Crimp (electrical)

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A wire and connector in a crimping tool Crimping tool 04.jpg
A wire and connector in a crimping tool

An electrical crimp is a type of solderless electrical connection which uses physical pressure to join the contacts.

Contents

Crimp connectors are typically used to terminate stranded wire. [1]

History

The technique of soldering wires has remained common for at least a century, however crimp terminals came into use in the middle of the 20th century. In 1953, AMP Incorporated (now TE Connectivity) introduced crimp barrel terminals, and in 1957 Cannon Brothers experimented with machined contacts integrating crimp barrels. [2] During the 1960s, several standards for crimp connectors were published, including MS3191-1, MS3191-4 and MIL-T-22520. In 2010, the predominant standard for crimp connectors changed to MIL-DTL-22520. [3]

Characteristics

Close-up of two ring-tongue terminals before (left) and after (right) crimping. Kabelschuh detailfoto 2.jpg
Close-up of two ring-tongue terminals before (left) and after (right) crimping.

The benefits of crimping over soldering and wire wrapping include:

Crimping is normally performed by first inserting the terminal into the crimp tool. The terminal must be placed into the appropriately sized crimp barrel. The wire is then inserted into the terminal with the end of the wire flush with the exit of the terminal to maximize cross-sectional contact. Finally, the handles of the crimp tool are used to compress and reshape the terminal until it is cold-welded onto the wire. [6]

The resulting connection may appear loose at the edges of the terminal, but this is desirable so as to not have sharp edges that could cut the outer strands of the wire. If executed properly, the middle of the crimp will be swaged or cold-formed.

More specialized crimp connectors are also used, for example as signal connectors on coaxial cables in applications at high radio frequencies (VHF, UHF) (see below). These often require specialised crimping tools to form the proper crimp. [7]

Crimped contacts are permanent (i.e. the connectors and wire ends cannot be reused). [8]

Theory

Crimp-on connectors are attached by inserting the stripped end of a stranded wire into a portion of the connector, which is then mechanically deformed by compressing (crimping) it tightly around the wire. [9] The crimping is usually accomplished with special crimping tool such as crimping pliers. A key idea behind crimped connectors is that the finished connection should be gas-tight.

Effective crimp connections deform the metal of the connector past its yield point so that the compressed wire causes tension in the surrounding connector, and these forces counter each other to create a high degree of static friction which holds the cable in place. Due to the elastic nature of the metal in crimped connections, they are highly resistant to vibration and thermal shock. [10]

Two main classes of wire crimps exist: [11]

In addition to their shape, crimped connectors can also be characterized by their insulation (insulated or non-insulated), and whether they crimp onto the conductor(s) of a wire (wire crimp) or its insulation (insulation crimp). [12]

Shapes

Applications

Blade connectors (bottom), ring and spade connectors (top), and bullet connectors (right) Kabelschuh verschiedene commons.jpg
Blade connectors (bottom), ring and spade connectors (top), and bullet connectors (right)

Crimped connections are common alternatives to soldered connections. There are complex considerations for determining which method is appropriate –crimp connections are sometimes preferred for these reasons:

Crimped connectors fulfill numerous uses, including termination of wires to screw terminals, blade terminals, ring/spade terminals, wire splices, or various combinations of these. A tube-shaped connector with two crimps for splicing wires in-line is called a butt splice connector.

Single-wire crimp terminals include:

Crimping is also a common technique to join wires to a multipin connector, such as in Molex connectors or modular connectors.

Crimp plug-and-socket connectors can be classified as rear release or front release, referring to the side of the connector where the pins are anchored: [19]

Crimp connections are used typically to fix connectors, such as BNC connectors, to coaxial cables [20] quickly, as an alternative to soldered connections. Typically the male connector is crimp-fitted to a cable, and the female attached, often using soldered connections, to a panel on equipment. A special power or manual tool [21] is used to fit the connector. Wire strippers which strip outer jacket, shield braid, and inner insulation to the correct lengths in one operation [22] are used to prepare the cable for crimping.

Quality

A crimped connection will only be reliable if a number of criteria are met:

Micrographs of the crimped connections can be prepared to illustrate good and bad crimps for training and quality assurance purposes. The assembled connection is cut in cross-section, polished and washed in nitric acid to dissolve any copper dust that may be filling voids leading to a false indication of a good crimp.

Tools

A wide variety of crimping tools exist, and they are generally designed for a specific type and size of terminal. Handheld tools (sometimes called crimping pliers) are most common, which may be ratcheting. Apart from Handheld Tools, Crimping Tools can also include sophisticated electrically powered hydraulic types and battery operated tools that cover the entire size range and type of conductors, designed for mass production operations. [6]

Terminal insulation colors

Standard FASTON terminal colors [26]
Insulation colorWire gauge (AWG)Comments
Yellow26–22
Transparent24–20
Red22–18
Blue16–14
Yellow/Black16–14Heavy duty
Yellow12–10
Red8
Blue6
Yellow4
Red2
Blue1/0
Yellow2/0
Red3/0
Blue4/0

See also

Related Research Articles

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References

  1. ↑ Mazda, F. F. (2013-10-22). Electronics Engineer's Reference Book. Butterworth-Heinemann. ISBN   9781483161068. Archived from the original on 2018-01-22.
  2. ↑ "Crimping Facts". Archived from the original on 13 May 2015. Retrieved 11 July 2015.
  3. ↑ "MIL-DTL-22520: Crimping Tools, Wire Termination, General Specification for". Archived from the original on 1 December 2017. Retrieved 11 July 2015.
  4. ↑ "Jameco Catalog". jameco.com. Archived from the original on 22 March 2018. Retrieved 21 March 2018.
  5. 1 2 3 "Crimped Joints". Archived from the original on 2018-01-22.
  6. 1 2 3 Quality Crimping Handbook (PDF). Molex Application Tooling Group. 1996. Archived (PDF) from the original on 2021-08-18. Retrieved 2023-11-16.
  7. ↑ "Crimping Tool For N Type Coaxial Cable Connectors". maunindustries.com. Archived from the original on 30 August 2023. Retrieved 30 August 2023.
  8. ↑ "Crimp vs. Solder" (PDF). Aviel Electronics Catalog. 2013. Archived (PDF) from the original on 26 February 2020. Retrieved 1 July 2019.
  9. ↑ Elliott, Brian (2007). Electromechanical devices & components illustrated sourcebook . McGraw-Hill. pp.  151. ISBN   978-0-07-147752-9.
  10. ↑ "Crimp vs Solder: Pros and Cons". RF Connectors. 1 December 2004. Archived from the original on 1 July 2019. Retrieved 7 July 2019.
  11. ↑ XJ4Ever; Schmuckatelli Heavy Industries. "You're, like, crimping my style, man" (PDF). Archived (PDF) from the original on 21 December 2018. Retrieved 7 July 2019.{{cite web}}: CS1 maint: numeric names: authors list (link)
  12. ↑ "Crimp Quality Guidelines" (PDF). TE Connectivity Application Tooling. May 2011. Archived from the original (PDF) on 2 July 2013. Retrieved 7 July 2019.
  13. 1 2 "Electronic Installation Practices Manual". NAVSHIPS 900171 (U.S. Navy). 23 May 1952. Archived from the original on 13 July 2015. Retrieved 12 July 2015.
  14. 1 2 "2.8 mm Apex Terminal Crimp Guidelines" (PDF). Archived from the original (PDF) on 14 July 2015. Retrieved 12 July 2015.
  15. 1 2 3 4 5 6 7 8 9 "Crimp symbols". Archived from the original on 2015-07-12.
  16. 1 2 3 4 "Forms of Crimping". Archived from the original on 2017-11-17.
  17. 1 2 3 4 "Ferrules: Your Best Insurance Against Costly Connection Failure" (PDF). Archived (PDF) from the original on 2017-12-01.
  18. ↑ "Electrical Terminals - Pin and Receptacle Type". Archived from the original on 12 July 2015. Retrieved 11 July 2015.
  19. ↑ Worley, Jon (31 July 2018). "Circular Connector Terminology Guide". NYK Component Solutions. Archived from the original on 26 June 2019. Retrieved 7 July 2019.
  20. ↑ Typical crimp BNC connector [ permanent dead link ]
  21. ↑ "Typical manual crimp tool for fitting BNC and other coaxial connectors to cables" (PDF). Archived from the original (PDF) on October 29, 2014.
  22. ↑ "Typical coax one-operation stripper" (PDF). Archived from the original (PDF) on October 29, 2014.
  23. ↑ "Cross Sectioning". Archived from the original on 2017-06-20.
  24. ↑ "Tensile Test". Archived from the original on 2017-12-01.
  25. ↑ "Wire Harness Manufacturing Terms, Tools, and Tips of the Trade". Archived from the original on 2023-11-15. Retrieved 2023-11-16.
  26. ↑ "AMP Standard Terminals and Splices" (PDF). Archived (PDF) from the original on 2015-07-13.
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