Touch Sensor Adhesive Gasket Layout for FPC Bonding Stress
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Solution Overview
Problem
Current touch sensors face challenges in maintaining reliable electrical connections and moisture resistance due to the stress on substrates during bonding processes, which can lead to damage or degradation of conductive materials and adhesive layers.
Innovation Solution
The implementation of a mechanical stack with multiple adhesive layers and a dielectric layer forming a gasket seal around the perimeter of a cover panel, along with a flexible printed circuit (FPC) extending through channels in these layers, provides mechanical support and resistance to moisture ingress, allowing for low-temperature bonding of the FPC to connection pads without damaging the adhesive.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If high-temperature bonding is used to attach the FPC to connection pads, then strong electrical connections are achieved, but the adhesive layers and conductive materials are damaged or degraded
Solution Approach 1:
The patent changes the temperature parameter of the bonding process by introducing a heat-resistant layer that acts as a thermal barrier. This allows the bonding process to occur at controlled temperatures that prevent damage to adhesive layers while still achieving sufficient electrical connection strength through the connection pads.
Solution Approach 2:
The patent introduces a heat-resistant layer as an intermediary between the FPC bonding process and the adhesive layers. This intermediary layer protects the adhesive materials from thermal degradation during bonding, enabling strong electrical connections without compromising adhesive integrity.
2Stability of the object's composition
If the FPC is rigidly bonded to the substrate, then stable electrical connections are achieved, but stress during bonding damages the substrate and conductive materials
Solution Approach 1:
The patent employs a flexible printed circuit (FPC) that can bend and conform to the substrate surface during bonding. This flexibility allows the FPC to accommodate substrate variations and reduce stress concentration, achieving stable electrical connections without damaging the substrate or conductive materials.
Solution Approach 2:
The patent introduces protective layers and design features that cushion against bonding stress before it reaches the substrate and conductive materials. These pre-positioned protective elements absorb and distribute bonding forces, preventing damage while maintaining connection stability.
3Object-affected harmful factors
If adhesive layers are extended to the perimeter for moisture sealing, then moisture resistance is improved, but the bonding process creates more stress concentration points
Solution Approach 1:
The patent applies adhesive layers with different properties at different locations. At the perimeter, adhesive layers are optimized for moisture sealing, while in the bonding regions, the adhesive formulation and thickness are adjusted to minimize stress concentration. This localized optimization achieves both moisture resistance and stress resistance.
Solution Approach 2:
The patent segments the adhesive layer into distinct functional zones: perimeter regions for moisture sealing and central regions for stress distribution during bonding. This segmentation allows each zone to be optimized for its specific function, achieving both moisture protection and stress resistance.
Data Source
AI summary
In one embodiment, an apparatus includes a cover panel. An adhesive layer is coupled to the cover panel. A perimeter of the adhesive layer forms at least a portion of a gasket seal extending substantially perpendicular to an inner surface of the cover panel. An inner surface of the gasket seal defines an edge of a channel. The apparatus also includes a substrate coupled to the adhesive layer. The substrate includes an outer surface having disposed thereon a connection pad region and drive or sense electrodes. The drive or sense electrodes are disposed between the substrate and the cover panel. At least a portion of the channel is disposed between the gasket seal and the connection pad region. The apparatus further includes a flexible printed circuit (FPC) electrically coupled by the connection pad region to the drive or sense electrodes. A first portion of the FPC extends through the channel.