Abstract:
Contact ring, which is brought into contact with a probe card having tungsten needles, has a multiplicity of POGO pins on its one surface facing the probe card. The contact ring has, on another surface opposite to the one surface, press-fitting sockets electrically connected with the POGO pins. Motherboard has sockets similar in construction to the press-fitting sockets of the contact ring. Coaxial cables each have press-fit terminals that are press-fittable in one of the sockets of the contact ring and in one of the sockets of the motherboard, and thereby these coaxial cables electrically connect the contact ring with the motherboard. Because the contact ring and the motherboard are electrically connected with each other by the press-fit engagement alone, there are encountered no inconveniences due to the conventional soldering-based connection.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates generally to interface units for testers that test electrical characteristics of IC (Integrated Circuit) devices and other semiconductor devices. More particularly, the present invention relates to a tester interface unit for providing electrical connection between a contact ring and a motherboard, and a method of connecting the tester with a semiconductor device to be tested. 
     In order to ship IC devices with performance and quality assurances as final products, it is generally necessary to extract some or all of the IC devices and examine predetermined electrical characteristics of the extracted devices in manufacturing and test stages. Normally, the electrical characteristics of the IC devices are examined by so-called IC testers. In many cases, the IC testers perform a probe test for examining IC devices formed on a semiconductor wafer prior to a final test step. For examination of the IC devices on the semiconductor wafer, a special test device called a “probe device (or probe card)” is required which connects the IC devices to the IC tester. Each of the ordinary-type probe devices operates in a so-called cantilever fashion. Namely, each of these probe devices has a plurality of tungsten needles manually soldered onto a printed circuit board and projecting obliquely from the printed circuit board, and the obliquely-projecting tungsten needles are resiliently pressed against bonding pads of the IC devices. Therefore, the number of the IC devices that can be examined simultaneously depends greatly on the technology for manufacturing the probe device. 
     In recent years, the number of IC devices capable of being examined simultaneously has been progressively increasing, such as 16, 32 and 64. As the number of IC devices capable of being examined simultaneously increases there arises a need to reliably connect signal lines corresponding to 1,000 to 3,000 pins between the probe device and the tester, not to mention a need for a technique of fixing the needles with high accuracy. The probe devices today generally include a signal-line-connecting area that is located off and around the outer periphery of a central needle-fixing area, and thus it has become extremely difficult to form, in that signal-line-connecting area, a wiring pattern for supplying electric signals to 3,000 or more pins. Further, because the wiring pattern is connected with the signal lines by soldering, there would arise the problems that gold-plated pads of the IC devices are smudged or stained by a flux used in the soldering and a leakage current is produced between the pins by the flux. 
     Japanese Patent Laid-open Publication No. HEI-8-139142 discloses using a POGO pin ring in the form of an annular board. The POGO pin ring disclosed in the publication has a large number of POGO pins on opposite surfaces thereof. The POGO pins on one of the two surfaces are electrically connected with those on the other surface in a one-to-one relation. The one surface of the POGO pin ring is brought into contact with a performance board associated with a test head while the other surface of the POGO pin ring is brought into contact with a probe card, so that an electrical connection is achieved between the test head and the probe card. In this case, the distance or interval between the test head and the probe card is fixedly defined by the thickness of the POGO pin ring, and thus the tester is unavoidably fixed in construction, which would result in poor operability of the tester. 
     SUMMARY OF THE INVENTION 
     It is therefore an object of the present invention to provide an interface unit for a tester which can effectively avoid inconveniences encountered in connecting signals lines regardless of an increase in the number of simultaneously-tested IC devices and thereby achieves highly-reliable connection between the signal lines. 
     In order to accomplish the above-mentioned object, the present invention provides an interface unit for a tester which comprises: a contact board having a large number of contact terminals provided on one surface thereof, and sockets provided on another surface thereof and electrically connected with the contact terminals; a motherboard having a large number of wires to be connected to the contact terminals of the contact board, and a large number of sockets electrically connected with the wires; and a large number of connecting cables each having two plugs provided at opposite ends thereof. The plug provided at one end of each of the connecting cables is removably inserted in one of the sockets of the contact board and the plug provided at another end of each of the connecting cables is removably inserted in one of the sockets of the motherboard, so that the connecting cables electrically connect the contact terminals of the contact board with the wires of the motherboard. 
     The tester interface unit is used for providing electrical connection between a test control section and a probe section of a tester for an IC or other semiconductor device. The wires of the motherboard are connected to the test control section and the contact terminals provided on the one surface of the contact board are placed in contact with contact terminals of the probe section. The probe section is a probe card having the above-mentioned contact terminals on one surface thereof and contact needles, such as tungsten needles, on the other surface thereof, and the contact terminals of this probe section are electrically connected with the contact needles. When performing a test, the contact needles of the probe section are placed in contact with predetermined terminals of the device to be tested such as a semiconductor wafer, semiconductor device or IC. 
     The contact board is a contact ring having an annular shape, and the contact terminals provided on its one surface facing the probe card are resiliently movable contact pins such as POGO pins. This contact ring has, on the other surface, press-fitting sockets electrically connected with the POGO pins. The motherboard also has sockets that are similar in construction to the press-fitting sockets of the contact ring. By press-fitting plugs at opposite ends of connecting cables in desired ones of the sockets of the contact board and motherboard, the contact terminals (POGO pins) of the contact ring and the contact terminals of the motherboard are electrically connected with each other. Because the contact ring and the motherboard are electrically connected with each other only by the press-fit engagement between the plugs and the sockets, there are encountered no inconveniences that would result from the conventional soldering-based connection. Such plugs and sockets are preferred in that they can be firmly press-fitted with each other with increased reliability. For examples, each of the connecting cables is a coaxial cable including mold terminal sections at opposite ends thereof, and each of the mold terminal sections has at least two plugs projecting therefrom. Although it is preferable that the contact terminals provided on the one surface of the contact board be POGO pins as noted above, any other contact terminals than the POGO pins may be employed. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     For better understanding of the object and other features of the present invention, its preferred embodiments will be described in greater detail hereinbelow with reference to the accompanying drawings, in which: 
     FIG. 1 is a perspective view showing specific constructions of a motherboard, coaxial cables and contact ring in a tester interface unit in accordance with a preferred embodiment of the present invention; 
     FIG. 2 is a diagram schematically showing a general hardware organization of an IC tester employing a probe device of the present invention; and 
     FIG. 3 is a sectional view showing details of a connection between the coaxial cable and the contact ring of FIG. 1 and a connection between the coaxial cable and the motherboard. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 2 is a diagram schematically showing a general hardware organization of an IC tester employing an interface unit in accordance with a preferred embodiment of the present invention. Semiconductor wafer  21  includes a plurality of IC device chips formed thereon. XYZ stage  22  functions to position a tray  23 , for placing thereon the semiconductor wafer  21 , in three dimensions and rotate the wafer tray  23  about its Z axis. 
     Test station  24  determines a pin arrangement corresponding to a pin electronics card to be mounted, and this test station  24  is connected with an interface unit of a device to be tested (hereinafter “tested-device interface unit”). The tested-device interface unit includes a motherboard  25  and a plurality of coaxial cables  27 . The motherboard  25  is in the form of a printed circuit board and is connected to the test station  24 . The plurality of coaxial cables  27  electrically connect the motherboard  25  with a contact ring (or contact board)  26 . 
     The contact ring  26  in this preferred embodiment has, on its one surface facing a probe card  28 , groups of contact terminals  31 ,  34  commonly called POGO pins. Whereas the POGO pins in the conventionally-known probe devices are provided on opposite surfaces of the contact ring facing the probe card and motherboard, the POGO pins in the present invention are provided only on one surface of the contact ring facing the probe card. Specific constructions of the motherboard  25 , coaxial cables  27  and contact ring  26  will be described later. The probe card  28 , which is of the conventional construction, has a large number of tungsten needles  29  soldered thereon for contact with pads of the chips formed on the semiconductor wafer  21 . Using the probe device of such a construction, a test signal is supplied to each of the chips on the semiconductor wafer  21  in order to examine predetermined electrical characteristics of the chip. 
     FIG. 1 is a perspective view showing specific constructions of the motherboard  25 , coaxial cables  27  and contact ring  26 . In FIG. 1, the motherboard  25 , coaxial cables  27  and contact ring  26  are shown in opposite positional relationship to that of FIG. 2; that is, in FIG. 1, the contact ring  26  is shown as positioned above the coaxial cables  27  and the coaxial cables  27  above the motherboard  25 . Further, FIG. 3 is a sectional view showing details of a connection between the coaxial cable  27  and the contact ring  26  of FIG. 1 and a connection between the coaxial cable  27  and the motherboard  25 . As shown in FIG. 3, the contact ring  26  has a large number of the POGO pins only on its one surface facing the probe card  28 . 
     The POGO pins  31  serve as signal contact terminals, while the POGO pins  34  serve as grounding contact terminals. Because the POGO pins  31  and  34  are identical to each other in construction, the POGO pins  31  will be described in detail below. Each of the POGO pins  31  includes an electrically conductive socket  32  having a cylindrical shape, whose interior is divided vertically into two interior portions  32   a  and  32   b . Contact pin  33  is disposed within one of the two interior portions of the conductive socket  32  for vertical movement along the inner surface of the one or upper interior portion  32   a . Only a tapered distal (upper) end portion of the contact pin  33  projects upwardly beyond the upper cylindrical interior space of the conductive socket  32 . More specifically, the tapered distal end portion of the contact pin  33  projects upwardly through an opening of the conductive socket  32  that is smaller in diameter than the non-tapered body of the pin  33 . Each of the contact pins  33  constituting the POGO pins may be constructed in any other way as long as the contact pin  33  is movable vertically within the interior portion of the conductive socket  32 . Similarly, each of the other POGO pins  34  is constructed of an electrically-conductive socket  35  having two interior portions  35   a  and  35   b  and a contact pin  36 . The motherboard  25  and the coaxial cables  27  are connected with each other via a large number of electrically-conductive sockets  25 A and  25 B each in the form of a through-hole in the motherboard  25 . 
     Mold terminal sections  27 A and  27 B are provided at opposite ends of each of the coaxial cables  27 . The mold terminal section  27 B includes press-fit terminals  27 S and  27 E. The other mold terminal section  27 A includes press-fit terminals  27 T and  27 F. The press-fit terminals  27 S and  27 T are connected to an inner conductor of the coaxial cable  27  within the mold terminal sections  27 A and  27 B, and similarly the press-fit terminals  27 E and  27 F are connected to an outer conductor of the coaxial cable  27  within the mold terminal sections  27 A and  27 B. On the outer surface of each of the mold terminal sections  27 A and  27 B, there is put a mark  27 C indicating that the press-fit terminals  27 S and  27 T are terminals for signal lines. Each of the above-mentioned press-fit terminals  27 S,  27 E,  27 T and  27 F are each a pin-shaped plug provided with a resilient spring-like contact C. 
     As also shown in FIG. 3, the press-fit terminal  27 S of the mold terminal section  27 B is press-fitted in the other or lower cylindrical interior portion  32   b  of the conductive socket  32 , and the press-fit terminal  27 E of the mold terminal section  27 B is press-fitted in the other or lower cylindrical interior portion  35   b  of the conductive socket  35 . By the press-fit terminals  27 S and  27 E thus press-fitted in the lower cylindrical interior portions  3   b  and  35   b  of the conductive sockets  32  and  35 , respectively, the above-mentioned, spring-like contacts C of the terminals  27 S and  27 E are firmly pressed against and electrically connected to the respective inner surfaces of the sockets  32  and  35 . Similarly, the press-fit terminal  27 T of the mold terminal sectiomn  27 A is press-fitted in the through-hole of the conductive socket  25 A and the press-fit terminal  27 F of the mold terminal section  27 A is press-fitted in the through-hole of the conductive socket  25 B, so that the contacts C of the plugs  27 T and  27 F are pressed against and electrically connected to the respective inner surfaces of the sockets  25 A and  25 B. 
     FIG. 1 illustrates an example where there are provided a total of  216  POGO pins on one surface of the contact ring  26 , six POGO pins in each radial row. Therefore, the mold terminal sections  27 B of a total of  108  coaxial cables, three coaxial cables in each radial row, are press-fitted in the other surface of the contact ring  26  which is opposite to the one surface where the POGO pins are provided. The mold terminal sections  27 A of the  108  coaxial cables are, on the other hand, press-fitted in the through-holes of the conductive sockets  25 A and  25 B that are provided in the motherboard  25  along its circumference greater in diameter than the contact ring  26 . Because the coaxial cables  27 , contact ring  26  and motherboard  25  are electrically connected with each other by press-fitting engagement with no soldering, reliability of the electrical connections can be greatly increased, which achieves high-density packaging. Besides, this press-fitting arrangement can eliminate the possibilities of the gold-plated pads being smudged or stained by a flux used in soldering and the flux producing a leakage current between the pins. 
     The example of FIG. 1 has been described as having  216  POGO pins; in practice, however, 1,000 to 3,000 or a greater number of POGO pins are electrically connected using the coaxial cables. Further, in the present invention, the contact ring  26  and the motherboard  25  are mechanically connected with each other by given coupling (not shown). Furthermore, in a situation where several of the coaxial cables  27  are used as power supply cables, these coaxial cables  27  may be used with their respective inner and outer conductors short-circuited. 
     The preferred embodiment of the present invention has been described above in relation to the case where two mold terminal sections having signal press-fit terminals and grounding press-fit terminals are provided for each of the coaxial cables. However, the present invention is not so limited, and mold terminal sections having N (which is an arbitrary positive integer) signal press-fit terminals and N grounding press-fit terminals may be provided for N coaxial cables. Alternatively, mold terminal sections having N signal press-fit terminals and N or more grounding press-fit terminals may be provided for N coaxial cables. Namely, where a plurality of the grounding POGO pins are to be provided around each of the signal press-fit terminal, it is only necessary that the mold terminal section be constructed to have the grounding press-fit terminals greater in number than the signal press-fit terminal. It should also be apparent that the spring-like contacts C may be provided on the sockets ( 32 ,  35 ,  25 A,  25 B) rather than on the plugs (terminals  27 S,  27 E,  27 T,  27 F). 
     Furthermore, whereas the present invention has been described above in relation to a probe tester for testing IC devices in the form of a semiconductor wafer, it should be apparent that the present invention is also applicable as an interface unit for providing electrical connection between the contact ring and the motherboard. Moreover, whereas the present invention has been described in relation to an IC tester, it can of course be applied to a package tester, logic tester and the like. Therefore, the contact ring employed in the present invention does not have to be always ring-shaped and may be a plate having any desired shape. 
     In summary, the tester interface unit in accordance with the present invention achieves highly-reliable connection between signal lines.