Automatic test equipment or ATE is used to test semiconductor or other type devices at various stages of manufacture. Typically, an ATE tester supplies power and test signals, from instrument cards located in a test head, to a device interface board or DIB for routing to selected pins of a device under test or DUT.
As devices continue to operate at ever increasing speeds, and include ever increasing numbers of transistors, providing a stable source of power during dynamic modes of operation becomes problematic. The ATE power supply often responds to dynamic current changes of, for example, 300 amperes, within a few picoseconds. At these levels of current switching performance, inductance and minute resistances pose significant problems, tending to inhibit changes in current, thereby affecting the device-under-test. Typically, during dynamic modes of power supply operation, responsive high current waveforms are supplied by the instrument card to the DIB via a bus bar, or a heavy gauge wire, such as for example a 0.4 AWG cable.
Large diameter cables and bus bars are bulky and not easily maneuvered. This can be undesirable in certain ATE applications. In certain applications, for example, it may influence the positioning of the connector when mating with the DIB, or it can otherwise hinder operations nearby. Further, in precision testing applications, a corresponding return line is also provided between the instrument card and the DIB. Thus, a pair of cables is used, increasing such effects. In a paired force/return cable arrangement, mutual inductance is a concern. Since inductance sums along the length of the cable, this can limit high frequency response. Also, reliable, low inductance connection is not easily provided at low cost.
Conventional laminated foil straps are not easily manufactured to provide reliable interconnection at low cost, and do not provide high current interfacing with extremely low inductance. Such is often desired by ATE testers to provide precision testing of DUT's capable of operating at very high frequency.
In one embodiment a high power interface apparatus is provided having a multilayer laminated cable including force conductor planes having flush and recessed portions and return conductor planes having flush and recessed portions. The flush portions of the conductor planes extend to a contact end of the laminated cable and the recessed portions are removed from the contact end. The flush portions are aligned along axes at the contact end. The flush portions of the return conductor planes are aligned at the contact end along axes aligned within recessed portions of the force conductor planes. A dielectric material separates the force and return conductor planes.
In certain embodiments, surface contact pads are provided on the contact end. The surface contact pads include force contact pads, each contacting and extending along aligned flush portions of the force conductor planes, and also include return conductor pads, each contacting and extending along aligned flush portions of the return conductor planes. The contact pads may be formed by depositing and removing conductor material at the contact end of the cable. In some implementations, the end of the cable may be plated, and then scored, such as with a drill to define the pads. The recessed portions of the conductor planes may be formed wider than the flush portions to facilitate formation of the contact pads.
The multilayer laminate cable may be formed with a rigid portion near the contact end and a flexible portion between the cable ends. In some embodiments the force and return conductor planes of the flexible portion extend to the ends of the cable with the rigid portion having with additional force and return conductor planes. In such an embodiment, through vias may be provided in the rigid portion, to electrically couple the force conductor planes together and to electrically couple the return conductor planes together. Depending on the thickness of the rigid portion and the fabrication technique, the rigid end portion may be sliced into sub-portions to facilitate formation of the vias, and then recombined if desired. An alignment means such as holes may be provided at the cable end to facilitate recombination.
Some embodiments may have the contact pads formed at both ends of the cable, while other embodiments may have contact tabs extending from a second end of the laminated cable. In such an embodiment, the force and return conductor planes are integrally formed with contact tabs. The contact tabs of the force and return conductor planes are in a staggered configuration such that the force contact tabs are located on one side of an axis of separation and the return contact tabs are located on the other side of the axis of separation. A rigid end connector may be provide thereon, adapted to receive a plurality of the contact tabs in electrically isolated portions so that the contact tabs from one side of the axis of separation are received in one of the electrically isolated portions and the contact tabs from the other side of the axis of separation in an other of the electrically isolated portions. In still other embodiments both ends of the laminated cable may have the contact tabs.
To minimize inductance, each of the conductor planes is separated by a dielectric material distributed along the length of the cable 70. Further, the cable is configured such that successive conductor planes provide either a force or a return path. Thus, every other conductor plane is either a force or a return path.
The flush portions 85 extend to the contact end 75, and the recessed portions 87 are recessed from the contact end 75. The flush portions 85 of every other conductor layer 80 are aligned within the recessed portions 87 such that the flush portions 85 of successive conductor planes 80 are in a staggered configuration. The flush portions 85 of alternating conductor planes 80 are aligned.
In some embodiments, the recessed portions 87 are wider than the corresponding flush portions 85 that are located above and below the recessed portions 87. Thus, in some embodiments, the recessed portions 87 extend beyond the width of the flush portions 85 by a gap 86 amount (shown by phantom lines) along the edges of the flush portions 85. The gaps 86 inhibit formation of electrical continuity between force and return conductor planes by the contact pads 100, or by an interconnection means, such as the interposer 110 (shown in FIG. 2).
The laminate structure of the conductor planes 80 and the dielectric planes 90 may be formed by masking, deposition, and etching techniques typically utilized in forming printed circuit boards. Thus in one embodiment, between the conductor material of adjacent conductor planes, is deposited a prepreg material followed by a polyemet material, followed by prepreg material. The polyemet material may be any dielectric material capable of providing flex in combination with the prepreg material, such as that known by the trademark KAPTON, by DuPont.
With the above discussed embodiments, improved inductance is obtained by providing alternating stacked planes of force and return separated by dielectric material substantially along the length of the cable. Inductance characteristics of the interface can be further improved by providing multiple force and return contact pads, and by locating the force contact pads beside and interdigitated with the return contact pads. Thus, higher frequency switching of high current signals may be achieved.
Although shown in
Referring to
Appropriate prepreg compositions and selective curing processes are utilized during the fabrication process to produce integrally formed rigid and flexible portions 72 and 74. Hence, the flexible portion 72 is fabricated with flexible dielectric material, such as KAPTON. The rigid end 74, on the other hand, may be formed of the same dielectric material, or of a rigid dielectric material, if desired. In this implementation, such a process provides a robust low impedance laminated cable at reduced cost.
In some embodiments, the rigid end 74 will have the same number of conductor planes as the flexible portion 72. In other embodiments, the number of conductor planes in the rigid end 74 will be different than the number of conductor planes in the flexible portion 72.
In one implementation, the through vias (not shown) are formed by drilling and filling after the deposition of the conductor and dielectric planes 280 and 290. Depending on the size and number of conductor planes 280 in the rigid portion 274, the rigid portion may be sliced to reduce the number of layers for the drilling and filling process. Thereafter, the sliced portions may be recombined, such as with an adhesive 265, or other fastening means. In such an implementation, an alignment hole, aperture, key, surface, or other such means (not shown) is provided along the rigid portion 274 to facilitate recombination of sliced portions.
Contact pads may be formed on the end 275 of the cable 270 as discussed above. Contact pad 200 is shown contacting the flush portion 285 of alternating layers of the conductor planes 280. The recessed portions 287 are recessed from the contact pad 200 shown in FIG. 8.
One or both ends of the laminated cable may be provided with contact pads as discussed with reference to
Turning to
The tab extensions 410 and 415 may be integrally formed with the conductor planes of the flexible portion 465 to provide straight through connection, or they may provide a distributed connection as discussed with reference to FIG. 8. The tab extensions 410 and 415 may be utilized to coupled directly, or via a connector, to a circuit board, such as the instrument card 20 shown in FIG. 1.
In yet other embodiments as shown in
Turning to
The connector 600 has two electrically isolate portions 602 and 603 for receiving tab extension from alternating layers, and thus corresponding to the force and return paths of the conductor planes. The connector 600 is adapted so that the isolated portions 602 and 603 couple signals to pins 725 and 726, such as those known under the trademark HYPERTRONICS manufactured by Hypertronics of Hudson, Mass. Although only two portions 602 and 603 are shown, other configurations with four or more portions are also envisioned.
In some embodiments, one end of the laminated cable may be provided with the connections means discussed with reference to
While the preferred embodiments of the present invention have been described in detail above, many changes to these embodiments may be made without departing from the true scope and teachings of the present invention. The present invention, therefore, is limited only as claimed below and the equivalents thereof.
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3818119 | Sutherland et al. | Jun 1974 | A |
4085502 | Ostman et al. | Apr 1978 | A |
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Number | Date | Country | |
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20040060725 A1 | Apr 2004 | US |