Micro Pick Up Array With Compliant Contacts For Device Transfer
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Solution Overview
Problem
Integration and packaging issues, particularly in transferring micro devices such as RF MEMS microswitches, LED display systems, and quartz-based oscillators, are hindered by traditional transfer printing technologies that require the entire transfer wafer with devices to be involved in the process, limiting efficiency and scalability.
Innovation Solution
A micro pick up array with compliant contacts, featuring a base substrate, flexible membrane, and electrostatic transfer heads, allows for the transfer of micro devices by applying a clamping voltage to secure the array against a transfer head assembly, enabling relative movement between the plug and base substrate for precise and efficient device handling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If traditional transfer printing technology is used, then the entire transfer wafer with devices must be involved in the transfer process, but this limits efficiency and scalability
Solution Approach 1:
The invention divides the transfer wafer into individual transferable elements (TEs) that can be selectively manipulated and transferred independently. Each TE contains a micro device and associated structures, allowing parallel processing and selective transfer to multiple targets simultaneously, thereby improving productivity while reducing process complexity
Solution Approach 2:
The invention introduces a vertical dimension by forming TEs that extend through the thickness of the transfer wafer, with conductive elements connecting upper and lower surfaces. This three-dimensional structure enables electrical connection and mechanical support while allowing selective transfer of individual elements without moving the entire wafer
2Measurement precision
If the plug is made moveable relative to the base substrate, then precise device handling is enabled, but electrical contact reliability may be compromised
Solution Approach 1:
The invention uses a flexible membrane structure supporting the plug, allowing controlled deflection and movement relative to the base substrate. This flexibility enables precise positioning for device handling while maintaining continuous electrical contact through the compliant connection, resolving the contradiction between movement precision and contact reliability
Solution Approach 2:
The plug is designed to be dynamically moveable within the via through the flexible membrane, rather than fixed. This dynamic capability allows the plug to adjust its position for precise device manipulation while the flexible connection ensures continuous electrical connectivity, maintaining reliability during movement
3Reliability
If a gap is introduced to separate the plug from the base substrate, then high breakdown voltage is achieved, but electrical resistance increases
Solution Approach 1:
The invention creates different electrical properties in different regions: a large gap (10-100 μm) provides high breakdown voltage for reliability, while localized conductive elements (metal traces, doped regions) within the flexible membrane maintain low electrical resistance for efficient signal and power transmission, resolving the contradiction between breakdown voltage and resistance
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
Enables the secure and efficient transfer of micro devices with high precision and scalability, allowing for the integration of micro LED devices into larger systems with high transfer rates, while maintaining uniform electrical contact and minimizing electrical resistance.
Implementation Method 1
The flexible membrane may include a silicon layer and be deflectable such that the plug is moveable by not more than 5 μm along an axis orthogonal to the flexible membrane
Implementation Method 2
A micro pick up array with compliant contacts, featuring a base substrate, flexible membrane, and electrostatic transfer heads, allows for the transfer of micro devices by applying a clamping voltage
Data Source
AI summary
Micro pick up arrays for transferring micro devices from a carrier substrate are disclosed. In an embodiment, a micro pick up array includes a compliant contact for delivering an operating voltage from a voltage source to an array of electrostatic transfer heads. In an embodiment, the compliant contact is moveable relative to a base substrate of the micro pick up array.