Electricity: measuring and testing – Measuring – testing – or sensing electricity – per se – With probe – prod or terminals
Reexamination Certificate
1998-08-28
2001-06-26
Brown, Glenn W. (Department: 2858)
Electricity: measuring and testing
Measuring, testing, or sensing electricity, per se
With probe, prod or terminals
C324S072500
Reexamination Certificate
active
06252391
ABSTRACT:
BACKGROUND OF THE INVENTION
The present inventions relates to probes. More specifically, the present invention relates to high frequency electronic probes which are particularly well suited for nondestructive probing of devices having a high density I/O interface or connector.
In the testing of large systems during the initial bring up and including debugging of system hardware, special modifications are typically made to the product. A metal stiffener used to support the large system boards is machined so that an open access is provided to e.g., pins of a Multi Chip Module (MCM) as well as providing access to other points of interest. There are presently two methods used to measure system operations; destructive and nondestructive measurement techniques. These are accomplished either by direct soldering of probe connectors to the system board or by the use of an insulated template and probe arrangement. The first method, direct soldering, provides good high frequency measurements but has many limitations and disadvantages. These limitations and disadvantages include, for example, the requirement that the board must be removed from the test fixture each time a connection is to be soldered on, the number of connections present at any time is limited and the connections are susceptible to mechanical failure (e.g., such as being broken off). The second method, utilizing the probe template, offers a full range of interconnections, by means of holes drilled through a template made of an insulating material, at all signal locations as well as selected ground or voltage reference locations of the MCM. This arrangement is limited to measurements in the 500 MHZ bandwidth region. Thus, while this template arrangement is adequate for error injection and some mid-frequency a.c. measurements, it is not suitable for analysis of high frequency switching noise and circuit operation verification.
With the ever increasing of operational speeds of computer systems including mainframes, it becomes more and more difficult to provide accurate measurement of high frequency operational parameters such as switching noise, signal integrity, jitter measurements, measurements of differential signals, or of differential measurements of voltage to ground disturbances.
SUMMARY OF THE INVENTION
The above-discussed and other drawbacks and deficiencies of the prior art are overcome or alleviated by the high frequency electronic probe of the present invention. The high frequency electronic probe of the present invention is particularly well suited for use with a high density I/O interface such as a template to aid in probing the pin interface of a Multi Chip Module (MCM) on a system board. A system board has a metal stiffener (or other such structure) mounted thereon with an opening in the stiffener to provide access to an area of interest on the system board (e.g., the pins of the MCM). A probe test assembly (template) is positioned at the opening and secured to the stiffener when testing (probing) is desired to provide access to the pins of the MCM. A cover is positioned at the opening and secured to the stiffener at all other times.
The probe test assembly in one embodiment (high frequency testing applications) comprises an insulated pattern guide plate (or template) and a metal (conductive) probe plate which are positioned at the opening and secured to the stiffener by an insulated frame. The insulated frame protects ground pins in the probe plate from being exposed. The plates have a pattern or array of holes corresponding to the pattern of pins on the MCM. The insulated pattern plate insulates the metal probe plate from a probe. In high frequency applications the metal probe plate is part of the measurement system. The metal probe plate has resilient ground terminals (pins) pressed into selected holes therein which provide a low impedance ground return path for test measurements. For low bandwidth or d.c. testing applications the pattern plate is eliminated and the probe plate is comprised of an insulation material, whereby the probe plate does not form part of the aforementioned ground return path. Since the probe plate in this alternate embodiment is non-conductive a ground pin is not provided.
The probe in accordance with one embodiment of the present invention comprises a single ended, high frequency, resilient probe, i.e., a probe having measurement capability in the 3-9 Ghz range, which is particularly well suited for nondestructive probing of devices having a high density I/O interface or connector (such as the probe test assembly). More specifically, the probe comprises a probe body (unit) having a coaxial resilient double ended probe element attached thereto by an adaptor. A locking pin is attached to the probe adaptor and extends parallel to the probe element, however, it is slightly shorter as the locking pin should not contact any pins of the MCM when the probe is used. The locking pin serves to hold the probe on the probe test assembly. A hook is preferably provided at the distal end of the locking pin. Upon insertion of the probe element into a hole of the pattern and probe plates the locking pin will be inserted into an adjacent such hole and the hook will engage a surface of the probe plate, thereby locking the probe. The probe is unlocked by rotating the probe thereby causing the hook to release from the surface of the probe plate. For low frequency probing applications (including d.c.), two such probes are required, a signal probe and a ground probe which are connected to provide a return ground path.
In accordance with another embodiment of the present invention, a differential probe is utilized when measurement of two points that are close together, as well as being at a variable pitch from each other, is desired, at the same time. The differential probe is also well suited for high frequency (e.g., 3-9 Ghz range) nondestructive probing of devices having a high density I/O interface or connector (such as the probe test assembly). More specifically, the differential probe comprises a base having a first pair of opposing spring steel plates and a second adjacent pair of opposing spring steel plates connected thereto. The first pair of spring plates are also connected to a first probe adaptor and the second pair of spring plates are also connected to a second probe adaptor. A first probe body is mounted at an angle to the first adaptor and a second probe body is mounted at an angle to the second adaptor. A first coaxial resilient double ended probe element connected to the first probe body by the first adaptor and a second coaxial resilient double ended probe element connected to the second probe body by the second adaptor. The use of distinct first and second adaptors and corresponding spring plate pairs provides for lateral and independent movement of each of the first and second probe elements. This embodiment of the present invention provides a unique variable pitch differential measurement system, which can be used for differential measurements or to permit two single ended probes of similar or different types to be close to each other.
The above-discussed and other features and advantages of the present invention will be appreciated and understood by those skilled in the art from the following detailed description and drawings.
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patent: 5717328 (
Kempter Klaus K.
McAllister Michael F.
Pells Charles F.
Richter Stephan R.
Ruehle Gerhard
Brown Glenn W.
Cantor & Colburn LLP
Gonzalez Floyd
International Business Machines - Corporation
Nguyen Vincent Q
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