How to solder with a soldering iron using the example of soldering parts, wires and the ability to desolder them from the board (wires, radio components on the board) (video)

It is believed that about half of the failures of electronic boards are associated with a malfunction of the capacitor, without replacing which the further functioning of the circuit is impossible.

These parts themselves may vary both in characteristics and dimensions; however, they all have one thing in common - the presence of the main controlled parameter (capacity).

In order to check the capacitor installed in the circuit (including the so-called “electrolytes”), it is necessary to measure its capacitance. The faulty part will have to be removed from the circuit and then soldered on with a new one. Some types of capacitors do not need to be soldered, since they are attached by welding or clamps.

Does a resistor have polarity?

The author of Lithium asked a question in the Technology
: is there a difference (polarity) in how to solder resistors?! and got the best answer

Answer from Voldemar[guru] For resistors, there is no difference when desoldering. Observe polarity when soldering all active elements: transistors, diodes - their varieties: thyristors, dinistors, etc. When soldering active elements, there is a danger of their breakdown from static: this is for field-effect transistors - ground the soldering iron. Do not overheat them when soldering.

A resistor is one of the most commonly used elements in modern electronics. Its name comes from the English “resist”, which means resistance. Using a resistor, you can limit the effect of electric current and measure it, divide voltage, and set feedback in an electrical circuit. We can safely say that not a single electrical circuit or device can do without this element. That is why it is often necessary to measure the resistance of a resistor with a multimeter and check its performance. This material will tell you how to test the board for functionality with a multimeter.

The essence of soldering

Actually, what is soldering? This is the connection of conductors (such as wires or wires and traces on a board) using low-melting solder. It sounds simple, but in fact it is fundamentally important to ensure two things:

• reliable connection so that there is good contact all the time,
• sufficient connection area so that the soldering area does not overheat (relevant for power circuits).

• Exploitation

  Why doesn't rain short-circuit high-voltage lines?

However, it is worth noting that the solder itself has a high resistivity. Therefore, it is necessary that the thickness of the coated layer be small, and the coating area, on the contrary, be larger. Also note that the thicker the conductor (such as wire), the larger the area that needs to be covered.

What is a resistor

In Russian scientific literature, electrical resistors are often called simply “resistance.” From this name, its purpose immediately becomes clear - to resist the action of electric current. A resistor is a passive electrical element, since under its action the current only decreases, in contrast to active elements, which increase its effect.

From Ohm's law and Kirchhoff's second law it follows that if current flows through a resistor, then its voltage drops. Its value is equal to the strength of the flowing current multiplied by the resistance of the resistor.

Important! The symbol for a resistor in schematics is a rectangle, so it's easy to remember. Depending on the type of resistor, it is depicted as a rectangle with a symbol inside.

Resistors are divided according to installation method. They are:

• Output, that is, they are mounted through a microcircuit with radial or axial pins. This type was commonly used decades ago and is now used for simple devices;
• SMD, that is, electrical resistors without leads. They have only slightly protruding legs, so they are mounted into the board itself. In modern devices they are most often used, since with automatic board assembly by a conveyor it is profitable and fast.

Example of soldering for a soldering iron with a copper tip

Any soldering begins with tinning pads, wires, and other elements that will need to be connected together. Tinning is actually a surface coating of surfaces with solder. The purpose of this procedure is simple. The surface layer will provide good cohesion for future welding solder, and therefore a reliable connection during soldering. Here it is necessary to say something about the materials that you are going to solder. So let’s say, it will be good to solder, ferrous metals are already worse, but I wouldn’t advise you to solder aluminum at all. Because this is a troublesome and thankless task. It is here that it is necessary to say that if you have a choice, then choose copper wires and connectors for soldering; this choice will allow you to solder comfortably. So, about tinning with a copper soldering iron. We heat up the soldering iron, usually this time is 5-7 minutes. Don't even try before. During heating, you can dip the soldering iron into rosin or solder fat once to prevent oxidation of copper.

As soon as the tip begins to confidently melt the solder, consider it warmed up.

During this time, you can still clean the wire or pad from insulation and oxide. If it is a stranded wire, then after removing the insulation, twist all the wires together. Also, if the connection is permanent, then also connect the wires of different conductors to each other. Now place the wire(s) on the pad and treat it with acid, rosin, or grease.

That is, with the reagents that I wrote to you about earlier. They are the ones who will contribute to tinning, and as a result, to the soldering itself. In our case, this is solder fat, I heated it and dipped the wire into it. Now we grab an excess amount of solder onto the tip, in fact it will be a drop of solder. We bring it to the conductor and move along it.

The conductor should be filled evenly.

Now it will look like something covered in a metal shell. If there is not enough solder, then again take the solder with a tip and distribute it at the soldering site.

We carry out the same procedure with the other conductor. Now you can solder the conductors together. We set them up the way we need them and each time, bringing a little solder on the tip of the pin, we fill the gap between the conductors.

If necessary, take solder and bring it to the soldering site.

The result is a beautiful, durable and reliable contact. If necessary, the conductors can be twisted before soldering.

We isolate the soldering area. Now about soldering to the board. Here again we need to start with tinning the board tracks. If you are mounting something on a universal circuit board, then immediately take a board with tinned contacts. Next, we straighten the contacts of the radio component and insert them into the holes so that they protrude from the other side by 0.5-1 mm. Now, as in the case of the wire, we take solder onto the tip and bring it to the leg-hole location.

We touch it, and the solder spreads along the leg, filling the hole. So we solder all the legs of the radio element (wires).

Now, although you haven’t learned how to solder with a soldering iron with a copper tip, you know how it’s done.

Maintenance (tinning) of a copper soldering iron tip during and after soldering

As I already told you, the copper tip fades over time and eventually changes its shape. As a result, it is necessary to put its shape in order from time to time. It is best to forge the tip, that is, use a hammer and anvil, and tap out the desired shapes. But if this is not the case, then you can get by with a simple needle file.

We take and process the sting so that it fits the shape (size) that is convenient for you. For me, this shape is the shape for a flat-head screwdriver. The two sides are ground off with a needle file, resulting in a smooth but “bare” metal – copper.

It must be said that copper is a soft metal. Handles it accordingly easily. After this shaping, it is necessary to protect the tip from oxidation. This is done simply by applying solder to the surface layer of the tip, which performs two functions. Firstly, we use it to solder, which we have already discussed. Secondly, it protects the tip from oxidation and burnout. So, when we processed the tip cold, we turn on the soldering iron. While it is warming up, but not yet warmed up, you can dip the tip in rosin or solder fat.

Then we take solder and apply it to the heated tip. The solder itself will spread over its surface. The entire tip is ready for use.

Restoration of the tip must be carried out periodically when you notice that the area on it has become uneven, and as a result, soldering has become inconvenient.

What is a multimeter

A multimeter is a device that can measure AC or DC current, voltage and resistance. It replaces three analog or digital instruments at once: ammeter, voltmeter and ohmmeter. It is also capable of changing the main indicators of any electrical network and ringing it. There are two types of multimeters: digital and analog. The first are portable devices with a display to display the results. Most multimeters on the market today are digital. The second type is already outdated and is no longer popular. It looks like a regular measuring instrument with a graduation scale and an analog needle showing the measurement value.

Resistor ringing

The resistor can and should be called. You can ring without unsoldering the element from the board. Ringing an element for a break is done as follows:

1. Turn on the multimeter and turn off the device if dialing is carried out without soldering;
2. Using a multimeter without taking into account polarity, touch the terminals of the electrical resistor;
3. Record the value. If it is equal to one, then this indicates a malfunction and a break has occurred, and the element itself should be replaced.

When not soldering, you should take into account the fact that if the circuit is complex, then you may have to make connections through bypasses and circuits. It is possible to say that an element is 100% faulty only when at least one of its legs is soldered off.

How to unsolder a part from a board

In fact, soldering in most cases involves not only connecting contacts, but also separating them. If we need to disconnect the soldered wires, then we heat up the soldering area and everything is ready. However, with radio components everything is more complicated. It’s okay if it’s a resistor or transistor when there are 2-3 pins. In this case, after a break, we quickly warm up the contacts, and then remove the part from the board. You can use small pliers or tweezers to avoid burning your hands. But with microcircuits everything is much more complicated. Often their dismantling happens unilaterally, that is, when the legs are simply cut off while still on the board, and then soldered off one at a time. This is justified in the case when the microcircuit will no longer be used. If you need to save a radio component with a large number of pins, then there are two ways. The first is to use a syringe needle. Each time you heat up the solder, you should position the needle on the leg in such a way that it separates the solder from the contact. After this procedure has been completed with all contacts of the radio component, it can be removed from the board. The second option is when solder suction is used.

In this case, a structure that looks like a syringe is attached to the heated solder. After pressing the button, it sharply raises the piston, a discharge occurs and excess solder enters the suction container. That's all the secrets of how you can desolder a part from a board.

Resistor polarity

Many people are interested in how to find out the polarity of a resistor in order to determine exactly which output contact and where to insert it. In order not to mislead people, we can immediately say that the electric resistor does not and cannot have polarity. This radio element is non-polar. It is believed that resistors are non-polar and can be connected to a printed circuit board in any position of their terminals, in any combination. As with a fuse, you can check the functionality of the resistor in any combination of multimeter contacts and leads, and the order in which it is soldered to the electrical circuits does not matter. It is only important to take into account and check the nominal resistance of the element before soldering, since then in case of malfunctions it will be more difficult to do this due to the influence on the measurement of other elements and circuits of the board.

Blog about electronics

And so you decided to plunge headlong into electronics, stocked up on a soldering iron, bought solder and... What next? If worst comes to worst, everyone knows how to solder, but not many people know the subtleties of the technology and come with experience. Well, I’ll speed up this disastrous process and tell you a couple of tricks.

So, you’ve probably already read about a good soldering iron for small-scale installation, so we’ll start dancing from there. In addition to a soldering iron, you will need solder and flux. Read more about them.

Solder. This is a special alloy that melts at a temperature of about 200 degrees. The most common is 60/40 Alloy, also known as POS-61. An alloy containing 60% tin and 40% lead. Its melting point is 183-230 degrees. Typically sold as wire wound on spools. For small installations, it is better to take one with a smaller wire diameter - it is easier to dose. I have two coils, one with 0.3 mm solder wire, the second 0.6 mm. Well, I also have one and a half millimeter, but I hardly use it. Only if I massively solder massive parts that require a lot of solder. It’s better to buy imported solder; unfortunately, the Russian product pretty much sucks. There may be high-quality ones, but usually I came across low-grade slag. A coil of solder, as in the picture, should cost from 150-200 rubles, more expensive is possible, cheaper is not advisable. It’s better to spend money once, but then have beautiful and high-quality soldering and not worry about it. A reel usually lasts for a year and a half or two, which is at least. It’s also useful to buy yourself some Rose alloy. This is also a kind of solder, but its melting point is completely ridiculous - somewhere around 90-100 degrees. This alloy is sometimes useful for dismantling, but this will be discussed in a separate article later.

The simplest and most popular flux. This is ordinary purified pine resin. When soldering, first take a little solder onto the tip, then poke it into the rosin to get resin onto the tip, and then quickly solder before the resin evaporates. The method is not very convenient, so they often do it differently. Take ordinary ethyl (medicinal) alcohol and dissolve crushed rosin in it until it dissolves. Afterwards, this solution is applied with a brush to the parts to be soldered and soldered. The activity of rosin is not high, so sometimes nothing works out - the details are not tinned, but rosin has one huge advantage, which sometimes overcomes all its shortcomings. Rosin is absolutely passive. That is, it does not need to be removed from the soldering site, since it does not oxidize or reduce metals, while being an excellent dielectric. This is why I try to make the most critical solderings with alcohol-rosin flux.