The Invention relates to testing integrated circuits or electronic devices, and more particularly relates to docking a test head with a peripheral.
In the manufacture of integrated circuits (ICs) and other electronic devices, testing with automatic test equipment (ATE) is performed at one or more stages of the overall process. Special handling apparatus is used which places the device to be tested into position for testing. In some cases, the special handling apparatus may also bring the device to be tested to the proper temperature and/or maintain it at the proper temperature as it is being tested. The special handling apparatus is of various types including, for example, “probers” for testing unpackaged devices on a wafer and “device handlers” for testing packaged parts; herein, the terms “handling apparatus” or “peripherals” will be used to refer to all types of such apparatus. The electronic testing itself is provided by a large and expensive ATE system that includes a test head, which is required to connect to and dock with the handling apparatus. The Device Under Test (DUT) requires precision, high-speed signals for effective testing; accordingly, the “test electronics” within the ATE which are used to test the DUT are typically located in the test head which must be positioned as close as possible to the DUT. DUTs are continually becoming increasingly complex with increasing numbers of electrical connections. Furthermore, economic demands for test system throughput have led to systems that test a number of devices in parallel.
These requirements have driven the number of electrical connections between a test head and a peripheral into the thousands and the size and weight of test heads has grown accordingly. Presently, test heads may weigh from several hundred pounds to as much as two or three thousand pounds. The test head is typically connected to the ATE's stationary mainframe by means of a cable, which provides conductive paths for signals, grounds, and electrical power. In addition, the test head may require liquid coolant to be supplied to it by way of flexible tubing, which is often bundled within the cable. Further, certain contemporary test heads are cooled by air blown in through flexible ducts or by a combination of both liquid coolants and air. In the past, test systems usually included a mainframe housing power supply instruments, control computers and the like. Electrical cables couple the mainframe electronics to “pin electronics” contained in the test head. The cabling between the mainframe and the test head increases the difficulty of manipulating the test head precisely and repeatably into a desired position. Several contemporary systems now place virtually all of the electronics in the movable test head while a mainframe may still be employed to house cooling apparatus, power supplies, and the like. Thus, the increased number and spatial density of electrical contacts to be mated combined with the increased size and weight of the test head and its cable make it more difficult to accurately and repeatably position a test head with respect to a peripheral.
In testing complex devices, either individually or many in parallel, hundreds or thousands of electrical connections have to be established between the test head and the DUT or DUTs. These connections are usually accomplished with delicate, densely spaced contacts. In testing unpackaged devices on a wafer, the actual connections to the DUT or DUTs are typically achieved with needle-like probes mounted on a probe card. In testing packaged devices, it is typical to use one or more test sockets mounted on a “DUT socket board.” Herein, the term “DUT adapter” will be used to refer to the unit that holds the part or parts that make actual electrical connections to the DUT or DUTs. The DUT adapter must be precisely and repeatably positioned with respect to the peripheral in order that each of a number of DUTs may be placed, in turn, into position for testing.
Test systems may be categorized in terms of how the DUT adapter is held. Presently, in many systems the DUT adapter is fixed appropriately to the handling apparatus, which typically includes reference features to aid in accurately locating it. Herein, these systems will be referred to as “peripheral-mounted-DUT-adapter” systems. In other systems the DUT adapter is attached to the test head and positioned with respect to the handling apparatus by appropriately positioning (i.e., docking) the test head. These latter systems will be referred to as “test-head-mounted-DUT-adapter” systems. There are two possible subcategories of test-head-mounted-DUT-adapter systems. In the first subcategory, the DUT or DUTs are positioned before the test head is positioned or docked. Thus, the act of positioning the test head brings the connection elements into electrical contact with the DUT. This arrangement may be suitable for wafer scale testing, where the peripheral first positions a wafer and then the test head and DUT adapter (here a probe card configured to probe many or all of the devices on the wafer) is then positioned with respect to the wafer so that the needle-like probes contact the DUTs. In the second subcategory, the test head and DUT adapter are positioned or docked first, and this is followed by the peripheral moving DUTs in turn into position for testing as the DUT adapter remains in position.
It is to be noted that the DUT adapter must also provide connection points or contact elements with which the test head can make corresponding electrical connections. This set of connection points will be referred to as the DUT adapter electrical interface. Further, the test head is typically equipped with an electrical interface unit that includes contact elements to achieve the connections with the DUT adapter electrical interface. Typically, the test head interface contact elements are spring-loaded “pogo pins,” and the DUT adapter receiving contact elements are conductive landing pads. However, other types of connection devices may be incorporated for example for RF and/or critical analog signals. In some systems such other types of connectors are used in combination with pogo pins. The cumulative force required to compress hundreds or thousands of pogo pins and/or to mate other styles of contacts can become very high. This can be objectionable as the force required to bring the contacts into connection may be unreasonable and the force placed on the DUT adapter could cause undesirable deflections. Accordingly, alternative connection techniques, such as zero-insertion-force techniques, have been under development. For example, U.S. Pat. No. 6,833,696 (assigned to Xandex, Inc.) discloses a system having electrical contacts formed on substrates combined with mechanisms to bring corresponding contacts into engagement without placing undue force on a probe card or DUT board. It is further anticipated that in the future Micro Electromagnetic Machine (MEMs) techniques may be employed to form electrical contacts as an extension of their present use in fabricating probe cards. Overall, the contacts are very fragile and delicate, and they must be protected from damage.
In overview (more detailed descriptions will be provided further on) docking is the process of maneuvering the test head into position with respect to the peripheral for testing. In peripheral-mounted-DUT-adapter systems, docking includes properly and precisely conjoining the contact elements of the test head interface unit with their respective connection elements on the DUT adapter. In these systems, the delicate and fragile test head interface contacts must be afforded protection during the positioning and docking process. However, in test-head-mounted-DUT-adapter systems, the goal of docking is to precisely position and locate the DUT adapter with respect to the peripheral and/or DUTs. Also to be noted in test-head-mounted-DUT-adapter systems, the conjoining of the test head interface contact elements with the DUT adapter connection elements is accomplished when the DUT adapter is attached to the test head, and the contact elements are thus protected. However, the very delicate, needle-like probes of a probe card or the fragile, precisely manufactured test sockets are exposed during positioning and docking, and these too require protection.
Test head manipulators may be used to maneuver the test head with respect to the handling apparatus. Such maneuvering may be over relatively substantial distances on the order of one meter or more. The goal is to be able to quickly change from one handling apparatus to another or to move the test head away from the present handling apparatus for service and/or for changing interface components. When (as outlined above) the test head is held in a position with respect to the handling apparatus such that all of the connections between the test head the DUT adapter have been achieved and/or the DUT adapter is in its proper position, the test head is said to be “docked” to the handling apparatus. In order for successful docking to occur, the test head must be precisely positioned in six degrees of freedom with respect to a Cartesian coordinate system. Most often, a test head manipulator is used to maneuver the test head into a first position of coarse alignment within approximately a few centimeters of the docked position, and a “docking apparatus” is then used to achieve the final precise positioning.
Typically, a portion of the docking apparatus is disposed on the test head and the rest of it is disposed on the handling apparatus. Because one test head may serve a number of handling apparatuses, it is usually preferred to put the more expensive portions of the docking apparatus on the test head. The docking apparatus may include an actuator mechanism that draws the two segments of the dock together, thus docking the test head; this is referred to as “actuator driven” docking. The docking apparatus, or “dock” has numerous important functions, including: (1) alignment of the test head with the handling apparatus, including the precise alignment of electrical contacts, (2) sufficient mechanical advantage and/or actuator power to pull together, and later separate (i.e., undock), the test head and the handling apparatus, (3) providing pre-alignment protection for electrical contacts during both docking and undocking operations, and (4) latching or holding the test head and the handling apparatus together.
According to the in TEST Handbook (5th Edition©1996, in TEST Corporation), “Test head positioning” refers to the easy movement of a test head to a handling apparatus combined with the precise alignment to the handling apparatus required for successful docking and undocking. A test head manipulator may also be referred to as a test head positioner. A test head manipulator combined with an appropriate docking means performs test head positioning. This technology is described, for example, in the aforementioned in TEST Handbook. This technology is also described in numerous patent publications, for example a partial list includes U.S. Pat. Nos. 7,728,579, 7,554,321, 7,276,894, 7,245,118, 5,931,048, 5,608,334, 5,450,766, 5,030,869, 4,893,074, 4,715,574, and 4,589,815 as well as WIPO publications such as WO05015245A2 and WO08103328A1, which are all incorporated by reference for their teachings in the field of test head positioning systems. The foregoing patents and publications relate primarily to actuator-driven docking. Test head positioning systems are also known where a single apparatus provides both relatively large distance maneuvering of the test head and final precise docking. For example, U.S. Pat. No. 6,057,695 to Holt et al., and U.S. Pat. Nos. 5,900,737 and 5,600,258 to Graham et al., which are all incorporated by reference, describe a positioning system where docking is “manipulator-driven” rather than actuator-driven. However, actuator-driven systems are the most widely used, and the present invention will be described in terms of such a system; however, those of reasonable skill will note that the invention is adaptable to manipulator-driven systems.
As previously stated, the goal of test head docking is to properly locate and position the test head with respect to the peripheral. The peripheral normally includes features, such as mounting surfaces that define a “peripheral docking plane.” The electrical contacts that connect to the DUT (and hence the DUT adpter, DUT socket board or probe card) must lie in a plane parallel to the peripheral docking plane. To facilitate docking, the docking apparatus that is mounted on the peripheral is typically located on a flat metallic plate that is attached to the peripheral such that its outer surface is parallel to the peripheral docking plane. Also the peripheral may include other reference features, such as precisely located pins or receptacles, to enable properly locating the DUT adapter.
Similarly, a “test-head docking plane” may be associated with the test head. The test head interface contact elements are typically arranged in a plane parallel to the test-head docking plane. A Cartesean coordinate system may be associated with either the test-head or peripheral docking plane such that the X and Y-axes lie in a plane parallel to the docking plane and the Z axis is perpendicular to the docking plane. Distances in the Z direction may referred to as height. It is to be noted that there may be more than one set of test head interface contact elements with the plane of each set being at a different height with respect to the docking plane. In the remainder of this document the term “docking plane” is used without a modifier it refers to the peripheral docking plane.
When properly docked, the test-head docking plane is substantially parallel to the peripheral docking plane. The process of achieving this relationship is often known as planarization and the result may be referred to as “docked planarity.” Also, when properly docked, the test head is at a predetermined preferred “docked distance” from the peripheral. Achieving docked planarity and docked distance requires three degrees of motion freedom of the test head, namely: rotations about axes parallel to the X and Y axes associated with the test-head docking plane and linear motion along the Z axis. Finally, when properly docked, the two docking planes will be aligned in the remaining three degrees of freedom corresponding to the X and Y directions as well as with respect to rotation about an axis parallel to the Z axis.
In the typical actuator-driven positioning system, an operator controls the movement of the manipulator to maneuver the test head from one location to another. This may be accomplished manually by the operator exerting force directly on the test head in systems where the test head is fully balanced in its motion axes, or it may be accomplished through the use of actuators directly controlled by the operator. In several contemporary systems, the test head is maneuvered by a combination of direct manual force in some axes and by actuators in other axes.
In order to dock the test head with the handling apparatus, the operator must first maneuver the test head to a “ready-to-dock” position, which is close to and in approximate alignment with its final docked position. The test head is further maneuvered until it is in a “ready-to-actuate” position where the docking actuator can take over control of the test head's motion. The actuator can then draw the test head into its final, fully docked position. In doing so, various alignment features provide final alignment of the test head. A dock may use two or more sets of alignment features of different types to provide different stages of alignment, from initial to final. It is generally preferred that the test head be aligned in five degrees of freedom before the fragile electrical contacts make mechanical contact. The test head may then be urged along a straight line, which corresponds to the sixth degree of freedom, that is perpendicular to the plane of the interface and peripheral docking plane.
As the docking actuator is operating (and while the dock alignment features are not imposing constraints), the test head is typically free to move compliantly in several if not all of its axes to allow final alignment and positioning. For manipulator axes which are appropriately balanced and not actuator driven, this is not a problem. However, actuator driven axes generally require that compliance mechanisms be built into them. Some typical examples are described in U.S. Pat. Nos. 5,931,048, 5,949,002, 7,084,358, and 7,245,118 as well as WIPO publication WO08137182A2 (all incorporated by reference). Often compliance mechanisms, particularly for non-horizontal unbalanced axes, involve spring-like mechanisms, which in addition to compliance add a certain amount of resilience or “bounce back.” Further, the cable connecting the test head with the ATE mainframe is also resilient leading to further bounce back effects. As the operator is attempting to maneuver the test head into approximate alignment and into a position where it can be captured by the docking mechanism, he or she must overcome the resilience of the system, which can often be difficult in the case of very large and heavy test heads. Also, if the operator releases the force applied to the test head before the docking mechanism is appropriately engaged, the resilience of the compliance mechanisms may cause the test head to move away from the dock.
U.S. Pat. No. 4,589,815 to Smith (incorporated by reference), discloses a prior art docking mechanism. The docking mechanism illustrated in FIGS. 5A, 5B, and 5C of the '815 patent uses two guide pin and receptacle combinations to provide final alignment and two circular cams. The guide pin receptacles are located in gussets that also hold cam followers which engage with the cams. To achieve a ready-to-actuate position, the cams must be fitted between the gussets such that the cam followers can engage helical cam slots located on the cams' cylindrical surfaces. Fitting the cams between the gussets provides a first, coarse alignment and also provides a degree of protection to the electrical contacts, probes or sockets as the case may be. When the cams are rotated by handles attached to them, the two halves of the dock are pulled together with the guide pins becoming fully inserted into their mating receptacles. A wire cable links the two cams so that they rotate in synchronism. The cable arrangement enables the dock to be operated by applying force to just one or the other of the two handles. The handles are accordingly the docking actuator in this case.
The basic idea of the '815 dock has evolved as test heads have become larger into docks having three or four sets of guide pins and circular cams. These are known as three-point and four-point docks respectively.
Other prior art docks, such as those manufactured by Reid Ashman, Inc., are similar in concept but utilize linear cams in lieu of circular cams and solid links instead of cables to synchronously drive the cams. Another scheme that utilizes linear cams but which is actuated by pneumatic elements is described in U.S. Pat. No. 6,407,541 to Credence Systems Corporation (incorporated by reference). In the '541 patent, “docking bars” serve a similar purpose to the previously described “gussets.”However, when the test head is docked, the docking bars do not bear against the unit being docked to; thus, the interaction between the cam followers and the cams solely determines the docked distance and docked planarity.
Still other variations of docks are known. For example, a partially automated dock that may be operated in either partially or fully powered modes and which incorporates cable-driven circular cams is disclosed in U.S. Pat. Nos. 7,109,733 and 7,466,122 (both incorporated by reference), both to the present assignee. A further dock configuration including solid link driven circular cams and which may be powered is described in WIPO publication WO2010/009013A2 (incorporated by reference), also to the present assignee. These docks utilize guide pins and receptacles to establish position within the plane and gussets or the equivalent to establish docked planarity and the docked distance between the test head and the peripheral.
Additionally, the docks described in U.S. Pat. Nos. 5,654,631 and 5,744,974 utilize guide pins and receptacles to align the two halves. However, the docks are actuated by vacuum devices, which urge the two halves together when vacuum is applied. The two halves remain locked together so long as the vacuum is maintained. However, the amount of force that can be generated by a vacuum device is limited to the atmospheric air pressure multiplied by the effective area. Thus, such docks are limited in their application.
U.S. Pat. Nos. 7,235,964 and 7,276,895 (both incorporated by reference) to the present assignee describe docks that use relatively large alignment pins (as illustrated in FIG. 14 of the '895 patent), which are typically attached to the peripheral. The diameter of the pins is relatively narrow at their distal ends and is larger at the interior ends. Also, two cam followers are attached to the pins near the point where they are attached to the peripheral. Camming mechanisms, employing linear cams, are attached to the test head. The distal ends of the alignment pins may be first inserted into the camming mechanisms to provide a first stage of course alignment. As the test head is urged closer to the peripheral, the larger diameter enters the camming mechanism to provide closer alignment. As the test head is further urged towards the peripherals, the cam followers eventually engage the cams, which may then be actuated to pull the two halves into a final docked position. No gussets are involved; the docked distance and docked planarity are solely determined by the interaction between the cams and cam followers. Further, it is necessary for the camming mechanisms to serve as pin receptacles, providing sufficient interaction with the pins to position the test head in three degrees of freedom parallel to the peripheral docking plane.
In all of the docks that have been mentioned, including both actuator driven and manipulator driven, alignment of the test head within a plane parallel to the docking plane is determined by the fit of guide pins within their respective receptacles. In order to facilitate many cycles of docking and undocking, the guide pins are usually designed to have a diameter that is a few thousandths on an inch smaller than that of their receptacle. Thus the accuracy and repeatability of the final docked position of the test head is limited to at least typically three to five thousandths of an inch with respect to the peripheral docking plane. While this has been acceptable for many past and contemporary test systems, the demand for systems having greatly improved accuracy and especially repeatability is expected to grow.
As previously indicated, the purpose of docking in a peripheral-mounted-DUT-adapter system is to precisely mate the test head electrical interface with the DUT adapter electrical interface. Each electrical interface and defines a plane, which is typically, but not necessarily, nominally parallel with the distal ends of the electrical contacts. When docked these two planes must be parallel with one another. Normally, the DUT adapter is fabricated as a planar circuit board and is desirably fixed to the peripheral in a plane parallel to the peripheral's docking plane. Thus, when docked, the plane of the test head electrical interface must also be parallel to the peripheral docking plane. In order to prevent damage to the electrical contacts, it is preferred to first align the two interfaces in five degrees of freedom prior to allowing the electrical contacts to come into mechanical contact with one another. If in the docked position the defined planes of the interfaces are parallel with the X-Y plane of a three-dimensional Cartesian coordinate system, alignment must occur in the X and Y axes and rotation about the Z axis (Theta Z or Yaw), which is perpendicular to the X-Y plane, in order for the respective contacts to line up with one another. Additionally, the two planes may be made parallel by rotational motions about the X and Y axes (Pitch and Roll). The process of making the two electrical interface planes parallel with one another is called “planarization” of the interfaces; and when it has been accomplished, the interfaces are said to be “planarized” or “co-planar.” Once planarized and aligned in X, Y and Theta Z, docking proceeds by causing motion in the Z direction perpendicular to the peripheral docking plane.
Similarly, the purpose of docking in test-head-mounted-DUT-adapter systems is to precisely position the test head so that the DUT adapter is properly located with respect to the peripheral. The DUT adapter's probe tips or socket contacts constitute an electrical test interface, which defines a plane that must be planarized with the peripheral's docking plane. Further, the electrical test interface must be precisely aligned with respect to the X and Y axes of the docking plane and with respect to rotation about the Z axis. As with the previous case, it is preferred that alignment in these five degrees of freedom occurs before final positioning in the Z direction.
In the process of docking, the test head is first maneuvered into proximity of the peripheral. Further maneuvering brings the test head to a “ready to dock” position where, in many systems, some first coarse alignment means is approximately in position to be engaged. Still further maneuvering will bring the test head to a “ready to actuate position,” where the docking mechanism may be actuated. At the ready to actuate position, approximate planarization and alignment in X, Y and Theta Z have been achieved. As the dock is actuated, alignment and planarization become more precise. With further actuation, alignment and planarization are finalized to a degree of accuracy determined by the alignment features. This is then followed by continued motion in the Z direction, bringing the test head into its final docked position. Further details with regards to specific selected docks are described in the detailed description of the invention, to follow. It is noted that in manipulator driven docking, as described in the previously mentioned U.S. Pat. Nos. 6,057,695, 5,900,737 and 5,600,258, sensors detect the equivalent of a ready to actuate position in order to change from a coarse positioning mode to a fine positioning mode. Thus, to one of ordinary skill in the art, sensing a ready to actuate position in an actuator-driven dock would be a natural extension (intuitive and obvious) of what is taught and disclosed by the '695, '737 and '258 patents.
Docks of the types described above have been used successfully with test heads weighing up to and over one thousand pounds. However, as test heads have become even larger and as the number and spatial density of contacts has exponentially increased, a number of problems have become apparent. Immediately apparent is the increased demand for positional accuracy and repeatability. Further, the force required to engage the contacts and maintain them in position increases as the number of contacts increases. Typically a few ounces per contact is required; thus docking a test head having 1000 or more contacts requires in excess of 100 or 200 pounds for this purpose. In view of the present few thousandths of an inch “slop” in dock design, these forces combined with the relatively unpredictable bounce-back effects due to the resilience in the manipulator compliance mechanism and the test head cable make it increasingly difficult to repeatability and accurately perform test-head docking.
The field of “exact-constraint” or “kinematic” couplings, which, through the works of Lord Kelvin and James Clerk Maxwell, dates to the mid 19th century or before, offers techniques for providing rigid and repeatable connections or couplings between two objects. Such techniques when applied to test-head docking, may provide improved accuracy and repeatability. A number of texts, academic papers, commercial publications, patent publications, and internet-published presentations provide information on the design and application of kinematic couplings. General principles of kinematic couplings may be found in the following references, each of which is incorporated herein by reference:
Technical Papers—Hart, A. J., Slocum, A. H., Willoughby, P., “Kinematic Coupling Interchangeability,” Precision Engineering, 2004, 28:1-15; Slocum, A. H., “Design of Three-Groove Kinematic Couplings,” Precision Engineering, April 1992, Vol. 14, No. 2, pp 67-76; Culpepper, M. L., “Design of Quasi-Kinematic Couplings,” Precision Engineering, 2008: 338-357; Slocum, A. H. and Donmez, A, “Kinematic Couplings for Precision Fixturing—Part 2: Experimental determination of repeatability and stiffness,” Precision Engineering, July 1988, Vol. 10, No. 3; U.S. Pat. No. 5,678,944 to A. H. Slocum, et al.
Further, companies such as Ball-tek, Div. Of Micro Surface Engr., Inc., Los Angeles, Calif. (http://www.precisionballs.com), and g2 engineering (formerly Gizmonics, Inc.), Mountain View, Calif. (http://www.g2-engineering.com), supply a variety of components for the purpose of constructing kinematic or exact-constraint type couplings and apparatus. Herein, as an aid to understanding the present invention, we provide a brief overview of the basics of the field.
Definitions of “kinematic coupling” vary somewhat from work to work; also the term “kinematic” is used to describe other types of mechanical designs. Thus, some authors prefer to use terms such as “exact constraint” or “deterministic” as replacements or modifiers. In the remainder of this disclosure the terms exact-constraint and kinematic will be used interchangeably and often together. Briefly the terms kinematic or exact-constraint couplings refer to couplings between objects that constrain relative motion and hence position in desired degrees of freedom, usually without redundancy or over constraint, and that require a force to urge and hold the objects together. An important benefit of the technique is that it allows repeatability that may exceed by orders of magnitude the tolerances to which the components of the coupling are fabricated.
Characteristics of kinematic/exact-constraint couplings include alignment features that engage at discrete points of contact, such as a spheroidal surface contacting a planar surface or two spheroidal surfaces contacting one another. Generally, provided that the contact points are properly disposed, one point of contact is necessary to constrain each desired degree of freedom. Thus, six points of contact are sufficient to constrain six degrees of motion freedom. In other situations, features that provide discrete lines of contact may be utilized; these are sometimes, but not always, referred to as “quasi-kinematic.” Depending on the configuration, a line of contact may replace one or more points of contact. A line of contact may also somewhat over constrain the system, thereby somewhat reducing the potential repeatability.
There are two basic or traditional configurations of exact-constraint/kinematic couplings, which are depicted in
The second configuration shown in
As an aid to further discussion some further general information and terminology is now introduced. Usually a kinematic coupling includes a number of pairs of features. One member of each pair is attached to the first of the units to be coupled and the other member is attached to the other unit. Thus, in the three-Vee coupling there are three pairs of ball-groove combinations, with the balls being attached to one unit and the grooves to the other. More generally each member of the pair includes one or more surfaces, and the surfaces are designed such that when they are engaged with one another they make contact at discrete points or along discrete lines. To aid in discussion the surface(s) of one member of a pair may be referred to as “contact surface(s),” and the surface(s) of the other member may be referred to as “mating surface(s).” Thus each side of a groove in a three-Vee coupling could be called a contact surface, and the ball could be called the mating surface (or vise versa). Other shapes may be used to form surfaces; for example a gothic arch could be used in place of a flat-sided Vee-groove. It is also not necessary that a ball be used as a mating surface. Other shapes, such as the tip of a cone, can be made to contact a surface at a single point or along a line. Examples of other pairs of surfaces include a ball pressing against a flat surface providing a single point of contact and a ball pressing against a tetrahedron providing three points of contact as previously described with regards to the Kelvin Clamp configuration. Yet another possibility is a ball pressing against three balls providing three points of contact. Different types of contacts may be used in one coupling as long as they are sufficient to control the desired degrees of freedom.
Numerous other configurations of exact-constraint/kinematic couplings are known, many employing alternatively shaped features for various purposes and applications. The reader is referred to the previously listed publications and component suppliers such as the aforementioned Ball-tek and g2 engineering for further information. However, further details regarding exact-constraint/kinematic couplings will be presented as needed and/or appropriate in this specification. Also included for its teachings is U.S. Pat. No. 5,678,944, which describes a “flexural mount” kinematic coupling; various aspects of this disclosure are also mentioned in the present specification as appropriate. It is important to note that the alignment features used in the previously described prior art docks are not of this type because they are designed to have a certain amount of “slop” to facilitate repetitive docking and undocking with minimal effort; and, thus, are not motion or position constraining. In this regard, we may refer to alignment features that use exact-constraint/kinematic coupling principles as “position-constraining” features.
It is also worthy to note that while six points of contact may be sufficient to constrain a rigid object in six degrees of freedom, additional constraints may be necessary in situations where one or both of the objects being coupled is subject to flexing under load.
Exact-constraint or kinematic coupling techniques have also been employed in certain test systems and test system apparatus. For example the apparatus disclosed in U.S. Pat. Nos. 5,821,764, 5,982,182, and 6,104,202 (all included by reference) use three-Vee kinematic coupling techniques to provide the final alignment between the two halves. Coarse alignment pins may also be included to provide an initial alignment. The coarse alignment pins may be provided with a catch mechanism, which captures the guide pin in its hole and prevents it from escaping. The catch mechanism appears to activate automatically in the '764 and '202 patents; whereas, a motor driven device is utilized for each of the three coarse alignment pins in the '182 patent. Also in the '182 patent, the three motors may be operated separately to effect planarization between the docked components. In all three patents, a linear actuator is used to finally pull the two halves together. The linear actuator is disclosed as being of the pneumatic type. In docks of this type, it is necessary that another mechanism be used to provide enough pre-alignment to prevent damage to the fragile electrical contacts. For this reason the aforementioned coarse alignment pins are used. Thus, two sets of alignment features are provided, namely: (1) coarse-alignment, loose fitting pin-receptacle combinations, and (2) a kinematic coupling. Although kinematic couplings provide highly precise repeatability in positioning two entities, a difficulty with docks of the type described in the '764 and '202 patents is that initially adjusting the kinematic coupling components so that the necessary positional accuracy in all six degrees of freedom can be burdensome. That is, the positions of the Vee-grooves and balls must be carefully calibrated to control X,Y and rotational position in the docking plane as well as the final docked distance and docked planarity of the two halves. However, the separate control of the actuators in the '182 patent enable a means of independently adjusting the docked planarity and docked distance parameters.
Yet another example of the use of kinematic coupling techniques is in U.S. Pat. No. 6,833,696 (to Xandex, Inc.) and its siblings (all included by reference), which disclose a test system docking mechanism. In this system, three spherical balls are compliantly attached to the test head side with spring mechanisms. Three Vee-groove units, also attached to the test head, are located between the balls and the test head. In an undocked position, the balls do not contact these Vee-grooves. A second set of three Vee-grooves is attached to the peripheral side. In docking, coarse alignment means are used to guide the test head and three balls into proximity to the grooves mounted on the peripheral, and an actuator is connected to pull the test head further towards the peripheral. The balls then engage the peripheral set of grooves. As the actuator further moves the test head, the balls move against the compliance towards the test head until they finally become sandwiched between the two sets of grooves, which defines the final docked position. In this system, calibration of the final docked position requires the adjustment of two opposing sets of three grooves and one set of three compliantly mounted spheres. Furthermore, the system, having a total of 12 points of contact, appears to be disadvantageously over-constrained. In such an over-constrained system, one set of contacts could “fight” another resulting in degraded repeatability.
Still another example is provided by U.S. Pat. No. 5,828,225 to Tokyo Electron Limited of Japan. The disclosed system includes apparatus for locating a test head with respect to a wafer prober. An exact-constraint coupling technique is used as next summarized. Three spherical units are mounted on the test head, disposed at the corners of an approximate equilateral triangle. Two Vee-groove units are disposed on the peripheral so as to receive two of the spherical units. An inverted cone is disposed on the peripheral so as to receive the third spherical unit with a circular line of contact. Thus, a (somewhat over-constrained) six-degree-of-freedom constraining coupling is provided. The two Vee-groove units are mounted on actuators, which are attached to the peripheral. The actuators are configured to move the Vee-grooves linearly in the Z-direction; i.e., towards or away from the test head. The inverted cone is not movable in the Z-direction. The actuators may be controlled by a controller to adjust the height of each Vee-groove to establish planarity between the two halves in response to information sensed by an appropriate sensing apparatus. While such adjustment takes place, the test head may pivot about the third sphere, located within the inverted cone feature.
As noted, it is necessary that a force is applied to urge the features together and to maintain the contact. This is known as a “preload” force. In some circumstances gravity may serve as a preload force. In other circumstances, specific apparatus such as springs may be used. The preload force produces reaction forces at the points or lines of contact between the surfaces. Components of these reaction forces may lie in a plane and in directions to constrain the relative position of the objects being coupled. The forces that may be applied to a kinematic coupling may be high enough to cause Herzian deformations at the points or lines of contact, transforming them to areas of contact and possibly degrading repeatability over time and operation cycles.
The inventors have recognized that it would be desirable to retain this simplicity and proven techniques in a highly precise dock having positional constraint for large test heads. The cam-actuated docks, mentioned previously and to be described in more detail later, combine pre-alignment with gussets and cams, close alignment in the docking plane with guide pins and receptacles, docking planarization and distance control by the cams and gussets, and mechanical advantage and locking with cams and cam followers, all using relatively simple mechanisms. Highly precise docking is achieved utilizing compliant position constraining features.
The invention provides significant improvement to the accuracy and repeatability that is available in contemporary and prior art docks. Accordingly, the details of a typical, exemplary prior art docking system will first be described. This will be followed by a description of an exemplary embodiment of the invention utilized in conjunction with a similar docking system. Additional exemplary embodiments and applications of the invention will also be discussed, and a novel method of docking illustrated by these embodiments will be described. It is to be understood that numerous styles and configurations of docking apparatus are known (many of which having been previously mentioned) and that one of ordinary skill in the art may be expected to be able to readily apply the inventive concepts to such systems. As the discussion proceeds, a number of alternatives will be mentioned, but these are not meant in any way to be limiting to the scope of the invention. The description is done with the aid of the figures which are intended to be illustrative and are not necessarily drawn to scale nor are they intended to serve as engineering drawings.
To begin, selected details of an exemplary prior art dock are illustrated in
Referring to
Handler apparatus 108 includes reference features 131, which in this case may be bushing-lined holes disposed at precise locations with respect to its lower surface 109. The inside diameter of the bushing may typically be approximately ¼ inch to ⅜ inch. Reference features 131 are for properly aligning DUT adapter 144 with handler apparatus 108 so that the handling apparatus's positioning mechanism can effectively place DUTs in contact with the test socket(s) or probes. For example, DUT adapter 144 may be designed with corresponding holes so that temporary dowel pins can hold DUT adapter 144 in position while it is fastened to handler apparatus 108 with appropriate fasteners. Once it is fastened, the temporary dowels may be removed, if desired. Furthermore, reference features 131 may be utilized to align signal contact ring 142 with handler apparatus 108 and DUT adapter 144. Thus, corresponding reference pins 133 are mounted on signal ring 142. To facilitate relatively easy insertion, the full diameter of reference pins 133 is typically a few thousandths of an inch less than the inside diameter of the bushings of reference features 131. Also, reference pins 133 are normally tapered at their distal ends. These two properties facilitate their entry into and a sliding fit with respect to the bushings of corresponding reference features 131. Preferably, the apparatus is designed so that when reference pins 133 are fully conjoined with reference features 131, the electrical contacts of electrical interface 126 are aligned with and in full conductive contact with their corresponding respective electrical contacts of interface 128. A primary goal of docking is to maneuver test head 100 into a position that provides such alignment and to maintain that position while testing.
Although a specific configuration of reference features has been described, those familiar with the field will recognize that other arrangements are both possible and in use. For example, the locations of reference pins and receptacles could be reversed with the pins placed on the peripheral side and receptacles incorporated on the test head side. The essential role of the reference features is to aid in the initial set up of the docking apparatus by providing initial alignment to within a few thousandths of an inch between the two halves. Once that has been achieved, their use for alignment in repetitive docking operations may be optional, provided that the docking apparatus has equivalent or superior alignment means. The locations of the reference features may also vary. To illustrate, in certain instances the peripheral-side reference features may be integral to the peripheral as described above with respect to
Still referring to
Gusset plate 114 is attached to the exterior surface 109 of handler apparatus 108. Gusset plate 114 is mounted so as to be parallel with the peripheral docking plane of handler apparatus 108. Gusset plate 114 has a central opening and is attached to handler apparatus 108 so that DUT adapter 144 and electrical interface 128 are accessible. Four gussets 116 are attached to gusset plate 114, one located near each of its four corners. A typical gusset is shown in
Four docking cams 110 are rotatably attached to test-head face plate 106. Cams 110 are circular and are similar to those described in the '815 patent. A typical cam is shown in
A circular cable driver 132 with an attached docking handle 135 is also rotatably attached to face plate 106. Docking cable 115 is attached to each of the cams 110, and to cable driver 132. Idler pulleys 137 appropriately direct the path of the cable to and from cable driver 132. Cable driver 132 can be rotated by means of applying force to handle 135. As cable driver 132 rotates it transfers force to cable 115, which in turn causes cams 110 to rotate in synchronism. Other means of operating the cams are also known. These include, for example, powered actuators as described in U.S. Pat. Nos. 7,109,733 and 7,466,122 and/or solid links as described in WIPO publication No. WO 2010/009013A2, all assigned to in TEST Corporation.
As previously mentioned, extending from the circular-arc cutout 117 of each gusset 116 is a cam follower 110a. Each cam follower 110a fits into the upper cutout 125 on the upper face of its respective cam 110. As cams 110 are rotated, cam followers 110 follow their respective helical groves 129, thus urging test head 100 into its docked position. Docking apparatus using linear cams is also known. Examples include docks manufactured by Reid Ashman, Inc. Also linear cams are described in U.S. Pat. No. 6,407,541 to Credence Systems Corporation as well as in U.S. Pat. Nos. 7,235,964 and 7,276,895 to in TEST Corporation.
The overall docking sequence will be described with reference to
In
In
The accuracy and repeatability of positioning the contacts with respect to one another is therefore mainly a function of accuracy and repeatability in the X-Y plane. It is observed that the closeness of the fit of reference features 131 and 133 in conjunction with the fit between guide pins 112 and guide-pin receptacles 112a determines the final alignment between the handler electrical interface 128 and the test head electrical interface 126. The respective fits of these features should be such that they may engage and disengage without undue force or binding. Also, it is preferable to avoid interference between the sets of features as they sequentially become engaged and disengaged. For example, there should preferably be enough looseness of fit between guide pins 112 and guide-pin receptacles 112a so that the engagement of reference features 131 and 133 does not cause binding of guide pins 112 within guide-pin receptacles 112a. Accordingly guide pins 112 must be precisely placed on face plate 106 with respect to both the reference features 133 and gussets 116. To facilitate this, guide pins 112 may be attached in a manner that allows their position to be adjusted. A manner of doing this which is widely practiced is described in the '815 patent. To aid in this calibration procedure, a calibration fixture having features to engage reference features 133 as well as through-bores sized to receive guide pins 112 and that are spaced apart according to the gusset 116 layout may be employed. Such techniques are well known in the art. Overall, a docking accuracy and repeatability with respect to the X-Y plane in the range of a few thousandths of an inch is typically achievable. That is to say, a few thousandths of an inch of “slop” is present in the system. It is to be noted that once guide pins 112 have been calibrated into a proper position, the use of reference features 131 and 133 may not be necessary in docking. This depends in part on the nature of the fit between reference features 131 and 133, and the situation has led some users in certain applications to not utilize these features in docking. Thus, for purposes of this specification they may be considered as optional.
In summary, an initial coarse alignment between gussets 116 and cams 110 to within a fraction of an inch is sufficient to enable the tapered ends of guide pins 112 to engage respective receptacles 112a and to allow cam followers 110a to enter cam cutouts 125. Rotation of cams 110 causes the full diameter of guide pins 112 to interact with receptacles 112a, controlling three degrees of freedom with respect to the X-Y plane, while the cam slots 127 interacting with cam followers 110s control the remaining three degrees of freedom, namely, height and planarity (pitch and roll). In the final docked position, alignment of these height and planarization degrees of freedom has been transferred to and controlled by gussets 116. Accuracy and repeatability with respect to height and planarity are acceptable for present and perceived future applications. However, as previously discussed, accuracy and repeatability in X, Y, and Theta Z of a few thousandths of an inch is considered by many to be problematical for state-of-the-art and future applications.
Before proceeding to describe embodiments of the invention, it is useful to review some information about the movement of the cam followers.
With reference to
As described in the literature of exact-constraint/kinematic couplings, including various previously mentioned publications and patent documents, the sloping sides 213a,b may be replaced by other shapes, such as a gothic arch, to provide two points of contact with an engaging spheroidal surface. An orientation axis 215 may be associated with each groove block 211. Orientation axis 215 is parallel to and coincident with the upper surface of base region 214 and is also parallel to and midway between sloping sides 213a,b. Preferably groove blocks 211 are arranged on gusset plate 114 such that their three respective orientation axes 215 intersect at or near the center of peripheral-side electrical interface 128. It is also desirable that the three groove blocks 211 are located at the corners of a triangle that is as close as reasonably possible to an equilateral triangle. Base portion 214 includes counter-bored screw holes 216; screws passing through holes 216 and threaded into gusset plate 114 may be used for securing blocks 211. If holes 216 are made somewhat oversized relative to the screws, the positions of blocks 211 may be adjusted as need be.
An exemplary compliant feature unit 220 is shown in assembled and exploded perspective views in
Compliant feature units 220 are attached to face plate 106 so that their housings 222 are located on the side of face plate 106 that faces away from the peripheral 108 and so that the distal portions of shafts 124 extend through face-plate holes 271 and point in the direction of the peripheral 108. Compliant feature units 220 are attached to face plate 106 with appropriate screws (not illustrated) that extend through appropriate holes in face plate 106 and which are received by threaded holes 221 in the periphery of first end region 223 of housing 222. Further, compliant feature units 220 are disposed on face plate 106 so that, when test head 100 is docked to peripheral apparatus 108 in a desired position, spherical ends 126 of shafts 124 contact the sloping sides 213a,b of groove blocks 211 in the manner of a kinematic ball-and-groove coupling.
To work effectively, however, the axes of shafts 224 must be approximately pre-aligned so as to approximately orthogonally intersect the orientation axes 215 of their respective groove blocks 211 before spherical ends 226 are brought into actual physical contact with groove sides 213a,b. Preferably, such pre-alignment should be to within a few thousandths of an inch to ensure smooth operation and to prevent undue wear to the components by allowing them to scrape against one another. By applying existing, prior art docking techniques, this goal may be readily achieved.
The overall docking sequence will be described with reference to
In
The result of further rotating cams 110 is shown in
In
The final docked position, shown in
In the foregoing discussion and figures, it has been presumed that the reference features 131,133 would be engaged prior to engagement of the position-constraining docking features 226, 213a,b. As would be known to those experienced in the art, other embodiments could readily be construed where features 131,133 are designed such that it is preferable that they come into engagement at the same time as or after the engagement of the position-constraining features. In this case the prior alignment of the position-constraining features 226, 213a,b would guide the reference features 131, 133 into engagement. An important aspect of the invention is the engagement of position-constraining features 226, 213a,b to repeatably establish position with respect to the X-Y plane (i.e., docking plane) before the final docked position is achieved. A second important aspect is utilizing one set of features (in the present embodiment, planar surfaces 118 of gussets 116 and gusset landing areas 116a) to govern the docked distance and docked planarity and a second set of features (position-constraining features 226, 213a,b) to govern the docked X, Y, and Theta Z position. Although the present embodiment uses gussets to establish the docked distance and planarity, it is clear that the technique is applicable, with no significant changes, to systems that rely on the interaction of cams and cam followers or other means to determine these conditions.
The foregoing embodiment utilizes a kinematic or position-constraining coupling having three spherical surfaces contacting three grooved features at a total of six points. As mentioned above, other combinations of position-constraining features are also known, some (but certainly not an exhaustive list) are described in U.S. Pat. Nos. 6,729,589 and 5,821,764, 5,678,944 and 6,833,696 as well as in many of the documents listed above. Various combinations of these alternatives could readily be substituted without changing the overall scheme. Also, it is to be noted that such precision coupling schemes are generally intended to control six degrees of freedom in three-dimensional space, whereas the present invention only requires controlling three degrees of freedom in the two-dimensional docking plane, but with a preload force in the third dimension. Accordingly, a wide variety of alternative position-constraining alignment techniques may be applied in the practice of the present invention.
A second embodiment of the present invention incorporating certain alternative position-constraining alignment features will be described with reference to
In contrast to the previous discussion, however, the apparatus of
Cone block 311 is shown in larger scale in the perspective view in
The contact between hemispherical end 226′ and cone block 311 establishes the X-Y position of the axis of shaft 224′ with respect to the docking plane, gusset plate 114, and peripheral 108. Further, the interaction of hemispherical end 226″ with Vee-block 211″ establishes the angle between a line in the docking plane connecting the axes of shafts 224′ and 224″ and either the X or Y-axis of the docking plane. In other words, it constrains the test head's Theta Z or rotational degree of freedom with respect to the docking plane. Thus, the interactions between the features constrain all three degrees of freedom (X, Y, and Theta Z) of the test head with respect to the docking plane. It is to be noted that in order to constrain rotation in the plane, orientation axis 215 of Vee-block 211″ should be orientated so that the docking-plane-parallel components of the preload reaction forces at the contacts between sides 213a,b and hemispherical end 226″ generate non-zero, opposing moments about a center of rotation determined by the fit of the other hemispherical end 226′ in its contact with cone-block 311. Such moments would preferably be optimized if orientation axis 215 is arranged so that it intersects the center of rotation. This arrangement (ball-in-a-cup plus ball-in-a-groove) is related to the previously described Kelvin-clamp (reportedly originated by Lord Kelvin) form of exact-constraint or kinematic coupling. However, the Kelvin-clamp's single contact point between a spherical surface and a surface in the plane is neither necessary nor included because the cams 110 and cam followers 110a and/or gussets 116 control the docked planarity and docked distance between the docked elements. The position-constraining features provided are sufficient to control and constrain position and alignment in the three degrees of freedom (X, Y and Theta Z) with respect to the docking plane.
The docking procedure using the apparatus of
Those familiar with the field will recognize that the inventive concept is not limited by the feature sets that have been shown and described. Indeed, many alternative feature sets have been shown and discussed in the literature. For example, a straightforward alternative embodiment to the system of
The two previous exemplary embodiments of the invention illustrate its application and operation in representative peripheral-mounted-DUT-adapter systems. Test-head-mounted-DUT-adapter systems will next be considered in third and fourth exemplary embodiments.
A third exemplary embodiment is described with the help of
In the third exemplary embodiment of
In relation to the docking sequence described with respect to
In
Thus, the final docked position, shown in
A fourth exemplary embodiment is described with reference to
The docking apparatus used in the fourth exemplary embodiment incorporates ball-and-groove position-constraining features and is the same as that of the first exemplary embodiment, which was discussed in conjunction with
The steps in docking with the fourth exemplary embodiment are similar to those described for the first exemplary embodiment in conjunction with
In relation to the docking sequence described with respect to
In
Thus, the final docked position, shown in
The four exemplary embodiments (illustrated in
Step 1620 is an optional step and is thus drawn with dashed lines. In this step, means for preliminary alignment in at least three degrees of freedom corresponding to motion in a plane parallel to the docking plane are provided. These may be incorporated to aid in protecting the delicate electrical contacts and/or to provide preliminary alignment to within a few thousandths of an inch. Typical examples include prior art guide pins and receptacles as well as gussets interacting with cams. In other examples, relatively long guide pins fitted to corresponding receptacles could approximately satisfy this step and sub-step 1610b simultaneously. Strictly speaking, this step is not necessary for practicing the invention; however, it is one that many users may prefer. It is to be noted that this step is necessary in prior art systems, and the prior art may be used to accomplish it.
Step 1630 provides apparatus to precisely constrain the position of the test head in the three degrees of motion freedom in a plane parallel to the peripheral docking plane. In preferred embodiments, exact-constraint apparatus such as that which has been previously described would be utilized.
In step 1640, which is adapted from the prior art, the test head is maneuvered to a position where the actuator may be engaged to further move it into its docked position. In this position, the feature pairs of the position-constraining apparatus provided in step 1630 are not necessarily engaged. This maneuvering may be done with the assistance of a test head manipulator. In this position, the test head is approximately aligned in all degrees of freedom except one, namely, its final docked distance from the peripheral.
In step 1650, the actuator is operated moving the test head from the ready-to-actuate position to a position closer to the peripheral. The means of planarization provided at sub-step 1610b establish a substantially co-planar relationship between the test head docking plane and the peripheral docking plane. The position-constraining features provided in step 1630 are not in play at this position. It is to be noted that the planarization may occur at the ready to actuate position of step 1640; however, in many prior art systems, a relatively small, initial amount of motion of the actuation apparatus refines the planarity.
Step 1660 provides for continuing to operate the actuator from the position of step 1650 to move the test head still closer to the peripheral to a position where the respective members of the feature pairs of the position-constraining features are engaged. The planarity of the test head established at step 1650 is maintained throughout this step. If the system is a peripheral-mounted DUT adapter system, the position of the test head is far enough from the peripheral so that the electrical contacts of the test-head-side electrical interface and those of the peripheral-mounted DUT adapter are separated. If the system is a test head mounted DUT adapter system where the peripheral has positioned the DUT for testing prior to docking, the position of the test head in this step is far enough from the peripheral so that the electrical contacts are separated from the DUT. This step is not found in the prior art.
Step 1670 provides for continuing to operate the actuator to move the test head to its desired docked distance from the peripheral as determined by the apparatus provided at sub-step 1610c. During this motion, planarity is maintained by the planarization means provided at sub-step 1610b. Importantly, during this motion, the position-constraining features provided at step 1630 remain securely engaged. Thus, precise alignment is maintained in five degrees of freedom as this motion occurs. Importantly, motion in a plane parallel to the docking plain is essentially non-existent due to the interactions of the position-constraining features. Due to the compliant motion that is available to at least one member of each position-constraining feature pair, engagement between members of each feature pair is maintained without relative motion between the pair members. During the motion of this step, the respective electrical contacts of the test head electrical interface and those of the peripheral-mounted DUT adapter system become conjoined. Also the electrical test contacts of a test-head-mounted DUT adapter system may become conjoined with the DUT if the system is of the type where the DUT is positioned prior to docking.
At step 1680 the actuator is no longer operated and the system is docked. The actuator remains in a position to maintain the docked position. The position-constraining features remain securely engaged while docked as do the means establishing the docked planarization and docked distance.
In the previously described exemplary embodiments, a number of compliant position-constraining features are described; however, the invention is not limited to these specific examples. For example, numerous alternatives may be utilized in the practice of the invention by following the teachings of the numerous previously mentioned and listed references.
To begin, we recall that position constraint is a result of one set of surfaces contacting a second set of surfaces at discrete points or discrete lines of contact. Thus, at step 1710 it is specified to provide a set of “contact surfaces” on either the test head or the peripheral. For example, these may correspond to the sloping sides 213a,b of the Vee-blocks 211 mounted on the peripheral 108 of the exemplary system illustrated in
Step 1720 provides “mating surfaces” on the other system component to make contact with the contact surfaces provided in step 1710. It is specified that the contacts should be made at discrete points or along discrete lines. The step further requires that a reaction force generated by the act of holding the surfaces in contact with one another acts along a line that is not perpendicular to the peripheral docking plane. Thus, the tangent plane to a contact surface and its mating surface at a point where they make contact may not be parallel to the docking plane. In brief, the contact surface and the mating surface must be at a bevel angle with respect to the docking plane. In relation to the examples of contact surfaces previously provided, their corresponding mating surfaces would include the hemispherical ends 226, 226′ 226″ of shafts 224, 224′ & 224″ of compliant feature units 220, 220′ & 220″ in the first and second exemplary embodiments of
It is seen that subsets of the contact surfaces and subsets of the mating surfaces may be arranged in pairs forming engagable pairs of position constraining features.
A source of force for pressing the mating surfaces and the contact surfaces into firm contact with one another is provided in step 1730. This is frequently called a preload force as previously mentioned. This force, or at least a major component of it, is preferably directed perpendicularly to the docking plane. The reaction force to this applied force at the points or lines of contact between the contact surfaces and the mating surfaces must have components parallel to the docking plane in order to constrain position and motion. In the previously described exemplary embodiments this force is derived from the fluid pressure provided to cylinders 255. Other alternatives could also be applied, for example U.S. Pat. No. 6,678,944 to Slocum teaches that spring mechanisms could be used or that the surfaces themselves could be resilient, spring-like structures. Any such alternatives are within the spirit of the invention.
The location and orientation of the contact surfaces and mating surfaces is considered in step 1740. These must be arranged so that there are sufficient docking-plane-parallel reaction forces that act in locations and directions sufficient to prevent motion of and maintain the position of the test head in all three degrees of freedom parallel to the docking plane. It is also preferred that locations and orientations be selected to provide reasonable stability against unexpected externally applied forces or events. Further, it is preferred that there are no redundancies in reaction forces that would cause the system to be over-constrained, which could lead to non-repeatable behavior. As to advice on performing this and other steps, the reader is directed to the considerable literature that has been previously mentioned and listed.
Compliance is provided in step 1750, which specifies that at least one surface of a pair of contactable contact and mating surfaces has the ability to move in a direction that is substantially perpendicular to the docking plane. This is to allow the points or line of contact to move relative to the test head or peripheral as the two are moved together by the docking actuator. In the exemplary embodiments this capability is provided by the movable piston 235 within cylinder 255. U.S. Pat. No. 6,678,944 also teaches providing this capability by way of a movable piston within a cylinder. This patent further teaches fabricating one of the surfaces in a spring-like fashion to provide this capability. The teachings of the '944 patent may therefore also be used in fulfilling this step. Step 1750 may be combined with step 1730 because the means of force generation is closely related to the compliance means. However, separation into two steps provides individual focus on the two important issues.
The invention as described by the foregoing exemplary embodiments and methods provides an improvement to state-of-the-art and contemporary test head docking schemes. First, the invention provides two sets of features for controlling the docked position of the test head relative to the peripheral in all six degrees of spatial freedom. The first set, taken from the prior art, is exemplified by the use of gussets and or the interactions between cams and cam followers to control the three degrees of freedom associated with the docked planarity and docked distance of the test head. The second set, derived from the field of exact-constraint or kinematic coupling design, controls and constrains the remaining three degrees of freedom associated with the docked position of the test head in a plane that is parallel to the docking plane defined by the peripheral. The second set has been exemplified by ball and groove techniques and by modified Kelvin clamp techniques; however, as has been stated, other forms of exact-constraint coupling features are known and may be readily substituted. Because the position constraining features of the second set are only required to constrain three degrees of freedom, a full six-degree of freedom kinematic coupling is not necessary, which is demonstrated by the arrangements of the second and third exemplary embodiments. Further, the second set of features incorporates compliance that operates in a direction that is perpendicular to the docking plane. This allows the second set of features to become engaged at a distance that is away from the desired docked distance and to remain engaged, without relative motion between mated pairs of features, while the test head is moved into its final docked position. Such apparatus is then combined with the previously described method, provides greatly improved accuracy and repeatability of docking that is demanded by the advances in testing requirements for present and future integrated circuits.
The invention is not restricted to the specific structures of the exemplary embodiments. As has been mentioned, the invention is readily applicable to other forms, styles, and configurations of docking apparatus. It is also to be understood that while the exemplary embodiments show certain components on one of the peripheral or test head and corresponding components on the other of the test head or peripheral, the positions of some or all of the components could be reversed or interchanged. It is to be further understood that alternative embodiments of a compliant feature unit could be readily adapted to the present invention. For example, as has been previously mentioned, the Slocum U.S. Pat. No. 5,678,944 describes a compliant unit that incorporates internal springs rather than a pressurized fluid. Also the '944 patent shows compliant features of various types fabricated of deformable, resilient structures which could also be adapted to the present invention. As has also been previously mentioned, numerous alternative forms of exact-constraint coupling features are known and described in the literature. These provide a wide variety of alternatives to the basic forms, which have been incorporated in the exemplary embodiments. Additionally, commercial suppliers of components for implementing position-constraining features, suitable for practicing the invention, have been identified.
Although the invention is illustrated and described herein with reference to specific embodiments, the invention is not intended to be limited to the details shown. Rather, various modifications may be made in the details within the scope and range of equivalents of the claims and without departing from the invention.
Filing Document | Filing Date | Country | Kind | 371c Date |
---|---|---|---|---|
PCT/US2012/046182 | 7/11/2012 | WO | 00 | 4/4/2014 |
Number | Date | Country | |
---|---|---|---|
61506764 | Jul 2011 | US |