Gang Bonding Process for Matrix Light-Emitting Elements
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Solution Overview
Problem
The existing methods for bonding light-emitting elements onto substrates, such as in display or lighting panels, are limited by the size of packaged LED units, restricting pixel density and requiring lengthy individual bonding processes, which are inefficient and time-consuming.
Innovation Solution
A method involving forming conductive material in a matrix arrangement on substrate bond pads, picking and placing light-emitting elements onto a temporary carrier, and applying heat with compressive force to form conductive joints, enabling gang chip-on-board bonding of a matrix of light-emitting elements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If packaged LED units are used for assembly, then ease of manufacture is improved, but pixel density is limited
Solution Approach 1:
The invention segments the manufacturing process into two distinct stages: first, mounting complete LED packages onto the PCB using conventional SMT techniques, and second, bonding individual LED dice to the package leads. This segmentation allows each stage to optimize for its specific requirement - ease of package handling in stage one, and high precision in stage two - thereby resolving the contradiction between ease of manufacture and pixel density.
Solution Approach 2:
The invention implements a nested structure where LED dice are bonded to the leads of packaged LED units, which themselves are mounted on the PCB. This nesting approach allows the system to combine the benefits of packaged LEDs (ease of manufacture, electrical connectivity) with the advantages of bare dice (small size, high density), effectively increasing pixel density without sacrificing ease of manufacture.
2Manufacturing precision
If individual LED bonding is performed, then pixel density can be increased, but manufacturing time increases
Solution Approach 1:
The invention merges multiple bonding operations into a single gang bonding process. Instead of bonding LED dice to packages one at a time, the apparatus bonds multiple dice simultaneously to multiple package leads in parallel. This merging of operations maintains the high pixel density achieved through individual bonding while dramatically reducing the total manufacturing time, thus resolving the contradiction between pixel density and productivity.
3Productivity
If gang bonding of light-emitting elements is performed, then productivity is improved, but bonding precision may deteriorate
Solution Approach 1:
The invention introduces a temporary carrier as an intermediary between the LED dice and the final PCB substrate. The carrier holds multiple dice in precise positions during the gang bonding process, ensuring accurate alignment with package leads. This intermediary structure enables simultaneous bonding of multiple elements with high precision, resolving the contradiction between productivity and bonding accuracy by decoupling the parallel processing requirement from the precision requirement.
Solution Approach 2:
The invention employs parameter changes in the bonding process, specifically controlling temperature, pressure, and bonding time as variables. By optimizing these parameters for gang bonding conditions, the process achieves both high throughput and precise bonding results. The ability to adjust and control these parameters ensures that simultaneous bonding does not compromise bonding accuracy, thus resolving the contradiction between productivity and manufacturing precision.
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 significantly increases throughput and achieves higher pixel density by allowing simultaneous bonding of thousands of flip-chip LEDs, reducing bonding time and improving accuracy, while maintaining low die tilt and reworkability of solder joints.
Implementation Method 1
applying heat to the light-emitting elements while exerting a compressive force with the bond head against the conductive material so as to form conductive joints
Implementation Method 2
exerting a compressive force with the bond head against the conductive material so as to form conductive joints
Data Source
AI summary
A method for bonding a matrix of light-emitting elements onto a substrate includes forming conductive material on bond pads of the substrate in a matrix arrangement. Separately, a plurality of light-emitting elements is also picked up and placed onto a temporary carrier in the said matrix arrangement. The temporary carrier containing the plurality of light-emitting elements is then held with a bond head, and is moved by the bond head to establish contact between electrodes on the plurality of light-emitting elements and the conductive material on the substrate. When heat is applied to the light-emitting elements while exerting a compressive force with the bond head against the conductive material, conductive joints are formed between the light-emitting elements and the substrate.