Threading technique
The threading technique is used to wire electronic circuits ( prototypes , functional models) or to repair / rework circuit boards.
method
The connections are made using thin, enamel-insulated, but solderable and notch-resistant enamelled copper wires ("thread wire"). Commercially available rolls of 40 m each with a wire diameter of 0.15 to 0.20 mm (AWG 34); the current carrying capacity is then 100 mA, the dielectric strength 600 V DC, the resistance layer 0.86 Ohm / m. At the connection points, the thread wire is wrapped around the electrical connection (component pins), but in contrast to the winding technique , it is soldered with tin solder, in that the heat of the soldering tip melts the typically 5 µm thick insulation made of “self-fluxing” polyurethane. In addition to the high wiring density, an advantage of the method is the low height on the wiring side, which is only slightly larger than that of a printed circuit.
A breadboard with soldering pads is usually used as the basis . It is customary and advantageous to use it, in particular, when many ICs in dual-inline housings (DIL) - so-called “TTL diggers” - need to be wired and only relatively few other components are available. Another application is the wiring of the (now obsolete) core memory .
Threading pins can be used as an aid (see picture above right); The thread wire can be locked and thus tensioned by means of a slide. Further aids are a folding tool for bending IC connections and special connection pins with a press-in tool for the circuit board.
The connections are almost always made by hand according to a wiring plan. Since the wiring can become very confusing, the wires are guided over special threading combs . However, troubleshooting is very difficult with the threading technique.
In addition to the thin wire for the signal lines, several wires, thicker wire or busbars are occasionally used for the power supply and ground lines in order to avoid voltage drops. The bus system ( backplane ) of older high-performance computers was partially wired with thread technology, but mostly as a winding connection.
Today the threading technique is only used for prototypes and corrections - with small quantities, subsequent circuit changes are sometimes implemented in this way, one then speaks of "jumper wires", "strapping" or "patch wires". The basic equipment consisting of threading wire, threading comb and threading pin is available from distributors of electronics retailers as well as from senders geared towards hobbyists.
Sources of error and correction
Since it is all handmade, mistakes can easily occur. On the one hand, there is a risk that the enamel insulation of the wires will not melt during soldering, so that either no contact or an unreliable cold solder joint is created. On the other hand, if the wires are improperly routed (away from a solder pad too close to the neighboring pin), an electrical short circuit is easily possible. Incorrect connections are also a common cause of errors.
Bad soldering points can be repaired by re-soldering. In the event of a short circuit, all of the connections between the pins involved often have to be removed and rewired. The same goes for wrong connections.
If a connection has to be loosened, the wire can only be cut at one end if necessary and otherwise left in the assembly. The open wire end and the signal-carrying conductor path can lead to further problems, which is why you should remove the entire wire if possible.
Today's thread pins are made of plastic. Using the slider to lock and tension the thread wire leads to a notch at the tip relatively quickly.
Health notice
Individual manufacturers of thread wire are now issuing a warning: English When soldering through polyurethane enamelled wire a small quantity of TDI gas is produced. Use in a well ventilated room. In translation: The melting of the polyurethane insulation during soldering produces small amounts of toluene diisocyanate gas (an initial product of PU), so that sufficient ventilation / ventilation must be ensured during processing.
Web links
Individual evidence
- ↑ coated Hi-Rel electronics with visible patch wires from electricstuff.co.uk , accessed April 2, 2014.
- ↑ For example, you can get a threading pin from reichelt Elektronik or a contacting pin from Farnell (as of April 2014)
- ↑ VeroWire Datasheet (PDF) Vero Technologies website; Retrieved April 2, 2014
