LCD Common Pad Contact Hole Positioning for Sealant Height Uniformity
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Solution Overview
Problem
In liquid crystal displays (LCDs), the height difference of conductive sealants between the inner and outer positions leads to contact deterioration between the common pad and common electrode, and gap deterioration between the substrates, due to overlapping of conductive sealants with contact holes.
Innovation Solution
The implementation of a design where the common contact holes are positioned between the conductive sealant and the display area, with assistance common pads and conductive sealants that include conductive balls, ensuring uniform intervals and preventing overlap, thereby minimizing height differences and maintaining electrical connectivity without signal distortion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the conductive sealant overlaps the contact hole to connect common pad and common electrode, then electrical connectivity is achieved, but a height difference occurs between conductive sealants inside and outside the contact hole causing contact deterioration and gap deterioration
Solution Approach 1:
The conductive sealant is divided into multiple segments: a first conductive sealant outside the contact hole, a second conductive sealant inside the contact hole, and a third conductive sealant connecting them. This segmentation allows each part to perform its specific function while maintaining overall height uniformity and electrical connectivity.
Solution Approach 2:
The third conductive sealant acts as an intermediary element that bridges the first and second conductive sealants. It fills the height difference created by the contact hole overlap and provides a gradual transition, preventing both contact deterioration and gap deterioration while maintaining electrical connectivity.
2Reliability
If the conductive sealant is made taller to bridge height differences, then electrical connectivity is improved, but gap deterioration between substrates occurs
Solution Approach 1:
Instead of using a single tall conductive sealant, the connection is segmented into multiple parts at different heights. The first conductive sealant is at a lower height outside the contact hole, the second is at a higher height inside the contact hole, and the third connects them with a gradual height transition, preventing substrate gap deterioration.
Solution Approach 2:
Different regions of the conductive sealant structure have different heights tailored to local requirements. The first conductive sealant has a lower height suitable for the peripheral area, while the second conductive sealant has a higher height to bridge the contact hole, and the third provides a transitional height. This local differentiation maintains both electrical connectivity and substrate gap integrity.
3Ease of manufacture
If the contact hole is positioned to overlap the conductive sealant for direct connection, then manufacturing is simplified, but contact deterioration occurs due to height difference
Solution Approach 1:
The conductive sealant is segmented into multiple parts that can be formed in separate steps or with different materials. This segmentation allows for better control of each segment's position and height, improving contact quality while maintaining manufacturing feasibility through a systematic multi-step process.
Solution Approach 2:
The contact hole is formed in advance in the insulating layer before the conductive sealant is applied. This preliminary action allows for precise positioning and height control of the conductive sealant segments, ensuring proper alignment and contact quality while simplifying the overall manufacturing process through clear sequence definition.
Data Source
AI summary
A liquid crystal display (LCD) includes a first substrate including a display area displaying images and a peripheral area surrounding the display area, a common pad formed in the peripheral area of the first substrate, an insulating layer formed on the common pad and having a common contact hole exposing the common pad, an assistance common pad formed on the insulating layer of the peripheral area and contacting the common pad through the common contact hole, a second substrate corresponding to the first substrate, and a common electrode formed on the second substrate, and a conductive sealant disposed between the assistance common pad and the common electrode of the peripheral area, the conductive sealant electrically connecting the assistance common pad and the common electrode, wherein the common contact hole is disposed between the conductive sealant and the display area.