Modular interface between test and application equipment

Abstract: Disclosed is an interface (300) for providing an electrical contact between a test equipment (25, 30) and an application equipment (10, 20). The interface (300) is adapted for receiving a plurality of individual segments (320i), whereby at least one of the segments (320i) comprises at least one electrical path (120, 130) for providing the electrical contact. At least one of the segments (320i) might be electrically isolated with respect to the interface (300) and/or other segments (320i), and can have a ground condition substantially independent of the ground condition of the interface (300) and/or other segments (320i).

Description: BACKGROUND OF THE INVENTION The present invention relates to interfaces between test and application equipments. Testers such IC testers are provided for generating dedicated analog and/or digital signals to a device under test (DUT) and analyzing the response thereof. Such testers are described in detail e.g. in US-A-5,629,631 or in the co-pending European Patent application No. 99105625.0 by the same applicant, EP-A-88299, US-A-5,499,248, or US-A-5,453,995. The document WO-A-99 45400 describes a tester with an interface having modular and exchangeable segments for providing electric signal paths. This document belongs to the state of the art within the terms of Article 54(3) EPC. In most cases, the provision of signals from the tester to a specific application site of the DUT has to be matched with the specific mechanical and electrical properties of the tester as well as of an application equipment handling the DUT. Fig. 1 shows an example of a typical DUT application equipment such as a wafer prober 10 for transporting and positioning highly sensitive silicon wafers as DUTs. The wafers (not visible inside the wafer prober 10) are internally connected to a probe card 20 as interface of the wafer prober 10 towards a tester 25 (in Fig. 1 only symbolized as a general block). Wafer probers are generally applied for testing integrated circuit in the earliest possible production phase. The probe card 20 is typically a device-specific printed circuit board (PCB), e.g. with high-density contact needles on the wafer side and gold-plated contact pads on the tester side (as the side visible in Fig. 1). The probe card 20 normally straddles the dense (needle) pattern form the wafer side to a wider pad pattern for contacting with the tester 25. The size of the probe card 20 is generally limited by the hardware of the wafer prober 10. The wafer prober 10 has to ensure a reliable electrical contact between the contact pads of the wafer and the probe card 20. A DUT board 30 represents the electrical and mechanical interface of the tester 25 towards the DUT. The DUT board 30 normally is a device specific printed circuit board (PCB) custom-built for the specific requirements of the DUT application equipment and can be exchanged dependent on the respective application. More details about the DUT boards 30 are described in particular in the aforementioned co-pending European Patent Application No. 99105625.0. In case that the DUT board 30 is provided as a custom-built exchangeable part, the DUT board 30 is often contacted within the tester 25 by means of spring-loaded contact pins (also called "Pogo™"). While the DUT board 30 and the probe card 20 are electrically optimized (e.g. with respect to signal speed, signal purity, impedance, and transmission rate) regarding either the tester 25 or the DUT of the wafer prober 10, a good electrical and mechanical matching between the DUT board 30 and the probe card 20 has to be achieved. This becomes in particular important with increasing signal transmission rates going up to two Gigabit per second. In the example of Fig. 1, an interface tower 50 (also called "Pogo™ tower") is used as interface between the DUT board 30 and the probe card 20. The interface tower 50 converts the pin pattern (normally rectangular arrangement) of the DUT board 30 of the tester 25 to the pattern (normally round and more dense) of the probe card 20. In the example of Fig. 1, the interface tower 50 further has to bring signals from the tester 25 through a round-shaped hole in a head plate 60 of the wafer prober 10 and bridge the spatial distance between the DUT board 30 and the probe card 20. All the interfacing provided by the interface tower 50 has to be done with a minimum loss in performance for the entire test system provided by the tester 25 and the application equipment of the wafer prober 10. That means that all parts in the electrical path of the interface tower 50 have to maintain a controlled impedance (normally 50 Ω) and a high contact quality for each provided tester channel (e.g. more than 1000 channels). Fig. 2A shows in cross sectional view an embodiment of the interface tower 50 (product number E7017AA) as used for the Hewlett-Packard HP 83000. The interface tower 50 is of cylindrical shape with a central aperture 100. A solid aluminum core 110 bears the electrical and mechanical contacts. The core 110 comprises a plurality of signal paths 120 and ground contacts 130. In the representation of Fig. 2A, the top side of the tower interface 50 is to be directed towards the DUT board 30, while the lower side of the interface tower 50 is to be directed to and to be contact with the probe card 20. Fig. 2B shows in greater detail the electrical paths of the interface tower 50 as depicted on the left side of Fig. 2A. Each signal path 120 is provided by a double-sided spring-loaded contact (Pogo™) isolated by air within holes 140 drilled through the core 110. Ground connection is performed by the ground contacts 130 provided by single-sided ground Pogos, which are arranged around the signal paths 120 and contacted directly with the aluminum core 110. This arrangement of the ground contacts 130 together with the air-isolated holes 140 generates a 50 Ω environment, when a defined relation between the diameters of the electrical contacts of the signal paths 120 and the holes 140 is selected. Thus, the core 110 of the interface tower 50 provides a solid ground for all tester signals transmitted via the signal paths 120 and has to be isolated from a mechanical ground to avoid ground loops in the interface tower 50. The tower interface 50, as shown in Fig. 2A, provides an excellent transmission of electrical signals between the DUT board 30 and the probe card 20. The electrical configuration of the signal paths 120 and the ground contacts 130 ensures an almost loss-free signal transmission, even for very high transmission rates with bandwidths in the range of up to 7 GHz. The provision of the holes 140 with a defined diameter over the entire length of the holes 140, however, encounters severe mechanical difficulties. In case of the above described interface tower 50 with the product number E7017AA, holes 140 have to be provided with a diameter of 3 mm over a length of 50 mm. It is clear for the skilled person in the art that the provision of such holes is extremely difficult and costly and renders the interface tower 50 to be relatively costly. In this context, it has to be understood that each interface tower 50 normally is a specific custom-built part and usually only covers one specific pin-count (e.g. the number of individual electrical paths to be provided) for one specific tester arrangement. While, on one hand, the price of each interface tower 50 is relatively high (e.g. in the range of $ 30.000), a failure or breakdown of the interface tower 50, on the other hand, can lead to significant costs until the testing procedure can be resumed. Thus, it will be required to keep relatively costly spare interface towers 50 in stock to reduce possible test stoppage times. SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a lower cost interface between test and application equipment. The object is solved by the independent claims. Preferred embodiments are shown by the dependent claims. According to the invention, an interface between test and application equipment (also referred to as tester/application interface or TA-interface) is provided with individual modular and exchangeable segments. Each segment can comprise one or more electrical signal and/or ground paths or simply be a dummy segment in order to fill unused segment space within the TA-interface. The modular arrangement of the segments allows to significantly reduce the testing costs, since the TA-interface, on one hand, can easily be adapted to a specific pin-count in a respective application. On the other hand, broken or malfunctioning segments can easily be exchanged without requiring to exchange the entire TA-interface. The TA-interface can thus be configured in accordance with the actual requirements and might also be upgraded on demand, thus allowing to distribute or shift costs until the actual moment of requirement. Furthermore, the modular segment configuration allows to limit stock costs from entire TA-interfaces to only less costly segments, in order to limit unavoidable stoppage time of the testing procedure. In a preferred embodiment, all segments are substantially equal. In another embodiment, the TA-interface only comprises one or more different types of segments, whereby the segments of each type are equal. This further allows reducing costs due to an increased standardization and exchangeability within the segments of the same type. In a further embodiment, one or more of the segments are electrically insulated or isolated, so that each of those one or more segments can be provided to be electrically independent with individual electrical characteristics, such as an individual ground condition. This is in particular useful for testing DUTs with mixed analog and digital functionality. In one embodiment, the ground condition of one or more of the electrically independent segments can be configured independently. The invention thus provides a modular product structure allowing customer-specific configurations with lower price for lower pin-counts and rendering onsite repair/exchange of segments (e.g. by the customer) possible. The invention further allows to provide segments with separated ground conditions, thus significantly increasing the flexibility of the entire test system and enabling testing of applications with mixed functionality (e.g. digital and analog). In most cases, the TA-interface according to the invention is fully compatible with TA-interfaces already commercially available, such as within the Hewlett-Packard HP 83000 system. In general, the TA-interface is applied for providing an electromagnetic link between test and application equipment. In most cases, however, the electromagnetic link is made by electrical contacts, an optical contact, or a combination of both. The test equipment preferably is an integrated circuit tester, and, accordingly, the application equipment preferably is an integrated circuit handling equipment. BRIEF DESCRIPTION OF THE DRAWINGS Other objects and many of the attendant advantages of the present invention will be readily appreciated and become better understood by reference to the following detailed description when considering in connection with the accompanied drawings. Features that are substantially or functionally equal or similar will be referred to with the same reference sign(s). Fig. 1 shows an example of a typical DUT application equipment, Figs. 2A and 2B show an embodiment of the interface tower 50, and Fig. 3 shows an embodiment of an interface tower 300 according to the invention. DETAILED DESCRIPTION OF THE INVENTION Fig. 3 shows an embodiment of an interface tower 300 as an example of a TA-interface according to the invention. The interface tower 300 is depicted in Fig. 3 in the same way as the interface tower 50 in Fig. 1, so that the shown upper side of the interface tower 300 is intended to be contacted with the DUT board 30, while the lower side is intended to be contacted with the probe card 20. The interface tower 300 according to the invention can be provided fully compatible with the interface tower 50 as shown in Fig. 1, so that the interface tower 300 can be applied in the same way as shown by and described for Fig. 1. The interface tower 300 comprises a frame 305 with a plurality of recesses 310i (with i = A, B, C, ...), each one adapted to receive a respective segment 320i (with i = A, B, C, ...). In the embodiment of Fig. 3, the interface tower 300 comprises eight recesses 310A...310H, each filled with a respective segment 320A...320H. In the explosive view of Fig. 3, the segments 320A and 320D are represented spaced off from the interface tower 300. As further apparent from Fig. 3, segments 320A, 320B, 320E and 320F are embodied as blank or dummy segments bearing no electrical contacts, while segments 320C, 320D, 320G and 320H are embodied as segments with a plurality of electrical contacts for establishing an electrical contact between respective contacts of the DUT board 30 and the probe card 20. Each segment 320i can be fixed to the frame 305 of the interface tower 300 e.g. by means of screws 330. For that purpose, each segment 320i is provided on its upper side with a flange 340i laterally extending over a body 350i to be inserted into the respective recess 310i. Each flange 340i comprises grooves 360. For fixing the segment 320i to the frame 305, the screws 330 are inserted into the grooves 360 and screwed to the frame 305. On its upper side, the interface tower 300 further comprises rods 370 for adjusting and fixing the interface tower 300 to the DUT-boards 30 (cf. Fig. 1). The arrangement of the signal paths 120 and the ground contacts 130 in the segments 320i is preferably provided in the same way as depicted in Fig. 2B. Each ground contact 120 is contacted directly with the solid core of the body 350i. Preferably, the body 350i, at least for the segments 320i with electrical contacts 120 and 130, is provided by a solid aluminum core. In a preferred embodiment, each segment 320i is electrically insulated against the frame 305 and/or other segments 320i. For that purpose, an insulating layer 400 (preferably an epoxy layer) is arranged between the flanges 340i of the segments 320i and the upper side of the frame 305. Between side walls 410i around each segment 320i and inner walls 420i of each recess 310i, an insulation might be provided e.g. by a coating over the outside walls 410i and/or the outside walls 420i of the frame 305. Alternatively or in addition thereto, an air gap (e.g. 0.5 mm) might be provided between the outside walls 410i and 420i of the segments 320i and the recesses 310i. Further insulation might be provided with respect of the mechanical fixing of the segments 320i to the frame 305. Preferably the head of the screws 330 will only come in contact with an insulating layer 500i (preferably an epoxy layer) provided on the top side of each segment 320i (cf. in particular Fig. 2B), while the bodies of the screws 330 are spaced apart from the flange 340i, so that no electrical contact will be provided by the screws 330 between the segments 320i and the frame 305. In the embodiment of Fig. 3, all segments 320i preferably have the same mechanical dimensions, but are capable to take over different tasks. This allows configuring the interface tower 300 in accordance with the special applications. The interface tower 300 can e.g. be split into analog and digital areas comprised of one or more of the segments 320i, whereby each area can have its own electrical ground condition. The segments 320i can be designed for different pin-counts and different performance requirements. Thus, the user of the test system will be able to upgrade the interface tower 300 when the pin count of the test system increases or if higher performance is required. Mechanical and electrical contact between the interface tower 300 and the DUT board 30 as well as between the interface tower 300 and the probe card 20 is generally provided by mechanically pressing the components against each other. Contact might be provided manually e.g. using locking means such as screws, semi-automatically e.g. using bayonet slide locks or lever systems, or automatically e.g. using automatic loading mechanisms of the prober 10 and/or the tester 25.

Claims: An individual, modular and exchangeable segment (320i) comprising: a solid core (110) bearing a plurality of electromagnetic signal paths (120) and at least one ground contact (130) for providing an electromagnetic link between a test equipment (25, 30) and an application equipment (10, 20), whereby the solid core (110) is electrically connected to the at least one ground contact (130), and the plurality of electromagnetic signal paths (120) is electrically isolated from the core (110), so that the solid core (110) provides a solid ground for each of the electromagnetic signal paths (120), and means (360) adapted for fixing the segment (320i) to an interface (300). The segment (320i) of claim 1, further comprising segment insulation means (500i) for electrically insulating the segment (320i) with respect to the interface (300) and/or other segments (320i). The segment (320i) according to any one of the claims 1 or 2, wherein the electromagnetic signal paths (120) are provided within openings (140) through the core (110) electrically isolated from the core (110). The segment (320i) according to any one of the claims 1-3, wherein a plurality of the ground contacts (130) are arranged substantially around each electromagnetic signal path (120). The segment (320i) according to any one of the above claims 1-4, wherein the electromagnetic link is made by electrical and/or optical contacts, and the electromagnetic signal paths (120, 130) are electrical and/or optical paths (120, 130). An interface (300) for providing an electromagnetic link between a test equipment (25, 30) and an application equipment (10, 20), characterized in that the interface (300) provides receiving means (305, 310i) adapted for receiving a plurality of individual, modular and exchangeable segments (320i) according to any one of the claims 1-5, the interface (300) further comprising ground condition means for providing at least one of the segments (320i) with an electrical ground condition substantially independent of an electrical ground condition of the interface (300) and/or other segments (320i). The interface (300) of claim 6, wherein the receiving means (305, 310i) comprises insulation means for electrically isolating at least one of the segments (320i) with respect to the other segments (320i). The interface (300) according to any one of the above claims 6 or 7, wherein the receiving means (305, 310i) comprises a frame (305) with a plurality of recesses (310i), each for receiving one of the segments (320i). A test equipment (25, 30) for testing a device in an application equipment (10, 20), characterized by an interface (300) in accordance with any one of the above claims 6-8, and at least one segment (320i), in accordance with any one of the above claims 1-5, having electrical paths (120, 130) for providing an electrical contact between the test equipment (25, 30) and the application equipment (10, 20). An interface (300) for providing an electromagnetic link by a plurality of electromagnetic paths (120, 130) between a test equipment (25, 30) and an application equipment (10, 20), characterized in that the interface (300) comprises a plurality of individual modular and exchangeable segments (320i), at least one of which being in accordance with any one of the claims 1-5.

Inventors: ZAISER JOCHEN, ZAISER, JOCHEN
Applicants: AGILENT TECHNOLOGIES INC, AGILENT TECHNOLOGIES, INC. (A DELAWARE CORPORATION)
Application year: 1999
Main classification: G01R1
IPC codes: G01R1, G01R31, G08C19, H01L21