Electrical contact

Abstract: An electrical contact (66) for electrically con­ necting pads (4 and 8) of a substrate (6) and a panel (12), respectively, comprises parallel inner arms (68) connected together by a central bight (70), at one end, the other ends of the arms (68) being connected by bights (72) to outer arms (74) having pad engaging, bowed, contact sur­ faces (82) from which extend portions (78) having contact ends (80). As the pads (4 and 8) are pressed against the bowed contact surfaces (82), the inner and outer arms (68 and 74) function as spring members rather than as conduc­ tors and determine the contact pressure between the contact surfaces (82) and the pads (4 and 8). The contact ends (80) engage, and wipe against, the central bight (70) providing a short electrical path between the pads (4 and 8).

Description: This invention relates to electrical contacts, especially for use in connectors, such as IC chip carrier sockets or similar substrates, for integrated circuit chip carriers and particularly in connectors which have contact members contained in modules which are assembled to a connector frame or housing. Such a connector is described and claimed in EP-A-0 255 244 from which the present application has been divided. Integrated circuits (ICs) and other electronic devices are commonly packaged in so-called IC chip carriers. A chip carrier comprises a body of insulating material having the IC chip contained therein and having contact pads at predetermined spaced locations near its periphery. The dimensions and other standards for such chip carriers are established in a specification, commonly referred to as the JEDEC standard, which was established and which is maintained by the Electronics Industries Association of 2001 I Street, N.W., Washington, D.C., 2006. Connectors for integrated circuit chip carriers, such as chip carrier sockets or other types of connectors, must be manufactured so that the contact members in the connector housing will contact the pads in the integrated circuit chip carrier when the chip carrier is assembled to the connector housing. Standard chip carriers are produced with varying numbers of contact pads of "positions" ranging from 64 positions to 164 positions or even more in proposed new designs. It is known to produce connectors for IC chip carriers in the form of a housing having a plurality of contact modules therein or thereon, each contact module comprising usually a length of insulating material having spaced-apart metallic contacts therein, see for example U.S. Patents 3 960 423, 4 571 015, and 4 593 463. A uni planar contact element for an IC chip carrier connector is disclosed in US-A-4 513 353 or in DE-A-26 06 695. The use of contact modules offers several advantages such as the fact that different types of modules can be fitted into a standard housing frame so that a single type of frame can be used for an entire family of connectors such as chip carrier sockets. Additionally, the use of modules frequently will simplify the manufacturing process. Since the contacts of such modules are used for the connection of high frequency devices, the contacts should in each case provide a short current flow path in order to avoid inductance effects. At the same time, however, the spring characteristics of the contact should be sufficient to make effective electrical contact with said contact pads. To these ends, the present invention consists in an electrical contact of generally Σ-shape having substantially all of its parts lying in a single plane, the electrical contact comprising, in combination, the following features : a first spring contact means is provided proximate a second spring contact means; a bight portion has a first end integral with the first spring contact means and a second end integral with the second spring contact means; the first spring contact means has a spring portion, a contact portion, and a leg portion the spring portion having a first end which is integral with the bight portion and a second end which is attached to the contact portion, the spring portion is configured in such a manner as to provide the spring characteristics required to ensure proper operation of the electrical contact, the contact portion extends from the spring portion such that the contact portion is positioned to effect electrical engagement with contact pads of a substrate or the like, the leg portion extends from the contact portion such that a free end of the leg portion is positioned proximate the bight portion; the second spring contact means has a spring portion, a contact portion, and a leg portion, the spring portion having a first end which is integral with the bight portion and a second end which is attached to the contact portion, the spring portion is configured in such a manner as to provide the spring characteristics required to ensure proper operation of the electrical contact, the contact portion extends from the spring portion such that the contact portion is positioned to effect electrical engagement with contact pads of a substrate or the like, the leg portion extends from the contact portion such that a free end of the leg portion is positioned proximate the bight portion; the free end of the leg portion of the first spring contact means and a first section of the bight portion are in overlapping relationship, as are the free end of the leg portion of the second spring contact means and a second section of the bight portion, whereby as the contact portions of the first and second spring contact means are brought into engagement with respective electrical components, the spring portions are resiliently depressed, causing the free ends of the leg portions to engage the corresponding sections of the bight portion, this motion results in a wiping action between the respective free ends of the leg portions and the bight portion, resulting in current flowing in a path from the first electrical component through the contact portion of the first spring contact means, the leg portion of the first spring contact means, the bight portion, the leg portion of the second spring contact means, the contact portion of the second spring contact means, and to the second electrical component. For a better understanding of the invention and to show how it may be carried into effect reference will now be made by way of example to the accompanying drawings in which:- FIGURE 1 is a perspective exploded view showing a connector embodying the invention and a substrate and a circuit board or other substrate in alignment with the connector. FIGURE 2 is a top plan view, with parts broken away, showing the connector mounted on the circuit board or other lower substrate. FIGURE 3 is a sectional view looking in the direction of the arrows 3-3 of Figure 2. FIGURE 4 is a view similar to Figure 3 but showing the parts exploded from each other. FIGURE 5 is a perspective view showing an individual contact module of the connector with one contact or contact member exploded from the module. FIGURE 6 is a perspective view showing an alternative form of the connector. Referring to Figures 1-4, a connector assembly 2 serves to connect contact pads 4 on a substrate 6 to terminal areas or pads 8 on one surface 10 of a panel-like member 12 which may be a circuit board or another device having a substrate. The substrate 6 comprises a square body of insulating material having an upper substrate surface 14, as viewed in the drawing, a lower substrate major surface 16, and peripheral substrate side surfaces 18 which intersect at corners 20. Keyway notches 22 extend into the peripheral substrate side surfaces 18 between each pair of adjacent corners 20. The connector assembly 2 comprises a housing assembly 24 which in turn comprises a housing frame 26 in which there are contained a plurality of modules 48 described below. The housing frame has an upper housing major surface 28, a lower or second housing major surface 30, and peripherally extending housing side surfaces 32 which intersect at corners. A central portion of the upper surface 28 constitutes a substrate receiving zone 34 which is square and which includes, but extends beyond, a central opening in the housing frame. Module receiving openings 36 are provided between the central opening and the peripheral side surfaces 32. These module receiving openings 36 surround the substrate receiving zone 34 and in the disclosed embodiment four such openings 36 are provided, each opening extending along one of the sides of the square substrate receiving zone. Each opening 36 has ends 38 that are adjacent to the corners of the frame and has inner and outer opening sidewalls 40, 42, the outer sidewall being adjacent to the peripheral surface 32 as shown in Figure 2. Each opening has a pair of centrally located opposed keyways 44 for reception of a substrate positioning key 46 which is received in the notches 22 of the substrate. The keyways 44 are substantially midway between the ends 38 of the opening. Additional keyways 47 are provided in the sidewall 42 and are between the keyways 44 and one of the ends 38. Referring now to Figure 5, each of the modules 48 comprises a block of insulating material, preferably, a molded plastic material, having upper and lower major surfaces 50, 52 as viewed in the drawing, inner and outer side surfaces 54, 56, and ends 58. Each module has a module key 57 integral with its side surface 56 which is dimensioned to be received in one of the module keyways 47, thereby accurately to locate the module in its respective module receiving opening. A plurality of contact receiving cavities 60 extend inwardly of each module from the side surface 54 and extend to the upper and lower surfaces 50, 52. Each cavity also extends completely through the module to the surface 56 and has a central positioning rib 62 which extends from the surface 56 towards the surface 54. Upper and lower positioning ribs are also provided as shown at 64 and 65. These positioning ribs accurately locate the contact members 66 in the cavities. The contact members 66 provide an electrical path downwardly as viewed in Figures 3 and 4 from the terminal pads 4 on the upper substrate to the terminal pads 8 on the panel-like member 12. The contact members are of general Σ-shape and are flat stamped sheet metal devices. Each has a pair of parallel central or inner arms 68 connected by a bight portion 70. The left-hand ends of the arms as viewed in Figure 4 are curved as shown at 72, thereby to provide upper arms 74 which are adjacent to the upper and lower surfaces of the housing frame. Adjacent to their ends, the arms 74 extend laterally as shown at 76 to a contact portion 82 and then inwardly as shown at 78 to their ends 80. The ends are also contact portions in that they bear against the bight portion 70 so that the electrical path extends from the upper contact portion 82 to the bight portion and then through the lower arm portion 78 to the lower contact portion. The arms 68 and 74 thus function as spring members rather than as conductors and determine the contact pressure at the various electrical interfaces at 82 and 80 as viewed in Figure 3. It should be mentioned that an extremely short electrical path is desirable for high speed (high frequency) devices in order to avoid inductance effects. As shown best in Figures 1 and 3, the connector has upper and lower pressure plates 84, 86 which are preferably of metal and a lower insulator plate 88 which is interposed between the lower pressure plate 86 and the underside of the panel-like member 12. The entire assembly is held in position by means of screws 90 which extend through the entire assembly and which are received in threaded holes in the upper pressure plate 84. As will be apparent from a comparison of Figures 3 and 4, when the screws are tightened, the individual contact members are flexed and the contact portions 82 are urged against the pads 4, 8, and the ends of the arms 78 are urged against edge portions of the bight 70. A wide variety of connectors can be produced at greatly reduced tooling cost for the reason that a variety of modules 48 can be used with a standard housing frame 24. For example, the standard frame 24 can be used with modules having different numbers of contact members in each module and with different center-to-center spacings of the contact members in each module. It can be appreciated that the tooling cost (the cost to produce the mold) to manufacture a connector housing is quite high and the larger the number of contact members in the housing, or to put it another way, the higher the density of the contact members, the greater the cost of tooling. The connector shown in the accompanying drawings is, in fact, designed to have 320 contact positions therein or 80 contact positions along each of the sides of the square substrate receiving zone 34. The standard overall dimensions of connectors of this type are about 36.8 mm (1.45 inches) on each side of the substrate receiving zone has 80 contact members on very closely spaced centers. In practice, it is only necessary to produce a mold to manufacture a single module as shown at 48 having 20 cavities therein for contact members 66. The individual modules are then assembled to the frame as described above. By prior art methods, on the other hand, it would be necessary to produce a mold for a housing member having 320 cavities therein. It should be mentioned that an added advantage is achieved in many instances by virtue of the fact that the cavities are produced in the individual modules rather than in the frame housing and the tooling problems are thereby greatly simplified. It can be seen that the individual cavities in the module of Figure 5 can be molded with straight action type injection molding material. If it were attempted to produce cavities of the same configuration directly in the housing frame, the molding operation would be rendered much more difficult. The advantages discussed above are achieved, as a practical matter, by virtue of the fact that the module locating means of the connector for locating the individual modules in the housing frame, and the substrate locating means, for locating the substrate on the housing frame, are directly related to each other and the usual problems encountered with tolerance buildup in the manufacture of connectors are greatly alleviated. The module locating and substrate locating systems for the connector are interrelated in the sense that the keyways 44, which locate the substrate on the housing frame and the keyways 47, which locate the modules in the housing frame, are determined from a common reference point when the housing frame is manufactured. The parts which are assembled to the housing frame, the modules 48 and the substrate 6, are thus brought into registry with each other by the commonality of the locating or keying systems which locate these parts on the frame. The importance of the interrelated keying systems discussed above can be appreciated from a consideration of the problems which are always encountered in the manufacture of connectors of the type under consideration with reference to the location of the contact receiving cavities. In general, the cavities in a connector housing cannot be exactly positioned or located but can only be located in the housing within dimensional tolerances; for example, the center-to-center spacing between adjacent cavities in a housing might be 0.508 mm (0.02 inches) plus or minus about 0.102 mm (0.004 inches). The variations due to this tolerance are not always self-cancelling and for this reason, designers commonly specify a cumulative tolerance which is to say they specify a limitation on the tolerance buildup should all of the variations from the nominal dimension be on the plus side rather than on the minus side. Cumulative tolerances are virtually uncontrollable when the number of units, in this case contact receiving cavities, grows relatively large. Thus since the disclosed connector has 80 contact receiving cavities along each side of the substrate receiving zone, it would have a very large cumulative tolerance buildup in each of the sections of 80 contact members. The contact members are, however, handled in small groups and the maximum cumulative tolerance buildup is limited to the cumulative buildup of that group. In the disclosed connector, each module has 20 cavities and the maximum cumulative tolerance buildup is therefore limited by that number. Figure 6 shows an alternative form of the connector which is generally similar to that of Figures 1-5 but differs therefrom in that the locating system for the modules and the locating system for the substrate 4 have a shared common keying member 92. In this instance, a module bridges or extends past each of the pairs of opposed keyways 44 and the common keying member 92 has arms such that it can extend into one of the cavities of the common module. The common keying member 92 thus has an upstanding ear 96 which is received in a notch 22 of the substrate.

Claims: An electrical contact (66) of generally Σ-shape having substantially all of its parts lying in a single plane, the electrical contact (66) comprising, in combination, the following features : a first spring contact (68, 72, 74, 76, 78) means is provided proximate a second spring contact means (68, 72, 74, 76, 78); a bight portion (70) has a first end integral with the first spring contact means and a second end integral with the second spring contact means; the first spring contact means has a spring portion (72), a contact portion (76), and a leg portion (78), the spring portion (72) having a first end (68) which is integral with the bight portion (70) and a second end (74) which is attached to the contact portion (76), the spring portion (72) is configured in such a manner as to provide the spring characteristics required to ensure proper operation of the electrical contact (66), the contact portion (76) extends from the spring portion (72) such that the contact portion (76) is positioned to effect electrical engagement with contact pads (4) of a substrate or the like, the leg portion (78) extends from the contact portion (76) such that a free end (80) of the leg portion (78) is positioned proximate the bight portion (70); the second spring contact means has a spring portion (72), a contact portion (76), and a leg portion (78), the spring portion (72) having a first end (68) which is integral with the bight portion (70) and a second end (74) which is attached to the contact portion (76), the spring portion (72) is configured in such a manner as to provide the spring characteristics required to ensure proper operation of the electrical contact (66), the contact portion (76) extends from the spring portion (72) such that the contact portion (76) is positioned to effect electrical engagement with contact pads (8) of a substrate or the like, the leg portion (78) extends from the contact portion (76) such that a free end (80) of the leg portion (78) is positioned proximate the bight portion (70); the free end (80) of the leg portion (78) of the first spring contact means and a first section of the bight portion (70) are in overlapping relationship, as are the free end (80) of the leg portion (78) of the second spring contact means and a second section of the bight portion (70), whereby as the contact portions (76) of the first and second spring contact means are brought into engagement with respective electrical components (4,8), the spring portions (72) are resiliently depressed, causing the free ends (80) of the leg portions (78) to engage the corresponding sections of the bight portion (70), this motion results in a wiping action between the respective free ends (80) of the leg portions (78) and the bight portion (70), resulting in current flowing in a path from the first electrical component (4) through the contact portion (76) of the first spring contact means, the leg portion (78) of the first spring contact means, the bight portion (70), the leg portion (78) of the second spring contact means, the contact portion (76) of the second spring contact means, and to the second electrical component (8). An electrical contact (66) as recited in claim 1, in which the spring portions (72) of said first spring contact means and said second spring contact means are of a generally U-shaped configuration. An electrical contact (66) as recited in claim 1 or 2, in which the free ends (80) of the leg portions (78) of said first spring contact means and said second spring contact means have an arcuate configuration. An electrical contact (66) as recited in claim 1, 2 or 3, in which said first spring contact means is essentially a mirror image of said second spring contact means.

Inventors: GRABBE DIMITRY G, KORSUNSKY IOSIF, GRABBE, DIMITRY G., KORSUNSKY, IOSIF
Applicants: WHITAKER CORP, THE WHITAKER CORPORATION
Application year: 1990
Main classification: H05K7
IPC codes: H01R11, H01R33, H05K7