Mohammad A. Gharaibeh

Accelerated vibration reliability testing of electronic assemblies using sine dwell with resonance tracking

In this work a sinusoidal vibration test method with resonance tracking is employed for reliability testing of circuit assemblies. The system continuously monitors for changes in the resonant frequency of the circuit board and adjusts the excitation frequency to match the resonant frequency. The test setup includes an electrodynamic shaker with a real-time vibration control, resistance monitoring for identifying electrical failures of interconnects, and vibration logging for monitoring changes in the dynamic response of the assembly over time. Reliability tests were performed using both the resonance tracking sinusoidal test method and the traditional fixed-frequency method for assemblies, each consisting of a centrally mounted BGA device assembled with SAC305 solder. These tests show that the resonance tracking method gives more consistent failure times than the fixed frequency method. Failure analysis for the tested devices shows the primary failure mode is trace failure with evidence of solder fatigue. A finite element model, correlated with experimental modal analysis, is shown to accurately estimate the circuit board deflection estimated from the harmonic vibration data. This provides a means of estimating the stresses in the electronic interconnections while for accounting for the variability between test parts. These fine-tuned vibration measurement techniques and related finite element models provide the building blocks for high cycle solder fatigue plots (i.e., S-N curves).

Analytical Solution for Electronic Assemblies Under Vibration

An analytical solution using Ritz method for the electronic assembly vibration problem has been presented in detail. In this solution, a special treatment for plate-mounted-on-standoffs boundary conditions scheme was required, and hence described. Also, a simple equation for estimating ball grid array (BGA) solder joint axial stiffness was developed. The results of the analytical solution were validated with modal analysis measurements and finite element (FE) models data in terms of natural frequencies and mode shapes. Then, the analytical solution was used to estimate the most critical solder joint deformations and stresses. Finally, the so developed solution provided an effective tool to examine the effect of several geometric and material configurations of electronic package structure on the fatigue performance of electronic products under mechanical vibration loadings.

A Pair of Partially Coupled Beams Subjected to Concentrated Force

This paper presents a solution for a symmetrical coupled beam structure loaded by a concentrated force. In this structure, a simply supported beam is coupled to another beam by a thin elastic layer, and the elastic layer can connect either the whole beams or only part of the beams. This solution generalized the previously published solution on a uniform coupling to the case of partial coupling. The solution strategy with governing equations and boundary conditions is discussed, and the solution for a most practical case is given explicitly. The analytical solution is in excellent agreement with the finite element analysis result. Finally, the effect of the key parameters is discussed in detail, with emphasis on its application in structural analysis of printed circuit board assembly in electronic packaging.

Reliability assessment of electronic assemblies under vibration by statistical factorial analysis approach

Purpose n n n n nThis paper aims to present a reliability performance assessment of electronic packages subjected to harmonic vibration loadings by using a statistical factorial analysis technique. The effects of various geometric parameters, the size and thickness of the printed circuit board and component and solder interconnect dimensions on the fundamental resonant frequency of the assembly and the axial strain of the most critical solder joint were thoroughly investigated. n n n n nDesign/methodology/approach n n n n nA previously published analytical solution for the problem of electronic assembly vibration was adopted. This solution was modified and used to generate the natural frequency and solder axial strains data for various package geometries. Statistical factorial analysis was used to analyze these data. n n n n nFindings n n n n nThe results of the present study showed that the reliability of electronic packages under vibration could be significantly enhanced by selecting larger and thicker printed circuit boards and thinner and smaller electrical components. Additionally, taller and thinner solders might also produce better reliability behavior. n n n n nOriginality/value n n n n nThe results of this investigation can be very useful in the design process of electronic products in mechanical vibration environments.

Vibrations Analysis of Rectangular Plates with Clamped Corners

Abstract This paper discusses the fundamental natural frequency of a thin elastic rectangular, isotropic and orthotropic, plates with clamped corners. Rayleigh’s method was used to analytically calculate the plate lowest natural frequency. In this solution, the vibration mode shape was assumed in a form that certifies the displacement as well as the rotational boundary conditions of the current problem. Finally, this paper provides useful information for evaluating the natural frequency of a plate with fixed corners with different mass attachments configurations.

Reliability analysis of vibrating electronic assemblies using analytical solutions and response surface methodology

Abstract This paper introduces a reliability performance study of electronic assemblies subjected to harmonic vibration loading using analytical solutions and response surface methodology (RSM). The work involved a modification of a previously published analytical solution for the vibrating assembly problem. This solution is employed to calculate the fundamental resonant frequency of the system and the ball grid array (BGA) solder interconnect axial deflections. Using RSM, the geometric parameters of an electronic package, the size and thickness of the printed circuit board (PCB) and the component as well as the solder height and radius, effects on the assembly first natural frequency and the most-critical solder joint axial deflection is investigated and hence presented. The results showed that the natural frequency of the system as well as the critical solder deformations and thus reliability can be effectively affected by such geometric variables. The results of this study can be very useful for the design of electronic products in vibration loading environments.

Finite element model updating of board-level electronic packages by factorial analysis and modal measurements

Purpose n n n n nOne difficultly in building an effective finite element (FE) model of a board-level package is because of complex structure of the printed circuit board (PCB), as it contains copper layers, woven fabrics, plated-through holes and so forth. Therefore, it is often acceptable to obtain equivalent orthotropic material properties and use them in the simulation. This paper aims to provide a research methodology to produce equivalent FE models for board-level electronic packages. n n n n nDesign/methodology/approach n n n n nIn this methodology, the FE models’ data were correlated with experimental modal analysis results in terms of natural frequencies and mode shapes. Statistical factorial analysis was used to examine the electronic assembly material properties effect on the structure’s resonant frequencies. The equivalent material properties of the PCB were adjusted using the optimization tool available in ANSYS software for free boundary conditions. The equivalent FE model was then validated for the fixed boundary conditions. n n n n nFindings n n n n nThe resultant FE models were in great match with the measured data in terms of resonant frequencies and mode shapes. The so-developed models can be further used in the analysis of the dynamic response of the electronic packages and solder interconnects. n n n n nOriginality/value n n n n nThe current approach provides a sophisticated research methodology to provide high-accuracy FE models of electronic assemblies subjected to vibration. The main value of this approach is to first test the effect of each material property on the package dynamic characteristics before starting the correlation process, then to automate the correlation algorithm using the built-in FE model updating feature available in ANSYS software.