Wiring pencil

The threading technique is used for wiring of electronic circuits (prototypes, functional model ) or for repair / rework of printed circuit boards.

Method

The connections are made through thin, enamelled, but durchlötbare and notch- resistant enamelled copper wires ( " braided wire "). Commercially available are rolls of 40 m with a wire diameter of 0.15-0.20 mm (AWG 34); the current carrying capacity is then 100 mA, the dielectric strength 600 V DC, the resistance per unit length 0.86 ohm / m. At the junctions of the braided wire is wrapped around the electrical connection ( component pins), but soldered in contrast to the winding technique with solder by the typically 5 microns thick insulation from "self- fluxing " polyurethane is melted by the heat of the soldering tip. An advantage of the method is in addition to the high wiring density to the low height on the wiring side (which is only slightly larger than that of a printed circuit board ).

As a basis we used mostly a breadboard with solder pads. Common and advantageous use was particularly when many ICs in dual in-line package ( DIP ) - so-called " TTL graves " - to wire and a few other components were relatively available. Another application was the wiring of the (now obsolete ) core memory.

As an aid Fädelstifte can be used ( see figure at right ); can be locked and clamped so that the braided wire by a slide. More tools will be a folding tool for bending of IC terminals as well as special pins with push-in tool for PCB.

The connections are almost always carried out by hand for a wiring diagram. Since the wiring can be very confusing, one performs the wires through special Fädelkämme. Troubleshooting is still very difficult in the threading technique.

In addition to the thin wire for signal lines are used for the power supply and ground lines occasionally more wires, thicker wire or conductor rails in order to avoid voltage drops. The bus system ( backplane) of older high-performance computer has been partially wired with threading technique, but mostly as a winding connection.

Nowadays Fädeltechnik is only used for prototypes and corrections - in small numbers subsequent circuit changes are sometimes realized in this way, then one speaks of "Jumper Wires", " Strapping " or "patch wires ". The basic equipment of braided wire, Fädelkamm and Fädelstift is still available for both distributors of electronics retail trade as well as geared to hobbyists shippers.

Sources of error and correction

As they were all is handmade, errors can easily occur. On the one hand there is a risk that the insulation coating of the wires does not melt during the soldering process, so that either no contact or unreliable cold solder joint is formed. On the other hand, easily an electrical short circuit is in awkward leadership of the wires ( on Nachbarpin passing of a solder pad off too close ) possible. Incorrect connections are also a common source of errors.

Bad solder joints can be repaired through rework. Short circuits often all connections must be removed and the pins involved rewired. The same applies to wrong connections.

Must be a compound are dissolved, you can only undo the wire pinch at one end and otherwise left in the building. The open end of the wire and the signal-carrying conductor path can lead to further problems, so you should remove the entire wire if possible.

Today Fädelstifte are made of plastic. Use the slider for locking and clamping the Fädeldrahtes leads relatively quickly to a notch at the top.

Sanitary Notice

Individual manufacturers of Fädeldrahtes now give a warning out: English When soldering through polyurethane enamelled wire a small quantity of gas is produced TDI. Use in a well ventilated room. In translation, mutatis mutandis: By the melting of the polyurethane insulation when soldering arise small amount of toluene gas ( a starting material of PU), so pay attention to adequate ventilation / ventilation during processing.