Do-it-yourself soldering iron at home in different ways. Soldering iron: selection, manufacture and improvement - types, options, schemes, nuances Homemade powerful soldering iron for 220v

A soldering iron is an attribute of any radio amateur, from a professional to those who have just started. Today on sale you can find soldering irons or even soldering stations of any size. But they all have one big minus - they are quite rough and they have a large distance from the end of the sting to the edge of the handle. Such dimensions are convenient when soldering large parts, but when working with small elements, such devices are inconvenient, due to the fact that they are very heavy. position. Having looked through the schemes of miniature soldering irons on the Internet, I found that many of them have some design flaws: a non-replaceable tip, lack of grounding, and much more. So I decided to try to create more modernized“assistant” for a beginner radio amateur based on several instructions. The features of our future soldering iron include: a small distance from the end of the tip to the edge of the handle (~ 30 -40 mm), handle diameter (~ 15 mm), the ability to replace the tip and heating elements (reserve), ease of manufacture, which does not require any special knowledge.

Homemade miniature low-voltage soldering iron - drawing

As a handle, an ordinary brush was used, which was preliminarily polished and lacquered.
For a good fastening of the wires in the handle, I used such a homemade knot: I made a thread in a hollow rivet and glued it into the handle. Here you can easily fix the cable using the locking screw.
Then I moved on to the manufacture of mounts for the heat shield. They were also made from hollow rivets, but with a smaller diameter. M1.6 thread was created in them and glued into the handle holes.

The heating element was taken from an ordinary inexpensive Chinese soldering iron, after some manipulations with the dimensions, it fit perfectly with our device.

This element has a power of 7 watts and a length of 6.5 mm. Power is supplied by an adjustable power supply unit - from 0 ... 18 Volts. At the same time, the heating temperature can reach 280 degrees.
In the back of the pen was glued a regular spring, which can be borrowed from a regular ballpoint pen. This part is necessary to protect the power cable from breaking.
The ground and power wire is threaded in cambric. A socket for grounding is pressed into the main opening of the plug, which is designed for the cable, and the power cables are led out through an additional hole.
As you can see in the picture, the resulting home-made miniature low-voltage soldering iron in its dimensions barely casts from an ordinary fountain pen.

Sometimes there are situations when the owner simply cannot do without a simple soldering iron. For example, you need a multi-core cable for an outlet, or from a burned-out appliance. At such moments, one has to either borrow an instrument, or postpone the matter for an indefinite period. After all, not everyone wants to buy an expensive soldering iron or soldering station unless he is a repairman. However, there is a simple way out of this situation - to independently assemble a small soldering iron, it is just right for small work. The manufacturing process will not take much time and effort, but you can save some money and gain invaluable experience. Next, we will tell you how to make a soldering iron with your own hands at home. You will be offered several designs, and you can choose the one that suits you the most.

Idea #1 - Use a Resistor

The first and most simple technology for making an electric soldering iron with your own hands is using a powerful resistor. The device will be designed to operate at a voltage of 6 to 24 volts, which will allow it to be powered by various current sources, and even make a portable version powered by a car battery. In order to make your own tool, you will need the following materials:

To make a soldering iron from a resistor at home, you must follow these steps:

At the end of a thick copper rod, you need to drill a hole and drive the thread under the screw with a tap. It is also necessary to cut a groove for the retainer, which in our case is the spring ring. This can be done with a triangular needle file or a hacksaw.
From the second end, drill a hole with a diameter like a thin rod, which will act as a mini soldering iron tip.
All elements of the rod must be assembled into one whole, as shown in the photo.
The resistor is prepared for mounting the soldering iron tip, which must be inserted and fixed at the back with a screw with a washer.
From a textolite or plywood plate, you need to make a comfortable handle with a seat for a resistor and a wire with your own hands. To do this, use a jigsaw to cut out two identical halves of the handle and make holes and recesses for screws and nuts.
Connect the power cord to the heater terminals. It must be screwed onto the screws so that the contact is reliable.
The finished homemade soldering iron is twisted and checked.

We draw your attention to the fact that with such a portable gun you can easily solder microcircuits and even with your own hands. It can work not only from the power supply, but also from the battery. On the forums, we met a lot of feedback, where this option homemade products were connected from the cigarette lighter to 12 volts, it is also very convenient!

Please note that when first turned on, all soldering irons may smoke and stink for a while. This is normal for any model, as some elements of the paintwork will burn out. This will stop later.

Video instructions for making a simple electrical appliance

Idea number 2 - The second life of a ballpoint pen

There is another unusual, but at the same time simple idea how to make a soldering iron with your own hands from improvised materials for soldering small parts or smd components. In this case, again, it will come in handy for us, but now it’s not PEV (as in the previous version), but MLT, with a power of 0.5 to 2 watts.

So, first you need to prepare the following materials:

Ballpoint pen of the simplest design.
Resistor with characteristics: resistance 10 Ohm, power 0.5 W.
Double-sided textolite.
Copper wire with a diameter of 1 mm, it can be wound from an old choke or bought in an electrician's store copper wire in isolation and carefully remove it with a clerical knife
Steel or copper wire with a diameter of not more than 0.8 mm.
Wires for connecting to the network.

Making a soldering iron from a pen at home is quite simple, you just need to follow these steps:

Remove a layer of paint from the surface of the resistor. This operation can be carried out with the help of a skin, a needle file or a file, in extreme cases, a knife. The main thing is not to overdo it, so as not to damage the resistor. If the paint is difficult to remove, connect the product to a regulated power supply and heat it up a little.
2 wires come out of the barrel, cut one of them and drill a hole for a copper wire in this place (diameter 1 mm). To prevent the wire from touching the cup (this must be avoided), countersink with a thicker drill, as shown in the photo below. In addition, you need to make a small cut for the wire right on the resistor cup. A triangular file will help you with this again.
Bend the steel wire into the shape of a handle with a ring fastening, with a diameter similar to that of a drank on a cup. If you have copper wire, then you need to clamp the cup in it and twist it with pliers so that the contact is reliable, but do not overdo it, otherwise you will wrinkle the body. Remember that the wire must be without varnish insulation.
Carefully cut out the board from the double-sided PCB with your own hands, exactly the same as shown in the example in the photo. It is not necessary to buy new leaf textolite. You can use a jigsaw to cut a suitable piece from any unnecessary double-sided board. Or do without it altogether: twist the wire with wires, and attach them to the handle with superglue. The main thing to pay attention to is that the distance between the heating element and the handle is more than 5 cm, otherwise the plastic may melt.
Next, you need to assemble a homemade soldering iron from the handle, which should not cause difficulties.
It remains to install a thin sting in the seat. To prevent the copper wire from burning through the resistor, you need to make a protective layer of a piece of mica or ceramic between the back wall and the sting.
The last thing to do is to connect the homemade product to a 1 A power supply and a voltage of no more than 15 Volts using wires.

That's the whole technology of creating a homemade mini soldering iron at home. As you can see, there is nothing complicated in the manufacture of this tool, and you can easily cope with it, and all the materials can be found at home by dismantling old equipment or looking for them in the bins.

How to make a more complex model of a mini soldering iron at home?

Video review of a device with nichrome wire, powered by 12 volts

Idea #3 - Powerful Impulse Pattern

This option is suitable for those who are already more or less familiar with radio engineering and can read the corresponding diagrams. A master class on making a homemade pulsed soldering iron will be provided following the example of this scheme:

The advantage of this tool is that the tip heats up within 5 seconds after turning on the power, while the heated rod can easily melt the tin. At the same time, it can be made from a switching power supply from a fluorescent lamp, slightly improving the board at home.

As in the previous examples, we will first consider the materials from which you can make a soldering iron with your own hands at home. Before assembly, you must prepare the following improvised means:

All you need is to connect the tip to the secondary winding, which, in fact, is already part of it. After that, one of the ballast leads must be connected to the primary winding of the transformer and all the elements of the circuit must be fixed in a reliable case that will protect you from accidental electric shock, since the circuit contains a life-threatening voltage of 220 volts!

The principle of operation of this design is that the ballast from the lamp creates an alternating voltage that is applied to the primary winding of the transformer and is reduced to low values, while the current increases many times over. One turn, which is, in fact, the tip of the soldering iron, acts as a resistor, on which heat is dissipated. When the button is pressed, current is supplied to the circuit, and rapid heating occurs, after the button is released, the tip cools quickly, which is very convenient, since you do not have to wait long for the tool to heat up and cool down.

Idea #4 - Simple Wire Option

There is another option for making a miniature soldering iron - using nichrome wire. For this you will need:

Manufacturing process:

Drill a hole in the bar for the copper wire 3 times larger than its diameter.
Put a piece of copper wire in it so that it protrudes about 5 cm and fix it there with thick plaster putty, let it dry.
Put on a copper bar, which is a sting, insulation and wind the required amount of nichrome wire, leaving a distance between the turns. Also put insulation on the ends and bring them closer to the handle. Then connect to twists with wires. Tape them to the handle with electrical tape.

That's all, you got another simple and robust construction soldering iron, made by hand.

We still recommend using either the first or the second option, which is more understandable and easier to manufacture. As for the transformer version, although it is more powerful, it is still not so convenient to use. We hope that these photo instructions were useful for you and finally we recommend that you definitely watch all the video examples in which the assembly process is considered in more detail!

Also read:

I recommend to the readers of the magazine an easily calculated, easy to manufacture and very reliable electric soldering iron. For example, I have several of these at home: from a “tiny machine” for working with microelectronics to a powerful “cleaver”, with which I patch leaky metal tanks, repair well filters and other large-sized parts. Moreover, the heating element for each electrical appliance is ... a resistor of the appropriate power (type PE or PEV), powered by a household electrical network with a voltage of 220 V. Extinguishing resistances, if you cannot do without them, are reactive, more precisely, capacitive, allowing you to solve rather complex electrical problems with minimum sizes the devices themselves.

As practice has shown, to carry out calculations in the manufacture of soldering irons with resistor heaters, it is enough to know Ohm's law (I \u003d U / R), the elementary power formula (P \u003d IU) and tolerably use four arithmetic steps.

Suppose that, having a PEV30 vitrified resistor with a nominal value of 100 Ohms, you decided to make a soldering iron based on it for operation from a 220 V power supply. Referring to the above ratios, it is easy to determine the required data: current 2.2 A, power consumption 484 W. But…

The 30-watt parameter appearing in the name of the resistor used is the dissipation power at which the PEVZO can maintain its nominal value for a long time (thousands of hours!) without noticeably heating up. Mounted as a heater in a soldering iron (of course, with an inserted copper heat sink rod), this resistor must and can dissipate power many times greater than the nameplate one.

True, 484 W will also be unbearable for him - it will melt. Taking this into account, we will lower (for example, four times) the power per 100-ohm PEV30 by connecting a special damping resistance in series with it. Then the current that will flow through such a circuit will also decrease and become equal, according to calculations, to 0.55 A. This means that the voltage drop across the heater resistor will now be only 55 V.

But the network is 220 V. Therefore, 165 V is the proportion of damping resistance, the value of which, according to the law of electrical engineering known from the school bench, should be equal to 300 Ohms. As such an element of the chain, it is impossible better fit capacitor (for example, type MBGCH), designed for an operating voltage of 250-300 V.

We know from theory that the equivalent resistance of a 1 microfarad capacitor at a frequency of 50 Hz is approximately 3 kΩ. We need 300 ohms. Given this, we select the capacitance of the quenching capacitor 10 times larger, that is, equal to 10 microfarads.

So, the necessary data is received. Now you can proceed directly to the manufacture of the soldering iron itself.

The rod is machined (or purchased with subsequent refinement); material - red copper, diameter - with a minimum (in relation to the inner hole of the selected resistor) gap, which during assembly is recommended to be filled with silicate office glue (not shown in the figure). Although the glue impairs heat transfer from the heater, it dampens the “copper rod - nichrome spiral” system, protecting the fragile ceramic base of the vitrified resistor from cracking. In addition, the crystallized adhesive layer virtually eliminates the occurrence of backlash in the main assembly of the soldering iron.

1 - sting (copper rod), 2 - resistor, 3 - asbestos threads, 4 - electric cord, 5 - ceramic bushing, 6 - handle (plastic based on thermosetting resins), 7 - rubber bushing, 8 - metal tube body, 9 - M4 bolt (3 pcs.), 10 - insulation (lacquered cloth), 11 - metal casing.

As for the conductive wires welded to the resistor terminals, it would seem that they can simply be brought out through a hole in the tube-case. But with a high power soldering iron, it is difficult to avoid melting and burning the insulation at the cord (and there it is not far from short circuit). Therefore, it is better to play it safe by reinforcing the insulation at the point of connection of the cores to the resistor with a heat-resistant asbestos thread (followed by impregnation with silicate glue) and installing a ceramic sleeve on the tube body. It will not be superfluous to use an additional elastic (rubber) sleeve at the input of the power cord into the soldering iron handle.

Last advice. The power of the soldering iron can be quickly changed by adding or reducing the capacitance of the capacitors in the battery. For example, in order to quickly heat up the working rod, it is enough to connect two more of the same in parallel instead of the 10 microfarads used. The total electric capacity of the battery will then triple. As the required temperature is reached, the power can be reduced, leaving connected, say, 20 microfarads (with long work limited even to the previous 10 microfarads). Moreover, if the mass of the heated rod is solid, then it happens that preference is given to a soldering iron with a quenching capacity, the real value of which is less than necessary, and only occasionally (and not for long) is a reserve connected - the entire battery of capacitors.

To assemble a soldering iron with your own hands, home (and not only) craftsmen are primarily driven by economic considerations. A simple 220 V soldering iron for ordinary small soldering work is better, of course, to buy. However, it is also possible to modify it without disassembling it in order to extend the life of the sting. But here is an “ax” for 150-200 W, which can be used to solder metal water pipes, is no longer 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 mains from a 12 V car or a pocket lithium-ion battery. How to independently make a soldering iron for such cases, and not only for such cases, is discussed in today's publication.

What is smd

Sub Micro Devices, subminiature devices. You can clearly see smd by opening a mobile phone, smartphone, tablet or computer. Using smd technology, tiny (perhaps smaller than a match cut) components without wire leads are mounted by soldering onto contact pads, called polygons in smd terminology. The landfill can be with a thermal barrier to prevent heat from spreading along the paths printed circuit board. Here the danger is not only and not so much in the possibility of peeling the tracks - the piston connecting the mounting layers can break from heating, which will make the device completely unusable.

A soldering iron for smd must be not only micro-powerful, up to 10 watts. The heat reserve in its tip should not exceed that which the soldered part can withstand. But long soldering with a soldering iron that is too cold is even more dangerous: the solder still does not melt, but the part warms 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 time limit and / or the amount of heat transfer during soldering, or in the operational, during the current technological operation, temperature adjustment of the tip. Moreover, you need to keep it 30-40 degrees higher than the melting point of the solder with an accuracy of literally up to 5-10 degrees; this is the so-called. permissible temperature hysteresis of the tip. This is greatly hindered by the thermal inertia of the soldering iron itself, and the main task in designing one is to achieve its lowest possible time constant for heat, 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 plumbing, and accurate enough mini for smd.

Note: in fact, 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 as a sting. If the working part of the soldering iron is mounted on the rod, it is called a tip. Let's assume that the tip with the rod is also a sting.

Simplest

For now, let's not get into the complexity. Let's say we need a regular 220V soldering iron without any fuss. We go to choose and see the difference in prices reaches 10 or more times. We understand why. First: a heater, nichrome or ceramic. The latter (not "alternative"!) Is practically eternal, but if the soldering iron is dropped on a hard floor, it can crack. The tip of soldering irons on ceramics is necessarily non-replaceable - which means you need to buy a new one. And the nichrome heater, if the soldering iron is not forgotten 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 pity. Nickel-plated copper with special additives dissolves little with solder and burns very slowly in the soldering iron holder, but it is expensive. Brass or bronze heats up worse, and it is impossible to solder smd with them - the temperature hysteresis cannot be brought back to normal due to the much worse thermal conductivity of the material than that of copper. The red-copper sting is also 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 the very thing, its thermal conductivity is the maximum possible, and thermal inertia and hysteresis are minimal. True, you will have to change it often, but the sting is 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 work and letting the soldering iron cool, the tip is removed, beaten off the oxide by tapping on the edge of the table, and the soldering iron clip channel is blown through. With the dissolution of solder, it is worse: it is often inconvenient to grind the sting and it quickly works.

You can make a soldering iron tip made of ordinary red copper many times more resistant to the action of molten solder without sharpening its working end, but forging it to desired shape. Cold copper is perfectly forged with an ordinary metalworker's hammer on the anvil of a desktop vise. The author of this article has had a forged tip in the ancient Soviet EPTsN-25 for more than 20 years, although this soldering iron is at work, if not every day, then certainly every week.

simple 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 dissipating the rated power in free space, the wire resistors heat up to 210-250 degrees. With a heat sink in the form of a sting, the “wiremaker” keeps a long-term power overload by 1.5-2 times; the temperature of the sting 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 resistance of the resistor according to the formula: R = (U ^ 2) / (kP), where:

R is the desired resistance;

U - operating voltage;

P is the required power;

k is the above power overload factor.

For example, you need a 220V 100W soldering iron to solder 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 150 or 180 Ohm resistor, because There are no 160 Ohm "wire wires", this value is from a range of 5% tolerance, and "wire wires" are not more accurate than 10%.

The opposite case: there is a resistor with a power p, what power can a soldering iron be made of it? What voltage should it be powered from? Remember: P = U^2/R. We take P = 2p. U^2 = PR. We take from this value Square root, we get the operating voltage. For example, there is a 15 W 10 ohm resistor. The power of the soldering iron goes up to 30 watts. 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 a trifle with fusible 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 big with this soldering iron.

Manufacturing

How to make a soldering iron from a resistor is shown in fig. above:

We select a suitable resistor (pos. 1, see also below).
We prepare the details of the sting and fasteners for it. A groove on the rod is selected under the annular spring with a needle file. Threaded blind holes are made under the bolt (screw) and the tip, pos. 2.
We collect the rod with a tip in the sting, pos.3.
We fix the tip in the heater resistor with a bolt (screw) with a wide washer, pos. four.
We fasten the heater with a sting to a suitable handle with any convenient way, pos. 5-7. One condition: the heat resistance of the handle is not lower than 140 degrees, the resistor leads can heat up to such a temperature.

Subtleties and nuances

The soldering iron described above from 5-20 W resistors was made by many (including the author in the days of his pioneering youth) and, having tried it, they were convinced that they could not seriously work. It heats up for an unbearably long time, and only solders a trifle with a poke - a layer of ceramics interferes with heat transfer from the nichrome spiral to the sting. That 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 winding 0.02-0.2 mm nichrome is also not for everyone.

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

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

Only for a soldering iron, you need to look for old-type resistors PE or PEV (in the center in the figure, still in production). Their insulation is vitrified, withstands repeated heating to light red without loss of properties, it only darkens when it cools. The ceramics inside are clean. But the C5-35V resistors (on the right in the figure) are painted, inside too. It is completely impossible to remove the paint in the channel - the ceramics are porous. When heated, the paint chars and the sting sticks tightly.

Soldering iron regulator

An example with a low-voltage soldering iron from a resistor is given above for good reason. The PE resistor (PEV) from the trash or from the iron market most often turns out to be of the wrong value for the available voltage. In this case, you need to make a power regulator for the soldering iron. These days, it's much easier, even for people who have the most vague 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 is inexpensive. Permissible input voltage 5-36 V; output - 3-27 V at current up to 5 A. Voltage and current are set separately. Therefore, you can not only set the desired voltage, but also adjust the power of the soldering iron. There is, for example, a tool for 12 V 60 W, 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, the stock TC43200 multi-turn regulators are best replaced 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 an impulse soldering iron is either cold or slightly warmed up. Solder by pressing the start button. At the same time, the sting quickly, for fractions of a unit, heats up to operating temperature. It is very convenient to control the soldering: the solder spread, squeezed the flux out of the drop - released the button, the sting cooled down just as quickly. You just need to have time to remove it so that it does not solder there. The danger of burning a component with some experience is minimal.

Types and schemes

Impulse heating of the soldering iron tip is possible in several ways, depending on the type of work and the requirements for the ergonomics of the workplace. In amateur conditions, or for a small individual IP, a pulsed soldering iron is more convenient and more affordable to do one of the following. schemes:

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

Electrical circuit diagrams pulse soldering irons of these types are shown in Fig: pos. 1 - with a current-carrying sting 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 ways to implement at home.

50/60 Hz

The scheme of a pulse soldering iron with a tip under the current of industrial frequency is the simplest, but this is not its only advantage, and not the main thing. The potential at 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 the installers in the electronics production worked precisely with industrial frequency impulses. Disadvantages - bulkiness, significant weight and, as a result, poor ergonomics: on a shift 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: Bison, Sigma (Sigma), Svetozar, etc.

The device of a pulsed soldering iron at 50/60 Hz is shown in pos. 1 and 2 fig. Apparently, in order to save on production costs, manufacturers most often use transformers on cores (magnetic cores) of type P (pos. 2), but this is far from best option: in order for the soldering iron to solder like an EPTsN-25, the power of the transformer is needed 60-65 watts. Due to the large stray field, the transformer on the P-core in the short-circuit mode is very hot, and the heating time of the sting reaches 2-4 s.

If the P-core is replaced with a SL from 40 W with a secondary winding from a copper bus (pos. 3 and 4), then the soldering iron can withstand hourly work at an intensity of 7-8 solders per minute without unacceptable overheating. For operation in the mode of periodic short-term short-circuits, the number of turns of the primary winding is increased by 10-15% against 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 (pos. 5). Since its voltage is a fraction of a volt, this further increases the efficiency of the soldering iron and lengthens its operating time before overheating.

With forced heating

The scheme of a soldering iron with forced heating does not require special explanation. In standby mode, the heater operates at a quarter of the rated power, and when you press the start button, the energy accumulated in the capacitor bank is released into it. By disconnecting / connecting to the battery capacity, you can rather roughly, but within acceptable limits, dose the amount of heat generated by the sting. Dignity - the complete absence of induced potential on the sting, if it is grounded. The disadvantage is that on commercially available capacitors, the circuit is only feasible for resistor mini-soldering irons, see below. It is mainly used for episodic work on hybrid assembly boards not saturated with components, smd + ordinary printed wiring in through caps.

At high frequency

Pulse soldering irons at an increased or high frequency (tens or hundreds of kHz) are very economical: the thermal power at the tip is almost equal to the nameplate electric inverter (see below). They are also compact and lightweight, and their inverters are suitable for powering constant heating 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 by a constant voltage of 220 V.

Note: for power over approx. 50 W RF impulse soldering iron is not worth doing. Although, for example. computer IPBs come with a power of up to 350 W or more, but it is almost impossible to make a sting for such power - either it will not warm up to operating temperature, or it will melt itself.

A serious drawback is that the influence of the own inductance of the sting and the secondary winding affects the operating frequencies. Because of this, an induced potential of more than 50 V may occur on the tip for more than 1 ms, which is dangerous for the CMOS component (CMOS, CMOS). Also a significant drawback - the operator is irradiated by the power flow of the electromagnetic field (EMF). 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 - no more than 4 hours, but no more than 1.5 hours in a row.

The easiest way to circuit the inverter of a 25-30 W pulsed RF soldering iron for ordinary soldering work is based on a 12 volt halogen lamp power adapter, see pos. 3 fig. with diagrams. The transformer can be wound on a core of 2 K24x12x6 ferrite rings stacked together with a magnetic permeability μ of at least 2000, or on a W-shaped magnetic circuit 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 each. Winding 4 - 2 turns in parallel of a wire with a diameter of 2 mm or more (on a ring) or a braid from a television coaxial cable (pos. 3a), also parallel.

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 sq. cm.

The inverter option for a soldering iron up to 16 W can be made on the basis of a pulse starting device (IPU) for LDS or the filling of a burned-out economy light bulb, respectively. power (do not hit the flask, there are mercury vapors!) Refinement is illustrated by pos. 4 in fig. with diagrams. What is highlighted in green may be different in the IPU different models but we don't care. We need to remove the starting elements of the lamp (highlighted in red in pos. 4a) and short-circuit points A-A. We get the diagram of pos. 4b. In it, in parallel with the phase-shifting inductor L5, a transformer is connected on the same ring 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. Sting (pos. 4g) from the same wire. Finished device compact (pos. 4d) and can be placed in a convenient case.

Mini and micro on resistors

A soldering iron with a heating element based on a metal-film resistor MLT is structurally similar to a soldering iron made of a wire resistor, but it is performed at a power of up to 10-12 watts. The resistor operates with a power overload of 6-12 times, because, firstly, the heat sink through a relatively thick (but absolutely thinner) tip is larger. 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 on 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 for power up to 10 W, it is really possible to make only a soldering iron on MLT-2 for small discrete components (placers) and small microcircuits on your own, see for example. video below:

Video: micro-soldering iron on resistors

Note: the chain of MLT resistors can also be used as a heater for an autonomous battery soldering iron for ordinary soldering work, see next. video clip:

Video: rechargeable 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 - the MLT-0.5 case - is very thin and almost does not prevent heat transfer to the tip, but it will not let a thermal impulse through at the moment it touches the polygon, which is why they often burn out smd components. Having picked up a sting (which requires quite considerable experience), you can slowly solder smd with such a soldering iron, continuously monitoring the process under a microscope.

The manufacturing process of such a soldering iron is shown in Fig. Power - 6 watts. Heating is either continuous from an inverter from those described above, or (better) with forced heating direct current from IP to 12 V.

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/en/soldering_iron/

induction

The induction soldering iron is by far the pinnacle of technical achievements in the field of soldering metals with eutectic solders. In essence, an induction soldering iron is a miniature induction furnace: the high-frequency EMF of the inductor coil is absorbed by the tip metal, 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 RF currents, for example. computer switching power supply, see e.g. plot

Video: induction soldering iron

However, the qualitative and economic indicators of induction soldering irons for ordinary soldering work are low, which cannot be said about their harmful effects on health. In fact, their only advantage is that the sting that has become attached to the clip in the case can be torn out, for fear of breaking the heater.

Much more interesting are the induction mini-soldering irons of the METCAL system. Their introduction in the production of electronics made it possible to reduce the percentage of rejects due to errors of installers by 10,000 times (!) And lengthen the work shift to a normal one, and the workers dispersed after it vigorous and capable in all other respects.

The device of the METCAL type soldering iron is shown at the top left in fig. The highlight is in the ferronickel coating of the tip. The soldering iron is powered by high-frequency precisely sustained frequency of 470 kHz. The thickness of the coating is chosen such that at a given frequency, due to the surface effect (skin effect), the Foucault currents are concentrated only in the coating, which is very hot and transfers heat to the sting. The sting 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 terms of temperature, it absorbs EMF energy much weaker, but it still does not let HF into copper, because. maintains electrical conductivity. Having cooled below the Curie point by itself or due to the outflow of heat to the solder, the coating again begins to intensively absorb EMF and heats up the tip. Thus, the sting keeps the temperature equal to the Curie point of the coating with an accuracy of literally up to a degree. The thermal hysteresis of the tip is negligible, because determined by the thermal inertia of the thin coating.

In order to avoid harmful effects on people, soldering irons are produced with non-replaceable tips, tightly fixed in a coaxial cartridge, through which it is 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, corresponding to the Curie point of the coating in degrees Fahrenheit (260, 315 and 370 degrees Celsius). Main working cartridge - 600; 500th solder especially small smd, and 700th large smd and scattering.

Note: to convert degrees Fahrenheit to Celsius, you need to subtract 32 from Fahrenheit, multiply the remainder by 5 and divide by 9. If it is necessary the other way around, add 32 to Celsius, multiply the result by 9 and divide by 5.

Everything is great about METCAL soldering irons, except for 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. Making your own METCAL tip is unrealistic: the coating is applied by spraying in a vacuum; galvanic at the Curie temperature instantly exfoliates. A thin-walled tube mounted on copper will not provide absolute thermal contact, without which METCAL simply turns into a poor soldering iron. Nevertheless, to make yourself an almost complete analogue of the METCAL soldering iron, and with a replaceable tip, although difficult, but possible.

induction for smd

The device of a home-made induction soldering iron for microcircuits and smd, similar in performance to METCAL, is shown on the right in fig. Once 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 sting 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, the thermal focus of the tip will not go beyond the winding. The shank will, of course, be hotter than the tip, but their temperatures will change synchronously (theoretically, the thermal hysteresis is zero). Once you have set up the automation with the help of an additional thermocouple that measures the temperature of the tip of the tip, you can continue to solder safely.

The role of the Curie point is played by a timer. It is reset by a signal from the temperature controller 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 the soldering iron is not soldered for a long time, the timer will turn off the inverter after 7 seconds until the tip cools down and the thermostat gives a new heating signal. The bottom line here is that the thermal hysteresis of the tip is proportional to the ratio of the times of the turned off and on heating of the tip O / I, and the average power on the tip is the reverse I / O. Up to a degree, such a system does not hold the temperature of the sting, but +/-25 Celsius with a working sting of 330 provides.

Finally

So what kind of soldering iron to do? A powerful one made of a wire resistor is definitely worth it: there is nothing at all, it doesn’t ask for food, but it can help out thoroughly.

It is also worth making a simple soldering iron for smd from an MLT resistor on the farm. Silicon electronics is exhausted, it is at an impasse. Quantum is already on its way, and graphene clearly loomed in the distance. Both do not directly interface with us, like a computer through a screen, mouse and keyboard, or a smart phone / tablet through a screen and sensors. Therefore, the silicon framing will remain in the devices of the future, but only smd, and the current scattering will seem like something like radio tubes. And do not think that this is fiction: only 30-40 years ago, not a single science fiction writer thought of a smartphone. Although the first samples of mobile phones were already there. And an iron or a vacuum cleaner "with brains" to the then dreamers and in bad dream would not come to mind.

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A soldering iron is an indispensable device for radio amateurs and home craftsmen. Often there is a need to solder away from a 220 V electrical outlet and use, for example, a 12-volt car battery to connect. When soldering subminiature devices, mini soldering irons with special characteristics are needed. In this regard, many are wondering how to make a soldering iron with their own hands, getting a convenient device and saving money at the same time.

Soldering iron for SMD

SMD devices are microcircuits in mobile phones, laptops or tablets. The installation of circuit elements is carried out on a site with contacts, where there is a thermal barrier to prevent the spread of heat along the tracks.

Soldering iron requirements for SMD:

Power should not be more than 10 W;
The temperature of the soldering iron should not be more than that which the microcircuit element can withstand;
If the tip is too cold, then a long soldering procedure can worsen the part due to the long heat exposure time;
It is necessary to achieve a temperature of the tip about 40 ° C higher than the temperature at which the solder melts. Here the main obstacle is the inertia of the soldering iron.

Sting material

Most best sting- nickel-plated copper, with additives. This is the most expensive material and it is problematic to find it for making a soldering iron with your own hands.

A tip made of bronze or brass is not suitable for soldering SMD boards, because it has a high thermal inertia.

A copper sting also has disadvantages: a short service life due to burning, but it can simply be changed. But copper has a high thermal conductivity, and better material for work with miniature boards no.

You can make a mini soldering iron with your own hands from the MLT-0.5 resistor. Its tube is thin enough and will not interfere with heating the sting.

What needs to be prepared:

case from a simple ballpoint pen;
MLT-0.5 with a resistance of 5 to 10 ohms;
a piece of textolite 1-3 cm;
steel wire 0.8 mm;
copper wire 1 mm.

Manufacturing steps

Strip the resistor from paint with a sharp object. If it is cleaned poorly, connect to a power source for warming up;

Cut off the lead from one end of the resistor and drill a hole into which a piece of copper wire is inserted - the future soldering iron tip. Straighten the second conclusion and leave it, it will serve as one current conductor;

Important! The sting should enter the hole in the ceramic body, but not touch the walls of the side metal cup. To do this, the hole in the cup should be slightly wider than in the body. By the way, a case with holes exists only for domestic resistors.

On the surface of the same metal cup, a cut is made for laying the second conductor;
The second conductor is made of steel wire, which is bent so that an open ring is formed in the middle, which fits tightly into the cut made;

In the upper part of the body of a ballpoint pen or some other suitable hollow plastic rod, a board made of double-sided textolite should be installed, which is given the necessary shape;
A steel wire ring is put on the cup and soldered to ensure good contact. This negative conductor still serves as a fastening element;
Conductors are soldered to the upper part of the PCB board on both sides, and conductors are threaded to the lower part, which are threaded into a plastic tube (handle body);
Before you put the sting, a tiny piece of mica must be placed inside so that the copper does not come into contact with the resistor cup located at the other end. The sting can be replaced periodically.

For the supply wire, it is good to take MGTF. Its insulation withstands accidental contact with the heating element. Soldering with such a home-made tool is performed with ordinary solder and flux. Homemade soldering iron powered by BP. It is necessary to get 7-10 V at the output, depending on the resistance of the resistor. It's a good idea to use a PSU where you can adjust the voltage.

Resistor soldering iron

The wire resistor is an existing nichrome heater. It is able to heat up to 250°C when the power is dissipated into the surrounding space. If you install a tip that will remove heat, the resistor can withstand a double power overload for a long time. The tip will heat up to 300°C. You can also increase the heating by creating a threefold overload, but then the home-made soldering iron must be periodically (after 1.5 hours) turned off.

When calculating the soldering iron, the resistance and power of the resistor are taken into account. The resistor must be taken of the PEV type, old, but still being produced. They are covered with vitreous enamel, withstand repeated overheating, they can only darken.

Important! Resistors of type C5-35V, which cannot be used, are painted on all sides. The paint is not completely removed. When a device made from them is heated, the paint melts, the sting can stick forever, without the possibility of replacement.

From the PEV-10 resistor, you can design a soldering iron with a power of 30-40 watts. At the same time, if powered from a 12-volt source, the resistance should be approximately 5 ohms. If the device will operate from a 220 V network, it is necessary to use PEV-20 with a significantly higher resistance. The design of such a soldering iron is similar in principle, but differs in execution.

How to make a mini soldering iron from a resistor powered by a 12-volt voltage source can be seen in the example:

It is necessary to prepare the design of the sting so that it is closely inserted into the ceramic body. A copper rod is taken with a diameter approximately corresponding to the size of the hole in the case, and drilled from two sides: under the sting, which will be a slightly smaller rod, and under the bolt for fasteners. In both holes it is necessary to cut the thread, as well as on the surface of the sting;

A cut is made on a larger rod, where a ring is put on to fix the entire structure;
Now you need to solder the electrical cord to the terminals of the resistor and make a convenient handle from insulating material. To protect and strengthen the copper terminals of the resistor, metal clips can be attached to them from above.

Important! The operating current of the manufactured mini soldering iron should not be higher than 1 A.

These are the two simplest designs of an electric soldering iron. Experienced home craftsmen can complicate them without using a resistor, but by making heating element on one's own.