The quartz-crystal resonator is the core device for frequency control in modern communication systems and network technology. At present, in modern resonator blanks manufacturing, BOE solution is usually used as the etching solution, but its etching rate is relatively volatile, and the surface morphology of the blanks is prone to defects after etching, which brings certain difficulties to the deep-etching process of the wafer. To solve the above challenges, this paper systematically compares a BOE solution and anhydrous etching solution in terms of etching rate, surface morphology, and electrical properties of the blanks after etching. Seven groups of blanks were etched using different etching solutions with different etching conditions to verify their effect on the surface morphology and electrical properties of quartz blanks. The experimental results suggest that the application of anhydrous etching solution has achieved better surface morphology and electrical properties and can be more suitable for application in batch manufacturing. In general, when using anhydrous etching solution, it is possible to reduce surface roughness by up to 70% and equivalent resistance by 32%, and the etch rate is almost 10 times lower than BOE solution under the same temperature, which is more conducive to the rate control of wafers in the etching process.

Quartz crystal resonators (QCRs) can be described by four parameters in the BVD-equivalent circuit: static capacitance (C ₀), motional capacitance (C ₁), motional inductance (L ₁), and motional resistance (R ₁). In this study, we propose a set of formulae through theoretical deduction to evaluate these four parameters using the impedances of QCRs at different frequencies. Using this method, engineers can evaluate the four parameters without theoretical errors in only one frequency sweep. The method has been verified by LTspice simulation. In the simulation, the average error was 0.35%, which demonstrated its correctness. Meanwhile, in practical measurements, compared to the parameters reported by 250B, the parameters calculated using this method demonstrated better fitting ability. Moreover, the calculation process was simple. Therefore, the measuring procedures and apparatus can be simplified using this method.

Due to the rapid cooling rate (230 mm/s) and large temperature gradient (107°C/m) produced by the self-propagating high-speed heat source, the liquid solder solidification procedure is extremely non-equilibrium, implying that the solder's original microstructure will invariably have a significant effect on the microstructure after melting and solidification. In this paper, a 300μm thick low-temperature eutectic solder Sn42Bi58 was heated by a 40μm AlNi self-propagating thin foil to investigate the impact of the solder's initial microstructure uniformity on the post-soldering microstructure. The results indicated that the melting time of SnBi solder was short due to the action of a self-propagating high-speed heat source, which resulted in the incomplete melting of heterogeneous phases and the non-uniform distribution of elements during the solder melting process, which had a significant effect on the morphology and composition distribution of the solidified microstructure. The preceding conclusions have the potential to improve the interconnection process based on the self-propagation reaction of AlNi thin foil, which is critical for both theoretical guidance and engineering application.