Polyimide Strain Gage Fabrication With Precise Resistance Trimming
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Solution Overview
Problem
Existing methods for fabricating flexible patterned conductors, such as strain gauges and polyimide-based resistors, face challenges in achieving precise patterning and resistance calibration, often resulting in inconsistent product quality due to inadequate surface conditioning, patterning techniques, and resistance trimming processes.
Innovation Solution
A method involving surface conditioning of flexible polyimide substrates using mechanical abrasion, scrubbing of conductive foils, precise patterning with UV radiation and photoresist, automated resistance calibration, and shunt trimming using an algorithmic approach, along with pressurized cleaning and forming an epoxy emulsion layer, to ensure accurate and consistent fabrication of flexible patterned conductors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional patterning methods are used without adequate surface conditioning, then the fabrication process is simpler, but patterning precision and resistance calibration consistency deteriorate
Solution Approach 1:
The patent applies surface conditioning (mechanical abrasion, plasma treatment, or chemical etching) to the flexible substrate before depositing the conductive foil. This preliminary action modifies the substrate surface to enhance adhesion and ensure uniform patterning, directly resolving the contradiction by preparing the surface in advance to achieve precision without requiring overly complex subsequent processes
Solution Approach 2:
The patent replaces manual or less precise patterning methods with photolithography and laser trimming. The photolithography process uses UV radiation through photoresist to create precise patterns, while laser trimming provides automated, high-precision resistance calibration, thereby achieving manufacturing precision through advanced physical methods rather than mechanical means
2Manufacturing precision
If manual resistance trimming is used, then the equipment is simpler, but resistance calibration precision and consistency deteriorate
Solution Approach 1:
The patent replaces manual resistance trimming with automated laser trimming systems. The laser trimming apparatus automatically removes conductive material to achieve precise resistance values, and the system incorporates feedback control to maintain consistency across multiple units, thereby achieving high precision through automation rather than manual operation
Solution Approach 2:
The patent implements feedback control in the resistance calibration process by measuring the actual resistance after each trimming operation and adjusting subsequent trimming accordingly. This closed-loop control ensures that the target resistance is achieved with high precision and consistency, resolving the contradiction by using automated feedback-based adjustment
3Reliability
If inadequate cleaning processes are used, then the fabrication time is shorter, but product quality and defect rates deteriorate
Solution Approach 1:
The patent performs cleaning operations at multiple stages before critical processes. Surface conditioning includes cleaning the flexible substrate before conductive foil deposition, and additional cleaning is performed after patterning before resistance calibration. These preliminary cleaning actions prevent defects that would require rework, thereby maintaining high product quality without significant time penalty
Solution Approach 2:
The patent implements continuous cleaning processes integrated into the fabrication flow rather than discrete, time-consuming separate steps. The cleaning operations are performed in-line between manufacturing steps, maintaining continuous production flow while ensuring thorough contamination removal, thus achieving both high reliability and maintained productivity
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This method enhances the precision and consistency of flexible patterned conductor fabrication, leading to improved resistance calibration and reduced defects, resulting in higher-quality strain gauges and polyimide-based resistors with accurate resistance values.
Implementation Method 1
patterning the conductive foil employs applying UV radiation through a patterned mask which fully covers generally only the conductive foil
Implementation Method 2
surface conditioning of the flexible polyimide substrate using mechanical abrasion
Data Source
AI summary
A method of manufacture of a strain gage or flexible polyimide-based resistor, the method including the steps of providing a flexible polyimide substrate, joining a conductive foil to the flexible polyimide substrate, applying a layer of photoresist to the conductive foil and thereafter, patterning the conductive foil by etching using the photoresist, wherein the method is characterized in that it includes at least one of the following steps: surface conditioning of the flexible polyimide substrate using mechanical abrasion, scrubbing of the conductive foil prior to the patterning, removal of photoresist by scrubbing following the patterning, pressurized cleaning, using deionized water, following the patterning, automated algorithmic resistance calibration and shunt trimming and forming an emulsion layer of epoxy over the conductive foil following the patterning.