Micro LED Display Module Bonding and Light Isolation Structure
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Solution Overview
Problem
The electrical connection and bonding between inorganic light emitting elements and substrates in micro LED display panels are unstable, leading to potential material waste and increased costs due to uneven distribution and excess conductive balls in anisotropic conductive films, as well as light interference between sub-pixels.
Innovation Solution
A display module design featuring a substrate with pad electrodes, inorganic light emitting elements with contact electrodes connected via bumps, a reflective member underfilled with grey resin and reflective beads to enhance bonding and light efficiency, and a black cover member to reduce light interference, along with a manufacturing method involving reflow, UV curing, and heat treatment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If inorganic LEDs are made very small to achieve high resolution, then display resolution is improved, but electrical connection stability between electrodes deteriorates
Solution Approach 1:
The electrical connection structure is segmented into multiple functional layers: pad electrode, bump structure (with conductive ball and solder layer), and bridge structure. This segmentation allows each component to be optimized independently - the bump provides mechanical bonding while the bridge extends the electrical connection path, collectively improving reliability without compromising the small size of the inorganic LEDs
Solution Approach 2:
The bridge structure acts as an intermediary element between the bump and the pad electrode. It extends the electrical connection path and provides additional bonding area, mediating the connection between the small contact electrode and the larger pad electrode, thereby improving electrical connection stability while maintaining the compact design
2Ease of manufacture
If inorganic light emitting elements are bonded to substrate, then display panel assembly is achieved, but bonding stability deteriorates due to small size
Solution Approach 1:
The bonding interface is segmented into multiple bonding regions: the bump bonding area and the bridge bonding area. This segmentation distributes the bonding stress across multiple points and increases the total bonding area, thereby improving bonding stability while maintaining the small size of the inorganic light emitting elements
Solution Approach 2:
The bonding structure uses composite materials including the bump (with conductive ball and solder layer) and the bridge structure (with conductive material). This composite approach combines different material properties to achieve both mechanical bonding strength and electrical conductivity, improving bonding stability without compromising ease of manufacture
3Reliability
If anisotropic conductive film is used for connection, then electrical connection is achieved, but material cost increases due to excess conductive balls
Solution Approach 1:
The design extracts only the necessary conductive elements (single conductive ball in the bump) rather than using a dense array of conductive balls as in anisotropic conductive films. This extraction approach maintains electrical connection reliability while significantly reducing the quantity of conductive material required, thereby lowering material costs
Solution Approach 2:
The conductive material is concentrated locally in the bump structure where it is most needed for electrical connection, rather than being distributed uniformly across the entire connection area. This local concentration approach improves connection reliability while reducing overall material usage and cost
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
Stabilizes electrical connections, enhances bonding between inorganic light emitting elements and substrates, improves light efficiency by reducing light absorption, and minimizes material costs by optimizing the distribution and usage of conductive materials.
Implementation Method 1
a reflective member configured to underfill the inorganic light emitting element to cover side surfaces of the inorganic light emitting element and a bottom surface of the inorganic light emitting element, and configured to reflect light
Implementation Method 2
a cover member configured to cover side surfaces of the reflective member and the mounting surface of the substrate, the cover member having a black color
Implementation Method 3
wherein the reflective member is formed by dispensing a resin onto the substrate
Implementation Method 4
along with a manufacturing method involving reflow, UV curing, and heat treatment
Data Source
AI summary
A display module includes: a substrate including a mounting surface and a pad electrode on the mounting surface; an inorganic light emitting element including a contact electrode corresponding to the pad electrode; a bump disposed between the pad electrode and the contact electrode to bond the pad electrode and the contact electrode, the bump being electrically connecting the pad electrode to the contact electrode; a reflective member configured to underfill the inorganic light emitting element to cover side surfaces of the inorganic light emitting element and a bottom surface of the inorganic light emitting element, and configured to reflect light; and a cover member configured to cover side surfaces of the reflective member and the mounting surface of the substrate, the cover member having a black color.