Received 20 December 2007 Defence Science Journal, Vol. 59, No. 1, January 2009, pp. 58-62 Ó 2009, DESIDOC 58 Estimation of Fatigue-life of Electronic Packages Subjected to Random Vibration Load M.I. Sakri, S. Saravanan, P.V. Mohanram, and S. Syath Abuthakeer PSG College of Technology, Coimbatore-641 004 ABSTRACT Random vibration is being specified for acceptance tests, screening tests, and qualification tests by manufacturers of electronic equipment meant for military applications, because it has been shown that random vibration more closely represents the true environment in which the electronic equipment must operate. In this paper, the methodology of testing an electronic package subjected to random vibration load is illustrated using Joint Electronic Device Engineering Council’s (JEDEC) JESD22-B103B standard. The electronic package mounted at the centre of the printed circuit board was subjected to vibration, variable frequency condition ‘D’ of JEDEC standard for 30 min. After 30 min of random vibration test, the component lead-wires, solder- joints, and PCB were thoroughly inspected for failure. From the observations, it was found that no failure occurred during the test period. The fatigue life of the component, estimated using analytical method, was found to be 96.48 hours. Keywords: Dual in-line package, DIP, random vibrations, JEDEC standard, electronic package reliability NOMENCLATURE C Constant for different types of electronic components h Height or thickness of PCB (inch) L Length of electronic component (inch) r Relative position factor for component on PCB P Input PSD level at resonant frequency (G 2 /Hz) B Length of PCB edge parallel to component (inch) Z rms Dynamic displacement of PCB, (inch) f d Desired natural frequency (Hz) f n Natural frequency of PCB assembly (Hz) L f Fatigue life of component (h) G rms RMS acceleration level 1. INTRODUCTION Electronic devices used in military equipment such as RADAR systems, communication systems, missile launch systems, and control devices in airplanes, helicopters, ships, and submarines operate in severe environmental conditions. It has been observed that most of the electronic failures are due to extreme temperature conditions (thermal cycling and thermal shocks), severe vibrations, humidity, and dust. According to US Air-Force statistics, of all the failures observed in electronic equipment used in defence applications, about 55 per cent are due to thermal problems, 20 per cent due to vibration problems, 19 per cent because of humidity and 6 per cent due to dust and other reasons 1 . (Fig. 1). High acceleration levels, displacements and stresses because of severe vibration loads (in particular random vibrations) will lead to failure of lead-wires; solder-joints, cracking of printed circuit board (PCB), and loosening of fastening screws. Table 1 shows the acceleration levels and the frequency range at which some of the military equipment operate. For reliable functioning of military equipment, the electronic- based control systems must be designed to withstand all sorts of severe vibration loads. The reliability of electronic devices used in military applications is very important while operating in worst terrains of battlefield. Malfunctioning of critical systems in military equipment will lead to heavy loss of human lives and property. Random vibration test has proved to be a very powerful tool for improving the manufacturing integrity of electronic equipment by screening out the defective components and defective assembly methods, which result in a sharp improvement in the overall reliability of the system. Steinberg 1 has described the failure of electronic equipment due to many different types of vibration during their service- TEMPERATURE 55% HUMIDITY 19% DUST 8% VIBRATION 20% Figure 1. Failures in electronic equipment.