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Alleviating Resistor Drift

IP.com Disclosure Number: IPCOM000090430D
Original Publication Date: 1969-Apr-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 2 page(s) / 25K

Publishing Venue

IBM

Related People

Forster, RA: AUTHOR [+2]

Abstract

In resistor trimming operations in which grit is dispelled at high velocity from a nozzle to erode part of the thick-film resistor on a substrate, if all resistors on a particular substrate are not trimmed simultaneously, resistance drift occurs. Such drift is due to static change buildup on the resistor. When resistance drift occurs, the resistors trimmed during the first pass or first trimming operation decrease in value during the second pass on the previously untrimmed resistors. Additionally, those resistors that are trimmed during the second pass are usually driven into a pretrim-fail range during the first pass. Where all resistors are connected, for example in series, a floating ground can be used, that is, the same voltage is connected across all resistors, those not being trimmed as well as those being trimmed.

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Alleviating Resistor Drift

In resistor trimming operations in which grit is dispelled at high velocity from a nozzle to erode part of the thick-film resistor on a substrate, if all resistors on a particular substrate are not trimmed simultaneously, resistance drift occurs. Such drift is due to static change buildup on the resistor. When resistance drift occurs, the resistors trimmed during the first pass or first trimming operation decrease in value during the second pass on the previously untrimmed resistors. Additionally, those resistors that are trimmed during the second pass are usually driven into a pretrim-fail range during the first pass. Where all resistors are connected, for example in series, a floating ground can be used, that is, the same voltage is connected across all resistors, those not being trimmed as well as those being trimmed. Where the resistors are individually isolated, all those not being trimmed in either pass can be grounded. It is assumed that resistors R1, R2 and R3 are to be trimmed, the resistors being connected together and connected to power source 10. The resistors are also connected in separate bridge monitoring circuits to indicate when they arrive at their desired resistance during the trimming operation. Resistor R4, which is not trimmed during the first pass, is connected to power source 10, while resistors R5 and R6, being in separate circuits, are connected to ground.

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