Study On The Mechanism And Technology Of Quartz Pendulous Reed Processing Based On The Picosecond Laser Modification Assisted Wet Etching

Quartz flexible accelerometer is the acceleration measurement sensor used in high-precision inertial navigation system,which plays an important role in aviation,aerospace,national defense and other fields.The quartz pendulous reed is the core part of the quartz flexible accelerometer,which has a decisive influence on the working accuracy and performance of the quartz flexible accelerometer.However,due to the hard and brittle material characteristics of fused silica and the technical blockade of foreign countries,the quartz pendulous reed forming processing technology in our country still suffers from poor processing quality and high production cost.Therefore,it is urgent to find a new fabricating method.To address the above problems,based on the spatial shaping picosecond laser induced fused silica material modification,combined with wet etching composite processing technology to carry out the quartz pendulous reed forming processing mechanism and processing technology research in this thesis.The quartz pendulum reed forming processing technology based on picosecond laser modification-assisted wet etching was proposed.The Gaussian beam was transformed into the Bessel beam,and discrete distribution of microcavities and nanocracks along the laser transmission direction was induced by laser modification.With the assistance of ultrasonic vibration,the HF solution can penetrate into the modified area through the microchannel formed by laser modification to widen the cutting slit so that the material to be removed can be separated automatically from the substrate.The main research contents are as follows:（1）The dimensional accuracy of the quartz pendulous reed is as high as±3μm formed by the picosecond laser modification assisted wet etching technology,and both top and rear surface dimensions have high consistency and stability.The edges are smooth without visible microcracks,and the largest edge chipping was only 4μm;The maximum residual stress introduced by laser modification is only 35.3 k Pa,which is smaller than the thermal stress generated by CO₂laser ablation cutting（24.1MPa）and the maximum allowable stress of the quartz pendulous reed（50 k Pa）;Smooth and flat surface quality obtained by optimizing wet etching process parameters;The laser modification of single quartz pendulous reed can be finished in less than 3 min,and wet etching can be completed within 10 min,which both meet the economic and high efficiency requirements of industrial production.（2）The spatial distribution of laser energy was optimized by beam shaping,and the Gaussian beam was transformed into the Bessel beam,which is more suitable for material modification with larger thickness;The picosecond Bessel laser energy allows for better deposition along the axial direction to produce discrete distribution of microcavities along the thickness of the material.The Raman spectra of the pristine sample and the picosecond laser modified area showed that the microscopic molecular structure of fused silica is not significantly reconstructed by picosecond laser modification（rearrangement of cyclic molecular structure）;According to the morphology analysis of picosecond laser modified cross-section,it is proposed that the mechanism of picosecond laser modification is due to the high-pressure shock wave that induced by the significant local thermal effect generated by the interaction between laser pulse and material,and the discrete distribution of microcavities along the laser transmission direction is formed.These microcavities have a significant accelerating effect on HF wet etching,and the above theoretical mechanism is further verified by KOH etching comparison experiment.（3）The influence of different etching temperature and HF solution concentration on the slit width and thickness of quartz pendulous reed was studied by orthogonal experiment;A multi-level orthogonal experiment with three factors including HF concentration,etching time and etching temperature was designed,and the mapping among etching volume,etching temperature,HF solution concentration and etching time was established.It provides technical guidance and data support for precise control of wet etching time and etching rate.