Porosity effect on the mechanical properties of nano-silver solder.

Nano-silver has the characteristics of low-temperature sintering and high-temperature service, which can reduce the thermal stress in the packaging process. Because of the high melting point and good high-temperature mechanical properties, silver is widely used in high-temperature packaging and connection fields. Sintered nano-silver has a porous structure on the microscopic level, it is necessary to study the mechanical properties of nano-silver with porosity. In this paper, we proposed a method for finite element modeling of porous nano-silver. Finite element analysis and nanoindentation test were used to investigate the Young's modulus of nano-silver. At the same time, and the quadratic equation of porosity and Young's modulus was fitted, and it was verified by Ramakrishnan model and nanoindentation results. These results show that the Young's modulus of nano-silver decreases with the increase of internal porosity, and the Young's modulus and porosity show a quadratic function correlation. As the porosity increases, the Young's modulus of nano-silver decreases at a slower rate. The modeling method presented in this paper can well predict the Young's modulus of nano-silver.

Correction of thermal airflow distortion in warpage measurements of microelectronic packaging structures via deep learning-based digital image correlation.

The projected speckle-based three-dimensional digital image correlation method (3D-DIC) is being increasingly used in the reliability measurement of microelectronic packaging structures because of its noninvasive nature, high precision, and low cost. However, during the measurement of the thermal reliability of packaging structures, the thermal airflow generated by heating introduces distortions in the images captured by the DIC measurement system, impacting the accuracy and reliability of noncontact measurements. To address this challenge, a thermal airflow distortion correction model based on the transformer attention mechanism is proposed specifically for the measurement of thermal warpage in microelectronic packaging structures. This model avoids the oversmoothing issue associated with convolutional neural networks and the lack of physical constraints in generative adversarial networks, ensuring the precision of grayscale gradient changes in speckle patterns and minimizing adverse effects on DIC calculation accuracy. By inputting the distorted images captured by the DIC measurement system into the network, corrected images are obtained for 3D-DIC calculations, thus allowing the thermal warpage measurement results of the sample to be acquired. Through experiments measuring topography with customized step block specimens, the effectiveness of the proposed method in improving warpage measurement accuracy is confirmed; this is particularly true when captured images are affected by thermal airflow at 140 °C and 160 °C, temperatures commonly encountered in thermal reliability testing of packaging structures. The method successfully reduces the standard deviation from 9.829 to 5.943 µm and from 12.318 to 6.418 µm, respectively. The results demonstrate the substantial practical value of this method for measuring thermal warpage in microelectronic packaging structures.

Design and Optimization of a Novel MEMS Tuning Fork Gyroscope Microstructure.

This paper presents the design and optimization of a novel MEMS tuning fork gyroscope microstructure. In order to improve the mechanical sensitivity of the gyroscope, much research has been carried out in areas such as mode matching, improving the quality factor, etc. This paper focuses on the analysis of mode shape, and effectively optimizes the decoupling structure and size of the gyroscope. In terms of structural design, the vibration performance of the proposed structure was compared with other typical structures. It was found that slotting in the middle of the base improved the transmission efficiency of Coriolis vibration, and opening arc slots between the tines reduced the working modal order and frequency. In terms of size optimization, the Taguchi method was used to optimize the relevant feature sizes of the gyroscope. Compared with the initial structure, the transmission efficiency of Coriolis vibration of the optimized gyroscope was improved by about 18%, and the working modal frequency was reduced by about 2.7 kHz. Improvement of these two indicators will further improve the mechanical sensitivity of the gyroscope.