Test socket with conductive compression contacts for integrated circuits

Abstract

To provide a socket contact structure that suppresses signal loss due to an increase in an electrical signal path in a BGA socket and that solves problems of impedance matching, contact damage, and the like, especially in a cantilevered beam socket structure.SOLUTION: There is provided a test socket for an electronic circuit device 13 with protruding circuit contacts 11. The test socket includes an underlying PCB substrate 5 with an overlaying electrically insulative housing 7. The PCB substrate 5 includes an array of electrically conductive vias 15 extending therethrough. The housing 7 includes an array of socket apertures 9 which align with the PCB vias 15, and contain resiliently compressible electrically conductive compression contacts 17 therein that connect electrically with the conductive vias 15 of the PCB substrate 5. The socket apertures 9 each have peripheral retention flaps 27 which electrically engage and retain the protruding circuit contacts 11 of the electronic circuit device 13 with the conductive compression contacts 17 within the socket apertures 9 during testing.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] (CROSS REFERENCE TO RELATED APPLICATIONS) This application is a non-provisional patent application that claims the benefit of U.S. Provisional Application No. 63 / 375,993, filed September 16, 2022, entitled “Test Socket With Conductive Compression Contacts For High Performance Integrated Circuits,” the contents of which are incorporated by reference in their entirety into this specification.

[0002] The present invention relates generally to the art of test sockets for electronic circuit devices such as integrated circuits, and more particularly to an improved test socket structure for high performance integrated circuits incorporating conductive compression contacts for greater electrical conductivity and design flexibility. [Background technology]

[0003] The statements in this section are merely intended to provide background information related to the present disclosure and are not intended to be prior art.

[0004] Ball Grid Array (BGA) technology refers to a particular type of surface mount package used to permanently or semi-permanently attach integrated circuits to a printed circuit board (PCB). In a BGA implementation, the conductive interconnect pins of a traditional pin grid array or dual in-line package are replaced with an array of conductive circuit contacts or pads in the form of small solder balls on the underside of the integrated circuit. This allows for more connection points and shorter trace connections to the package leads, improving performance at high speeds.

[0005] As technology advances, more and more products are being designed to use high performance integrated circuits. To analyze and finalize the design of these products / circuits during development, test sockets are used to facilitate the interconnection between the device under test (DUT) and the PCB. Without test sockets, designing and testing such circuits would require multiple solder reflows to connect and disconnect. To cater to such stringent needs, sockets allow for a semi-permanent connection between the DUT and the main target PCB. However, making such interconnections through test sockets inevitably increases the electrical signal path, essentially resulting in potential signal loss. Since high performance applications require such signal loss to be minimized, it is considered beneficial to use BGA technology for such sockets.

[0006] In conventional sockets, current contact technology for BGA circuits typically employs pressed metal cantilever beams, known as "grippers," that extend through the socket body and connect each BGA solder ball of the DUT to the main target PCB. Such a "gripper" contact and how it engages a solder ball are shown in Figures 1A, 1B, and 1C of the drawings. As shown, when the DUT is inserted into the test socket, each pressed metal cantilever beam grips an associated solder ball of the DUT. The opposite end of each beam is then soldered to the main PCB. Of note, this technology requires the pressed metal beams to be a certain length to apply a minimum retention force to the solder balls of the DUT, which essentially thickens the socket body and introduces undesirable signal loss into the system. Of note, this conventional contact technology is typically limited in performance to approximately 24 GHz.

[0007] The use of cantilever technology also creates additional problems, especially when used with high performance integrated circuits. For example, cantilever contacts tend to suffer from undesirable signal reflections and insertion loss due to the elongated and irregular shape of the cantilever. The irregular shape of the cantilever also creates variations in the dielectric area from the signal inlet to the signal outlet, making impedance matching more difficult. Additionally, cantilever contacts can move or tilt within the socket opening, resulting in improper contact positioning when soldered to the main PCB and potential damage to the contact when inserting a new device.

[0008] Traditional BGA sockets with cantilever contacts are also difficult to reconfigure to accommodate integrated circuits with different sized solder balls: the irregular shaped cantilevers must be stamped out of metal and cannot be reconfigured without the use of expensive hard tooling, making this style of contact less versatile to use.

[0009] Also, the solder balls of BGA circuits are not always nicely rounded at well-defined equators that the cantilever contacts are intended to grip, and currently there is no effective means of adapting conventional cantilever contacts to incorporate any type of retention feature for situations where the solder ball equators are not well-defined.

[0010] Finally, many devices under test require capacitors and resistors for proper operation. These electrical components must be located close to the device to maintain the integrity of the power supply. Capacitors also need to be located close to the required load to provide high speed current. However, this cannot be provided using existing cantilever style socket systems because such components must be incorporated into the main PCB, which is separated from the DUT by the socket assembly. This limits the effectiveness of current contact technology in these situations.

[0011] The above problems and other shortcomings associated with conventional cantilever-type socket contacts have reduced their versatility and effectiveness in use, particularly with advances in high performance integrated circuits. It is apparent, therefore, that a clear industry need exists for an improved socket contact solution which overcomes many of the limitations of conventional test sockets and provides enhanced performance characteristics for use with high performance integrated circuits. Summary of the Invention [Problem to be solved by the invention]

[0012] With the above in mind, one object of the present invention is to provide a compression contact socket solution that completely avoids the cantilever contact approach of BGA test sockets and establishes a much shorter trace connection between the DUT and the main PCB, thus reducing the inherent signal loss associated with traditional socket connections and significantly improving circuit performance speed.

[0013] Another object is to provide such an improved compression contact socket with a more uniform cross-sectional contact shape which improves impedance matching capabilities and reduces undesirable signal reflections and insertion losses caused by the elongated, irregular shape of conventional cantilever beam contact technology.

[0014] It is yet another object of the present invention to provide a socket contact which is less susceptible to cant and other misalignments and which facilitates daisy-chain testing of electrical components without damaging the electrical contacts of the test socket. In this regard, it is also an object to provide such a compression-type contact which can be more easily reconfigured to accommodate integrated circuits having circuit contacts of different sizes and configurations.

[0015] Another object of the present invention is to design such a test socket as the PCB itself, with the necessary capacitors and resistors embedded therein and located in close proximity to the DUT, improving power integrity and providing higher operating current speeds for high performance circuits. In this manner, the contacts may optionally be configured in the form of a coaxial transmission structure, as described further herein, which is not available with the current cantilever contact approach.

[0016] It is a further object to design such sockets so that they can include or incorporate retention features for securing integrated circuits having less well-defined or irregularly shaped circuit contact elements. It is a further object to provide all of the foregoing advantages and improvements without increasing the required footprint of the DUT, ensuring a smooth transition from test to final production. [Means for solving the problem]

[0017] To achieve the above objectives, the present invention incorporates a novel approach to test socket technology for integrated circuits that utilizes conductive compression contacts instead of the conventional cantilever-type approach. In the present invention, the test socket has a body including an underlying PCB substrate and an overlying insulating socket housing secured thereon. The underlying PCB substrate includes an array of filled vias extending through the PCB substrate arranged to align with an array of electrical circuit contacts projecting from a DUT, such as solder balls in an integrated circuit incorporating BGA technology. A conductive compression contact is attached to the upper surface of each filled via, preferably comprised of a resiliently compressible material in the form of a small conductive elastomeric button (e.g., .about.75 μm thick). The lower end of each filled via terminates in a small solder ball attachment that is used to establish a solder connection to the main PCB of the circuit.

[0018] An insulating socket housing overlies and is affixed to the PCB substrate. The socket housing includes an array of generally cylindrically shaped socket holes or openings extending through the body configured to align with the array of filled vias and compression contacts in the PCB substrate. One or more flexible retention members formed on an upper periphery of each socket opening in the housing function to firmly grip and hold the contacts of the DUT against the conductive compression contacts of the test socket when inserted therein. Thus, with this configuration, electrical connections are effectively established from the array of DUT contacts through the conductive compression contacts and corresponding filled vias in the PCB substrate to the main PCB.

[0019] In this configuration, no elongated, bending cantilever arms are required to make the electrical connection. The socket housing grips and holds the protruding circuit contacts of the DUT to tightly engage the corresponding compression contacts of the PCB board. Thus, the compression contacts are kept to a minimum thickness and the filled vias are significantly shortened, effectively shortening the overall signal path between the DUT and the main PCB. Furthermore, the compression contacts and corresponding filled vias can be constructed with a relatively uniform cylindrical cross-section and can be easily tailored to optimize impedance matching as needed. All of the aforementioned features have been found to help significantly reduce signal loss and signal reflections associated with conventional cantilever contacts, significantly increasing circuit performance speed.

[0020] In addition to the above, because the socket body is constructed in PCB form, power and ground layers can be arranged in multiple layers. This allows resistors and capacitors to be embedded in the PCB substrate closer to the DUT, improving power integrity and current speeds required for high performance circuits. The cylindrical shape of these contacts and vias also makes it easy to configure filled vias as coaxial structures, if desired. Again, this is not possible with traditional cantilever contact technology.

[0021] In this structure, a conductive compression contact is firmly secured to each filled via in the PCB substrate at the base of each corresponding socket opening, so it cannot tilt or move within the socket during insertion of the DUT and is less susceptible to damage than traditional cantilever-type contacts.

[0022] The above and additional features and advantages of the present invention will become more readily apparent from the following detailed description, however, it should be understood that the description and specific examples herein are for illustrative purposes only and are not intended to limit the scope of the present disclosure. [Brief description of the drawings]

[0023] The drawings described herein are for illustrative purposes only and are not intended to limit the scope of the present disclosure in any way.

[0024] [Figure 1A] FIG. 1A is a perspective view of a prior art cantilever type electrical contact currently used in BGA test sockets for integrated circuits.

[0025] [Figure 1B] FIG. 1B is a pair of cross-sectional views illustrating a test socket incorporating the cantilever contacts shown in FIG. 1A and illustrating how the solder ball contacts of a BGA device are engaged thereby.

[0026] [Figure 2A] FIG. 2A is a cross-sectional view of a BGA test socket constructed in accordance with the present invention and positioned for insertion of a BGA test device therein.

[0027] [Figure 2B] FIG. 2B is a cross-sectional view of the BGA test socket of FIG. 2A with a BGA test device inserted therein in mating relationship.

[0028] [Diagram 3]FIG. 3 is a close-up cross-sectional view of one conductive compression contact of the test socket of FIG. 2B, accompanied by an enlarged view showing a solder ball of a BGA test device inserted within the socket opening.

[0029] [Figure 4] FIG. 4 is a close-up cross-sectional view of a BGA test socket similar to that shown in FIG. 2B, illustrating one embodiment in which conductive compression contacts are pressed against the top of filled vias in a PCB substrate.

[0030] [Diagram 5] FIG. 5 is another close-up cross-sectional view of a BGA test socket incorporating the principles of the present invention, showing an alternative embodiment in which the conductive compression contacts are carried on separate carriers formed in each socket opening of the housing.

[0031] [Figure 6] FIG. 6 is an exploded transparent close-up perspective view of a socket housing similar to that shown in FIGS. 2A-4, showing flexible retaining members formed around the upper periphery of each socket opening and conductive elastomeric contacts disposed at their base.

[0032] [Figure 7] FIG. 7 is a close-up perspective view of a portion of a socket housing illustrating one embodiment of a plurality of flexible retention members formed around the periphery of each socket opening for receiving in a snap-lock relationship the solder ball contacts of a BGA test device.

[0033] [Figure 8A] FIG. 8A is a top view illustrating an alternative embodiment of a flexible retention member formed on each socket housing configured to help accommodate solder balls of various sizes.

[0034] [Figure 8B]FIG. 8B is a top view of yet another alternative embodiment of the flexible retaining member shown in FIG. 8A configured to help accommodate solder balls of various sizes.

[0035] [Figure 8C] FIG. 8C is a top view of the retention flap shown in FIG. 8A, illustrating how the flap is appropriately sized to accommodate and provide the desired retention force to a variety of different sized solder balls.

[0036] [Figure 8D] FIG. 8D is a close-up side elevational view (partial view only) showing how solder balls are retained within sockets in a socket housing by the different sized retention flaps shown in either FIG. 8A or FIG. 8B.

[0037] [Figure 9A] FIG. 9A is a transparent close-up perspective view of a socket housing similar to that shown in FIG. 6, illustrating an alternative embodiment of a conductive compression contact having a central slit to accommodate receipt of a solder ball and reduce resistive push-back force.

[0038] [Figure 9B] FIG. 9B is a transparent close-up perspective view similar to that shown in FIG. 9A illustrating another alternative configuration of a conductive compression contact having a pair of intersecting central slits.

[0039] [Figure 9C] FIG. 9C is a close-up side elevational view of a test socket incorporating a socket housing with the alternative conductive compression contact of FIG. 9A or FIG. 9B with the socket housing cut away to facilitate viewing of the compression contact seated therein. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0040] The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses. It should be understood that throughout the drawings, corresponding reference numerals indicate like or corresponding parts and features. Moreover, although the following discussion shall be particularly relevant and focused on test sockets for integrated circuits utilizing BGA contact mounting technology, it will be recognized and understood that the present invention is equally suitable and applicable to test sockets designed to accommodate other pin grid array type circuits having protruding conductive interconnect contact pins.

[0041] As discussed above and illustrated in Figures 1A-1C, current contact technology used in BGA test sockets typically employs a stamped metal cantilever beam, known as a "gripper," that extends through the socket body and connects each BGA solder ball of the DUT to the main PCB. As previously discussed, the elongated, irregular shape and flexible cantilever action present many performance and other issues with the use of this type of contact. The present invention incorporates a new approach to test socket technology that incorporates conductive compression contacts and PCB substrates to solve many of the problems associated with traditional cantilever type contacts.

[0042] 2A and 2B, it can be seen that the BGA test socket 1 of the present invention has a body portion 3 including an underlying substrate 5 configured as a PCB, on which is mounted a BGA insulating socket housing 7. The socket housing 7 includes an array of generally cylindrical socket holes or openings 9 extending therethrough and configured to align with and receive an array of solder ball contacts 11 of a particular device under test (DUT) 13. FIG. 2A shows the DUT 13 just prior to connection to the test socket 1, aligned with the socket openings 9 in the housing 7, while FIG. 2B shows the DUT 13 connected to the test socket 1 with the solder ball contacts 11 of the DUT 13 inserted into the corresponding openings 9 in the housing 7.

[0043] The underlying PCB substrate 5 of the socket body 3 includes an array of conductive filled vias 15 extending therethrough, which are positioned to align with the socket openings 9 in the housing 7 and, in turn, with the array of solder balls 11 of the DUT 13. As can be best seen in FIG. 3, a conductive compression contact 17 is attached to the top surface 19 of each filled via 15 in the PCB substrate 5. As can be seen throughout the drawings, the bottom end of each filled via 15 terminates in a small solder ball attachment portion 21 that is used to establish a solder connection to the circuit's main PCB (not shown). Thus, an electrical connection is effectively established from the array of DUT solder ball contacts 11 through the conductive compression contacts 17 and corresponding filled vias 15 in the PCB substrate 5 to the main PCB.

[0044] In this embodiment, it is contemplated that the compression contacts 17 are preferably constructed of a resiliently compressible elastic material such as a conductive elastomer, for example, silicone rubber embedded with silver particles, silicone rubber embedded with silver plated nickel particles, or silicone rubber embedded with gold plated nickel particles, etc. It is contemplated, without limitation, that other conductive elastomers are contemplated, and further that such compression contacts 17 may take the form of any conductive spring or hybrid spring / elastomer combination, or other conductive compression mechanism, without departing from the invention herein.

[0045] As shown in Figures 3 and 4, in a preferred embodiment, it is contemplated that each contact 17 may take the form of a small, generally cylindrical, conductive elastomer button approximately 75 μm thick. In this embodiment, the contact 17 may be screen printed onto the top end 19 of a corresponding via 15 in the PCB substrate 5. The size of the elastomer button 17 may also be easily configured to accommodate various solder ball sizes for different DUTs. Because the contact 17 has a more simplified, uniform cylindrical shape, such reconfiguration can be achieved relatively easily using only soft tooling, whereas conventional pressed cantilever shaped contacts can only be reconfigured using expensive hard tooling.

[0046] It is further contemplated that in an alternative embodiment, the compression contacts 17 may be carried on separate carriers 23 formed in each socket opening 9 of the housing 7 and laminated to the PCB substrate 5, as shown in Figure 5. Other manners of connecting such conductive elastomeric contacts 17 would be possible without departing from the invention herein. However, it should be understood that the size of such contacts 17, regardless of how secured, may vary depending on the particular performance requirements and needs of a particular application.

[0047] 3, the top surface 25 of the elastomeric contact 17 may have a concave or other contoured surface formed to conform and mate with the generally spherical shape of the corresponding solder ball 11 of the DUT 13. Forming such a seat for the solder ball contact 11 on the contact 17 may help provide improved surface area contact and better electrical connectivity over a standard ball-shaped solder contact. However, if the solder balls 11 have height variations, the top surface may be flat to allow for more compliance range.

[0048] 2A-6, an insulating socket housing 7 of the test socket 1 overlies and is attached to the PCB substrate 5. The housing 7 is preferably constructed of an electrically insulating material that can withstand a reflow temperature of at least about 230 degrees Celsius, such as PEEK, polyimide, polyamide, FR4 / 5, G10, or other insulating material. The housing 7 may be attached to the PCB substrate 5 by any suitable means known in the art.

[0049] As best shown in Figures 6 and 7, one or more flexible, resilient retention members or flaps 27 are formed within the housing 7 at an upper periphery 29 of each socket opening 9. The retention flap(s) 27 project inwardly from the periphery 29 to narrow a portion of the upper access to the socket opening 9 to a diameter slightly smaller than the maximum diameter of the solder balls 11 at their equator. Thus, when the DUT 13 is inserted into the test socket 1, the retention flap(s) 27 corresponding to each socket opening 9 flexes downward toward the compression contacts 17 and outwardly past the equator of the ball contacts 11 so that the solder balls 11 can enter the socket opening 9. As best shown in Figure 3, once inserted, the retention flap(s) 27 flex back inwardly in a resilient manner to close the solder ball contacts 11 in a position slightly over-dead-center relative to the equator of the solder balls. In this manner, the flexible retention flap(s) 27 act to firmly grip and hold the solder ball contacts 11 of the DUT 13 against the top surfaces 25 of the conductive compression contacts 17 of the test socket 1 .

[0050] In the previous embodiment, the retention flaps 27 are of substantially equal size and shape, and the size and number of flaps included may vary depending on the application at hand. However, with reference to Figures 8A-8C, it is contemplated that other retention flap configurations may be useful to better accommodate various situations. For example, due to size tolerance variations, it is known that the diameter of a typical solder ball contact tends to vary across the DUT array itself, and often between different DUTs. Thus, the size of the solder balls may be expressed with a diameter tolerance, e.g., nominal φ0.3±0.025 mm.

[0051] To accommodate various sizes of solder ball contacts 11 and ensure proper connection and retention, the flap 27 may alternatively be formed as a series of different sized fingers or smaller sub-flaps 27a, 27b, 27c, and 27d that project radially inward from the upper periphery 29 of the socket opening 9 and establish different diameters based on the tolerances of a typical solder ball. Such flaps may be a series of individual flaps or a series of sub-flaps of different sizes as shown in Figures 8A and 8B. Of course, more or fewer flaps / sub-flaps may be used depending on the needs of the application.

[0052] 8A and 8B show two alternative adaptations of the retention flap 27 having different sub-flap configurations 27a, 27b, 27c, and 27d. In FIG. 8A, the sub-flaps are slightly arcuate and more pointed at their free ends, with the larger / longer sub-flap 27a curving oppositely to that of the remaining sub-flaps 27b, 27c, 27d. In the embodiment of FIG. 8B, the sub-flaps are less curving and slightly angular at their free ends, and possibly slightly stiffer than the sub-flaps of the embodiment shown in FIG. 8A. In each embodiment, sub-flap 27a extends inwardly most, thus establishing the small diameter of the socket opening 9. Each of the sub-flaps 27b, 27c, 27d protrudes slightly less radially inward, thereby establishing a slightly larger diameter opening at its point to help accommodate larger diameter solder ball contacts 11 (typically based on a given solder ball tolerance). Of course, each of the sub-flaps 27a, 27b, 27c, and 27d may be configured as an individual protruding flap without departing from the invention herein.

[0053] As best seen in Figures 8C and 8D, the longer sub-flaps 27a are designed to project inwardly enough to ensure a proper interference fit for even the smallest diameter solder ball contacts 11 when inserted into the socket opening 9. By way of example, Figure 8C shows one possible configuration for accommodating solder ball contacts 11 having a nominal diameter of 0.3 ± 0.025 mm. A larger solder ball contact 11 (e.g., φ 0.325 mm) is engaged and held in place by one or more of the sub-flaps 27a-27d. For smaller solder ball contacts 11 at the lower end of the tolerance range (e.g., φ 0.275 mm), it can be seen that the sub-flaps 27a sufficiently narrow the diameter of the entry into the socket opening 9 so that the smaller contacts 11 are engaged by the retention flaps 27 and are properly held with sufficient engagement force against the compression contacts 17.

[0054] As shown in FIG. 8D, when a solder ball 11 is inserted into the socket opening 9, the longer sub-flap(s) 27a (and possibly other sub-flaps 27b-27d depending on the diameter of the solder ball contact 11 being inserted) are bent downward toward the compression contact 17. As the solder ball 11 is inserted into the socket opening 9, the sub-flap(s) eventually pass over dead center relative to the equator of the solder ball. At this point, the sub-flap(s) long enough to reach the solder ball contact 11 face the contact 11 and resist counter movement in the opposite direction of removal. As a result, at least the longer sub-flap(s) 27a function to hold the inserted solder ball contact 11 in stable engagement with the compression contact 17, as shown in FIG. 8D.

[0055] As further shown in FIG. 8D, depending on the size of the solder ball contact 11, at least some of the remaining shorter sub-flaps 27b, 27c, and 27d can resiliently return to their original positions or bend slightly in the opposite direction to bear against the solder ball contact 11 at a position slightly spaced apart from the sub-flap 27a, thus helping to further stabilize and fix the solder ball contact 11 in place between the longer and shorter sub-flaps. Hence, the sub-flaps 27a-27d are adapted to engage the solder ball contact 11 at a plurality of spaced apart positions on the outer surface of the solder ball contact 11, substantially cupping the solder ball contact 11 therebetween. Such a design helps to minimize interference between the solder ball contact 11 and the socket opening 9 and to stabilize the solder ball contact 11 within the socket opening 9 under an appropriate retention force. It will also be appreciated that depending on the variations in their diameter tolerances, the sub-flaps 27a-27d may deflect from 0 to 90 degrees relative to the plane of the socket opening 9 upon insertion of the solder ball contacts 11. In a preferred system, the sub-flaps 27a-27b establish a required pull-out force that is equal to or preferably exceeds the required insertion force of the solder ball contacts 11.

[0056] By using the socket housing 7 to securely engage and hold the solder ball contacts 11 of the DUT 13 to the corresponding compression contacts 17 of the PCB substrate, the electrical connection path between the DUT 13 and the main PCB is substantially simplified. A thin, bending cantilever arm is not required to make the electrical connection as in prior art cantilever contacts. In this configuration, the thickness of the compression contacts 17 is minimized (i.e., ~75 μm) and the filled vias 15 in the PCB substrate 5 can be significantly shortened. This effectively shortens the overall signal path between the DUT 13 and the main PCB. This not only significantly reduces the signal loss and signal reflections commonly found in conventional cantilever contacts, but has been found to significantly improve circuit performance speeds above 50 GHz.

[0057] Furthermore, in the configuration of the present invention, both the compression contacts 17 and the filled vias 15 corresponding to each socket opening 9 in the housing 7 can be constructed with a relatively uniform cylindrical cross-section. Again, as opposed to conventional cantilever contact technology, this uniform cylindrical cross-section configuration provides significant improvements in signal transmission and circuit performance speed. Additionally, the sizes of the compression contacts 17 and filled vias 15 can be relatively easily tuned and optimized for impedance matching purposes, which is not possible with conventional cantilever contacts.

[0058] As shown in Figures 9A and 9B, in yet another alternative embodiment, the elastomeric compression contact 17 may be split into separate sections, such as halves or quarters, to increase flexibility and reduce push-back force on the solder ball contact 11. In the embodiment of Figure 9A, the elastomeric compression contact 17 is formed split down the middle to form two opposing conductive resilient contact portions 17a and 17b. In Figure 9B, the elastomeric compression contact 17 is split crosswise to form four spaced apart elastomeric compression contact portions 17c, 17d, 17e, and 17f. The compression contact 17 may be split completely through its body as shown, or may only be split partially to add flexibility and provide greater gripping ability.

[0059] As best seen in FIG. 9C, when the solder ball contact 11 engages the compression contact 17 with a downward force, the elastomeric halves 17a, 17b (see FIG. 9A) or quarters 17c-17f (see FIG. 9B) deform outwardly around the lower periphery of the solder ball 11, thus gripping the ball and providing a somewhat lower push-back connection force than a full-bodied elastomeric compression contact 17. The center split allows for more slack and relaxation, thereby reducing the forced push-back force when used in applications that require such low contact forces by design. Of course, alternative and additional configurations of the elastomeric compression contact 17 are certainly contemplated to achieve various push-back force and stabilization characteristics without departing from the invention herein.

[0060] Since the socket body 3 is essentially constructed in the form of a PCB, i.e., PCB board 5, it can include copper traces and multiple power and ground layers, providing further advantages and improvements over conventional cantilever socket contact technology. As a PCB, resistors and capacitors (not shown) can be embedded within the PCB board 5, allowing such components to be advantageously located closer to the DUT 13. This can improve power integrity and current speed for high performance circuit requirements. Embedding capacitance in the PCB board of the test socket 1 also provides further advantages in addition to improved performance and EMC (electromagnetic compatibility). This can reduce the cost of the assembled product, improve manufacturing quality, improve long term reliability, and reduce the overall size of the main PCB.

[0061] As a PCB, the filled vias 15 in the PCB substrate 5 can also be configured as a coaxial structure if desired. Because of the cylindrical shape of the vias 15 and conductive compression contacts 17, each contact can use a dedicated ground layer on an inner layer of the PCB substrate and a flooded ground layer on an outer layer to create a signal surrounded by a ground shield. Again, this is not possible with conventional cantilever contact technology.

[0062] In this construction, the conductive compression contacts 17 are rigidly secured against each filled via 15 in the PCB substrate 5 adjacent the base of each corresponding socket opening 9 in the housing 7. As such, they will not tilt or move within the socket housing 7 upon insertion of the DUT 13 and are therefore less susceptible to damage than conventional cantilever contacts. This allows the test socket 1 to be used and reused for daisy-chain testing of multiple DUTs without worrying about damage or misalignment issues. Furthermore, the socket configuration of the present invention requires zero additional footprint for implementation and the socket housing 7 is fully adaptable to include other additional retention features to facilitate connection with a variety of different styles of integrated circuits.

[0063] The disclosure herein is intended to be merely exemplary in nature and, thus, variations that do not depart from the gist of the disclosure are intended to be within the scope of the disclosure. Such variations are not to be considered as departing from the spirit and scope of the disclosure, which consists of what has been shown and described herein and recited in the appended claims.

Claims

1. 1. A socket device for use in holding electronic circuit devices for testing, comprising: (a) a substrate comprised primarily of an electrically insulating material, the substrate including an array of conductive vias extending between a first side and a second side of the substrate; (b) an electrically insulative housing overlying at least a portion of the first surface of the substrate, the housing having an array of socket openings extending therethrough that are aligned with the array of vias in the substrate; (c) a resiliently compressible conductive compression contact in electrical contact with one of the vias of the substrate and seated within each of the socket openings; (d) at least one retention member formed in the housing along a periphery of each of the socket openings, the at least one retention member being configured to hold a protruding circuit contact of the electronic circuit device in an engaged relationship with the compression contact when the circuit contact is inserted into its corresponding socket opening.

2. 2. The socket device of claim 1, wherein said compression contacts are formed at least in part from an elastomeric material having conductive particles embedded therein.

3. 2. The socket device of claim 1, wherein said compression contacts are configured in the form of small, resilient buttons having a generally uniform cylindrical cross-section throughout and a contact surface which traverses a substantial portion of said socket opening.

4. 2. The socket device of claim 1, wherein said compression contacts have contoured contact surfaces that aid in positioning and stabilizing said circuit contacts on said electronic circuit device.

5. 2. The socket device of claim 1, wherein said compression contacts are divided into a plurality of flexible sections that surround corresponding circuit contacts of said electronic circuit device.

6. 2. The socket device of claim 1, wherein said retention member includes a plurality of flexible flaps projecting inwardly from said periphery of said socket opening.

7. 7. The socket device of claim 6, wherein at least one of said flexible flaps has a different size than the other of said flaps to accommodate said circuit contacts of different sizes.

8. 7. The socket device of claim 6, wherein at least one of said flaps includes a plurality of sub-flaps of different sizes to accommodate said circuit contacts of different sizes.

9. 7. The socket device of claim 6, wherein at least one of said flaps limits the diameter of said socket opening at said periphery to a diameter slightly less than a corresponding maximum diameter of said circuit contact received therein.

10. 10. The socket device of claim 9, wherein one of the flaps is adapted to flex toward the compression contact when engaged by the circuit contact, and another of the flaps is adapted to engage the circuit contact at a location further spaced from the compression contact to help stabilize the circuit contact within the socket opening.

11. 2. The socket device of claim 1, wherein said substrate is configured in the form of a printed circuit board, each of said vias on said second surface thereof being electrically connected to a protruding electrical contact.

12. 1. A socket device for use in holding electronic circuit devices for testing, comprising: (a) a socket body having an underlying substrate configured in the form of a printed circuit board and an overlying socket housing configured from an electrically insulating material; (b) the substrate includes a plurality of conductive vias extending through the substrate that align with a plurality of socket openings extending through the housing; (c) each of the socket openings in the housing has a base disposed adjacent to and in communication with a corresponding via in the substrate, and a socket entry opposite the base adapted to receive a protruding circuit contact of the electronic circuit device into the socket opening; Furthermore, the socket device (d) a conductive contact formed at least in part from an elastomeric material and disposed in each of the socket openings adjacent the base for electrical contact with a corresponding via in the underlying substrate; (e) at least one retention member formed on the housing along a periphery of the socket entrance of each of the socket openings for holding corresponding circuit contacts of the electronic circuit device in engaging relationship with the conductive contacts disposed within the socket openings.

13. 13. The socket device of claim 12, wherein said conductive contact has a generally uniform cylindrical cross-section throughout and a contact surface that traverses a substantial portion of said socket opening.

14. 14. The socket device of claim 13, wherein said contact surface is contoured to match an outer periphery of said circuit contacts of said electronic circuit device that contact said contact surface.

15. 13. The socket device of claim 12, wherein the conductive contacts are divided into a plurality of flexible sections adapted to surround at least a portion of a periphery of the circuit contacts of the electronic circuit device with which the conductive contacts engage.

16. 13. The socket device of claim 12, wherein said retention member includes a plurality of flexible projections extending inwardly from said periphery of said socket entry of each of said socket openings.

17. 17. The socket device of claim 16, wherein at least some of said projections have a different size than other of said projections to accommodate circuit contacts of different sizes.

18. 17. The socket device of claim 16, wherein at least some of the projections include a series of fingers of different lengths which engage the outer periphery of the circuit contact when the circuit contact is inserted into the corresponding socket opening at different locations along an axis extending between the socket entry and the base of the socket opening.

19. 1. A socket device for use in holding electronic circuit devices for testing, comprising: (a) a socket body having an underlying substrate in the form of a printed circuit board having multiple power layers and ground layers, and an overlapping socket housing made of an electrically insulating material; (b) the substrate includes a plurality of conductive vias extending through the substrate that align with a plurality of socket openings extending through the housing, at least some of the vias being electrically connected to at least some of the power and ground layers within the substrate; (c) each of the socket openings in the housing has a base disposed adjacent to and in communication with a corresponding via in the substrate, and a socket entry opposite the base adapted to receive a protruding circuit contact of the electronic circuit device; Furthermore, the socket device (d) a resiliently compressible conductive contact disposed in each of the socket openings adjacent the base and in electrical contact with a corresponding one of the vias in the underlying substrate; (e) the conductive contacts are configured in the form of small elastomeric buttons having a generally uniform cross-sectional shape and a contact surface that traverses a substantial portion of the socket opening within which the conductive contacts are disposed; Furthermore, the socket device (f) a plurality of retention members projecting radially inwardly from the housing along a periphery of the socket entry of each of the socket openings for retaining corresponding circuit contacts of the electronic circuit device in mating relationship with the conductive contacts disposed within the socket openings; (g) a socket device, wherein said plurality of retention members have finger portions of different lengths for receiving and retaining said circuit contacts of different sizes.

20. 20. The socket device of claim 19, wherein the circuit contacts of the electronic circuit device are solder ball contacts, and the contact surfaces of the conductive contacts are contoured to mate with outer peripheral surfaces of the solder ball contacts in contact with the contact surfaces.

21. 21. The socket device of claim 20, wherein the fingers of different lengths engage the solder ball contacts at different positions along an axis extending between the socket entrance and the base of the socket opening when the solder ball contacts are inserted into the corresponding socket openings.

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