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Browse Prior Art Database

Package Test Chip

IP.com Disclosure Number: IPCOM000042405D
Original Publication Date: 1984-May-01
Included in the Prior Art Database: 2005-Feb-03
Document File: 2 page(s) / 48K

Publishing Venue

IBM

Related People

Anderson, CJ: AUTHOR

Abstract

Multiple resistive splits on a package test chip provide for testing several different low temperature chips having the same package footprint. The test chip shown in Fig. 1 has four inputs to resistive splits. Low temperature testing may take place at liquid helium (4.2K) temperature. The outputs of the resistor splits go to all the rest of the chip signal pads. The resistor RS used in the resistor split should be about 200 L, which is much larger than the series resistance in the input/output (I/O) cable from room temperature. The inputs to the resistor splits should be symmetric about the chip, but the wiring of the outputs of the resistor split to the pads should not be symmetric about the chip, because then the chip can be rotated and have a different wiring configuration. Fig.

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Package Test Chip

Multiple resistive splits on a package test chip provide for testing several different low temperature chips having the same package footprint. The test chip shown in Fig. 1 has four inputs to resistive splits. Low temperature testing may take place at liquid helium (4.2K) temperature. The outputs of the resistor splits go to all the rest of the chip signal pads. The resistor RS used in the resistor split should be about 200 L, which is much larger than the series resistance in the input/output (I/O) cable from room temperature. The inputs to the resistor splits should be symmetric about the chip, but the wiring of the outputs of the resistor split to the pads should not be symmetric about the chip, because then the chip can be rotated and have a different wiring configuration. Fig. 2 shows a simple two-chip package and how it would be tested using the resistive split chip. A current (6I shown as example) is injected into one of the resistor splits and all the other package I/Os (including the package ground) are grounded through ammeters. All the return current has to be accounted for; if a different amount of current returns through an I/O than anticipated, then there is a short or open in the package. Each resistor split is used as both input and output. To test the rest of the package, current is injected into the other resistor splits one at a time. The package fault that would not be testable is an interlevel short between two lines that h...