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Method for a built-in metal foil electrical-resistance strain gauge in a flexible printed circuit

IP.com Disclosure Number: IPCOM000011841D
Publication Date: 2003-Mar-19
Document File: 4 page(s) / 57K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method for a built-in metal foil electrical-resistance strain gauge in a flexible printed circuit. Benefits include improved functionality, improved performance, improved design flexibility, and an improved test environment.

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Method for a built-in metal foil electrical-resistance strain gauge in a flexible printed circuit

Disclosed is a method for a built-in metal foil electrical-resistance strain gauge in a flexible printed circuit. Benefits include improved functionality, improved performance, improved design flexibility, and an improved test environment.

Background

        � � � � � Stress analysis is conventionally performed by measuring strains on the surface of a flexible printed circuit or a production component. Several experimental methods available for measuring strain, including:

•        � � � � Mechanical

•        � � � � Acoustical

•        � � � � Electrical

•        � � � � Optical

•        � � � � Moiré

        � � � � � The metal foil electrical-resistance strain gauge is the most frequent choice of experimentalists because of its cost-effectiveness. However, strain gauge attachment to the flex circuit is a very tedious manual process that can significantly affect the accuracy of the data collected because of operator and adhesive material variations.

        � � � � � No clear solution eliminates the operator and material variations. Measurement capability analysis, however, can be applied to quantify the variations and further minimize them.

General description

        � � � � � The disclosed method is a built-in metal foil electrical-resistance strain gauge in a flexible printed circuit. The method enables in-place package strain measurement for stress analysis. The gauges can be developed as part of the flexible circuit fabrication process with the photographic production of a master image of gauge grid patterns followed by the foil-etching process. This process enables miniaturization of the grids, versatility of grid configuration, and enhanced control of gauge quality and accuracy. Strain gauges can be built in at any location within the flex circuits to provide a near full-field strain measurement. The tedious sample preparation found in traditional strain gauge applications in flex circuits is eliminated.

        � � � � � The key elements of the method include:

•        � � � � Strain gauge grid pattern (strain-sensing element)

•        � � � � Thin film as an insulator

•        � � � � Carrier for strain-sensing element

•        � � � � Tabs (or terminals) for lead wire connections in the flexible printed circuits.

Advantages

        � � � � � The disclosed method provides advantages, including:

•        � � � � Improved functionality due to enabling miniaturization of the grids

•        � � � � Improved performance due to enhancing the control of gauge quality and accuracy

•        � � � � Improved design flexibility due to versatility of grid configuration

•        � � � � Improved test environment due to the capability to be built in at any location within the flex circuit to provide a near full-field strain measurement

•        � � � � Improved test environment due to eliminating the tedious sample preparation found in conventional strain gauge applications in flex circuits

•        � � � � Improved cost effectiveness due to being created in place as...