Correlation of Printed Circuit Board Properties to Pad-Crater Defects Under Monotonic Spherical Bend

Abstract

The restriction of lead in solder has caused a change in base materials used to make electronics—the result of which has been a new failure mode known as pad-crater. The susceptibility of six commercially available printed circuit board (PCB) laminates to pad-crater by spherical bend test was determined. The correlation of PCB laminate tensile properties, Vicker’s hardness (VH) of the resin, and weave dimensions showed an inverse relation between susceptibility to pad-crater and VH. Spherical bend testing of pure G10 laminate showed the orthotropic nature of laminates must be accounted for when modeling spherical bend. Comparison of bare PCB spherical bend test results showed the warp and weft direction have different strain responses for some materials. Comparison of strain energy of printed circuit board assemblies and bare PCB subjected to spherical bend showed the additional stiffness added by the ball grid array is almost identical for PCB laminates with different tensile properties.