Electricity: measuring and testing – Testing potential in specific environment – Voltage probe
Reexamination Certificate
2002-04-16
2004-12-14
Karlsen, Ernest (Department: 2829)
Electricity: measuring and testing
Testing potential in specific environment
Voltage probe
C324S149000, C324S754090
Reexamination Certificate
active
06831452
ABSTRACT:
TECHNICAL FIELD
The present invention is generally related to monitoring and testing of integrated circuit devices and, more particularly, is related to systems and methods for wideband single-end probing of variably spaced probe points.
BACKGROUND OF THE INVENTION
Continuing advances in integrated circuit (“IC”) technology are a major cause of the demand for improved systems and methods to monitor and/or test IC devices. For example, chips that are mounted on printed circuit boards (“PCBs”) are being developed with higher component densities and smaller physical dimensions. In turn, the chip packages, i.e. the chip housing and electrical connectors, are being designed in more complex and compact configurations. A ball grid array (“BGA”), a chip package that uses an array of solder balls for the electrical connectors, is a typical example of such complex and compact chip package configurations. Other chip package configurations continue to use pins for electrical connectors, but the pins are smaller and arranged to tighter tolerances, and thus, such configurations are also becoming more complex and compact.
IC devices are also being developed that have increased performance characteristics. For example, as IC technology advances, central processing unit (“CPU”) chips, for example that are utilized in computers, are being developed to have increased processing speeds. Furthermore, communication buses that interconnect internal IC devices within a computer system are being developed to support increased speed and bandwidth performance.
The increased complexity and compactness of chip package configurations and the increased performance characteristics of chips and other IC devices create challenges to effective and efficient monitoring and/or testing of such devices. For example, to monitor and/or test an IC device, electrical signals are typically obtained from the device and input to monitoring and/or testing equipment, such as an oscilloscope or logic analyzer. A probe is typically connected to such monitoring and/or testing equipment and used to obtain the electrical signals by making physical contact with the electrical connectors or other probe points of the IC device, a process typically referred to as “probing.” Thus, in order to facilitate the effective and efficient monitoring and/or testing of IC devices, the probe must have physical and electrical features which overcome the challenges posed by the increased complexity and compactness of the chip package configurations and the increased performance characteristics of the IC devices.
Thus far, various systems and methods have been introduced in an attempt to provide physical and electrical features which overcome the challenges to effective and efficient monitoring and/or testing of IC devices, but shortcomings still persist. For example, active probing systems have been introduced that provide high bandwidth (i.e., high frequency) signal reception and low loading of probe tips (i.e., low current through-flow) by positioning the active electronics circuitry as close as possible to the probe tips. But, this practice results in several disadvantages. First, such active probing systems are typically large and bulky, which makes it difficult or impossible to securely connect the probe tips to the probe points of a PCB mounted IC device (e.g., by soldering) to perform hands-free probing and, further, to place the IC device in operation (e.g., by placing the PCB in an enclosure or card-cage) with the probe tips connected to the probe points to perform “in-situ” (i.e., in actual operation) probing. Second, the cable that connects such active probing systems to monitoring and/or testing equipment is usually bulky and inflexible since it contains power conductors (for power supply to the active electronics circuitry) as well as one or more coaxial cables (for signal transmission), and these undesirable features of the connection cable also makes it difficult to maintain the active probing system in position for probing an IC device. Third, such active probing systems are limited in their probing applications because the probe tips have a fixed relative physical positioning and the electrical characteristics of the probe tips (e.g., the damping resistance) are fixed relative to the probing system and cannot be varied. Finally, the cost of such active probing systems is typically too high to justify soldering probing attachments to them without concern for permanently damaging the probing systems.
As another example, differential probes (i.e., probes used for measuring the difference between two signals) have been introduced to provide high frequency differential probing of IC devices. Such differential probes have a fixed spacing between the probe tips which limits the configuration of IC device probe points which can be physically contacted for probing. In an attempt to overcome this shortcoming, “bent-wire” probe tip attachments have been introduced which can replace or modify the fixed-spacing probe tips. These bent-wire probe tip attachments can be attached to existing differential probes and bent to vary the spacing between the attached probe tips in order to contact the intended probe points of an IC device. But, the bent-wire probe tip attachments add undesirable parasitic impedance to the probe tip circuit which reduces the bandwidth (i.e., the high frequency signal reception capability) of the differential probe and, thereby, reduces the capability of the differential probe to accurately obtain signals from high frequency IC devices. Additionally, the positioning of the probe tips of the bent-wire probe tip attachments may undesirably vary during probing of an IC device and thereby result in loss of intended contact with the probe points as well unintended contact with other probe points and/or damaging short-circuit conditions.
As yet another example, wideband (i.e., high bandwidth) probes have been introduced to measure voltage signals of IC devices. Such wideband probes typically must contact a probe signal point and a ground probe point of an IC device with a probe tip and a ground contact, respectively, to obtain voltage signals. A fixed position “spring wire” (e.g., an offset bent wire) or “pogo pin” (i.e., a telescopically retracting pin) is typically utilized as a ground contact for these wideband probes. Since the distance between a signal probe point and a ground probe point varies among IC devices, the ground contacts of existing wideband probes are typically bent to allow the probe tips to contact the probe points. There are several disadvantages to utilizing a spring wire as the ground contact in existing wideband probes. First, the length of a practical spring wire is relatively long and, thus, adds undesirable parasitic impedance to the probe circuit, thereby reducing the bandwidth capability of the probe. Second, the positioning of the spring wire ground contact may undesirably vary (or “skate”) during probing of an IC device and thereby result in loss of intended contact with the ground probe point as well as cause unintended contact with other probe points and/or damaging short-circuit conditions. Third, the spacing set between the probe tip and the ground contact by bending the spring wire may vary, even during routine handling of the probe, thus, making the positioning accuracy unreliable for repeated probing without repeated bending adjustments. Similarly, in utilizing a pogo pin as the ground contact in existing wideband probes, the typical practice of bending the pogo pin to facilitate contact with a ground probe point may result in skating, particularly since the bend in the rigid pogo pin typically must be maintained by force applied against the probe points during probing. Because of its rigidity, the pogo pin also does not accurately maintain the adjusted position during repeated probing.
Based on the foregoing, it should be appreciated that there is a need for improved systems and methods which address the aforementioned, as well as other, shortcomings of existing systems and methods.
SUMMA
Agilent Technologie,s Inc.
Karlsen Ernest
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