Display Pad Electrode Dummy Metal Layer Crack Prevention
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Solution Overview
Problem
Display devices face issues with corrosion and disconnection of wirings due to cracks in the insulating layer, which can occur during the misalignment of pad electrodes and bumps in the driving chip mounting process, leading to potential electrical failures.
Innovation Solution
A display device design featuring a pad electrode unit with a first metal layer, a second metal layer, and a dummy metal layer, where the terminals are arranged in zigzag patterns, and the dummy metal layer is positioned between the terminal and the second metal layer or on top of the insulating layer, preventing direct pressure on the insulating layer and thus minimizing the risk of cracks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the pad electrode and bump are aligned during mounting, then electrical connection is achieved, but misalignment causes cracks in the insulating layer leading to wiring corrosion and disconnection
Solution Approach 1:
The patent introduces a dummy metal layer as an intermediary element between the pad electrode and the bump. This dummy metal layer absorbs misalignment stress and prevents direct transmission of force to the insulating layer, thereby preventing cracks while maintaining electrical connection reliability through the second metal layer that contacts the terminal.
Solution Approach 2:
The dummy metal layer is positioned beforehand in the mounting structure to cushion and absorb potential misalignment forces before they can reach the insulating layer. This preventive cushioning mechanism protects the insulating layer from cracks even when alignment is not perfect during the bump bonding process.
2Reliability
If the second metal layer directly contacts the terminal through via holes, then electrical connection is established, but pressure during mounting can crack the insulating layer covering the wiring
Solution Approach 1:
The dummy metal layer serves as a mediator between the second metal layer and the terminal area. It provides an alternative path for stress distribution and prevents direct pressure transmission to the insulating layer covering the wiring, while still allowing electrical connection through the via holes to the terminal.
Solution Approach 2:
The patent segments the metal layer structure into multiple functional layers: the first metal layer with terminals, the dummy metal layer for stress absorption, and the second metal layer for electrical connection. This segmentation allows each layer to perform its specific function independently, protecting the insulating layer while maintaining connectivity.
3Ease of manufacture
If a simple pad electrode structure is used, then manufacturing is easier, but misalignment during mounting causes insulating layer cracks and wiring failure
Solution Approach 1:
The pad electrode structure is segmented into three distinct metal layers with specific functions: the first metal layer for terminal formation, the dummy metal layer for stress protection, and the second metal layer for electrical connection. This segmentation maintains manufacturing feasibility while significantly improving wiring connection durability through the protective dummy layer.
Solution Approach 2:
The dummy metal layer is strategically positioned only in specific areas where misalignment stress is most likely to occur, providing localized protection to the insulating layer. This local quality enhancement maintains ease of manufacture while improving reliability at critical stress points.
Data Source
AI summary
A display device is disclosed. In one aspect, the device includes a substrate including a display area and a non-display area and a pad electrode unit formed in the non-display area. The pad electrode unit includes a plurality of first metal layers respectively including a plurality of terminals arranged in substantially parallel to each other and a plurality of wirings extending from the terminals and covered by an insulating layer. The pad electrode unit also includes a plurality of second metal layers formed over the insulating layer and connected to the terminals. The pad electrode unit further includes a plurality of dummy metal layers formed between the terminals and the second metal layers or on the top of the insulating layer covering the wirings.