# Patent

## Title
Low profile electrical interconnect with fusion bonded contact retention and solder wick reduction

## Abstract

An electrical interconnect and a method of making the same. A plurality of contact members are located in through holes in a substrate so distal portions of the contact members extend above a first surface of the substrate in a cantilevered configuration and proximal portions of the contact members are accessible along a second surface of the substrate. A flowable polymeric material located on the second surface of the substrate is fusion bonded to the proximal portions of the contact members so the flowable polymeric material substantially seals the through holes in the substrate. An insulator housing is bonded to the first surface of the substrate with the distal portions of the contact members located in through holes in an insulator housing, so the distal portions are accessible from a second surface of the insulator housing.

## Background
CROSS-REFERENCE TO RELATED APPLICATIONS
This application claims the benefit of U.S. Provisional Application No. 62/134,810, filed Mar. 18, 2015 and U.S. Provisional Application No. 62/146,550, filed Apr. 13, 2015, the disclosure of which are hereby incorporated by reference.


TECHNICAL FIELD
The present disclosure relates to a low-profile electrical interconnector with contact members fusion bonded to a substrate that forms a seal around the contact member to reduce solder wicking. The substrate is bonded to an insulator housing so distal portions of the contact members are located in through holes.
BACKGROUND OF THE INVENTION
Traditional IC sockets are generally constructed of an injection molded plastic, insulator housing that includes stamped and formed copper alloy contact members stitched or inserted into recesses. The assembled IC socket is then generally processed through a reflow oven to attach solder balls to the contact members.
During final assembly the contact pads on the printed circuit board (“PCB”) are printed with solder paste or flux and the solder balls on the IC socket are placed in registration with the contact pads. The assembly is then reflowed and the solder balls essentially weld the IC socket to the PCB.
During use, an IC socket receives an IC device, such as a packaged integrated circuit. The contact members electrically couple the terminals on the IC device with the corresponding terminal on the PCB. The terminals on the IC device are typically held against the contact members by applying a load, which is expected to maintain intimate contact and reliable circuit connection throughout the life of the system without a permanent connection. As a result, the IC device can be removed or replaced without the need for reflowing solder connections.
These types of IC sockets and interconnects have been, produced in high volume for many years. As IC devices advance to next generation architectures traditional. IC sockets, have reached mechanical and electrical limitations that require alternate methods.
As processors and systems have evolved, several factors have impacted the design of traditional IC sockets. Increased terminal counts, reductions in the distance between the contacts known as terminal pitch, and signal integrity have been main drivers that impact the socket and contact design. As terminal counts go up, the IC package essentially gets larger due to the additional space needed for the terminals. As the package grows larger, costs go up and the relative flatness of the package and corresponding PCB require compliance between the contact and the terminal pad to accommodate the topography differences and maintain reliable, connection.
Package producers tend to drive the terminal pitch smaller so they can reduce the size of the package as well as the flatness effects. As the terminal pitch reduces, the available area to place a contact is also reduced, which limits the space available to locate a spring or contact member which can deflect without touching a neighbor. In order to maximize the length of the spring so that it can deflect the proper amount without damage, the thickness of the insulating walls within the plastic housing is reduced which increases the difficulty of molding as well as the latent stress in the molded housing, resulting in warpage during the heat applied during solder reflow. For mechanical reasons, the contact designs desire to have a long contact that has the proper spring properties. Long contact members tend to reduce the electrical performance of the connection by creating a parasitic effect that impacts the signal as, it travels through the contact. Other effects such as contact resistance impact the self-heating effects as current passes through power delivering contacts, and the small space between contacts can cause distortion as a nearby contact influences the neighbor which is known as cross talk. Traditional socket methods are able to meet the mechanical compliance requirements of today's needs, but they have reached an electrical performance limit.
Traditional sockets are manufactured from bulk plastic material that is machined to, provide device location features as well as positions for the electrical contacts that can be stamped and formed, blanked, wire electro-discharge machining processed, or constructed from conductive elastomer, coil spring probes, or several variations. The predominant contact type used in sockets is the spring probe, which basically consists of two or more metal members that engage each other to create the electrical path biased by a coil spring that provides normal and return force.
Traditional electrical contacts are press fit into the insulator housing. A polymer in the insulator housing is displaced during insertion to create an interference fit which holds the electrical contact in position. In some cases a flowable elastomeric material is dispensed onto the surface of the insulator, which flows into the insulator housing near the electrical contacts. When cured the flowable material holds the electrical contact in position.
Next generation systems will operate above 5 GHz and beyond and the existing interconnects will not achieve acceptable performance levels without significant revision. A major issue with the use of spring probes in sockets is the electrical performance is degraded by the coil spring which is an inductor, as well as the potential capacitance of the metal members and the relatively high contact resistance due to the various sliding connection point.
BRIEF SUMMARY OF THE INVENTION
The present disclosure is directed to a method of making an electrical interconnector. A plurality of contact members are positioned in through holes in a substrate so distal portions of the contact members extend above a first surface of the substrate in a cantilevered configuration and proximal portions of the contact members are accessible along a second surface of the substrate. A flowable polymeric is located on the second surface of the substrate adjacent the through holes. The substrate and the contact members are subject to sufficient energy and/or pressure so the flowable polymeric layer flows into engagement with the proximal portions of the contact members and fuses the contact members to the substrate. Distal portions of the contact members are positioned in through holes in an insulator housing. The first surface of the substrate is bonded to a first surface of the insulator housing so the distal portions are accessible from a second surface of the insulator housing.
The flowable polymeric material is fused to the contact members and substantially seals the through holes in the substrate. In one embodiment, distal portions of the contact members are formed with a plurality of beams maintained in a cantilevered relationship with respect to the first surface of the substrate. The beams elastically deform or flex to mechanically and electrically engage with terminals on circuit members.
The flowable polymeric material can be a layer positioned on the second surface of the substrate. The flowable polymeric material is then processed to reveal the proximal portions of the contact members, such as by imaging, or laser drilling. Alternatively, the flowable polymeric material is molded or deposited on the second surface of the substrate adjacent the through holes. The flowable polymeric material can be a low melt liquid crystal polymer, an epoxy set resin, a thermoset material, or a thermoplastic material.
In one embodiment, the substrate is formed from a first polymeric material have a first glass transition temperature and the flowable polymeric material from a second polymeric material have a second glass transition temperature. The second glass transition temperature is lower than the first glass transition temperature. The substrate and the contact members are, subjected to sufficient energy and/or pressure so the second glass transition temperature of the flowable polymeric material is exceeded, but the first glass transition temperature is not exceeded, so that the flowable polymeric material enters a molten or rubber-like state and flows into engagement with proximal portions of the contact members.
In one embodiment, the method includes electrically coupling proximal portions of the contact members to contact pads on a first circuit member. Terminals on a second circuit member are positioned in the through holes along the second surface of the insulator housing, and mechanically and electrically coupled to the distal portions of the contact members.
In another embodiment, solder ball terminals on a BGA device are positioned in the through holes along the second surface of the insulator housing. The distal portions of the contact members are elastically deformed or flex to mechanically and electrically engage with the solder ball terminals on the BGA device.
The present disclosure is also directed to an electrical interconnector. A plurality of contact members are located in through holes in a substrate so distal portions of the contact members extend above a first surface of the substrate in a cantilevered configuration and proximal portions of the contact members are accessible along a second surface of the substrate. A flowable polymeric material located on the second surface of the substrate is fusion bonded to the proximal portions of the contact members so the flowable polymeric material substantially seals the through holes in the substrate. An insulator housing is bonded to the first surface of the substrate with the distal portions of the contact members located in through holes in an insulator housing, so the distal portions are accessible from a second surface of the insulator housing.
In one embodiment, the distal portions of the contact members include a plurality of beams maintained in a cantilevered relationship with respect to the first surface of the substrate. The beams elastically deform or flex to mechanically and electrically engage with terminals on a circuit member.
In one embodiment, the substrate is formed from a first polymeric material have a first glass transition temperature and the flowable polymeric material from a second polymeric material have a second glass transition temperature, wherein the second, glass transition temperature is lower than the first glass transition temperature.
The present disclosure is also directed to an electrical assembly including contact pads on a first circuit member electrically coupled proximal portions of the contact members. Terminals on a second circuit member are positioned in the through holes along the second surface of the insulator housing, and mechanically and electrically coupled with distal portions of the contact members.
In an alternate embodiment, the electrical assembly includes solder ball terminals on a BGA device positioned in the through holes along the second surface of the insulator housing. The distal portions of the contact members are mechanically and electrically coupled with the solder ball terminals on the BGA device.
The contact members can be stamped, formed, etched or fabricated from conventional means and assembled loose or retained on a strip until they are removed and installed. The contact members can be of virtually any size and shape. The insulator housing can be constructed with a variety of techniques, such as injection molding, laminated in layers using traditional circuit board fabrication techniques, printed by depositing polymers in desired locations, or a combination thereof.



BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING
FIGS. 1A and 1B are cross sectional views of a multi-layered insulator housing for an electrical connector with a flowable contact retention region in accordance with an embodiment of the present disclosure.
FIGS. 2A and 2B are cross sectional views of an alternate multi-layered insulator housing for an electrical connector with a flowable contact retention region in accordance with an embodiment of the present disclosure.
FIG. 3 is a cross sectional view of a molded insulator housing for an electrical connector with a flowable contact retention region in accordance with an embodiment of the present disclosure.
FIG. 4 is a cross sectional view of an insulator housing for an electrical connector with a printed flowable contact retention region in accordance with an embodiment of the present disclosure.
FIGS. 5A and 5B are cross sectional views of a multi-layered insulator housing for an electrical connector with a plurality of flowable contact retention regions in accordance with an embodiment of the present disclosure.
FIG. 6A-6B are cross sectional views of spring contact members in an electrical connector with a plurality of flowable contact retention regions in accordance with an embodiment of the present disclosure.
FIGS. 7A and 7B are exploded views of a socket with a flowable contact retention region in accordance with an embodiment of the present disclosure.
FIG. 7C is a side sectional view of the socket of FIG. 7A.
FIG. 7D is a perspective view of an array of contacts for use in the socket of FIG. 7A.
FIGS. 7E-7G illustrate alternate contacts suitable for use in the socket of FIG. 7A.
FIG. 7H is a side view of an electrical interconnect with electroplated terminals coupled to a BGA device engaged with the socket of FIG. 7A in accordance with an embodiment of the present disclosure.
FIG. 8 is a cross sectional, view of an insulator housing for an electrical connector with a flowable contact retention region in accordance with an embodiment of the present disclosure.
FIG. 9 is a cross sectional view of an insulator housing for an electrical connector with a printed flowable contact retention region in accordance with an embodiment of the present disclosure.



DETAILED DESCRIPTION OF THE INVENTION
FIGS. 1A and 1B are sectional views of an electrical connector 50 in accordance with an embodiment of the present disclosure. Insulator housing 52 is constructed with a plurality of layers 54A, 54B, 54C, 54D, 54E (“54”). In one embodiment, the layers 54 are discrete layers bonded using a variety of techniques, such as adhesive bonding, ultrasonic or solvent welding, and other techniques known to those in the art. In another embodiment, some of the layers can be molded or machined as a subassembly.
A plurality of through holes 56 are formed in the insulator housing 52 to receive contact members 58. The through holes 56 and contact members 58 are arranged to correspond with terminals 60 on first circuit member 62 and contact pads 64 on second circuit device 66. In the embodiment illustrated in FIG. 1B the terminals 60 are solder balls and the first circuit member 62 is an integrated circuit device. The second circuit member 66 is a PCB.
The layers 54 of the insulator housing 52 can be constructed from a variety of materials, as polyimide or liquid crystal polymer. If the electrical connector 50 is a rigid structure, one or more of the layers 54 can be FR4 or one of many high speed laminates or substrates. If the electrical connector 50 is a semiconductor package, one of the layers 54 can be a material such as FR4, BT resin of any one of a variety of laminate or substrate materials.
The contact members 58 are preferably sized to loosely fit in the through holes 56. The loose-fit arrangement permits vibratory insertion or high speed stitching. The contact members 58 are preferably beam structures with first end portions 70 locating near first surface 72 of the insulator housing 52 and second end portions 74 located near a second surface 76 of the insulator housing 52.
In the illustrated embodiment, layer of a flowable polymeric material 92 is located between layers 54D and 54E in retention region 83. The layer of a flowable polymeric material 92 can be constructed from a thermoplastic material, an epoxy set resin, a low-melt liquid crystal polymer, a thermoset resin, and a variety of other polymeric materials. As best illustrated in FIG. 1B, the flowable material 92 is plastically deformed by applying energy and/or pressure to the electrical connector 50. The energy can be, for example, heat, ultrasonic stimulation, infrared RF, or some combination thereof. Pressure 61 is also preferably applied to facilitate the flow of the flowable polymeric material 92 into engagement with the contact members 58. By controlling the quantity and, duration of energy applied to the electrical connector 50 it is possible to form seal 93 around the contact member 58 in the engagement region 83, without compromising the structural integrity of the insulator housing 52. The seal 93 serves to both retain the contact member 58 in the insulator housing 52 and reduce solder 80 from wicking into the through holes 56.
In the illustrate embodiment, the flowable material 92 engages with retention features 82 on the contact members 58. The retention features 82 reduce the gap between the flowable material 92 and the contact members 58 created by the through holes 56.
Locating retention region 83 near the second surface 76 of the insulator housing 52 maintains the first end, portions 70 of the contact members 58 in a free-floating or cantilevered configuration. Main beams 78 of the contact members 58 are configured to flex within the through holes 56 when terminals 60 are compressively engaged with the first, end portions 70. Gap 86 is maintained between the layer 54D and the contact members 58 in the region 84. Solder balls 80 on second end portions 74 of the contact members 58 serve to electrically and mechanically couple the contact members 58 to the contact pads 64 on the second circuit member 66.
In one embodiment, the layers 54 are constructed from a first polymeric material have a first glass transition temperature and the layer of a flowable polymeric material 92 is preferably constructed from a second flowable polymeric material with a second glass transition temperature that is lower than the first glass transition temperature. After the contact members 58 are loosely positioning within the through holes 56, the electrical connector 50 is subjected to sufficient energy and/or pressure so the second glass transition temperature of the layer of a flowable polymeric material 92 is exceeded, but the first glass transition temperature of the first polymeric material is not exceeded. As best illustrated in FIG. 1B, when the layer of a flowable, polymeric material 92 is in the glass transition state it flows into engagement with retention features 82 on the contact members 58 in retention region 83 on the insulator housing 52.
The glass-liquid transition or glass transition short is the reversible transition in amorphous materials (or in amorphous regions within semi crystalline materials) from a hard and relatively brittle “glassy” state into a molten or rubber-like state, as the temperature is increased. The reverse transition, achieved by cooling the viscous liquid into the glass state, is referred to as vitrification. The glass-transition temperature (Tg) of a material characterizes the range of temperatures over which this glass transition occurs. The glass transition temperature is always lower than the melting temperature (Tm) of the crystalline state of the material, if one exists.
Once the electrical connector 50 is cooled so the layer of a flowable polymeric material 92 is below the second glass transition temperature, the layer of a flowable polymeric material 92 resumes the glass state (i.e., vitrification) and securely retain the contact members 58 in the through holes 56. In one embodiment, the layer of a flowable polymeric material 92 preferably substantially surrounds the contact member 58 to prevent wicking of the solder 80 into the insulator housing 52.
After heat-cycling and cooling the flowable polymeric material 92, the contact members 58 are fused to the retention region 83. As used herein, “fused” or “fusing” refers to bonding or joining a component to a polymeric material by subjecting the polymeric material to sufficient energy and/or pressure to cause the materials to bond together. In some embodiments, fusing requires the glass transition temperature of the polymeric material to be temporarily exceeded.
By locating retention region 83 near the second surface 76 of the insulator housing 52, first end portions 70 of the contact members 58 are maintained in a cantilevered relationship with respect to the first surface 72. Compressively engaging the first circuit member 62 against the electrical connector 50 in direction 94 causes the terminals 60 to flex elastically the first end portions 70 of the contact members 58, primarily along the main beams 78, in direction 96 to form a compressive electrical connection between the first end portions 70 and the terminals 60.
In one embodiment, the flowable polymeric material 92 is a low temperature LCP. LCP's are a class of aromatic polyester polymers that are extremely unreactive and inert so as to be useful for electrical applications. Liquid crystal polymers are a rod-like molecular structure, rigidness of the long axis, and strong dipoles and/or easily polarizable substituents. The distinguishing characteristic of the liquid crystalline state is the tendency of the molecules to point along a common axis. This is in contrast to molecules in the liquid phase, which have no intrinsic order. In the solid state, LCP molecules are highly ordered and, have little translational freedom.
Liquid-crystal polymers are available in melted/liquid or solid form. The melting temperatures ranges from about 280° C. to about 400° C. and glass transition temperatures range from about 145° C. to about 400° C., providing sufficient range to select appropriate materials for the first and second polymeric materials.
In solid form the main example of lyotropic LCPs is the commercial aramid known as Kevlar. In a similar way, several series of thermotropic LCPs have been commercially produced by several companies (e.g., Vectran/Ticona). LCP materials have a dielectric constant of about 2.9 at a frequency of about 20 GHz, a co-efficient of thermal expansion of about 8 to about 17 ppm/degree C., and a dimensional, stability of less than about 0.1%. Use of LCP material in circuit structures is disclosed in U.S. Pat. Publ. No. 2016/0014908 (Rathburn), which is hereby incorporated by reference.
Another advantage to the multilayer insulator housing 52 is that by modifying the dielectric properties of the layers 54 in a region around the contact members 58 at specific points relative to the contact geometries, changes in the capacitive field can be made to offset the inductance of the contact members 58. This “impedance tuning” can be done using a variety of techniques, including adding a continuous layer of a higher dielectric constant material, by varying the dielectric constants of the housing layers 54, or by adding localized metal at multiple points within a layer or region adjacent to the contact members 58. In the context of the present multi-layered socket housing, these changes may include increasing the thickness of the center layers 54C relative to the surface layers 54A, 54E, selecting a material for the center layer 54C with a higher dielectric constant, maintain an air gap between the center layer 54C and the contact members 58, and/or adding metal to portions of the socket housing to surround the contact members 58, each of which is discussed in U.S. patent application Ser. No. 14/565,724, entitled Performance Enhance Semiconductor Socket, filed Dec. 10, 2014, which is hereby incorporated by reference. The various structures for impedance tuning may be used alone or in combination with each other. The various structures for impedance tuning may be used alone or in combination with each other.
FIGS. 2A and 2B are sectional views of an alternate electrical connector 100 in accordance with an embodiment of the present disclosure. Insulator housing 102 is constructed with a plurality of layers 104A, 104B, 104C, 104D, 104E, 104F (“104”). A plurality of through holes 106 are formed in the insulator housing 102 to receive contact members 108. The through holes 106 and contact members 108 are arranged to correspond with terminals 110 on first circuit member 112 and contact pads 114 on second circuit device 116.
The contact members 108 are preferably sized to loosely fit in the through holes 106. The contact members 108 are preferably dual-beam structures with first end portions 114 located near first surface 116 of the insulator housing 102 and second end portions 118 located near a second surface 120 of the insulator housing 102. Main beams 122 of the contact members 108 are configured to flex outward in direction 120 within the through holes 106 when terminals 110 are compressively engaged with the first end portions 114.
In one embodiment, the layers 104A, 104B, 104C, 104D, and 104F are preferably constructed from a first polymeric material have a first glass transition temperature. The layer 104E is preferably constructed from a flowable polymeric material with a second glass transition temperature that is lower than the first glass transition temperature. After the contact members 108 are loosely positioning within the through holes 106, the electrical connector 100 is subjected to sufficient energy and/or pressure so the second glass transition temperature of the second flowable polymeric material is exceeded, but the first glass transition temperature of the first polymeric material is preferably not exceeded.
As best illustrated in FIG. 2B, the second flowable polymeric material (i.e., layer 104E) enters a molten or rubber-like state and flows into engagement with the second end portions 118 of the contact members 108 in retention region 124. In the preferred embodiment, the second flowable polymeric material seals the contact members 108 to the insulator housing 102 to reduce solder wicking.
In an alternate embodiment, pressure 126 is used to plastically deform the layer 104E to achieve the configuration illustrated in FIG. 2B. Once the layer of flowable polymeric, material 104E is in physical contact with the contact members 108 in the retention region 124, heat is applied to cure the layer 104E, thereby forming seal 128 with the contact members 108.
FIG. 3 is a sectional view of an alternate electrical connector 150 where the insulator housing 152 is molded to include first and second polymeric materials 154, 156 in accordance with an embodiment of the present disclosure. In one embodiment, the insulator housing 152 is co-injection molded by sequentially injecting the first and second polymeric materials 154, 156. The polymeric materials 154, 156 intersect at interface region 160, but preferably to not substantially mix.
A plurality of through holes 162 are formed in the insulator housing 152 to receive contact members 164. The contact members 164 include a retention feature 170 that engages primarily with the second flowable polymeric material 156 in the insulator housing 152 at retention region 174. The through holes 162 are sized to maintain gaps 166 in the region of the insulator housing 152 constructed from the first polymeric material 154 to permit flexure in flexure region 172 during engagement with circuit member 168. The gap 166 facilitates insertion of the contact members 164 before reflow and prevents engagement with the contact member 164 in the flexure region 172 during reflow of the second flowable polymeric material 156. As discussed herein, energy and/or pressure is applied to the electrical connector 150 so the second flowable polymeric material 156 flows and is fused to the contact member 164 in the retention region 174.
FIG. 4 is a sectional view of an alternate electrical connector 200 where the insulator housing 202 is molded from a first polymeric material 204 and the second flowable polymeric material 206 is selectively printed in retention region 208 in accordance with an embodiment of the present disclosure. In the illustrated embodiment, the first polymeric material 204 is molded with recesses 220 configured to receive the second flowable polymeric material 206. The second flowable polymeric material 206 is preferably printed on the insulator housing 202 before insertion of contact members 210.
Energy and/or pressure is applied to the electrical connector 200 so the second flowable polymeric material 206 flow and fuses with the contact member 210 in the retention region 208. In the illustrated embodiment, the second flowable polymeric material 206 engages with retention feature 212 on the contact members 210. In one embodiment, the second flowable polymeric material 206 substantially surrounds the perimeter of the contact member 210 in the retention region 208 to reduce wicking of solder 222 into the insulator housing 202.
FIGS. 5A and 5B are sectional views of an electrical connector 250 in accordance with an embodiment of the present disclosure. Insulator housing 252 is constricted with a plurality of layers 254A, 254B, 254C, 254D, 254E, 250F, 250G (“254”). In the illustrated embodiment, layers of a flowable polymeric material 256 are located between the layers 254D, 254E, 254F, 254G. The layers 254, 256 are preferably bonded using a variety of techniques, such as adhesive bonding, ultrasonic or solvent welding, and other techniques known to those in the art. In another embodiment, some of the layers can be molded or machined as a subassembly after the fact.
Through holes 258 extend from first surface 260 to second surface 262. In the illustrate embodiment, through holes 258 in the layers 254E, 254F, 2540 are sized to create contours 264 that generally corresponds with shape of retention features 266 of contact members 268. The complementary shapes of the contour 264 and the retention features 266 brings the flowable layers 256 in close proximity to bridge the gap there between.
The contact members 268 are preferably sized to loosely fit in the through holes 258. The contact members 268 have a shape and function generally as discussed in connection with FIGS. 1A and 1B.
As best illustrated in FIG. 5B, the flowable material 256 is plastically deformed by applying energy and/or pressure 253 to the electrical connector 250. By controlling the quantity and duration of energy and/or pressure 253 applied to the electrical connector 250 it is possible to form seal 270 around the contact member 268 in engagement region 272, without compromising the structural integrity of the insulator housing 252. The seal 270 serves to both retain the contact member 268 in the insulator housing 252 and inhibits solder 274 from wicking into the through holes 258.
FIGS. 6A and 6B are sectional views of alternate electrical connector 300 with insulator housing 302 retaining, spring contact members 304. The insulator housing 302 is constructed from multiple layers 306A, 306B, 306C, 306D, 306E, 306F (“306”) in accordance with an, embodiment of the present disclosure. In one embodiment, layers of a flowable polymeric material 308 are located between the layers 306C, 306D, 306E, 306F. Additional details about insulator housings with spring contact members applicable to this disclosure are disclosed in U.S. Pat. No. 8,758,067 (Rathburn) and U.S. Pat. Publ. 2015/0091600 (Rathburn), filed Dec. 10, 2014, the disclosures of which are hereby incorporated by reference in their entireties.
The spring contact members 304 are of a conventional structure with an upper portion 310 that slides axially relative to lower portion 312. Spring member 314 located in through holes 330 biases the upper portion 310 away from the lower portion 312 along axis 316. In application, upper portion 310 extends above top surface 320 of the insulator housing 302 to engage with contact members on the IC device 322. Simultaneously, lower portion 312 extends beyond lower surface 324 of the insulator housing 302 to engage with contact pads 326 on the PCB 328. The lower portion 312 is typically soldered to the contact pads 326.
The through holes 330 in the layers 306D, 306E, 306F are sized to follow contour of the lower portion 312. Applying energy and/or pressure to the electrical contact 300 causes plastic deformation of the layers of a flowable polymeric material 308, which forms a seal 332 around the lower portion 312 at retention region 334 to prevent solder wicking.
FIGS. 7A through 7C illustrate a surface mount technology BGA socket 350 with a layer of a flowable polymeric material 352 in accordance with an embodiment of the present disclosure. Contact members 354 are inserted in preformed openings 356 in substrate 358. After insertion, the layer of flowable polymeric material 352 is positioned over proximal ends 360 of the contact members 354. Energy and/or pressure is applied to flow the layer of flowable polymeric material 352 into engagement with the contact members 354. The contact members 354 are now mechanically retained to the substrate 358. The flowable polymeric material 352 also forms a seal around the contact members 354 in the openings 356, so that when solder balls 364 are attached and subsequent reflowed to circuit board 376 the solder 364 is prevented from wicking up the contact members 354 and into the insulator housing 370. In an alternate embodiment, the flowable polymeric material 352 is molded or deposited on the substrate 358 adjacent the openings 356.
The substrate 358 containing the contact members 354 can be inverted to expose proximal ends 360 of the contact members 354, which will typically connect to the printed circuit board during final assembly. The rear surface of the substrate 358 and the exposed proximal ends 360 of the contact members 354 can be treated as a field of connection points for further enhancement that provides contact retention, adds circuit features not normally embedded within a socket, adds mechanical features to improve the reliability of the solder joint to the PCB, and provides a platform to add passive and active circuit features to improve electrical performance or internal function and intelligence, such as disclosed in commonly assigned U.S. Pat. No. 8,955,215 (Rathburn), which is hereby incorporated by reference.
In the illustrated embodiment, the flowable polymeric material 352 preferably includes an array of openings 362 that correspond with the proximal ends 360 of the contact members 354 so that solder balls 364 can be applied. In an alternate embodiment, the flowable polymeric material 352 is applied as a continuous sheet without the openings 362 and the openings 362 are subsequently drilled, such as with a laser. Distal ends 366 of the contact members 354 are then positioned in openings 368 in insulator housing 370.
For some applications Cu may be too soft to be used as the contact members 354, so CuNiSi or other copper alloy may be substituted. In the illustrate embodiment, the contact members 354 do not include contact retention features, greatly reducing the complexity of the component and the tooling required to produce them. After insertion, the flowable polymeric material 352 retains the contact members 354 in the socket 350.
As best illustrated in FIG. 7C, the socket 350 enables direct socketing of BGA device 372 without reflow to the solder balls 374. The socket 350 permits the BGA device 372 to be removable and replaceable without the need for rework or reflow of the solder balls 374. The socket 350 itself is soldered to PCB 376. The distal portions 366 of the contact members 354 are shaped to accept the solder balls 374 on the BGA device 372 in a manner that retains the BGA device 372, but allows the BGA device 372 to be lifted out.
The challenge with this type of product is to create an interface between the solder ball 374 on the BGA device 372 and the contact tips 366 such that the BGA device 372 can be inserted with low enough force to enable insertion by hand, while still providing stable contact resistance and reliable connection. Related to this challenge is the extraction force relative to insertion force such that the BGA device 372 can be easily removed by hand or with the aid of a tool without breaking solder joints 380 between the contact members 354 and the PCB 376 as well as the joint, from the BGA device 372 to the solder balls 374.
As best illustrated in FIG. 7B, distal portions 366 of the contact members 354 include contact tips 382 that score the solder balls 374 during insertion to remove oxides. Adjacent a curved region 384 has a diameter corresponding to a diameter of the solder balls 374 to capture the solder balls 374 in the insulator housing 370. Once the BGA device 372 is fully seated there will be a slight engagement of the contact tips 382 beyond the upper hemisphere 386 of the solder ball 374 diameter to retain the solder ball 374 in the insulator housing 370. Several varieties of contact shapes and geometries can be formed to optimize the interface and reliability, with multiple points of contact greatly enhancing probability of reliable connection as well as reducing inductance and contact resistance. (See FIGS. 7E-7G).
The intent of the design is to “loosely” or slightly cradle the solder balls 374 on the BGA device 372 in the openings 368 in the insulator housing 370. The openings 368 in the insulator housing 370 are sized to permit the beams 388 to flex slightly while the openings 368 in the insulator housing 370 prevent over deflection of the beams 388. The beams 388 can also be shorter to minimize the height of the socket 350. The contact members 354 can also be coined or formed with a single beam 388 that closely surrounds the solder balls 374 to provide multiple points of contact as well as reduce metal content to improve capacitive effects.
FIG. 7D illustrates an array 390 of contact members 354 stamped and formed on grid that matches the pattern of the openings 356 in the substrate 358. The contact members 354 are simultaneously engaged with the substrate 358. The portions 392 of the array 390 that hold the contact members 354 together are then removed by etching, laser cutting, or the like.
FIGS. 7E-7G illustrate alternate configurations of the contact members 354 in accordance with an embodiment of the present disclosure. FIGS. 7E and 7F illustrate embodiments with three beams 388. All of the beams 388 can flex radially outward. FIG. 7G is illustrates a folded structure with paired beams 394A, 394B, where the respective pairs 394 flex, away from each other along axis 396.
FIG. 7H is a side view of an electrical interconnect 500 with electroplated terminals 502 coupled to a BGA device 504 engaged with the socket 350 of FIG. 7A in accordance with an embodiment of the present disclosure. Details of the electrical interconnect 500 are disclosed in commonly owned U.S. patent Ser. No. 14/408,039, filed Mar. 13, 2013, entitled HIGH SPEED CIRCUIT ASSEMBLY WITH INTEGRAL TERMINAL AND MATING BIAS LOADING ELECTRICAL CONNECTOR ASSEMBLY, the disclosure of which is hereby incorporated by reference.
FIG. 8 is a side cross-sectional view of a portion of a semiconductor socket 400 in accordance with an embodiment of the present disclosure. Substrate 402 includes an array of through holes 404 that extend from a first surface 406 to a second surface 408. Recesses 410 are formed in the second surface 408 that overlaps with the through holes 404. The substrate 402 can be configured to engage with a variety of circuit members 412, such as example, IC device 412. As used herein, the term “circuit member” refers to, for example, a packaged integrated circuit device, an unpackaged integrated circuit device, a printed circuit board, a flexible circuit, a bare-die device, an organic or inorganic, substrate, a rigid circuit, or any other device capable of carrying electrical current.
A plurality of discrete contact members 414 are inserted into recesses 410 so distal portions 416 extend out through the holes 404. In the illustrated embodiment, the distal portions 416 are simple cantilever beams located above the first surface 406. The distal portions 416 preferably have a generally uniform cross section. Proximal portions 418 of the contact members 414 are preferably configured to reside in the recesses 410. The contact members 416 can be positioned into the recesses 410 using a variety of techniques, such as for example stitching or vibratory techniques. The contact members 414 are preferably constructed of copper or similar metallic materials such as phosphor bronze or beryllium-copper. The contact members are preferably plated with a corrosion resistant metallic material, such as nickel, gold, silver, palladium, or multiple layers thereof. Semiconductor sockets such as illustrated in FIGS. 8 and 9 are disclosed in commonly-assigned U.S. patent application Ser. No. 13/319,158 entitled Semiconductor Socket, filed Jun. 15, 2010, and Ser. No. 14/408,338 entitled Semiconductor Socket with Direct Metalization, filed Mar. 14, 2013, the entire disclosures of which are hereby incorporated by reference.
In one embodiment, the entire substrate 402 is substantially constructed from a low glass transition temperature polymeric material. During reflow the polymeric material of the substrate 402 engages with the proximal portions 418. After cooling, the substrate 402 is bonded and sealed to the proximal portions 418 in the retention region 420, preventing solder 422 from wicking into the recesses 410.
In an alternate embodiment, the substrate 402 is constructed from a high glass transition temperature polymeric material and the inside surface of the recesses 410 are printed with lower glass transition polymeric material 422. During reflow the polymeric material 422 engages with the proximal portions 418.
FIG. 9 is a cross-sectional view of an interconnect assembly 450 in, accordance with an embodiment of the present disclosure. Substrate 452 includes an array of through holes 454 that extend from a first surface 456 to a second surface 458. Recesses 458 are formed in the second surface 456 that overlaps with the through holes 454.
Substrate 452 is constructed from a high glass transition temperature polymeric material. Recess 458 in the substrate 452 is filed with low glass temperature polymeric material 460. The polymeric material 460 can be molded with the substrate 452 or be deposited in the recess 458 after the substrate 452 is formed. The through holes 454 also extend through the polymeric material 460.
A plurality of discrete contact members 462 are inserted into the through holes 454. In the illustrated embodiment, the contact members 462 are simple cantilever beams without any retention features. During reflow the polymeric material 460 engages with proximal portions 464 of the contact members 462. After cooling, the substrate 452 is bonded and sealed to the proximal portions 464 in retention region 466. Solder balls 468 are printed onto the proximal end 470 of the contact member 462. The polymeric material 460 forms a seal in the retention region 466 to prevent solder 468 from wicking into the through holes 454.
Where a range of values is provided, it is understood that each intervening value, to the tenth of the unit of the lower limit unless the context clearly dictates otherwise, between the upper and lower limit of that range and any other stated or intervening value in that stated range is encompassed within the embodiments of the disclosure. The upper and lower limits of these smaller ranges which may independently be included in the smaller ranges is also encompassed within the embodiments of the disclosure, subject to any specifically excluded limit in the stated range. Where the stated range includes one or both of the limits, ranges excluding either both of those included limits are also included in the embodiments of the present disclosure.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the embodiments of the present disclosure belong. Although any methods and materials similar or equivalent to those described herein can also be used in the practice or testing of the embodiments of the present disclosure, the preferred methods and materials are now described. All patents and publications mentioned herein, including those cited in the Background of the application, are hereby incorporated by reference to disclose and described the methods and/or materials in connection with which the publications are cited.
The publications discussed herein are provided solely for their disclosure prior to the filing date of the present application. Nothing herein is to be construed as an admission that the present disclosure is not entitled to antedate such publication by virtue of prior invention. Further, the dates of publication provided may be different from the actual publication dates which may need, to be independently confirmed.
Other embodiments of the disclosure are possible. Although the description above contains much specificity, these should not be construed as limiting the scope of the disclosure, but as merely providing illustrations of some of the presently preferred embodiments of this disclosure. It is also contemplated that various combinations or sub-combinations of the specific features and aspects of the embodiments may be made and still fall within the scope of the present disclosure. It should be understood that various features and aspects of the disclosed embodiments can be combined with or substituted for one another in order to form varying modes of the disclosed embodiments of the disclosure. Thus, it is intended that the scope of the present disclosure herein disclosed should not be limited by the particular disclosed embodiments described above.
Thus the scope of this disclosure should be determined by the appended claims and their legal equivalents. Therefore, it will be appreciated that the scope of the present disclosure fully encompasses other embodiments which may become obvious to those skilled in the art, and that the scope of the present disclosure is accordingly to be limited by nothing other than the appended claims, in which reference to an element in the singular is not intended to mean “one and only one” unless explicitly so stated, but rather “one or more.” All structural, chemical, and functional equivalents to the elements of the above-described preferred embodiments) that are known to those of ordinary skill in the art are expressly incorporated herein by reference and are intended to be encompassed by the present claims. Moreover, it is not necessary for a device or method to address each and every problem sought to be solved by the present disclosure, for it to be encompassed by the present claims. Furthermore, no element, component, or method step in the present disclosure is intended to be dedicated to the public regardless of whether the element, component, or method step is explicitly recited in the claims.

## Claims

1. A method of making an electrical interconnector, the method comprising the steps of:
positioning a plurality of discrete contact members in through holes in a substrate so distal portions of the contact members extend above a first surface of the substrate in a cantilevered configuration and proximal portions of the contact members are accessible along a second surface of the substrate;
locating a flowable polymeric on the second surface of the substrate adjacent the through holes;
subjecting the substrate and the contact members to sufficient energy and/or pressure so the flowable polymeric layer flows into engagement with the proximal portions of the contact members and fuses the contact members to the substrate;
positioning distal portions of the contact members in through holes in an insulator housing; and
bonding the first surface of the substrate to a first surface of the insulator housing so the distal portions are accessible from a second surface of the insulator housing.

2. The method of claim 1 wherein the flowable polymeric material fused to the contact members substantially seals the through holes in the substrate.

3. The method of claim 1 comprising forming distal portions of the contact members with a plurality of beams maintained in a cantilevered relationship with respect to the first surface of the substrate.

4. The method of claim 1 comprising forming distal portions of the contact members with a plurality of beams that elastically deform to mechanically and electrically engage with terminals on circuit members.

5. The method of claim 1 comprising positioning a layer of the flowable polymeric material on the second surface of the substrate.

6. The method of claim 5 comprising processing the flowable polymeric material to reveal the proximal portions of the contact members.

7. The method of claim 1 comprising molding the flowable polymeric material to the second surface of the substrate adjacent the through holes.

8. The method of claim 1 comprising depositing the flowable polymeric material on the second surface of the substrate adjacent the through holes.

9. The method of claim 1 selecting the flowable polymeric material from low melt liquid crystal polymer, an epoxy set resin, a thermoset material, or a thermoplastic material.

10. The method of claim 1 comprising:
forming the substrate from a first polymeric material have a first glass transition temperature and the flowable polymeric material from a second polymeric material have a second glass transition temperature, wherein the second glass transition temperature is lower than the first glass transition temperature; and
subjecting the substrate and the contact members to sufficient energy and/or pressure so the second glass transition temperature of the flowable polymeric material is exceeded, but the first glass transition temperature is not exceeded, so that the flowable polymeric material enters a molten or rubber-like state and flows into engagement with proximal portions of the contact members.

11. The method of claim 1 comprising:
electrically coupling proximal portions of the contact members to contact pads on a first circuit member;
positioning terminals on a second circuit member in the through holes along the second surface of the insulator housing; and
mechanically and electrically coupling the terminals on the second circuit member with distal portions of the contact members.

12. The method of claim 1 comprising:
positioning solder ball terminals on a BOA device in the through holes along the second surface of the insulator housing; and
elastically deforming distal portions of the contact members to mechanically and electrically engage with the solder ball terminals on the BOA device.

13. An electrical interconnector comprising:
a plurality of discrete contact members located in through holes in a substrate so distal portions of the contact members extend above a first surface of the substrate in a cantilevered configuration and proximal portions of the contact members are accessible along a second surface of the substrate;
a flowable polymeric material located on the second surface of the substrate is fusion bonded to the proximal portions of the contact members so the flowable polymeric material substantially seals the through holes in the substrate; and
an insulator housing bonded to the first surface of the substrate with the distal portions of the contact members located in through holes in an insulator housing, so the distal portions are accessible from a second surface of the insulator housing.

14. The electrical interconnect of claim 13 wherein distal portions of the contact members comprise a plurality of beams maintained in a cantilevered relationship with respect to the first surface of the substrate.

15. The electrical interconnect of claim 13 wherein distal portions of the contact members comprise a plurality of beams that elastically deform to mechanically and electrically engage with terminals on a circuit member.

16. The electrical interconnect of claim 13 wherein the flowable polymeric material is selected from one of a low melt liquid crystal polymer, an epoxy set resin, a thermoset material, or a thermoplastic material.

17. The electrical interconnect of claim 13 wherein the substrate is formed from a first polymeric material have a first glass transition temperature and the flowable polymeric material from a second polymeric material have a second glass transition temperature, wherein the second glass transition temperature is lower than the first glass transition temperature.

18. An electrical assembly comprising:
the electrical interconnect of claim 13;
contact pads on a first circuit member electrically coupled proximal portions of the contact members;
terminals on, a second circuit member positioned in the through holes along the second surface of the insulator housing, and mechanically and electrically coupled with distal portions of the contact members.

19. An electrical assembly comprising:
the electrical interconnect of claim 13;
solder ball terminals on a BGA device positioned in the through holes along they second surface of the insulator housing, the distal portions of the contact members mechanically and electrically coupled with the solder ball terminals on the BGA device.