Print Head Fly Height Control Using Reflective Optical Sensing
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Solution Overview
Problem
Existing methods for fabricating organic light emitting diodes (OLEDs) face challenges in precise deposition and thermal management, particularly in maintaining accurate fly height and thermal stability during the printing process, which affects the quality and efficiency of the devices.
Innovation Solution
The implementation of a system with a micronozzle array print head, optical sensors, and actuators that use reflective optical devices to accurately measure and adjust the distance between the print head and substrate, combined with thermal management to maintain precise thermal conditions for the sensors, ensuring reliable and accurate deposition and minimizing heat exposure to the sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If sensors are placed close to the printing zone for accurate measurement, then measurement precision is improved, but thermal exposure to sensors increases causing reliability degradation
Solution Approach 1:
A reflective optical device (mirror) is introduced as an intermediary between the sensor and the substrate. The sensor measures distance to the mirror rather than directly to the substrate, allowing the sensor to be positioned away from the hot printing zone while maintaining measurement accuracy through optical reflection.
Solution Approach 2:
The measurement approach transitions from direct spatial measurement to optical path measurement. By using light reflection, the system measures distance in an optical dimension rather than requiring the sensor to be physically close to the substrate in the mechanical dimension, thereby separating measurement function from thermal exposure.
2Manufacturing precision
If print head to substrate distance is reduced for precise deposition, then manufacturing precision is improved, but control difficulty increases due to confined space
Solution Approach 1:
The system implements closed-loop feedback control where the optical sensor continuously measures the actual distance between the print head and substrate (via mirror reflection), and this measurement feeds back to the control system which adjusts the print head position to maintain the target fly height, thereby achieving precise deposition control.
Solution Approach 2:
The system replaces complex mechanical positioning and measurement mechanisms with an optical measurement system. Instead of using mechanical encoders or contact-based measurement devices, the patent uses optical sensors and reflective optics to determine position, simplifying the mechanical complexity while improving measurement precision.
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 enhances the reliability and accuracy of the deposition process, improves the lifetime of the sensors, and maintains precise thermal management, leading to improved OLED quality and efficiency by ensuring closer measurements to the printing zone and effective thermal management.
Implementation Method 1
A reflective optical device may be disposed on the at least one print head to reflect the signal output by the at least one optical sensor, and to reflect the signal from a surface of the substrate to the optical sensor.
Data Source
AI summary
Embodiments of the disclosed subject matter provide a device having a print head that includes a micronozzle array of depositors to deposit a material on a substrate. A reflective optical device may reflect a signal output by at least one optical sensor, and to reflect the signal from a surface of the substrate to the optical sensor. A processor may determine a distance between the optical sensor and the target surface of the substrate. The device may include one or more actuators coupled to the at least one print head to move the print head relative to an internal reference frame and adjust a position of the print head to the substrate. The sensor may be fixedly coupled with a mount to the internal reference frame. The print head may be configured to move independently of the optical sensor in at least one axis of linear or rotational motion.