Pixel Connection Electrode Structure for Reliable IMC Bonding
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Solution Overview
Problem
The formation of uniform intermetallic compound (IMC) alloys for pixel connection electrodes in display devices is challenging due to varying melting points and etching rates, leading to process difficulties and unreliable bonding between pixel electrodes and light emitting elements.
Innovation Solution
A display device design featuring pixel connection electrodes with a main layer made of an IMC alloy and a surrounding sub-layer of a different material, where the main layer is an alloy of a high melting point metallic material and a low melting point material, and the sub-layer is made of the high melting point material, with barrier layers of titanium, reducing the need for patterning the IMC alloy and enhancing bonding reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an IMC alloy is used for the pixel connection electrode to ensure reliable bonding, then bonding reliability is improved, but the process complexity increases due to difficulty in forming uniform alloys and patterning
Solution Approach 1:
The pixel connection electrode is divided into two distinct layers: a first layer made of a single metallic material (e.g., Au, Ag, or Cu) and a second layer made of an IMC alloy. This segmentation allows the first layer to provide reliable bonding through simple patterning, while the second layer provides the IMC alloy properties for bond strength, thereby resolving the contradiction between bonding reliability and process complexity.
2Reliability
If a uniform IMC alloy is formed for pixel connection electrodes, then bonding reliability is improved, but manufacturing precision deteriorates due to varying mixing ratios and etching rates
Solution Approach 1:
By separating the pixel connection electrode into a first layer (single material) and a second layer (IMC alloy), the patent enables precise patterning of the first layer using conventional photolithography, while the second layer is formed after patterning to avoid etching issues. This resolves the manufacturing precision problem while maintaining bonding reliability through the IMC alloy's presence.
Solution Approach 2:
The first layer is formed and patterned before the second layer is deposited. This preliminary action allows the single-material first layer to be precisely patterned without the complications of IMC alloy etching, and subsequently, the IMC alloy second layer is formed to provide the necessary bonding properties, thus resolving both precision and reliability requirements.
3Reliability
If the pixel connection electrode thickness is increased to ensure bonding reliability, then bonding strength is improved, but the process difficulty increases
Solution Approach 1:
The pixel connection electrode is segmented into a first layer and a second layer, where the first layer provides the bonding interface with the pixel electrode and light emitting element, and the second layer provides additional bond strength through IMC alloy properties. This segmentation allows achieving bonding reliability without excessively increasing the total thickness, thereby reducing process difficulty compared to forming a single thick IMC alloy layer.
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 simplifies the process of preparing pixel connection electrodes, improves luminance by allowing wider light emitting elements, and reduces process complexity while ensuring secure bonding.
Implementation Method 1
an intermetallic compound (IMC) alloy in which a metallic material having a relatively low melting point is infiltrated, in a molten state, into a metallic material having a relatively high melting point
Data Source
AI summary
A display device includes: a circuit board including a plurality of pixel drivers respectively corresponding to a plurality of emission areas; a plurality of pixel electrodes on the circuit board and respectively corresponding to the plurality of emission areas; a plurality of pixel connection electrodes respectively on the plurality of pixel electrodes, each of the plurality of pixel connection electrodes including: a main layer on each of the plurality of pixel electrodes; and a sub-layer surrounding a part of a side surface of the main layer adjacent to a top surface of the main layer and including a material different from a material of the main layer; and a plurality of light emitting elements respectively on the plurality of pixel connection electrodes.