Test Socket for Semiconductor Integrated Circuit

Abstract

The IC test socket includes a socket body, rotating contacts, and an elastomeric retainer. The socket body has a top surface facing the IC and a bottom surface facing the load board. The socket body defines a slot extending from the top surface to an opening in the bottom surface. The rotating contacts are disposed in the slot. The elastomeric retainer captures the rotating contacts within the socket body and includes a rounded portion about which the rotating contacts rotate. The elastomeric retainer receives a translational force from the rotating contacts to compress when the elastomeric retainer translates from a free state to a pre-loaded state when engaged with the load board, and receives a rotational force from the rotating contacts to compress when the elastomeric retainer rotates from a pre-loaded state to a loaded state when engaged with the IC.

Description

Technical Field

[0001] The field of the present disclosure generally relates to test sockets for semiconductor integrated circuits, and more specifically to test sockets having rotational contacts that translate, or "scrub," on contact pads of an integrated circuit being tested.

Background Art

[0002] Semiconductor integrated circuits (ICs) are manufactured in various packages, or chip configurations, including, for example, the quad flat no-leads (QFN) package, which is common in many IC applications and is produced in large quantities. The manufacture of any quantity of ICs generally includes testing the ICs in a manner that simulates the end-user applications of those ICs. One way to test an IC is to connect each IC to a printed circuit board (PCB) that exhibits the contacts and various functionalities of the IC. The PCB, sometimes referred to as a load board, can be reused to test many ICs. A basic component of the load board that enables such testing is an IC test socket that can be reused many times to test a large number of ICs. The test socket electrically and mechanically connects the IC to the load board. The extent to which a test socket can be reused is quantified, for example, by how many "cycles" it can withstand without degrading performance such as signal performance. Each time an IC is inserted or placed in the test socket, it is called one cycle. Generally, over many cycles, the electrical and mechanical characteristics of the contacts and structure of the test socket begin to degrade as a result of, for example, oxidation, abrasion, compression, tension, or other forms of wear. Such degradation ultimately affects the integrity of the test itself, at which point the test socket reaches the end of its useful life. Accordingly, a test socket that maintains good electrical and mechanical performance over a long life cycle is desired.

Summary of the Invention

[0003] In one aspect, a test socket for a flat leadless semiconductor IC comprises a socket body, a rotary contact, and an elastomeric holder. The socket body comprises an upper surface configured to face the flat leadless semiconductor IC and a bottom surface opposite the upper surface and configured to face a load board. The socket body defines a slot extending from the upper surface to an opening in the bottom surface. The rotary contact is disposed within the slot. The rotary contact is configured to translate between a free state and a pre-load state and to rotate about a round portion of the elastomeric holder between the pre-load state and a load state. The elastomeric holder captures the rotary contact within the socket body. The elastomeric holder is configured to be compressed by receiving a translational force from the rotary contact when translating from the free state to the pre-load state upon engagement with the load board, and to be compressed by receiving a rotational force from the rotary contact when rotating from the pre-load state to the load state upon engagement with the flat leadless semiconductor IC.

[0004] In another aspect, a test system comprises a load board and a test socket. The test socket comprises an upper surface configured to face a semiconductor IC and a bottom surface attached to the load board. The socket body defines a slot extending from the upper surface to an opening in the bottom surface. The rotary contact is disposed within the slot in a pre-load state. The rotary contact is configured to rotate about a round portion of the elastomeric holder between the pre-load state and a load state. The elastomeric holder captures the rotary contact within the socket body. The elastomeric holder is configured to compress between the socket frame and the rotary contact and to be further compressed by receiving a rotational force from the rotary contact when rotating from the pre-load state to the load state upon engagement with the semiconductor IC.

[0005] In yet another aspect, a method of assembling a test system for a semiconductor IC is provided. The method includes disposing a plurality of rotary contacts within corresponding slots of a socket body of a test socket. The method includes disposing an elastomeric holder above the rotary contacts. The method includes attaching a socket frame above the plurality of rotary contacts and the elastomeric holder.

Brief Description of the Drawings

[0006]

Figure 1

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Best Mode for Carrying Out the Invention

[0007] Embodiments of the test socket described herein provide a rotary contact that generates a scrub on the contact pads of the IC when the load board and the IC during testing are engaged. The described test socket is configured to receive a flat leadless IC package such as a QFN IC, where the scrub on the contact pads of the IC desirably reduces the contact electrical resistance of the electrical connection between the IC and the rotary contact of the test socket. Conversely, the test socket described herein generally minimizes translation or scrub by the rotary contact on the PCB contacts of the load board.

[0008] FIG. 1 is a cross-sectional view of an example of an IC test system 100 for testing a semiconductor IC 102. The IC 102 is one or more electronic circuits packaged in a single semiconductor chip that generally includes a plurality of contact pads 104 for conducting signals to and from circuits within the package. The IC test system 100 includes a load board 106 to which a test socket 108 is attached. The load board 106 includes PCB contacts 110 that will connect the IC 102 to a load circuit or test circuit (not shown) integrated with the load board 106. The test socket 108 is a reusable interface for connecting multiple units of the IC 102 to the load board 106. FIG. 2 is a perspective view of the test socket 108 for a QFN IC such as the IC 102. The test socket 108 includes a socket body 112 that defines a receptacle 114 for receiving the IC 102. In some embodiments of the test socket 108, the socket body 112 includes guide walls 116 that can be linear or tapered to guide the IC 102 into the receptacle 114 to ensure proper alignment of the contact pads 104 and the PCB contacts 110. More specifically, the guide walls 116 align the contact pads 104 with corresponding contacts (not shown) within the test socket 108. The contacts of the test socket 108 extend through the socket body 112 to electrically connect each of the contact pads 104 of the IC 102 to the corresponding PCB contacts 110 on the load board 106.

[0009] FIG. 3 is a cross-sectional view of one embodiment of the rotary contact 300 within the test socket 108 (shown in FIG. 1) in a free state, i.e., before the test socket 108 is attached to the load board 106 and before the IC 102 is installed. FIG. 4 is a cross-sectional view of the rotary contact 300 in a pre-loaded state, i.e., when the test socket 108 is attached to the load board 106 but the IC 102 has not yet been installed. FIG. 5 is a cross-sectional view of the rotary contact 300 in a loaded state, i.e., when the test socket 108 is attached to the load board 106 and the IC 102 is installed in the receptacle 114. FIG. 6 is a perspective view of the rotary contact 300 separated from the test socket 108. The rotary contact 300 is composed of a conductive material such as, for example, copper, copper alloy, aluminum, aluminum alloy, steel, or other conductive metals, or some combination thereof.

[0010] The rotary contact 300 is installed in a slot 302 within the socket body 112. The rotary contact 300 extends from the receptacle 114 to an opening 304 within the socket body 112, where it engages with the PCB contact 110 in a protruding manner. The rotary contact 300 includes a surface 306 and an arm 308 that respectively rest on the surface 310 and the support end 312 of the socket body 112 when the rotary contact 300 is in a free state. The rotary contact 300 is captured within the slot 302 by an elastomeric retainer 314 that holds or biases the rotary contact 300 with respect to the surface 310 and the support end 312. The elastomeric retainer 314 provides a force to maintain a good connection between the rotary contact 300 and the contact pad 104 of the IC 102 and between the rotary contact 300 and the PCB contact 110 of the load board 106.

[0011] The rotary contact 300 terminates at a first end having a tip 316 that engages, translates, or scrubs on the contact pad 104 of the IC 102, and includes a rounded end 318 that connects the tip 316 to the lower surface of the arm 308. The rotary contact 300 terminates at a second end opposite the tip 316 and having a round claw 320 and a flat portion 322.

[0012] The tip 316 of the rotary contact 300 should be sharp, or "sharp", in order to enable effective scrubbing on the contact pad 104 of the IC 102. For example, in one embodiment, the tip 316 is rounded with a radius of about 0.05 millimeters (mm). More generally, the tip 316 should be rounded with a radius of 0.10 mm or less.

[0013] The rounded end 318 that connects the tip 316 to the lower surface of the arm 308 of the rotary contact 300 is rounded with a sufficient radius to allow smooth movement during the assembly of the test socket 108 in the free state and to allow smooth rotational movement within the slot 302. For example, in one embodiment, the rounded end 318 has a radius of about 0.15 mm.

[0014] The arm 308 of the rotary contact is substantially straight, and in certain embodiments, the tip 316 is narrower than the opposite end of the rotary contact 300. For example, the arm 308 can be tapered, having a narrow width W near the tip 316 and a wider width W near the contact point with the PCB contact 110. The taper of the arm 308 allows for greater mechanical strength of the rotary contact 300 due to the increased width W. The taper of the arm 308 also allows for efficient current conduction by avoiding discontinuities on the surface of the rotary contact 300. Also, the width W of the arm 308 partially defines where the rotary contact 300 rests on the socket body 112 at the surface 310 and the support end 312 (having the shape of the surface 306).

[0015] When the test socket 108 is in the unloaded state, the surface 306 of the rotary contact 300 rests on the surface 310 of the socket body 112 and rises away from the surface 310 when in the pre-load state or the loaded state. The round claw 320 engages with the elastomeric holder 314 when the rotary contact moves to the pre-load state. The round claw 320 is rounded to provide smooth deformation of the elastomeric holder 314 and reduce wear of the elastomeric holder 314 during deformation. In one embodiment, for example, the round claw 320 has a radius of about 0.18 mm. More generally, the round claw 320 should have a radius of at least 0.10 mm to allow smooth deformation and minimize wear of the elastomeric holder 314.

[0016] When the test socket 108 is mounted on the load board 106 (i.e., the pre-load state shown in FIG. 4), the PCB contact 110 engages with the rotary contact 300, and the load board 106 engages with the socket body 112. When engaging with the rotary contact 300, the PCB contact 110 pushes the rotary contact 300 upward to compress the elastomeric holder 314 against the socket frame 324 of the test socket 108. More specifically, the rotary contact 300 translates toward the socket frame 324 and compresses and deforms the elastomeric holder 314 against the first top 326 and the second top 328 of the socket frame 324. The flat portion 322 of the rotary contact 300 allows smooth translation of the rotary contact 300 along the wall of the socket body 112 that partially defines the slot 302. The elastomeric holder 314 applies a pre-load force to the rotary contact 300 when engaged with the load board 106 and the elastomeric holder 314 is compressed. The pre-load force applied to the rotary contact 300 must ensure good electrical contact between the rotary contact 300 and the PCB contact 110 and be at least partially weakened by inserting the IC 102 into the receptacle 114. The amount of pre-load force provided by the elastomeric holder 314 can be customized for a given application by selecting appropriate properties of the elastomeric holder 314.

[0017] When the IC102 is inserted into or installed on the receptacle 114 of the test socket 108, the contact pad 104 engages with the tip 316 of the rotary contact 300 and presses the tip 316 downward into the slot 302 within the socket body 112. The downward movement of the tip 316 into the slot 302 causes a rotational movement of the rotary contact 300 around the elastomeric holder 314. Also, the support end 312 of the socket body 112 functions as a fulcrum or pivot point, transmitting the downward force of the IC102 into a compressive or contact force applied by the round claws 320 of the rotary contact 300 to the elastomeric holder 314, and the elastomeric holder 314 further deforms against the first top 326 and the second top 328 of the socket frame 324. Similarly, the PCB contact 110 also operates as a pivot point for transmitting the downward force of the IC102 into a rotational force for compressing the elastomeric holder 314. Since the movement of the rotary contact 300 is rotational, the round claws 320 rotate away from the wall of the socket body 112, and similarly, the tip 316 of the rotary contact 300 translates or scrubs along the contact pad 104. The scrubbing generated by the rotational movement of the rotary contact 300, more specifically the tip 316, reduces the electrical resistance of the connection between the contact pad 104 and the rotary contact 300, and ultimately reduces the contact electrical resistance of the electrical connection between the contact pad 104 of the IC102 and the PCB contact 110 of the load board 106. The rotation around the elastomeric holder 314 and across the PCB contact 110 enables a reduction of the scrubbing on the PCB pads 110 of the load board 106.

[0018] When the IC102 is removed from the receptacle 114 of the test socket 108, the elastomeric holder 314 is pre - deformed under the rotational force, returns to its pre - loaded state, reverses the rotational force of the rotary contact 300, and returns the rotary contact 300 to its pre - loaded state with a return force.

[0019] FIG. 7 is a perspective view of the rotary contact 300 (shown in FIGS. 3-6) disposed within the test socket 108 in a free state. FIG. 7 shows the contact pads 104 separated from the IC 102 and the PCB contacts 110 separated from the load board 106. The rotary contact 300 is disposed within a slot 302 defined in the socket body 112. FIG. 7 shows only the portion of the socket body 112 proximate the illustrated rotary contact 300. Embodiments of the test socket 108 can include any number of rotary contacts 300 packaged in respective slots 302 along one or more dimensions. For example, one embodiment of the test socket 108 shown in FIG. 2 is configured for a QFN IC having a plurality of rotary contacts 300 disposed at all four ends of the socket body 112. In such an embodiment, for example, the slots 302 are defined independently in the socket body 112 to limit the movement of the rotary contact 300 to a rotational movement within the plane shown in FIGS. 3-5. Conversely, in certain embodiments, the elastomeric retainer 314 and the socket frame 324 span a plurality of rotary contacts 300 disposed within respective slots 302.

[0020] The elastomeric retainer 314 provides a force to maintain a good or “tight” connection between the rotary contact 300 and the contact pads 104 of the IC 102 and between the rotary contact 300 and the PCB contacts 110 of the load board 106. The elastomeric retainer 314 includes a rounded portion 702 that engages the rotary contact 300 to generate a pre-load force. The elastomeric retainer 314 includes a square portion 704 that deforms when the rotary contact 300 transitions to a loaded state under the contact force from the IC 102 and that pushes the rotary contact 300 back to the pre-loaded state with a return force when the IC 102 is removed from the receptacle 114 of the test socket 108. The first top 326 of the socket frame 324 is positioned to be along the top, or tip, of the claw 320. Similarly, the second top 328 of the socket frame 324 is disposed to be along the centerline of the rounded portion 702 of the elastomeric retainer 314.

[0021] FIG. 8 is a flow diagram of a method 800 of assembling the test socket 108 shown in FIGS. 3 - 5 and 7. The rotary contacts 300 are placed (802) within corresponding slots 302 of the socket body 112. Each rotary contact 300 is placed on a surface 310 and a support end 312. Next, an elastomeric retainer 314 is placed above the rotary contacts 300 (804) to capture the rotary contacts 300 between the elastomeric retainer 314 and the socket body 112. The socket frame 324 is attached above the rotary contacts 300 and the elastomeric retainer 314 (806) to hold both the elastomeric retainer 314 and the rotary contacts 300 in place. When the rotary contacts 300 are in a free state, i.e., before the test socket 108 is attached to the load board, the elastomeric retainer 314 is not compressed. The test socket 108 is then attached (808) to the load board 106 to transition the rotary contacts 300 from the free state to a pre - load state. The rotary contacts 300 translate towards the socket frame 324 in the pre - load state, compressing the elastomeric retainer 314 against the socket frame 324. More specifically, the elastomeric retainer 314 compresses and deforms against a first top 326 and a second top 328 of the socket frame 324.

[0022] The semiconductor IC 102 is placed within the test socket 108 (810), transitioning the rotary contacts 300 from the pre - load state to a load state (810). The rotary contacts 300 rotate around the elastomeric retainer 314, causing the claws 320 of each rotary contact 300 to rotate against the elastomeric retainer 314 in order to compress the elastomeric retainer 314 against the socket frame 324. The tip 316 of each rotary contact 300 translates towards the corresponding contact pad 104 of the semiconductor IC 102.

[0023] When the semiconductor IC 102 is removed from the test socket 108, the rotary contact 300 rotates so as to return to the pre-loading state. When transitioning from the loaded state to the pre-loading state, the elastomeric holder 314 releases the claw 320 and rotates so as to return toward the surface 310 of the socket body 112, thereby rotating the tip portion 316 so as to return toward the socket frame 324.

[0024] The technical effects of the systems and apparatuses described in this specification can include: (a) providing a customizable pre-loading force via an elastomeric holder; (b) enabling scrubbing against semiconductor IC contact pads when installing the IC in the test socket; (c) reducing the contact electrical resistance between the test socket and the IC by introducing scrubbing when installing the IC in the test socket; and (d) reducing scrubbing against the PCB contacts of the load board by means of rotary contact.

[0025] In the foregoing specification and the following claims, numerous terms having the following meanings are referenced.

[0026] As used herein, an element or step recited in the singular and preceded by the word "a" should be understood as not excluding a plurality of elements or steps, unless such exclusion is explicitly recited. Further, reference to an "exemplary implementation" or "one implementation" of the present disclosure is not intended to be construed as excluding the existence of additional implementations that also incorporate the recited features.

[0027] "Any" or "optionally" means that the subsequent recited event or circumstance may or may not occur, and that the description includes both examples where the event occurs and examples where it does not.

[0028] Throughout the specification and claims of this application, approximating language that may be used to modify any quantitative representation can vary within an acceptable range that does not alter the basic function to which the term relates. Accordingly, a value modified by one or more terms such as "about", "substantially", and "approximately" should not be limited to the exact value specified. In at least some instances, the approximating language may correspond to the precision of the instrument used to measure the value. Throughout the specification and claims, limitations of ranges may be combined or interchanged. Such ranges are identified and include all sub-ranges contained therein unless the context or language indicates otherwise.

[0029] Unless otherwise specified, disjunctive language such as the phrase "at least one of X, Y, or Z" is generally understood within the context in which it is used to state that an item, term, etc. can be X, Y, or Z, or any combination thereof (e.g., X, Y, and / or Z). Thus, such disjunctive language is not generally intended to, and should not, imply that a particular embodiment requires at least one of each of X, at least one of each of Y, or at least one of each of Z for their respective existence. Further, disjunctive language such as the phrase "at least one of X, Y, and Z" is understood to mean X, Y, Z, or any combination thereof including "X, Y, and / or Z" unless otherwise specified.

[0030] The systems and methods described herein are not limited to the specific embodiments described herein. Rather, the components of the system and / or the steps of the method can be utilized separately and independently of other components and / or steps described herein.

[0031] Certain features of various embodiments of the present disclosure are shown in some drawings and not in others, but this is merely for convenience. In accordance with the principles of the present disclosure, any feature of any drawing may be referenced and / or claimed in combination with any feature of any other drawing.

[0032] This specification uses examples to provide details regarding the disclosure, including the best mode, and to enable any person skilled in the art to practice the disclosure, including making and using any apparatus or system and performing any incorporated method. The patentable scope of the present disclosure is defined by the claims and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that are different from the literal language of the claims, or if they include equivalent structural elements that are substantially different from the literal language of the claims.

Claims

1. A test socket for a flat leadless semiconductor integrated circuit (IC), comprising a socket body having an upper surface configured to face the flat leadless semiconductor IC and a bottom surface configured to face a load board on the opposite side of the upper surface, the socket body defining a slot extending from the upper surface to an opening in the bottom surface; a socket body, a rotary contact disposed in the slot, the rotary contact being configured to translate between a free state and a pre-load state, and the rotary contact being configured to rotate between the pre-load state and a load state; a rotary contact, an elastomeric holder for capturing the rotary contact within the socket body, the elastomeric holder having a rounded portion around which the rotary contact rotates, the elastomeric holder being configured to compress upon receiving a translational force from the rotary contact when translating from the free state to the pre-load state upon engagement with the load board, and the elastomeric holder being configured to compress upon receiving a rotational force from the rotary contact when rotating from the pre-load state to the load state upon engagement with the flat leadless semiconductor IC; an elastomeric holder, a socket frame defining a receptacle configured to receive the flat leadless semiconductor IC, the socket frame being disposed above the elastomeric holder, and the elastomeric holder being configured to compress upon receiving a translational force from the rotary contact against a first top portion and a second top portion protruding from the socket frame toward the load board; a socket frame, a test socket comprising.

2. The test socket according to claim 1, wherein the rotary contact has a tip portion proximate to the upper surface of the socket body, and the tip portion is configured to engage a contact pad of the flat leadless semiconductor IC when the rotary contact rotates from the pre-load state to the load state. A test socket.

3. The test socket according to claim 2, wherein the tip portion of the rotary contact is configured to translate with respect to the contact pad of the flat leadless semiconductor IC when the rotary contact rotates from the pre-load state to the load state. A test socket.

4. In the test socket according to claim 2, the rotary contact further includes a claw at an end opposite to the tip end, and the claw is configured to move away from the wall of the socket body when the rotary contact rotates from the pre-load state to the load state. Test socket.

5. In the test socket according to claim 2, the rotary contact a round protrusion that is close to the bottom surface of the socket body and is configured to engage with a printed circuit board (PCB) pad of the load board when in the pre-load state and the load state. Round protrusion, an arm extending between the tip end and the round protrusion, and the arm is configured to rotate on a support end of the socket body within the slot. Arm, The test socket further comprising

6. In the test socket according to claim 1, the elastomer holder is configured to be compressed by receiving a rotational force from the rotary contact with respect to the socket frame. Test socket.

7. A test system for a semiconductor integrated circuit (IC), the test system a load board, a test socket, and the test socket a socket body having an upper surface configured to face the semiconductor IC and a bottom surface attached to the load board, and the socket body defines a slot extending from the upper surface to an opening in the bottom surface. Socket body, a rotary contact disposed in the slot in a pre-load state, the rotary contact being configured to rotate between the pre-load state and the load state. Rotary contact, an elastomer holder that captures the rotary contact within the socket body, the elastomer holder including a round portion configured to rotate around the rotary contact and a square portion that provides a contact force and a return force to the rotary contact, and the elastomer holder is compressed between the socket frame and the rotary contact, and the elastomer holder is configured to be further compressed by receiving a rotational force from the rotary contact when rotating from the pre-load state to the load state when engaging with the semiconductor IC. Elastomer holder, A socket frame that defines a receptacle configured to receive the semiconductor IC, the socket frame being disposed above the elastomeric holder, the elastomeric holder being configured to be compressed by receiving a translational force from the rotary contactor against a first top and a second top that project from the socket frame toward the load board, the socket frame; A test system comprising. **Claim 8** The test system according to claim 7, wherein the rotary contactor comprises a tip portion proximate to the upper surface of the socket body, the tip portion being configured to engage a contact pad of the semiconductor IC when the rotary contactor rotates from the pre-load state to the load state. **Claim 9** The test system according to claim 8, wherein the tip portion of the rotary contactor is configured to translate with respect to the contact pad of the semiconductor IC when the rotary contactor rotates from the pre-load state to the load state. **Claim 10** The test system according to claim 8, wherein the rotary contactor further comprises a claw at an end opposite to the tip portion, the claw being configured to move away from the wall of the socket body when the rotary contactor rotates from the pre-load state to the load state. **Claim 11** The test system according to claim 8, wherein the rotary contactor Is a round protrusion proximate to the bottom surface of the socket body, configured to engage a printed circuit board (PCB) pad of the load board when in the pre-load state and the load state, the round protrusion; An arm extending between the tip portion and the round protrusion, the arm being configured to rotate on a support end of the socket body within the slot, the arm; The test system further comprising. **Claim 12** The test system according to claim 7, wherein the socket frame comprises a tapered guide wall configured to align the contact pads of the semiconductor IC with the rotary contactors. **Claim 13** A method of assembling a test system for a semiconductor integrated circuit (IC), the method comprising: Placing a plurality of rotary contactors in corresponding slots of a socket body of a test socket; placing an elastomer holder above the rotary contactor; attaching a socket frame above the plurality of rotary contactors and the elastomer holder, the socket frame defining a receptacle configured to receive the semiconductor IC, the elastomer holder being configured to be compressed by receiving a translation force from at least one of the plurality of rotary contactors against a first top and a second top protruding from the socket frame toward the load board; A method comprising.

14. The method according to claim 13, wherein arranging the plurality of rotary contactors includes arranging each rotary contactor of the plurality of rotary contactors on a support end of the socket body.

15. In the method according to claim 13, attaching the socket body to the load board; translating the plurality of rotary contactors toward the socket frame in a pre-load state to compress the elastomer holder against the socket frame; A method further comprising.

16. In the method according to claim 15, placing the semiconductor IC into the test socket; rotating the plurality of rotary contactors around the elastomer holder in a loaded state, thereby rotating the claws of each rotary contactor on the elastomer holder to compress the elastomer holder against the socket frame; A method further comprising.

17. The method according to claim 16, wherein rotating the plurality of rotary contactors includes translating a tip of each rotary contactor relative to a corresponding contact pad of the semiconductor IC.

18. The method according to claim 16, further comprising removing the semiconductor IC from the test socket and rotating the plurality of rotary contactors to return to the pre-load state.

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