Mechanical Shock Testing Research Articles

Behavior of Polymeric Substrates and Sintered Silver Printed Hybrid Electronic Assemblies Subject to Extreme Acceleration Levels and Elevated Temperatures

Abstract This paper focuses on the response of printed hybrid electronic (PHE) assemblies with polymeric substrates and additively manufactured sintered silver electrical traces subject to extreme mechanical shocks (up to 100,000 g) and high temperatures (up to 150 °C). The substrates are hemispherical domes of injection-molded polycarbonate and polysulfone thermoplastics. Trace deposition onto the domes is accomplished by a novel process that combines conventional milling with extrusion printing to recess silver traces and dielectric insulation within the surface of the substrate. Mechanical shock testing is performed using an accelerated-fall drop tower equipped with a dual mass shock amplifier (DMSA) able to generate accelerations from 10,000 g up to 100,000 g with pulse durations of ∼0.05–0.1 ms and impact velocities of 6.5–20.5 m/s. Specimen performance is characterized by electrical and physical testing before and after testing. While polycarbonate domes survive multiple drops at all acceleration levels and temperatures, they are sensitive to heat and susceptible to warping and structural deformation at 150 °C which can compromise trace performance. Polysulfone domes can survive these temperatures without issue, but are less shock resistant and only survive 3–4 drops at 100,000 g (compared to 30+ for polycarbonate domes). Trace resistance is used as a metric to assess trace performance. All traces exhibit progressive long-term degradation over the course of multiple shocks, followed by instantaneous discontinuity during the final shock event. Trace failure (defined as the doubling of static trace resistance) occurs at ∼105–106 J/kg cumulative impact energy for all acceleration levels.

Evaluation of the mechanical shock testing standards for electric vehicle batteries

The safety of Li-ion batteries (LIB) has become an important issue with the continuously increased use of electric vehicles (EV) in the world. In a survivable vehicle crash, when the vehicle needs to maintain structural integrity, crash-induced shock may damage EV's LIB. Therefore, an evaluation of commonly used mechanical shock test standards for EV battery module and pack is performed in this study against the crash-induced shock signals collected from National Highway Traffic Safety Administration (NHTSA) New Car Assessment Program (NCAP) tests. Various shock analysis methods including signal characteristics in time domain, power spectral density (PSD) and shock response spectrum (SRS) in frequency domain, and the acceleration/velocity-change diagram are used for the evaluation. It is found that most peak accelerations of NCAP shock signals significantly exceed the peak accelerations specified in shock testing standards. Crash-induced shocks cannot be fully represented by the half-sine pulse adopted in shock testing standards. In both time and frequency domains, the existing shock testing standards generally underestimate the severities of the crash-induced shocks, and therefore, are non-conservative. It also shows that the correct selection of a filter for the processing of the original crash-induced shock signal is crucial for the specification of EV battery shock environment and shock response analyses. The results obtained in this research can support the development of more reliable shock testing standards for EV batteries.

Mechanical shock test simulation analysis of butterfly valves developed for the naval defense industry and evaluation of real test and production data

The main purpose of this study is to investigate the mechanical shock behavior and develop the shock resistance of widely preferred butterfly valves for navy defense industries by handling the real test results with computer aided design and simulation programs. The 2D and 3D drawings were realized by using solid modeling and design programs. Mechanical analyzes to determine the mechanical strength of the specimens were carried out with the finite element analysis method by using structural simulation program. Mechanical shock test simulations were carried out by with shock response spectrum analysis. Solidification, filling-time–temperature analyzes, and simulation studies of inner stresses caused by micro and macro shrinkages were performed by using the casting simulation program. Comparisons of virtual tests simulated in computer environment with real tests were done in shock test setup. Products made of bronze were preferred due to the high corrosion resistance and the desire to be a useful research article that can respond to common applications in the defense industry. Virtual shock test simulation and real shock tests were performed according to the MIL STD 810 standard. The shock test results observations showed that by revising the design with a safety factor of 18% on the specimen, it was ensured that the product could pass the mechanical shock test even at an acceleration of 4000 m/s2. Then material become safe to use. With the use of a three-way feeder in the production of the reinforced design the difference in net weight from 19% has been reduced to 12%, while the production time has been improved by 22%.

Discussion of Mechanical Shock Test Stress for Ultra-large-scale CMOS Image Sensors

The ultra-large-scale CMOS image sensors are significantly different from the traditional CMOS image sensors in terms of pixel size, chip size and structure. CMOS image sensors generally come with an optical window structure that is sealed to the ceramic housing by means of adhesive. The optical window material is generally sapphire, and the larger the image element size, the larger the required glass optical window area. Ultra-large size CMOS image sensors in the package before the general optical window thickness, parallelism, light window average transmittance assessment. The object of mechanical impact test assessment is the CMOS image sensor optical window structure and capping process. The paper mainly discusses the typical failure cases of ultra-large-scale CMOS image sensors on the basis of the applicability of mechanical shock test standards, and investigates how to define the mechanical shock test stress from simulation, limit test and the requirements by users. This paper provides the qualification assessment basis of mechanical shock for newly developed products.

Robustness and performance evaluation of TDLAS sensor for scramjet intake

A single-body typed TDLAS sensor was developed, and its robustness and performance were experimentally evaluated under harsh thermal and mechanical environments which could be formed in scramjet intake. To confirm integrity and operability of the TDLAS sensor in the harsh thermal environments, high-thermal gradient, long-duration heating, and aero-heating tests were conducted. The high-thermal gradient, long-duration heating, and aero-heating tests were performed using high-temperature torch, furnace, and supersonic wind tunnel, respectively. In addition, vibration, mechanical shock, and acceleration tests were performed to analyze the durability and operating performance of the TDLAS sensor in the harsh mechanical environments. The vibration/mechanical shock, and acceleration tests were carried out using shaker and centrifuge, respectively. The TDLAS sensor did not experience any damage and had a stability of signal measurement under these severe thermal and mechanical environments. The experimental test results showed that the single-body TDLAS sensor in this paper could be used in the extreme thermal and mechanical conditions which could be formed in the scramjet intake.

Thermally/mechanically robust anodic aluminum oxide (AAO) microheater platform for low power chemoresistive gas sensor

The semiconductor metal oxide gas sensors are getting high attention owing to their high sensitivities and fast responses. They require high temperature for the reaction with target gases, and suspended silicon membrane microheaters are typically used to reduce the heating power consumption. However, they have low durability for long-term uses, and high probability of fracture by thermal stress or mechanical impact. In this study, as an alternative to the silicon membrane microheater, anodic aluminum oxide (AAO)-based microheater platform gas sensor was fabricated for low power consumption and high thermal/mechanical stabilities. Nanoscale air gaps of the AAO substrate reduce the heat loss transferred to the substrate. Therefore, AAO-based microheater platforms do not require suspended structures sustained by very thin bridges, which dramatically enhances thermal/mechanical stabilities. The temperature of fabricated microheater platform reached to 250 °C by a heating power of 27.4 mW. The excellent thermal/mechanical stabilities of the AAO-based microheater platforms were verified by cyclic on-off and mechanical shock test. The pulsed heating operation was adopted, and it reduced the heating power consumption to 9 mW. The fabricated AAO-based gas sensors showed much higher responses to NO2 gas compared to the SiO2 membrane-based gas sensors.

Fabrication of racetrack-type double-pancake coils using 2G tapes and online mechanical shock test

Racetrack-type double-pancake (DP) coil was wound successfully with YBCO high-temperature superconducting tapes. The characteristics and impact resistance of the coils were investigated. The characteristics of the dependent DP coil did not change after applying different acceleration values in the X and Y directions. With the increasing value of acceleration (i.e., up to 30 g in X direction and 15 g in Y direction), the voltage of the racetrack coil remained unaffected. Based on the tests, three racetrack-type coils were wound and assembled in a certain sequence to form a magnet. The optimum temperature range for impregnating the magnet was confirmed by investigating the viscosity and shear stress of paraffin at different temperatures. After the assembly of the coils, the magnet was vacuum impregnated with liquid paraffin. Subsequently, the magnet was fixed in a Dewar that was filled with liquid nitrogen to cool the coils. The magnet was energized after cooling down. Then, the mechanical shock resistance of the coils in Dewar was tested dynamically. Results showed that the coil characteristics did not change after paraffin impregnation. The voltage and magnetic field were almost unaffected by the dynamic increase in the acceleration value to up to 30 g every 5 g interval in the X direction. Thus, these methods of construction and paraffin impregnation and fixtures can be used in the racetrack-type magnet.

Thermal and Mechanical Shock Testing of a Brick Wall and A Polystyrene Wall

Polystyrene is one of the many novel materials being developed today. The goal of our research is to demonstrate that polystyrene is a good construction material in the El Oued region of Southeast Algeria. It can also be a strong rival for other building materials like brick. The results of our research, particularly in thermal testing, are very promising. Polystyrene is a better insulator than brick; the temperature of the polystyrene chamber varies between 26 and 27°C, whereas the temperature of the brick chamber varies between 36 and 37 °C. Polystyrene has a 5 times mechanical impact compared to brick. Despite its lack of availability in the region's markets, polystyrene is a strong rival to other materials such as brick.

Fabrication of Racetrack-Type Double-Pancake Coils Using 2g Tapes and Online Mechanical Shock Test

Fabrication of Racetrack-Type Double-Pancake Coils Using 2g Tapes and Online Mechanical Shock Test

Prediction and adjustment method for shock response spectrum in mechanical impact type shock test for spacecraft instrument

Prediction and adjustment method for shock response spectrum in mechanical impact type shock test for spacecraft instrument

Soldering of Passive Components Using Sn Nanoparticle Reinforced Solder Paste: Influence on Microstructure and Joint Strength.

In this study, the effects of adding Sn nanopowder (particle size < 150 nm) to three solder pastes SAC3-X(H)F3+, SCAN-Ge071-XF3+, and water washable WW50-SAC3 are evaluated regarding microstructure, morphology, joint strength, and electrical resistance. The nanopowder was added at a rate of 10% by weight and then mechanically mixed until homogenous solder paste was obtained. The results showed that the addition of Sn nanoparticles resulted in homogenous bond formation for SAC-3 and SCAN, while voids and bubbles formation slightly increased within the joint interface for the water washable solder paste. The SCAN + Sn nano reinforced solder paste showed increased variation of joint strength from 12.6 to 39.9 N, while the water washable + Sn nanopowder reinforced solder paste showed less variability in joint strength from 17.3 to 33.9 N. Both sets of solder paste with and without Sn nano reinforced solder paste showed a reliable quality joint under mechanical shock testing after six shocks in six milliseconds with an 87.1 ms pulse duration. The results showed that Sn nanoparticles resulted in a small resistance change, while RDC values (in mΩ) slightly decreased for SAC and increased for SCAN and further increases for water washable solder paste.

A Study on the Reliability Test of a Lithium Battery in Medical Electric Wheelchairs for Vulnerable Drivers

There are test items for lithium-ion batteries in reliability testing for automobiles and motorcycles, but equivalent test items have not yet been established for mobility scooters (also known as electronic wheelchairs). To evaluate the lithium-ion battery pack or system mounted on a mobility scooter, it is necessary to test vibrations and mechanical shock while driving, independent of tests for the lithium-ion battery cells. In an effort to meet this need, test profiles were established for mobility scooter lithium-ion batteries by performing on-road driving tests and mechanical shock tests. The proposed test profiles were validated using robust statistics and proficiency statistics. The safety of the test profiles was tested in a nationally accredited testing laboratory. As a result, the lithium-ion battery mounted on the mobility scooter was found to have incurred no leakage, short circuit, burst, or explosion. The vibration and mechanical shock test profiles proposed in this study are expected to serve as basis data for establishing standards for mobility scooter safety and reliability.

Risk assessment for bonding wires instantaneous touch in high density packaging

This paper studies the risk assessment method of bonding wires instantaneous touch during mechanical shock tests. Under-damping vibration motion is used to describe bonding wire’s motion state with mechanical shock loads. The influence of loop span, wire diameter and loop height on the amplitude and frequency of wire’s vibration are analysed based on the results of finite element analysis and design of experiments. The detection experiments of bonding wire’s instantaneous touch are conducted to get the vibration amplitude and vibration damping coefficient. Then, the risk assessment method is built by the analysis of simulation data and experiments data to evaluate the probability of adjacent wire’s transient touch under mechanical shock load.

Evaluation of digital micromirror devices for use in space-based multiobject spectrometer application

The astronomical community continues to be interested in suitable programmable slit masks for use in multi-object spectrometers (MOSs) on space missions. There have been ground-based MOS utilizing digital micromirror devices (DMDs) and they have proven to be highly accurate and reliable instruments. This paper summarizes the results of a continuing study to investigate the performance of DMDs under conditions associated with space deployment. This includes the response of DMDs to radiation, to the vibration and mechanical shock loads associated with launch, and the operability of DMD under cryogenic temperatures. The optical contrast ratio and a study of the long-term reflectance of a bare device have also been investigated. The results of the radiation testing demonstrate that DMDs in orbit would experience negligible heavy-ion induced single event upset (SEU) rate burden, we predict SEU rate of 5.6 micromirrors per 24 hours. Vibration and mechanical shock testing was performed according to the NASA General Environmental Verification Standard (GEVS), no mirrors failed in the devices tested. The results of low temperature testing suggest that DMDs are not affected by the thermal load and operate smoothly at temperatures at least as low as 78 K. The reflectivity of a bare DMD did not measurably change even after being exposed to ambient conditions over a period of 13 months. The measured contrast ratio (on state vs off state of the DMD micromirrors) was greater than 6000/:1 when illuminated with an f/4 optical beam. Overall, DMDs are extremely robust and promise to provide a reliable alternative to micro shutter arrays (MSA) to be used in space as remotely programmable slit masks for MOS design.

CAE Method for Evaluating Mechanical Performance of Battery Packs under Mechanical Shock Testing

CAE Method for Evaluating Mechanical Performance of Battery Packs under Mechanical Shock Testing

How Mitigation Techniques Affect Reliability Results for BGAs

Abstract Since 2006 RoHS requirements have required lead free solders to take the place of tin-lead solders in electronics. The problem is that in some environments the lead free solders are less reliable than the older tin-lead solders. One of the ways to solve this problem is to corner stake, edge bond or underfill the components. When considering what mitigation technique and material to use, the operating conditions must be characterized. The temperature range is important when selecting a material to use since the glass transition temperature (Tg) and coefficient of thermal expansion (CTE) are important properties. If improperly chosen, the mitigation material can cause more failures than an unmitigated component. This study focused on 208 I/O BGAs on a 4 layer FR4 board. There were three solders tested; two lead free (SAC305 and SN100C) and one leaded (SnPb). Three mitigation techniques were tested: corner staking, edge bonding, and underfilling. Each of these techniques had two mitigation materials tested. One material was reworkable and the other was not. The boards were subjected to mechanical shock testing and sinusoidal vibration testing until failure. The results of the testing show that no one mitigation technique is best for all of the conditions tested. The same is true for the mitigation material. The best choice of mitigation technique and material is application dependent.

Stochastic shock response spectrum decomposition method based on probabilistic definitions of temporal peak acceleration, spectral energy, and phase lag distributions of mechanical impact pyrotechnic shock test data

Most of the times pyrotechnic shock design and test requirements for space systems are provided in Shock Response Spectrum (SRS) without the input time history. Since the SRS does not describe the input or the environment, a decomposition method is used to obtain the source time history. The main objective of this paper is to develop a decomposition method producing input time histories that can satisfy the SRS requirement based on the pyrotechnic shock test data measured from a mechanical impact test apparatus. At the heart of this decomposition method is the statistical representation of the pyrotechnic shock test data measured from the MIT Lincoln Laboratory (LL) designed Universal Pyrotechnic Shock Simulator (UPSS). Each pyrotechnic shock test data measured at the interface of a test unit has been analyzed to produce the temporal peak acceleration, Root Mean Square (RMS) acceleration, and the phase lag at each band center frequency. Maximum SRS of each filtered time history has been calculated to produce a relationship between the input and the response. Two new definitions are proposed as a result. The Peak Ratio (PR) is defined as the ratio between the maximum SRS and the temporal peak acceleration at each band center frequency. The ratio between the maximum SRS and the RMS acceleration is defined as the Energy Ratio (ER) at each band center frequency. Phase lag is estimated based on the time delay between the temporal peak acceleration at each band center frequency and the peak acceleration at the lowest band center frequency. This stochastic process has been applied to more than one hundred pyrotechnic shock test data to produce probabilistic definitions of the PR, ER, and the phase lag. The SRS is decomposed at each band center frequency using damped sinusoids with the PR and the decays obtained by matching the ER of the damped sinusoids to the ER of the test data. The final step in this stochastic SRS decomposition process is the Monte Carlo (MC) simulation. The MC simulation identifies combinations of the PR and decays that can meet the SRS requirement at each band center frequency. Decomposed input time histories are produced by summing the converged damped sinusoids with the MC simulation of the phase lag distribution.

How Mitigation Techniques Affect Reliability Results for BGAs

Since 2006 RoHS requirements have required lead free solders to take the place of tin-lead solders in electronics. The problem is that in some environments the lead free solders are less reliable than the older tin-lead solders. One of the ways to solve this problem is to corner stake, edge bond or underfill the components. When considering what mitigation technique and material to use, the operating conditions must be characterized. The temperature range is important when selecting a material to use since the glass transition temperature (Tg) and coefficient of thermal expansion (CTE) are important properties. If improperly chosen, the mitigation material can cause more failures than an unmitigated component. This study focused on 208 I/O BGAs on a 4 layer FR4 board. There were three solders tested; two lead free (SAC305 and SN100C) and one leaded (SnPb). Three mitigation techniques were tested: corner staking, edge bonding, and underfilling. Each of these techniques had two mitigation materials tested. One material was reworkable and the other was not. The boards were subjected to mechanical shock testing and sinusoidal vibration testing until failure. The results of the testing show that no one mitigation technique is best for all of the conditions tested. The same is true for the mitigation material. The best choice of mitigation technique and material is application dependent.

I/O Printed Circuit Board Assemblies; Recent Learning in Mechanical Stress Analysis, Verification Testing, and Post-test Analysis Techniques and Results

Recent high-end server designs have included new Input / Output (I/O) printed circuit board (PCB) assemblies consisting of a variety of form factors, electronic design layouts, and packaging assembly characteristics. To insure the required functional and reliability aspects are established and maintained, new mechanical analysis and verification testing techniques have been recently devised. A description of the design application set, the analysis tools and techniques applied, and the verification testing completed, including the associated measurement techniques as well as post-testing analysis methods and results are presented. Also included are the recent PCB raw card characterization efforts whose results have been applied as material property inputs to the analysis to improve analytical-to-empirical correlation. Included within the application set are both the use of custom designed cards as well as industry standard, original equipment manufacturer (OEM) cards that are packaged within custom enclosures. Given packaged and unpackaged (i.e., as installed in a higher-level rack system assembly) fragility testing requirements, new analysis techniques exploiting the capabilities of LS-DYNA have been used to provide a predictive means to support both initial as well as iterative design levels. In addition, these analysis results are also used to identify locations for measurement sensor placement employed during mechanical verification testing. Thermal shock and mechanical shock and vibration verification testing details and results are provided describing the conditions applied to simulate assembly shipping conditions, both as packaged as well as in situ to the higher-level of assembly. Included with this is a discussion with respect to post-test analysis techniques and results, including the use of both microscopic cross-section analysis as well as dye-pry assessments. Concluding, continued and future activities are described as “best practices” for the application of this methodology as part of the end-to-end development process.

Increased Resistance to Mechanical Shock of Metallic Materials by Metal-Ceramic Surface Coatings

In the last time, material engineering in lately developed the design and processing technology of materials in well-defined goals. Thus, they designed and achieved the metal alloys for use in strong fields required mechanical shock using methods of surface engineering. In this direction, we have developed very superficial deposition techniques by thermal spray of ceramic and metal powders, both for hard coating and to protect surfaces in refractory environments. In a controlled manner, can form new structures, which leads to an improvement in the tribological properties of the coatings obtained. In this paper are described experimental results obtained after the tests of resistance to mechanical shock testing of metal-ceramic coatings on forged titanium support. We analyzed the behavior of thermal deposited layers of ZrO2 stabilized with 8% Y2O3 and Al2O3 after applying mechanical shock test and scratch test. These materials were analyzed in terms of structural, of mechanical properties and adhesion of the surface layers using electron microscopy, X-ray diffraction, Charpy device, CETR UMT-2 tribometer. The results showed that the materials investigated have a stratified columnar structure, shows lamellar and intra - lamellar cracks and pores formed between neighbor "splat's". From microscopic analysis, after these tests, it was observed that the thermal deposited layers were not separated and there was a fingerprint on their surface. The experimental results show that the new structures obtained presents much better mechanical properties compared to the material, forged titanium, no deposit.