Segmented Pressure Sensor for Display Devices
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Solution Overview
Problem
In the manufacture of display devices, pressure sensors are often damaged by lasers used to melt frit for bonding glass layers, and the presence of an air gap required for capacitance-based sensors limits the thickness of the final device.
Innovation Solution
A pressure sensor configuration with a reference ground layer and sensing pad positioned between the display substrate and window substrate, utilizing a compressible adhesive compression region to change the distance between the reference ground and sensing pad, and a sensing pad divided into sub-regions with gaps to allow laser penetration and minimize damage from the laser.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If pressure sensors are positioned in the area of the frit layer for detection purposes, then pressure sensing capability is improved, but the laser used to melt the frit damages the pressure sensor and electrical traces
Solution Approach 1:
The sensing pad is divided into multiple sub-regions that are spaced apart from each other. This segmentation allows the laser to pass through the gaps between sub-regions to melt the frit layer, while the sub-regions themselves provide sufficient area for capacitance-based pressure sensing. The segmented structure thus enables both pressure detection and laser penetration through the same location.
Solution Approach 2:
Different regions of the sensing pad structure are assigned different functions: the sub-regions provide sensing capability while the gaps between them allow laser transmission. This local differentiation of quality (sensing vs. transparency) within the same component resolves the contradiction between needing sensor presence and allowing laser passage.
2Area of stationary object
If the sensing pad is made solid to improve sensing area, then pressure detection is improved, but the laser cannot penetrate through to melt the frit
Solution Approach 1:
The sensing pad is divided into multiple sub-regions with gaps between them. This segmentation maintains sufficient total sensing area while creating pathways for laser penetration through the gaps, thus resolving the contradiction between sensing area and laser transparency.
3Adaptability or versatility
If an air gap is introduced below the display substrate to enable capacitance-based pressure sensing, then pressure sensing functionality is improved, but the integrated height of the display increases
Solution Approach 1:
Instead of creating an air gap below the display substrate (adding height in the vertical dimension), the patent positions the pressure sensing components (sensing pad and reference ground) within the existing planar structure between the display substrate and window substrate. This shifts the sensing mechanism from a vertical air-gap configuration to a lateral capacitive configuration, maintaining thin profile while enabling pressure sensing.
4Measurement precision
If the sensing pad is positioned to overlap the frit layer for effective pressure detection, then sensing capability is improved, but the pressure sensor blocks the laser from melting the frit
Solution Approach 1:
The sensing pad is segmented into sub-regions with gaps between them, allowing the laser to pass through while maintaining sufficient sensing area. This resolves the blocking issue while preserving detection capability.
Solution Approach 2:
The gaps in the segmented sensing pad, which might seem to reduce sensing area, actually provide the beneficial effect of allowing laser penetration. The harmful blocking effect is converted into a beneficial transparent pathway for the laser while retaining sufficient sensing capability.
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
Enables effective detection of pressure applied to the display substrate without an air gap, allowing for thinner device manufacturing and reducing damage to electrical traces.
Implementation Method 1
capacitance-based pressure sensors often require an air gap below a display substrate so that a distance between a reference ground and a sensing pad can be changed
Implementation Method 2
The compression region can be compressed so as to change a distance between the reference ground layer and the sensing pad
Implementation Method 3
The frit is often melted with a laser that is passed over the frit near the edges of the display
Implementation Method 4
The frit is a ceramic composition that, when heated, melts to hermetically bind the glass pieces
Data Source
AI summary
Technologies are described for pressure sensors used in display devices. In one embodiment, a reference ground layer and sensing pad can be positioned between a display substrate and a window substrate. Additionally, a compression region can be positioned between the display substrate and the window substrate. The compression region can be compressed so as to change a distance between the reference ground layer and the sensing pad. By placing the compression region between the window substrate and the display substrate, the air gap below the display substrate can be removed. In still another embodiment, the sensing pad is aligned over a frit layer, but it is divided into spaced-apart sub-regions that are serially coupled together. Gaps between the sub-regions are sized such that the laser can adequately penetrate through the sensor pad to melt the frit.