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Resistor Trimming

IP.com Disclosure Number: IPCOM000092055D
Original Publication Date: 1968-Aug-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 2 page(s) / 25K

Publishing Venue

IBM

Related People

Kamenetsky, S: AUTHOR [+4]

Abstract

This is a method for trimming resistors after they have been assembled in a circuit module. More precise values of resistance are obtained. This is accomplished by use of abrasive nozzles which are brought in contact with resistors to be trimmed. These nozzles are under the control of a circuit which continually monitors the values of resistance. When the resistors in a circuit are trimmed to a desired value, the abrasive nozzles are withdrawn and the circuit module is indexed from the trimming apparatus.

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Resistor Trimming

This is a method for trimming resistors after they have been assembled in a circuit module. More precise values of resistance are obtained. This is accomplished by use of abrasive nozzles which are brought in contact with resistors to be trimmed. These nozzles are under the control of a circuit which continually monitors the values of resistance. When the resistors in a circuit are trimmed to a desired value, the abrasive nozzles are withdrawn and the circuit module is indexed from the trimming apparatus.

There are some modules which cannot be programmed for the trimming of all resistors simultaneously because of their particular physical configuration. In drawing 1, assume that resistors R1, R2, and R3 are in a configuration such that all three cannot be trimmed simultaneously. In a single pass of the abrasive nozzles over the module, only R1 and R2 or R2 and R3 can be trimmed in the following manner. R1 and R2 are placed in bridges and trimmed, but R3 cannot be trimmed independently, drawing 2. R2 and R3 are placed in bridges and trimmed, but R1 cannot be trimmed independently, drawing 3.

Conventional techniques require that the circuit modules be physically circulated through the trimming apparatus twice. This snapback method eliminates double handling through the trimming machine. With snapback, in a first pass of the abrasive nozzles over the module, the ground connection is between R1 and R2. The latter are connected in bridges and trimmed...