Micro Pickup Array Shape Control via Piezoelectric Actuation
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Solution Overview
Problem
Integration and packaging of micro devices such as RF MEMS microswitches, LEDs, and quartz-based oscillators face challenges due to shape changes in micro pickup arrays during transfer, leading to inconsistent contact pressures and potential pick or place failures.
Innovation Solution
A support substrate with a piezoelectric actuator element is used to actively control the curvature of the micro pickup array, maintaining a stable shape through feedback loops and sensors, ensuring consistent contact pressures during micro device transfer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the micro pickup array is heated during transfer, then transfer speed and efficiency are improved, but thermal expansion causes shape distortion and contact pressure variation
Solution Approach 1:
The patent applies temperature compensation by dynamically adjusting the shape of the micro pickup array in response to thermal expansion. Shape control actuators modify geometric parameters of the array to counteract distortion caused by heating, maintaining contact pressure stability while enabling high-speed transfer operations
Solution Approach 2:
The system implements feedback control through shape sensors that continuously monitor the array shape and feed this information to a controller. The controller adjusts actuators in real-time to compensate for thermal distortion, creating a closed-loop system that maintains shape stability during heated transfer operations
2Reliability
If the micro pickup array shape is actively controlled to maintain stability, then contact pressure consistency is improved, but device complexity increases due to additional actuators and sensors
Solution Approach 1:
The micro pickup array is divided into multiple independently controllable unit cells, each with its own shape control actuator. This segmentation allows localized shape adjustment to maintain contact pressure consistency without requiring complex global control mechanisms across the entire array
Solution Approach 2:
The patent employs flexible membranes or thin film structures that can passively conform to shape adjustments made by actuators. This approach simplifies the overall structure by using compliant materials rather than rigid mechanical linkages, reducing device complexity while maintaining contact pressure consistency
3Productivity
If the micro pickup array operates at elevated temperature, then transfer efficiency is improved, but thermal gradient induces out-of-plane bending and position-dependent contact variations
Solution Approach 1:
The shape control system applies localized compensation to different regions of the micro pickup array based on their specific thermal conditions. Each unit cell or region can be independently adjusted to account for local thermal gradients, maintaining contact position accuracy even when operating at elevated temperatures for improved 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 ensures reliable transfer and placement of micro devices by maintaining a stable interface between the micro pickup array and the target substrate, preventing pick failures and ensuring appropriate contact pressures, thereby improving the integration and packaging process.
Implementation Method 1
a piezoelectric actuator element bonded to a support substrate to control a shape of the support substrate
Implementation Method 2
the transfer heads operate in accordance with principles of electrostatic grippers, using the attraction of opposite charges to pick up the micro devices
Data Source
AI summary
Structures and methods to actively control the shape of a micro pickup array (MPA) during micro device transfer are described. In an embodiment, a strain is applied to the MPA counteractive to strain arising during micro device transfer operations. For example, strain may be applied by a piezoelectric actuator element bonded to a back side of the base substrate to control a curvature of base substrate, and by extension the MPA.