WO2000054370A2

WO2000054370A2 - A connector assembly providing error resistant coupling of electrical signals

Info

Publication number: WO2000054370A2
Application number: PCT/US2000/006466
Authority: WO
Inventors: Henry O. Herrmann, Jr.
Original assignee: The Whitaker Corporation
Priority date: 1999-03-12
Filing date: 2000-03-10
Publication date: 2000-09-14
Also published as: WO2000054370A3; TW464100U; WO2000054370A9; AU3525900A

Abstract

An electrical connector assembly (10) with a contact (12) having a high resistance portion. When the contact of the electrical connector assembly first makes contact with the one or more contacts of a receptacle assembly (30), the high resistant portion prevents a voltage surge. As the electrical connector assembly (10) is further inserted to the receptacle assembly (30), the energy passing from the receptacle to the electrical connector assembly is gradually increased. Eventually, the contacts within the receptacle pass the high resistant portion of the contact of the electrical connector assembly (10) and make contact with the conductive portion (20) of the electrical contact, thereby permitting transmission of valid signals without the generation of spurious errors.

Description

A CONNECTOR ASSEMBLY PROVIDING ERROR RESISTANT COUPLING OF ELECTRICAL SIGNALS

This invention relates generally to electrical connectors for electronic devices . More particularly, the invention relates to electrical contacts for use in electrical connectors particularly suited for use in computers and peripheral equipment therefor to prevent the generation of spurious signals upon the mating of the electrical connector of the peripheral equipment with the electrical receptacle of the computer.

Electrical connectors having contacts that carry electrical signals for peripheral electronic devices that are mated to receptacles of electronic systems, such as computers, are well known in the art. A recurrent problem with many prior art mating plugs is the generation of spurious signals upon the mating of the peripheral electronic devices with corresponding receptacles of the electronic systems when the electronic system and/or the device is already energized. The mating therebetween may induce a voltage pulse into the energized electronic system. The voltage pulse may travel through the electronic system, thereby introducing spurious errors into the system. This problem is known in the art as the "hot swap" problem.

The condition that causes errors in electronic systems results from the very high data rates and very low energy of the signals being used within the systems . The input capacitance of the mating plugs, printed circuit board lines, and device capacitance of associated buffer integrated circuit devices are the basis of the problem. Energy must flow from the system bus to charge this input capacitance, (generally tens of picofarads) . When energy is removed from the system bus, such as by having a peripheral device connected thereto, or when energy is input to the system bus by a nanosecond pre- charge circuit or buffer leakage, a voltage pulse to an adjacent device on the bus occurs, thereby creating errors in the system. The voltage pulse may be no grater than normal signals so no new radiated noise problem is introduced. However, the voltage pulse can cause data to be incorrectly transferred. Accordingly, the interconnections themselves are a large portion of the problem. This problem is universal since it affects both digital and analog electronic circuits.

The prior art has generally addressed the "hot swap" problem by using logic and timing control circuitry, such as that which is disclosed in U.S. Patent No. 4,245,270 to slowly ramp up the voltage within the connecting line. However, this only addresses disturbances to the power supplies, not the signal lines.

Many connecting schemes require certain portions of the connector to be mated prior to other portions, or in a particular sequence. For example, with respect to power applications, U.S. Patent No. 4,079,440 discloses a circuit board having two connector plugs of differing lengths . The longer connector plug makes initial contact with a power line prior to the shorter plug, which reduces the onset of power surges. However, this scheme requires manual dexterity and specific insertion and removal timing for proper operation, as well as additional plugs.

A connector assembly disclosed in U.S. Patent No. 4,747,783 attempts to eliminate timing and control circuitry for power applications. This connector assembly uses a long pin in the "plug" to first make contact with its mating "socket" to gradually increase the voltage to the socket until the entire plug makes mating contact with the socket. The plug comprises a pin having a thin insulating material covering the surface and a thin low resistive material covering the insulating material. When the plug makes initial contact with the socket, the current must pass through the resistive portion of the plug, this permits the electronic components in the peripheral device to charge gradually and eliminates the current surges which may otherwise result. This device having a long pin is undesirable for several reasons. First, it requires the use of several contacts of differing lengths, thereby raising manual dexterity problems. Secondly, although the low resistance (i.e., 2-60 ohms) is sufficient to eliminate current surges in power transmissions, it is not sufficient to eliminate the voltage pulse from being introduced into the electronic system. In addition, the thin layer of low resistive material surrounding the thin layer of insulating material introduces an additional problem into the connection between the peripheral device and the electronic system; short capacitance. As explained previously, capacitance is undesirable in a connector .

U.S. Patent Application Serial No. 09/042,400, having Attorney Case No. 17231, filed March 13, 1998, assigned to the same assignee of the present invention, and entitled "Improved Contact for Error Resistant Coupling of Electrical Signals," serves well its intended purpose of eliminating the spurious signals. It is desired that further improvements be provided so as to further reduce and even eliminate the "hot plug" problem. It would be desirable to provide a signal connector assembly that would prevent the introduction of errors into an electronic system during a hot plug mating condition.

It would be further desirable to provide a signal connector assembly having electrical contact selection, that is, some electrical contacts may be provided with means for eliminating the "hot swap" problem, while other electrical contacts may be conventional .

The present invention provides a signal connector assembly having at least one signal contact with a high resistive portion so that when the signal connector assembly associated with a peripheral first makes contact with a receptacle assembly of an electronic system, such as a computer, the high resistive portion of the at least one signal contact of the signal connector assembly prevents a voltage spike from occurring. To prevent voltage pulses, variably resistive portions are necessary depending upon the application. As the plug is further inserted into the receptacle, the energy flow is gradually increased. Eventually, the high resistant portion of the at least one signal contact passes the mating contacts of the receptacle and allows a low resistance portion of the at least one signal contact to make a final engagement with the mating contacts of the receptacle, thereby permitting transmission of valid signals without the generation of spurious errors.

It is an object of the present invention to provide a signal connector assembly which permits connection of a peripheral device to an energized electronic system, such as a computer, without introducing any spurious errors into that system.

It is another object of the present invention to provide a signal connector assembly having electrical contacts that may be selected with or without means for eliminating the "hot swap" problem. Other objects and advantages of the present invention will become apparent after reading the detailed description of the presently preferred embodiment.

Figure 1 illustrates dual signal electrical contacts of a portion of a signal connector assembly of the present invention .

Figure 2 illustrates quadruple flexible electrical contacts of a portion of a receptacle assembly associated with the practice of the present invention. Figure 3 illustrates the insertion of the signal connector assembly of Figure 1 into the receptacle assembly of Figure 2 prior to the mating therebetween.

Figure 4 illustrates the mating of the signal connector assembly of Figure 1 with the receptacle assembly of Figure 2.

Figure 5 illustrates a plurality of the signal contacts of the signal connector assembly of Figure 1.

Figure 6 illustrates the leading surface of the signal contact of the signal connector assembly of Figure 5.

Figure 7 is a view of the leading surface of the contact of the signal connector assembly taken along line

7-7 of Figure 6.

Figures 8, 9 and 10 illustrate various embodiments for locating a high resistant material in the signal contact of the signal electrical connector assembly of the present invention.

Figure 11 illustrates the performance gained by the signal electrical connector assembly of the present invention relative to a prior art signal electrical connector assembly.

With reference to the drawings, wherein the same reference number indicates the same element throughout, there is shown in Figure 1 two signal electrical contacts 12 and associated housing of the signal electrical connector assembly 10 of the present invention. It should be recognized that although two contacts are shown in detail for simplicity, there are typically more than two contacts 12 with every signal electrical connector assembly 10 for mating with corresponding contacts of a receptacle assembly. Conversely, the signal connector assembly 10 may comprise a sole signal electrical contact 12 and, more importantly, the practice of the present invention contemplates the utilization of a sole signal electrical contact 12. The signal electrical connector 10 may be interchangeable are referred to herein as a mating plug, and further the signal electrical contact 12 may be simply referred to herein as the contact 12. Further, it should be recognized that the signal electrical connector assembly 10 may have a mixture of signal contacts some with means for eliminating the "hot swap" problem in accordance with the practice of the present invention, and some with conventional signal contacts. This feature of mixed signal contacts provides the designer with the selectability to customize the signal electrical connector to meet various needs .

The signal electrical connector assembly 10 of Figure 1 comprises two housing members 14 and 16, known in the art, that define a cavity 18. Each of the signal electrical contacts 12 has a leading surface portion 20, a wing section 22, and a trailing section portion 24. The leading surface portion 20 provides initial sliding engagement with at least one flexible electrical conductor, to be described with reference to Figure 2. The leading surface portion 20 is defined by a material having a variable resistance in the range from about 100Ω to about 100MΩ to be further described with reference to Figures 8-10. The wing section 22 is merged into the leading surface portion 20 for intermediate engagement of the at least one flexible electrical conductor. The trailing surface portion 24 is merged into the wing section 22 for final sliding engagement of the at least one flexible electrical conductor in a fully mated relationship therebetween to produce a relatively low resistance connection. The trailing surface portion 24 is defined by a conductive material and has a tail 24A that is interconnected to the signal capable of being carried by contact 12.

For the embodiment of Figure 1, the two contacts 12 are separated by a non-electrically conductive spacer 26 which may be comprised of a plastic material. The spacer 26 is placed between and separates the two electrical contacts 12 by a distance corresponding to a predetermined distance that separates two corresponding flexible electrical conductors of the receptacle assembly, to be described with reference to Figure 2. The non-electrically conductive spacer 26 has a nose section 28 that intercepts and spreads apart the two flexible electrical conductors, before the initial engagement thereof by leading surface portion 18 of each of the two contacts 12. The mating plug 10 carrying the spacer 26 mates with the receptacle assembly 30 which may be described with reference to Figure 2.

Figure 2 illustrates a portion of the receptacle assembly 30 that has dimensions complementary to the mating plug 10 so as to accommodate the mating therebetween. The receptacle 30 has many of the features disclosed in U.S. Patent 5,586,915 of R.J. Baker et al which is herein incorporated by reference. The receptacle assembly 30 has flexible electrical conductors 32_x, 32₂, 32₃ and 32₄, with at least one conductor thereof for receiving a respective electrical signal being carried by a single contact 12 of the mating plug 10. For the embodiment shown in Figures 1 and 2 , each of the contacts 12 of Figure 1 mates with a respective flexible conductor, such as 32ι or 32₃. The flexible conductors 32ι, 32 , 32₃ and 32 , known in the art, are typically contacts of a backplane for an electronic system, such as a computer. It should be recognized that only one arrangement for the mating with two contacts 12 is shown for receptacle assembly 30 for the sake of simplicity, but typically there are at least two or more arrangements provided by the receptacle assembly 30 for mating with additional and corresponding contacts 12 over and above the two contacts 12 shown in Figure 2. The receptacle assembly 30 comprises housing members 34 and 36 that are dimensioned to fit into the cavity 18 of the mating plug 10, when the mating plug 10 is moved in the direction 38 into the receptacle assembly 30. The mating of the mating plug 10 and the receptacle 30 may be further described with reference to Figure 3.

As seen in Figure 3, the nose section 28 of the spacer 26 is about to intercept and spread the flexible conductors 32ι, 32₂, 32₃ and 32₄ outward. Continued insertion of the mating plug 10 causes the nose section 28 to spread flexible conductors 32ι, 32₂, 32₃ and 32 and allow the flexible conductors 32χ, 32₂, 32₃ and 32 to move over the nose section 28 and onto the leading surface portion 22 of each contact 12 of Figure 3 comprised of the resistive material . Further continued insertion of the mating plug 10 allows for final sliding engagement on flexible conductors 32ι, 32₂, 32₃ and 32 in a fully mated relationship with the trailing section 24 of each of the two contacts 12 so as to produce a relatively low resistance connection therebetween and which may be further described with reference to Figure 4.

As seen in Figure 4, the flexible conductors 32ι, 32₂, 32₃ and 32₄ are in their final engagement with the trailing portion 24 of each of the contacts 12 of Figure 4 comprised of an electrically conductive material so as to provide a low resistance contact between the electrical contact 18 and the flexible contacts 32χ, 32₂, 32₃ and 32₄ of about 50 milliohms. The electrical contact 12, more particularly, a plurality of electrical contacts 12 each having a leading surface portion 20, preferably a wing section 22, and a trailing surface portion 24 may be further described with reference to Figure 5 illustrating the conductive paths of the electrical connector assembly 10 with the spacers 26 removed from the connector 10. As seen in Figure 5, a valley 42 is preferably located adjacent the wing section 22 of each electrical contact 12 and the valley 42 leads into the trailing surface portion 24 which, in turn, leads into an electrical conductive pattern 44, known in the art, within the signal electrical connector assembly 10. The leading surface portion 20 and the wing section 22 of the electrical contact 12 may be further described with reference to Figure 6. Figure 6 illustrates the leading surface portion 20 as having contained therein the resistive material (shown in cross hatch) and also illustrates the wing section 22 which may be further described with reference to Figure 7 and which is a view taken along line 7-7 of Figure 6. Figure 7 illustrates the shape of wing section 22, in cross section, and is preferably comprised of a copper based material.

The resistive material placed in the leading surface portion 20 is of particular importance to the present invention and has various embodiments which may be described with reference to Figures 8, 9 and 10. The resistive material embedded in the leading surface portion 20 may be of the type and resistivity disclosed in the previously mentioned U.S. Patent Application

Serial No. 09/042,400 which is herein incorporated by reference.

Figure 8 illustrates the wing section 22 as having a groove 50 and a first embodiment 20A of resistive material located entirely in front of the groove 50. The resistive material 20A, as well as other embodiments, replaces the original metal that is removed from the leading surface portion 20 and is comprised of a material that provides a variable resistance in the range from about 100Ω to about 100MΩ.

Figure 9 illustrates a second embodiment 20B of resistive material that extends from the tip of the leading surface portion 20 all the way past the wing section 22. Figure 10 is composed of Figures 10(A), 10(B) and

10(C) and illustrates a third embodiment of a resistance material 20C (see Figure 11(A)) that eliminates the wing section 22 (see Figures 10(A), (B) and (C) ) .

The embodiments of Figures 8-10 provide the variable resistivity necessary to prevent spurious signals, discussed in the "Background" section, when the connector assembly 10 is mated with the receptacle assembly 30.

In operation, the mating plug 10 is inserted into the receptacle assembly 30 and the flexible contacts 32ι, 32 , 32₃ and 32 which make first contact with, for the embodiments of Figures 1 and 2, the spacer 26 and then with the leading surface portion 20 of each of the two contacts 12 having the resistive material embedded therein. Since it is contemplated that the electronic system will be energized, this will permit energy from the electronic system to begin flowing from the flexible conductors 32ι, 32₂, 32₃ and 32 , through the resistive material within the leading surface portion 20 and into the remainder of the conductive portion of each of the contacts 12. The resistive material reduces the magnitude of the voltage pulses such that they do not present errors into the electronic system. More particularly, a portion of the voltage "seen" by the mating plug 10 drops across the resistive material. As the mating plug 10 is inserted further into the receptacle assembly 30, the flexible conductors 32ι, 32 , 32₃ and 32 pass along the surface of the resistive material embedded in the leading surface portion 20 until the flexible contacts 32ι, 32₂, 32₃ and 32 finally reach the trailing portion 24 of each of the contacts 12. When the mating plug 10 is fully inserted into the receptacle 30, the flexible conductors^" 32ι, 32 , 32₃ and 32₄ are in direct contact with the trailing portion 24 of each of the electrical contacts 12. Accordingly, there is now no voltage drop across the resistive material embedded in the leading surface portion 20 of the contact 12. With respect to capacitance, the arrangement of the present invention specifically limits the capacitance between the metallic portions of the mating plug 10 and the receptacle assembly 30 to an acceptably low level. It accomplishes the limitation by minimizing the associated effective coupling area and by minimizing the effective dielectric constant between mating metallic portions which is primarily air.

A primary aspect of preventing a voltage pulse is to reduce the initial current that can be taken from or supplied to a signal electrical contact 12 upon insertion of the mating plug 10 into the receptacle assembly 30. This prevention has been achieved by the practice of the present invention and may be further described with reference to Figure 11.

Figure 11 illustrates two waveforms 46 and 48, with the waveform 46 illustrating the effect achieved by the electrical contact 12 of the present invention having means for eliminating the "hot swap" problem discussed in the "Background" section, and with waveform 48 representing a prior art electrical connector assembly not having the benefits of the present invention. Both

(electrical contact 12 and the conventional contact) were carrying respective electrical signals when individually connected to a single line equivalent to a Small Computer System Interface (SCSI) bus line. From Figure 11 it is seen that waveform 46 is relatively constant as compared to waveform 48 having the spike portions shown therein.

Although the invention has been described in part by making detailed reference to certain specific embodiments, such details are not intended to be restrictive. It will be appreciated by those skilled in the art that many variations may be made in a structured mode of operation without departing from the spirit and scope of the invention as disclosed in the teaching herein.

Claims

What is claimed is:

1. A plug (10) for mating with a receptacle having at least one flexible electrical conductor for receiving an electrical signal, said plug having at least one contact (12) capable of carrying an electrical signal and engaging said at least one flexible electrical conductor and providing error resistant coupling of said electrical signal, said at least one contact comprising: a leading surface portion (20) for initial sliding engagement with said at least one flexible electrical conductor, said leading surface portion comprising a conductive material substrate and a resistive material applied directly to the conductive substrate. a trailing surface portion (24) for final sliding engagement of said at least one flexible electrical conductor in a fully mated relationship therebetween to produce a relatively low resistance connection, said trailing surface portion being defined by a conductive material.

2. The plug as described in claim 1 , wherein said leading surface portion and said trailing surface portion define a contiguous surface.

3. A plug (10) for mating with a receptacle having at least two flexible electrical conductors spaced apart from each other by a predetermined distance for receiving two respective electrical signals, said plug having at least two contacts (12) capable of carrying an electrical signal and^" intercepting said at least two flexible electrical conductors and providing error resistant coupling of said electrical signals, said plug comprising:

(a) two contacts (12) each comprising: a leading surface portion (20) for initial sliding engagement with said at least one flexible electrical conductor, said leading surface portion comprising a conductive material substrate and a resistive material applied directly to the conductive material substrate; a trailing surface portion (24) for final sliding engagement of said at least one flexible electrical conductor in a fully mated relationship therebetween so as to produce a relatively low resistance connection, said trailing surface portion being defined by a conductive material; and

(b) a non-electrically conductive spacer (26) placed between and separating said two contacts by a distance corresponding to said predetermined distance of said at least two flexible electrical conductors, said non-electrically conductive spacer having a nose section that intercepts said at least two flexible electrical conductors before said initial engagement of said leading surface portion of said two contacts.

4. The electrical contact as described in claim 3 , wherein said leading surface portion and said trailing surface portion define a contiguous surface.

5. An electrical contact comprising: a leading surface portion (20) for initial sliding engagement of at least one flexible electrical conductor, said leading surface portion comprising a conductive material substrate and a resistive material applied directly to the conductive material substrate; a trailing surface portion (24) for final sliding engagement of said at least one flexible electrical conductor in a fully mated relationship therebetween to produce a relatively low resistance connection, said trailing surface portion being defined by a conductive material .

6. The electrical contact as described in claim 5, wherein said leading surface portion and said trailing surface portion define a contiguous surface.