Structural, thermal and dielectric properties of low-alkali borosilicate glasses for electronic applications

Low-alkali borosilicate glasses are widely used in electronic packaging applications due to their low dielectric constant, low dielectric loss and excellent matching of thermal expansion coefficient to silicon. This paper presents information about structural, thermal and dielectric investigations of low-alkali borosilicate glass compositions for potential electronic packaging applications. Different bulk borosilicate glass samples were fabricated by conventional melting and quenching technique followed by powder processing. Total alkali oxide content in the composition was kept at 2-3 wt% to achieve high dielectric performance. The glass structure was investigated by Fourier transform infrared spectroscopy. X-ray diffraction analysis was employed to investigate crystallization behavior. Thermal properties were investigated by a heating microscope as well as a push-rod dilatometer. The dielectric properties were investigated by an impedance analyzer at room temperature. The results indicated that the glass structure connectivity has a significant effect on thermal and dielectric properties. Reduced glass structure connectivity due to the lower amount of tetrahedral BO4 units resulted in decreased bulk density, dielectric constant and characteristic temperatures as well as glass transition temperature (T-g). Sample D is a promising candidate for electronic packaging application due to its excellent matching of thermal expansion coefficient (3.3 ppm/degrees C) to Silicon, relatively low softening point (720 degrees C) and T-g (450 degrees C), low dielectric constant (4.07) and low dielectric loss (0.0029).