Influences of Al₂O₃ replacing Bi₂O₃ on structure and properties of phosphate glasses for electronic packaging

Currently, the development of new packaging substrate materials with low dielectric permittivity, low loss, excellent thermal stability, and chemical stability for meeting 6G massive high-speed wireless communication has always been significant pursuits of many researchers. In this work, the 10 CaO–(25-x)Bi₂O₃–xAl₂O₃–60P₂O₅–5Sb₂O₃(x = 0−15) glasses were fabricated using melting annealing process. The results indicate that with the increment of Al₂O₃ content, the numbers of [AlO₄] tetrahedron units and metaphosphate Q² units in the glass structure firstly increase and then decrease, implying an improvement to the glass network structure. Meanwhile, when the content of Al₂O₃ is 12.5 mol%, the molar volume (V_m) and oxygen molar volume (V_o) of the glass exhibit a minimum value, proving that the most compact glass structure is achieved. The 12.5 mol% Al₂O₃-added glass sample shows excellent chemical stability and possesses the low dielectric permittivity of 5.0 and the lowest loss of 2.5 × 10^–3 as well as the low thermal expansion coefficient of 8.21 × 10^–6/°C. These findings reveal that the prepared glass with 12.5 mol% Al₂O₃ is a potential candidate for electronic packaging field.