Unpackaged Micro LED Backlighting for Thin Displays
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Solution Overview
Problem
Conventional semiconductor device fabrication processes result in packaged devices that are bulky, limiting the thickness and efficiency of display technologies like LED-backlit LCDs, as they require thick lenses and significant spacing to manage heat and cost, making it difficult to produce thin, cost-effective, and uniformly reproducible thin displays.
Innovation Solution
A display backlighting apparatus using an array of closely spaced, unpackaged semiconductor dies directly transferred to a circuit substrate, reducing thickness and improving luminescence and contrast ratio, achieved through a machine that precisely positions and affixes micro LEDs onto a substrate, allowing for a more power-efficient and thinner structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If packaged LEDs are used in LED-backlit LCD displays, then the LEDs provide sufficient light output and heat management, but the display thickness increases significantly due to the size of packaged LEDs, thick lenses, and required spacing
Solution Approach 1:
The patent extracts the essential light-emitting function from the packaged LED structure by using only the unpackaged semiconductor die. The packaging, lens, and associated components are removed, retaining only the core LED die that provides light output and heat generation, thereby eliminating the thickness contribution from packaging and lens components.
Solution Approach 2:
The patent changes the physical state and dimensions of the LED component by transitioning from packaged LEDs (with dimensions in millimeters) to unpackaged semiconductor dies (with dimensions in micrometers). This parameter change reduces the LED component size by factors of 10-100 in linear dimensions, enabling display thickness reduction while maintaining functional performance.
2Length of stationary object
If unpackaged semiconductor dies are used directly, then the display thickness is reduced, but it becomes difficult to manufacture thin displays in a cost-effective, uniform, and mass-reproducible manner
Solution Approach 1:
The patent performs preliminary actions by pre-dicing the semiconductor wafer into individual dies and pre-positioning them on a carrier substrate before transfer to the final display substrate. This preliminary preparation enables efficient batch processing and automated handling, making the manufacturing of thin displays cost-effective and uniform despite the complexity of handling unpackaged dies.
Solution Approach 2:
The patent uses a carrier substrate as a temporary copy or intermediate platform to hold and organize multiple unpackaged dies before their final placement. This copying approach allows for standardized handling, testing, and transfer processes that maintain manufacturing uniformity and cost-effectiveness while working with unpackaged semiconductor components.
3Reliability
If packaged LEDs are used, then the dies are protected from environmental degradation, but the overall assembly size increases by 100 times the volume compared to unpackaged dies
Solution Approach 1:
Instead of using rigid packaged enclosures that increase volume by 100 times, the patent employs thin-film encapsulation layers directly on the semiconductor die surface. These thin protective films provide environmental protection while adding minimal thickness, maintaining both reliability and compact form factor.
Solution Approach 2:
The patent transitions from three-dimensional packaged enclosures to two-dimensional thin-film protection on the die surface. This dimensional change protects the semiconductor die from environmental degradation while minimizing the volume increase, as the protection is applied as a surface layer rather than a volumetric enclosure.
Data Source
AI summary
A backlighting apparatus for an LCD display includes a substrate and a circuit trace disposed on a surface of the substrate. The apparatus further includes a plurality of light sources affixed to the substrate via the circuit trace in a predetermined pattern across the surface of the substrate. Each light source includes one or more micro-sized, unpackaged LEDs. A height of the one or more micro-sized, unpackaged LEDs is from about 12 microns to about 200 microns.