Raised Adhesive Layer Bonding for Faster Micro LED Transfer
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Solution Overview
Problem
The transfer process of micro LED chips using conventional surface mount systems is time-consuming and can damage both the micro LED chips and the permanent substrate due to pressure and thermal changes, leading to inefficient bonding and potential substrate damage.
Innovation Solution
A light-emitting assembly with a raised adhesive layer on a substrate, where the micro LED units are directly bonded to a circuit board in a single transferring step, minimizing damage and improving bonding strength through a design with protrusions on the adhesive layer and a protective layer for enhanced reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional surface mount system is used for transferring micro LED chips, then the transfer process can be completed, but the transfer time becomes extremely long (one month for six million chips)
Solution Approach 1:
The invention segments the transfer process into two distinct stages: (1) batch transfer of micro LED chips from substrate to adhesive layer, and (2) subsequent transfer from adhesive layer to permanent substrate. This segmentation enables parallel processing and eliminates the sequential bottleneck of conventional pick-and-place systems, dramatically increasing transfer speed.
Solution Approach 2:
The adhesive layer is applied to the permanent substrate in advance, creating a pre-prepared receiving surface. Micro LED chips are then batch-transferred onto this pre-positioned adhesive layer, eliminating the need for repeated positioning and bonding operations for each chip, thus significantly reducing total transfer time.
2Productivity
If conventional pick-and-place procedure is used, then micro LED chips can be transferred, but pressure and thermal changes occur between transfer head and permanent substrate affecting bonding strength
Solution Approach 1:
The adhesive layer serves as an intermediary between the micro LED chips and the permanent substrate. It provides a compliant bonding interface that accommodates thermal expansion differences and distributes bonding pressure uniformly, preventing the high localized stresses that would otherwise damage the chips or substrate during conventional direct bonding.
Solution Approach 2:
The adhesive layer acts as a pre-positioned cushioning layer that absorbs and distributes mechanical and thermal stresses before they reach the micro LED chips or permanent substrate. This beforehand cushioning prevents damage during the bonding process while maintaining reliable electrical and mechanical connections.
3Productivity
If repeated pick-and-place procedure is used, then micro LED chips can be transferred to permanent substrate, but the permanent substrate may be damaged
Solution Approach 1:
The invention extracts the bonding function from the permanent substrate by introducing a separate adhesive layer. The permanent substrate only needs to support the adhesive layer, while all bonding operations occur between the micro LED chips and the adhesive layer. This extraction eliminates repeated mechanical contact and potential damage to the permanent substrate.
Solution Approach 2:
The adhesive layer serves as a protective intermediary that absorbs all mechanical stresses during transfer operations. By positioning the adhesive layer between the transfer head and permanent substrate, it prevents direct impact forces from reaching the permanent substrate, thereby eliminating damage risks while maintaining batch transfer efficiency.
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 reduces the transfer time, minimizes damage to both the micro LED units and the circuit board, and enhances bonding efficiency, resulting in cost-effective and reliable production.
Implementation Method 1
an adhesive layer (30) disposed on the substrate (200) in a first direction
Implementation Method 2
The protective layer (500) is connected between the adhesive layer (30) and the light emitting units (100), and has a Shore A hardness greater than that of the adhesive layer (30)
Data Source
AI summary
A light-emitting assembly with a raised adhesive layer includes a substrate, an adhesive layer, a plurality of light emitting units, and a protective layer. The adhesive layer is disposed on the substrate in a first direction. The light emitting units are disposed on the adhesive layer opposite to the substrate in the first direction. Each of the light emitting units includes a first-type semiconductor layer, a second-type semiconductor layer, an active layer that is disposed between the first-type and second-type semiconductor layers, a first electrode that is electrically connected to the first-type semiconductor layer, and a second electrode that is electrically connected to the second-type semiconductor layer. The protective layer is connected between the adhesive layer and the light emitting units, and has a Shore A hardness greater than that of said adhesive layer. A light emitting apparatus is also provided herein.