Patent Application
20120184116
The subject matter herein relates generally to interposers used to connect electronic components.
Various packages or devices exist within the computer industry which require interconnection to a printed circuit board. The devices have lands or balls which are placed on predetermined centerline spacing or pitch, such as 1.0 mm and below. The devices are profiled with arrays of 50 by 50 and even greater. Given the plurality of lands, their centerline spacing, and given the force applied to each land, the devices cause a variety of problems in practice in connection to the printed circuit board.
Sockets exist within the market for the interconnection of such devices, where the sockets include a substrate having contacts terminated to one side of the substrate for connection to the package or device and contacts or balls terminated to the other side of the substrate for connection to the printed circuit board. The contacts have pitches that correspond with the spacing of lands or balls on the device. Attachment of the contacts to the substrate, particularly when the centerline spacing is small, is difficult and time consuming. As the size of contacts decrease to accommodate finer pitches in high density arrays, the amount of material in the contact may not be great enough to support the mechanical requirements, such as normal force and working range of the system. This is especially problematic in contacts formed on pitch out of the available material in the array, as the available material is limited by the space between pitch centers. Traditional methods of contact construction utilize enough material necessary to meet the mechanical and/or electrical requirements of the contact, and then form the material into a shape that will fit within the allowable space within the array. This is commonly done using a bent beam design that often contains features that overlap neighboring contact areas of the array, but don't interfere with their electrical connectivity. When forming the contacts on pitch, only the material in each isolated contact area is available for forming the contact's shape. As pitches in arrays become smaller, the space limitations prevent the use of traditional bent beam designs.
A need remains for an interposer that may be manufactured in a cost effective and reliable manner. A need remains for a mechanically and electrically effective contact for use in an interposer having high density that may be formed on pitch in a cost effective manner.
In one embodiment, an interposer is provided having a substrate having a first surface and a second surface with vias extending between the first and second surfaces. The interposer also includes a contact array mounted to the first surface that has a plurality of coil-shaped contacts. The contacts have heels terminated to corresponding vias. The contacts have beams defining a mating interface of the interposer configured for mating with an electronic component. Optionally, the contacts may be conic helix shaped. The beams may include at least one turn. The beams may be free standing from the heel and may be compressible along contact axes toward the first surface of the substrate.
In another embodiment, an interposer is provided having a thin, flexible substrate having a first surface and a second surface with a thin metal spacer between the first and second surfaces. The interposer also includes a contact array mounted to the first surface that has a plurality of coil-shaped contacts. The contacts have heels terminated to corresponding metal spacer. The contacts have beams defining a mating interface of the interposer configured for mating with an electronic component. Optionally, the contacts may be conic helix shaped. The beams may include at least one turn. The beams may be free standing from the heel and may be compressible along contact axes toward the first surface of the substrate.
In another embodiment, a contact array is provided for an interposer having a substrate. The contact array has a film and a plurality of contacts held by the film. The contacts have heels configured to be terminated to the substrate and beams extending from the heels. The beams are coil-shaped and have pads defining a mating interface of the interposer configured for mating with an electronic component.
In a further embodiment, an interposer is provided having a substrate having a first surface and a second surface with conductors extending between the first and second surfaces. An array of solder balls are soldered to the second surface and are electrically connected to corresponding conductors. A contact array is mounted to the first surface that has a plurality of coil-shaped contacts. The contacts have heels terminated to the first surface and are electrically connected to corresponding conductors. The contacts having coil-shaped beams define a mating interface of the interposer that is configured for mating with an electronic component.
In a further embodiment, an interposer is provided having a substrate having a first surface and a second surface with conductors extending between the first and second surfaces. A first contact array having a plurality of coil-shaped contacts is mounted to the first surface and is electrically connected to corresponding conductors. A second contact array having a plurality of coil-shaped contacts is mounted to the second surface and is electrically connected to corresponding conductors. The contacts having coil-shaped beams define a mating interface of the interposer configured for mating with first and second electronic components.
The subject matter herein relates to interposers, such as a land grid array (LGA) interposer. The interposer is configured to be used to connect two electronic components. For example, the interposer may be used as a chip interconnect for connecting a chip to a printed circuit board. However, it could also mean a board-to-board interconnect. In the illustrated embodiments herein, the subject matter will be described by way of an interconnect to a chip.
The contact array 110 includes a plurality of individual contacts 112, only a portion of which are shown in
The substrate 102 extends between a first side 120 and a second side 122. The contact array 110 is provided along the first side 120. In the illustrated embodiment, the housing 104 is mounted to the first side 120. Alternatively, the housing 104 may surround the substrate 102 such that the substrate 102 is received within the housing 104. The second side 122 is configured to be mounted to another component, such as a printed circuit board (not shown). The second side 122 may be soldered to the printed circuit board using an array of solder balls. Other attachment means are possible in alternative embodiments. In some alternative embodiments, a second contact array may be attached to the second side 120.
The interposer 100 includes a coverlay 126 that is applied over the contact array 110. The coverlay 126 includes openings 128 that fit around the contacts 112 when the coverlay 126 is coupled to the first side 120 of the substrate 102. The coverlay 126 defines a spacer for the contacts 112 so that the contacts 112 do not bottom out against the substrate 102 when the electronic component is coupled to the interposer 100.
The contact heel 140 has an upper surface 146 and a lower surface 148. The upper and lower surfaces 146, 148 are planar and parallel to one another. The lower surface 148 defines a mounting surface for mounting the contact 112 to the substrate 102. In an exemplary embodiment, the lower surface 148 is configured to be soldered to the substrate 102.
In an exemplary embodiment, the beam 142 is a conic helix shaped spring beam. The beam 142 extends a height 150 along a contact axis 152. The beam 142 is coiled around the contact axis 152. The beam 142 is a three-dimensional curve with a continuously varying distance from the axis 152. The beam 142 may have a shape of a logarithmic spiral, an Archimedean spiral, or another spiral shape. The beam 142 may have a constant radius of curvature or a changing radius of curvature. The beam 142 may have any arc length and/or radius of curvature. Optionally, both a radius 154 of the beam 142 and the height 150 of the beam 142 are a continuous monotonic function of an angle 156 from a longitudinal axis 158 of the contact 112. The contact heel 140 extends along the longitudinal axis 158. Optionally, the contact 112 is widest along the longitudinal axis 158.
In an exemplary embodiment, the beam 142 has more than one turn (e.g. extends more than 360°). In the illustrated embodiment, the beam 142 has approximately 2 turns. The beam 142 may have more or less turns in alternative embodiments. In the illustrated embodiment, the contact heel 140 is provided at a radially outer portion of the contact 112 and the pad 144 is provided at a radially inner portion of the contact 112, such that the diameter of the contact 112 increases with the height 150 from the substrate 102 (shown in
In an exemplary embodiment, the contact 112 is manufactured from a conductive material, such as copper or a copper alloy. The contact 112 may be manufactured by forming the beam 142 in a spiral shape from a metal workpiece and then deforming the beam 142 by lengthening the beam 142 along the contact axis 152. For example, the beam 142 may be formed by an etching process, such as a chemical etching process. Alternatively, the beam 142 may be formed by another process, such as a stamping process. The beam 142 may be deformed by pressing or pulling the contact 140 and/or the pad 144 to lengthen the beam 142 along the contact axis 152 (e.g. in the height 150 direction). Portions of the contact 112 may be plated. For example, the pad 144 may be nickel plated. Optionally, the lower surface 148 of the heel 140 may not be plated, but rather may include an organic solderability preservative (OSP) coating.
A solder mask 172 is provided over the second surface 162 and/or a portion of the second pad 170. A solder ball 174 is soldered to the second pad 170. In alternative embodiments, rather than attaching solder balls 174 to the second surface 162, another contact array may be provided on the second surface 162.
A solder mask 176 is provided over the first surface 160 and/or a portion of the first pad 168. Solder 178 is provided between the first pad 168 and the contact 112 to electrically connect the contact 112 to the first pad 168. The contact heel 140 is soldered to the first pad 168 using the solder 178. The contact heel 140 may be attached by other means, such as welding, using conductive epoxy and the like. In other alternative embodiments, rather than mechanically securing the contact heel 140 to the first pad 168, the contact heel 140 may be held in direct physical contact with the first pad 168, such as using a carrier film, where the contacts 112 are laminated to the carrier film and the carrier film is attached to the first surface 160 using adhesive or another securing means. The carrier film holds a plurality of the contacts 112 as a unit such that all of the contacts 112 may be simultaneously mounted to the substrate 102. The compression of the contacts 112 holds the contact heels 140 in engagement with the first pads 168.
The beam 142 extends from the contact heel 140 away from the first surface 160. The beam 142 is deflectable and may be deflected toward the substrate 102 when the electronic component is attached to the interposer 100. The coverlay 126 extends over the substrate 102 and may cover a portion of the contact 112, such as the contact heel 140. The opening 128 is aligned with the beam 142 such that the contact 112 may extend through the coverlay 126. As the electronic component is loaded into the interposer 100, the electronic component engages an outer surface 180 of the coverlay 126 to define a stop for the electronic component. When the electronic component engages the outer surface 180, the beam 142 is positioned within the opening 128 and is in a compressed state.
The contact array 110 includes a carrier film 198 that holds the contacts 112. The carrier film 198 may be laminated to the metal workpiece used to form the contacts 112. Portions of the carrier film 198 may be removed during manufacture, while other portions of the carrier film 198 remain holding the contacts 112 together such that the contact array 110 may be attached to the substrate 102 (shown in
The beams 142 are formed from the material available within a radial area 200 surrounding a central point 202. Optionally, the contact axis 150 (shown in
In the illustrated embodiment, the longitudinal axes 158 are oriented transverse to the columns 190 and rows 192. Optionally, the longitudinal axes 158 are oriented approximately 45° to the columns 190 and the rows 192. The contact heels 140 extend along the longitudinal axes 158. The contact array 110 has tangential areas 204 off to one side of corresponding radial areas 200. The contact heels 140 are formed in the tangential areas 204. The longitudinal axes 158 extend through the tangential areas 204. The tangential areas 204 are provided between radial areas 200 of adjacent contacts 112. For example, because the radial areas 200 are generally circular in shape, “dead zones” are defined between four adjacent contacts 112. The tangential areas 204 extend into corresponding dead zones. By maximizing the size of the radial areas 200 and utilizing the tangential areas 204 between the radial areas 200, usage of the metal material of the workpiece is optimized between the pitch centers. By making the beams 142 as thick as practical, the amount of metal material of the workpiece used for mechanical and electrical integrity is optimized giving the contacts 112 good mechanical strength to withstand the compression and to allow the contacts 112 to impart a normal force on the electrical component to maintain electrical contact therewith.
In an exemplary embodiment, the beam 242 is a conic helix shaped spring beam. The beam 242 extends a height 250 along a contact axis 252. The beam 242 is coiled around the contact axis 252. The beam 242 is a three-dimensional curve with a continuously varying distance from the axis 252. The beam 242 may have a shape of a logarithmic spiral, an Archimedean spiral, or another spiral shape. In the illustrated embodiment, the beam 242 has a constant radius of curvature.
In an exemplary embodiment, the beam 242 has less than one turn (e.g. extends less than 360°). The beam 242 is generally thicker than the beam 142 (shown in
The first contact array 304 includes a plurality of individual coil-shaped contacts 312, which may be the same as or similar to the contacts 112 (shown in
The substrate 302 includes conductive and non-conductive films or layers 320, 322 that are laminated together. Optionally, the contacts 312, 314 may be formed from corresponding conductive layers 320, such as by etching or otherwise removing portions of the conductive layers 320. The contacts 312, 314 are formed on pitch with material available in radial areas of the conductive layers 320 defined between pitch centers. The substrate 302 includes metal spacers that define the conductors 316 through the substrate 302. The conductors 316 extend through the non-conductive layer(s) 322. Optionally, coverlays 324, 326 may be provided on the outer layers of the substrate 302. The contacts 312, 314 extend through the coverlays 324, 326, respectively.
It is to be understood that the above description is intended to be illustrative, and not restrictive. For example, the above-described embodiments (and/or aspects thereof) may be used in combination with each other. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from its scope. Dimensions, types of materials, orientations of the various components, and the number and positions of the various components described herein are intended to define parameters of certain embodiments, and are by no means limiting and are merely exemplary embodiments. Many other embodiments and modifications within the spirit and scope of the claims will be apparent to those of skill in the art upon reviewing the above description. The scope of the invention should, therefore, be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled. In the appended claims, the terms “including” and “in which” are used as the plain-English equivalents of the respective terms “comprising” and “wherein.” Moreover, in the following claims, the terms “first,” “second,” and “third,” etc. 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.
