μLED Backplane Bonding With Pulsed Laser Thermal Control
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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 the use of pulsed laser technology to selectively bond LEDs to a target substrate, where the temporal and spatial profiles of photon pulses are modulated to control thermal effects, allowing for precise and efficient electrical coupling while minimizing thermal impact on the LEDs and backplane.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional bonding methods are used to bond LEDs to backplanes, then bonding can be achieved, but adverse thermal effects occur due to thermal expansion mismatches
Solution Approach 1:
The patent introduces a multi-stage curing process with controlled temperature parameters. The underfill material is first cured at a low temperature (e.g., 50-100°C) to establish mechanical support, then subsequently cured at a higher temperature (e.g., 150-200°C) to achieve full bonding. This staged parameter change allows bonding to proceed while minimizing thermal expansion mismatches that would occur with conventional single-stage high-temperature bonding.
Solution Approach 2:
The underfill material is applied and partially cured before the actual LED-to-backplane bonding process. This preliminary action creates a mechanical support structure that stabilizes the assembly during subsequent bonding operations, preventing thermal expansion mismatches from causing misalignment or bonding failures.
2Reliability
If conventional bonding methods are used, then LEDs can be bonded to backplanes, but manufacturing time and cost increase
Solution Approach 1:
The underfill material is pre-applied to either the backplane or LED array before the bonding process. This preliminary action eliminates the need for separate underfill application steps during manufacturing, reducing overall process time while ensuring proper positioning and support during bonding.
Solution Approach 2:
The multi-stage curing process allows different portions of the assembly to be cured at different times and temperatures. The first stage provides immediate mechanical support at low temperature, while the second stage completes bonding. This parameter optimization reduces total manufacturing time compared to conventional single-stage high-temperature bonding that requires longer processing to avoid defects.
3Productivity
If conventional bonding methods are used, then LEDs can be bonded to backplanes, but yield decreases due to thermal expansion mismatches
Solution Approach 1:
The staged curing process with controlled temperature parameters minimizes thermal expansion mismatches. The first curing stage at low temperature (50-100°C) establishes mechanical support with minimal thermal stress, while the second stage at higher temperature (150-200°C) completes bonding. This parameter optimization significantly reduces bonding defects and improves manufacturing yield.
Solution Approach 2:
The underfill material is pre-applied and partially cured to create a stable mechanical support structure before final bonding. This preliminary action prevents thermal expansion mismatches from causing misalignment or bonding failures during the heating process, thereby improving yield.
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 approach reduces adverse thermal effects, ensures accurate alignment and bonding of LEDs, and enhances the mechanical and electrical integrity of the bonds, thereby improving manufacturing efficiency and reducing defects in display devices.
Implementation Method 1
applying first thermal energy to the uncured UF material to pre-cure the uncured UF material
Implementation Method 2
irradiating an excess portion of the pre-cured UF material with a first photon beam to remove the excess portion
Implementation Method 3
bonding the at least partially exposed distal portion of the second electrical contact to the adjacent distal portion of the first electrical contact is induced by second thermal energy generated by a second photon beam irradiating at least one of the semiconductor device or the target substrate
Implementation Method 4
curing the pre-cured UF material
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.