Micro Device Positioning via Liquid Layer Capillary Force
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Solution Overview
Problem
The precision of positioning micro devices on substrates during fabrication processes is challenging due to the small size of micro devices, requiring effective methods to securely hold and align them on conductive pads.
Innovation Solution
A method involving the formation of a conductive pad with a specific lateral length and a liquid layer on a substrate, where a micro device with a capillary force is gripped by the liquid layer, ensuring the micro device is held in a controllable position, with the conductive pad's lateral length being less than or equal to twice that of the micro device's lateral length, facilitating precise binding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a liquid layer is used to grip micro devices, then positioning precision is improved, but the method becomes ineffective for macroscopic devices where liquid layer grip is insufficient
Solution Approach 1:
The patent applies local quality by creating a liquid layer with specific local properties (capillary forces) that are effective for micro-scale devices. The liquid layer is formed with controlled thickness and distribution to provide sufficient grip force for micro devices with lateral lengths less than 100 μm, while the method explicitly excludes macroscopic devices where such local capillary forces become insufficient.
Solution Approach 2:
The patent utilizes parameter changes by exploiting the scale-dependent nature of capillary forces. At micro-scales, capillary forces dominate and provide effective gripping, while at macro-scales these forces become negligible. The method leverages this parameter change (force magnitude relative to device size) to achieve precise positioning for micro devices while recognizing the method's limitations for larger devices.
2Manufacturing precision
If the conductive pad lateral length is reduced to match micro device size, then positioning precision is improved, but the pad area for electrical contact is reduced
Solution Approach 1:
The patent applies local quality by concentrating the liquid layer and capillary forces in a localized region that matches the micro device footprint. The conductive pad is sized specifically (lateral length ≤ 2× device lateral length) to provide just enough contact area for the micro device, creating optimal local interaction without wasting substrate area on excessively large pads.
3Manufacturing precision
If the conductive pad lateral length is made less than or equal to twice the micro device lateral length, then positioning control is improved, but the risk of misalignment increases
Solution Approach 1:
The patent applies preliminary action by forming the liquid layer on the conductive pad before placing the micro device. This pre-formed liquid layer creates a capillary grip zone that actively guides and secures the device during placement, compensating for the reduced pad size and minimizing misalignment risks through the gripping action.
Solution Approach 2:
The patent uses the liquid layer as an intermediary between the conductive pad and micro device. This liquid intermediary creates capillary forces that actively hold and position the device, providing a mechanism for reliable alignment even when the pad dimensions are tightly constrained relative to device size.
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 enhances the precision and stability of micro device positioning on conductive pads, particularly for devices with lateral lengths less than 100 μm, ensuring secure binding and electrical contact, while avoiding issues with macroscopic devices where the liquid layer's grip is insufficient.
Implementation Method 1
the micro device is in contact with the liquid layer and is gripped by a capillary force produced by the liquid layer between the micro device and the conductive pad
Data Source
AI summary
A method of restricting a micro device on a conductive pad is provided. The method includes: forming the conductive pad having a first lateral length on a substrate; forming a liquid layer on the conductive pad; and placing the micro device having a second lateral length over the conductive pad such that the micro device is in contact with the liquid layer and is gripped by a capillary force produced by the liquid layer between the micro device and the conductive pad, the micro device comprising an electrode facing the conductive pad, wherein the first lateral length is less than or equal to twice of the second lateral length.