Flush Pad Configuration for Silicon OLED Display Substrate Yield
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Solution Overview
Problem
The existing silicon-based OLED display substrates face issues with photoresist residue accumulation at the pad locations during the development process, leading to uneven brightness (twill mura) and decreased product yield due to the formation of pits where the pads are located.
Innovation Solution
The display substrate design includes a pad configuration where the surface of the pad is disposed flush with the surface of the circuit structure layer around the pad and away from the base substrate, eliminating the pit formation and subsequent photoresist residue accumulation, thereby preventing twill mura and improving yield.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the pad is recessed below the circuit structure layer surface, then the bonding connection to external circuit board is enabled, but photoresist residue accumulates at the pad location during development process
Solution Approach 1:
Instead of recessing the pad below the surface, the invention inverts the approach by making the pad surface flush with or slightly protruding from the circuit structure layer surface. This inversion eliminates the pit formation that causes photoresist residue accumulation, while still enabling bonding connection to the external circuit board through the flush surface configuration.
2Object-generated harmful factors
If the pad surface is flush with the circuit structure layer surface, then photoresist residue accumulation is prevented, but bonding connection to external circuit board must be redesigned
Solution Approach 1:
The flush pad surface serves multiple functions: it prevents photoresist residue accumulation during the development process, provides a planar bonding surface for external circuit board connection, and maintains structural integrity with the surrounding circuit structure layer. This multi-functionality eliminates the need for separate pit structures while achieving both development process reliability and bonding connectivity.
3Reliability
If pits are formed at pad locations, then bonding electrode is exposed for connection, but uneven brightness (twill mura) occurs due to photoresist residue
Solution Approach 1:
The invention performs preliminary action by configuring the pad surface to be flush with the circuit structure layer surface before the development process begins. This preliminary configuration prevents the formation of pits that would otherwise trap photoresist residue during development, thereby preventing twill mura and ensuring uniform brightness across the display substrate while still exposing the bonding electrode for connection.
Data Source
AI summary
A display substrate includes a display area and a bonding area located on one side of the display area; the display substrate includes a base substrate and a circuit structure layer disposed on the base substrate; the circuit structure layer of the display area is provided with a pixel driving circuit including multiple transistors, the display area further includes a light emitting structure layer and a package structure layer sequentially stacked on a side of the circuit structure layer away from the base substrate, the light emitting structure layer includes a light emitting device connected to the pixel driving circuit; a pad is provided in the circuit structure layer of the bonding area and configured to be bonded and connected to an external circuit board, a surface of the pad is disposed flush with a surface of the circuit structure layer around the pad and away from the base substrate.