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6

Low-Power Commercial, Automotive, and Appliance Connections

Anthony Lee and George Drew

They weighed me, dust by dust— They balanced film by film

Emily Dickinson
CoNTENTS

6.1 Introduction........................................................................................................................ 376 6.2 Connectors..........................................................................................................................377
6.2.1 Functional Requirements .....................................................................................377 6.2.2 Types of Connectors .............................................................................................. 378 6.2.3 Mechanical Considerations.................................................................................. 381
6.3 Contact Terminals..............................................................................................................384
6.3.1 Contact Physics ......................................................................................................384 6.3.2 Terminal Types ......................................................................................................384 6.3.3 Other Electrical Contact Parameters...................................................................392
6.4 Degradation of Connector Contact ................................................................................. 393
6.4.1 Surface Films .......................................................................................................... 393 6.4.2 Fretting Corrosion of Tin-plated Contacts .........................................................396 6.4.3 Examples of Contact Failures...............................................................................402
6.4.3.1 Automotive Position Sensor Connector...............................................402 6.4.3.2 Fuel Injector Connector..........................................................................403 6.4.3.3 Glowing Contacts ...................................................................................403 6.4.3.4 Electrolytic Corrosion.............................................................................404 6.4.3.5 Incompatible Plating and Low Contact Force.....................................404
6.5 Automotive Connector Contacts .....................................................................................405
6.5.1 Vehicle Conditions.................................................................................................405 6.5.2 High Power Connectors for Electric and Hybrid Vehicles ..............................405 6.5.3 Aluminum Wiring Connections .........................................................................406 6.5.4 Connections for High-Vibration Environment .................................................408
6.6 Summay ..............................................................................................................................408 References ....................................................................................................................................409

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6.1 Introduction

Perhaps the most useful function of electrical connection systems is to serve as a convenience for assembly, installation, and servicing of an electrical device or system. For example, the internal connections in a timer control module of a dishwasher enable the assembly of such a module. In addition, the electrical connections of the harness to the motor, valves, and power sources complete the entire dishwasher assembly. Likewise, the physical installation of a component such as a motor into a clothes washer drive assembly or a radio into the dashboard of an automobile is done first, and then the electrical circuits are completed by mating the connectors or installing other required electrical connections. As each subassembly is linked, each harness is connected with other circuits and to the power source. Depending on the complexity of the entire electrical system, a variety of connectors such as in-lines, junction splices, device connectors, and headers are used. The overall system architecture of the entire “wiring harness” determines the number of points and the location where the circuits will be connected. Also, depending on the type of components in the circuits, connection systems may serve to connect low-current or low-voltage, high-frequency electronics circuits, high-current power circuits, timer and control circuits, sensor circuits, and communication signal circuits. In this chapter, we deal mainly with electrical contacts of the separable type such as the male and female terminals in connection systems. We will also briefly examine the semi-permanent type of crimp and insulation displacement connections because they are intimately related to connectors and are subject to similar physical principles. As with all electrical connection systems, the basic design of an electrical contact depends on a set of application parameters. Table 6.1 summarizes the range of circuit parameters within the scope of this chapter. The basic design and application of the connections require the consideration of
(a) The electrical devices to be connected, which define the voltage and current level, and (b) The functional, physical, electrical, mechanical, and environmental requirements of the system to determine the correct connection system to be used. For example, a connection made directly to the motor must have sufficient retention force to withstand the vibration from the motor, whereas a ribbon cable will require a different connector from a power feed line with large-gauge round cables.

TABLe 6.1

Application Parameters of Connection Systems in the Area of Low-Power Commercial, Residential, Automotive, and Appliance Circuits

  • Type
  • Circuit
  • Voltage (V)
  • Current (A)

  • Power
  • Appliance/commercial/residential 120–240 ac

Appliance/commercial/residential 120–240 ac Appliance/commercial/residential 24–36 ac
10–100

< 10 < 2 > 1

~ 300

< 1

Lighting Control

  • Power
  • Automotive

Automotive, Electric Drives Automotive Electronics
12–36 dc ~ 300 ac, dc 5–12 dc 5–12 dc

< 1

Power Control Low Power Signal

< 1 < 0.1

All

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The environment has a major impact on the design and material chosen for each type of connector housing and electrical contacts. For example, outdoor versus indoor applications can have a major implication on the design of the terminals and the material used (see Chapters 2, 3, 7, and 8). Other important parameters include the range of operating temperature, duty cycle, number of insertions, thermal cycling or shock, seal and protection, and the corrosion level of the environment. Section 6.5 will give examples of automotive connectors as applied to the challenging automotive environment. Also, the initial cost of a connection system, including the cost of assembly, may determine the type of connector used. On the other hand, the cost associated with service and maintenance of such a system could be much higher than an alternative, which has a higher initial cost. If such equipment is for an application at a remote location, the total cost of the system may dictate the connection system selected. Various industry standards and specifications have been developed, forming some common ground for both suppliers and users of connectors or connection within a given industry. For example, the American Society of Testing and Measurement (ASTM) has an extensive list of contact-related standards especially related to alloy materials, testing methodology, and recommended measurement practices. The Electronics Industries Association (EIA) also has a list of contact-related standards. Many of those standards from both EIA and ASTM have been approved as American National Standards. For appliance and consumer-related products, the connection systems are tested and listed together with the product as Underwriter’s Laboratory (UL)-approved. For household and related components, the National Electrical Code (NEC) may also apply. For automotive connectors, there are a number of applicable SAE and ISO specifications. Also, the military specifications (Mil Specs) have comprehensive connector standards for devices associated with military applications in the United States. In this chapter, Section 6.2 addresses connectors, their function, design, subcomponents, and assembly. In Section 6.3, we will focus on the electrical contact terminals of the electrical connections. The connector contact degradation mechanisms are discussed in Section 6.4. Since automotive applications have dominated the recent drastic growth in electrical and electronics systems, we shall devote a new Section 6.5 on this topic in this Second Edition.

6.2 Connectors

6.2.1 Functional requirements

Although the basic function of connectors is to provide electrical interconnections to complete the circuit, a large number of non-electrical factors determine the type of connector or connection system used. To begin with, mechanical requirements such as size, shape, mounting, and mating and unmating force and frequency need to be considered. In addition, environmental requirements such as temperature, temperature cycle, humidity, contaminants (solid, liquid, and gaseous), shock and vibration, and sealing further complicate the design and selection process. The electrical requirement often goes beyond circuit voltage and current. Many applications also require low contact resistance, terminal impedance, polarity, and appropriate insulation level. To satisfy these often competing requirements, connection technology has evolved into a sophisticated engineering

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discipline. The challenge to the connection engineers is to design the lowest-cost products that meet all requirements, which in reality often work at cross purposes.

6.2.2 Types of Connectors

There are several generic types of connectors frequently found in automotive, appliance, and commercial applications: (1) Simple terminal–terminal, (2) Rack and panel, (3) Plug and receptacle, (4) Edge-on, and (5) Compliant pin. The terminal–terminal type is the simplest and has been in use ever since the beginning of electricity. An example is illustrated in Figure 6.1, showing the simple blade-box connector. Clearly, manual connection is required for this type of connector, and essentially no insulation or enclosure is present to protect the terminals. This is acceptable when the connector is used within an enclosure such as the appliance’s housing. This connector has both sufficient contact force to provide a low contact resistance even with non-noble coatings and sufficient mechanical force to prevent the contacts from parting. The rack and panel type connector is typically for mounting of equipment where one side of the connector is on the removable part of the equipment and the other half on the stationary or fixed part. As the removable part is installed on the “rack”, the connector is mated as well. A precision guide or a floating connector is mounted to ensure alignment of contact terminal to avoid damage due to variations in position during insertion. Figure 6.2 illustrates an example of such a connector.

Figure 6.1

Example of the simple terminal–terminal type connector.

Figure 6.2

Example of the rack and panel type connector.

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The plug and receptacle type is perhaps the most widely used. This type is very flexible, especially in the assembly of complex harness or circuits such as the installation of the automotive harness to support a large number of electrical features and functions. Figure 6.3 shows an example of this type of connector. Depending on the specific application, the connector may be a part of a device with the mating part on the wiring harness. The component on the device side is known as a header or device connection. Also, such a connector is used as an in-line for joining one harness segment with another. Another application is a bulkhead feed-through. Here, the connector serves to permit the harness to terminate at some physical barrier and the circuit to continue on the other side such as at the wall socket, plug at the back of a control unit, or the feed-through at the firewall between the engine and the passenger compartments. When the number of lines is large, a plug-and-receptacle connector, which requires manual installation, can be difficult to mate. Some type of mechanical assistance in the form of lever or bolt-screw is often incorporated. Also, there are other assurance features to insure the quality of the installation including, lock, terminal position assurance (TPA), and connector position assurance (CPA). An example of this type of connector with the full complement of features is shown in Figure 6.4. Further, other requirements like shrouding, connector seal, and cable dressing to reduce mechanical and environmental stresses increase the complexity of the connector design. The edge-on type connector is mainly for board-to-board and wire-to-board connections. In the majority of applications, a part of the terminal on the edge of the printed circuit board has its metal traces exposed. The other part of the connector has

Lock
Connector enclosure

Figure 6.3

Example of the plug and receptacle type connector.

Lever lock
Connector seal
TPA

TPA

Female connector
Male connector
Male position assurance

Figure 6.4

An automotive connector of the plug and receptacle type with TPA, CPA, lock, seal, and mechanical assist lever.

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terminals and attachments to the cables. In some instances, a flexible printed circuit is used. In this case, a modified form of the edge-on connector is used as illustrated in Figure 6.5 [1,2]. Another common connection is the compliant pin connector [3,4,5]. A compliant pin consists of an electrical terminal incorporating a relatively stiff spring section which is designed to be press-fitted into a plated-through hole of a printed circuit board. Figure 6.6 shows examples of one of the most common compliant pin shapes—called the “eye of the needle”. While it has been used in electronic components for many years, compliant pin technology has only recently (from 2005) been used in high-volume automotive electronics as an alternative to solder joints. A desirable feature in the design is to have enough contact force to promote galling (cold welding) at the contact spots during insertion of the pin into

Figure 6.5

Edge-on connector for flexible printed circuits (FPC).

  • (a)
  • (b)

(c)

Figure 6.6

Compliant pin connector, (a) Typical “eye of needle” terminal design, (b) Cross-section after insertion into circuit board, and (c) Automotive compliant pin connector.

Low-Power Commercial, Automotive, and Appliance Connections

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a circuit board. This provides a very stable electrical connection with a low resistance for connections that do not have to be taken apart. On the other hand, the terminal insertion force must be low enough that the printed circuit boards, or board-mounted electronic components, are not damaged when the compliant pins are press-fitted into place [3,4]. The relatively large centerline spacing required between compliant pins can be a disadvantage compared to soldering or other termination methods. As the spacing between the plated holes decreases, the interaction of stresses around the holes can cause damage to the printed circuit board.

6.2.3 Mechanical Considerations

While the number of connector designs for different applications is large, they share several common features. Depending on the requirements and the environment the connector must service, the complexity can vary. Except for the simplest types of connectors, the essential parts of a connector are: contact terminals, line insulation, enclosure, and cable or wire termination. We will briefly discuss each of these parts.

Contact terminals: These are the conducting members and consist of two terminals, one male and another female, that pass the current when they are in the mated position. Section 6.3 covers different types of contact terminals. From the mechanical consideration, the terminals have attachment to the cable on the one end and the contact interface on the other. This interface also requires a low and stable resistance during its service life.
Line insulation: For connectors with multiple lines, electrical insulation, or isolation between adjacent lines is essential. Such insulation also serves to maintain the terminal location and alignment. As illustrated in Figure 6.3, the line insulation is a part of the plastic enclosure.
Enclosure: This is the housing for the connector where the parts of the connector are assembled. Mating is accomplished by joining the two parts of the connector enclosure together. Thus, the enclosure must provide mechanical guides for mating. Further, it also provides protection to the internal parts. For the rack and panel type connector, part of the housing is in the equipment. It can also be a header of an electronic module.
Cable termination: It forms the transition between the cable and the terminal and is often a non-separable connection. Usually, a metallic or mechanical (soldered, welded or crimped) joint serves both the electrical and mechanical connection. Although the wire–terminal interface is a permanent contact interface outside the scope of the separable contact interfaces being discussed here, it does play an important role in the assembly and performance of the terminals as a part of the connector. This interface provides the electrical and mechanical link from the terminal to the wire. Its interface resistance and contact degradation can lead to degradation of the separable contact interface at the male or female terminal. A brief discussion on the crimp termination will be presented in Section 6.3.2.

An insulation displacement connection (IDC) is also used as a method for attaching the cable to the terminal. As shown in Figure 6.7, the cable is fed into an IDC slot. During insertion, insulation to the cable is cut, the slot is forced to expand, and an electrical contact with

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Insertion tool

Figure 6.7

Insulation displacement connection (IDC) before and after cable insertion.

a. Connector seal b. Terminal engage c. Inertia lock d. Connector engage
(composite)
(d)

(c)
(b)

(a)

Position

Figure 6.8

Connector engagement force characteristics.

the wire is made. Examples of such a termination method were reported in the literature [6–8]. The inherent advantage of IDC connection is the consistent contact force between the wire and the IDC slot. Also, such termination process is attractive for automation because the cables going to the same connector can be terminated simultaneously. On the other hand, crimping and soldering are done individually. Other connector features illustrated in Figure 6.4 include connector seals. For connectors exposed to the elements, seals effectively prevent the intrusion of liquid, gas, and particulates into the contact terminal areas. Liquid contaminants are a major cause of contact corrosion and loss of electrical insulation between lines; dust and particulates can often lead to high-resistance contacts (see Chapters 2 and 4). Sealing against gaseous contaminants is much more difficult. However, the seals do drastically reduce the diffusion of corrosive gaseous pollutants into the terminal contact areas and greatly increase the service life of terminals. Some seal designs must also handle situations when a pressure difference exists between the inside and the outside of the connector such as during temperature cycling or submersion under water. For manual connector engagement, one can capture the mating force as shown in Figure 6.8. This force–displacement characteristic reflects events occurring during the mating process. For manual mating, the peak force must be sufficiently low to be acceptable

Low-Power Commercial, Automotive, and Appliance Connections

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to the operator. Equally important is the work performed or the area under the force– displacement curve. From an operator’s point of view, the connector engagement needs to relate to an “effort” of mating. The “effort” is comprised of not only the peak force and the work of mating, but also the ergonomic environment such as the reach and orientation of the mating, size and shape of the connector, visibility of the parts, and the posture of the operator. The quantification of the “effort” of mating a connector is certainly not an exact science and often subjective. However, the design must incorporate features that result in a connector that is “easy” for the operator to put together. When the number of contacts in the connector is in the tens, especially when seals are used, a mechanical assist engagement may be required. Such a feature may take the form of a lever as shown in Figure 6.4. Some connector designs even go all the way to a zero-insertion-force (ZIF) concept [9,10]. The basic principle used is that during connector mating, the frictional force is nearly zero, and a subsequent clamping action presses the contacts together. Most ZIF concepts basically separate the insertion action from the application of the normal force. Another feature is the connector lock. The holding force of a connector is often not suffi- cient to maintain the engagement for the service life. This is especially true for applications, where the connector experiences frequent movement or is under a vibratory environment. A case in point is the connector attached to the engine of a motor vehicle. A positive locking mechanism is essential to ensure engagement is maintained. Such a connector lock feature is shown in Figure 6.3. As an aid to the assembly and installation of the connector, terminal position assurance
(TPA), and connector position assurance (CPA) are incorporated into more sophisticated connector designs. Such features are illustrated in Figure 6.4. A common approach in TPA design is to prevent the connector from being further assembled unless all terminals are positioned correctly. Similarly, unless the connector is fully mated and locked, the CPA cannot be installed. Both TPA and CPA have greatly improved the installed quality of connection systems. A filtered connector is a specialized connector design where a low-pass L–C circuit, for example, is incorporated into its construction. An example is shown in Figure 6.9. Here, the ferrite block provides the series inductance, and an array of chip capacitors is placed between the pins and the ground. Also, a C–L–C pi filter section can be similarly implemented by adding another capacitor array. Incorporating a filter in the connector provides high-frequency isolation between the two sides of the connector. This saves valuable board space and addresses the electromagnetic compatibility of the circuit.

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  • The Elements.Pdf

    The Elements.Pdf

    A Periodic Table of the Elements at Los Alamos National Laboratory Los Alamos National Laboratory's Chemistry Division Presents Periodic Table of the Elements A Resource for Elementary, Middle School, and High School Students Click an element for more information: Group** Period 1 18 IA VIIIA 1A 8A 1 2 13 14 15 16 17 2 1 H IIA IIIA IVA VA VIAVIIA He 1.008 2A 3A 4A 5A 6A 7A 4.003 3 4 5 6 7 8 9 10 2 Li Be B C N O F Ne 6.941 9.012 10.81 12.01 14.01 16.00 19.00 20.18 11 12 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 3 Na Mg IIIB IVB VB VIB VIIB ------- VIII IB IIB Al Si P S Cl Ar 22.99 24.31 3B 4B 5B 6B 7B ------- 1B 2B 26.98 28.09 30.97 32.07 35.45 39.95 ------- 8 ------- 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 4 K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr 39.10 40.08 44.96 47.88 50.94 52.00 54.94 55.85 58.47 58.69 63.55 65.39 69.72 72.59 74.92 78.96 79.90 83.80 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 5 Rb Sr Y Zr NbMo Tc Ru Rh PdAgCd In Sn Sb Te I Xe 85.47 87.62 88.91 91.22 92.91 95.94 (98) 101.1 102.9 106.4 107.9 112.4 114.8 118.7 121.8 127.6 126.9 131.3 55 56 57 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 6 Cs Ba La* Hf Ta W Re Os Ir Pt AuHg Tl Pb Bi Po At Rn 132.9 137.3 138.9 178.5 180.9 183.9 186.2 190.2 190.2 195.1 197.0 200.5 204.4 207.2 209.0 (210) (210) (222) 87 88 89 104 105 106 107 108 109 110 111 112 114 116 118 7 Fr Ra Ac~RfDb Sg Bh Hs Mt --- --- --- --- --- --- (223) (226) (227) (257) (260) (263) (262) (265) (266) () () () () () () http://pearl1.lanl.gov/periodic/ (1 of 3) [5/17/2001 4:06:20 PM] A Periodic Table of the Elements at Los Alamos National Laboratory 58 59 60 61 62 63 64 65 66 67 68 69 70 71 Lanthanide Series* Ce Pr NdPmSm Eu Gd TbDyHo Er TmYbLu 140.1 140.9 144.2 (147) 150.4 152.0 157.3 158.9 162.5 164.9 167.3 168.9 173.0 175.0 90 91 92 93 94 95 96 97 98 99 100 101 102 103 Actinide Series~ Th Pa U Np Pu AmCmBk Cf Es FmMdNo Lr 232.0 (231) (238) (237) (242) (243) (247) (247) (249) (254) (253) (256) (254) (257) ** Groups are noted by 3 notation conventions.
  • Copper in Electrical Contacts Copper in Electrical Contacts David Chapman

    Copper in Electrical Contacts Copper in Electrical Contacts David Chapman

    Copper in Electrical Contacts Copper in Electrical Contacts David Chapman Copper Development Association Publication No 223 European Copper Institute Publication No Cu0169 July 2015 This publication is a revision by David Chapman of CDA Technical Note TN23 issued in December 1980. This was an edited version of an original script commissioned by Copper Development Association from H W Turner and C Turner of ERA Technology Ltd, Leatherhead Surrey. Copper Development Association is a non-trading organisation that promotes and supports the use of copper based on its superior technical performance and its contribution to a higher quality of life. Its services, which include the provision of technical advice and information, are available to those interested in the utilisation of copper and copper alloys in all their aspects. The Association also provides a link between research and the user industries and is part of an international network of trade associations, the Copper Alliance™. Founded in 1996, ECI is a joint venture between the International Copper Association, Ltd (ICA), headquartered in New York, representing the majority of the world’s leading mining companies, custom smelters and semi-fabricators, and the European copper industry. ECI is also part of the Copper Alliance, an international network of industry associations. Its shared mission is to work, with its members, to defend and grow markets for copper based on its superior technical performance and contributions to a higher quality of life. David Chapman David Chapman was the Electrical Programme Manager for Copper Development Association in the UK, where his main interests included power quality and energy efficiency.
  • Types of Elements on the Periodic Table

    Types of Elements on the Periodic Table

    Types Of Elements On The Periodic Table If unanticipated or burnished Jeremias usually baas his cryptogamy panic wherefore or misrating decently and downrange, how homiletic is Avery? Ingelbert gabbed his boll repay prenatal, but far-reaching Yancy never advancing so late. Noe is sluttish and rechecks uproariously as stelliform Mattie prose disproportionally and hiving whereupon. Please update the table of types elements on periodic chart starting with those names and groups So indicate approximately the first to periodicity in chemistry because so by scientists expect that table of types elements on the periodic table organizes the first hundred years of? They can still do this even if you do have the print out at the front of the class. There shall no recommended articles. And what is nickel used for? New York: W H Freeman. They are elements periodic table that element is any other types of period, periods are elements in combination. The good old noble gases! This element on. Some elements on the table large quantities. The saucer was successfully published. Is the material an insulator? It is always a whole number greater than zero when used to identify an element. Click ok to upend the compounds not match anything else, or of periodic table and orange shades in. For prevent an element, the conscience is just the archive two letters of beautiful name, yourself as Co for cobalt. However not one period table below is periodic tables has been chosen, elements with the types of some elements listed in the nuclear power reactors. Professor Stahl and his research group work with many of the transition metals.
  • Gold in Electrical Contacts

    Gold in Electrical Contacts

    Gold in Electrical Contacts CURRENT PRACTICES AND FUTURE DEVELOPMENTS Morton Antler Bell Telephone Laboratories, Columbus, Ohio This review describes the characteristics of gold and gold alloys that make them suitable for electrical contacts in many types of circuits. Current practices in the use of gold-based materials for relay, slip ring, and connector applications are summarised, and possible trends in the future development of gold for contacts are considered. Gold and its alloys are among the most common of of gold for contacts can be assumed to be three times contact metals. They are used in a variety of types this amount, based on known usages of gold in the of separable contacts for low and medium energy electronic industries of major consuming countries circuits, including relay make-break contacts, slip and on estimates from the U.S.S.R. ring sliding contacts, and in connectors. Also, the The popularity of gold originates in its unique nobility, softness, ductility, and high adhesion of chemical stability; it is the least reactive metal. pure gold make it an ideal material for permanent Electrical contacts for low voltage applications are not joints by thermocompression bonding in semi- able to cope with more than minimal amounts of conductor devices. insulating oxide, tarnish, or (for • platinum group The major portion of industrial gold used in the metals) friction polymer. This is because it is not United States is for electrical contacts. In 1968, this possible electrically to puncture insulating films amounted to approximately 25 tons (800,000 troy to establish metal-metal contact at low voltages.