Pad Electrode Structure Crack Prevention in OLED Displays
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Solution Overview
Problem
The existing pad electrode structures in organic light-emitting display (OLED) apparatuses are prone to damage and corrosion when a printed circuit board is attached and removed, leading to reliability issues due to cracks in the conductive barrier layer, which can propagate to the pad electrode and affect other wirings.
Innovation Solution
A pad electrode structure is designed with an interlayer insulating layer having convex portions and a conductive barrier layer made of materials like indium tin oxide, with a planarization insulating layer covering the edges and filling openings, preventing crack propagation and corrosion by isolating the pad electrode from direct contact with the conductive balls.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the pad electrode structure uses a simple conductive barrier layer without additional protective layers, then the manufacturing process is simple, but the conductive barrier layer is prone to damage and corrosion when printed circuit boards are attached and removed
Solution Approach 1:
The protective structure is divided into multiple functional layers: a conductive barrier layer for electrical protection, a planarization insulating layer for mechanical protection and surface flattening, and an interlayer insulating layer with convex portions for crack prevention. This segmentation allows each layer to specialize in protecting against specific failure modes while maintaining overall manufacturing feasibility through standardized layering processes.
Solution Approach 2:
The pad electrode structure employs a composite multi-layer configuration combining conductive materials (indium tin oxide, indium zinc oxide, zinc oxide, indium oxide, indium gallium oxide, or aluminum zinc oxide) for the conductive barrier layer with insulating materials for the planarization and interlayer insulating layers. This composite structure provides both electrical functionality and mechanical protection, preventing crack propagation and corrosion while maintaining conductivity where needed.
2Reliability
If the conductive barrier layer is made thin to maintain good electrical contact, then electrical conductivity is improved, but the layer becomes more susceptible to cracks and damage during board attachment and removal
Solution Approach 1:
The planarization insulating layer is positioned to cover the edges of the conductive barrier layer before any mechanical stress from printed circuit board attachment and removal occurs. This pre-positioned protective layer acts as a cushion that absorbs mechanical stress and prevents it from reaching the thin conductive barrier layer, thereby preventing crack initiation and propagation while allowing the conductive layer to remain thin for optimal electrical contact.
Solution Approach 2:
The planarization insulating layer serves as an intermediary between the thin conductive barrier layer and the external mechanical stresses from printed circuit boards. This intermediate layer transfers and distributes mechanical loads away from the fragile conductive barrier layer, protecting it from direct stress while maintaining the thin profile needed for good electrical conductivity.
3Reliability
If the pad electrode structure includes multiple protective layers to prevent crack propagation, then reliability is improved, but the manufacturing process becomes more complex
Solution Approach 1:
The interlayer insulating layer features convex portions positioned specifically between the openings where the conductive barrier layer is most vulnerable to crack propagation. This localized structural modification provides targeted protection exactly where needed without adding complexity to the entire structure. The convex portions act as stress distribution elements that prevent crack propagation locally at critical points while maintaining overall structural simplicity.
4Reliability
If the planarization insulating layer completely covers the conductive barrier layer, then protection is maximized, but access to the pad electrode for electrical connection is blocked
Solution Approach 1:
The planarization insulating layer is segmented with openings that align with the pad electrode contact regions. This segmentation allows the layer to provide comprehensive protection over most of the conductive barrier layer while maintaining controlled access points for electrical connections. The openings are strategically positioned to enable printed circuit board contact pads to reach through and establish electrical connection with the underlying pad electrode structure.
Data Source
AI summary
An organic light-emitting display apparatus includes a pad electrode structure having excellent reliability due to the prevention of propagation of a crack to the pad electrode. The organic light-emitting display apparatus includes further an interlayer insulating layer on the pad electrode, a conductive barrier layer, and a planarization insulating layer. The interlayer insulating layer includes a plurality of openings that expose an upper surface of the pad electrode. The conductive barrier layer is on the plurality of openings and the interlayer insulating layer. The planarization insulating layer covers an edge of the conductive barrier layer. The planarization insulating layer is in the openings and covers an edge of the conductive barrier layer. An upper portion of the planarization insulating layer may be substantially planar with an upper portion of the conductive barrier layer on convex portions of the interlayer insulating layer.