Author : M.I. Sakri, P.V.Mohanram

The lead wires and solder joints of surface mounted sensitive electronic components are more prone to failures due to vibration environments and leads to malfunctioning of electronic system. In this work a Plastic Small Outline Package (PSOP) and Printed Circuit Board (PCB) assembly is used as a test vehicle and subjected to sinusoidal vibrations by mounting the PCB assembly on conventional Nylon spacers. Then, the assembly is subjected to a constant input acceleration of 0.5G. Small input acceleration levels are amplified at resonant frequencies due to which high stresses are induced in lead wires and solder joints. Efforts are made to reduce the stress levels in critical elements of electronic packages, transmissibility ratio, PCB displacement and output acceleration levels by introducing damping using the resilient Neoprene rubber as a spacer material. By mounting the PCB assembly on Neoprene rubber spacers the displacement and output acceleration levels are minimized. The experimental results reveal that, the PCB mounted on Nylon spacers experienced a deflection of 0.1 mm (at PCB centre), output acceleration of 55G and a transmissibility ratio of 110 (at first resonant frequency and 0.5G input). When the PCB assembly was mounted on Neoprene rubber spacers and subjected to same input acceleration of 0.5G, the deflection and peak acceleration levels were reduced by 40% and 46% respectively. Also, the transmissibility ratio was reduced by 46%. Numerical simulation is also done to validate the experimental results. The experimental and numerical simulation results are in close agreement with each other. The methodology of the research work is explained in the following sections.

Keywords: Printed Circuit Board, Lead wires, Solder joints, Rubber spacers, Vibration control, Fatigue life.

Article published in International Conference on Advances in Mechanical Sciences 2014, Special Issue-2 (Feb 2014)