Electricity: measuring and testing – Fault detecting in electric circuits and of electric components – Of individual circuit component or element
Utility Patent
1997-06-02
2001-01-02
Karlsen, Ernest (Department: 2858)
Electricity: measuring and testing
Fault detecting in electric circuits and of electric components
Of individual circuit component or element
C324S754090
Utility Patent
active
06169411
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention generally relates to circuit testing devices, and more particularly to an assembly and method for electrically contacting the leads of an integrated circuit package.
An integrated circuit package is typically comprised of integrated circuits packaged inside an insulated housing with a plurality of thin, parallel electrical leads extending outwardly from the housing. The leads of an integrated circuit package may be bent into various configurations including but not limited to a “gull-wing” lead configuration which is known in the art.
Circuit testing devices are used in various testing capacities such as, for example, verifying electrical continuity, measuring voltage output, etc. Such tests are frequently performed on the individual leads of an integrated circuit package by electrically contacting each lead with a test probe.
A typical loaded printed circuit board is usually crowded with various electrical components, including arrays of integrated circuit packages. Due to the close spacing of components on the board or “board density” as well as the small size and pitch or spacing of each integrated circuit package lead, it is often difficult to manipulate each lead with a test probe for testing purposes. Thus, circuit testing devices have been developed which conductively route each integrated circuit package lead to a device, e.g. a pin or the like, which is more easily manipulated by a test probe. In particular, circuit testing devices known as “test clips” typically include a spring-tensioned lead portion which “clips” onto an integrated circuit package to hold the circuit testing device leads firmly against the integrated circuit package leads. A significant amount of lateral force is required to hold a test clip in place against the integrated circuit package leads. For this reason, the center portion or “body” of a test clip must be sufficiently rigid to maintain this lateral force. In addition, there is generally a 1:1 ratio between the circuit testing device leads and the integrated circuit package leads, with the leads of both devices being approximately the same size. Thus, careful alignment of the circuit, testing device leads with the leads of the integrated circuit package is very important. The individual circuit testing device leads in a test clip are usually not insulated from one another, and so even a slight misalignment can result in a shorted electrical connection between the circuit testing device leads. In addition, test clips tend to have a larger overall size or “footprint” than the integrated circuit packages they clip onto. Thus, as the board density increases, so does the possibility that test clips will interfere with adjacent components.
Examples of test clips may be found in the 1993 Pomona Surface Mount & IC Test Accessories catalog, by ITT Pomona Electronics, 1500 E. Ninth St., Pomona, Calif. 91769, which is incorporated herein by reference for all that is contained therein. As shown in the catalog, to select the right test clip, the. following characteristics of the integrated circuit package to be tested must be determined: number of leads; package configuration (number of sides); lead pattern (e.g., 4×4, 7×7, 16×24, etc.); lead spacing; package type (e.g. DIP, PLCC, SOIC, QFP, etc.); standard (EIAJ or JEDEC); footprint; and interface (top side interconnection method). Using a test clip with characteristics that do not exactly match those of the integrated circuit package may result in electrical shorts or opens. Thus, test clips may not be available for certain integrated circuit packages which do not have industry-standard (i.e. EIAJ or JEDEC) characteristics. Furthermore, allowable tolerances in commercial products are sufficiently variable so that differences between manufacturers, or even between different plants of the same manufacturer, may require different test clips for devices with the same part number. For example, the leads of integrated circuit packages may be bent differently, the packages may be manufactured to English or Metric standards, or the housing portions of the packages may vary in size and/or shape. Finding a test clip for a particular integrated circuit package may therefore be difficult or impossible. Likewise, a test clip which matches the characteristics of a particular integrated circuit package may not be usable on another integrated circuit package with slightly different characteristics.
OBJECTS OF THE INVENTION
In accordance with the present invention, it is an object thereof to provide a circuit testing assembly which may be used on a wide variety of integrated circuit packages.
It is also an object of the invention to provide a circuit testing assembly which does not require the application of lateral forces to maintain electrical contact between the circuit testing device leads and the leads of an integrated circuit package.
It is also object of the invention to provide a circuit testing assembly which is relatively laterally compact as compared to spring-tensioned type lead contact assemblies.
It is another object of the invention to provide a circuit testing assembly which minimizes the effect of misalignment between the circuit testing device leads and the integrated circuit package leads.
It is a further object of the invention to provide a circuit testing assembly with individually insulated leads that minimize the problem of electrical shorts or opens among the leads.
It is a still further object of the invention to provide a circuit testing assembly which may be used on integrated circuit packages with the same number of leads and lead spacing regardless of differences in other characteristics.
It is an even further object of the invention to provide a circuit testing assembly which provides a plurality of leads for each integrated circuit package lead, thereby ensuring contact between the leads of both the circuit testing assembly and the integrated circuit package.
These and other objects, features, and advantages of the invention shall be described below in the following Summary of the Invention and Detailed Description of the Invention.
SUMMARY OF THE INVENTION
The present invention may comprise an assembly for testing the leads of an integrated circuit package. The assembly may comprise a testing substrate for use in connection with a test probe, the testing substrate comprising a plurality of conductive portions. The conductive portions may comprise a plurality of elongate conductive pins secured to the testing substrate and extending outwardly therefrom. The assembly may also comprise conductive bridge means for providing electrical contact between the leads of the integrated circuit package and the conductive portions of the testing substrate. The conductive bridge means may comprise at least one compressible bridge member having a plurality of electrically conductive wires embedded therein or secured to the surface of the bridge member, the wires being parallel to one another and spaced apart from one another. The assembly may further comprise locator means for retaining the conductive bridge means therein and maintaining the conductive bridge means in electrical contact with the leads of the integrated circuit package and the conductive portions of the testing substrate. The locator means may comprise mounting means for mounting the assembly to a circuit board. The locator means may also comprise at least one elongate opening therethrough, each opening having a bridge member positioned therein.
The present invention may also comprise a conductive bridge apparatus for providing electrical contact between leads of an integrated circuit package and conductive portions of a testing substrate. The conductive bridge apparatus may comprise an elongate insulating member comprised of compressible material. A plurality of electrically conductive wires may be embedded within the insulating member which are parallel to one another and spaced apart from one another within the insulating member.
The present invention may further com
Agilent Technologies
Karlsen Ernest
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