Patent Application
20160356842
This invention relates generally to contactor systems for testing integrated circuits and, more specifically, to a contactor system for testing Ball Grid Array (BGA) packaged devices under test (DUTs).
A ball grid array (BGA) is a type of surface-mount packaging (a chip carrier) used for integrated circuits. BGA packages are used to permanently mount devices such as processors. A BGA can provide several interconnection pins, or balls, because the whole bottom surface of the device can be used, instead of just the perimeter. The leads are also on average shorter than with a perimeter-only type package leading to better performance at high speeds.
The balls at the bottom of a package for a conventional 0.5 mm BGA packaged DUT can fluctuate in size between 250 and 350 microns, with a 300-micron average size. In order to make reliable contact with the balls of the BGA in a high volume manufacturing environment, the contactor must be able to maintain proper contact despite a total ball height fluctuation of 150 microns. Accordingly, a reliable contactor needs to have 150-micron compliance.
A popular solution to the mechanical compliance problem is using a pogo pin contactor, which utilizes a spring-loaded cylindrical pogo. The pogo pin contactors are typically part of a socket in which the BGA packaged DUT is placed for testing. However, a limitation with pogo pin contactors is that they are typically 3 to 5 mm long, and at higher frequencies e.g., over 40 GHz, the inductance due to the pogo pin length limits high frequency performance. A design technique that is typically used by socket manufacturers (for the BGA packaged DUTs) to alleviate this problem is to suspend each pogo pin in a cylindrical hole in a metal block to create a coaxial transmission line. However, the maximum operating frequency despite using this technique is 40 GHz.
Another class of contactors that is typically used in the industry is conductive elastomer. The typical thickness of 0.14 mm for the elastomer creates minimal parasitic inductance, thereby, making elastomer an effective solution for 77-82 GHz testing. However, the contactor compliance for elastomers is relatively poor compared to pogo pins. For example, the approximate contactor compliance for elasatomer is about 40 microns, which is a small fraction of the required high volume manufacturing target of 150 microns. Additionally, elastomer contactors may not be as durable in a high volume manufacturing environment.
As a result, there is no current solution in the industry that offers both 80 GHz or so electrical performance and 150-micron mechanical compliance. Conductive elastomer contactors might provide electrical performance to 80 GHz, but mechanical compliance is limited to only approximately 40 microns. Pogo pin contactors, on the other hand, provide electrical performance only to 40 GHz, but mechanical compliance is limited to 150 microns.
Accordingly, there is a need for a contactor that has both 80 GHz electrical performance and 150 micron mechanical compliance. A typical application for these contactors, for example, is for use in testing devices to be incorporated into collision avoidance radar systems for automobiles. Many collision avoidance radar systems operate at frequencies of approximately 80 GHz or more because of the improved resolution available at those high frequencies. Accordingly, test systems for ICs to be incorporated into these types of radar systems need to provide a reliable solution for testing the high frequency parts.
A number of different automotive radar-based safety applications make use of frequencies from 76 to 77 GHz, for adaptive cruise control (ACC), blind-spot detection (BSD), emergency braking, forward collision warning (FCW), and rear collision protection (RCP). For example, in a collision warning system, an automotive radar sensor can detect and track objects within the range of the transmitted and returned radar signals, automatically adjusting a vehicle's speed and distance in accordance with the detected targets. Embodiments of the present invention advantageously provide cost-effective and efficient solutions for testing integrated circuits (ICs) to be used in automotive radar systems.
Embodiments of the present invention provide a pogo pin socket that has both 80 GHz millimeter wave test capability along with 150-micron compliance for rugged, reliable performance in a high volume manufacturing environment. Further, embodiments of the present invention provide a pogo pin contactor design that operates at millimeter wave frequencies and maintains a 50 ohm profile along its body.
In one embodiment, an apparatus for testing DUTs is disclosed. The apparatus comprises a socket operable to enable coupling between a Ball Grid Array (BGA) packaged DUT and a Printed Circuit Board (PCB), wherein the socket comprises a plurality of pogo pin connectors. The apparatus also comprises a pogo pin connector operable to couple a ball on the BGA packaged DUT to a trace on the PCB, wherein the pogo pin connector of the socket comprises a first end operable for contact with a ball on the BGA packaged DUT and a second end operable for contact with the PCB, wherein the first end is thicker than a shaft of the pogo pin connector, wherein the PCB comprises at least a ground plane and a signal plane comprising signal traces, and wherein the ground plane is nearer to the second end relative to the signal plane.
In one embodiment, a method of assembling a test system using pogo pin contactors. The method comprises positioning a socket to enable coupling between a Ball Grid Array (BGA) packaged DUT and a Printed Circuit Board (PCB), wherein the socket comprises a plurality of pogo pin connectors. The method further comprises coupling a ball on the BGA packaged DUT to a trace on the PCB using a pogo pin connector of the socket, wherein the pogo pin connector comprises a first end in contact with the ball on the BGA packaged DUT and a second end for contact with the PCB, wherein the first end is thicker than a shaft of the pogo pin connector. Finally, the method comprises contacting the second end of the pogo pin connector to the PCB, wherein a ground plane on the PCB is nearer to the second end relative to a plane with signal traces.
In a different embodiment, an automated testing equipment (ATE) apparatus is disclosed. The apparatus comprises a waveguide operable to communicate signals from a test head of the ATE to a Printed Circuit Board (PCB), wherein the PCB comprises signal traces operable to conduct signals. The apparatus also comprises a socket to enable coupling between a Ball Grid Array (BGA) packaged DUT and the PCB, wherein the socket comprises a plurality of pogo pin connectors and wherein a pogo pin connector is operable to couple a ball on the BGA packaged DUT to a trace on the PCB, wherein the pogo pin connector of the socket comprises a first end in contact with the ball on the BGA packaged DUT and a second end in contact with the PCB, wherein the first end is thicker than a shaft of the pogo pin connector, and wherein the PCB comprises at least a ground plane and a signal plane comprising signal traces, and wherein the ground plane is nearer to the second end relative to the signal plane.
The following detailed description together with the accompanying drawings will provide a better understanding of the nature and advantages of the present invention.
Embodiments of the present invention are illustrated by way of example, and not by way of limitation, in the figures of the accompanying drawings and in which like reference numerals refer to similar elements.
In the figures, elements having the same designation have the same or similar function.
Reference will now be made in detail to the various embodiments of the present disclosure, examples of which are illustrated in the accompanying drawings. While described in conjunction with these embodiments, it will be understood that they are not intended to limit the disclosure to these embodiments. On the contrary, the disclosure is intended to cover alternatives, modifications and equivalents, which may be included within the spirit and scope of the disclosure as defined by the appended claims. Furthermore, in the following detailed description of the present disclosure, numerous specific details are set forth in order to provide a thorough understanding of the present disclosure. However, it will be understood that the present disclosure may be practiced without these specific details. In other instances, well-known methods, procedures, components, and circuits have not been described in detail so as not to unnecessarily obscure aspects of the present disclosure.
For expository purposes, the term “horizontal” as used herein refers to a plane parallel to the plane or surface of an object, regardless of its orientation. The term “vertical” refers to a direction perpendicular to the horizontal as just defined. Terms such as “above,” “below,” “bottom,” “top,” “side,” “higher,” “lower,” “upper,” “over,” and “under” are referred to with respect to the horizontal plane.
Automotive applications are requiring increased use of RF/microwave frequency bands, from low RF signals through millimeter-wave frequencies at 77 GHz in radar applications. As these high-frequency signals become more integral parts of the worldwide driving experience, effective test solutions become more critical for designers developing new automotive RF/microwave circuits, as well as production facilities seeking efficient methods for verifying the performance of these radar circuits. While lower-frequency testers are in abundance, and automotive applications employ a wide range of wireless frequencies, a growing concern in automotive markets is for the accurate and cost-effective testing of 77-GHz automotive radar systems for instance. This interest stems from the fact that historically, test and measurement equipment operating at such high frequencies has neither been commonplace nor cost-effective.
A number of different automotive radar-based safety applications make use of frequencies from 76 to 77 GHz, for adaptive cruise control (ACC), blind-spot detection (BSD), emergency braking, forward collision warning (FCW), and rear collision protection (RCP). For example, in a collision warning system, an automotive radar sensor can detect and track objects within the range of the transmitted and returned radar signals, automatically adjusting a vehicle's speed and distance in accordance with the detected targets. Embodiments of the present invention advantageously provide cost-effective and efficient solutions for testing integrated circuits (ICs) to be used in automotive radar systems.
Accordingly, embodiments of the present invention provide a socket that uses pogo pin contactors, wherein the pogo pin is suspended in a cylindrical hole in a metal block within the socket to create a coaxial transmission line. Further, by optimizing the profile of the pogo pin for 50 ohms along its body, embodiments of the present invention provide a pogo pin contactor design, which can operate 80 GHz millimeter wave frequencies while maintaining 150-micron compliance. Moreover, the metal block of the socket that the pogo pin contactors are passed through provides superior isolation and minimizes cross-talk between the signals.
Both ends of the pogo pins are typically spring-loaded. Because the pins are used to propagate millimeter waves, the diameter of the Signal pins is significantly smaller than 1 mm. The tips of the pogo pins 350 protrude into air above the metal block so that contact can be made with the BGA packaged DUT. The bottom of the pogo pins 355 make contact with the traces on a PCB.
Conventional test sockets have satisfactory compliance but are limited to less than 40 GHz performance.
One reason the pogo pin contactor design in a conventional socket is not able to support higher frequencies is because while the coaxial shaft of the pogo pin contactor may be optimized for a single-ended 50 ohm impedance, the ends of the pogo pins are not similarly optimized for a single-ended 50 ohm impedance at 80 GHz (or a 100-ohm differential impedance). Because the pogo pin ends are not similarly optimized, the short wavelength characteristic of millimeter waves causes reflections and other irregularities as a result of the discontinuities between the pogo pin coaxial shaft and the ends. Consequently, high frequencies over 80 GHz cannot be supported.
Simulation results also show that the ends of the pogo pin contactors in conventional sockets are not optimized to minimize reflections and other irregularities.
Accordingly, embodiments of the present invention address optimizing both the BGA ball interface and the PCB interface of a pogo pin contactor for a single-ended 50 ohm impedance (or a differential 100-ohm impedance). With the wavelengths for millimeter waves, every piece of the pogo pin structure needs to be optimized for 50 ohm impedance, otherwise, it results in undesirable reflections within the structure. Embodiments of the present invention optimize the entire structure of the pogo pin for a 50-ohm impedance including the tips.
In one embodiment of the present invention, the pogo pin end 912 making contact with the BGA interface is also larger than the coaxial shaft of the pogo tip. In other words, the optimized pogo pin has thick ends 912 (relative to the shaft 913), shaped like dumb bells as shown in
Embodiments of the present invention address this discrepancy by configuring the ground plane 1028 to be above the plane with the signal traces 1029. The signal is communicated via the coaxial body of the pogo pin contactor through signal vias 1025 and starts traveling across the PCB when it reaches the signal traces 1026. The ground signals, meanwhile, reach the ground plane 1028 before the signal reaches the signal plane 1029.
By comparison, moving the ground plane to the top, as shown in
At step 1502, a socket is provided to enable coupling between a Ball Grid Array (BGA) packaged DUT and a Printed Circuit Board (PCB), wherein the socket comprises a plurality of pogo pin connectors and wherein the PCB comprises a plurality of layers.
At step 1504, a ball on the BGA is coupled to a trace on the PCB using a pogo pin connector, wherein the pogo pin connector comprises an end in contact with the ball on the BGA and an end in contact with the PCB, wherein the end in contact with the ball on the BGA is thicker than the shaft of the pogo pin connector.
At step 1506, a ground plane is provided on the PCB, wherein the ground plane is nearer to the end of the pogo pin connector in contact with the PCB relative to a plane on the PCB with signal traces.
While the foregoing disclosure sets forth various embodiments using specific block diagrams, flowcharts, and examples, each block diagram component, flowchart step, operation, and/or component described and/or illustrated herein may be implemented, individually and/or collectively, using a wide range of hardware configurations. In addition, any disclosure of components contained within other components should be considered as examples because many other architectures can be implemented to achieve the same functionality.
The process parameters and sequence of steps described and/or illustrated herein are given by way of example only. For example, while the steps illustrated and/or described herein may be shown or discussed in a particular order, these steps do not necessarily need to be performed in the order illustrated or discussed. The various example methods described and/or illustrated herein may also omit one or more of the steps described or illustrated herein or include additional steps in addition to those disclosed.
It should also be understood, of course, that the foregoing relates to exemplary embodiments of the invention and that modifications may be made without departing from the spirit and scope of the invention as set forth in the following claims.
The foregoing description, for purpose of explanation, has been described with reference to specific embodiments. However, the illustrative discussions above are not intended to be exhaustive or to limit the invention to the precise forms disclosed. Many modifications and variations are possible in view of the above teachings. The embodiments were chosen and described in order to best explain the principles of the invention and its practical applications, to thereby enable others skilled in the art to best utilize the invention and various embodiments with various modifications as may be suited to the particular use contemplated.
Embodiments according to the invention are thus described. While the present disclosure has been described in particular embodiments, it should be appreciated that the invention should not be construed as limited by such embodiments, but rather construed according to the below claims.
