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Browse Prior Art Database

Cryogenic Testing of Josephson Chips

IP.com Disclosure Number: IPCOM000051698D
Original Publication Date: 1981-Feb-01
Included in the Prior Art Database: 2005-Feb-10
Document File: 2 page(s) / 45K

Publishing Venue

IBM

Related People

Byrnes, H: AUTHOR [+3]

Abstract

In the testing of Josephson device chips, it is necessary to provide a contactor package which will work well at 4.2 degrees K. Such a package has to have minimal length contact paths and in conjunction avoid the problem of differential contraction between different materials. If undue contraction occurs, it will not be possible to align contacts to pads on the chip under test. It is also desirable to minimize stray magnetic fields at the chip since Josephson circuits depend upon magnetic fields for their switching properties. The package shown in Figs. 1 and 2 uses miniature contacts, a silicon space transformer, and a molybdenum alignment frame to solve these problems.

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Cryogenic Testing of Josephson Chips

In the testing of Josephson device chips, it is necessary to provide a contactor package which will work well at 4.2 degrees K. Such a package has to have minimal length contact paths and in conjunction avoid the problem of differential contraction between different materials. If undue contraction occurs, it will not be possible to align contacts to pads on the chip under test. It is also desirable to minimize stray magnetic fields at the chip since Josephson circuits depend upon magnetic fields for their switching properties. The package shown in Figs. 1 and 2 uses miniature contacts, a silicon space transformer, and a molybdenum alignment frame to solve these problems.

A pressure block 10 is used to press the chip under test 12 onto the miniature flexible contacts 18. Molybdenum frame 14 aligns the chip to the contacts 18. Beneath frame 14 is a silicon space transformer 16. Mini-cobra contacts 1a (Fig.
2) of the type described in U.S. Patent 4,027,935 are mounted in polyimide dies 20, and are held in position by the frame 14. An alignment shim 22 is located between frame 14 and the mounting plate 24. Alignment pins 26 secure alignment of the components of this chip-test package.

The low thermal contraction of molybdenum makes possible the alignment of the contacts 18 to pads on the chip 12, and also to pads on transformer 16, to a high precision. Electrical testing of chip 12 can occur in liquid helium at 4.2 degrees K.

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