Effect of different Ba/Sr ratios on the properties of borosilicate glasses for application in 3D packaging

Abstract

Borosilicate glass is a promising material for 3D system integration technology due to its high integration and adjustable CTE (coefficient of thermal expansion). However, the structure and composition of borosilicate glasses result in a relatively high melting point and dielectric loss, which hinders the wide application of such glasses. In this study, we analyze the relationship between different Ba/Sr ratios and the structure and properties of the glass. We determine and further analyze the effect of mixed alkaline earth effect on the proportion of the Qn unit, [BO3], and [SiO4] in the glass structure, and consequently, its influence on the dielectric properties. Alkaline earth metals act as network-modifying ions to reconnect the interrupted network of the glass, stabilizing the glass structure and reducing the polarization loss of the glass. Raman analysis showed that the Raman spectrum shifted towards higher frequencies as the ratio of Al2O3/RO increased, with the Raman bands at 1300 cm−1-1500 cm−1 almost disappearing, while the Raman area at 730 cm−1-830 cm−1 increased. This indicated that the [BO3] units formed a ring structure in the glass, thereby enhancing the compactness of the glass network. The thermal expansion coefficient was 4.09 ppm K−1 when the Ba/Sr ratio was 1:1, and the dielectric constant and dielectric loss were 4.3 and 1.24 × 10−3, respectively. Overall, the dielectric properties and thermal expansion coefficients of the glass can be effectively reduced by doping with alkaline-earth metals, making the borosilicate glass more suitable for three-dimensional integrated system packaging.