Research of LTCC/Cu, Ag multilayer substrate in microelectronic packaging

Low temperature cofired ceramics (LTCC) technology has been widely used for high frequency components. Thick film copper is one of critical technology in microelectronic packaging. This paper focuses on low temperature ceramic cofired with copper. The difficulty with LTCC/Cu is organic material removal and copper circuit protection. By the careful control of the oxygen partial pressure in different sintering procedure, a quality multiplayer/copper system can be achieved. Different shrinkage characteristics of copper thick film and LTCC sheet result in delamination, cracking, and camber in the final products. Sintering promoters play an important role in the electrical conductivity and adhesion strength of copper thick film. The final structure of the sintered thick film appeared as three dimensional network structure. Approximately 8 wt.% glass promoter can match the shrinkage rate of the substrate and silver paste. LTCC has a low thermal conductivity, which limits its application in some fields. Thermal vias buried in LTCC substrate can resolve this problem.