Display Panel Opening Structure for Micro LED Bonding Reliability
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Solution Overview
Problem
The existing micro LED displays face issues of peeling or cracking between film layers during bonding with the driving backplane due to large concentrated stress and unsolidified or molten metal bumps leading to short circuits.
Innovation Solution
A display panel design featuring a driving backplane with connecting electrodes, an insulating layer having openings with a ridge and furrow profile that increases the contact area between bump electrodes and the sidewall, reducing pressure and stress, and an organic material insulating layer with step surfaces to prevent overflow and short circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If bonding pressure and metal bump size are increased to ensure good contact, then electrical connection reliability is improved, but stress concentration causes peeling or cracking between film layers
Solution Approach 1:
The insulating layer is designed with non-uniform thickness, featuring a first thickness in the opening region and a second thickness in the electrode region. This local quality variation allows the opening region to accommodate bonding stress while the thicker electrode region provides structural support, resolving the contradiction between ensuring good electrical contact and preventing film layer damage.
Solution Approach 2:
The insulating layer acts as a cushioning element that is pre-configured with specific thickness variations. The first thickness region provides stress absorption capacity before bonding occurs, preventing stress concentration from directly transmitting to the film layers during the bonding process, thus protecting against peeling or cracking.
2Reliability
If bonding pressure is increased to ensure contact, then electrical connection is improved, but unsolidified or molten metal bumps may flow and cause short circuits
Solution Approach 1:
The insulating layer has different thicknesses in different regions: a first thickness in the opening region that allows metal bump flow during bonding, and a second thickness in the electrode region that prevents overflow. This local quality differentiation enables the structure to tolerate controlled metal flow while preventing harmful short circuits.
Solution Approach 2:
The insulating layer serves as an intermediary structure between the opening and the electrode region. It mediates the metal bump behavior during bonding by providing a controlled path for metal flow in the opening region while acting as a barrier in the electrode region, thus preventing short circuits without compromising electrical connection.
3Stress or pressure
If the opening area is increased to reduce stress, then stress concentration is reduced, but electrical connection area may be compromised
Solution Approach 1:
The solution moves from a two-dimensional trade-off between opening area and connection area to a three-dimensional solution by varying the insulating layer thickness. The opening region has a first thickness that reduces stress concentration, while the electrode region has a second thickness that maintains electrical connection, effectively adding the thickness dimension to resolve the contradiction.
Solution Approach 2:
Different regions of the insulating layer are assigned different thicknesses optimized for their specific functions: the opening region uses a first thickness optimized for stress distribution, while the electrode region uses a second thickness optimized for electrical connection, eliminating the need to compromise between these competing requirements.
Data Source
AI summary
A display panel is provided. The display panel includes a driving backplane with a connecting electrode, an insulating layer arranged on the connecting electrode, and a light-emitting unit arranged on the driving backplane. The insulating layer includes an opening exposing part of a surface of the connecting electrode. The light-emitting unit is electrically connected with a bump electrode, and the bump electrode is electrically connected with the connecting electrode through the opening. The opening has a ridge and furrow profile, which can increase an area of a sidewall of the opening, such that a contact area between the bump electrode and the sidewall is increased to prevent peeling or cracking between the films.