Soldering operations are quite common not only in professional areas in manufacturing and construction, but also in everyday life. They are used to obtain interatomic permanent connections between small parts and elements. There are different types of soldering, differing in technological nuances, used consumables, workpieces, etc.
Technology overview
This is a joining method that uses a bonding melt (solder) with suitable characteristics for specific conditions. Both the active soldering element and the workpieces are subjected to preheating, which forms a structure of materials that is malleable for joining. The temperature regime must exceed the peak heating point, bypassing which the metal parts soften and begin to transition to a liquid state. An important characteristic of any type of soldering is the thermal exposure time under the melt. This is the interval from the start of heating to the solidification of the solder afterconnections. On average, the operation takes 5-7 minutes, but there may be deviations from this range - it depends on the characteristics of the workpiece and the area of the processed node.
Solder lamps
The most common tool for soldering various workpieces, which allows you to get high-temperature heating by burning alcohol, kerosene and other liquid fuels. In the process of operation, a flare fuse escapes from the nozzle of the device, which is subsequently directed to the target area of the melt. Such devices can be used not only for joining parts, but also for heating structures and mechanisms. Also, soldering machines are used before removing paintwork. The average heating temperature of a lamp soldering iron is 1000 - 1100 ° C, so it can also be used in welding work. The most productive models include gasoline lamps. They quickly reach optimum operating temperature and handle most standard soldering operations. The design of the devices provides for a cartridge for fuel, as well as a flame regulator that allows you to vary the power of thermal exposure.
Brazing torches
A wide range of gas soldering irons that can be connected to a fuel canister or to a central fuel source. The first supply option has the advantage of autonomy. A burner with a spray can, like a gasoline lamp, can be used regardless of external communications. When choosing such an apparatus, one should take into account the power, workingtemperature, type of gas used, ready-to-use time, etc. For example, a standard gas soldering torch runs on propane-butane and reaches a heating temperature of up to 1300°C. The period of continuous thermal exposure can reach 3 hours, but this time will also depend on the volume of the connected cartridge. Burners are also distinguished by the type of ignition system. The simplest models are switched on mechanically, and in more modern versions, piezo ignition is used.
Electric soldering irons
Also a common type of soldering equipment in the domestic environment, which is safe (compared to gas devices) and compact in size. But it is worth emphasizing the shortcomings as well. Firstly, such devices are dependent on the mains, which limits their scope. Secondly, electric soldering equipment maintains a low heating temperature in the range of 400 - 450°C. This is due to the fact that part of the energy is lost in the process of converting electricity into heat.
When choosing a device, you must take into account the maximum voltage. So, in workshops and industries, standard 220 V models are used. In domestic conditions, devices operating from 12 and 24 V transformers are often used. Tasks that can be solved with electric soldering irons are mainly limited to repairing small equipment, restoring microcircuit contacts, connecting plastic parts, etc.
Soldering stations
For batch or in-line soldering operationsusing multifunctional equipment. The soldering station is characterized by a wide range of adjustment options for operating parameters, as well as higher heating temperatures. Suffice it to say that devices of this type operate at a power of 750 - 1000 W, connected to networks with a voltage of 220 V. As a rule, these are professional soldering equipment, but there are also household counterparts. For example, devices for group operations at home may include several interchangeable tips of different sizes, stands, desolderers, wire cutters, and other auxiliary accessories. Now it's worth getting acquainted with different technological approaches to soldering processes.
Main types of soldering
There are techniques for performing operations on the joint and the gap. So, if the gap between the connected elements is less than 0.5 mm, then the soldering will be with a gap. Exceeding this interval means that the connection is made end-to-end. Moreover, the joints can have different configurations - for example, X- and V-shaped. Gap soldering is performed only with liquid solder, which is sent to the intermediate zone during operation. Standard types of butt soldering involve filling free space with solder under the influence of gravity.
Classification of soldering by temperature conditions
Today, soft, hard and high-temperature soldering is used, which is used mainly in manufacturing and construction. The first two techniques are in many ways similar - for example, in both cases, the workingthe temperature is 450°C and below. For comparison, high-temperature connections are made in the mode of at least 600°C, and more often - above 900°C.
At the same time, low-temperature processing can provide a quality connection. The most advantageous will be the use of hard solder, due to which high strength and refractoriness of parts are achieved. Adding copper to the gap or joint will also increase the ductility of the workpiece. If it is required to obtain a flexible and elastic structure, then soft soldering is used.
Classification of solders
It is conditionally possible to divide modern solders into two groups:
- Melting at low temperatures.
- Melting at high temperatures.
As already noted, low temperature soldering is performed at 450°C and below. The solder itself for this kind of operation should already soften at 300°C. Such materials include a wide group of tin alloys with the addition of zinc, lead and cadmium.
High temperature melt media are used for soldering at temperatures around 500°C. These are mainly copper compounds, which also include nickel, phosphorus and zinc. It is important to note that, for example, tin-lead-cadmium solder, in addition to a lower melting point, will differ from copper alloys in mechanical strength. The ratio of resistance to physical pressure can be represented as follows: 20 - 100 MPa versus 100 - 500 MPa.
Types of fluxes
When exposed to heat on the surface of a metal workpiecean oxide coating is formed, which prevents the formation of a quality connection with the solder. Various types of soldering fluxes are used to eliminate such obstacles, some of which also eliminate traces of rust and scale.
Fluxes can be classified just by compatibility with solders (hard and soft) or by temperature resistance. For example, for soft soldering of heavy metals, products marked F-SW11 and F-SW32 are used. For solid connection of heavy alloys, soldering fluxes of the F-SH1 and F-SH4 types are used. Light metals like aluminum are recommended to be pre-treated with compounds of groups F-LH1 and F-LH2.
Induction brazing method
This soldering technology has several advantages over the classic hot melt joining method. Among them, one can single out the minimum degree of oxidation of the workpiece, which in some cases eliminates the need to use fluxes, as well as a low warping effect. As for the target materials, they include both soft and hard alloys, as well as ceramics with plastics. For example, the optimal solder for copper in this case will be marked L-SN (modifications SB5 or AG5). As a source of thermal energy during induction exposure, both hand-held lamp devices and machine units of the appropriate power can act. In production, generator sets are also used when it is necessary to obtain a long-term soldering of large-area nodes. Also, a multi-place inductor is included in the work, which canreceive workpieces one by one. This technology, in particular, is used to make hand cutting tools.
Ultrasonic soldering
Another modern high-tech soldering method, the development of which was caused by the need to eliminate a number of characteristic shortcomings of electrochemical connection methods. A key feature of this technique is the ability to replace conventional flux as a means of eliminating oxides. The stripping function is performed by the energy of ultrasonic waves, which causes the process of cavitation in the liquid solder. At the same time, the tasks of thermal binding action from the melt are fully preserved.
The technology is also superior in terms of connection speed. If we compare ultrasonic radiation with the effect that tin-lead solder gives, then the intensity of the collapse of the cavities of the processed node will be several times higher. Observations show that ultrasonic waves with a frequency of 22.8 kHz provide a solder closing speed of 0.2 m/s.
There are also economic advantages of this method. They are also associated with a change in approaches to the use of fluxes and solders. In the production of electrical devices, when assembling monolithic capacitors, current converters and other devices, metallization with palladium, silver and platinum pastes is widely used. The process of ultrasonic soldering allows you to replace precious metals with cheaper counterparts without losing the performance of the future product.
Features of soldering-welding
Soldering as such has many similarities with traditional welding technologies. Also used is the heating of the workpieces and third-party material that affects the formation of the seam. But, compared to welding techniques, brazing does not provide for an internal melt of the workpiece structure. The edges of the parts, as a rule, remain solid, although they are heated. And yet, a complete melt of the workpiece gives a stronger connection. Another thing is that to achieve such a result, more powerful equipment may be required. When using liquid solder for copper, non-capillary soldering with dense filling of the seam is quite feasible. This connection method is partly related to welding, since it increases the adhesion of the structures of two or more workpieces. Non-capillary soldering is recommended with electric arc machines or an oxy-acetylene torch.
Conclusion
Getting a quality joint during the soldering process is influenced not only by the right choice of technology, solder with flux and equipment. Often, small organizational procedures related to the preparation of materials and subsequent processing are of decisive importance. In particular, the use of hard solder requires multi-stage cleaning of the target surface using abrasive grinding and chemical attack with carbon tetrachloride. The finished part should be clean, smooth and as level as possible. Directly during the soldering, it is also recommended to pay special attention to the method of fixing the workpieces. Desirablefasten them in a clamping tool, but in such a way that the latter is protected from chemical and thermal attack.
Do not forget about safety. Active consumables - flux and solder - require special care. For the most part, these are chemically unsafe elements that, under high temperature exposure, can release toxic substances. Therefore, at a minimum, skin and respiratory protection should be protected during work.
