Research Projects

Composite Material Integration for High-density Embedded Passives

This is a feasibility study to determine novel processing capability of capacitor formation using high permittivity tape in composite structure of low permittivity LTCC tapes.

Contact PersonVasudivan Sunappan()
SolutionProcessing of LTCC composite materials with mixed dielectric properties required modified fabrication processes. A combination of the controlled printing process and the split-step lamination produced excellent planarity which rendered the substrate suitable for post firing processes such as flip chip or other components assembly. The substrate warpage is minimised when the high permittivity layer is sandwiched between an equal number of low permittivity LTCC tape layers and further reduced when more mass, either in terms of layers or in terms of surface area, is added.
Applications

Low temperature co-fired ceramic (LTCC) substrate technology offers an excellent platform for multi-functional integration. The co-sintering processes developed to achieve heterogeneous integration of low permittivity dielectric materials and high permittivity dielectric materials will provide the key platform technology to realise multi-functional integration and mixed-signal functions in Radio Frequency (RF) applications.

Problems Addressed

Manufacturing challenges in co-sintering of composite dielectric materials in multi-layer configuration are studied and analysed. Conventional LTCC tapes and inks shrink by about 15% and 25% after firing in x-y plane and z-axis respectively. The composite structure of high permittivity tapes in low permittivity LTCC tapes constrain the fired shrinkage to about 3% in x-y plane and 48% in z-axis. The composite structure results in significant via protrusion of the vertical interconnects due to non-uniform shrinkage of via-fill inks and dielectric tapes. The Coefficient of Thermal Expansion (CTE) mismatch of low and high permittivity tapes results in substrate warpage.