Random Vibration Test Research Articles

Failure Analysis and Modeling of Solder Joints in BGA Packaged Electronic Chips

In this article, the random vibration test and finite-element simulation analysis of SAC305 solder joints in BGA packaged electronic chips were carried out. A failure model for BGA solder joints was established based on the life data. And vulnerable parts in electronic chips were analyzed. First, the random vibration test was conducted. Second, a lognormal distribution model of solder joints by means of the life data was established and analyzed based on the fracture mechanics theory. Finally, the finite-element simulation model of BGA packaged electronic chip was established and discussed. Failure characteristics of solder joints at different positions in electronic chips were compared and the failure mode of the solder joint was discussed using the simulation result and the observation result with scanning electron microscope (SEM). The results show that the life of each single solder joint in BGA packaged electronic chips follows a logarithmic normal distribution under the random vibration. Solder balls located at the four outermost corners of the chip are subjected to the greatest stress, which are the weakest parts in electronic chips. Cracks in solder joints are generated near the package side and emerged from the edge of the intermetallic compound (IMC) layer with the largest curvature.

Effect of thermal and vibrational combined ageing on QFN terminal pads solder reliability

Automotive environment generates vibration and temperature fluctuation, which reduces the life of electronic boards. The heavy trucks passing at relatively high speed on uneven road pavement is considered as the main reason of the traffic vibration. In fact, interaction between wheels and road surface causes a dynamic excitation which generates waves propagating in the soil affecting nearby structures. In addition, Thermal Cycling Test reveals the strict impact of environment conditions and slow cycles of temperature caused during operation. In this paper, vibration tests are performed continuously throughout thermal cycling to investigate the combined effect of temperature and vibration on the SAC305 solder of Quad Flat No-lead (QFN) terminals pads bonded on Printed Circuit Board (PCB). Power Spectral Density (PSD), which can be linked to the strain rate, is calculated from the acceleration, during combined ageing. Experimental results imply that the number of combined cycles affects the PCB responses: the value of the first natural frequencies and the corresponding PSDs. Fifty thermal cycles of combined thermal cycling and fatigue random vibration tests have been carried out on 100 QFN terminal pads solder. Statistical evaluation of the State of Health of the solder showed that cracking has started in 68% of them. An in-depth analysis was conducted to understand the reasons behind this degradation. On the other hand, an accurate numerical model for simultaneous combined thermal cycling and vibration simulation is developed and validated using experiments. These simulations make it possible to assess the displacement evolution due to combined loadings.

Continuous convolution and nonlinear transformation for multi-shaker non-Gaussian random vibration control

This study proposes a continuous convolution method combined with memoryless nonlinear transformation for multi-input multi-output stationary non-Gaussian random vibration tests. The challenge of the multi-shaker non-Gaussian random vibration test lies in the coupling problems that are manifested in the inherent physical system and in the existence of cross-spectral densities. In the presented method, the independent stationary Gaussian random signals pass through a designed finite impulse response filter with a convolution manipulation first, and then the resulting signals are transformed to the non-Gaussian random signals by the memoryless nonlinear transformation method. The desired drive signals are obtained by the input–output relationship in the frequency domain. The finite impulse response filter is constructed by the frequency sampling technique in which the amplitude characteristics of the filter are determined by the predefined reference power spectral densities. A new monotonic nonlinear transformation function with an approximate kurtosis solution is provided. It only contains one parameter for kurtosis control both in sub-Gaussian and super-Gaussian cases. The memoryless nonlinear transformation is used to maintain the cross-spectral densities, although some distortions are introduced to the power spectra during the transformation process. The inverse system method is used to overcome the coupling problem caused by the inherent physical system. A simulation example and a triaxial vibration test are carried out, and the results indicate the validity and feasibility of the proposed method.

High-damping PCB implemented by multi-layered viscoelastic acrylic tapes for use of wedge lock applications

Wedge locks have been widely used for effective spatial accommodation and easier integration of electronics. However, an increase in the dynamic displacement of the printed circuit board (PCB) with the increase in the board size is unavoidable because the wedge lock provides mechanical fixation only along the edge of the board. This is one of the technical issues in assuring the fatigue life of electronic packages under a severe vibration environment. However, application of a stiffener for the reduction of board displacement leads to an increase in the mass and volume of the electronics. In this study, for implementing lightweight and compact electronics, we proposed a high-damping PCB for effective vibration attenuation caused by high damping characteristics implemented by multi-layered viscoelastic acrylic tapes. The basic characteristics of the proposed PCB were obtained through free-vibration tests under various temperature conditions. Additionally, random vibration tests of PCB specimens with various layers of viscoelastic tapes were performed, and the fatigue life of electronic packages was compared to that of the specimen without tapes.

Study on the Random Vibration Test of 300MW Machine Unit in Thermal Power Plant

Study on the Random Vibration Test of 300MW Machine Unit in Thermal Power Plant

A simplified modelling and analysis of six degree of freedom random vibration test

This paper deals with the modelling and analysis of six degree of freedom random vibration test. It involves an advanced multi-input multi-output random vibration test system where three translational and three rotational motions can be controlled simultaneously. In this work, a mechanical model of the six degree of freedom vibration test system is established such that eight exciters are modelled as spring damper pairs and the shaker table is assumed to be rigid. The acceleration properties of the test article undergoing such six degree of freedom base vibrations are analyzed and the relationships among the absolute acceleration, relative acceleration and base acceleration are derived. In practical applications, typically there is no available angular acceleration sensor for high frequency measurements. Therefore, the three rotational accelerations are obtained from measured translational accelerations of three or more control sensors with a response coordinate transformation matrix. It is shown that the locations of the control points have a significant influence on the response spectral results, which is reflected in the condition number of the output coordinate transformation matrix. The general multi-input multi-output random vibration control method is applied to the 6-DOF random vibration test. A six degree of freedom random vibration test simulation is finally provided.

CubeSat’s Deployable Solar Panel with Viscoelastic Multilayered Stiffener for Launch Vibration Attenuation

Ensuring the structural safety of a deployable solar panel under a severe launch vibration environment is one of the important factors for a successful CubeSat mission. A CubeSat’s deployable solar panel proposed in this study is effective to guarantee the structural safety of solar cells by attenuating launch loads owing to the superior damping characteristic achieved by a multilayered stiffener with viscoelastic acrylic tapes. The demonstration model of 3 U CubeSat’s deployable solar panel was fabricated and tested to validate the effectiveness of the proposed design. The basic dynamic characteristics of the solar panel were measured through free-vibration tests according to the various layers of the stiffener. Moreover, the characteristics of the deployed solar panel were measured and investigated under various temperatures to predict its capability under in-orbit operation. The effectiveness of the proposed design for launch vibration attenuation was demonstrated through qualification level sine and random vibration tests.

Phase noise performance stabilization of PLL system under dynamic vibration condition for airborne applications

AbstractThe purpose of this paper is to disclose improved crystal based frequency source system covering design techniques and experimental methodologies for the stabilization of phase noise performance of X-band phase-locked loop (PLL) at 10.6 GHz. Phase noise performance of PLL-based unit under test (UUT) is prone to disturbance occurred in random vibration profile frequency spectrum. UUT self-resonance plays vital role in occurrence of disturbance in random vibration profile. The stabilization of phase noise performance during dynamic (random) vibration condition is achieved by following methodologies, i.e. vibration-isolator compensation techniques, purification tactic for reference crystal of PLL, and spatial location analysis for finding out mounting position of reference crystal. Spatial analysis helps to filter out UUT self-resonance frequency from random vibration spectrum which leads to reduction of frequency resonance pickups during random vibration testing.

Evaluation method and platform of vibrational disturbance test for ventricular assist devices.

For ventricular assist devices utilizing levitation bearing technology, collision and wear of the rotor would occur if the bearing cannot resist disturbances from patient activities and vibration/shock impacts. The reliability of ventricular assist devices can be seriously affected, potentially impairing blood compatibility (e.g. thrombus generation) and threatening patient safety. In this article, we proposed a vibrational disturbance test protocol for ventricular assist devices. Two kinds of vibrational disturbances-translational and rotational-were defined and the disturbance levels determined as 6G and 10 rad/s per possible patient activity impact. A test platform was built according to the disturbance level requirements. The test platform successfully generated the required disturbance. The vibration test evaluation criteria for ventricular assist device assistance (characterized by the pressure head, flow rate, and driving current waveform) were well verified. Compared with translational vibration, rotational vibration had a greater impact on the rotor. Accurate control of high-speed rotor is difficult because of the gyroscopic effect. As conventional random vibration tests cannot cover all risk situations, it is recommended that translational and rotational disturbance tests are carried out for levitation ventricular assist devices. We recommend that researchers and manufacturers pay attention to the vibrational impact of rotor-levitated ventricular assist devices.

Experimental Research on Combined Vibro-Acoustic Test of a Satellite

Random vibration tests and acoustic tests are typical environmental testing approaches for verifying the dynamic environmental adaptability of a satellite, which should be selectively carried out on the ground before launch. Existing test criteria suggest that large spacecraft should be excited in a reverberation chamber, whereas a shaker should be used for a small spacecraft. With the development of an experimental technique of environment simulation, the combined vibration and acoustic (vibro-acoustic) testing technique and the coupling effect are increasingly investigated for reproducing a more realistic environment and avoiding an overtest or an undertest. This paper describes a combined vibro-acoustic test of a full-scale prototype satellite in detail. The equivalence between random vibration and acoustics excitation for satellite ground testing is discussed. Then the vibro-acoustic coupling influence distribution on the satellite is experimentally investigated by using a defined reduction ratio factor. Finally the inhibition of high-frequency sound pressure caused by the cavity resonance is quantitatively measured to show the attenuation center frequency of sound pressure spectrum.

Determination of the topology of lithium-ion battery packs for space equipment and validation through experimental investigation

Abstract Lithium-ion batteries are extensively used, not only for their advantages of high specific energy and durability but also for their light weight and robust structures, in many applications of space equipment, where severe mechanical vibration and shock conditions are encountered, especially during the launch, climb and stationing on the determined orbit. To design a robust battery pack that can withstand such loading conditions, a comprehensive investigation into the effects of such circumstances must be carried out both experimentally and computationally. In this study, four different battery topologies complying with the electrical requirements were compared according to various performance indicators. Then, the best prototype of the alternatives was chosen. The selected lithium-ion battery pack was examined with the help of resonance, harmonic and random vibration tests that were implemented according to the ECSS (European Cooperation for Space Standardization) standards. Additionally, a finite element model of the pack was prepared, and vibration simulations were run and compared with the experimental results. In the experimental work, it was observed that the battery-pack retained its structural integrity without experiencing any kind of mechanical failures. It was also observed that the outcomes of the finite element simulations are reasonably consistent with the test results.

Damage monitoring of carbon fiber reinforced silicon carbide composites under random vibration environment by acoustic emission technology

Carbon fiber-reinforced silicon carbide (C/SiC) composites are widely used in high-temperature thermo-structural applications. They are subjected to extreme loading conditions, such as random vibrations, which are likely to damage the structure. Structural micro-damage identification during vibration is very difficult, owing to the randomness of the environmental vibration and the complicated response it causes in structures. This study aims to determine a method for monitoring the damage properties of a C/SiC structure under a random vibration environment using acoustic emission (AE) technology. First, a pencil break experiment is conducted to verify the feasibility of the AE technology. Then, an AE monitoring experiment of the structural damage in a vibration environment is systematically conducted. Two types of experiments are designed for simulating the damage formation process inside the structure. In addition, the parameter characteristics of typical AE signals in the random vibration test are analyzed, and the relationships between the AE signal parameters and vibration loading are obtained. Lastly, the different stages of material damage development and damage types in each stage are provided to reveal the damage evolution processes of C/SiC composites. The results indicate that AE technology can be effectively applied to investigate the damage behaviors of C/SiC composites in random vibration environments.

Analyses on the large size PBGA packaging reliability under random vibrations for space applications

Large size commercially available plastic ball grid array chip packaging was tested and analyzed under random vibration to access its application feasibility on satellite electronics. Two types of the PBGA of 16 mm × 16 mm and 10 mm × 10 mm were chosen, and the chips were surface mounted without underfill on a daisy chained polyimide printed circuit boards. Then the boards were installed to an aluminum frame, a common type used to fix the boards to satellite structure, and undergone the random vibration tests. Two extreme levels of the random vibrations, the power spectrum of which were 22.48 grms and 31.78 grms, were applied sequentially to investigate the sustainability. It was found that the test results did not show any solder failure under the test conditions, indicating the robust structural integrity and providing the evidences justifying the PBGA packaging feasibility to the aerospace applications. Numerical analyses were also performed to analyze the PCB vibration behaviors and stress development mechanisms. The analyses results showed that, unlike usual expectation, the first natural mode may not be the dominant contribution to the solder stress developments, and higher natural modes could induce the maximum stress depending on the chip size and its location.

High-frequency random vibrations of a stiffened plate with a cutout using energy finite element and experimental methods

In this paper, by employing the energy finite element analysis, the high-frequency vibrations of a stiffened plate having a cutout, subjected to random vibrations, have been analyzed, and the obtained results have been validated by use of experimental methods. By using equations for joining of structures, energy finite element analysis computer codes were developed for the coupling of beam-plate elements. Finally, a plate containing a cutout and three stiffeners was fabricated and subjected to high-frequency random vibration tests. The results of the prepared codes were compared with the results of experiments. These comparisons indicated that at high frequencies, the energy finite element analysis can be used as an effective tool in the analysis of high-frequency vibrations.

Remaining useful life (RUL) estimation of electronic solder joints in rugged environment under random vibration

The remaining useful life (RUL) of electronic modules under the influence of rugged random-vibration and operational conditions is investigated in this paper. The effects of storage conditions and soft failures, caused by the vibrations to solder joints of a printed circuit board (PCB) are analyzed. The RUL is estimated with the help of vibration testing and finite element analysis techniques. Keeping in view the standard and working environmental conditions, the PCB of a power distribution module is subjected to random and sine vibrations. Besides the significance of fatigue damage and RUL estimation of solder joints, caused by storage or operation for a period of five years has not been addressed in existing literature so far. The current study performs the modal analysis to find the natural frequencies, mode shapes, and participation factor ratios of a PCB and its components. These natural frequencies are subsequently verified via comparison with experimental sine sweep results. A random vibration test over the frequency range from 10 Hz to 2000 Hz is also applied for recording the time-to-failure ratio of the PCB. Moreover, the spectrum analysis is performed using the commercial ANSYS software, to assess the acceleration response and the stress power spectral density (PSD) of the critical solder joints. The stress PSD is then used to estimate the random vibration fatigue damage of the solder joint. The calculated fatigue life, based on the modified Miner's rule and the Basquin power-law conform to the actual random vibration testing results.

Fatigue failure and G rms –N curve of corrugated paperboard box

As a kind of transport packaging, the corrugated paperboard box is widely used in logistics. During transport, the stacked packaging units are subjected to random vibration induced by vehicles. Thus, the random dynamic force will be exerted to corrugated paperboard box continuously. As the shipping distance increases, there will be cumulative fatigue damage within the corrugated paperboard box, which will weaken the mechanical property (stiffness) and the protective value of the corrugated paperboard box. Therefore, the dynamic damage and fatigue failure of corrugated paperboard box are crucial for the design of corrugated paperboard box. This article aims to develop the acceleration root mean square-life curve of corrugated paperboard box. At first, the accelerated random vibration test method was developed by the theory analysis according to the damage equivalent principle of a specified point within the corrugated paperboard box. Then, the random vibration experiments were conducted on the loaded corrugated paperboard box by taking white noise as excitation power spectral density. In the experiments, the acceleration transmissibility curve was recorded periodically. Relative stiffness was taken as the indicator to detect the cumulative damage and assess the structural integrity of the corrugated paperboard box. The stiffness reduction 20%, 30%, and 40% were taken as fatigue failure criteria to develop the curves. Results show that both the Basquin type and exponential function type are in good fitting with the curve of the corrugated paperboard box. The index b of the Basquin type is between 8.16 and 11.01, and b′ of the exponential function type between 21.19 and 26.84. The study provides reference for the accelerated random vibration test of corrugated paperboard box.

A time-domain procedure for non-Gaussian stationary environmental testing using zero-memory nonlinear transformation

This article proposes a time-domain procedure for a non-Gaussian stationary random vibration test with prescribed power spectral densities. Previous procedures for generating non-Gaussianity suffered from certain defects. For example, zero-memory nonlinear transformation, an algorithm frequently applied to transform Gaussian signals into non-Gaussian signals, often produces changes in both auto-power spectral densities and cross-power spectral densities, which might result in control instability under certain circumstances. In this article, the authors propose a different approach for the zero-memory nonlinear function. First, a time-domain procedure for a non-Gaussian random test is introduced. Second, a rescaling method is applied to correct the magnitude amplification on the auto-power spectral density because of zero-memory nonlinear transformation. We offer experience formulas in this method to adjust the auto-power spectral density of both super-Gaussian and sub-Gaussian responses. Third, a control strategy using a finite impulse response filter is proposed to further improve the auto-power spectral density if the shape of the auto-power spectral density is distorted. The kurtosis loss induced by the filtering process is also analysed and a corresponding solution is put forward to ease the reduction. Numerical test and a biaxial shaker table test are conducted to validate the availability and superiority of the proposed procedure.

Experimental Analysis on Combined Vibration and Acoustics Test of a Satellite

Random vibration tests and acoustics tests are typical environmental testing approaches for verifying the dynamic environmental adaptability of a satellite, which should be selectively carried out on the ground before launch. Existing test criteria suggests that large spacecraft should be excited in a reverberation chamber, while a shaker should be used for a small spacecraft. With the development of experimental technique of environment simulation, the combined vibration and acoustics (vibro-acoustic) test are increasingly investigated for reproducing a more realistic environment and avoiding an over test or an under test. However, few studies have been published on coupling effect of combined vibration and acoustic test of a full scale prototype satellite. This paper discusses the equivalence between random vibration and acoustics excitation for satellite ground testing. The experiment results have shown advantages of the combined test in reproducing flight environment. And the coupling effect and distributions of high frequency response attenuation during the combined vertical vibro-acoustic test is observed and analyzed in detail.

On the Use of Kurtosis Control Methods in Shaker Testing for Fatigue Damage

Abstract Random vibration testing with increased kurtosis introduces high peaks into shaker drive signals to simulate land vehicle vibration more accurately and also to shorten the required test time. Two methods of controlling kurtosis by phase manipulation in the inverse fast Fourier transform were implemented, tested, and compared. The first method generates high-kurtosis excitations with a gradual, smooth pattern of peak heights from low to high, and the second method produces isolated high peaks with intervals of stable background vibration between them. When applying a kurtosis increase for accelerated fatigue damage testing, the kurtosis control method must be able to pass high-kurtosis values from the generated shaker table vibration into the stress response of the unit under test. However, this is not always the case, and only one of the considered methods was capable of doing so. In the article, the fatigue damage spectrum model was used for an evaluation of the time to failure. An experimental study was carried out using operational vibration measured in a car. Shaker testing of cantilever specimens was performed for Gaussian, non-Gaussian, and accelerated non-Gaussian excitations.

Dynamic response characteristics of an automotive lamp assembly

The objective of this paper is to model and analyse the dynamic response of an automotive lamp assembly. Modern automotive lamp assemblies have complex geometry and are composed of different parts made of polymer materials. As part of design verification, automotive lamp assemblies are subjected to accelerated random vibration tests to assess their integrity over a life-time exposure to mechanical vibration loading. Understanding the dynamic behaviour of the lamp is crucial in the numerical evaluation of the fatigue life. Dynamic analysis involves characterising the modal and harmonic behaviours. In this work, numerical modal properties and harmonic responses were validated using experimental testing. The numerical analysis was carried out using the ANSYS finite element analysis (FEA) software. Experimental modal properties including mode shapes and corresponding frequencies were determined using Polytec PSV-500 Xtra laser scanning head at a frequency range of 10 to 1000Hz. The experimental harmonic transmissibility responses of all the components of the lamp assembly were determined using a vibration shaker. The experimental and numerical mode shapes and responding frequencies obtained in the analyses compared well thus validating the numerical modal model. Furthermore, the mode shapes showed that the lamp assembly was mostly vibrating in bending, therefore subsequent analysis should take this into account. Harmonic response validation showed that the first few numerical resonant frequencies, that dominate the response, compared well with experimental results.