Mechanical Shock Reliability Analysis and Multiphysics Modeling of MEMS Accelerometers in Harsh Environments

2015 ◽  
Author(s):  
Pradeep Lall ◽  
Nakul Kothari ◽  
Jessica Glover
Keyword(s):  
Failure Modes ◽  
Complex Structure ◽  
Harsh Environments ◽  
Mechanical Shock ◽  
Mems Devices ◽  
Ambient Conditions ◽  
Physics Of Failure ◽  
Mems Sensor ◽  
Voltage Change ◽  
Mems Accelerometers

MEMS accelerometers have found applications in harsh environments with pressure, temperatures above ambient conditions, high g shock and vibrations. The complex structure of these MEMS devices has made it difficult to understand the failure modes and failure mechanisms of present day MEMS accelerometers. Little work has been done by the researchers in investigating the high g reliability of the MEMS accelerometers by continuous high g drops and quantifying the failure modes. There is little literature addressing the multiphysics finite element modelling of MEMS accelerometers subjected to high g shocks. In defense applications, where these devices are integrated with several other compactly assembled subsystems, lack of knowledge on the physics of failure for the MEMS sensor in harsh environment operation, can be detrimental to the success of the system on the whole. Being able to successfully model inside of an accelerometer, enables the user to better understand the change in parameters like time delay induced in response of successive drops, change in pulse width that indicate failure, reduction in sensed g levels. Some researchers have subjected various accelerometers to repeated drops at their maximum sensing g(not high g) level, and used optical microscopy to detect damaged sensing elements [Beliveau, 1999]. Few researchers have modeled the internal structure of the MEMS device, along with the device packaging under the stresses of operation [Fang 2004, Ghisi 2008, Xiong 2008]. In this paper, a multiphysics model of capacitive and the moving elements of the accelerometer has been developed to model the change in capacitance with respect to stroke and understand the correlation with g-levels, in addition to the transient dynamic response of the accelerometer under high-g shock. This has not been much explored in the past. The accelerometer studied in the paper is the ADXL193, and subjected to repeated drops of 3000g in each 3 axes as per 2002.4 of MIL-STD-883 without preconditioning. A characteristic graph of capacitance vs accelerometer stroke has been obtained from a series of electrostatic simulations and is then used to relate g levels, capacitance, stroke deflection and voltage change using electromechanical transducer elements. The drift in the performance characteristics of the accelerometer have been measured versus the number of shock events. In addition, an attempt has been made to investigate the failure mode in the accelerometer.

Survivability of MEMS Accelerometer Under Sequential Thermal and High-G Mechanical Shock Environments

2015 ◽  
Author(s):  
Pradeep Lall ◽  
Amrit Abrol ◽  
Lee Simpson ◽  
Jessica Glover
Keyword(s):  
Failure Modes ◽  
Performance Enhancement ◽  
Research Work ◽  
Harsh Environments ◽  
Mechanical Shock ◽  
X Rays ◽  
Mems Devices ◽  
Mems Accelerometer ◽  
Capacitive Accelerometer ◽  
Mems Accelerometers

Reliability data on MEMS accelerometers operating in harsh environments is scarce. Micro-electro-mechanical systems (MEMS) are used in a variety of military and automotive applications for sensing acceleration, translation, rotation, pressure and sound. This research work focuses on dual axis MEMS accelerometer reliability in harsh environments. Structurally an accelerometer behaves like a damped mass on a spring. Commercially there are three types of accelerometers namely piezoelectric, piezoresistive and capacitive depending on the components that go into the fabrication of the MEMS device. Previously, majority of concentration was focused on an effective internal design, performance enhancement of CMOS-MEMS accelerometers and packaging techniques Cheng [2002], Qiao [2009], Lou [2005], and Weigold [2001]. Studies have also been conducted to obtain an enhanced inertial mass SOI MEMS process using a high sensitivity accelerometer Jianbing [2013], Chen [2005]. There have been prior test(s) conducted on MEMS accelerometers, Jiang [2004], Cao [2011], Chun-Sun [2009], Lou [2009], Tanner [2000] and Yang [2010] but the availability of data on reliability degradation of such devices in harsh environments Brown [2003] is almost little to none which thereby generates the importance of this work and also makes way for a whole new path involving the reliability assessment techniques for MEMS devices. Concentration of our work is primarily on the reliability of this accelerometer upon sequential exposure to harsh environment(s) and drop-shock. Reliability of accelerometers in high G environments is unknown. The effects of these pre-conditions along with the drop test condition has been studied and analyzed. In this piece of research work, a test vehicle with a MEMS accelerometer, ADXL278 dual axis capacitive accelerometer, has been tested under high/low temperature exposure followed by subjection to high-g and low-g shock loading environments. The test boards have been subjected to mechanical shocks using the method 2002.5, condition G, under the standard MIL-STD-883H test. The stress environment and the test condition used for this paper are 1500g and 70g respectively where 70g is the full scale range output of ADXL278 in the drop direction with pulse duration set to 0.5millisecond. The deterioration of the accelerometer output has been characterized using the techniques of Mahalanobis distance and Confidence intervals. Scanning Electron Microscopy (SEM) has been used to study the different failure modes inside of the accelerometer, which were potted and polished and later de-capped. Furthermore, the non-destructive evaluations of the MEMS accelerometer have been demonstrated through X-rays and micro-CT scans.

The Response of Electrostatic MEMS Structure under Mechanical Shock and Electrostatic Forces

2013 ◽  
Vol 427-429 ◽  
pp. 120-123
Author(s):  
Xiang Guang Li ◽  
Qin Wen Huang ◽  
Yun Hui Wang ◽  
Yu Bin Jia ◽  
Zhi Bin Wang
Keyword(s):  
Failure Modes ◽  
Electrostatic Force ◽  
Short Circuit ◽  
Superposition Method ◽  
Mechanical Shock ◽  
Mems Devices ◽  
Electrostatic Forces ◽  
Mode Superposition Method ◽  
Electrostatic Mems ◽  
Micro Cantilever

For MEMS devices actuated by electrostatic force, unexpected failure modes can be hardly predicted when the electrostatic force coupled with the shock. A response model is established when a micro cantilever subjected to electrostatic force and mechanical shock. First, based on the theory of transverse forced vibration in vibration mechanics, the equation of motion under shock and electrostatic fore is presented. Then the reduced order model is gained after simplifying by mode superposition method. The computing results indicate that: the shock amplitude and duration are the key factors to affect the reliability of the device; the shock load and electrostatic forces make the threshold voltage much lower than the anticipated value. The micro cantilever may collapse to the substrate even at a voltage far lower than the pull-in voltage. This early dynamic pull-in instability may cause some failures such as short circuit, adhesion or collision damage.

Stiction Failure Mechanisms of the Micromachined Electrostatic Comb-Drive Structures

2011 ◽  
Vol 80-81 ◽  
pp. 850-854
Author(s):  
Yi Shen Xu ◽  
Ji Hua Gu ◽  
Zhi Tao
Keyword(s):  
Failure Modes ◽  
Failure Mechanisms ◽  
Mems Devices ◽  
Comb Drive ◽  
Interfacial Forces ◽  
Restoring Forces ◽  
Critical Investigation

Stiction is one of the most important and almost unavoidable problems in MEMS, which usually occurs when the restoring forces of the microstructures are unable to overcome the interfacial forces. Stiction could compromise the performance and reliability of the MEMS devices or may even make them malfunction. One of the pivotal process of advancing the performance and reliability of MEMS is to comprehend the failure modes and failure mechanisms of these microdevices. This article provides a critical investigation on the stiction failure mechanisms of the micromachined electrostatic comb-drive structures, which is significant to improve the reliability of microdevices, especially for microfilters, microgrippers, microaccelerometers, microgyroscopes, microrelays, and so on.

Failure Modes Model of MEMS Accelerometers Based on Neural Networks

2008 ◽  
Author(s):  
Yanping Bai ◽  
Ping An ◽  
Yilong Hao
Keyword(s):  
Neural Networks ◽  
Failure Modes ◽  
Late Phase ◽  
Primary Sources ◽  
Bp Network ◽  
Bp Networks ◽  
Mems Accelerometers ◽  
Perception Model ◽  
Hidden Layer ◽  
Training Success

Fabrication of a MEMS system involves design, testing, packaging and reliability related issues. However, reliability issues that are discovered at a late phase may cause major delays in the product development going together with high costs. In this paper we study the failure modes and Mechanisms of MEMS accelerometers products and present the classification modeling of failure modes based on neural networks. In ours MEMS accelerometers, there are six failure mechanisms that have been found to be the primary sources of failure nodes. We introduce nonlinear BP network with a hidden layer and linear perception to classify for MEMS accelerometers products. Classification results show that nonlinear BP network seem to be most appropriate to approach the problem of failure modes classification than linear perception. BP neural network is capable of learning the intrinsic relations of the patterns with which they were trained. For all experiments results, the training success of rate is 100% for both methods. BP networks obtained a high forecast success of rate of over 99.5%. The linear perception model obtained a success of rate of over 95.5%. We also analyze the technology stability of MEMS products.

scholarly journals Reducing the Hygroscopic Swelling in MEMS Sensor using Different Mold Materials

2020 ◽  
Vol 10 (1) ◽  
pp. 494
Author(s):  
Pinki Kumari ◽  
Kuldeep Singh ◽  
Anuj Singal
Keyword(s):  
Performance Analysis ◽  
Pressure Sensor ◽  
Ceramic Mold ◽  
Mems Devices ◽  
Challenging Problem ◽  
Microelectromechanical System ◽  
Saturation Concentration ◽  
Mems Sensor ◽  
Hygroscopic Swelling

Today, Hygroscopic swelling is one of the biggest challenging problem of Epoxy mold compound (EMC) in packaging with Microelectromechanical system (MEMS) devices. To overcome this hygroscopic swelling problem of EMC and guard the devices, MEMS devices are molded in this paper with different Mold Compound (MC) i.e. titanium and ceramic etc. during their interconnection with the board. Also, a comparatively performance analysis of this various mold compound with MEMS pressure sensor has been studied in this paper at 60% humidity, 140 mol/m<sup>3</sup> saturation concentration and 25 <sup>o</sup>C. It was observed that hygroscopic swelling does not take place in the titanium mold compound. But, titanium is very costly so we have to consider something cheaper material i.e. ceramic in this paper. The Hygroscopic swelling in Ceramic Mold Compound after 1 year is nearly 0.05mm which is very less than epoxy.

Present and Future Applications of MEMS for Automotive Industry

2014 ◽  
Vol 2014 (DPC) ◽  
pp. 001851-001892
Author(s):  
Thibault Buisson
Keyword(s):  
High Pressures ◽  
Failure Mechanisms ◽  
Extreme Environments ◽  
Pressure Sensors ◽  
Harsh Environments ◽  
Fe Model ◽  
Potential Candidate ◽  
Mems Devices ◽  
Technology Modeling ◽  
Sintered Ag

MEMS are found in many applications, ranging from large volume consumer applications such as mobile phones to specific high end devices for defense or space. MEMS market will continue to see steady, sustainable double digit growth for the next six years, with 20% compound average annual growth in units and 13% growth in revenues, to become a $21 billion market by 2017. Automotive applications represent today around 20% of the MEMS market in revenue and are expected to see a 5.4 % growth in the next five years, which means that the penetration of MEMS devices in this market will remain limited. Today, MEMS family in cars is mainly represented by pressure sensors for Tire Pressure Monitoring and Manifold Air Pressure sensing, and accelerometers in ABS and stabilization systems. These applications are reaching maturity, which mean that their growth gets directly related to the car sales. To find new growth opportunities, system integrators have been trying to develop new MEMS based systems to enhance safety, comfort and reduce pollution and energy consumption. The presentation will show emerging applications and the challenges they face from a technical and a market point of view. Diverse electronic packages operate under exceptionally harsh environments, which require extended lifetimes, presenting a significant challenge for the microelectronics community. Operating temperatures above 200 °C together with high pressures, vibrations and potentially corrosive environments implies that some technical issues regarding the development of electronic systems that will operate at such high temperature remain. Technology based on sintering has been recently emerging for power modules, capable of withstanding up to 300 °C. Sintered Ag is one potential candidate for die attachment for extreme environments. The application of sintered Ag has proven already to significantly increase the lifetime of interconnects when compared to solder joints. Both characterization of the failure mechanisms as well as prediction of product life in such environments is critical to the long term reliability of these devices. The present work aims to develop an understanding of how and why attach materials for Si dies degrade/fail under harsh environments by investigating sintered Ag material. New failure mechanisms will become dominant in the sintered Ag technology. Modeling helps understanding how a particular system behaves if conditions are altered. Thus, a 2D axis symmetric die attach model, commonly used to represent microelectronic package assemblies, was generated using Ansys Workbench. The FE-model provided a good understanding of the effect of single parameter variation of different leadframe materials (K64, K14, and FeNi42), chip height, sintered Ag and metallization thicknesses. The FE-model provided a rapid assessment of delamination, cracking and other defects and their location within the package. The effect of the sintered Ag thickness on the plastic strain was only slight. Furthermore, on the chip side, the local thermal mismatch between the Si die and the sintered Ag was the most important loading factor. Also, thicker chips generated higher stresses. Further analysis of simulation and experiment of sintered Ag interconnects will give more insight on dominating failure mechanisms, and help reduce failure risks.

KL Transform and Neural-Net Based Framework for Failure Modes Classification in Electronics Subjected to Mechanical-Shock

2011 ◽  
Author(s):  
Pradeep Lall ◽  
Prashant Gupta ◽  
Kai Goebel
Keyword(s):  
Failure Mode ◽  
Failure Modes ◽  
Learning Algorithm ◽  
Back Propagation ◽  
Feature Space ◽  
System Level ◽  
Neural Net ◽  
Mechanical Shock ◽  
Time Frequency ◽  
Damage Initiation

Electronic systems under extreme shock and vibration environments including shock and vibration may sustain several failure modes simultaneously. Previous experience of the authors indicates that the dominant failure modes experienced by packages in a drop and shock frame work are in the solder interconnects including cracks at the package and the board interface, pad cratering, copper trace fatigue, and bulk-failure in the solder joint. In this paper, a method has been presented for failure mode classification using a combination of Karhunen Loe´ve transform with parity-based stepwise supervised training of a perceptrons. Early classification of multiple failure modes in the pre-failure space using supervised neural networks in conjunction with Karhunen Loe´ve transform is new. Feature space has been formed by joint time frequency analysis. Since the cumulative damage may be accrued under repetitive loading with exposure to multiple shock events, the area array assemblies have been exposed to shock and feature vectors constructed to track damage initiation and progression. Error Back propagation learning algorithm has been used for stepwise parity of each particular failure mode. The classified failure modes and failure regions belonging to each particular failure modes in the feature space are also validated by simulation of the designed neural network used for parity of feature space. Statistical similarity and validation of different classified dominant failure modes is performed by multivariate analysis of variance and Hoteling’s T-square. The results of different classified dominant failure modes are also correlated with the experimental cross sections of the failed test assemblies. The methodology adopted in this paper can perform real-time fault monitoring with identification of specific dominant failure mode and is scalable to system level reliability.

scholarly journals A Review on Key Issues and Challenges in Devices Level MEMS Testing

2016 ◽  
Vol 2016 ◽  
pp. 1-14 ◽  
Author(s):  
Muhammad Shoaib ◽  
Nor Hisham Hamid ◽  
Aamir Farooq Malik ◽  
Noohul Basheer Zain Ali ◽  
Mohammad Tariq Jan
Keyword(s):  
Failure Modes ◽  
Microelectromechanical Systems ◽  
Operating Conditions ◽  
Mems Devices ◽  
Test Technique ◽  
Parallel Testing ◽  
Test Systems ◽  
Key Issues ◽  
Mems Testing ◽  
The Cost

The present review provides information relevant to issues and challenges in MEMS testing techniques that are implemented to analyze the microelectromechanical systems (MEMS) behavior for specific application and operating conditions. MEMS devices are more complex and extremely diverse due to the immersion of multidomains. Their failure modes are distinctive under different circumstances. Therefore, testing of these systems at device level as well as at mass production level, that is, parallel testing, is becoming very challenging as compared to the IC test, because MEMS respond to electrical, physical, chemical, and optical stimuli. Currently, test systems developed for MEMS devices have to be customized due to their nondeterministic behavior and complexity. The accurate measurement of test systems for MEMS is difficult to quantify in the production phase. The complexity of the device to be tested required maturity in the test technique which increases the cost of test development; this practice is directly imposed on the device cost. This factor causes a delay in time-to-market.

Enabling Low Temperature Copper Bonding with an Organic Monolayer

2009 ◽  
Vol 74 ◽  
pp. 133-136 ◽  
Author(s):  
Ang Xiao Fang ◽  
Jun Wei ◽  
Chen Zhong ◽  
Wong Chee Cheong
Keyword(s):  
Bonding Temperature ◽  
Copper Surface ◽  
Mems Devices ◽  
Ambient Conditions ◽  
Copper Surfaces ◽  
Organic Monolayer ◽  
Metallurgical Bonding ◽  
Alternative Approach ◽  
Copper Material ◽  
Joint Integrity

Typically, copper material is used as a bonding material in MEMs devices for its excellent mechanical, electrical and hermetic properties. Direct copper bonding, however, requires high temperature (>300°C) to forge a bond due to the oxidative nature of copper. In this study, using an alternative approach based on an organic monolayer coating, we demonstrate metallurgical bonding between two copper surfaces under ambient condition at low bonding temperature below 140°C, while maintaining reliable mechanical joint integrity of 50MPa. This monolayer is believed to behave as a passivation layer, protecting the copper surface against oxidation under ambient conditions. In contrast to a bulk oxide layer, this layer can be easily displaced during mechanical deformation at the bonding interface.

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