Touch Sensor Stack Structure with Migration-Proof Layer
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Solution Overview
Problem
In conventional touch sensors, silver nanowires coated directly on a copper layer undergo a reduction reaction, leading to increased size and wire diameter, which results in reduced yield and performance due to incomplete etching and excessive etching issues during the manufacturing process.
Innovation Solution
A stack structure comprising a substrate, a copper layer, a migration-proof layer made of materials between copper and silver in the galvanic series, and a silver-nanowire layer, where the migration-proof layer is an alloy such as stainless steel, copper nickel alloy, or metals like titanium, molybdenum, and passivated nickel, which slows down the etching process and prevents silver nanowire amassing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If silver nanowires are directly coated on the copper layer, then the etching process can be simplified, but the Galvanic effect causes silver nanowires to amass and increase in size, reducing yield and performance
Solution Approach 1:
An intermediate layer is introduced between the copper layer and silver nanowire layer. This intermediate layer acts as a mediator that prevents direct contact between copper and silver, thereby eliminating the Galvanic effect that causes silver nanowire amassing while still allowing the etching solution to pass through and etch both layers effectively.
Solution Approach 2:
The structure is segmented into distinct layers: copper layer, intermediate layer, and silver nanowire layer. This segmentation physically separates the copper and silver components, preventing the harmful electrochemical interaction while maintaining the functional integrity of each layer during the etching process.
2Speed
If the etching solution etches the copper layer rapidly, then the etching speed is improved, but incomplete etching of the silver-nanowire layer and excessive etching occur
Solution Approach 1:
The intermediate layer serves as a buffer that moderates the etching process. It allows the etching solution to penetrate through at a controlled rate, preventing the rapid etching of copper from causing incomplete or excessive etching of the silver nanowire layer, thereby achieving uniform etching results.
Solution Approach 2:
The intermediate layer is positioned beforehand to cushion and regulate the etching process. It provides a controlled pathway for the etching solution, ensuring that the copper layer is etched at an appropriate speed without compromising the completeness or uniformity of the silver nanowire layer etching.
3Quantity of substance
If silver nanowires amass due to reduction reaction, then the coverage is improved, but the wire diameter increases and yield rate decreases
Solution Approach 1:
The intermediate layer prevents direct contact between copper ions and silver nanowires, thereby eliminating the reduction reaction that causes silver nanowire amassing. This maintains consistent wire diameter while ensuring adequate coverage through proper layer deposition.
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
The migration-proof layer effectively reduces the speed of etching, preventing incomplete etching and excessive etching, thereby enhancing the yield rate and performance of the touch sensor by maintaining the integrity of the silver-nanowire layer during the manufacturing process.
Implementation Method 1
Galvanic effect is generated between the copper layer and the silver nanowires whereby silver nanowires amass because of reduction reaction
Implementation Method 2
the migration-proof layer in the stack structure of the present disclosure decreases the speed at which the etching process carried out with the one-step etching solution reaches the next layer
Data Source
AI summary
A stack structure includes: a substrate, a copper layer disposed on the substrate, a migration-proof layer disposed on the copper layer, and a silver-nanowire layer disposed on the migration-proof layer, wherein the migration-proof layer is made of materials between copper and silver in galvanic series. A touch sensor includes the stack structure.