LED Flat Bonding Reflow With Press Plate Alignment
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Solution Overview
Problem
The challenge in bonding large numbers of light emitting diodes (LEDs) to a circuit board is that uneven solder application and temperature differences can cause inclined upper surfaces, leading to color irregularities in display images, making it difficult to achieve uniform light emission and repair individual LEDs.
Innovation Solution
A flat bonding method using a reflow process and a press plate to re-bond LEDs on a circuit board, where the press plate changes the direction of the upper surfaces and applies heat to melt the metal bonding layer, ensuring even alignment and elevation of LEDs, thereby preventing color irregularities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a large number of light emitting devices are bonded to a circuit board, then the display apparatus can achieve high resolution and complete images, but the upper surfaces of the bonded devices become inclined due to solder application variations and temperature differences
Solution Approach 1:
The patent applies preliminary action by performing a reflow process before final bonding to pre-adjust the positions and orientations of light emitting devices. This preliminary heating and reflow step allows devices to self-align and settle into proper orientations before the final bonding process, preventing inclination issues that would otherwise require individual correction later.
Solution Approach 2:
The patent replaces manual or mechanical adjustment methods with a thermal reflow process. Instead of mechanically positioning each device to ensure flatness, the invention uses controlled heating to melt the solder, allowing devices to self-align through capillary action and thermal expansion, thereby achieving uniform flatness across thousands of devices without mechanical intervention.
2Reliability
If individual light emitting devices with inclined surfaces are repaired, then color irregularities can be corrected, but the repair process becomes extremely difficult and time-consuming when large numbers of devices are involved
Solution Approach 1:
The reflow process serves as a preliminary correction step that prevents the need for individual repairs later. By addressing potential inclination issues during the initial bonding process through controlled reheating and reflow, the system ensures all devices are properly aligned before final placement, eliminating the need for difficult post-bonding repairs.
Solution Approach 2:
The light emitting devices self-correct their orientations during the reflow process through physical phenomena such as surface tension of molten solder and thermal expansion. The devices automatically align themselves to the circuit board without external intervention, making the system self-correcting and eliminating the need for manual repair operations.
3Manufacturing precision
If precise control of solder amount and temperature is maintained, then upper surfaces remain flat, but the bonding process becomes more complex and difficult to implement
Solution Approach 1:
The patent changes the parameters of the bonding process by implementing a two-stage thermal approach: an initial reflow stage with controlled heating to melt and reflow the solder, followed by a final bonding stage. This parameter change allows the system to achieve flatness through the physics of reflow rather than through precise control of solder application, simplifying the overall process control requirements.
Solution Approach 2:
The invention substitutes precise mechanical control of solder application with a thermal field approach. Instead of requiring precise mechanical dispensing of solder and temperature control during bonding, the system uses a reflow process where thermal energy melts the solder and allows it to redistribute and self-level, replacing complex mechanical precision requirements with simpler thermal processing.
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 ensures that at least 50% of the LEDs have an angular difference of less than 5 degrees and elevation deviation of about 2 μm, resulting in uniform light emission and preventing color defects in display panels.
Implementation Method 1
The press plate may apply heat to the light emitting devices to melt at least the portion of the metal bonding layer.
Implementation Method 2
at least a portion of the metal bonding layer may be melted during the re-bonding process
Implementation Method 3
bonding light emitting devices on a circuit board using a reflow process
Data Source
AI summary
A flat bonding method of light emitting devices including bonding light emitting devices on a circuit board using a reflow process, and re-bonding at least a portion of the light emitting devices bonded on the circuit board using a press plate while pressing the portion of the light emitting devices.