Electrical connectors – Preformed panel circuit arrangement – e.g. – pcb – icm – dip,... – With provision to conduct electricity from panel circuit to...
Reexamination Certificate
2000-04-10
2001-08-07
Sircus, Brian (Department: 2839)
Electrical connectors
Preformed panel circuit arrangement, e.g., pcb, icm, dip,...
With provision to conduct electricity from panel circuit to...
Reexamination Certificate
active
06270357
ABSTRACT:
This invention relates to burn-in and test of high frequency devices in small electronic device packages. More particularly, it relates to methods and apparatus for mounting and holding electronic device packages during burn-in and test and to establishing and maintaining positive electrical contact to closely spaced input/output terminal lands or leads on such packages without damaging the electronic device, the device package, its interconnection terminals or the test socket and without introducing unnecessary signal distortion.
Advances in microelectronics technology tend to develop electronic device chips and packages which occupy less space while performing more functions. As a result, the number of electrical interconnections between the device package and external circuitry required for the circuits in the chips to communicate with the outside world increases and the physical size of each such interconnection must decrease. In order to provide electrical communication between the chip and external circuitry, circuit chips are usually contained within a housing or package which supports interconnection pads or lands, leads, balls, etc., on one or more of its external surfaces. In order to reduce overall lead length from chip to external circuitry and to provide adequate spacing between input/output terminals on the package, high pin count devices are sometimes mounted in packages in which the input/output terminals are in the form of conductive lands or pads formed on one or more faces of the package. The lands are often arranged in rows parallel with and adjacent peripheral edges of one face with the surfaces of the lands coplanar and parallel with (but slightly below) the bottom surface of the package. The lands may be arranged in other patterns such as parallel rows which cover the entire bottom surface in a grid pattern; lands grouped near the center of the bottom surface; or various combinations of such arrangements. Such device packages (commonly known as land grid array or LGA packages) may thus be mounted on circuit patterns on the surface of a circuit board or the like so that the terminal lands are bonded to mating lands or pads on the board.
In some device packages terminal balls may be formed on or substituted for the land. Terminal balls are usually a quantity of solder which has been heated so that it forms a liquid sphere by surface tension and thus forms a ball-like protrusion extending from the face of the device package. Such device packages (commonly known as ball grid array or BGA packages) may likewise be mounted to circuit patterns on the surface of a circuit board or the like by bonding the solder balls to mating lands or pads on the board.
In many cases it is desirable that the completed device package be subjected to test and/or burn-in prior to acceptance and assembly onto a circuit board. While the terminals (whether lands or balls) may be directly and permanently surface mounted on a circuit board by soldering, it is much more difficult to establish and maintain temporary electrical contact with each land or ball without destroying or damaging the land or ball, the package or the encapsulated device chip. In order to reliably test and burn-in such packages, the package must be temporarily mounted in a re-useable socket or mounting which makes precision interconnection between the input/output terminals and outside circuitry without introducing signal distortion problems and without physically damaging the device package.
As the size of the package decreases and the number of terminals increases, the size and spacing of terminals become smaller. Smaller and more closely spaced lands are, of course, more difficult to contact with test probes or the like. Furthermore, long or massive contact pins cannot be used for connecting external circuitry to the input/output terminals for testing when high frequency devices are involved because such contact pins, particularly when closely spaced in order to contact closely spaced terminals, introduce unacceptable signal distortion.
Conventional burn-in and test apparatus employs test sockets mounted on a burn-in board with the pin-out leads of the test or burn-in socket passing through the bottom of the socket and through holes in a circuit board in conventional through-hole mountings. Interconnection of high frequency devices with outside circuitry using such conventional mounting can induce unacceptable signal distortion because of the high density of parallel terminal connections passing through the board. Surface mounting of test and burn-in sockets can minimize signal distortion resulting from cross-talk, reactive capacitance, etc., by spreading the interconnection circuitry across the surface of the board and reducing parallel lead lengths.
Miniaturized device packages have now been devised which have very closely-spaced input/output terminal lands on one face of the package. Such device packages, because of their extremely small size, configuration and physical construction, are most difficult to handle without causing damage, yet good electrical contact with all the input/output terminals is essential. With such small packages and such finely-spaced terminals, it is not practical to probe each terminal with an individual wire-like probe. Such probes tend to bend (and thus become mis-aligned); overlap two or more terminals; exert sufficient pressure on the terminal to break or otherwise damage it; or tend to distort and/or bond with the terminal. It is therefore desirable that apparatus be devised in which such small packages may be easily temporarily mounted (preferably by automation) and tested and/or stress-tested by burn-in and the like without damaging the device package or introducing signal distortion problems.
In accordance with the present invention reliable precise electrical contact is provided between input/output lands on small LGA packages (or balls on BGA packages) and external circuitry by mounting apparatus which employs a guide plate and contact pins which extend through guides in the guide plate to contact the input/output terminals on the device package and input/output lands connected with external circuitry. The guide plate is formed of electrically insulating material and has a first set of parallel guides (such as parallel holes or channels) arranged to correspond with the terminal arrangement of the device package. The guide plate may be supported on a support base and either the guide plate or the support base has a second set of parallel guides arranged to correspond with input/output lands connected with external circuit media such as a circuit board, burn-in board or the like. A contact pin having first and second substantially parallel end portions joined by a shank in the form of a support beam is positioned so that the support beam extends from a guide in the first group of parallel guides to a guide in the second group of parallel guides and one end portion of the contact pin extends through a guide in the first group of parallel guides to contact an input/output terminal on a device package supported on or adjacent the guide plate surface. The other end portion of the contact pin extends through the second guide to contact an input/output land on the external circuitry board. The support beam is supported in or on the base support (or the guide plate) and the end portions of the contact pin constrained by the guides so that the ends of the contact pins are precisely aligned with and form electrical contact with the input/output terminals on the device package. The ends of the contact pins are constrained to move only axially by the parallel guides, thus extremely small diameter contact pins can be positioned very close together and form reliable individual contact with very small and closely spaced terminals. Since the contact pins are very small and relatively short, they have very little mass. Capacitance-induced, inductance-induced and impedance-induced signal distortion are thus minimized. With the support beam portion of the contact pin between the two end port
Griggs Dennis T.
Sircus Brian
Webb Brian S.
LandOfFree
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