MEMS Pirani gauges achieve high-precision measurements of air pressure through multilayer thin-film structures. However, the thin-film structure makes the device vulnerable to thermal stresses during operation due to its insufficient mechanical toughness and limited deformability characteristics. In order to deeply explore the influence of thermal stress on the performance of thin-film devices, this study utilized COMSOL Multiphysics to conduct finite element analysis on MEMS Pirani gauges with two distinct heating mechanisms. The impact of thermal stress on the MEMS Pirani gauge was systematically evaluated by integrating the coupling effects of thermal, mechanical, and electrical multiphysics fields. The numerical simulation outcomes revealed the influence of thermal stress on the sensitivity, stability, and measurement accuracy of the Pirani gauge under varying thermal conditions. It was demonstrated that persistent thermal stress can lead to the degradation of thin-film material properties and electrical characteristic drift, thereby affecting the reliability of the Pirani gauge. The findings provided by the finite element simulation in this study offer crucial insights for the optimal design and risk mitigation strategies of MEMS Pirani gauges. © Published under licence by IOP Publishing Ltd.

This study focusses on heat-generating thermistors in microelectromechanical systems (MEMS) flow sensors and explores their heat-generating characteristics in sand and dust polluted environments. A mathematical model was developed and a corresponding simulation model was constructed to assess the joint effect of dust deposition thickness and external input voltage on the heat generation temperature of the thermistor. The study reveals a significant inhibitory effect of dust particles on the heat transfer efficiency. Controlling for other variables, we established quantitative relationships between thermistor temperature and dust deposition thickness and input voltage. © Published under licence by IOP Publishing Ltd.

The effect of organic contamination on the sensitive comb structure of accelerometers in microelectromechanical systems (MEMS) is hardly involved in the original MEMS reliability study, because the existing technology can guarantee chip packaging in the absence of contamination, but with the advancement and popularity of multi-chip packaging technology, some chip devices may have organic substances volatilised and have an effect on the strength of the comb structure of accelerometer devices, thus affecting the service life of the devices. However, with the progress and popularity of multi-chip packaging technology, some of the chip devices may have volatilisation of organic substances, which may affect the strength of the acceleration sensor comb, and thus the service life of the device. In this paper, the theoretical derivation and experimental verification method to complete the study, and in the organic pollution test, organic substances will mainly have an impact on the strength of the comb structure of the acceleration sensor, so this paper focuses on the comb structure before and after the organic pollution of the strength of the change. The results of the experimental study show that the strength of the comb structure of the MEMS device decreases to a certain extent after the contamination compared with that before the contamination. This research result provides a theoretical basis for finding the failure inducing factors in the MEMS failure mode and predicting the device life. © 2024 IEEE.

This paper presents a new method for wafer-level packaging of MEMS silicon-on-insulator (SOI) sensors and actuators working in the situation of over-loading. The developed process starts with backside deep reactive ion etching (DRIE) of the substrate to define the support structures as down stop blocks. This is followed by hydrofluoric acid etching to remove excessive SiO2 layer underneath the structural area to free the movable device parts. Then, another step of DRIE was applied on the device layer to form the device features. As the area of support structures are much smaller than proof mass, no stiction was observed. Finally, a glass wafer was used to encapsulate the switch using an anodic bonding technique to form a up stop block. In the work described here, the process is demonstrated for micromachining of an optical switch surviving from the high-impact overload environment at 20,000 g with pulse-width 120 μs. © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2024.

The thermally conductive silver adhesive is widely used as a thermal interface material for thermal management of electronic device packaging. In engineering applications, the evolution of holes inside the silver adhesive interface seriously affects its service life. In this paper, we designed high-temperature accelerated aging experiments for submicron silver adhesive interfaces. The evolution of the pores during interfacial aging was characterized by X-ray scanning and scanning electron microscopy and counting the porosity. The temperature fields of interfaces with different porosities were simulated using finite element simulation. Both experimental and simulation results show that the increase in porosity accelerates the aging of the silver-glue interface. When the porosity is increased to 30%, the simulated equivalent thermal conductivity reduces by 52.50%, and the experimentally tested interfacial thermal resistance increases by 71.58%. The experimental test results of the interfacial thermal resistance are more significant than the simulated results, indicating that porosity is not the only factor influencing accelerated interfacial aging. It provides a theoretical and experimental basis for further research on porosity accelerated aging of silver adhesive interfaces. © 2023 IEEE.

The electromigration life of interconnects under pulsed current will change significantly compared to DC conditions. To accurately predict the reliability life of micro-copper pillar bump under pulsed current stress, in this paper, based on the built electromigration test system, accelerated life tests were carried out at 110°C, 125°C and 140°C temperature coupled 100Hz frequency bidirectional pulsed current 2.5-3.0 ×104A/cm2. The effects of parameters such as temperature, current density, and forward current percentage on electromigration life were investigated. The reliability life model of micro-copper pillar bump interconnects under bi-directional current stress was successfully established by introducing a damage recovery factor γ into the Black equation. The modeling establishment process entirely considers the effect of the Joule heating effect, fitting the current density index n is 15.52, activation energy Q is 1.09 eV, and the damage recovery coefficient γ is determined to be -0.81. No significant correlation is found between γ and temperature and current density performance. The lifetime model shows that the change in current direction will slow down the electromigration effect of the micro bump but will not eliminate the resulting electrically induced damage. The mathematical relationships the model establishes between parameters such as temperature, current density, time proportion of the forward current, and electromigration lifetime of copper pillar bumps under bidirectional current are important engineering references to support high-density packages' design and lifetime prediction. © 2023 IEEE.

The sensitive structures of certain devices containing micro-electromechanical system (MEMS) must be directly exposed to the working environment, making them vulnerable to contamination by dust and other pollutants in that environment. Consequently, this contamination degrades the performance of the device, impacting both its working life and stability. Existing test methods, such as GB/T 4208-2017 and GB/T 2423.37-2006, are not entirely suitable for evaluating the sand and dust contamination test of these MEMS devices. To address these issues, a thermistor-based test structure was designed and processed to develop an evaluation method suitable for testing the sand and dust contamination sensitive MEMS structures. The test results indicate that, unlike other hermetically sealed electronic devices, the imposition of electrical stress and cycling of the operating voltage "on-off" during the test does not increase dust accumulation. Furthermore, due to sand and dust contamination, the thermistor value of the device drifts during operation. This drift primarily arises from increased thermal resistance between the heating element of the device and the surrounding environment, resulting from the accumulation of sand and dust, which results in the increase of temperature of the heating element and ultimately results in an elevated thermistor value. This study can provide support for the structural design and package design of MEMS sensitive structures, and provide a basis for the identification and inspection of related products and the development of detailed specifications. © 2023 IEEE.

The number of datacenters worldwide has increased substantially over the past two decades to handle the large amount of information and data available. To meet the complex computing requirements, the thermal design power of high-performance computing (HPC) increases, leading to serious thermal management challenges. In this study, embedded manifold cooling (EMC) system for HPC ICs is proposed. It is successfully maintaining the temperature rise of commercial CPU to 18K under thermal stress conditions. By processing the embedded microchannel on the bulk silicon and bonding with 3D manifold structure, the coolant is directly introduced into the chip to minimize the thermal resistance between the heat source and ambient. Integrated miniature circulating pump and heat exchanger ensure the cooling system is compatible with the existing computing system. The results show that the cooling performance of embedded manifold cooling under thermal stress conditions is 71.4% higher than that of air cooling and 60.7% higher than that of immersion cooling. © 2022 IEEE.

In this work, we reported a novel donut-step combined microchannel for sheathless inertial particle focusing, which both Dean flow and geometry-induced secondary flow can be generated and enhanced. We used 10.7 μm fluorescent particles to test the focusing performance of the presented chips with an inverted fluorescent microscope. We achieved a narrow focusing width of ≈10.2 μm and a throughput of ≈4000 particles/s, with a flow rate of ≈300 μL/min. © 2022 MicroTAS 2022 - 26th International Conference on Miniaturized Systems for Chemistry and Life Sciences. All rights reserved.

This work reported a method for embedding jet impingement micro-structures into an integrated circuit (IC) chip's substrate. The IC chip can keep the junction temperature less than 120°C at high power density (2200 W/cm2) using this method. Trapped by traditional chip packaging and heat dissipation methods, the inability to remove dissipated heat has led to the clock frequency stabilized at around 3 GHz, and the gate array ratio is also strictly controlled within 20%. Our method is expected to increase the computational efficiency of IC chips without improving the CMOS process node. © 2022 IEEE.