Patent Application
20080242128
The invention relates generally to electrical contacts, and more particularly, to elastomeric electrical contacts.
Interconnect devices are sometimes used to provide electrical connection between different electrical components, such as, but not limited to, integrated circuits and printed circuit boards, for example when removal, replacement, and/or testing of the electrical components is desired. Many of these electrical components have electrical contacts arranged in a “land grid array” (LGA) which is a two-dimensional array of contact pads. One type of interconnect device, known as an “interposer”, has an array of compressible contacts which is placed between the two opposing arrays of the electrical components to provide an electrical connection between the electrical contacts of the opposing arrays.
Establishing reliable contact between the electrical contacts of the opposing electrical component arrays and the electrical contacts of the interposer may sometimes be difficult due to, for example, height variations between electrical contacts of the opposing electrical component arrays and/or the electrical contacts of the interposer. Variations in thickness and/or warping of any of the substrates supporting the opposing electrical contact arrays and the interposer may also cause difficulty establishing reliable contact. Many interconnect devices use elastomeric electrical contacts that are compressed between the electrical contacts of the opposing electrical component arrays such that the elastomeric electrical contacts apply a mechanical force to the electrical contacts to facilitate establishing and maintaining reliable electrical contact between the opposing electrical component arrays. Compression of the elastomeric electrical contacts also allows for some degree of nonplanarity between, and/or misalignment of, the electrical contacts of the opposing electrical component arrays that may be caused by the warping, variations of height, and/or variations of thickness described above.
Elastomeric electrical contacts typically include an elastomeric body and electrically conducting pathway. Some known elastomeric electrical contacts, sometimes referred to as “filled elastomers”, include an elastomeric body having an interior that is filled with one or more electrically conducting materials. However, filled elastomers may have a limited elastic working range because of the amount of conducting filler needed to reach the percolation threshold and conduct a predetermined amount of electrical current, which may increase contact forces above desired levels. Other known elastomeric electrical contacts include an elastomeric body that includes an electrically conductive pathway formed on an exterior of the elastomeric body. Elastomeric electrical contacts having an electrically conductive pathway on an exterior thereof may have a higher elastic working range than filled elastomeric electrical contacts. However, the electrically conductive pathway may have a lower current carrying capability than filled elastomeric electrical contacts. For example, the dimensions of the electrically conductive pathway may be limited by the desired elastic working range of the elastomeric body. Specifically, if the electrically conductive pathway is formed too large, it may limit the elastic working range of the elastomeric body or the electrically conductive pathway. However, if the conductive pathway is formed too small, it may not carry a desired level of electrical current. Moreover, if formed too small, the conductive pathway may crack and/or fracture during compression of the elastomeric body such that the electrical circuit is broken.
What is needed therefore is an elastomeric electrical contact that has a higher current carrying capability than known elastomeric electrical contacts having exterior electrically conductive pathways while maintaining a predetermined elastic working range without cracking and/or fracture of the pathway.
In one embodiment, an electrical contact is provided that includes an elastomeric body extending between a base portion and a mating end portion. The elastomeric body includes a ledge extending from the mating end portion to the base portion of the elastomeric body. The ledge is defined by a portion of the elastomeric body. An electrically conductive pad extends over at least a portion of the mating end portion. An electrically conductive trace is formed on a surface of the ledge. The electrically conductive trace extends from the mating end portion to the base portion of the elastomeric body. The electrically conductive trace is in electrical contact with the electrically conductive pad for electrically connecting the electrically conductive pad with an electrically conductive element engaging the base portion of the elastomeric body.
In another embodiment, an interposer for electrically connecting a pair of electrical components is provided. The interposer includes a substrate including an electrically conductive element, and an electrical contact mounted on the substrate. The electrical contact includes a first elastomeric portion having a first mating end portion and a first ledge. The first ledge is defined by a portion of the first elastomeric portion. A second elastomeric portion has a second mating end portion and a second ledge. The second ledge is defined by a portion of the second elastomeric portion. First and second electrically conductive pads extend over at least a portion of the first and second mating end portions, respectively. First and second electrically conductive traces are formed on a surface of the first and second ledges, respectively. The first electrically conductive trace is in electrical contact with the first electrically conductive pad and the electrically conductive element. The second electrically conductive trace is in electrical contact with the second electrically conductive pad and the electrically conductive element such that the first and second electrically conductive pads are electrically connected.
In another embodiment, an electrical contact is provided that includes an elastomeric body extending between a base portion and a mating end portion, an electrically conductive pad extending over at least a portion of the mating end portion, the electrically conductive pad comprising a generally planar portion, and an electrically conductive trace formed on an exterior surface of the elastomeric body. The electrically conductive trace extends from the mating end portion to the base portion of the elastomeric body. An exposed surface of the electrically conductive trace faces in a direction generally toward the plane of the generally planar portion of the electrically conductive pad. The electrically conductive trace being in electrical contact with the electrically conductive pad for electrically connecting the electrically conductive pad with a conductive element engaging the base portion of the elastomeric body.
The electrical components 12, 14 may each be any suitable type of electrical component, such as, but not limited to, printed circuit boards, integrated circuits, electrical modules, and/or other electrical devices. The arrays 18, 20 may each be any suitable type of array of electrical contacts that enables operative electrical connection between the electrical components 12, 14, such as, but not limited to, Pin Grid Arrays (PGAs), Land Grid Arrays (LGAs), and/or Ball Grid Arrays (BGAs). Moreover, the arrays 18, 20 may have any suitable configuration, arrangement, and/or pattern of electrical contacts that enables operative electrical connection between the electrical components 12, 14.
Alternatively, the substrate 34 and the electrically conductive elements 44 may have other arrangements and/or configurations besides coated through holes that enable the conductive elements 44 to electrically connect the portions 40 of each elastomeric electrical contact 32. Moreover, although shown as extending over the surfaces 36, 38, the conductive elements 44 may only extend over interior surfaces of the substrate that define the through holes 46.
The conductive elements 44 may be fabricated from any suitable material(s) that enable the conductive elements 44 to function as described herein, such as, but not limited to, copper, aluminum, silver, nickel, palladium, platinum, rhodium, rhenium, tin, and/or gold. Non-noble metals covered with a conductive layer may be used as a base material(s) to provide strength and/or rigidity. Such non-noble metals may be covered with a barrier metal that is covered with a surface structure of a noble metal to ensure chemical inertness and provide suitable asperity distribution to facilitate good metal-to-metal contact. The substrate 34 may be fabricated from any suitable material(s) that enables the substrate 34 to function as described herein, such as, but not limited to polyimide, polyester, epoxy, other materials having a low and uniform dielectric constant, and/or electrically conductive materials, such as, but not limited to, stainless steel. In some embodiments, the substrate 34 is fabricated entirely from one or more materials having a low and uniform dielectric constant (excluding any conducting elements, traces, and the like, e.g., the elements 44 and the traces 48). Alternatively, the substrate 34 is fabricated from one or more conductive materials, such as, but not limited to, stainless steel, that is at least partially covered with one or more materials having a low and uniform dielectric constant. The dielectric properties of the substrate 34 facilitate shielding the electrical contacts 32 from each other. Additionally or alternatively, each electrical contact portion 40 may be at least partially covered by one or more shielding layers of any suitable material(s).
An electrically conductive pad 56 extends over the mating end portion 54 of the elastomeric body 50. The pad 56 engages a corresponding electrical contact 22, 24 of the corresponding array 18, 20, respectively, to electrically connect the electrical contacts 22, 24 with the corresponding electrical contact 32, as will be described below in more detail. The electrically conductive pad 56 may also facilitate preventing siloxane contamination at the interface of the pad 56 and the corresponding electrical contact 22, 24. Although shown as generally planar, the electrically conductive pad 56 may have any suitable shape, whether completely or partially planar, and may cover any portion of the mating end portion 54 of the elastomeric body 50 that enables the conductive pad 56 to function as described herein.
The elastomeric body 50 includes a ledge 58 extending about an exterior thereof. The ledge 58 extends from the mating end portion 54 to the base portion 52 of the elastomeric body 50. An electrically conductive trace 60 is formed on a surface 62 of the ledge 58. The electrically conductive trace 60 extends from the mating end portion 54 to the base portion 52 of the elastomeric body 50. The electrically conductive trace 60 is in electrical contact with the electrically conductive pad 56 at an end 64 thereof. An opposite end 66 of the electrically conductive trace 60 is positioned such that when the base portion 52 of the elastomeric body 50 is engaged with the corresponding conductive element 44, the conductive trace 60 is in electrical contact with the corresponding conductive element 44. Accordingly, when the base portion 52 is engaged with the corresponding conductive element 44, the electrically conductive pad 56 is electrically connected to its corresponding conductive element 44 via the electrically conductive trace 60. The size of the electrically conductive trace 60 may be selected to provide a predetermined current carrying capability as well as provide sufficient support for the trace 60 such that the trace 60 does not crack and/or fracture for a predetermined elastic working range of the elastomeric body 50.
The ledge 58 and the electrically conductive trace 60 may each have any suitable shape and follow any suitable path about the elastomeric body 50 that enables them to function as described herein. In the exemplary embodiment, the ledge 58 and the trace 60 each extend in a generally helical path about the elastomeric body 50. Moreover, in the exemplary embodiment, an exposed surface 68 of the trace 60 faces in a direction generally toward a plane 70 of the generally planar electrically conductive pad 56. The plane 70 of the electrically conductive pad 56 extends, in the exemplary embodiment, generally perpendicularly to a longitudinal axis 72 of the elastomeric body 50. However, in embodiments where the electrically conductive pad 56 does not define a plane that extends generally perpendicularly to the longitudinal axis 72, the trace 60 may face in a direction generally toward a plane (not shown) that extends generally perpendicularly to the longitudinal axis 72.
The electrically conductive trace 60 may be formed on the ledge 58 using any suitable means, method(s), and/or process(es), such as, but not limited to, electroplating, physical vapor deposition, evaporation, sputtering, chemical vapor deposition, and/or direct metal printing. The electrically conductive trace 60 may be fabricated from any suitable material(s) that enable the trace 60 to function as described herein, such as, but not limited to, copper, aluminum, silver, nickel, palladium, platinum, rhodium, rhenium, tin, and/or gold. Non-noble metals covered with a conductive layer may be used as a base material(s) to provide strength and/or rigidity. Such non-noble metals may be covered with a barrier metal that is covered with a surface structure of a noble metal to ensure chemical inertness and provide suitable asperity distribution to facilitate good metal-to-metal contact.
The conductive pad 56 may be fabricated from any suitable material(s) that enable the conductive pad 56 to function as described herein, such as, but not limited to, copper, aluminum, silver, nickel, palladium, platinum, rhodium, rhenium, tin, and/or gold. Non-noble metals covered with a conductive layer may be used as a base material(s) to provide strength and/or rigidity. Such non-noble metals may be covered with a barrier metal that is covered with a surface structure of a noble metal to ensure chemical inertness and provide suitable asperity distribution to facilitate good metal-to-metal contact.
The elastomeric body 50 may be fabricated from any suitable material(s) that enable the elastomeric body 50 to function as described herein, such as, but not limited to, silicone rubber, fluorosilicone rubber, polyepoxide, polyimide, polybutadiene, neoprene, ethylene propylene diene monomer (EPDM), a thermoplastic elastomer, and/or polystyrene. The elastomeric body 50 may have any suitable shape that enables the elastomeric body 50 to function as described herein, such as, but not limited to, a cone, a truncated cone (a frustoconical shape), a pyramid, a truncated pyramid, a prism, and/or a hemisphere. In the exemplary embodiment, the elastomeric body 50 includes a frustoconical shape extending between the mating end portion 54 and the base portion 52.
In the exemplary embodiment, each of the electrical contacts 224 of the circuit board 216 extends through a corresponding through hole 247 within the circuit board 216 such that each contact 224 includes a portion 225 extending along a surface 236 of the circuit board and a portion 227 extending along an opposite surface 238 of the circuit board 216. The elastomeric electrical contacts 232 are mounted directly on the circuit board 216 such that an electrically conductive trace 260 of each contact 232 is in electrical contact with the portion 225 of a corresponding one of the electrical contacts 224 of the circuit board 216. Each trace 260 is also electrically connected to an electrically conductive pad 256 of the contact 232 that is engaged with, and therefore electrically connected to, a corresponding one of the electrical contacts 222 of the electrical component 212. The portions 227 of each of the electrical contacts 224 of the circuit board 216 may be electrically connected to corresponding electrical contacts (not shown) of any other suitable electrical component (not shown), such as, but not limited to, another circuit board, integrated circuits, electrical modules, and/or other electrical devices. Optionally, the elastomeric electrical contacts 232 may each extend through a through hole 246 within the circuit board 216 and include a base portion 252 extending along the surface 238 of the circuit board 216. The base portion 252 may facilitate stabilizing and/or facilitate holding the elastomeric electrical contacts 232 on the circuit board 216.
The embodiments described herein provide an elastomeric electrical contact that may reduce a stress applied to an electrically conductive trace during compression of an elastomeric body of the contact.
Exemplary embodiments are described and/or illustrated herein in detail. The embodiments are not limited to the specific embodiments described herein, but rather, components and/or steps of each embodiment may be utilized independently and separately from other components and/or steps described herein. Each component, and/or each step of one embodiment, can also be used in combination with other components and/or steps of other embodiments. For example, although specific sensor elements are described and/or illustrated with specific attachment devices, each described and/or illustrated sensor element may be used with any of the described and/or illustrated attachment devices as is appropriate. When introducing elements/components/etc. described and/or illustrated herein, the articles “a”, “an”, “the”, “said”, and “at least one” are intended to mean that there are one or more of the element(s)/component(s)/etc. The terms “comprising”, “including” and “having” are intended to be inclusive and mean that there may be additional element(s)/component(s)/etc. other than the listed element(s)/component(s)/etc. Moreover, the terms “first,” “second,” and “third,” etc. in the claims are used merely as labels, and are not intended to impose numerical requirements on their objects. Further, the limitations of the following claims are not written in means—plus-function format and are not intended to be interpreted based on 35 U.S.C. §112, sixth paragraph, unless and until such claim limitations expressly use the phrase “means for” followed by a statement of function void of further structure.
While the invention has been described in terms of various specific embodiments, those skilled in the art will recognize that the invention can be practiced with modification within the spirit and scope of the claims.
