Acousto-Optic Beam Deflection for High-Speed Laser Micromachining
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current laser processing technologies face challenges in achieving high-speed, precise, and efficient ablation of fine features in chip packaging due to limitations in beam positioning, intensity control, and thermal management, particularly at high velocities and small feature sizes, leading to issues like depth variation, thermal side effects, and beam distortion.
Innovation Solution
A laser processing system combining a galvanometer-driven subsystem with an acousto-optic deflector (AOD) to provide high-speed beam positioning and intensity control, allowing for dithering and power modulation to create customized spot profiles and maintain constant dosage, while also using AODs to stabilize beam jitter and minimize thermal effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If traditional galvo mirrors and linear stages are used for beam positioning, then the system structure is simple, but the beam position acceleration is limited and cannot meet high-velocity processing requirements
Solution Approach 1:
The patent replaces the mechanical galvo mirror system with an acousto-optic deflector (AOD) that uses acoustic waves to modulate the refractive index of a crystal, thereby deflecting the laser beam. This substitution of mechanical system with an acoustic-optical system enables beam position acceleration exceeding the dynamic limits of traditional galvos while maintaining compact system architecture.
Solution Approach 2:
The patent changes the operating parameters of the AOD by varying the acoustic frequency and amplitude to dynamically control beam position and acceleration. This parameter-based control allows rapid beam repositioning without mechanical inertia limitations, achieving the required beam position acceleration for high-velocity processing.
2Productivity
If high peak power laser pulses are used to ablate material, then ablation efficiency is improved, but thermal side effects such as melting and cracking increase
Solution Approach 1:
The patent uses periodic ultrafast laser pulses with carefully controlled repetition rates and duty cycles to ablate material. The pulsed nature of the laser delivers high peak power for efficient ablation while the interpulse cooling period prevents thermal accumulation, thereby reducing thermal side effects like melting and cracking.
Solution Approach 2:
The patent exploits the phase transition of material from solid to vapor through ultrafast laser ablation. The high peak power pulses induce direct sublimation or vaporization of material without passing through a molten phase, avoiding thermal damage associated with melting and subsequent cooling.
3Adaptability or versatility
If the laser beam spot characteristics are changed to process different features, then feature versatility is improved, but processing time increases due to reconfiguration delays
Solution Approach 1:
The patent implements dynamic control of beam spot characteristics through real-time modulation of AOD parameters and laser pulse properties. The system can rapidly change beam size, shape, and position by adjusting acoustic fields and pulse parameters without mechanical reconfiguration, enabling versatile feature processing with minimal time loss.
Solution Approach 2:
The patent creates a universal beam control system where the AOD and laser pulse modulator work together to provide multiple processing capabilities (different spot sizes, shapes, and positions) through a single integrated system. This multi-functional approach eliminates the need for separate optical components for different feature types, reducing reconfiguration time.
4Productivity
If high beam position acceleration is achieved for high-velocity processing, then throughput is improved, but beam positioning accuracy decreases due to dynamic limits
Solution Approach 1:
The patent implements feedback control where the actual beam position is continuously monitored and compared with the desired position. The error signal is used to adjust AOD parameters in real-time, compensating for any positioning deviations and maintaining high accuracy even during high-acceleration beam repositioning for high-velocity processing.
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 flexible, high-speed, and precise processing of features with reduced thermal side effects and improved accuracy, allowing for tight control of feature dimensions and depth variation, even at high velocities, thereby enhancing throughput and reducing material damage.
Implementation Method 1
A laser processing system combining a galvanometer-driven subsystem with an acousto-optic deflector (AOD) to provide high-speed beam positioning and intensity control
Implementation Method 2
Laser processing of dielectric and conductive materials is commonly used to ablate fine features in electronic components
Data Source
AI summary
A laser processing system for micromachining a workpiece includes a laser source to generate laser pulses for processing a feature in a workpiece, a galvanometer-driven (galvo) subsystem to impart a first relative movement of a laser beam spot position along a processing trajectory with respect to the surface of the workpiece, and an acousto-optic deflector (AOD) subsystem to effectively widen a laser beam spot along a direction perpendicular to the processing trajectory. The AOD subsystem may include a combination of AODs and electro-optic deflectors. The AOD subsystem may vary an intensity profile of laser pulses as a function of deflection position along a dither direction to selectively shape the feature in the dither direction. The shaping may be used to intersect features on the workpiece. The AOD subsystem may also provide rastering, galvo error position correction, power modulation, and/or through-the-lens viewing of and alignment to the workpiece.