SOCKETS FOR "SPRINGED" SEMICONDUCTOR DEVICES

SOCKETS FOR ”SPRINGED” SEMICONDUCTOR DEVICES

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This is a continuation of commonly-owned, copending U.S. Provisional Patent Application No. 60/051, 365 filed Jun. 30, 1997.

TECHNICAL FIELD OF THE INVENTION

[0002] The invention relates to making interconnections between electronic components, especially microelectronic components and, more particularly, to interconnection elements (contact structures) exhibiting resiliency (springiness), and methods of making same.

BACKGROUND OF THE INVENTION

[0003] Commonly-owned U.S. patent application Ser. No. 08/152,812 filed 16 Nov. 93 (now U.S. Pat. No. 4,576,211, issued 19 Dec. 95), and its counterpart commonly-owned copending “divisional” U.S. patent applications Ser. No. 08/457,479 filed 01 Jun. 95 (status: pending) and Ser. No. 08/570,230 filed 11 Dec. 95 (status: pending), all by KHANDROS, disclose methods for making resilient interconnection elements for microelectronics applications involving mounting an end of a flexible elongate core element (e.g., wire “stem” or “skeleton”) to a terminal on an electronic component, coating the flexible core element and adjacent surface of the terminal with a “shell” of one or more materials having a predetermined combination of thickness, yield strength and elastic modulus to ensure predetermined force-to-deflection characteristics of the resulting spring contacts. Exemplary materials for the core element include gold. Exemplary materials for the coating include nickel and its alloys. The resulting spring contact element is suitably used to effect pressure, or demountable, connections between two or more electronic components, including semiconductor devices.

[0004] Commonly-owned, copending U.S. patent application Ser. No. 08/340,144 filed 15 Nov. 94 and its corresponding PCT Patent Application No. PCT/US94/ 13373 filed 16 Nov. 94 (WO95/14314, published 26 May 95), both by KHANDROS and MATHIEU, disclose a number of applications for the aforementioned spring contact elements, and also discloses techniques for fabricating contact pads (contact tip structures) at the ends of the spring contact elements.

[0005] Commonly-owned, copending U.S. patent application Ser. No. 08/452,255 filed 26 May 95 and its corresponding PCT Patent Application No. PCT/US95/ 14909 filed 13 Nov. 95 (WO96/17278, published 06 Jun. 96), both by ELDRIDGE, GRUBE, KHANDROS and MATHIEU, disclose additional techniques and metallurgies for fabricating spring contact elements as composite interconnection structures and for fabricating and mounting contact tip structures to the free ends (tips) of the composite interconnection elements.

[0006] Commonly-owned, copending U.S. patent application Ser. No. 08/558,332 filed 15 Nov. 95 by ELDRIDGE, GRUBE, KHANDROS and MATHIEU, and its corresponding PCT Patent Application No. US95/ 14885 filed 15 Nov.

95 by ELDRIDGE, GRUBE, KHANDROS and MATHIEU disclose methods of fabricating resilient contact structures which are particularly well-suited to fabricating spring contact elements directly on semiconductor devices. As used herein, a semiconductor device having spring contact elements mounted thereto is termed a “springed semiconductor device”.

[0007] Commonly-owned, copending U.S. Provisional Patent Application No. 60/024,555 filed 26 Aug. 96, by ELDRIDGE, KHANDROS and MATHIEU, and PCT Patent Application No. US97/08606 filed 15 May 97 by DOZIER, ELDRIDGE, KHANDROS, MATHIEU and TAYLOR disclose additional contact tip structure metallurgies and structures.

[0008] The present invention addresses and is particularly well-suited to making interconnections to modern microelectronic devices having their terminals (bond pads) disposed at a fine-pitch. As used herein, the term “fine-pitch” refers to microelectronic devices that have their terminals disposed at a spacing ofless than 5 mils, such as 2.5 mils or 65 pm. As will be evident from the description that follows, this is preferably achieved by taking advantage of the close tolerances that readily can be realized by using lithographic rather than mechanical techniques to fabricate the contact elements.

BRIEF DESCRIPTION (SUMMARY) OF THE INVENTION

[0009] As mentioned above, a semiconductor device having spring contact elements mounted thereto is termed a “springed semiconductor device”. Such a device may be interconnected to an interconnection substrate in one of two main ways. It may be “permanently” connected such as by soldering the free ends of the spring contact elements to corresponding terminals on an interconnection substrate such as a printed circuit board. Alternatively, it may be “temporarily” connected to the terminals simply by urging the springed semiconductor device against the interconnection substrate so that a pressure connection is made between the free ends of the spring contact elements and the terminals. Another way of looking at such temporary pressure connections is that the springed semiconductor device is “self-socketing”.

[0010] The ability to remove a springed semiconductor device from its temporary pressure connection with an interconnection substrate is certainly useful in the context of replacing or upgrading the springed semiconductor device. In this context, it is important that the pressure connections be robust, and capable of withstanding the wear and tear associated with normal operations. Generally, a certain minimum contact force is desired to effect reliable pressure contact to electronic components (e.g., to terminals on electronic components). For example, a contact (load) force of approximately 15 grams (including as little as 2 grams or less and as much as 150 grams or more, per contact) may be desired to ensure that a reliable electrical connection is made to a terminal of an electronic component which may be contaminated with films on its surface, or which has corrosion or oxidation products on its surface. The minimum contact force required of each spring contact element demands either that the yield strength of the spring material or that the size of the spring element are increased. As a general proposition, the higher the yield strength of a material, the more difiicult it will be to work with (e.g., punch, bend, etc.). And the desire to make springs smaller essentially rules out making them larger in cross-section.

[0011] A more fundamental object is achieved simply by making transient (very temporary) connections to a springed semiconductor device. And that is, the ability to test the springed semiconductor device prior to temporarily or permanently mounting it to an interconnection substrate of a system to (1), if necessary, bum-in the springed semiconductor device and (2) to ascertain whether the springed semiconductor device is measuring up to its specifications. As a general proposition, this can be accomplished by making “transient” pressure connections with the spring contact elements with relaxed constraints on contact force and the like. The making of such transient connections to springed semiconductor devices is the focus of the present invention. The present invention discloses a number of techniques for socketing (making transient pressure connections) to springed semiconductor devices.

[0012] According to the invention, methods and apparatuses for effecting a temporary connection to a portion of an elongate spring contact element mounted to and extending from an electronic component are provided.

[0013] In one embodiment, an interconnection substrate has a terminal which is a plated through hole. The spring contact element is inserted through the through hole so that a portion of the spring contact element is within the through hole.

[0014] Additional methods, apparatuses and embodiments thereof are disclosed herein.

[0015] Other objects, features and advantages of the invention will become apparent in light of the following description thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Reference will be made in detail to preferred embodiments of the invention, examples of which are illustrated in the accompanying drawings. The drawings are intended to be illustrative, not limiting. Although the invention will be described in the context of these preferred embodiments, it should be understood that it is not intended to limit the spirit and scope of the invention to these particular embodiments. Certain elements in selected ones of the drawings are illustrated not-to-scale, for illustrative clarity. Often, similar elements throughout the drawings are referred to by similar references numerals. For example, the element 199 may be similar in many respects to the element 299 in another figure. Also, often, similar elements are referred to with similar numbers in a single drawing. For example, a plurality of elements 199 may be referred to as 199a, 199b, 199c, etc.

[0017] FIG. 1 is a side cross-sectional view of a “springed” semiconductor device, according to the invention.

[0018] In the following figures, a springed semiconductor device is shown with spring contact elements which are mounted thereto and extend therefrom contacting corresponding terminals of an interconnection substrate. In some of the figures, the spring contact elements are shown con

tacting the terminals. Other of the figures are slightly exploded for illustrative clarity, showing the spring contact elements nearly in contact with the terminals.

[0019] FIG. 2 is a side cross-sectional view of a “springed” semiconductor device being urged against an interconnection substrate such as a printed circuit board (PCB), according to the invention.

[0020] FIG. 2A is a side cross-sectional view of another technique of urging a springed semiconductor device against an interconnection substrate, according to the invention.

[0021] FIG. 3 is a side cross-sectional view of another technique of urging a springed semiconductor device into contact with terminals of an interconnection substrate, according to the invention.

[0022] FIG. 4 is a side cross-sectional view of another technique of connecting a springed semiconductor device to terminals of an interconnection substrate, according to the invention.

[0023] FIG. 5A is a side cross-sectional view of a technique of urging a springed semiconductor device into contact with concave terminals of an interconnection substrate, according to the invention.

[0024] FIG. 5B is a side cross-sectional view of another technique of urging a springed semiconductor device into contact with concave terminals of an interconnection substrate, according to the invention.

[0025] FIG. 5C is a side cross-sectional view of another technique of urging a springed semiconductor device into contact with concave terminals of an interconnection substrate, according to the invention.

[0026] FIG. 6A is a side cross-sectional view of another technique of horizontally contacting spring contact elements extending from a springed semiconductor device with resilient contact structures extending from terminals of an interconnection substrate, according to the invention.

[0027] FIG. 6B is a bottom plan view of the apparatus of FIG. 6A, according to the invention.

[0028] FIG. 7A is a side cross-sectional view of another technique of horizontally contacting spring contact elements extending from a springed semiconductor device with pairs of resilient contact structures extending from terminals of an interconnection substrate, according to the invention.

[0029] FIG. 7B is a bottom plan view of the apparatus of FIG. 7A, according to the invention.

[0030] FIG. 7C is a bottom plan view of an alternate embodiment of the apparatus of FIG. 7A, according to the invention.

[0031] FIG. 8 is a side cross-sectional view of another technique of horizontally contacting spring contact elements extending from a springed semiconductor device with terminals of an interconnection substrate, according to the invention.

[0032] FIGS. 9A and 9B are side cross-sectional views of another technique of horizontally contacting spring contact elements extending from a springed semiconductor device with terminals of an interconnection substrate, according to the invention.

DETAILED DESCRIPTION OF THE INVENTION

[0033] FIG. 1 illustrates a “springed” semiconductor device 102, which is an electronic component having a plurality (two of many shown) of free-standing elongate microspring spring contact structures 110 mounted to and extending from a corresponding plurality (two of many shown) of terminals 104 on a surface thereof. Each spring contact element 110 extends laterally parallel to the surface of the component 102 (in the “x” and “y” axes, and extends to a height “H” in the z-axis above the surface of the component 102.

[0034] As discussed in a number of the aforementioned patents and patent applications, the springed semiconductor device 102 can be connected to another electronic component such as a printed circuit board (PCB) or other suitable interconnection substrate simply by urging the free ends (tips) 11011 of the spring contact elements 110 against corresponding terminals (not shown) on the PCB (not shown). Alteratively, the free ends (tips) of the spring contact elements 110 can be soldered to the terminals of the PCB or interconnection substrate.

[0035] FIG. 2 illustrates a technique 200 wherein the “springed” semiconductor device 102 is urged (in the direction of the arrow 212) against an interconnection substrate such as a printed circuit board (PCB) 214 so that the tips 110a come into pressure contact with a corresponding plurality (two of many shown) of terminals 216 on the PCB 214 to establish a pressure connection therewith. As mentioned above, the tips 11011 of the spring contact elements 110 can also be soldered to the terminals 216 of the PCB 214. The present invention, however, is principally directed to making temporary connections with the spring contact elements (110) of springed semiconductor devices (102).

[0036] FIG. 2, and the figures that follow, are illustrative of making temporary pressure connections to a springed semiconductor device such as for testing the semiconductor device. In this context, the semiconductor device is termed a “device under test” (DUT). In some of the figures, such as in FIG. 2, the temporary pressure connection is made in the z-axis, by applying “vertical” pressure to the tip (11011) of the spring contact element (110) in a direction which is perpendicular to the surface of the electronic component 102. In other of the figures, such as in FIG. 6A, the temporary pressure connection is made in the x or y axes, by applying “horizontal” pressure to a midportion of the spring contact element (110) in a direction which is parallel to the surface of the electronic component 102.

[0037] FIG. 2A illustrates another technique 220 for making a vertical temporary pressure connection with spring contact elements 110 of a springed semiconductor device (DUT) 102. In a manner similar to that of the technique illustrated in FIG. 2, the tips 11011 of the spring contact elements 110 make pressure connections (contact) with terminals 226 (compare 216) of a PCB 224 (compare 214), as illustrated by the arrow 228 (compare 212). In this example, the DUT 102 is housed within a metal cap (housing) 230 which is a five-sided box such that the back side (top, as viewed) of the DUT is against the bottom surface of the housing 230. The open (bottom, as viewed) end of the housing 230 is covered by a rigid planar member (substrate) 232 which has a plurality (two of many shown) of guide

holes 234 aligned with the tips 11011 of the spring contact elements 110 which extend therethrough. For example, for spring contact elements 110 having a height “H” of 50 mils, the spring contact elements 110 extend 5 mils beyond the external (bottom, as viewed) surface of the rigid planar substrate 232.

[0038] The rigid planar substrate 232 is suitably formed of silicon and the guide holes are suitably tapered with their wide ends facing the DUT 102 and the interior of the housing 230, and is suitably formed of a silicon wafer using conventional semiconductor micromachining techniques. As illustrated, the rigid planar substrate 232 is sized to extend slightly, such as 100-250 mils beyond the four (two visible in the figure) sidewalls of the housing 230, to completely cover the open (bottom, as viewed) end of the housing 230. In this manner, the DUT 102 and a major portion of each spring contact element 110 are protected from inadvertent mechanical damage, such as from handling this springed semiconductor device “subassembly” (102, 110, 232).

[0039] As illustrated in FIG. 2A, the subassembly of the DUT 102 within the housing 230 is held against the front (top, as viewed) surface of the PCB 224 by suitable mechanical means, such as spring clips 236 having two ends, one end 236a extending into or through corresponding holes 238 in the PCB 224, the other end 2361) extending over the external bottom (top, as viewed) surface of the housing 230. In this manner, a reliable desired amount of pressure can be effected between the spring contact elements 110 and corresponding terminals 226 of the PCB 224. Such an arrangement is suitable for testing (transient connection) or for more permanent demountable mounting of the subassembly (102/230) to the PCB.

[0040] In summary, there has been described in FIGS. 2 and 2A a method of effecting temporary connections to free ends (tips) of elongate spring contact elements mounted to and extending from an electronic component such as a semiconductor device by:

[0041] urging the springed semiconductor device (DUT) against an interconnection substrate (e.g., PCB) so that the tips of the spring contact elements vertically contact corresponding terminals on the PCB.

Another Vertical Technique

[0042] Commonly-owned, copending PCT Patent Application No. US95/ 14842 filed 13 Nov. 95 by Dozier, Eldridge, Grube, Khandros and Mathieu [C-5-PCT] discloses methods of removably mounting electronic components to a circuit board (interconnection substrate) by providing a socket element with solder contacts on one side thereof and with elongate free-standing spring contact elements on another side thereof, particularly for making pressure connections to corresponding balls and lands of ball grid array (BGA) and land grid array (LGA) electronic components.

[0043] FIG. 3 illustrates another technique 300 of making vertical pressure connections to tips of spring contact elements 110 of a springed semiconductor device (DUT) 102. Whereas in the techniques described with respect to FIGS. 2 and 2A the interconnection substrate (214, 224) simply had terminals against which the tips (11011) of the spring contact elements (110) were pressed, in this technique, the tips 11011 of the spring contact elements 110 are pressed against terminals 326 (compare 216) which are disposed at