MULTIPLE ROLLING CONTACTS

Abstract: A rolling contactor is described for testing electronic devices having a plurality of very closely spaced, linearly aligned terminals, e.g. ceramic chips (6) containing an array of capacitors, packaged no larger than a single 1206 chip capacitor (0.120 x 0.60). Such chips have like pluralities of linearly aligned terminals (10, 12) along opposite sides. The contactor (2) includes a plurality of juxtaposed contact wheels (20, 24), each wheel being individually suspended by a corresponding cantilever arm (52, 54). The wheels are spaced to register with a line of terminals, and the arms are resilient enough to apply, when flexed, sufficient axial force to their respective wheels to make good contact with the terminals. Two of such multiple rolling contactors can be opposally positioned for simultaneously contacting lines of terminals on opposite sides of a chip array passing therebetween. In such a case, the wheels of one contactor are positioned to impinge registered terminals along one edge of the array, while the wheels of the opposing contactor simultaneously impinge registered terminals along the opposite edge of the array.

Description: MULTIPLE ROLLING CONTACTS This application claims the benefit of U.S. Provisional Application No. 60/064,244, filed November 4, 1997. BACKGROUND OF THE INVENTION This invention relates in general to the field of cantilever type electrical contactors, and more particularly to such a connector having multiple rolling contacts for simultaneously coupling electrically with multiple terminals, i.e. contact areas, of electrical components. A conventional ''wiping" or cantilever type contactor typically has a flat metal, spring arm with a contact tip at a free end of the arm. In operation, a device to be contacted is moved, actually or relatively, until the contact tip encounters a terminal of the device causing the cantilever arm to be deflected slightly. Due to the spring in the arm, the contact tip presses against the terminal for good electrical contact. During this operation, the contact point "wipes" across the terminal. This wiping method, although simple and reliable, has certain drawbacks. The contact pressure supplied by the cantilever arm needs to be controlled carefully. Too little pressure will result in poor electrical contact; too much pressure can damage a terminal, particularly when the terminal comprises a coating of tin or tin/ lead solder plating. Conventionally, termination damage to the device is defined as any removal of the solder plating, which is typically only 100-200 microinches thick. Such damage can occur when the contact tip is abrasive in which a case, the tip, being relatively stationary, scrapes an undesirable track across the termination increasing the risk of termination damage. Conventionally, separate cantilever arms are used for the terminals of a multi-terminal device. Due to the continuing miniaturization of electronic devices, and due to the packaging of multiple individual devices in a single package or chip array, minimal clearances exist between the terminals of such devices and the transport mechanism or holding fixture used to bring the device in contact with the cantilever arms. (As used herein the term "chip array" refers to an array of electronic devices packaged in a single ceramic, or similar material, chip including capacitor arrays and any other electrical array in a form that allows it to be contacted by this invention.) The result is that cantilever tips can collide with or ride against a holding fixture or transport mechanism. Holding fixtures are typically FR-4 glass epoxy, or similar non-conductive materials, which tend to have a moderate to highly abrasive surface. Since the cantilever tip is relatively stationary, it can become roughened and abraded from such encounters, and thus tend to further damage device terminals. Also, the cantilever tips can become contaminated by, for example, oxidation or adherence of contaminants to the tips, or a combination of both. In such cases, access to the tips for cleaning is difficult and time consuming when there is close proximity between the tips and the devices being measured, the holding fixtures and/or the device transport mechanisms. Too many things must be disassembled to clean or replace the tips. A significant advance over a wiping contactor is a rolling contactor. It eliminates the damage to terminals caused by "wiping." While this is particularly useful for circuit components having just two end terminals, for example single capacitor ceramic chips, heretofore it has not been feasible to use rolling contacts for simultaneously touching the multiple terminal pairs of an array chip. For example, an array of four individual capacitors can now be packaged in a chip the same size (0.120 X 0.60 inch) as a conventional single (1206) chip capacitor. Because of the extremely small distances between the terminals, it has not been possible to use rolling contacts for simultaneously contacting all eight terminals of such a chip array. This invention solves the above-described problems. The multiple rolling contactor of this invention can simultaneously electrically couple a plurality of terminals of a chip array with little or no damage or markings. This invention is a significant advance over the prior art because, among other things, it eliminates the damage due to the "wiping" action of conventional cantilever type contactors and can be used on chip array devices where the terminations are too close for conventional contactors. It is particularly useful in component handlers for the handling ceramic capacitor arrays, but also for handling any other multiple terminal device having a form that allows it to be contacted by this invention. Other advantages and attributes of this invention will be readily discernable upon a reading of the text hereinafter. SUMMARY OF THE INVENTION An object of this invention is to provide a multiple rolling contactor which will not damage the terminations of small electronic devices while making contact therewith. An additional object of this invention is to provide a contactor having a plurality of individual rolling contactors, each having a rolling point of contact. An additional object of this invention is to provide a contactor having a plurality of individual rolling contacts, each mounted on a separate resilient arm. An additional object of this invention is to provide a contactor having a plurality of rolling contactors which are individually biased to apply contacting pressure to respective terminations of an electronic device being tested. An additional object of this invention is to provide a contactor having a plurality of individual rolling contacts configured to allow each termination on a side of a chip array to be simultaneously contacted. A further object of this invention is to provide a multiple rolling contactor which, when used with an opposing multiple rolling contactor, can together simultaneously contact all the terminations of a chip array. These objects, and other objects expressed or implied in this document, are accomplished by a contactor for signal coupling to a plurality of linearly aligned terminals on a device. Preferably the contactor has a corresponding plurality of contact wheels, the wheels being juxtaposed and spaced to register with the terminals, and a plurality of respective axles on which the wheels can turn. The axles are individually and resiliently cantilevered to respective dispositions at which all the wheels are tangentially aligned to simultaneously roll over respectively registered terminals. The contactor also includes signal communication between each wheel and a user, such a device tester. In general, going from an end contact wheel toward a midpoint of the wheels, each wheel is larger in diameter than a preceding wheel to offset said each wheel's axle, from the tangential alignment, beyond the preceding wheel's circumference. In this way the axles can be stacked along a plane without interfering with the turning on the wheels. Preferably the turning axes of all the wheels are parallel to each other and to the tangential alignment of the wheels, and all lie in an imaginary plane which also passes through the tangential alignment. In the preferred embodiment, the contactor includes a plurality of elongated, resilient arms, one for each wheel, each arm having a free end to which a respective axle is connected, and mounting base, to which the opposite, non-free ends of the arms are affixed, for supporting the arms. In the preferred embodiment, there is signal communication between each axle and its respective wheel, between each axle and its respective resilient arm, and between each resilient arm and the user. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a pictorial view of opposing contactors according to this invention in full contact with a chip array. Figure 2 is a enlarged partial pictorial view of the opposing contactors of Figure 1. Figure 3 is a front view of the contactors of Figure 1 with the upper contactor sectioned along the axes of the contact wheels. Figure 4 is a partial pictorial view of the contactors of Figure 1 as viewed from the side and rear of the chip array positioned therebetween. Figure 5 is an exploded view of the upper multiple contactor of Figure 1. DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to Figure 1, a first multiple contactor, generally designated 2, is shown disposed above a second, opposing contactor, generally designated 4. Preferably, the second contactor 4 is a mirror configuration of the first contactor 2. For descriptive reference purposes only, the first contactor is called herein the "upper" contactor, and the second is called the "lower" contactor, but it should be understood that the illustrated orientation and nomenclature of the contactors are arbitrary choices because there are no restrictions on orientation. In operation, a stream of electronic devices, such as a chip array 6, is passed between the rolling contacts, i.e. wheels, of the opposing contactors. The chip array illustrated has four linearly aligned terminals or contact areas on each side. The contactors are shown as they would be positioned for parametric testing of the chip array, and are shown independent of any test fixture on which they would normally be mounted or attached by means of a mounting base, 8 for the upper contactor and 8A for the lower contactor which preferably mirror each other. For clarity of understanding, not shown is a chip carrier used to move chip arrays into position between the opposing contactors for continual, rapid sequential testing of such chip arrays. Referring to Figures 2 and 3 , since the lower contactor 4 is a mirror image of the upper contactor 2 , the following description of assembly and operation will be limited to the upper contactor unless otherwise specifically indicated. The chip array 6 under test has a line of four terminations being touched by individual wheels of the upper contactor: a small left contact wheel 18 is shown contacting a left termination 10; a large left contact wheel 20 is shown contacting a left center termination 12; a large right contact wheel 22 is shown contacting a right center termination 14; and a small right contact wheel 24 is shown contacting a right termination 16 ("small" and "large" referring to the relative diameters of the wheels) . All the wheels are preferably gold plated brass or similar material being highly conductive and resistant to wear. The large wheels have concentric cylindrical hubs projecting outwardly in opposite directions. A left hub 26 extends from the large left wheel 20, and a right hub 28 extends from the large right wheel 22. Each of the contact wheels rotates independently on its own axle: the left small wheel on axle 30, the left large wheel on axle 32, the right large on axle 34 and the right small on axle 36. As illustrated, but not necessarily so, the axles are all about the same length and diameter, and are preferably made of a conductive, copper- graphite material. (As used herein the term "axle" refers to a pin, bar, shaft, or the like, on which or by means of which a wheel rotates.) Inboard ends of the axles are disposed in respective axle holes centrally defined in the small contact wheels and in the hubs of the large contact wheels. The axles communicate signals to and from their respective wheels and, e.g. a test fixture. While the small wheels and the hubs of the large wheels are in frictional contact with their respective axles for constant electrical continuity, the wheels are preferably not affixed to their axles and turn on them. Referring to all the figures, the outboard ends of the wheel axles are supported by either a "left" axle support block 38 or a "right" axle support block 40, the terms "left" and "right" being arbitrarily chosen terms of reference only. The support blocks are generally rectangular in shape, having an axle support shelf 42 projecting from a short side of the block. Axle seats 44 are defined in the shelves. A left axle support block 38 is shown supporting the axle 32 for the large left contact wheel 20. A right axle support block 40 is shown, in mirror image, supporting axle 30 of the left small contact wheel 18. Axles 34 and 36 are shown supported by a right support block 40 and a left support block 38, respectively. The axles are held in their respective axle seats by respective resilient retainer bars 46. The axle retainer bars extend from their support blocks over the axles to confine them to their seats. The retainer bars are disposed in respective retainer bar channels 48 defined in their support blocks. Each retainer bar is secured to its block by a fastener, e.g. a screw, near the bar's end opposite the axle it is retaining. The axle support blocks are preferably made of the same material as the axles, preferably a copper-graphite material providing electrical continuity between the axles and their respective support blocks. The copper-graphite material is also solder compatible, allowing solder to adhere to the support block. The axle retainers are preferably made of blue-tempered spring steel to retain a resilient pressure on the axles to keep them seated. Referring to Figures 1 and 5, each axle support block is attached to a respective cantilever arm, 52 or 54. Two block holes 50 are defined transversely through each axle support block in a line parallel to and offset from its retainer bar channel 48. Each cantilever arm is preferably made of a beryllium-copper material and is connected to its axle support block perpendicular to the axle seat. The cantilever arms are affixed to respective block surfaces opposite of the axle retainer bars by solder applied in the block holes. Each wheel is thus independently supported by a cantilever arm which suspends a respective axle support block, which in turn holds the axle on which the wheel turns. As illustrated, the wheels are tangentially aligned to simultaneously fall over a line of respectively registered terminals. Referring to Figures 1 and 5, the small contact wheels, 18 and 24, have cantilever arms 54 with tabs 56 projecting laterally near the ends of the arms remote from the support blocks. The free ends of all the cantilever arms, are precisely positioned and affixed by a combination of electrically insulating blocks and pins which are attached to mounting blocks 8. An angled insulator block 58 is affixed to each mounting block by connecting pins 60 extending through mounting and locating holes precisely machined or formed in both the angled insulating block and the mounting block. The insulators are a non-conductive, ceramic, or similar material capable of maintaining precise dimensions. The cantilever arms 52 for the large contact wheels are located on the angled insulator block by pins 62 extending from an "upper" face of the angled insulator block, and are clamped thereon by the connector block 64. The connector block fits over the ends of the pins 62 and is affixed to the angled insulator block by fasteners, such as screws. The connector block is also made of an electrically insulating material similar to the angled insulation block. The tabbed cantilever arms 54 which support the small contact wheels are similarly sandwiched and pinned in position between a bottom insulator block 66 and a bottom connector block 68 by pins 62 extending through holes defined in the insulator blocks and the tabbed cantilever arms. Referring again to Figures 1 and 5, the bottom connector block 68 has a raised section which fits into a recessed area in the angled insulator block 58. Spring- loaded contacts 70, "pogo stick" or similar, at the ends of wires 72 (for conducting signals to and from a tester) , fit into through holes, 74A and 74B, defined in the upper connector block 64 and the bottom connector block 68, respectively. The wires going to the bottom connector block pass through an access hole (not shown) defined in the center of the upper connector block. The through holes 74A in the upper connector block are directly over the upper cantilever arms 52, allowing spring-loaded contacts 70 to press against the arms for sending and receiving electronic signals to and from the large contact wheels. The through holes 74B in the bottom connector block are offset laterally from those in the upper connector block so that they are positioned directly over the tabs 56 extending from the lower cantilever arms 54, allowing signal communication between the small contact wheels and the tester. Referring again to Figures 1 and 5, the mounting base 8 has an arm 76 which projects forward from the base parallel to the cantilever arms which terminates in a lateral extension 78 perpendicular to the cantilever arm. The lateral extension has two recessed areas on either side of a pivot pin post 80 projecting upward therefrom. The recessed areas on either side of the pivot pin post are aligned with and accommodate the lower cantilever arms 54 therein. Fulcrum pins 82 are inserted into and frictionally held in holes defined in the pivot pin post perpendicular to the axes of the cantilever arms. The fulcrum pins are a preferably non-conductive ceramic or similar material sufficient to support the upper and lower cantilever arms intermediate the connector blocks and the axle support blocks, 38 and 40. The lower cantilever arms are separated vertically from the upper cantilever arms. The angled insulator block 58 causes the upper cantilever arms to be at an approximately 10° angle with the lower cantilever arms. The tabbed cantilever arms supporting the small contact wheels abut the top of the lower fulcrum pins 82. The upper cantilever arms abut the tops of the upper fulcrum pins. The fulcrum pins bend the cantilever arms slightly upward which makes the large and small contact wheels spring biased toward a device under test. While this description of the biasing of the cantilever arms has been in relation to the upper multiple rolling contactor 2, it also applies to the lower contactor 4. Since the lower contactor 4 is essentially a mirror of the upper, the stress due to the deflection of the arms over fulcrum pins causes the large and small contact wheels to be biased upward. These opposing biases (downward in relation to upper contactor 2 and upward in relation to lower contactor 4) tends to apply opposite but generally equal force to the electronic devices therebetween. This helps insure adequate contact with the terminals of the chip arrays as they pass between the contactors, but also prevents the chips from moving away from either set of wheels. Referring to Figures 3, 4 and 5, comb plates 84 are affixed by fasteners to the respective bottoms of the mounting base extensions 78. The comb plates are located by pins 86 projecting from the bottom of the extensions. The comb plates each have a slot opposite its fastened edge to allow the large and small contact wheels to fit between two normal tines 88 at opposite forward corners of the comb plate. The tines fit just to the outside of the small contact wheels, i.e. 18 and 24, best shown in Figure 4. These tines limit lateral outward movement of the small contact wheels. Referring to Figure 3, because the contact wheels are free to pivot on their respective cantilever arms, and because the wheels can move laterally along their axles, the wheels must be spaced and electrically isolated from each other. Accordingly, a thin plastic circular insulating disk 90 is attached (for example, adhesively) to the inside (opposite the hub) of one or both of the large contact wheels. Annular insulating rings 92 are also attached to the hub sides of the large contact wheels. The insulating disk and annular rings prevent the large contact wheels from touching each other or the small contact wheels along their axles. With two multiple rolling contactors as described herein disposed on either side of an electronic device, such as a ceramic chip array, the multiple terminals of the device can be contacted simultaneously as it passes between the contactors. The foregoing description and drawings were given for illustrative purposes only, it being understood that the invention is not limited to the embodiments disclosed, but is intended to embrace any and all alternatives, equivalents, modifications and rearrangements of elements falling within the scope of the invention as defined by the following claims. For example, there need not be an equal number of opposing rolling contacts. This could be the case of a chip under test which has an unequal number of terminals on opposite sides. Also, there need not be any opposing rollers if a chip has terminals only along one side. Also, contactors could be orthogonal to each other, if for example, a chip has terminals along orthogonal sides. Also, there can be one or more wheels nested between the large wheels, in which case the diameters of the nested wheels would be greater than the large wheels so that the nested wheels' axles would be offset beyond the large wheels, and there would be three or more levels of cantilever arms. I CLAIM:

Claims: CLAIMS 1. A contactor for signal coupling to a plurality of linearly aligned terminals on a device, the contactor comprising: (a) a corresponding plurality of contact wheels, the wheels being juxtaposed and spaced to register with the terminals, (b) a plurality of respective axles on which the wheels can turn, (c) means for individually and resiliently cantilevering the axles to respective dispositions at which all the wheels are tangentially aligned to simultaneously roll over respectively registered terminals, and (d) means for signal communication between each wheel and a user. 2. The contactor according to claim 1 wherein, going from an end wheel toward a midpoint of the wheels, each wheel is larger in diameter than a preceding wheel to offset said each wheel's axle, from the tangential alignment, beyond the preceding wheel's circumference. 3. The contactor according to claim 2 wherein the turning axes of all the wheels are parallel to each other and to the tangential alignment of the wheels. 4. The contactor according to claim 3 wherein the turning axes all lie in an imaginary plane which also passes through the tangential alignment. 5. The contactor according to claim 1 wherein: (a) a first set of wheels and their axles are disposed to have a common turning axis, and (b) a second set of wheels and their axles are disposed to have a common turning axis different from the axis of the first set. 6. The contactor according to claim 5 wherein the turning axes are parallel to each other and to the tangential alignment of the wheels. . The contactor according to claim 6 wherein the turning axes all lie in an imaginary plane which also passes through the tangential alignment. 8. The contactor according to claim 6 wherein the axles of the first set of wheels are offset, from the tangential alignment, beyond the circumferences of the second set of wheels. 9. The contactor according to claim 1 wherein the cantilevering means comprises: (a) a plurality of elongated, resilient arms, one for each wheel, each arm having a free end to which a respective axle is connected, and (b) base means, to which the opposite, non-free ends of the arms are affixed, for supporting the arms. 10. The contactor according to claim 9 wherein the axles all extend outwardly from their respective wheels, and further comprising a plurality of block means, one each affixed to the free end of each resilient arm, for supporting a respective axle. 11. The contactor according to claim 10 wherein each block means comprises: (a) means, defined by said each block means, for seating an end of a respective axle remote from its respective wheel, and (b) means for retaining the respective axle in its seat. 12. The contactor according to claim 1 wherein the means for signal communication comprises: (a) signal communication between each axle and its respective wheel, and (b) means for signal communication between each axle and a user. 13. The contactor according to claim 9 wherein the means for signal communication comprises: (a) signal communication between each axle and its respective wheel, (b) means for signal communication between each axle and its respective resilient arm, (c) means for signal communication between each resilient arm and a user. 14. The contactor according to claim 11 wherein the means for signal communication comprises: (a) signal communication between each axle and its respective wheel, (b) means for signal communication between each axle and its respective means for retaining the axle in its seat, (c) means for signal communication between the means for retaining the axle in its seat and its respective resilient arm, (d) means for signal communication between each resilient arm and a user. 15. The contactor according to claim 2 wherein the cantilevering means comprises: (a) a plurality of elongated, resilient arms, one for each wheel, each arm having a free end to which a respective axle is connected, and (b) base means, to which the opposite, non-free ends of the arms are affixed, for supporting the arms. 16. An apparatus for signal coupling to a device having pluralities of linearly aligned terminals along two edges, the apparatus comprising: (a) a first contactor for coupling to one edge of the device, the first contactor comprising: (1) a plurality of contact wheels corresponding to the terminals of said one edge, the wheels being juxtaposed and spaced to register with the terminals of said one edge, (2) a plurality of respective axles on which the wheels can turn, (3) means for individually and resiliently cantilevering the axles to respective dispositions at which all the wheels are tangentially aligned to simultaneously roll over respectively registered terminals, and (4) means for signal communication between each wheel and a user; and (b) a second contactor for coupling to the other edge, the second contactor comprising: (1) a plurality of contact wheels corresponding to the terminals of said other edge, the wheels being juxtaposed and spaced to register with the terminals of said other edge, (2) a plurality of respective axles on which the wheels can turn, (3) means for individually and resiliently cantilevering the axles to respective dispositions at which all the wheels are tangentially aligned to simultaneously roll over respectively registered terminals, and (4) means for signal communication between each wheel and the user. 17. The contactor according to claim 16 wherein the second contactor is a mirror of the first contactor. 18. The apparatus according to claim 16 wherein for each contactor, going from an end wheel toward a midpoint of the wheels, each wheel is larger in diameter than a preceding wheel to offset said each wheel's axle, from the tangential alignment, beyond the preceding wheel's circumference.

Inventors: GARCIA DOUGLAS J, GARCIA, DOUGLAS, J.
Applicants: ELECTRO SCIENT IND INC, ELECTRO SCIENTIFIC INDUSTRIES, INC.
Application year: 1998
Main classification: H01R39
IPC codes: G01R1, G01R31, H01R39