Method and apparatus for a probe card

An integrated apparatus and method to provide test, diagnostics and characterization access to backplane electrical signals during electronic product development is presented. The apparatus removes need for manual and ad hoc connections made in an engineering laboratory or assembly line which make the process prone to damage of the components, inaccurate measurements and arbitrary fluctuations in function. The method and apparatus is a mechanized way to connect backplane signals to corresponding drivers, receivers and test equipment through probes placed on equidistant electrical traces, reducing inter signal variations.

FIELD OF THE INVENTION

The present invention relates generally to probe cards used in electronics More specifically, the present invention is an electronic and mechanical system which is used in the diagnostics and characterization of printed circuit boards with back planes for board to board interfaces.

BACKGROUND OF THE INVENTION

Electronic systems comprise, among other things, a plurality of printed circuit boards with electronic components. Such components may be application specific integrated circuits (ASICs), field programmable gate arrays (FPGAs), dynamic random access memories (DRAMs), flash memories, central processing units (CPUs), read only memories (ROMs), capacitors, inductors, resistors and wires. With the improvement of semiconductor technology, most of chip to chip and board to board electronic interfacing occurs through the use of a serializer and deserializer (serdes) protocol, over which transaction level communication occurs. When the semiconductor technology was not fully matured, the speeds achievable at these serdes interfaces were limited. Accordingly, pin count optimization was not possible through use of serdes technology as the low speeds limited the bandwidth of communication. Such limitation in bandwidth was compensated through widening of the chip-to-chip and board-to-board interfaces from being a single data bit interface to a byte (8 bits), half word (16 bits), word (32 bits) or double word (64 bits).

Serial interconnects have matured to the point where speed, reliability, and robustness make them a viable option for board-to-board connections. By eliminating need for parallel busses and defining new protocols leveraging serial technologies such as PCI Express, Ethernet, Serial RapidIO, pins can be freed up to support proper number of data and control plane pins without losing board-to-board bandwidth.

The original version of VME created in the 1980 and standardized as IEEE 1014-1987, called for 3U and 6U form factors for the backplanes. The 3U format comprises of a single 96-pin P1 connector to support the popular 16-bit microprocessors and the board size was similar to contemporary standards.

However, over time the 3U VME format lost its place as address and data bus widths increased, calling for more pins on the backplane. As 32-bit processors evolved, the 6U format with both P1 and P2 connectors became the de facto size of choice for VME.

The 3U and 6U form factors are also chosen for VPX, the ANSI/VITA 46 family of specifications. VPX has defined both a 3U and 6U format, allowing designers to choose the best for their application. VPX is an ANSI standard (ANSI/VITA 46.0-2007) that provides VME bus-based systems with support for switched fabrics over a new high speed connector. A 3U front panel is 132 mm long, while a 6U front panel is 265 mm long, and both are 100 mm in width.

New generations of embedded computing systems based on the VPX standard reflect the growing significance of high speed serial switched fabric interconnects such as RapidIO, 10 Gigabit Ethernet, PCI Express, and Infiniband. These technologies are replacing traditional parallel communications bus architectures for local communications, because they offer significantly greater capability. Switched fabrics technology supports multiprocessing systems that require the faster possible communications between processors (e.g., digital signal processing applications). VPX gives the large existing base of VMEbus users access to these switched fabrics. Technologies called for in VPX include 3U and 6U formats and new 7-row high speed connector rated up to 6.25 Gbit/s. In networking applications, these speeds are now approaching 25 Gbit/s.

As a drawback, increase of width of the interfaces has a consequent cost component as the increase in pin count mandated a costlier chip package, larger PCBs, higher power dissipation. With advent of higher integration and improvements in semiconductor technology, the clock speed of a serdes interface, which was limiting, increased exponentially. Where a serdes interface of 550 MHz at one point was a challenge, current serdes technology is now feasible to support upto 25 Gbit/s. With this exponential improvement in speed, the widening of the bus width to meet bandwidth requirements is no longer needed. Semiconductor chips and PCB designers exploited this improvement in technology to design inter-chip and inter-board protocols with serdes interfaces. While enabling more integration and reduction of sizes of the PCBs and semiconductor chips, the high speed interfaces between chips and between boards over backplanes have to be robustly designed for the protocols over them to work correctly.

The serdes interfaces between boards and chips over the backplanes, operating at very high speeds have to be tested for feasibility and reliability of correct bit transfer at desired rates. Tests have to be run and interfaces characterized and measured for best and worst case transition delay, temperature and process variations. Such measurements require a minimum of two and up to supportable slots of PCBs to be populated over a backplane. Then signals over and between any two slots are to be measured and characterized for these parameters. In the current state of technology, such measurements require human intervention, design of daughter cards, soldering and connecting probes and wires on boards under test. At very high speeds, such efforts affect both geometry and physical behavior of the electrical circuit that is subject of test and characterization. Accurate measurements are difficult due to fringe effects, hard to maintain uniformity and variations due to human touch. Due to abrupt and numerous connections and disconnections, a likelihood of damage to the semiconductor component or the PCB is not ruled out. Sometimes this leads to discard of entire PCB due to failure of a single semiconductor component. Losses this way affect the margins and increase the recurring costs in product design.

The present invention overcomes these challenges in backplane design, test and characterization. A probe card is designed, which is connectable in slot increments in one dimension and in pin pitch increment in other dimension on the backplane interconnects of the PCB. Two probe cards, located in different slots of the backplane are required to check the electrical performance of traces routed on the backplane. The probe cards have to be moved and positioned in increments relating to the slot to slot pitch and to the backplane connector's own row to row pitch.

The probe card provides mechanics to be able to engage and disengage the connections, avoiding need of human intervention on the PCBs. The probe card, designed as a semi-circle in one embodiment, provides the probe connects distributed along its circumference for easy connections to probes, drivers and receivers of the serial or parallel connections. In the present invention, test, diagnosis, probing and characterization are enabled while overcoming the shortcomings of the present art. Reliability, cost, time to design and market are all positively impacted.

Conventional probe cards are generally inserted into the backplane without any mechanical features guiding the process. Probe cards equipped with connectors with high insertion forces, like Multi-Gig connectors, are difficult to position and connect/disconnect from the backplane without damaging the connectors or without affecting the accuracy of the backplane performance measurements. The present invention overcomes these shortcomings.

Due to this invention, both testing and qualification of electrical interface is facilitated by providing symmetric, robust and functionally isolated probing points for backplane signals. The method and apparatus is flexible and adaptive to all laboratory test assemblies and equipment. Measurements are accurate and effect of human interventions in making and changing connections in the laboratory are minimized and isolated from probing results. Damages to sensitive electronic parts and components are minimized.

DETAIL DESCRIPTIONS OF THE INVENTION

In the following description specific details are set forth describing certain embodiments. It will be apparent, however, to one skilled in the art that the disclosed embodiments may be practiced without some or these entire specific details. The specific embodiments presented are meant to be illustrative, but not limiting. One skilled in the art may realize other material that, although not specifically described herein, is within the scope and spirit of this disclosure.

In one embodiment of the apparatus, the probe card is attached to a mechanical structure. In one embodiment, this comprises of movable parts which perform the required functions. In an exemplary embodiment, the whole probe card device has to fit within the envelope of one slot. In one test configuration, two probe cards are required to perform the testing. As an exemplary embodiment, the second probe card is attached to a basically mirrored mechanical structure.

In one functional use, as a first step, the probe card positioning device is placed on the slot to be tested by means of engaging the alignment pins on the backplane. In another embodiment, this is done using the backplane mounting holes. Alternatively, this could be achieved by alternate positioning means. In one embodiment, a clamping feature secures the probe card positioning device to the backplane.

As an adaptive feature of the present invention, in one embodiment, one mounting block of the probe card device can be moved to different locations along the bridge beam. In one functional use, it enables support for various backplane configurations. In one embodiment of the device, support is provided for both 6U (comprising of P1 and P2 connectors) and 3U (comprising of P1 connectors only) configurations.

In one embodiment, after positioning the probe card device on the backplane, the probe card connector is inserted into the backplane connector. Probe card connector can be positioned along the bridge beam in predetermined increments. In one exemplary embodiment, one means of positioning the probe card is by a set of holes drilled into the bridge beam. In this embodiment, a pin set in a corresponding hole acts as a stop. In one exemplary embodiment, the probe card is moved to the stop and locked in this position. This is achieved by tightening a thumb screw safety lock. The connector of the probe card is then inserted in the connector of the backplane by lowering the probe card, rotating a handle. Rotating the handle in the opposite direction disengages the probe card from the backplane. A stop keeps the load card in the disengaged position, ready to be repositioned.

FIG. 1100presents a one dimension front view of the probe card apparatus mounted on a 6U backplane112. In one embodiment, a probe card101is designed in a semi-circle shape with a plurality of probe connect points mounted on the circumference for connection to test assembly, driver or receiver of electrical signals. In one embodiment, a “T” Member PCB mount102is placed with a cross slide103. In an exemplary embodiment, the PCB mount102has protruding slots that fit into circumferential holes of a probe card handle104. In other embodiment, the probe card may have other geometries. In one embodiment, using a bridge beam108, cross slide plate103, cross slide106, two support blocks109117, two backplane clamps110116and two thumb screws111115, the probe card is mounted over a backplane112. In one embodiment, the probe card101tapers from the semi-circle portion to a thin attachment at the end of which a probe connector114is installed. An up position lock118is attached to the PCB mount102. In the illustration, the up position lock118is in unlock position, indicating that the probe card101is engaged with the probe connector114in the desired slots of the backplane connector112.

FIG. 2200is an illustrative embodiment of the above embodiment in a top view of the apparatus. The semi-circular probe cards203204appear rectangular with the probe connection points. The bridge beam has a P1 connector section202and a P2 connector segment201. The mounting apparatus is also seen in one dimension from the top.

FIG. 3300is an illustrative embodiment of the above embodiment in a side view of the apparatus. The semi-circular probe cards301302appear rectangular with the probe connection points. The bridge beam and the rest of the mounting apparatus are also seen in one dimension from the side.

FIG. 4400is an isometric exploded view of the device apparatus. A VPX backplane410in 6U format is shown. The mounting apparatus of thumb screws409411, backplane clamps408412and support blocks407414with pins406are used to install a bridge beam415. Using cross slide418and cross slide plate405, T member retainer plates403404, the probe card handle417and the up position lock, and thumb screw safety lock413, the probe card401with a probe connector402is mounted on the bridge beam using screws. The explode view illustrates all of the parts involved as well their location and connecting parts.

FIG. 5500represents an isometric view, illustrating two simultaneous probe cards501518mounted on the two respective bridge beams516. Both probe cards501518are in an engaged position, with the up position lock502in unlock position. The front side of the probe card is shown in the front501, while the back of the same is shown for the other port card518. Both cards are mounted on the bridge beams516using thumb screws,513511support blocks515510, backplane clamps514512and thumb screw safety locks505. The VPX backplane509is in a 6U format. The probe cards501518have their respective mechanical components of a probe card handle503, PCB mount519, stop pin517, cross slide504and cross slide retainers. The isometric view illustrates the apparatus engaged in a 6U backplane format.

FIG. 6600illustrates in one embodiment, the 6U format backplane609with probe card disengaged601. This figure is in a front view. The bridge beam614is mounted over the selected slot of the backplane609using thumb screws607610, backplane clamps606612, thumb screw safety lock611and support blocks605613The probe card handle603is in a downward position, essentially lifting the probe card601through T member PCB mount602and all connecting apparatus. This includes cross slide plate604, cross slide retainers, stop pin615and up position lock617. The probe connector608is seen lifted from the backplane slot609, with probe card handle603in a “down” position. The up position lock617is in lock position to avoid accidental dropping of the connector608onto the backplane609. For a proper connection, the lock617will have to be taken to unlock position, after which the probe card handle603will move anticlockwise to lower the probe connector608.

FIG. 7700illustrates in one embodiment, a similar view as above with the probe card701engaged. The mounted apparatus has moved to the P1 connector side on the backplane709. The thumb screws710707, backplane clamps712706, attach the VPX backplane709to the bridge beam714. The probe card apparatus comprising of probe card701, cross slide716, stop pin716, up position lock717and PCB mount702are then attached to the bridge beam714with mechanism of cross slide plate704and probe card handle703to engage and disengage the probe card701on to the backplane709. In this illustrative embodiment, the probe connector709is engaged on the back plane709. Consequently, the up position lock717is in “unlock” position.

FIG. 8800illustrates in one embodiment, an isometric view as above with the probe card801engaged. The mounted apparatus has moved to the P1 connector side on the backplane810. The thumb screws808811, backplane clamps812807, attach the VPX backplane810to the bridge beam814. The probe card apparatus comprising of probe card801, cross slide716, stop pin816, up position lock817and PCB mount802are then attached to the bridge beam814with mechanism of cross slide plate806and probe card handle803to engage and disengage the probe card801on to the backplane810. In this illustrative embodiment, the probe connector809is engaged on the back plane810. Consequently, the up position lock817is in “unlock” position.

FIG. 9900illustrates in one embodiment, an isometric view as above with the probe card901disengaged. The mounted apparatus has moved to the P1 connector side on the backplane910. The thumb screws908911, backplane clamps912907, attach the VPX backplane910to the bridge beam914. The probe card apparatus comprising of probe card901, cross slide916, stop pin815, up position lock917and PCB mount902are then attached to the bridge beam914with mechanism of cross slide plate906and probe card handle903to engage and disengage the probe card901on to the backplane910. In this illustrative embodiment, the probe connector909is disengaged on the back plane910. Consequently, the up position lock917is in “lock” position.

FIG. 101000illustrates in one embodiment, a single dimension view as above with the probe card1001engaged for a 3U backplane with only a row of P1 connectors. The mounted apparatus has only the P1 connector row on the backplane1012. The thumb screws10111014, backplane clamps10101015, attach the VPX backplane1012to the bridge beam1007. The probe card apparatus comprising of probe card1001, cross slide1003, stop pin1005, up position lock1017and PCB mount1002are then attached to the bridge beam1007with mechanism of cross slide plate1006and probe card handle1004to engage and disengage the probe card1001on to the backplane1012. In this illustrative embodiment, the probe connector1013is engaged on the back plane1012. Consequently, the up position lock1017is in “unlock” position.

FIG. 111000illustrates in one embodiment, a top view as above with the probe card11031104engaged for a 3U backplane with only a row of P1 connectors. The mounted apparatus has only the P1 connector row on the backplane10111102.

FIG. 121200illustrates in one embodiment, a side view as above with the probe card11011102engaged for a 3U backplane with only a row of P1 connectors. The mounted apparatus has only the P1 connector row on the backplane.

FIG. 131300, in one exemplary embodiment illustrates a multi-dimension isometric view of the apparatus of two probe cards engaged over a 3U backplane comprising of only P1 connectors. VPX backplane has two bridge beams1315mounted over it through thumb screw13121309, backplane clamps13131308, and support blocks13141306. Probe connector1311is engaged. On the corresponding bridge beams1315, the two probe cards1301are mounted through PCB mount1317, cross slide1304, stop pin1316, thumb screw safety lock1305, up position lock1302and probe card handle1303.

FIG. 141400, in a zoomed isometric view illustrates the steps involved in operating the mechanics for engaging and disengaging the probe card1401connector over the backplane. Section marked as1402is further zoomed as box1403to illustrate the positioning and use of the stop pin. As a first step, the probe handle is moved so that the PCB is in up position1. It is ensured that the lock lever is in the lock position2. In one embodiment, the safety thumb screw is loosened3. The stop pin is moved to properly indicate which pin positions (movement is per pin pitch) the probe connector will engage on the backplane4. The cross slide is moved towards the stop pin until contact is made5. In one application, the safety thumb screw is tightened6. The lock lever is then swung to unlock position7. The probe handle is then moved to engage probe connector to the VPX backplane8.

It is obvious to those skilled in the art that probe card devices can be designed in various stages of complexity, meaning more or less features can be incorporated.FIG. 15depicts a simpler version of a probe card device1501where the bridge beam1507has a serration1502on the lower side and the cross bar contains a spring loaded pin1503which allows the cross bar to be moved in predetermined increments over the bridge beam1507. The probe card connector1505is engaged with a backplane1506by manually pushing down the probe card device and disengaged by manually lifting the probe card device of the backplane1506. A thumb screw safety lock1504can be loosened or tightened.

FIG. 161600illustrates, in one embodiment, prototype of the present invention, with two actual probe cards engaged over a 6U backplane. The lock lever is in “unlock” position and handle is turned for the engagement.

It is also apparent to those skilled in the art, that is, to those who have knowledge and experience in this area of technology that the description above explains just two of many possible design variations. The examples provided above are exemplary only and are not intended to be limiting. One skilled in the art may readily devise other systems consistent with the disclosed embodiments which are intended to be within the scope of this disclosure. As such, the application is limited only by the following claims.