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Method of making microelectronic spring contact arrayRelated Patent Categories: Metal Working, Method Of Mechanical Manufacture, Electrical Device Making, Conductor Or Circuit Manufacturing, Contact Or Terminal Manufacturing, By Assembling Plural Parts, Forming Array Of Contacts Or TerminalsMethod of making microelectronic spring contact array description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20060191136, Method of making microelectronic spring contact array. Brief Patent Description - Full Patent Description - Patent Application Claims
BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] The present invention relates to methods of making microelectronic spring contact arrays, such as contact arrays for connecting to semiconductor devices (singulated or unsingulated), for purposes of testing or assembly. [0003] 2. Description of Related Art [0004] Microelectronic spring contact arrays such as used for contacting C4 or flat pad terminals of semiconductor devices have previously been made in various different ways. Some older techniques involve the assembly of fine, stiff components, such as tungsten wires, onto a base, such as a probe card. Techniques using tungsten wire and like components are generally limited to contact arrays with relatively few contacts, because of practical difficulties associated with achieving and maintaining a precise contact tip alignment across the array. [0005] A more recent method, involving forming composite spring contacts on a substrate using a relatively soft, fine wire that is coated with a layer of stiffer material, is capable of producing higher contact densities than the older tungsten wire techniques. The composite contacts may be formed directly on a contactor base or tile, or may be formed on a sacrificial substrate and transferred to a contactor base later. In the case of composite contacts that are transferred, loose contacts may be assembled to the contactor base or tile using a "pick-and-place" technique (i.e., by individual handling), or by gang-transferring to a contactor substrate. In a gang-transfer technique, the composite spring contacts are first formed tips-down on the sacrificial substrate. Then, while still attached to the sacrificial substrate, the contacts are first attached to a contactor substrate at their bases, and then, the sacrificial substrate is removed. [0006] Composite contacts are subject to some limitations. The shape of composite contacts is somewhat limited by the wire shaping process. Also, the soft wire core of each composite contact generally requires individual shaping before being coated with stiffener. This may slow down the process of making an array, particularly for arrays that include many thousands of such contacts. [0007] In yet another method, microelectronic spring contacts are formed on a contactor base using lithographic techniques that are similar to techniques for making semiconductor devices. The contactor base is coated with one or more sacrificial layers, and the sacrificial layers are patterned to define a contoured surface extending up through the sacrificial layers from the contactor base of each desired contact. A suitable spring contact material is then deposited on each contoured surface, and the sacrificial layers are removed to reveal freestanding spring contacts. Lithographic techniques have the advantage of enabling more varied shapes to be used for spring contacts, as well as eliminating the need for individual handling of the spring contacts. However, relatively complex lithographic processes may be needed to make spring contacts of certain shapes, and to achieve certain configurations of spring contacts on contactors, such as overlapping contacts. [0008] In some prior art methods, the composite and lithographic methods described above are combined to form a spring contact that includes both a composite portion, and a lithographically formed portion. Combination methods combine certain advantages of composite and lithographic methods, while still being subject to the disadvantages of both. [0009] It is desirable, therefore, to provide a method of making microelectronic spring contact arrays that overcomes the limitations of prior art methods. SUMMARY OF THE INVENTION [0010] The present invention provides a method of making microelectronic spring contact arrays that overcomes the limitations of prior art methods. According to the method, spring contacts of the desired shape are formed on a flat sacrificial substrate by patterning a sacrificial layer on the substrate according to the desired spring profile. The entire spring contact (or plurality of contacts) may be formed using a single patterning step. In the alternative, multiple patterning steps may be used, if desired. A suitable spring material is deposited in the patterned layer, and then the sacrificial substrate and layer are removed to reveal free (unattached) spring contacts. The free spring contacts may be attached to a contactor or tile base using a pick-and-place method, or by a mass assembly method. In some embodiments, the spring contacts may be attached directly to a semiconductor device. Optionally, the spring contacts may be provided with separate contact tip structures or additional coatings. [0011] A more complete understanding of the method of making microelectronic spring contact arrays will be afforded to those skilled in the art, as well as a realization of additional advantages and objects thereof, by a consideration of the following detailed description of the preferred embodiment. Reference will be made to the appended sheets of drawings which will first be described briefly. BRIEF DESCRIPTION OF THE DRAWINGS [0012] FIG. 1 is a flow diagram showing exemplary steps of a method according to the invention. [0013] FIGS. 2A-2B are plan and cross-sectional views, respectively, showing a suitable sacrificial substrate for use with the method. [0014] FIGS. 3A-3B are plan and cross-sectional views, respectively, showing the sacrificial substrate covered by a patterned layer of sacrificial material. [0015] FIGS. 4A-4B are plan and cross-sectional views, respectively, showing exemplary spring contacts attached to the sacrificial substrate after the sacrificial layer is removed. [0016] FIG. 5A is a plan view showing the exemplary spring contacts after being freed from the sacrificial substrate. [0017] FIG. 5B is a perspective view of a free spring contact in relation to a tapered recess of a base substrate, according to an alternative embodiment of the invention. [0018] FIG. 5C is a plan view of a double-armed free spring contact prior to assembly to a base substrate, according to an alternative embodiment of the invention. [0019] FIGS. 6A-6B are plan and cross-sectional views, respectively, showing an exemplary base of insulating material for mounting to the spring contacts. [0020] FIGS. 7A-7C are side cross-sectional views showing the exemplary base with springs contacts inserted therein during exemplary steps of an attachment process. [0021] FIG. 8 is a side cross-sectional view showing the base and attached array of spring contacts attached to terminals of an electronic component. Continue reading about Method of making microelectronic spring contact array... Full patent description for Method of making microelectronic spring contact array Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Method of making microelectronic spring contact array patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. 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