Capacitive Bond Pad Coupling for Touch Sensor Assembly
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Solution Overview
Problem
In touch sensor technology, moisture ingress and increased manufacturing costs arise due to gaps between the screen and touch sensor, and creases can damage sensors from multiple bonding operations when coupling dual-sided sensors to components like flexible printed circuits (FPCs).
Innovation Solution
Capacitively coupling bond pads on one side of the touch sensor allows for the attachment of the circuit on a single side, reducing the need for multiple bonding operations, minimizing gaps, and preventing creases, while enabling the use of dual-layer touch sensors in manufacturing processes like in-mold lamination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple bonding operations are performed to couple dual-sided sensors to components, then connection reliability is improved, but manufacturing complexity and cost increase
Solution Approach 1:
The invention extracts the bonding operation from one side of the touch sensor, performing bonding only on the rear surface while leaving the front surface unbonded. This eliminates the need for multiple bonding operations while maintaining connection reliability, as the capacitive coupling through the substrate provides sufficient electrical connection without requiring bonding on both sides.
Solution Approach 2:
The touch sensor substrate acts as an intermediary that enables capacitive coupling between the front surface bond pads and the rear surface bond pads. This intermediary mechanism allows electrical connection to be achieved through the substrate itself, eliminating the need for separate bonding operations on both sides while maintaining reliable signal transmission.
2Reliability
If multiple bonding operations are performed to couple dual-sided sensors, then connection reliability is improved, but manufacturing time and cost increase
Solution Approach 1:
The invention removes one bonding operation from the manufacturing process by performing bonding only on the rear surface of the touch sensor. This extraction of the redundant bonding step reduces manufacturing time and cost while maintaining adequate connection reliability through capacitive coupling across the substrate.
3Reliability
If bonding operations are performed on dual-sided sensors, then electrical connection is achieved, but creases are formed that can damage the sensor
Solution Approach 1:
The invention extracts the bonding operation from the front surface of the touch sensor, performing bonding only on the rear surface. This eliminates the source of creases that would form during bonding while maintaining electrical connection through capacitive coupling through the substrate, thereby preventing mechanical damage to the sensor.
4Adaptability or versatility
If gaps are present between the screen and touch sensor, then assembly flexibility is improved, but moisture ingress occurs
Solution Approach 1:
The invention uses optically clear adhesive (OCA) sheets as a temporary spacing mechanism during assembly that can be easily applied and removed. These OCA sheets maintain gap control during the bonding process but are designed to be consumable materials that are removed after bonding, eliminating the need for permanent gaps that would allow moisture ingress while maintaining assembly flexibility during manufacturing.
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 approach enhances manufacturing efficiency, reduces costs, and improves the reliability of touch sensors by eliminating moisture ingress and potential damage from creasing, allowing for faster and more cost-effective production of touch-sensitive systems.
Implementation Method 1
bond pads that are capacitively coupled to one another
Data Source
AI summary
In one embodiment, a system includes a touch sensor comprising a first set of electrodes and a first set of bond pads electrically coupled to the first set of electrodes. The system also includes a second set of bond pads capacitively coupled to the first set of bond pads. Each bond pad of the second set of bond pads is coincident with a bond pad of the first set of bond pads. The system also includes a circuit electrically coupled to the second set of bond pads such that signals may be communicated from the first set of bond pads to the circuit.