Contents lists available at ScienceDirect Microelectronics Reliability journal homepage: www.elsevier.com/locate/microrel Remaining useful life (RUL) estimation of electronic solder joints in rugged environment under random vibration Noor Muhammad a, ⁎ , Zhigeng Fang a , Muhammad Shoaib b a College of Economics and Management, Nanjing University of Aeronautics and Astronautics, 29 Jiangsu Avenue, Nanjing 211106, China b KTH Royal Institute of Technology, Stockholm, Sweden ARTICLEINFO Keywords: Random vibration Spectrum analysis Electronic solder joints Finite element analysis Fatigue life Remaining useful life (RUL) ABSTRACT 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 environ- mental 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 compo- nents. 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 vi- bration testing results. 1. Introduction Remaining useful life (RUL) for in-service electronic assemblies depends on the production process, the component type, quality of the soldering techniques, and the material besides the storage conditions. Electronic assemblies used in avionics and automotive applications experience significant vibrational stresses during operation or trans- portation compared with stationary equipment. The solder joints in printed circuit boards (PCBs) are affected by operational and storage conditions, which may lead to the earlier failure of the entire electronic assembly [1]. During storage, the failure in most of the electronic as- semblies is triggered by thermal stresses, temperature, and humidity, whereas the vibration is a major factor of failures during transportation. Field failure data [2,3] further verifies that about 95% of the electronic assemblies fail due to environmental stresses, about 55% of the pro- ducts fail due to thermal stresses (like high temperature and thermal cycling), 20% of the failures are due to humidity, and 20% are due to shock and vibration. Furthermore, the field failure data also indicates that the electromechanical assemblies and the solder joints are more vulnerable to the vibrational stresses. These vibrational stresses expose whiskers and cracks in the solder joints that may lead to the soft-failure under vibrational environment. This soft-failure is difficult to be iden- tified in the storage environment, as it is only triggered once the PCB module is in a vibrational environment. Therefore, the vibrational analysis plays a critical role in identifying the soft-failure vulnerability of solder joints in PCB modules, leading to an accurate assessment of storage stresses for the estimation of RUL. The existing studies have been conducted for the estimation of RUL in the context of environmental effects on PCB modules. According to Pippola et al. [4] and Smith [5], the life-consumption-monitoring (LCM) methodology is helpful to have an idea of consumed as well as RUL of the PCB module. In LCM, the physics-of-failure helps in iden- tifying the effect of stresses on the life of components, interconnects, assemblies, fixtures, and body of the module. The PCB module under investigation experiences random vibrations during operation; whereas, the sinusoidal vibration testing helps in estimating harmonics due to natural frequencies [7]. Kim and Hwang [8] have studied the reliability of plastic ball grid arrays (PBGAs) packaging under harsh random https://doi.org/10.1016/j.microrel.2020.113614 Received 30 September 2019; Received in revised form 10 February 2020; Accepted 18 February 2020 ⁎ Corresponding author. E-mail address: noor@nuaa.edu.cn (N. Muhammad). Microelectronics Reliability 107 (2020) 113614 0026-2714/ © 2020 Elsevier Ltd. All rights reserved. T