Electrical contact assembly

An electrical contact assembly includes a first electrical contact having a first mating element, and a second electrical contact having a second mating element. The first and second electrical contacts being configured to mate together at the first and second mating elements such that the first and second mating elements engage each other at a contact interface. A distribution of contact pressure across the contact interface at least partially coincides with a distribution of electrical current flow across the contact interface.

BACKGROUND OF THE INVENTION

The subject matter described and/or illustrated herein relates generally to electrical contacts, and more particularly, to an assembly of mated electrical contacts.

Complementary electrical contacts are configured to mate together at a contact interface where mating elements of the complementary electrical contacts engage (i.e., physically contact) each other. Many electrical contact assemblies form a Hertzian style contact interface when the mating elements of the complementary electrical contacts engage each other. Hertzian contact interfaces are formed when the mating element of one of the complementary electrical contacts includes a curved surface that engages a curved or approximately flat surface of the mating element of the other complementary electrical contact. The curved surface(s) deforms slightly under the contact force that holds the mating elements in engagement. For example, a Hertzian style contact interface is formed when a mating element in the form of a spherical protrusion engages an approximately flat (i.e., planar) surface of the mating element of the complementary electrical contact.

Hertzian contact interfaces are not without disadvantages. For example, the mechanical and electrical distributions across the Hertzian contact interface are typically not coincident. Specifically, the regions within the Hertzian contact interface having the greatest mechanical contact pressure (i.e., the greatest normal load or the greatest normal pressure) have different locations within the Hertzian contact interface than the regions within the Hertzian contact interface that carry the greatest amount of electrical current (i.e., the greatest current density). For example, the maximum mechanical contact pressure may be located at the center of the Hertzian contact interface, while the maximum amount of electrical current is distributed across the outer perimeter of the Hertzian contact interface. As a result of the mechanical and electrical distributions not being coincident, only a portion (e.g., a minority) of the area of the Hertzian contact interface is contributing to the flow of electrical current, which may lead to greater overall contact resistance and/or a greater localized thermal response.

Moreover, in situations wherein a shear force is applied to the Hertzian contact interface (e.g., from vibrational and/or thermal effects), mechanical degradation of the Hertzian contact interface will first occur where the lateral deformation is the greatest but the mechanical contact pressure is the lowest. In other words, shear forces may cause the Hertzian contact interface to mechanically degrade (e.g., break, fracture, wear, and/or the like) first at the regions that carry the greatest amount of electrical current, which may reduce the amount of electrical current that is carried by the Hertzian contact interface to fall below desired levels and/or may cause the electrical contacts to completely lose electrical contact therebetween. Shear forces may be especially problematic for Hertzian contact interfaces that are formed from electrical contacts that include non-noble metal coatings (e.g., Sn), which may require a higher normal load to penetrate the inherent oxide film that forms on non-noble metal coatings.

BRIEF DESCRIPTION OF THE INVENTION

In one embodiment, an electrical contact assembly includes a first electrical contact having a first mating element, and a second electrical contact having a second mating element. The first and second electrical contacts being configured to mate together at the first and second mating elements such that the first and second mating elements engage each other at a contact interface. A distribution of contact pressure across the contact interface at least partially coincides with a distribution of electrical current flow across the contact interface.

In another embodiment, an electrical contact assembly includes a first electrical contact having a first mating element, and a second electrical contact having a second mating element. The first and second electrical contacts are configured to mate together at the first and second mating elements such that the first and second mating elements engage each other at a contact interface. The contact interface includes a first asperity junction where the contact interface has the greatest current density and a second asperity junction where the contact interface has the greatest normal load, the first and second asperity junctions at least partially overlapping each other.

In another embodiment, an electrical contact assembly includes a first electrical contact having a first mating element, and a second electrical contact having a second mating element. The first and second electrical contacts are configured to mate together at the first and second mating elements such that the first and second mating elements engage each other at a contact interface. The first mating element and/or the second mating element has a periodic surface topology that includes approximately parallel valleys that are separated by peaks. The first and second mating elements are configured to engage each other at the peaks of the periodic surface topology such that the contact interface is at least partially defined by the peaks.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1is an exploded perspective view of an exemplary embodiment of an electrical contact assembly10.FIG. 2is a cross-sectional view of the electrical contact assembly10. Referring now toFIGS. 1 and 2, the assembly10includes a pair of complementary electrical contacts12and14that mate together to establish an electrical connection therebetween. The electrical contacts12and14may each be a component of any device, such as, but not limited to, an electrical connector (not shown), a printed circuit board (not shown), an electrical wire (not shown), an electrical cable (not shown), an electrical power source (not shown), and/or the like. The electrical contacts12and14may each be referred to herein as a “first” and/or a “second” electrical contact.

The electrical contacts12and14include mating elements16and18, respectively. The electrical contacts12and14mate together at the mating elements16and18. Specifically, the mating elements16and18engage each other to mate the electrical contacts12and14together. The mating elements16and18may be elements of larger segments of the electrical contacts12and14, respectively. For example, the mating elements16and18may be elements of mating segments (e.g., arms, beams, fingers, plugs, receptacles, and/or the like) of the respective electrical contacts12and14. The electrical contacts12and14may include other segments (not shown) in addition to mating segments, such as, but not limited to, mounting segments, termination segments, intermediate segments, housing segments, and/or the like. Each of the mating elements16and18may be referred to herein as a “first” and/or a “second” mating element.

The mating elements16and18engage each other at a contact interface20, which is best seen inFIG. 2and will be described in more detail below. The contact interface20is defined by the surface regions of the mating elements16and18that engage each other. The contact interface20may include one or more segments where the surface regions of the mating elements16and18engage each other. In the exemplary embodiment of the assembly10, the contact interface20is defined by a single continuous segment where the surface regions of the mating elements16and18engage each other. But, in other embodiments, the contact interface20may be defined by two or more discrete segments where the surface regions of the mating elements16and18engage each other.

In the exemplary embodiment of the assembly10, the mating element16of the electrical contact12includes a depression16aand the mating element18of the electrical contact14includes a protrusion18a. The protrusion18ais configured to be partially received into the depression when the mating elements16and18are engaged (i.e., when the electrical contacts12and14are mated together). In the exemplary embodiment of the assembly10, the protrusion18aand the depression16aare each curved and the protrusion18ahas a greater radius of curvature R1than the radius of curvature R2of the depression16a. Accordingly, the protrusion18ais configured to be only partially received within the depression16a. The protrusion18amay be referred to herein as a “curved protrusion”, while the depression16amay be referred to herein as a “curved depression”.

The protrusion18aof the mating element18and the depression16aof the mating element16may each have any respective radius of curvature R1and R2that enables the mating elements18and16to function as described and/or illustrated herein. Moreover, the radius of curvature R1of the protrusion18amay be greater than the radius of curvature R2of the depression16aby any amount that enables the mating elements16and18to function as described and/or illustrated herein.

In the exemplary embodiment of the assembly10, the depression16aand the protrusion18aeach have a spherical shape. Specifically, the depression16aand the protrusion18aeach have the shape of a partial sphere. Although shown as each defining less than half of a sphere, the depression16aand the protrusion18amay each define any other amount (e.g., approximately half) of a sphere. Moreover, the depression16aand the protrusion18amay each have other curved shapes besides spherical shapes, such as, but not limited to, a non-circular shape, an oval shape, a parabolic shape, a curved shape that includes a varying radius of curvature, and/or the like. The depression16amay be referred to herein as a “spherical depression”, while the protrusion18amay be referred to herein as a “spherical protrusion”.

The depression16aincludes a rim22. As will be described below, the rim22defines a portion of the contact interface20. The mating elements16and18of the assembly10define a “rim only” geometry wherein the mating element16only engages the mating element18at the rim22. In other words, the rim22defines the entirety of the portion of the contact interface20that is defined by the mating element16. In the exemplary embodiment of the assembly10, the rim22is circular because the depression16ais spherical. But, the rim22may have other curved shapes (e.g., an oval shape, a parabolic shape, and/or the like). Moreover, the depression16aand the protrusion18aare not limited to curved shapes. Rather, the depression16aand the protrusion18amay each additionally or alternatively include any other shape, such as, but not limited to, rectangular cross-sectional shapes, square cross-sectional shapes, cross-sectional shapes having more than four sides, triangular cross-sectional shapes, and/or the like. The rim22may thus include non-curved shapes (e.g., square shapes, rectangular shapes, triangular shapes, more than four sided shapes, and/or the like) in addition or alternative to one or more curved shapes. In embodiments wherein the depression16aand/or the protrusion18ainclude non-curved shapes, the relative sizes of the depression16aand the protrusion18amay be selected to provide a rim only geometry at the contact interface20.

As best seen inFIG. 2, when the electrical contacts12and14are mated together, the mating elements16and18are engaged at the contact interface20. Specifically, a surface region26of the protrusion18ais engaged with a surface region24of the depression18a. The contact interface20is defined by the surface regions24and26where the depression16aand the protrusion18a, respectively, engage each other. The surface region24of the depression16ais entirely defined by the rim22of the depression16a. The rim22thus defines the portion of the contact interface20that is defined by the depression16asuch that the contact interface is partially defined by the rim22. Because the surface region24of the depression16ais entirely defined by the rim22, the contact interface20has the “rim only” geometry discussed above.

The mating elements16and18may each be formed from any materials. In some embodiments, exterior surfaces of the mating elements16and/or18are defined by non-noble (e.g., Sn) and/or noble metal coatings. Examples of base materials and/or surface coating materials of each of the mating elements16and18include, but are not limited to, noble metals, non-noble metals, copper (Cu), copper alloys, aluminum (Al), aluminum alloys, zinc (Zn), zinc alloys, iron (Fe), iron alloys (including stainless steels), nickel (Ni), nickel alloys, silver (Ag), silver alloys, Bi, Bi alloys, gold (Au), gold alloys, tin (Sn), tin alloys, gold over palladium (Pd), gold over PdNi alloy, gold over NiP alloy, Au/NiP metallurgical combinations (e.g., AgNi, AgW, AgSnO, AgCdO, AgCu, and/or the like) and/or the like. In some embodiments, the mating elements16and18are formed from the substantially the same materials (e.g., have substantially similar surface coatings), while in other embodiments the mating elements16and18are formed from different materials. The mating elements16and18may be formed from any method, process, operation, and/or the like, such as, but not limited to, wire drawing operations and/or the like.

FIG. 3is a plan view of the electrical contact assembly10illustrating the contact interface20. The surface region26of the protrusion18aof the mating element18is engaged with the rim22of the depression16aof the mating element16. The contact interface20may include a distribution of electrical energy and mechanical contact pressure forces along the contact interface20. Such a distribution includes asperity junctions (also commonly referred to as “a-spots”)28where the contact interface20carries the greatest amount of electrical current and asperity junctions30where the contact interface20has the greatest mechanical contact pressure. The amount of electrical current carried by the contact interface may also be referred to herein and commonly as the “current density”, while mechanical contact pressure may be referred to herein and commonly as “normal load” and/or “normal pressure”. Electrical energy may be referred to herein as “electrical current flow”. The mechanical contact pressure acts in the directions of the arrows A and B inFIG. 2.

As can be seen inFIG. 3, the asperity junctions28and the asperity junctions30overlap (i.e., coincide with) each other. Accordingly, the mechanical distribution of mechanical pressure forces along the contact interface20coincides with the electrical distribution of electrical energy along the contact interface20. In other words, the location(s) along the contact interface20where the current density is the greatest (i.e., the asperity junctions28) overlap the location(s) along the contact interface20where the normal pressure is the greatest (i.e., the asperity junctions30).

For example, the asperity junctions28and30may overlap each other because the contact interface20has been more isolated (i.e., localized) to the surface regions24and26as compared to the broader surface areas of Hertzian contact interfaces of similarly sized mating elements. Moreover, because no mechanical contact is present inside the rim22, the outer portion of the contact interface20experiences significantly higher surface pressure values, which results in higher deformation of the asperity junctions28and30and thereby leads to more effective disruption of any surface oxide/contamination films.

In the exemplary embodiment of the assembly10, the asperity junctions28and30entirely overlap each other, such that the asperity junction28does not include any portion that does not overlap the asperity junction30, and vice versa. In other words, the mechanical distribution of mechanical pressure forces along the contact interface20completely coincides with the electrical distribution of electrical energy along the contact interface20. But, in other embodiments, the asperity junctions28and30only partially overlap each other, such that the asperity junction28includes a portion that does not overlap the asperity junction30, and/or vice versa. In other words, the mechanical distribution of mechanical pressure forces along the contact interface20may only partially coincide with the electrical distribution of electrical energy along the contact interface20. The area of the contact interface20, the relative size difference between the protrusion18aand the depression16a(e.g., the difference between the radii of curvature R1and R2), and/or the like may be selected to provide the asperity junctions28and30as at least partially overlapping.

FIG. 4is a cross-sectional view of another exemplary embodiment of an electrical contact assembly50. The assembly50includes a pair of complementary electrical contacts52and54that mate together to establish an electrical connection therebetween. The electrical contacts52and54mate together at respective mating elements56and58thereof that engage each other at a contact interface60to mate the electrical contacts52and54together. The electrical contacts52and54may each be referred to herein as a “first” and/or a “second” electrical contact. Each of the mating elements56and58may be referred to herein as a “first” and/or a “second” mating element.

In the exemplary embodiment of the assembly50, the mating element56of the electrical contact52includes an approximately planar surface56aand the mating element58of the electrical contact54includes a protrusion58a. The protrusion58aincludes a tip72having a depression74extending therein. The depression74includes a rim76. In the exemplary embodiment of the assembly50, the depression74has a spherical shape, but the depression74may have other curved shapes besides spherical shapes, such as, but not limited to, a non-circular shape, an oval shape, a parabolic shape, a curved shape that includes a varying radius of curvature, and/or the like. In the exemplary embodiment of the assembly50, the rim76is circular because the depression74is spherical. But, the rim76may have other curved shapes (e.g., an oval shape, a parabolic shape, and/or the like). Moreover, the depression74and rim76are not limited to curved shapes. Rather, the depression74may additionally or alternatively include any other shape, such as, but not limited to, rectangular cross-sectional shapes, square cross-sectional shapes, cross-sectional shapes having more than four sides, triangular cross-sectional shapes, and/or the like. The rim76may thus include non-curved shapes (e.g., square shapes, rectangular shapes, triangular shapes, more than four sided shapes, and/or the like) in addition or alternative to one or more curved shapes. The protrusion58amay be referred to herein as a “curved protrusion” and/or a “spherical protrusion”. The depression74may be referred to herein as a “spherical depression” and/or a “curved depression”.

When the electrical contacts52and54are mated together, the mating elements56and58are engaged at the contact interface60such that the protrusion58aengages a surface region64of the surface56aof the mating element56at the rim76of the depression74. Specifically, a surface region78of the protrusion58ais engaged with the surface region64of the surface56aof the mating element56. The contact interface20is defined by the surface regions78and64. The surface region78of the protrusion58ais entirely defined by the rim76of the depression74such that the contact interface60has the “rim only” geometry discussed above.

The contact interface60may include a distribution of electrical energy and mechanical pressure forces along the contact interface60. Such a distribution includes asperity junctions68where the contact interface60carries the greatest amount of electrical current and asperity junctions70where the contact interface60has the greatest mechanical contact pressure. The asperity junctions68and the asperity junctions70overlap (i.e., coincide with) each other. Accordingly, the mechanical distribution of mechanical pressure forces along the contact interface60coincides with the electrical distribution of electrical energy along the contact interface60. In the exemplary embodiment of the assembly50, the asperity junctions68and70entirely overlap each other. But, in other embodiments, the asperity junctions68and70only partially overlap each other.

FIG. 5is a perspective view of another exemplary embodiment of an electrical contact assembly110.FIG. 6is a cross-sectional view of the electrical contact assembly110. Referring now toFIGS. 5 and 6, the assembly10includes a pair of complementary electrical contacts112and114that mate together to establish an electrical connection therebetween. The electrical contacts112and114include mating elements116and118, respectively, that engage each other at a contact interface120to mate the electrical contacts112and114together. The electrical contacts112and114may each be referred to herein as a “first” and/or a “second” electrical contact. Each of the mating elements116and118may be referred to herein as a “first” and/or a “second” mating element.

The mating element116of the electrical contact112includes a groove116athat extends a length along the mating element116. The groove116aextends the length along a central longitudinal axis134. The groove116aincludes a rim136that extends along the length of the groove116a. The rim136is defined by opposite rim segments136aand136b. The mating element118of the electrical contact114includes a protrusion118a. The protrusion118ais configured to be partially received into the groove116awhen the mating elements116and118are engaged. In the exemplary embodiment of the assembly110, the protrusion118aand the groove116aare curved. The protrusion118ahas a greater radius of curvature R3than the radius of curvature R4of the groove116a. The protrusion118aand the groove116amay each have any respective radius of curvature R3and R4that enables the mating elements118and116to function as described and/or illustrated herein. Moreover, the radius of curvature R3of the protrusion118amay be greater than the radius of curvature R4of the depression116aby any amount that enables the mating elements116and118to function as described and/or illustrated herein. The protrusion118amay be referred to herein as a “curved protrusion” and/or a “spherical protrusion”, while the groove116amay be referred to herein as a “cylindrical groove”.

The groove116aand the protrusion118amay each have other curved shapes besides the respective cylindrical and spherical shapes shown, such as, but not limited to, a non-circular shape, an oval shape, a parabolic shape, a curved shape that includes a varying radius of curvature, and/or the like. Moreover, the groove116aand the protrusion118aare not limited to curved shapes. Rather, the groove116aand the protrusion118amay each additionally or alternatively include any other shape, such as, but not limited to, rectangular cross-sectional shapes, square cross-sectional shapes, cross-sectional shapes having more than four sides, triangular cross-sectional shapes, and/or the like. In embodiments wherein the groove116aand/or the protrusion118ainclude non-curved shapes, the relative sizes of the groove116aand the protrusion118amay be selected to provide a rim only geometry at the contact interface120.

When the electrical contacts112and114are mated together, a surface region126of the protrusion118ais engaged with the rim136of the groove116a. The contact interface120is defined by the surface regions124and126where the groove116aand the protrusion118a, respectively, engage each other. The surface region124of the groove116ais entirely defined by the rim136, such that the contact interface120has the “rim only” geometry discussed above.

The contact interface120may include a distribution of electrical energy and mechanical pressure forces along the contact interface120. Such a distribution includes asperity junctions128where the contact interface120carries the greatest current density and asperity junctions130where the contact interface120has the greatest normal pressure. As best seen inFIG. 5, the asperity junctions128and the asperity junctions130overlap each other such that the mechanical distribution of normal pressure forces along the contact interface120coincides with the electrical distribution of electrical energy along the contact interface120. In the exemplary embodiment of the assembly110, the asperity junctions128and130entirely overlap each other. But, in other embodiments, the asperity junctions128and130only partially overlap each other.

FIG. 7is a perspective view of another exemplary embodiment of an electrical contact assembly150.FIG. 8is a cross-sectional view of the electrical contact assembly150. The assembly150includes a pair of complementary electrical contacts152and154having respective mating elements156and158that engage each other at a contact interface160to mate the electrical contacts152and154together. The electrical contacts152and154may each be referred to herein as a “first” and/or a “second” electrical contact. Each of the mating elements156and158may be referred to herein as a “first” and/or a “second” mating element.

The mating element156includes an approximately planar surface156aand the mating element158includes a protrusion158a. The protrusion158aincludes a tip172having a groove174extending a length along the tip172. The groove174includes a rim176that extends along the length of the groove and is defined by opposite rim segments176aand176b. In the exemplary embodiment of the assembly150, the groove174has a cylindrical shape, but the groove174may have other curved shapes besides cylindrical shapes, such as, but not limited to, a non-circular shape, an oval shape, a parabolic shape, a curved shape that includes a varying radius of curvature, and/or the like. Moreover, the groove174is not limited to curved shapes. Rather, the groove174may additionally or alternatively include any other shape, such as, but not limited to, rectangular cross-sectional shapes, square cross-sectional shapes, cross-sectional shapes having more than four sides, triangular cross-sectional shapes, and/or the like. The protrusion158amay be referred to herein as a “curved protrusion” and/or a “spherical protrusion”. The groove174may be referred to herein as a “cylindrical groove”.

When the electrical contacts152and154are mated together, the mating elements156and158are engaged at the contact interface160such that the protrusion158aengages a surface region164of the surface156aof the mating element156at the rim176of the groove174. Specifically, a surface region178of the protrusion158ais engaged with the surface region164of the surface156aof the mating element156. The contact interface160is defined by the surface regions178and164. The surface region178of the protrusion158ais entirely defined by the rim176of the depression174such that the contact interface160has the “rim only” geometry discussed above.

The contact interface160may include a distribution of electrical energy and mechanical pressure forces along the contact interface160. Such a distribution includes asperity junctions168where the contact interface160carries the greatest amount of electrical current and asperity junctions170where the contact interface160has the greatest mechanical contact pressure. The asperity junctions168and the asperity junctions170overlap each other. Accordingly, the mechanical distribution of mechanical pressure forces along the contact interface160coincides with the electrical distribution of electrical energy along the contact interface160. In the exemplary embodiment of the assembly150, the asperity junctions168and170entirely overlap each other. But, in other embodiments, the asperity junctions168and170only partially overlap each other.

FIG. 9is a perspective view of another exemplary embodiment of an electrical contact assembly210.FIG. 10is a cross-sectional view of the electrical contact assembly210. The assembly210includes a pair of complementary electrical contacts212and214that include respective mating elements216and218that engage each other at a contact interface220to mate the electrical contacts212and214together. The electrical contacts212and214may each be referred to herein as a “first” and/or a “second” electrical contact. Each of the mating elements216and218may be referred to herein as a “first” and/or a “second” mating element. The protrusion218amay be referred to herein as a “curved protrusion” and/or a “spherical protrusion”.

The mating element218of the electrical contact214includes a protrusion218a. The mating element216of the electrical contact212includes a mating side216ahaving a periodic surface topology240that includes valleys242that are separated by peaks244that are associated with the valleys242. Specifically, the valleys242extend lengths along the periodic surface topology240. The lengths of the valleys242extend approximately parallel to each other along the periodic surface topology240. The peaks244extend lengths between the valleys242such that adjacent valleys242are separated by an associated peak244that extends therebetween.

When the electrical contacts212and214are mated together, the protrusion218ais engaged with the mating side216aof the mating element216at the peaks244of the periodic surface topology240of the mating side216a. Specifically, a surface region226of the protrusion218ais engaged with a surface region224of the mating side216athat is entirely defined by the peaks244. Although two peaks244are shown as engaged with the protrusion218a, the surface region224may include any number of peaks244engaged with the surface region226of the protrusion218a. The contact interface220is defined by the surface regions224and226. Accordingly, the peaks244of the mating element216that are engaged with the protrusion218apartially define the contact interface220.

The contact interface220includes asperity junctions228where the contact interface220carries the greatest current density and asperity junctions230where the contact interface220has the greatest normal pressure. As shown herein, the asperity junctions228and the asperity junctions230overlap each other such that the mechanical distribution of normal pressure forces along the contact interface220coincides with the electrical distribution of electrical energy along the contact interface220. In other words, the location(s) along the contact interface220where the current density is the greatest (i.e., the asperity junctions228) overlap the location(s) along the contact interface220where the normal pressure is the greatest (i.e., the asperity junctions230). For example, the asperity junctions228and230may overlap each other because the contact interface220has been more isolated (i.e., localized) to the surface regions224and226as compared to the broader surface areas of Hertzian contact interfaces of similarly sized mating elements. Moreover, using a periodic surface topology may create a low resistance contact that is nearly invariant against lateral position.

In the exemplary embodiment of the assembly210, the asperity junctions228and230entirely overlap each other such that the mechanical distribution of normal pressure forces along the contact interface220completely coincides with the electrical distribution of electrical energy along the contact interface220. But, in other embodiments, the asperity junctions228and230only partially overlap each other.

The area of the contact interface220, the width W (FIG. 10) of the valleys242(i.e., the sinus wavelength of the periodic surface topology240), the height H of the peaks244, and/or the like may be selected to provide the asperity junctions228and230as at least partially overlapping (i.e., at least partially coincident). For example, the width W of the valleys242may be selected as less than approximately 0.8 times the radius of curvature R5of the protrusion218aand greater than approximately 0.2 times the radius of curvature R5of the protrusion218a, wherein the height H of the peaks244(i.e., twice the sinus amplitude of the periodic surface topology240) is selected as greater than approximately 3% of the width W of the valleys242. The sinus amplitude of the periodic surface topology240may be determined, for example, from a contact area using the equation:
1/r=1/r1L+1/r1Q+1/r2L+1/r2Q,

where r is radius, 1 is the mating element216, 2 is the mating element218, L is the length radius, and Q is the cross radius. For example,FIG. 10illustrates the case of a protrusion218ahaving a radius of curvature of approximately 1.5 mm. InFIG. 10, the width W of the valleys242is selected as approximately 0.2 times the radius of curvature of the protrusion218a, or approximately 0.3 mm, which gives a sinus amplitude of approximately 9 μm.FIG. 11illustrates another embodiment of a protrusion318ahaving a radius of curvature of approximately 1.5 mm. InFIG. 11, the width W1of the valleys342of a periodic surface topology340of a mating element316is selected as approximately 0.8 times the radius of curvature of the protrusion318a, or approximately 1.2 mm, which gives a sinus amplitude of approximately 36 μm. The mating element316may be referred to herein as a “first” and/or a “second” mating element. The protrusion318amay be referred to herein as a “curved protrusion” and/or a “spherical protrusion”.

Referring again toFIGS. 9 and 10, an additional applied “roughness” profile (not shown) is optionally superimposed onto the periodic surface topology240of the mating side216aof the mating element216. In some embodiments, such a roughness profile does not deviate more than approximately 38% from the height H of the peaks244and/or from the width W of the valleys242. In other words, such a roughness profile may not deviate more than 385 from the sinus wavelength and/or from twice the amplitude of the periodic surface topology240.

Although only the mating side216aof the mating element216is shown as including the periodic surface topology240, in other embodiments, the protrusion218aof the mating element218may include a periodic surface topology in addition or alternative to the periodic surface topology240of the mating side216aof the mating element216. In embodiments wherein both the protrusion218aof the mating element218and the mating side216aof the mating element216include periodic surface topologies, the periodic surface topologies may be angled at any angle with respect to each other when the mating elements216and218are engaged. Specifically, the lengths of the valleys242of the periodic surface topology240of the protrusion218amay extend at any angle relative to the valleys (not shown) of the periodic surface topology (not shown) of the mating side216aof the mating element216. In some embodiments, the periodic surface topologies of the protrusion218aand the mating side216awill be oriented approximately perpendicular to the each other when the mating elements216and218are mated together. In other embodiments, the periodic surface topologies of the protrusion218aand the mating side216aare oriented approximately parallel or at an oblique angle relative to each other when the mating elements216and218are mated together. In embodiments wherein the periodic surface topologies of the protrusion218aand the mating side216aare oriented approximately parallel, the sinus wavelengths of the periodic surface topologies may be selected as approximately the same. A perfectly aligned pair of peaks from the mating elements216and218may create the most coincidence between the asperity junctions228and230. In embodiments wherein the periodic surface topologies of the protrusion218aand the mating side216aare not oriented approximately parallel, the sinus wavelengths of the periodic surface topologies may be different or approximately the same.

FIG. 12is a perspective view of another exemplary embodiment of an electrical contact assembly410illustrating an embodiment wherein a protrusion418ahas a periodic surface topology440. The assembly410includes a pair of complementary electrical contacts412and414that include respective mating elements416and418that engage each other at a contact interface420to mate the electrical contacts412and414together. The electrical contacts412and414may each be referred to herein as a “first” and/or a “second” electrical contact. Each of the mating elements416and418may be referred to herein as a “first” and/or a “second” mating element.

The mating element416of the electrical contact412includes an approximately planar surface416a. The mating element418of the electrical contact414includes a protrusion418a. The protrusion418ahas the periodic surface topology440, which includes valleys442that are separated by peaks444that are associated with the valleys442. The protrusion418amay be referred to herein as a “curved protrusion” and/or a “spherical protrusion”.

When the electrical contacts412and414are mated together, the protrusion418ais engaged with the approximately planar surface416aat the peaks444of the periodic surface topology440of the protrusion418a. Specifically, a surface region426of the protrusion418athat is entirely defined by the peaks444is engaged with the approximately planar surface416aat a surface region424of the surface416a. Although two peaks444are shown as engaged with the surface416a, the surface region426may include any number of peaks444engaged with the surface region224of the surface416a. The contact interface420is defined by the surface regions424and426, such that the peaks444of the mating element416that are engaged with the protrusion418adefine a portion of the contact interface420.

The contact interface420includes asperity junctions428where the contact interface420carries the greatest current density and asperity junctions430where the contact interface420has the greatest normal pressure. The asperity junctions428and the asperity junctions430at least partially overlap each other such that the mechanical distribution of normal pressure forces along the contact interface420at least partially coincides with the electrical distribution of electrical energy along the contact interface420.

FIG. 13is a perspective view of another exemplary embodiment of an electrical contact assembly510illustrating an embodiment wherein a mating element516having a concave shape includes a periodic surface topology540. The assembly510includes a pair of complementary electrical contacts512and514that include respective mating elements516and518that engage each other at a contact interface520to mate the electrical contacts512and514together. The electrical contacts512and514may each be referred to herein as a “first” and/or a “second” electrical contact. Each of the mating elements516and518may be referred to herein as a “first” and/or a “second” mating element.

The mating element518of the electrical contact514includes a protrusion518a. The mating element516of the electrical contact512includes a mating side516ahaving a concave shape. The mating side516aof the mating element516includes the periodic surface topology540, which includes valleys542that are separated by associated peaks544. The protrusion518amay be referred to herein as a “curved protrusion” and/or a “spherical protrusion”.

When the electrical contacts512and514are mated together, the protrusion518ais engaged with the mating side516aat the peaks544of the periodic surface topology540of the mating side516a. Specifically, a surface region526of the protrusion518ais engaged with a surface region524of the mating side516athat is entirely defined by the peaks544. Although two peaks544are shown as engaged with the protrusion518a, the surface region524may include any number of peaks544engaged with the surface region526of the protrusion518a. The contact interface520is defined by the surface regions524and526such that the peaks544of the mating element516that are engaged with the protrusion518apartially define the contact interface520.

The contact interface520includes asperity junctions528where the contact interface520carries the greatest current density and asperity junctions530where the contact interface520has the greatest normal pressure. The asperity junctions528and the asperity junctions530at least partially overlap each other such that the mechanical distribution of normal pressure forces along the contact interface520at least partially coincides with the electrical distribution of electrical energy along the contact interface520.

FIG. 14is a perspective view of another exemplary embodiment of an electrical contact assembly610illustrating an embodiment wherein both mating elements616and618include periodic surface topologies640and740, respectively. The assembly610includes a pair of complementary electrical contacts612and614that include the respective mating elements616and618, which engage each other at a contact interface620to mate the electrical contacts612and614together. The electrical contacts612and614may each be referred to herein as a “first” and/or a “second” electrical contact. Each of the mating elements616and618may be referred to herein as a “first” and/or a “second” mating element.

The mating element618of the electrical contact614includes a protrusion618a. The mating element616of the electrical contact612includes a mating side616ahaving a concave shape. The mating side616aof the mating element516and the protrusion include the periodic surface topologies640and740, respectively. The periodic surface topologies640and740include respective valleys642and742that are separated by associated peaks644and744, respectively. The protrusion618amay be referred to herein as a “curved protrusion” and/or a “spherical protrusion”.

When the electrical contacts612and614are mated together, the protrusion618ais engaged with the mating side616asuch that the peaks644of the periodic surface topology640of the mating side516aare engaged with the peaks744of the periodic surface topology740of the protrusion618a. Specifically, a surface region626of the protrusion518athat is entirely defined by the peaks744is engaged with a surface region624of the mating side616athat is entirely defined by the peaks644. In the exemplary embodiment of the assembly610, the periodic surface topologies644and744are oriented approximately perpendicular to each other. Specifically, the valleys644of the periodic surface topology640are oriented approximately perpendicular to the valleys744of the periodic surface topology740. Although two peaks644are shown as engaged with two peaks744, any number of the peaks644may be engaged with any number of the peaks744. The contact interface620is defined by the surface regions624and626such that the peaks644and744define the contact interface520.

The contact interface620includes asperity junctions628where the contact interface620carries the greatest current density and asperity junctions630where the contact interface620has the greatest normal pressure. The asperity junctions628and the asperity junctions630at least partially overlap each other such that the mechanical distribution of normal pressure forces along the contact interface620at least partially coincides with the electrical distribution of electrical energy along the contact interface620.

The various electrical contact assembly embodiments described and/or illustrated herein may provide contact interfaces where the asperity junctions within the contact interface that carry the greatest current density overlap (i.e., coincide with) the asperity junctions within the contact interface that have the greatest normal pressure. The coincidence of the asperity junctions that carry greatest current density and the asperity junctions that have the greatest normal pressure may result in a lower contact resistance of the electrical contacts of the assembly and/or may lead to the electrical contacts having lower normal forces, for example as compared to electrical contact assemblies having Hertzian type contact interfaces. Moreover, The coincidence of the asperity junctions that carry greatest current density and the asperity junctions that have the greatest normal pressure may result in less localized thermal response, for example as compared to electrical contact assemblies having Hertzian type contact interfaces. Technical effects of the various embodiments may include, but are not limited to, reducing contact resistance, reducing normal forces, and/or reducing localized thermal responses. The reduction of contact resistance and/or normal forces may be best for mating elements that engage each other at non-noble metal finished surfaces. A lesser effect may be seen when mating more noble metal finished surfaces. The reduction of contact resistance and/or normal forces may be seen both when the mating elements have substantially the same materials at the contact interface (e.g., when mating like finishes) and when the mating elements have different materials at the contact interface (e.g., when mating different finishes).