Touch Sensor Tail Structure for Crack-Free Fine-Pitch Terminals
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Solution Overview
Problem
Touch sensors often suffer from defects such as cracks or increased wire pitch due to the carbon terminal protective layer, which can lead to electrical communication issues and reliability problems.
Innovation Solution
A touch sensor design featuring a substrate film with a maximum thickness at the terminal and a protective layer with a fine pitch, along with an inextensible film covering the terminal, to minimize elongation and prevent cracking, and a method of producing this sensor with three-dimensionally formed components to ensure high reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a thin coating carbon layer is formed at fine pitch to cover individual wires in the tail, then electrical communication between adjacent wires is prevented, but cracks or increased wire pitch occur due to substrate film elongation during three-dimensional forming
Solution Approach 1:
The carbon layer is formed on the flat substrate film before the three-dimensional forming process. This preliminary formation ensures that the carbon layer is deposited on a stable, non-elongated surface, preventing subsequent cracking or pitch variation that would occur if formed after shaping
Solution Approach 2:
The carbon layer is divided into multiple segments arranged at fine pitch along the wire length. Each segment independently covers individual wires, preventing electrical communication between adjacent wires while maintaining flexibility during the forming process
2Shape
If the substrate film is three-dimensionally shaped to create the input detection portion, then the touch sensor achieves its functional form, but the terminal region experiences elongation causing wire and protective layer deformation
Solution Approach 1:
The substrate film exhibits different thickness characteristics at different locations: it is thicker in the terminal region and thinner in the input detection portion. This local variation in thickness provides structural support where needed while allowing flexibility where required
Solution Approach 2:
The terminal region is formed and stabilized before the three-dimensional shaping process. By establishing the terminal structure first on the flat substrate, subsequent forming operations do not cause elongation or deformation of the terminal wires or protective layers
Data Source
AI summary
To provide a touch sensor including a tail having a terminal protective layer that allows smooth insertion into or removal from a circuit board without causing any problem, which is likely to occur in a typical terminal protective layer provided on a terminal at a distal end of a tail of a touch sensor used for, for example, input operations of various electronic devices. A touch sensor having a plurality of sensor electrodes and a plurality of wires on a single substrate film includes a body including a flat portion and a deformed portion, which is three-dimensionally shaped relative to the flat portion surrounding the deformed portion and has an operation surface having the sensor electrodes, and a tail projecting from the body and having a terminal to connect the wires to a circuit board. The terminal has a terminal protective layer protecting the wires.