If in Soviet times there was a game for schoolchildren, the essence of which was to solder a radio-electronic microcircuit on their own, which they successfully did, but now the question of how to properly use a soldering iron puts many in a difficult position. Although learning how to solder with a soldering iron is not so difficult, and having mastered the basics for “dummies”, you will be able to carry out simple work on your own without turning to specialists.
Tool selection
A soldering iron is a tool with a heating element used to join fusible materials. According to the method of heating they are divided into:
- electrical;
- hot air;
- gas;
- induction
Soldering irons: 1-Electric, 2-Hot air, 3-Gas, 4-Induction
Electric soldering irons are used to work with electrical circuits and SMD boards . On average, they have a power of 15-40 watts. Using devices with a power of more than 100 W, large parts are soldered: radiators, copper tubes of different diameters, etc. Large hammer soldering irons with a power of up to 550 W are used in various industries: mechanical engineering, metallurgy, etc.
The choice of a particular tool is influenced not only by the size of the parts, but also by the thermal conductivity of the material from which it is made. It is this that determines the heating temperature, and, consequently, the required power. For example, copper may require a higher heating temperature than a similarly sized steel part. It is worth noting that when soldering copper parts, a situation may even arise where high thermal conductivity leads to unsoldering of connections made earlier.
The main element of the device (I remind you that we work mainly electrically) is the heating rod. It consists of a copper tube and a nichrome spiral wound on it. On one side of the rod, hidden in the handle of the device, current flows, and on the other, a tip made of a knurled copper rod is inserted. The tip of the sting is sharpened to a bevel. The tip is heated by closing the current on the nichrome spiral.
For electrical work, a lightweight, compact size tool with low heat capacity is suitable. To avoid voltage dissipation, it is better to choose a model that has a three-way ground plug. For a novice electrical engineer, a model up to 30 W will be sufficient. If you plan to repair a car using a soldering iron, then it is better to use 40-watt devices - for quickly connecting wires of any type over a large area. For comfortable operation of soldering irons in cars, special attachments are sold.
Many electronics repairmen use a soldering station. This design includes a set of all the tools necessary for soldering work: a soldering iron with replaceable tips, a stand, a voltage control unit, a hot air gun, cleaners and a desoldering pump.
Many people are interested in the question of whether it is possible to solder without a soldering iron. Yes, you can, in this case the solder and parts will have to be heated for tinning and soldering over an open fire. This allows you to create more or less high-quality connections, but the technology is less secure. In addition, a beginner who does not have sufficient experience may have great difficulties when working with materials such as copper, aluminum or stainless steel.
Features of dismantling
There are many known technical techniques that allow you to solder a microcircuit with a soldering iron, each of which has its own advantages and disadvantages.
You can remove electronic parts from boards without damaging the contacts in the following ways:
- by heating the soldering areas with just a soldering iron (with the addition of flux);
- through a special suction that removes molten solder from the contact pads;
- using a metal braid from a coaxial cable applied to the soldered leg;
- using heat-conducting metal plates (blades) or copper attachments that have slots for the contact patches of microcircuits.
The first three methods are suitable if you have a soldering iron whose power exceeds 25 watts.
The option of using special attachments involves replacing the working tip and is only suitable in combination with “powerful” soldering stations (more than 40 watts), capable of heating it together with the contacts soldered into the board.
In addition, this method of desoldering a part is only suitable for microcircuits with a suitable arrangement of legs for the configuration of the nozzle. The approach that has become more widespread is when a regular razor blade is used as a heater.
Solders and fluxes
Before soldering wires or electrical circuits, you must select the appropriate solder. Tin-silver and tin-lead solders and rosin are suitable for this work. Solders containing lead provide higher quality soldering, but have the disadvantage that this metal is harmful. Tin is used for soldering parts and materials that require safety for the body, for example, dishes.
The marking of solders indicates the metals included in its composition and their content. So, for example, POS-40 solder contains tin and lead (tin-lead solder). The number 40 indicates 40% tin content. The amount of lead in PIC solders affects the color (becomes darker) and the melting point (increases). For electrical work, POS with a tin content of 30% to 61%, as well as PSR-2 and PSR-2.5, are most often used. In the marking of tin-silver PSr-2.5, the number indicates that 2.5±0.3% of the solder is silver.
Solder
To clean the surface for soldering from oxides, special mixtures are used - fluxes. They are one of the most important factors affecting the quality of soldering. The flux must be selected to match the properties of the material being soldered and be strong enough to destroy the oxide film. Active acid-based fluxes are prohibited from being used for soldering microcircuits and circuit boards, as they cause corrosion and destroy contacts, but when working with chemically resistant metals, you cannot do without them. Today, when soldering, as a rule, they use soldering acid (zinc chloride), alcohol-rosin solution LTI-120 and borax (for soldering metals such as copper, cast iron, steel, brass).
If you are going to solder headphones, speakers or motherboard contacts, then you can use rosin as a flux. However, it should not be used for soldering microcircuit elements and circuit boards. And pay special attention to the following: you cannot use rosin for musical instruments! It heavily contaminates the adhesion site.
Flux
We recommend watching this video. It may answer remaining questions about fluxes and solders.
Using a razor blade
The main problem with soldering microcircuits is that they have several legs, which is why when one of them heats up, the others have time to cool down. This inconvenience can be overcome by using a heat-conducting device that contacts several legs at once.
In this case, the thermal power of the tip is distributed evenly between them and ensures that the solder melts in several contact areas at once. A simple razor blade can be used as such a device; to heat it up, you will need a soldering iron of suitable power or a hot air gun.
When heating the steel blade, it is recommended to slightly rock the chip on the soldered side, after which you can forcefully pull it out of the board. In the same way, the second row of legs is freed from solder.
Preparing for work
Of course, in order to become a master and solder parts of any complexity, you need time and experience. However, in order to repair headphones, attach an LED strip, or change capacitors on a computer board at home, you do not need to have special knowledge. Compliance with the instructions and electrical safety rules will allow you to complete this work without difficulty.
The condition of the tip is of great importance for the quality and efficiency of soldering. The process of caring for it is called tinning - the process of covering its surface with a thin layer of solder. This is done so that the copper from which the soldering iron tip is made does not oxidize. A soldering iron with an oxidized tip interacts poorly with solder and the material being processed. Each time, before soldering with a soldering iron, you should prepare it. First, we treat the tip of a cold soldering iron with a file or a stiff brush, cleaning the copper from dirt.
Cleaning the soldering iron with a brush (you can also use a file)
After cleaning the soldering iron.
Then, after heating the soldering iron to operating temperature, you need to alternately touch the rosin and then the solder several times. The alloy should evenly cover the working part.
Dip the soldering iron into the flux.
We touch the solder tip.
Below is a video on how to tin a soldering iron and prepare it for use. Perhaps the video shows it even better than our photographs, so we recommend watching it.
How to safely unsolder a transistor, microcircuit, diode
Soldering conditions
When creating a workplace, you should pay special attention to its lighting. You cannot solder a radio component in semi-darkness. If your vision does not allow you to clearly see all the details, then you need to wear corrective glasses.
The electronic board must be clearly fixed in space, and the body must be in a stable position. It is best to work sitting or standing on both legs, holding the soldering iron confidently. After all, any wrong move will cause irreparable harm.
Technology for dismantling radio components
The tip of the soldering iron should be precisely placed on the layer of solder located in the socket of one leg of the transistor and quickly melt it.
Then a needle is inserted into this place from the reverse side and the tin is separated from the stem. If there is a dismantling braid or desoldering pump, then use them.
When the design of a radio component allows the use of a metal clamp to remove heat from the housing, then it must be used.
If the space for installing the soldering iron tip is very limited, then they work without using a heat remover.
In this case, special attention is paid to the length of time the radio component remains at elevated temperatures.
Soldering boards and microcircuits
Very often, electric soldering irons are used for soldering printed circuit boards. A special small device of medium power is suitable for this. We recommend reading the article on choosing soldering irons for boards and microcircuits in more detail.
- First you need to prepare the surface so that it provides minimal resistance and a strong connection.
To degrease the board, you can wipe it with a cloth soaked in a soap solution. To remove hard deposits, a special product sold in a specialized store is suitable. The working area must be cleaned until the copper begins to shine. To treat contacts, you can use regular acetone. A less odorous and dangerous solvent is methyl hydrate. Degrease the board before soldering. - Once you've finished cleaning, place the pins and wires on the diagram. First of all, flat radio components, such as varistors and resistors, are soldered, and after them - large elements: potentiometers, capacitors, transistors, microphones, transformers, etc. This sequence serves to maintain the operating condition of sensitive components. When soldering charges or resistors, the wires should be bent at an angle of 45˚. Short wires and parts such as headphones, speakers, speakers can be pre-secured with insulating tape.
- Apply a small amount of solder to the tip of the heated soldering iron - this will improve the conductivity of the copper. Now you need to heat the connection - press the tip against the board component and hold in this position for 2-3 seconds. Be careful - if the heated area begins to bubble, you should immediately stop heating so as not to damage the board.
Soldering the board. - After applying solder to the soldering iron tip, apply it to the joint in the area being processed. After a small bump appears, you must stop soldering.
- Now you can turn off the soldering iron and start cleaning the area to be treated. In this case, care must be taken - the connection cannot be moved so that it is secured.
Below is a video that clearly describes the whole process: This soldering method allows a beginner to easily solder a radiator to the circuit, solder a button to a modem, an LED strip (more on this below) or repair a plug.
Board design
How to test a resistor with a multimeter
Printed circuit boards differ in the number of printed layers and the method of installing radio components:
- Single layer;
- Double layer;
- Multilayer;
- For DIP elements;
- For SMD components.
One board can contain both DIP and SMD elements on one or both sides. Multilayer printed circuit boards, in addition to outer layers, have internal ones, which usually serve for general shielding or wiring of power circuits. Thus, the motherboards of modern computers or mobile phones have up to seven layers.
Multilayer PCB
Soldering wires
The ability to solder wires can be useful in many situations. One of the most suitable examples is headphones that came out due to a broken wire. There are two main methods used to connect wires:
- The cores are placed on top of each other and soldered using solder.
- The wire strands are pre-twisted together and then tinned using solder.
In both cases, rosin is used. If it is necessary to clean the wires, liquid flux is applied with a brush. Other methods of soldering wires together are based on the two main ones described above and are presented in the following figure.
Methods for soldering wires together
To solder radioelements without printed wiring, two methods are used. The first (lap) is faster, and the second (twisting) provides greater reliability of the connection.
In order to repair headphones, the second indicated method is best suited (as it will provide greater connection strength). The procedure is approximately as follows:
- Find the damaged section of the wire and cut it out. Strip the edges of the wires to a sufficient length. To remove insulation, it is best to use a heated soldering iron or a flat, not very sharp knife.
- Place the wires next to each other (by color) and tin with rosin or FS-1 mixture.
- Wrap the treated area with electrical tape.
If the wire is damaged at the plug or headphone input, you will need to disassemble the case and solder the wires directly to the input pins.
Work order
Before starting work, it is necessary to prepare all tools, materials and devices so that they are at hand.
When installing or dismantling, the board can be placed on a thermal table. If a soldering gun is used for dismantling, then to prevent its impact on other components, you need to isolate them. This can be done by installing plates made of refractory material, for example, strips cut from old circuit boards that have become unusable.
When using a desoldering pump for dismantling, the process is more accurate, but takes longer. The desoldering pump “charges” as it cleans each leg. As it fills with pieces of solidified solder, it needs to be cleaned.
There are several soldering rules that must be followed:
- Soldering the microcircuits on the board must be done quickly so as not to overheat the sensitive part;
- You can hold each leg with tweezers during soldering to provide additional heat removal from the body;
- When installing using a hair dryer or infrared soldering iron, you must monitor the temperature of the part so that it does not rise above 240-280 °C.
Electronic parts are very sensitive to static electricity. Therefore, when assembling, it is better to use an antistatic mat that is placed under the board.
Soldering LED strip
Today, LED strips are actively used for installing interior lighting of varying complexity. It provides wide design possibilities, is small in size and is not inferior in performance to other lighting devices.
LED Strip Light
Regardless of the size and installation conditions, the tape is soldered according to the same instructions:
- Having cut the tape to the required length, the surface on which it is to be attached is degreased and dried.
- After tearing off the protective film from the back side, the tape is glued to the mounting surface.
- After this, the wires on the input contacts, small parts, dimmers, and controllers are soldered. During operation, you must avoid overheating the tape, this can lead to failure of the diodes.
Pay attention when soldering two strips! Plus should go to plus, and minus to minus!
The soldering process is shown in the photographs below:
We fix the LED strip (electrical tape was used)
A little solder on each contact.
Solder the wires, observing polarity.
Soldering irons with a power of up to 40 W are well suited for soldering diode strips. It is best to use wires with a cross section of 0.75 mm. Red ones are soldered to the positive contact, and black ones to the negative one.
Roll of LED strip.
Now let's talk about how to solder LEDs directly onto the board to create LED backlighting with your own hands. To do this, you will need the diodes themselves, a piece of the board for them (you can buy them at a radio store) and soldering accessories. To remove scale, we will use aluminum flux and tin as solder.
- We insert the diodes into the board so that the positive contacts (long “legs”) are located on one side, and the negative ones on the other. And bend the contacts to the sides. Be careful - if even one diode is connected incorrectly, everything will burn out.
- After treating the “legs” with flux, we solder them to the board.
- Cut off the excess length of the contacts using wire cutters. We strip the power wires to a length equal to the length of the diode row, apply them to the corresponding contacts and solder them.
- Ready! Now you can check the operation of the circuit by connecting the wires to a 12 V power source.
Principles of safe work with semiconductor radio components
Temperature conditions
All electronic devices are designed to operate at normal temperatures. They cannot withstand overheating for a long time and do not respond well to pulsed temperature influences: the semiconductor junction fails, contacts are broken, and the housing of the radio component is depressurized.
However, the main methods of their installation remain welding or soldering, which ensures the heating of the contact pads and their connection when cooling.
The brands of low-melting solders used, such as POS-60 or POS-40, begin to transform into a liquid state when heated to 183 degrees, and when cooled in air, they quickly cool down and create reliable contact.
The safety of the transistor, diode, microcircuit, capacitor is ensured due to the short time of melting and hardening of the solder on the leg of the radio component.
Board design
To ensure safe soldering, you should imagine the design of the board on which the radio component is attached. In practice, the most common models are with:
- one;
- or two layers of copper foil conductors onto which solder is applied.
They are glued onto dielectric plates made of fiberglass or getinax.
In addition to these models, special high-precision electronic devices use multilayer boards with a complex arrangement of conductive paths of various designs.
Installation of parts on them by soldering, using solder, is carried out by robots in a factory environment.
It is quite difficult for a home handyman to perform such work efficiently at home.
Soldering aluminum
There seems to be no difficulty in how to solder aluminum. After all, this material has high thermal conductivity and is easy to process. Despite this, when processing this metal, it is necessary to take into account some features.
Aluminum, when exposed to high temperatures, very quickly forms oxide films on the surface, and therefore for its soldering it is necessary to use special fluxes and soldering tips (coated with steel). And if processing aluminum wires is practically no different from working with other metals, then soldering flat aluminum surfaces is a much more complex process. First of all, you will need a soldering iron with a power of 60-100 W in order to heat large parts well.
- Before soldering aluminum, its working surface is cleaned of scale with sandpaper or a file.
- Afterwards it is degreased with gasoline, acetone or another solvent. Then the joint must be lubricated with a special flux.
- The soldering iron tip is dipped into rosin or ammonia until a slight haze appears. This cleans the copper from which the tip is made from oxides of other metals.
- Further actions are practically no different from working with other materials: the tip is lubricated in solder, after which a small amount of it is transferred to the soldering site for tinning. After this, the main layer of solder is applied.
Stainless steel is soldered in a similar way - this process also requires careful cleaning of the working surface before applying solder.
Cleaning the soldering iron
The sponge for cleaning the soldering iron should be moistened with water. Carefully wipe the hot soldering iron tip with several quick movements. Holding the tip in one place for too long can damage the sponge.
Cleaning (wiping) the tip of a dirty soldering iron with a damp sponge
The soldering iron tip does not need to be cleaned after soldering a single element. This should be done if the tip is noticeably dirty.
What are the dangers of microcracks in soldering in working devices?
The most dangerous thing about microcracks is sparking and air breakdown in working electronics. All this is accompanied by flammable sparks, loud bangs, acrid smoke, heating and melting of plastic. This is dangerous for humans.
For an electronic circuit, this is dangerous due to the failure of power transistors, expensive processors and burnout of board tracks. In general, this is not very pleasant and leads to expensive repairs. The photo shows soldering defects in the SMD component (resistor) and inhomogeneities in the BGA balls.
Soldering Station
In addition to the soldering iron, you can purchase a hot air soldering station. This is a powerful tool in the hands of a radio amateur. This tool is equipped with temperature settings accurate to one degree. The soldering station has a convenient stand. Using such a device, you can solder not only small radio components, but also desolder entire microcircuits from boards using hot air.
It will be interesting➡ The design of an ammeter and the principle of its operation
Soldering stations can significantly speed up your work. But to solder with such a station, experience is required. For beginners, there is no need for a soldering station at first. A simple soldering iron is enough to learn soldering skills. But once you get comfortable and confidently hold a soldering iron in your hand, you can think about more expensive equipment.
Soldering Station
