Micro LED Transfer Stamp Structure for High-Temperature Alignment
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Solution Overview
Problem
Existing mass transfer technologies for micro LEDs, such as those using PDMS stamps, are incompatible with eutectic bonding, suffer from alignment deviations due to thermal expansion, and are limited to small sizes, leading to unstable yields and high costs.
Innovation Solution
A stamp design featuring position limiting structures and transfer structures with a viscosity adjustable layer, allowing for uniform height and alignment control, enabling large-scale micro LED transfer and bonding without direct contact with the driving substrate, using materials that maintain adhesion and separation capabilities under high temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If PDMS stamps are used for mass transfer, then transfer capability is achieved, but alignment deviation occurs due to thermal expansion during eutectic bonding
Solution Approach 1:
The stamp is divided into multiple independent transfer structures (protrusions) with position limiting structures, allowing each to maintain uniform height independently. This segmentation prevents cumulative alignment deviations that would occur with a single large stamp structure subjected to thermal expansion during eutectic bonding.
Solution Approach 2:
The patent changes the material parameter of the stamp from PDMS to a material with lower thermal expansion coefficient, and adjusts the structural parameter by creating position limiting structures. These parameter changes enable the stamp to maintain dimensional stability during high-temperature eutectic bonding processes, preventing alignment deviation.
2Area of stationary object
If stamp size is increased for large-scale applications, then coverage area improves, but uniformity and alignment accuracy deteriorate
Solution Approach 1:
The large-area stamp is segmented into multiple smaller transfer structures (protrusions) distributed across the substrate. Each protrusion maintains uniform height and alignment independently, while collectively covering large areas. This segmentation allows the stamp to achieve both large coverage area and high alignment accuracy simultaneously.
Solution Approach 2:
The patent transitions from a single large two-dimensional stamp structure to a three-dimensional array of multiple smaller protrusions. This dimensional change allows each protrusion to maintain precise alignment while the collective array covers large areas, resolving the contradiction between area and precision.
3Reliability
If existing stamp materials are used, then transfer function is achieved, but material degradation occurs under high temperatures during bonding
Solution Approach 1:
The patent changes the material parameter from PDMS to a high-temperature stable material that can withstand eutectic bonding temperatures without degradation. This parameter change enables the stamp to maintain its structural integrity and transfer capability during high-temperature bonding processes.
Solution Approach 2:
The stamp employs composite material construction with position limiting structures and transfer structures made from materials selected for their thermal stability. This composite approach ensures the stamp can function reliably under high-temperature eutectic bonding conditions while maintaining transfer capability.
4Productivity
If direct contact between stamp and driving substrate is used, then transfer efficiency improves, but adhesion and separation control becomes difficult
Solution Approach 1:
The patent applies local quality by creating position limiting structures that confine the interaction to specific localized regions (at the tips of protrusions). This localized contact improves transfer efficiency while maintaining easy adhesion and separation control through the viscosity adjustable layer, as the contact area is precisely defined and limited.
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
Improves transfer and bonding efficiency by maintaining uniformity and alignment accuracy, enabling larger size applications while reducing material degradation and cost.
Implementation Method 1
a viscosity adjustable layer 32, of which an orthogonal projection on the base plate overlaps with orthogonal projections of the protrusions on the base plate, contacts with and stick to the light emitting diodes
Data Source
AI summary
A stamp includes a substrate; position limiting structures located on a side of the substrate and spaced apart from each other; and transfer structures, which are located on the side of the substrate where the position limiting structures are located, and are spaced apart from each other. The position limiting structures are in one-to-one correspondence with the transfer structures. Each position limiting structure surrounds a periphery of a corresponding transfer structure, and an orthogonal projection of the position limiting structure on the substrate does not overlap with an orthogonal projection of the corresponding transfer structure on the substrate. A distance between an end surface of an end, which is distal to the substrate, of each transfer structure and the substrate is greater than a distance between an end surface of an end, which is distal to the substrate, of a corresponding position limiting structure and the substrate.