A new approach to zero shrinkage LTCC

Several approaches have been introduced to produce zero x-y shrinkage of LTCC (Low Temperature Co-fired Ceramics) after co-firing in a conventional conveyor furnace. These techniques require additional experimental procedure to control shrinkage with better tolerance and/or to eliminate the so-called release tape through mechanical scrubbing. The release tape acts as a constraining layer during sintering by utilizing highly refractive materials such as alumina or zirconia as a main constituent of the tape. Recent reports revealed that un-sacrificial or internal constraining tape can be laminated with regular tape for subsequent zero x-y shrinkage. This work first demonstrates a new approach of producing zero x-y shrinkage without any additional sacrificial or un-sacrificial layer. This new approach is based on new LTCC composition consisting of novel glass and ceramic filler. Mechanism of the zero-shrinkage is associated with chemical reactions between tape constituents during firing. Carefully-designed LTCC materials integrated with Ag-based conductors have successfully demonstrated that the production of zero x-y shrinkage is reliable with competitive performance under common firing conditions such as 850-900°C and air-firing. Dielectric and physical properties changed depending on glass composition that determines the chemical reactivity and densification behavior. Dielectric constants of 4.0-9.0 and loss tangents of < 0.05 were typical values for the new zero shrinkage LTCC.