Identification of failure modes in portable electronics subjected to mechanical-shock using supervised learning of damage progression

2011 ◽  
Author(s):  
Pradeep Lall ◽  
Prashant Gupta ◽  
Kai Goebel
Keyword(s):  
Supervised Learning ◽  
Failure Modes ◽  
Mechanical Shock ◽  
Portable Electronics ◽  
Damage Progression

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.

The Mechanical Reliability of a Commercial MEMS Microphone

2013 ◽  
Vol 662 ◽  
pp. 551-555
Author(s):  
Wen Xiao Fang ◽  
Qin Wen Huang
Keyword(s):  
Recent Work ◽  
Random Vibration ◽  
Failure Modes ◽  
Mechanical Tests ◽  
Vibration Test ◽  
Mechanical Shock ◽  
Mechanical Reliability ◽  
Constant Acceleration ◽  
Shock Test ◽  
Mems Microphone

This paper describes our recent work on the mechanical reliability of a commercial MEMS microphone by performing three mechanical tests, i.e. a constant acceleration test, a mechanical shock test, and a random vibration test, according to the standard of Mil-Std-883. We find that, the studied MEMS part of the microphone can survive a stress limit above 20000g. Two failure modes, i.e. the breaking of diaphragm and the backplate and the delamination of the electrode from the backplate are revealed in the three tests.

Impact-Induced Damage Progression in 2-D and 3-D Woven Composite Systems

2001 ◽  
Author(s):  
Jared N. Baucom ◽  
Mohammed A. Zikry
Keyword(s):  
Failure Modes ◽  
Surface Condition ◽  
Woven Composites ◽  
Woven Composite ◽  
Additional Energy ◽  
3 Dimensional ◽  
Damage Progression ◽  
Glass Fiber Reinforced ◽  
The Difference ◽  
The Impact

Abstract The role of fabric architecture on the impact-induced damage progression and perforation resistance of glass-fiber reinforced vinyl-ester resin panels under dynamic loading condition is investigated. Three fabric preforms are considered: a 2-dimensional, plain-woven laminate, a commercially available biaxially reinforced warp-knit, and a 3-dimensional, orthogonally woven preform. Composite samples are subjected to multiple impacts, until perforation, and the impactor position and acceleration are monitored throughout each event, resulting in a visualization of dynamic energy dissipation. Failure modes of the various material systems are characterized. The radial damage expansion was smallest for the 2-d laminate, larger for the biaxially-reinforced warp-knit, and largest for the 3-d orthogonal woven composite. The 3-d composite survived more hits and dissipated more total energy than the other systems. The difference may be due to the additional energy absorption mechanisms, which involve the crimped portion of z-tows in the 3-d composites. This implies that failure may be controlled by manipulation of the properties of the z-tows. It also indicates that the surface condition of 3-d orthogonally woven composites can strongly affect the progression of impact-induced damage.

Constitutive Behavior of SAC Leadfree Alloys at High Strain Rates

2011 ◽  
Author(s):  
Pradeep Lall ◽  
Sandeep Shantaram ◽  
Mandar Kulkarni ◽  
Geeta Limaye ◽  
Jeff Suhling
Keyword(s):  
Constitutive Model ◽  
Solder Alloy ◽  
Failure Modes ◽  
High Strain ◽  
Image Correlation ◽  
Constitutive Behavior ◽  
Strain Rates ◽  
Mechanical Shock ◽  
High Strain Rates ◽  
Test Technique

Electronic products are subjected to high G-levels during mechanical shock and vibration. Failure-modes include solder-joint failures, pad cratering, chip-cracking, copper trace fracture, and underfill fillet failures. The second-level interconnects may be experience high-strain rates and accrue damage during repetitive exposure to mechanical shock. Industry migration to leadfree solders has resulted in proliferation of a wide variety of solder alloy compositions. Few of the popular tin-silver-copper alloys include Sn1Ag0.5Cu and Sn3Ag0.5Cu. The high strain rate properties of leadfree solder alloys are scarce. Typical material tests systems are not well suited for measurement of high strain rates typical of mechanical shock. Previously, high strain rates techniques such as the Split Hopkinson Pressure Bar (SHPB) can be used for strain rates of 1000 per sec. However, measurement of materials at strain rates of 1–100 per sec which are typical of mechanical shock is difficult to address. In this paper, a new test-technique developed by the authors has been presented for measurement of material constitutive behavior. The instrument enables attaining strain rates in the neighborhood of 1 to 100 per sec. High speed cameras operating at 300,000 fps have been used in conjunction with digital image correlation for the measurement of full-field strain during the test. Constancy of cross-head velocity has been demonstrated during the test from the unloaded state to the specimen failure. Solder alloy constitutive behavior has been measured for SAC105, and SAC305 solders. Constitutive model has been fit to the material data. Samples have been tested at various time under thermal aging at 25°C and 125°C. The constitutive model has been embedded into an explicit finite element framework for the purpose of life-prediction of leadfree interconnects. Test assemblies has been fabricated and tested under JEDEC JESD22-B111 specified condition for mechanical shock. Model predictions have been correlated with experimental data.

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.

Addressing Failure Analysis Challenges in Advanced Packages and MEMS using a Novel Phase and Darkfield X-Ray Imaging System

2020 ◽  
Author(s):  
S.H. Lau ◽  
Sheraz Gul ◽  
Guibin Zan ◽  
David Vine ◽  
Sylvia Lewis ◽  
...  
Keyword(s):  
Failure Modes ◽  
Imaging System ◽  
Dark Field ◽  
Organic Substrates ◽  
Mechanical Shock ◽  
X Ray ◽  
X Ray Imaging ◽  
X Ray Computed ◽  
2D And 3D ◽  
Non Destructive

Abstract Currently gaps in non-destructive 2D and 3D imaging in PFA for advanced packages and MEMS exist due to lack of resolution to resolve sub-micron defects and the lack of contrast to image defects within the low Z materials. These low Z defects in advanced packages include sidewall delamination between Si die and underfill, bulk cracks in the underfill, in organic substrates, Redistribution Layer, RDL; Si die cracks; voids within the underfill and in the epoxy. Similarly, failure modes in MEMS are often within low Z materials, such as Si and polymers. Many of these are a result of mechanical shock resulting in cracks in structures, packaging fractures, die adhesion issues or particles movements into critical locations. Most of these categories of defects cannot be detected non-destructively by existing techniques such as C-SAM or microCT (micro x-ray computed tomography) and XRM (X-ray microscope). We describe a novel lab-based X-ray Phase contrast and Dark-field/Scattering Contrast system with the potential to resolve these types of defects. This novel X-ray microscopy has spatial resolution of 0.5 um in absorption contrast and with the added capability of Talbot interferometry to resolve failure issues which are related to defects within organic and low Z components.

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.

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