Plasma-Activated μLED Bonding With Localized Laser Heating
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional methods for bonding millions of light-emitting diodes (LEDs) to backplanes in display devices result in adverse thermal effects, increasing manufacturing costs and time, and decreasing yield due to thermal expansion mismatches between LEDs and backplanes.
Innovation Solution
A method involving plasma activation and laser-induced heating to form mechanical and electrical couplings between LEDs and backplanes, using pulsed photon beams to control thermal effects and achieve precise bonding, with insulating layers and underfill materials to stabilize the alignment and reduce thermal stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional bonding methods are used to bond millions of LEDs to backplanes, then the bonding process can be completed, but adverse thermal effects occur including thermal expansion mismatches that cause misalignment and damage
Solution Approach 1:
The patent applies different properties to different parts of the bonding system: the backplane is designed with high thermal conductivity to rapidly conduct heat away from bonding locations, while the bonding agent is selected with specific thermal expansion properties that match the LED materials. This local differentiation of thermal properties enables high-speed bonding without the adverse thermal effects that would occur with uniform material properties throughout the system.
Solution Approach 2:
The patent changes the thermal parameters of the bonding system by selecting materials with specific thermal conductivity and thermal expansion coefficients. The backplane material is chosen to have high thermal conductivity to rapidly dissipate heat, while the bonding agent is selected to have thermal expansion properties that match the LED materials, preventing misalignment during the bonding process.
2Reliability
If conventional bonding methods are used, then bonding can be achieved, but manufacturing cost and time increase
Solution Approach 1:
The patent performs preliminary actions by pre-heating the bonding agent to optimal bonding temperature before the actual bonding operation, and by pre-positioning LEDs with precise alignment features that enable rapid pickup and placement. The backplane is also pre-prepared with corresponding alignment structures. These preliminary actions ensure that when bonding occurs, it can be completed quickly and reliably without requiring lengthy heating or alignment procedures during the main bonding cycle.
Solution Approach 2:
The patent replaces conventional thermal bonding mechanisms with a more efficient system that uses controlled localized heating combined with rapid mechanical pickup and placement. Instead of heating entire batches of LEDs and backplanes uniformly over extended periods, the system uses localized energy delivery combined with precise mechanical positioning to achieve bonding in much shorter cycles while maintaining high reliability.
3Productivity
If conventional bonding methods are used, then bonding can be completed, but yield decreases due to thermal expansion mismatches
Solution Approach 1:
The patent addresses thermal expansion mismatches by applying different thermal properties to different components: the backplane uses high thermal conductivity material to rapidly conduct heat away from bonding zones, while the bonding agent is specifically selected to have thermal expansion coefficients that match the LED materials. This local differentiation prevents the misalignment and bonding failures that would occur with uniform material properties, thereby maintaining high yield during high-speed bonding operations.
Solution Approach 2:
The patent employs composite material strategies by combining materials with complementary thermal properties in the bonding system. The backplane may use composite structures that provide both high thermal conductivity for heat dissipation and appropriate mechanical properties for structural support. The bonding agent itself may be a composite formulation that achieves optimal thermal expansion matching while maintaining appropriate bonding strength and electrical properties.
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 method effectively reduces adverse thermal effects, enhances the mechanical and electrical integrity of the bonds, and increases the efficiency and precision of the bonding process, allowing for the assembly of large arrays of LEDs without misalignment or damage.
Implementation Method 1
exposing the first insulating layer and the second insulating layer to a plasma that activates each of the first insulating layer and the second insulating layer
Implementation Method 2
electrically bonding the exposed distal portion of the second contact to the adjacent distal portion of the first contact via inducing thermal energy with associated thermal effects that are localized to the first and second contacts
Data Source
Figure 1A~1B
Figure 2A
Figure 2B
AI summary
The invention is directed towards enhanced systems and methods for employing a pulsed photon (or EM energy) source, such as but not limited to a laser, to electrically couple, bond, and/or affix the electrical contacts of a semiconductor device to the electrical contacts of another semiconductor devices. Full or partial rows of LEDs are electrically coupled, bonded, and/or affixed to a backplane of a display device. The LEDs may be μLEDs. The pulsed photon source is employed to irradiate the LEDs with scanning photon pulses. The EM radiation is absorbed by either the surfaces, bulk, substrate, the electrical contacts of the LED, and/or electrical contacts of the backplane to generate thermal energy that induces the bonding between the electrical contacts of the LEDs' electrical contacts and backplane's electrical contacts. The temporal and spatial profiles of the photon pulses, as well as a pulsing frequency and a scanning frequency of the photon source, are selected to control for adverse thermal effects.