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Test Probe With Variable Ground and Constant Impedance Capabilities

IP.com Disclosure Number: IPCOM000083868D
Original Publication Date: 1975-Aug-01
Included in the Prior Art Database: 2005-Mar-01
Document File: 2 page(s) / 33K

Publishing Venue

IBM

Related People

Marasch, MR: AUTHOR [+2]

Abstract

Recent developments in high-density semiconductor packaging have created the need for a compact AC test probe with an easily variable-ground pitch.

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Test Probe With Variable Ground and Constant Impedance Capabilities

Recent developments in high-density semiconductor packaging have created the need for a compact AC test probe with an easily variable-ground pitch.

In view of the need to obtain optimal usage of surface area in semiconductor packages, probe pads now tend to be designed to be of unequal distances from probable ground points at almost every package level. This creates severe problems in carrying out AC probing with conventional techniques and equipment.

In addition, in present semiconductor package designs the signal lines tend to be extremely short. Accordingly, when using conventional time domain reflectometer techniques, any large inductive or capacitive discontinuities resident within the probe tend to mask line measurements.

A probe is illustrated which solves the above problems by providing an easily variable pitch between the signal and the ground terminals, and providing matched impedance at the probe tips. Interchangeable probe tips are provided to enable divider action for AC measurements, or matched impedance for time domain reflectometer measurements.

The probe 10 utilizes a thumb wheel operated rack and pinion drive 14 to position a movable, nonrotating ground contact 16 relative to a fixed signal contact 18. A capability is provided to utilize interchangeable passive probe tips to provide matched 50 ohm or 90 ohm impedance to the probe tips. The probe tip divider ratio is determined t...