Fingerprint Recognizable Touch Sensor Bonding Pad Arrangement
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Solution Overview
Problem
The demand for large area touch sensors requires a printed circuit board with a narrow pitch between bonding pads to reduce the defect rate and prevent short circuits, while maintaining high transmittance and durability.
Innovation Solution
A touch sensor design featuring a printed circuit board with a bonding pad arrangement that includes alternately arranged first and second bonding pads, extension pads, and vias filled with conductive material, allowing for a separation distance of 15 μm to 35 μm between adjacent bonding pads, and utilizing an anisotropic conductive film layer for electrical connection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the pitch between bonding pads is reduced to accommodate large area touch sensors, then the number of bonding pads can be increased within limited space, but the risk of short circuits and manufacturing defects increases
Solution Approach 1:
The patent transitions from a conventional single-plane bonding pad arrangement to a three-dimensional stacked configuration. First bonding pads are arranged on a first plane of the substrate, while second bonding pads are arranged on a second plane at a different height level. This vertical dimensionality change allows bonding pads to be densely packed without increasing the risk of short circuits, as the stacked arrangement naturally provides electrical isolation between adjacent pads on different planes.
Solution Approach 2:
The patent introduces via holes as intermediary conductive structures that connect bonding pads on different planes. These via holes are filled with conductive material and selectively positioned to establish electrical connections only where required. The intermediary via holes enable the multi-plane bonding pad structure to function as a unified electrical network while maintaining isolation between non-connected pads, thus preventing short circuits.
2Area of stationary object
If the pitch between bonding pads is reduced to fit more pads in limited space, then large area touch sensors can be manufactured, but manufacturing precision requirements increase
Solution Approach 1:
By arranging bonding pads on multiple planes at different height levels, the patent effectively increases the functional area available for bonding pad placement without requiring proportional increases in lateral precision. The vertical separation provides an additional degree of freedom for alignment, reducing the stringency of lateral positioning requirements while still achieving high-density pad configurations for large area touch sensors.
3Area of stationary object
If bonding pads are arranged in a compact configuration to reduce pitch, then space utilization improves, but the complexity of the bonding structure increases
Solution Approach 1:
The patent segments the bonding pad structure into distinct functional groups: first bonding pads on a first plane, second bonding pads on a second plane, and via holes as connecting elements. This segmentation allows each component to be independently designed and optimized. The modular stacked configuration simplifies the overall structure compared to attempting to arrange all bonding pads on a single plane, as it separates electrical connection functions into discrete vertical pathways through the via holes.
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 design enables the production of large area touch sensors with reduced defect rates and prevents short circuits, while maintaining high transmittance and durability, supporting multi-touch capabilities and fingerprint recognition.
Implementation Method 1
utilizing an anisotropic conductive film layer for electrical connection
Implementation Method 2
vias filled with conductive material
Data Source
AI summary
A touch sensor may include: a touch panel including a plurality of electrodes and a plurality of electrode pads respectively connected to the plurality of electrodes; a bonding layer disposed on and in contact with the plurality of electrode pads; and a printed circuit board including: an insulating layer including a first surface adjacent to the bonding layer and a second surface facing the first surface; a plurality of first bonding pads provided in a first region of the first surface of the insulating layer; a plurality of second bonding pads disposed on the second surface of the insulating layer; and a plurality of extension pads disposed on a second region different from the first region of the first surface of the insulating layer and respectively connected to the plurality of second bonding pads.