Clustered Micro Pick-Up Arrays for High-Density Sequential Placement
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Solution Overview
Problem
Integration and packaging issues, particularly in transferring micro devices like RF MEMS microswitches, LEDs, and quartz-based oscillators, are hindered by traditional direct printing and transfer printing methods, which require de-bonding the transfer wafer and involve the entire wafer in the transfer process, limiting commercialization and efficiency.
Innovation Solution
A mass transfer tool with articulating transfer head assemblies and micro pick-up arrays, featuring clusters of transfer heads with intra-cluster and inter-cluster spacing, allowing for high-density pick and place operations using elastomeric contact, vacuum, or electrostatic principles, enabling efficient transfer of micro devices between donor and receiving substrates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If traditional direct printing or transfer printing methods are used, then device transfer is achieved, but the process requires de-bonding the transfer wafer and involves the entire wafer, limiting efficiency and commercialization
Solution Approach 1:
The patent divides the transfer process into discrete pick and place operations using individual transfer heads arranged in arrays. Each transfer head independently picks up and places devices, eliminating the need to handle the entire wafer at once. This segmentation enables parallel processing and eliminates de-bonding steps, directly resolving the contradiction between transfer efficiency and process complexity.
Solution Approach 2:
The patent replaces traditional mechanical bonding and de-bonding processes with electrostatic forces. Transfer heads use electrostatic attraction to pick up devices from the donor substrate and release them on the target substrate through voltage control. This substitution eliminates the need for wafer bonding and de-bonding operations, simplifying the process while maintaining high transfer efficiency.
2Quantity of substance
If transfer heads are arranged with small spacing for high density, then transfer density increases, but compressive forces on devices increase
Solution Approach 1:
The patent implements compliant transfer heads with localized elastic elements that can independently deform to accommodate device variations. Each transfer head has tailored compliance characteristics that allow it to apply minimal compressive force while maintaining secure contact. This local quality adjustment enables high-density arrangement without increasing overall compressive forces on devices.
Solution Approach 2:
The patent uses electrostatic voltage parameters to control the gripping force of transfer heads. By adjusting the voltage applied to each transfer head, the system can maintain secure device holding without requiring excessive mechanical compression. This parameter control allows high-density transfer head arrangement while keeping compressive forces on individual devices within safe limits.
3Ease of operation
If electrostatic transfer heads are used without shielding, then transfer operation is simple, but stray electric fields may affect device integrity
Solution Approach 1:
The patent introduces electrostatic shields as intermediary elements between the transfer heads and the devices being transferred. These shields, positioned adjacent to the transfer heads, intercept and redirect stray electric fields away from the devices. This intermediary structure protects device integrity while maintaining the simplicity of electrostatic transfer operation, as the shields are passively integrated into the transfer head assembly.
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
The solution enables high-density transfer of micro devices with increased throughput and reduced costs, protecting device integrity through compliant transfer heads and electrostatic shielding, while accommodating varying substrate topographies and reducing compressive forces.
Implementation Method 1
the transfer heads operate in accordance with principles of electrostatic grippers, using the attraction of opposite charges to pick up the micro devices
Implementation Method 2
Each of the plurality of transfer heads may include an elastomeric contact surface
Data Source
AI summary
Mass transfer tools and methods for high density transfer of arrays of micro devices are described. In an embodiment, a mass transfer tool includes a micro pick up array with an array of transfer heads arranged in clusters. The clusters of transfer heads can be used to pick up a high density group of micro devices followed by sequential placement onto a receiving substrate.