his article deals with electronics manufacturing and prototyping techniques, see Wire wrap jewellery for the jewellery related topic Close-up of a wire-wrap connection. Manual wire wrapping/stripping tool and wire in various colours. Wire stripper for AWG 30 Electrical wire wrap tool. Manual tool to open a wire wrap connection. Wrapped Z80 computer backplane 1977 Wrapped backplane (close-up) Wire wrap is a technology used to securely attach to points for electrical or data contact. Wire wrap is used in several industries. In the circuit board manufacturing or prototyping it is method of constructing circuit boards without having to have a printed circuit board manufactured. It can be made by hand or by machine, and can be hand-modified afterwards. It was popular for large-scale manufacturing in the 60s and early 70s, and continued to be used for short runs and prototypes until quite recently. Wire wrap construction can produce assemblies which are more reliable than printed circuits — connections are less prone to fail due to vibration or physical stresses on the base board, and the lack of solder precludes corrosion, dry joints, etc. The connections themselves are firmer and possibly have lower electrical resistance due to cold welding of the wire to the terminal post at the corners. Wire wrap construction became popular around 1960 in circuit board manufacturing, and use has now sharply declined. Surface-mount technology and the increase in electronic switching speed have made the technique much less useful than in previous decades. Solderless breadboards and the decreasing cost of professionally made PCBs have nearly eliminated this technology. In telecommunications wire wrap is in common high volume use in modern communications networks for cross connects between copper wiring plant. For example, most phone lines from the outside plant go to wire wrap panels in a central office, whether used for POTS phone service, DSL or T1 lines. Typically at a main distribution frame Internal Cross Facilities Assingments and External Cross Facilities Assigments, are connected together via jumpers that are wire wrapped. Wire wrap is popular in telecommunications since it is one of the most secure ways to attach wires, and provides excellent and consistent data layer contact. Wirewrap panels are rated for high quality data services, including Category 5 grade wiring. The principal competitor in this application is punch blocks, which are quicker but less secure. Contents [hide] 1 Overview 2 Manual Wire Wrap 3 Semiautomated Wire Wrap 4 Automated Wire Wrapping 5 Use of Electronic Design Automation 6 See also 7 External links  Overview The electronic parts sometimes plug into sockets. The sockets are attached with cyanoacrylate (or silicone adhesive) to thin plates of glass-fiber-reinforced epoxy. The sockets have square posts. The usual posts are 0.025 inches (635 micrometres) square, 1 inch (25.4 mm) high, and spaced at 0.1 inch (2.54 mm) intervals. Premium posts are hard-drawn beryllium-copper alloy plated with a 0.000025 inches (25 microinches) (635 nanometres) of gold to prevent corrosion. Less-expensive posts are bronze with tin plating. The two holes at the end of a manual wire wrap tool. The wire goes in the one near the edge, and the post is inserted into the hole in the center. 30 gauge silver-plated soft copper wire is insulated with a fluorocarbon that does not emit dangerous gases when heated. The most common insulation is "kynar". The 30 AWG Kynar is cut into standard lengths, then one inch of insulation is removed on each end. A "wire wrap tool" has two holes. The wire and one quarter inch (6.35 mm) of insulated wire are placed in a hole near the edge of the tool. The hole in the center of the tool is placed over the post. The tool is rapidly twisted. The result is that 1.5 to 2 turns of insulated wire are wrapped around the post, and atop that, 7 to 9 turns of bare wire are wrapped around the post. The post has room for three such connections, although usually only one or two are needed. This permits manual wire-wrapping to be used for repairs. The turn and a half of insulated wire helps prevent wire fatigue where it meets the post. Above the turn of insulated wire, the bare wire wraps around the post. The corners of the post bite in with pressures of tons per square inch (MPa). This forces all the gases out of the area between the wire's silver plate and the post's gold or tin corners. Further, with 28 such connections (seven turns on a four-cornered post), a very reliable connection exists between the wire and the post. Furthermore, the corners of the posts are quite "sharp". There are three ways of placing wires on a board.  Manual Wire Wrap Typical wire wrap construction of Bell System telephone crossbar switch. Note some types of connection were soldered. A manual wire wrap tool resembles a small pen. It is convenient for minor repairs. Wire wrap is one of the most repairable systems for assembling electronics. Posts can be rewrapped up to ten times without appreciable wear, provided that new wire is used each time. Slightly larger jobs are done with a manual "wire wrap gun" having a geared and spring loaded squeeze grip to spin the bit rapidly. Such tools were used in large numbers in American telephone exchanges in the last third of the 20th century, usually with a bigger bit to handle 22 or 24 AWG wire rather than the smaller 28 or 30 AWG used in circuit boards and backplanes. The larger posts can be rewrapped hundreds of times. They persisted into the 21st century in distribution frames where insulation-displacement connectors had not taken over entirely. Larger, hand held, high speed electric guns were used for permanent wiring, when installing exchange equipment between the late 1960s when they replaced soldering, and the middle 1980s when they were gradually replaced by connectorized cables. BASIC SOLDERING PROCEDURE Step 1 Check that your soldering iron tip is suitable for the Project. (no larger than the diameter of the pad). Check the tip is clean and shiny. If not, tin it by adding a small amount of solder to the tip. Step 2 Adjust the temperature of the soldering station to 3500 C (degrees Celsius ) Step 3 Ensure the solder sponge is damp. A dry sponge will not clean the tip effectively, and one that is too wet will lower the temperature of the tip making for an ineffective solder joint. Step 4 Carefully wipe the tip on the damp sponge until clean. Continually wipe the tip while soldering a circuit board. Step 5 Bend the lead of the component using fine pliers so that it easily slides into the holes of the printed circuit pad. Step 5 Insert the component to be soldered into the circuit board and bend the leads protruding from the bottom of the circuit board at an angle of approx 450. Step 6 Cut the leads of the component close to the outer edge of the solder pad. Step 7 When ready, hold the soldering iron at a 45 angle, and heat both the lead and the pad simultaneously. Touch the solder wire in the space between the iron tip and the lead. Step 7 Keep the soldering iron tip still while moving the solder around the joint as it melts. Step 8 Remove the solder tip first and the solder wire next, (prevents spiking). Step 9 Allow to the joint to cool naturally and undisturbed, do not blow on the solder joint to cool it. Step 10 When you have completed all solder joints thoroughly clean your board, using Isopropyl Alcohol, and a bristle brush, to remove the flux residue and other contaminants. Step 11 Wipe or pat dry with a lint free tissue to remove traces of residue. Step 12 Inspect for a good solder connection. The solder joint should be clean, smooth and shiny. The solder fillet should be concave in shape, feathering out smoothly to the edge of the pad. In the diagram below figure b) is the ideal solder joint. Figure a) the amount of solder applied is minimal and may result in a poor electrical connection over time. Figure c) indicates an excessive amount of solder has been applied to the connection. This may damage the solder pad due to excessive heat applied. Step 13 Leave a large blob of solder on the tip when switching the iron off as this will protect the tip from oxidation and contamination.
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