Basics of electronic ...

Electrical connections of electronic systems are usually soldered (sometimes wrapping the pins with special wires is also used). 15 W, 25 W, 40 W, 100 W soldering irons with replaceable or fixed tips, or soldering guns (heating activated by a trigger switch) are used for this work. The binder is a tin alloy, most often in the form of a wire without a core or a wire with a rosin core (so-called tinol) with diameters from 0.5 to 3 mm and melting temperatures from 180 °C to 240 °C, it is advisable to use a binder with lower melting point for soldering temperature-sensitive components, such as semiconductor components. The quality of the connections increases, and the time of heating delicate elements with a soldering iron is shortened if the soldering places are well prepared, namely:

1) clean them with a razor blade, sandpaper or knife from oxides, sulphides and other impurities,

2) coat the ends of the soldered elements with tinol,

3) use only a small amount of rosin dissolved in spirit when soldering.

The time of handling the soldering iron should be as short as possible, as this reduces the risk of damaging the soldered component.

Proper soldering should proceed as follows:

1) the connected elements should be mechanically fixed, e.g. the ends of the resistors placed in the eyelets of the printed circuit, in soldering tips, on switches, in other already soldered elements - and not "in the air",

2) touch the soldering iron with one hand to the connection point, and with tinol held in the other hand touch the soldering point at the same time and hold for a few seconds,

3) after removing the tinol, remove the soldering iron after a few seconds, making sure that the tin penetrates into the gaps and that the joint is evenly covered with tin adhering to the soldered place. If the tin accumulates in a ball with a small surface adjacent to the joint, this means that the soldering area has not been thoroughly cleaned and the joint is not secure ("cold soldering"): after some time, the oxidation of the solder will open the electrical circuit.

With some practice, you can solder with one hand by scooping up some molten tinol on the tip of the soldering iron. With tweezers in the other hand, you can then hold one of the soldered elements. Semiconductor components require the use of thermal shunts during soldering: between the housing of the diode, transistor, etc. and the place of soldering, the tip of the component is pressed with tweezers.