The resistor operates with a power overload of 6-12 times, because, firstly, the heat dissipation through the relatively thick (but absolutely thinner) tip is greater. Secondly, MLT resistors are physically several times smaller than PE and PEV. The ratio of their surface to volume resp. increases and heat transfer to the environment increases relatively. Therefore, soldering irons with MLT resistors are made only in mini and micro versions: when you try to increase the power, the small resistor burns out. Although MLTs for special applications are produced with a power of up to 10 W, it is realistic to make on your own only a soldering iron on the MLT-2 for small discrete components (placers) and small microcircuits, see for example. video below:

Video: micro soldering iron using resistors

Note: the MLT resistor chain can also be used as a heater for a stand-alone cordless soldering iron for ordinary soldering work, see next. video clip:

Video: Cordless mini soldering iron

It is much more interesting to make a mini soldering iron from an MLT-0.5 resistor for smd. The ceramic tube - MLT-0.5 body - is very thin and almost does not interfere with heat transfer to the tip, but will not allow a thermal impulse to pass through at the moment it touches the landfill, which is why SMD components often burn out. Having selected a tip (which requires quite a lot of experience), you can solder SMD with such a soldering iron slowly, continuously monitoring the process through a microscope.

The manufacturing process of such a soldering iron is shown in Fig. Power – 6 W. Heating is either continuous from the inverter described above, or (better) with forced heating with direct current from a 12 V power supply.

Note: how to make an improved version of such a soldering iron with a wider range of applications is described in detail here - oldoctober.com/ru/soldering_iron/

induction

The induction soldering iron is currently the pinnacle of technical achievements in the field of metal soldering with eutectic solders. In essence, an induction-heated soldering iron is a miniature induction furnace: the HF EMF of the inductor coil is absorbed by the metal of the tip, which is heated by Foucault eddy currents. Making an induction soldering iron with your own hands is not so difficult if you have a source of HF currents at your disposal, for example. computer switching power supply, see e.g. plot

Video: induction soldering iron

However, the quality and economic indicators of induction soldering irons for conventional soldering work are low, which cannot be said about their harmful effects on health. In fact, their only advantage is that the tip stuck to the holder in the body can be torn out without fear of tearing the heater.

Induction mini-soldering irons of the METCAL system are of much greater interest. Their introduction in electronics production made it possible to reduce the percentage of defects due to installer errors by 10,000 times (!) and lengthen the work shift to a normal one, and the workers left after it cheerful and capable in all other respects.

The structure of a METCAL type soldering iron is shown at the top left in Fig. The highlight is the ferronickel coating of the tip. The soldering iron is powered by RF at a precisely maintained frequency of 470 kHz. The thickness of the coating was chosen such that at a given frequency, due to the surface effect (skin effect), Foucault currents were concentrated only in the coating, which gets very hot and transfers heat to the tip. The tip itself turns out to be shielded from EMF and induced potentials do not arise on it.

When the coating warms up to the Curie point, above which the ferromagnetic properties of the coating disappear in temperature, it absorbs EMF energy much weaker, but still does not allow RF into the copper, because maintains electrical conductivity. Having cooled below the Curie point on its own or due to heat transfer to the soldering, the coating again begins to intensively absorb EMF and heats up the tip. Thus, the tip maintains a temperature equal to the Curie point of the coating with an accuracy of literally one degree. The thermal hysteresis of the tip is negligible, because determined by the thermal inertia of the thin coating.

To avoid harmful effects on people, soldering irons are produced with non-replaceable tips, tightly fixed in a cartridge of a coaxial design, through which they are supplied to the RF coil. The cartridge is inserted into the soldering iron handle - a holder with a coaxial connector. Cartridges are available in 500, 600 and 700 types, which correspond to the Curie point of the coating in degrees Fahrenheit (260, 315 and 370 degrees Celsius). Main working cartridge – 600; The 500th is used to solder especially small smds, and the 700th is used to solder large smds and scatterings.

Note: to convert degrees Fahrenheit to Celsius, you need to subtract 32 from Fahrenheit, multiply the remainder by 5 and divide by 9. If you need to do the opposite, add 32 to Celsius, multiply the result by 9 and divide by 5.

Everything is great about METCAL soldering irons, except the price of the cartridge: for “(company name) new, good” – from $40. “Alternative” ones are one and a half times cheaper, but are produced twice as fast. It is impossible to make a METCAL tip yourself: the coating is applied by spraying in a vacuum; Galvanic at the Curie temperature instantly peels off. A thin-walled tube mounted on copper will not provide absolute thermal contact, without which METCAL simply turns into a bad soldering iron. Nevertheless, making an almost complete analogue of the METCAL soldering iron yourself, with a replaceable tip, although difficult, is possible.

Induction for smd

The design of a homemade induction soldering iron for microcircuits and SMD, similar in performance to METCAL, is shown on the right in Fig. Once upon a time, similar soldering irons were used in special production, but METCAL completely replaced them due to better manufacturability and greater profitability. However, you can make such a soldering iron for yourself.

Its secret is in the ratio of the shoulders of the outer part of the tip and the shank protruding from the coil into the inside. If it is as shown in Fig. (approximately), and the shank is covered with thermal insulation, then the thermal focus of the tip will not go beyond the winding. The shank will, of course, be hotter than the tip of the tip, but their temperatures will change synchronously (theoretically, thermohysteresis is zero). Once you have set up the automation using an additional thermocouple that measures the temperature of the tip tip, you can then solder in peace.

The role of the Curie point is played by a timer. It is reset to zero by a signal from the thermostat for heating, for example, by opening the key that shunts the storage tank. The timer is started by a signal indicating the actual start of the inverter operation: the voltage from the additional winding of the transformer of 1-2 turns is rectified and unlocks the timer. If you do not solder with a soldering iron for a long time, the timer will turn off the inverter after 7 seconds until the tip cools down and the thermostat issues a new heating signal. The point here is that the thermal hysteresis of the tip is proportional to the ratio of the times of switched-off and switched-on heating of the tip O/I, and the average power on the tip is proportional to the reverse I/O. Such a system does not maintain the temperature of the tip up to a degree, but it provides +/–25 Celsius with a working tip of 330.

Finally

So what kind of soldering iron should you use? A powerful wirewound resistor is definitely worth it: it costs nothing at all, it doesn’t require eating, but it can help out a lot.

It is also worth making sure that you have a simple soldering iron for SMD from an MLT resistor on your household. Silicon electronics is exhausted, it is at a dead end. The quantum one is already on its way, and the graphene one is clearly looming in the distance. Both do not interface directly with us, like a computer through a screen, mouse and keyboard, or a smart phone/tablet through a screen and sensors. Therefore, silicon frames in future devices will remain, but exclusively SMD, and the current scattering will seem something like radio tubes. And don’t think that this is science fiction: just 30-40 years ago, not a single science fiction writer thought of a smartphone. Although the first samples of mobile phones were already available then. And an iron or a vacuum cleaner “with brains” would never have occurred to the dreamers of that time even in a bad dream.

(1 ratings, average: 5,00 out of 5)

We offer you, as an option, to make with your own hands a miniature 12-volt electric soldering iron from available materials and available equipment. It will be very convenient for working with small-sized working material - when soldering leads of various microcircuits, parts of micro-earphones, hand-held electronic watches (or, for example, make one yourself) and all sorts of other miniature elements of modern radio electronics.

Homemade micro-electric soldering iron

The set of materials required for the product is quite small. You will need: copper wire for the soldering iron tip; copper foil, nichrome wire and tin tube - casing for the electric heater; plastic heat-resistant handle; electrical cord in heat-resistant insulation; office silicate glue and talc for electrical insulating mass.

You may have some problem with copper foil. But it is completely solvable. If there is no foil, then it is not difficult to find foil-coated fiberglass from which printed circuits and boards are made (if printed circuits or boards are not lying around anywhere, then fiberglass can be bought for 200 rubles in a radio store). You can separate the layer of fiberglass foil by heating it with an iron. It is difficult to pry the edge of the foil at the beginning, but then following the iron you will easily wrap the foil onto a round stick. The main thing is to pull the foil evenly.

Necessary equipment: electric or, tweezers, pliers, wire cutters, plates or boards for coating with adhesive, rags for wiping hands and tools.

The miniature soldering iron will be powered from a household electrical outlet through a 220/12 volt step-down transformer, the secondary winding of which should deliver a current of 1 ampere to a 12-ohm load. For example, the TVK-110L transformer, used for frame scanning in vintage tube TVs (Record-V300, Vesna-308 and the like), is quite suitable. will not be suitable for this purpose.

As a soldering iron tip, take a piece of copper wire 40 mm long and 1.5 mm in diameter. Sharpen one end of the wire in the form of a dihedral angle with a 40˚ angle, after which the edges of the angle (“cheeks” of the tip) are tinned. The manufactured tip will be located inside the heating element.

Now prepare a special electrical insulating mass: knead talc using office silicate glue (liquid glass) until it becomes a thick dough. With this mass you will apply thin layers of insulation to a cylindrical surface using any devices (tweezers, boards, plates). Please note that the prepared raw mass is very sticky, and to protect your fingers and tools from sticking, sprinkle them with dry talcum powder from time to time.

Around the tip, tightly roll a tube 30 mm long from copper foil - the base for the heating element (the end of the tip 10 mm long will stick out of it). Carefully cover the tube with a thin layer of electrical insulating compound. Then, holding it over a gas or electric burner (temperature should be 100-150˚), dry until the electrical insulating dough is completely “sintered.”

Wind a heating coil of nichrome wire 350 mm long and 0.2 mm in diameter onto the prepared base of the heating element. Lay the coils tightly together in one layer. Don’t forget to leave straight ends – wire leads: one – 30 mm long, the other, “turnover” – 60 mm. Cover the winding with a protective electrical insulating layer and repeat drying completely.

When the winding insulation is dry, wrap the long (“turn over”) end of the wire back and, pressing it firmly against the surface of the tube, apply a third layer of your dough-like mass and repeat the drying process again. The heating element of the soldering iron is ready.

Also cover the two ends of the wire protruding from the heating element up to half of their length with electrical insulating mass (the remaining halves will be connected to the conductors of the electrical cord). This operation will require special patience and accuracy from you: you often have to additionally fill with raw “dough” the microcavities that remained due to oversight or carelessness and each time dry it over the burner.

The final design procedure is the assembly of a micro-electric soldering iron. Stretch an electrical cord in heat-resistant insulation through the inner cavity of the plastic heat-resistant handle and screw the ends of your nichrome electric heater to its bare wires.

And finally, the last coating and drying procedure: insulate the exposed junctions of the electric heater with the electrical cord. After this, mount the electric heater into a suitable sized tin protective casing and connect the casing to the handle.

After control switching on and warming up, your miniature 12 volt soldering iron will be ready for use.

When working with soldering, any radio amateur will always need a can of compressed air so that he can blow off dust from the board. In this article you will learn how to make such a can at home.

Now watch this useful video: