Stepped Display Pad Electrode for Low-Resistance Ultrasonic Bonding
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Solution Overview
Problem
Conventional display devices face increased electrical resistance and potential physical damage due to the use of anisotropic conductive films for coupling external devices to pad electrodes, which can lead to inefficiencies in data transmission and reliability issues during ultrasonic bonding.
Innovation Solution
A display device design where a pad electrode is directly bonded to a bump of an external device using an ultrasonic bonding method, with a reduced area of the protruding portion of the pad electrode to minimize physical damage and energy requirements, and an insulating pattern is used to facilitate electrical connection between the pad electrodes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an anisotropic conductive film is used to couple the external device to the pad electrode, then the electrical connection is established, but the electrical resistance is significantly increased
Solution Approach 1:
The invention extracts and removes the anisotropic conductive film from the bonding interface between the pad electrode and the external device bump. By eliminating this intermediate layer, the patent achieves direct metal-to-metal contact, thereby significantly reducing electrical resistance while maintaining reliable electrical connection through the ultrasonic bonding process.
Solution Approach 2:
The invention introduces a new intermediary approach by using ultrasonic vibration energy as the bonding mechanism instead of relying on the anisotropic conductive film. The ultrasonic bonding process creates direct metallurgical bonding between the pad electrode and bump, serving as a more efficient intermediary for electrical connection than the conventional conductive film.
2Strength
If ultrasonic bonding is applied between the external device and the display panel, then direct bonding is achieved, but physical damage may occur due to high bonding energy
Solution Approach 1:
The invention applies local quality by creating a non-uniform pad electrode structure with different thickness regions. The first region has a greater thickness than the second region, allowing the ultrasonic bonding energy to be concentrated in the thicker first region while the thinner second region experiences reduced energy exposure. This spatial variation in thickness protects the external device from excessive bonding energy while maintaining strong bonding in the critical connection area.
Solution Approach 2:
The pad electrode is segmented into multiple regions with different thicknesses - a first region for primary bonding and a second region for protection. This segmentation allows the bonding process to be distributed across different zones, with the thicker first region absorbing the majority of ultrasonic energy and the thinner second region providing protection against damage to the external device.
3Object-affected harmful factors
If the pad electrode area is reduced to minimize bonding energy, then physical damage is minimized, but electrical connection area is reduced
Solution Approach 1:
The invention uses local quality by creating spatial variation in pad electrode thickness rather than uniformly reducing the entire pad electrode area. The first region maintains greater thickness to provide sufficient electrical connection area and conductivity, while the second region has reduced thickness to minimize bonding energy exposure. This localized differentiation allows simultaneous optimization of both electrical connection reliability and damage protection.
Solution Approach 2:
The invention transitions from a two-dimensional area reduction approach to a three-dimensional thickness variation approach. Instead of simply reducing the pad electrode's planar area, the patent utilizes the thickness dimension to control bonding energy distribution. The thicker first region provides both electrical connectivity and energy absorption, while the thinner second region protects against damage, effectively using the third dimension to resolve the contradiction.
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 reduces electrical resistance and minimizes physical damage during bonding, ensuring reliable and efficient data transmission between the external device and the display panel while maintaining structural integrity.
Implementation Method 1
a pad electrode is directly bonded to a bump of an external device through an ultrasonic bonding method
Data Source
AI summary
A display device includes a substrate including an active area having pixels and a non-active area including a pad region. A pad electrode is disposed in the pad region and includes a first pad electrode and a second pad electrode disposed on the first pad electrode. A first insulating pattern is interposed between the first and second pad electrodes. In a plan view, the first insulating pattern is positioned inside the first pad electrode, and a portion of the second pad electrode overlapping the first insulating pattern protrudes further from the substrate in a thickness direction than a portion of the second pad electrode not overlapping the first insulating pattern. The second pad electrode directly contacts a portion of the upper surface of the first pad electrode. In a plan view, an area of the second pad electrode is greater than an area of the first pad electrode.