Investigation of the mechanical properties of printed circuit boards for nanosatellite

Abstract

Printed circuit boards (PCBs) are the backbones of electronic devices, used in nanosatellite to mechanically support, electrically connect, and protect electronic components of different subsystems. Their use in the space industry requires better knowledge of how they will react to the application of mechanical stress, because once in space there is no way of addressing any failure caused by structural deficiency. Therefore, the present work aimed at investigating the reaction of four-layer printed circuit boards to the application of static mechanical load. To achieve its aim, three objectives have been assigned to this dissertation: to characterize the reaction of the board to tensile stress and flexure stress, and to determine the allowable stress the board can withstand without compromising its structural performance. Hounsfield and Zwick Roell Universal Testing Machine (UTM) were used, respectively, to assess the board to tensile stress and to flexure stress using a three-point bend test; fractography analysis was undertaken with a Nikon SMZ25 microscope to validate the results. The FR-4 and Mercurywave samples were found, respectively, to have an ultimate tensile strength of 200.9084 MPa and 151.3143 MPa; a flexure strength of 602.7 MPa and 333.6 MPa; an ultimate tensile strain of 9.8% and 7.1%; a Young’s modulus of elasticity of 6.8 GPa and 5.9 GPa; a flexure modulus of elasticity of 42.0 GPa and 23.7 GPa; a Poisson’s ratio of 0.8% and 0.9%; a bending stiffness of 32.3 N/mm and 28.1 N/mm; a percentage elongation of 9.8% and 7.1%; and a deflection angle at fracture of 52.3% and 46.2%. The discussion has shown that the FR-4 sample will react significantly better to the application of tensile and flexure stress, and fractography analysis has validated the findings of the result analysis by showing trans-laminar and intra-laminar fracture morphology on the surface of the samples tested to tensile test and trans-laminar, intra-laminar and interlaminar fracture morphology on the surface of the samples tested to flexure test.