Miniature soldering iron

We bring to your attention two miniature soldering irons, the most affordable in manufacturing and satisfying the requirements for the installation of miniature electronic products.

The first design, shown in Figure 1, is intended for mounting transistors and microcircuits on printed circuit boards. The power of the soldering iron is about 7 watts. Supply voltage 6.3 V.

The design of the soldering iron is traditional. A copper tube is attached to a handle made of insulating material, into which the sting is pressed. 2-3 layers of fiberglass are wound on a copper tube, along which a heating spiral is wound. Outside, the spiral is insulated with asbestos thread. The entire heating element is closed with a metal cap from a multi-rod ballpoint pen. The assembly of the soldering iron is made in this sequence. The tube is heated with a powerful soldering iron and pressed onto the shank of the steel base. For greater reliability, drill a hole with a diameter of 0.8-1 mm in the place of attachment to the tube and rivet a piece of steel wire or nail in it. Two layers of fiberglass with a width of 40 mm and a nichrome spiral are wound on the tube. The spiral is a nichrome wire with a diameter of 0.35 mm (electric iron spiral) with a total resistance of 5-5.6 Ohms. The beginning and end of the winding is twisted with intermediate lengths of 100 mm long copper wire with a diameter of 0.6 mm. The beginning of the winding is fixed on the tube as close as possible to the sting and a nichrome wire is wound with a pitch of 0.3 mm. Then a thin asbestos cord is wound around the heater.

The washer is screwed to the handle and a power cord twisted from three insulated flexible conductors is passed through the hole in the handle and the washer. They are passed through three holes in the base and screwed to the washer by installing three bushings. The insulation at the passage through the holes in the base should be further strengthened with two to three layers of fiberglass. One of the wires with a brace of bare copper wire is attached to the shank of the base, this conductor is used to ground the tip of the soldering iron during operation. The remaining two are designed to connect the heater to a current source. A protective cover is put on the heater and fixed with a stopper made of a spring wire.

The transformer for powering the soldering iron must have good inter-winding insulation. The secondary current is about 1 A.

A feature of the second design (Fig. 2) is the device of the heater, it is made of graphite and screwed directly onto the tip of the soldering iron. The design of the soldering iron is very simple. The sting is made of a copper rod with a diameter of 5 mm and a M5 thread is cut into it. Screw the nut onto the thread until it stops and put on a metal washer (Fig. 4). Then put on a mica pad with a thickness of about 0.5 mm and carefully screw the heater.