Tuning high and low thermal expansion coefficients of Li2O–BaO–Al2O3–B2O3–SiO2/quartz LTCC composites by replacing quartz partly with α-Al2O3 or ZrO2

Abstract

Low-temperature co-fired ceramics (LTCC) with adjustable coefficients of thermal expansion (CTE) based on Li 2 O–BaO–Al 2 O 3 –B 2 O 3 –SiO 2 /quartz LTCC composites (glass/ceramics) have been employed in electronic packaging to address the interface thermal mismatch problem caused by different thermal expansion coefficients. In the present study, sintering behavior, phase structure, and CTE of LTCC composites is controlled by replacing quartz partly with α-Al 2 O 3 or ZrO 2 . Accordingly, LTCC composites with the highest and lowest CTE values are achieved. The results show that the major phases of α-Al 2 O 3 substituted LTCC composites are hexacelsian, β-spodumene, and virgilite. Correspondingly, CTE values are in the range of 5.67–8.62 × 10 −6 /°C. Whereas, ZrO 2 substituted LTCC composites have exhibited increased CTE values to 12.27 to 13.2 × 10 −6 /°C with major phases of cristobalite, hexacelsian, and bazirite. Moreover, the negative effects of phase transformation of hexacelsian can be inhibited to a certain extent upon substitution of α-Al 2 O 3 up to 15 wt%. This work provides suitable methods for preparing LTCC composites with gradient CTE and resolving the thermal mismatch effects at different interfaces (e.g., chip/LTCC, metal electrode/LTCC) in electronic packaging structures.