Fabricating Al2O3/Pyrex glass–ceramic composites with gradient CTE to solve IC packaging’s thermal mismatch

A series of novel low-temperature co-fired ceramic (LTCC) materials with gradient coefficients of thermal expansion (CTE) was successfully developed through the controlled incorporation of BaO and K₂O into alumina/Pyrex glass composites. The LTCC materials exhibit a gradient CTE ranging from 2.61 to over 10 ppm/℃. Additionally, these gradients are finely optimized through adjustments to the crystal phase composition and glass phase network. Benefiting from the mixed-alkali effect, the dielectric loss of these materials is optimized from the order of 10^–2 to below 10^–3 while achieving a dielectric constant of approximately 4. The fabrication of laminated structures with precisely designed CTE gradients was successfully implemented, and their structural integrity was rigorously evaluated through thermal shock testing. The LTCC material series exhibited good thermal conductivity and reached a maximum flexural strength of 113 MPa. The construction of the gradient CTE system and laminated structure design offers valuable insights into addressing CTE mismatch challenges between chips, substrates, and printed circuit boards (PCBs) in integrated circuit (IC) packaging. Moreover, the performance-optimized LTCC materials demonstrate great potential and significant advantages for IC packaging applications.