Slide 1: Hello! My presentation on the topic "Types of connections in electrical engineering".

Slide 2: Soldering (Definition)

Soldering, or soldering, is a method of connecting elements using a liquid alloy of different metals. When the molten metal cools down, the connection becomes strong and transmits current. Soldering connects parts made of aluminum, copper and any ferrous, non-ferrous and precious metals.

Soldering algorithm:

1. Preheating the soldering iron to operating temperature

2. Heating of soldered metals (with a soldering iron or on special stands)

3. Applying flux to soldered metal surfaces

4. Applying solder to the soldering iron tip

5. Tinning of soldered surfaces

6. Applying solder to the soldering iron tip

7. Soldering — transfer of solder from the soldering tip to the soldered surfaces.

8. Cooling of soldered surfaces

9. Flushing of flux residues from soldered surfaces (if necessary)

If the soldered surfaces do not weigh much, you can combine steps 2 and 5 in time.

3 slide (Solder)

Solder is a special metal alloy. It penetrates in liquid form between the surfaces of soldered metals. After cooling, the solder creates strong connections — mechanical and electrical.

It is usually an alloy of tin and lead. Their different ratios affect the melting point of the solder. Both low-temperature and high-temperature solders are available.

In electrical engineering, the most popular solder is POS 60 — tin-lead solder with a content of 60% tin. For convenience, it is available in the form of a tube filled with flux.

The diameter of the solder is directly related to the size of the soldering iron tip used — the larger the tip, the thicker the solder tube is needed.

Types of solder:

Soft Up to 300 16-100 tin-lead, tin-lead-cadmium, tin-zinc, antimony, lead-free (Sn+Cu+Ag+Bi+etc.). Hard Over 300 100-500 copper-zinc, copper-nickel, copper-phosphorous, silver. Solders are usually divided into two groups: soft; hard. Soft solders include solders with a melting point of up to 300 °C, and hard ones — over 300 °C. In addition, solders vary significantly in mechanical strength.

4 slide(Flux)

The main purpose of the flux is to remove the oxide film from the surface of soldered metals. The flux also reduces the surface tension of the liquid solder, improving spreading over the soldered surfaces. This increases the strength of the joint.

The most common flux is rosin.

Rosin is perfectly soluble in alcohol. It is also sold in a liquid state.

A mixture of rosin with stearin or technical vaseline resembles a thick ointment in consistency. Hence its name — soldering fat.

There are fluxes based on synthetic resins, as well as organic fluxes based on organic acids and solvents.

Fluxes are divided into:

1. Neutral;

2. active;

3. Highly active.

Although rosin consists of 75-95% resin acids, it belongs to neutral fluxes. Its acids remove the oxide film only when the temperature rises. Upon cooling, the remnants of unused rosin return to their original amorphous state. They are harmless to solder joints. Therefore, the remnants of neutral fluxes on a rosin basis can not be washed off.

The addition of strong activators transforms neutral fluxes into active and highly active ones. They quickly remove the aged oxide film on the metal. But after working with them, it is important to remove the flux residues — over time they can destroy the solder joint.

Slide 5 (Tinning).

Tinning is the removal of an oxide film from the surface of soldered metals and coating them with a thin layer of molten solder. Under the influence of flux, the oxide film on the metal surface is replaced by molten solder molecules

There is a strong bond between solder and metal at the molecular level. It prevents the formation of a new oxide film. When soldering, the molecules of the applied solder are securely connected to their "native" molecules on the tinned surface.

Here is an example of tinning a wire with an aged oxide film with various fluxes.

To tin the wire with neutral flux, the wire must be thoroughly cleaned. When using an active flux, such cleaning is no longer required. We dip the cleaned wire with a hot soldering iron into rosin, and apply active soldering fat to the uncleaned one.

The result of tinning is almost the same.

Slide 6 (Soldering tools).

The main soldering tool is a soldering iron. It is needed to heat soldered metals and transfer molten solder to them. Most of the soldering irons are electric.

A soldering iron with a power of 10-20 watts is suitable for working with microchips. For soldering larger radio components and thin wires, the soldering iron power of 30-40 watts is sufficient. Soldering thick wires and large parts requires a soldering iron with a power of 60 watts

The more solder there is on the soldering iron tip, the more it will drain to the soldering site. The amount of solder captured by the soldering iron sting depends on the area of its tip. Hence such a variety of shapes and sizes of the soldering iron tip. A wide tip is excellent for soldering thick wires, and a tip with a thin pointed tip is suitable for small contacts on a printed circuit board.

There are also gas soldering irons. They are heated by the combustion of gas, and refueled from a household gas canister. Such models are compact and versatile. With a conical nozzle, this is an ordinary soldering iron, without a tip, a small soldering hair dryer with a flame temperature of up to 400 °C.

The soldering iron stand will keep the desktop from drops of molten solder.

The board holder securely fixes the board when soldering small parts. It is also convenient to solder wires with it.

Soldering iron stands are often equipped with a sponge to clean the soldering iron tip from carbon deposits.

Slide 7 (Soldering parts, removing solder.)

When repairing equipment, it is often necessary to remove an unusable component. Then it is necessary to clean the contact pad for soldering a new part.

The tin pump copes with this task. This tool is used when removing parts from printed circuit boards. To bring it into working position, you need to press the piston rod.

Many people like the solder removal tape — it is woven from thin copper wire and impregnated with flux. The tape is applied to the place to be cleaned from solder and warmed up with a soldering iron. The braid works like a pump, absorbing the flowing solder and cleaning the contact pad.

8 Slide(Terminal block).

One of the simplest and most reliable wire connections is through terminal blocks. They come in several types, but a screw connection is used almost everywhere. There are sockets of different sizes – for different sizes of conductors, with different numbers of pairs — from 2 to 20 and more.

The terminal block itself is a plastic housing in which a metal socket or plate is soldered. A bare conductor is inserted into this socket or between the plates, clamped with a screw. After the screw is tightened, it is necessary to pull the conductor well to make sure that it is well clamped. Due to the fact that the connection points remain uninsulated, the area of application of terminal blocks is rooms with normal humidity.

The disadvantage of such a compound: due to the plasticity of metals - especially aluminum – over time, the contact weakens, which can lead to an increase in the degree of heating and accelerated oxidation, and this again leads to a decrease in contact. In general, periodically the connection of the wires in the screw terminal boxes must be tightened.

Advantages – speed, simplicity, low cost, does not require any skills, except the ability to use a screwdriver. Another important advantage is that you can easily connect wires of different diameters, single–core and multi-core, copper and aluminum. There is no direct contact, therefore there are no risks.

Slide 9 (Wire connection by crimping).

For crimping wires, a special aluminum or copper sleeve is required – it is selected based on the size of the twist (beam diameter), and the material is taken the same as that of the conductors. Bare and polished wires are twisted, a tube sleeve is put on them, which is clamped with special pliers.

Both casings and tongs come in different types, there are several types. Each of them has its own rules of use, which you need to navigate. It is necessary to pack the wires according to certain rules, measure the size of the resulting harness, and adjust it to the requirements. In general, it's a pretty dreary task. Therefore, this type of wire connection is mainly used by professional electricians, and more and more often they switch to spring clamps.

The connection of the wires by crimping consists in compressing the connecting sleeve (aluminum or copper tube) into which the wires are inserted with special press clamps. The wires are pre-stripped of insulation for the length of the sleeve, then we place the wires inside the sleeve and compress it for reliability in two or three places. If the sleeve is much larger than the wires that need to be pressed, then you can fill the sleeve with additional wires.

10 Slide (Spring clips for connecting wires).

One of the most controversial ways to connect wires is using spring clamps. There are several types of them, but the most common two are wago terminal blocks and PPE caps. They differ greatly in appearance and installation method, but both designs are based on a spring that creates a strong contact with the wire.

There is a debate about this spring. Opponents of using wago say that the spring will weaken over time, the contact will become worse, the connection will begin to warm up more and more, which, again, leads to an even faster decrease in the degree of spring elasticity. After some time, the temperature may rise so much that the case (plastic) will melt, but what may happen next is known.

In defense of the use of spring clamps for connecting wires, it can be said that if they are used in accordance with manufacturers' recommendations, problems are very, very rare. Although there are many fakes of both wago and PPE, as well as a sufficient number of photos of them in molten form. But at the same time, many people use them, and under normal operating conditions they work for years without complaints.

The appearance and design of the cap clamp, where:

1 is a movable spring made of wire with sharp edges;

2 – knurling or "lugs" for easy screwing in;

3 – connected wires;

4 – insulating skirt;

5 – the body of the cap is made of insulating material.

Slide 11 (Wago terminals).

There is a metal plate inside these devices that ensures proper contact. The shape of the plate and its parameters were developed and tested specifically. The tests were carried out on a vibration stand for many hours, then heated and cooled. After that, the electrical parameters of the connection were checked. All tests were passed perfectly and branded products always show themselves perfectly.

In general, the product range of Wago is very wide, but for the installation of electrical wiring or connection of household appliances, lighting fixtures, two versions of wire clamps are used: series 222 (detachable) with the ability to reconnect or change the connection and series 773 and 273 – which are called non-removable.

Spring clamps for electrical wiring of the Wago 222 series have a certain number of contact pads – from two to five – and the same number of locking flags. Before starting the connection, the flags are raised and insulated conductors are inserted into them (all the way), after which the flag is lowered.

There is another type of clamp that does not provide for the possibility to redo the connection of wires – series 773 and 273. When using these terminals, the operation is generally momentary: the stripped wire is inserted into the appropriate socket. The spring there clamps it, providing contact with the plate.

These spring–loaded wire clamps can be used to connect single-core aluminum or copper wires with a cross-sectional area from 0.75 mm2 to 2.5 mm2, multi-core with rigid wires - from 1.5 mm2 to 2.5 mm2. Soft stranded conductors cannot be connected using such connectors.