Preparation And Constrained Sintering Behavior Of Low-temperature Co-fired Ceramic Tapes

In recent years, low temperature co-fired ceramic (LTCC) has become a hot issue due to the wide application in the hybrid integration technology. LTCC thick films have been used as the basic component in various multifunctional devices. The study of the constrained sintering behavior and relevant mechanisms of LTCC films was an essential task for the optimization and precise control of the processing. In this paper, the tape casting processing of Yinfeng8.5thick films was investigated in addition to the vertical sintering behavior of DuPont951TM (DU), Ferro A6MTM (FE) and Yinfeng8.5TM (YF) tapes, and the influence of rigid substrate on the densification behavior of YF films with different thickness.Firstly, based on a series of experiments, optimal tape-casting parameters were obtained for the investigated systems. The solvent was composed of alcohol and methylbenzene with a weight ratio of3:2, and used according to200wt%-220wt%of the powder weight. Different additive agents were added in the solution, including triethyl phosphate as the surfactant with an optimal content of1%, polyethylene glycol (PEG) and dibutyl phthalate (DOP) as the plasticizer and polyvinyl butyral (PVB) as the binder. The obtained viscosity of the slurry decreased with the increase of the DOP content. The best additive amounts for the PVB were10wt%and8wt%for the casting process on glass and alumina substrate, respectively. Besides that, parameters were also determined for the slurry treatment process. The milling time was24h for the first and second ball-milling process and the vacuum degassing time was20min.Secondly, the uniaxial viscosities for the three LTCC films were determined through the measurement of the strain obtained through a non-contact optical dilatometer. The dilatometer was designed to facilitate the observation of sintered films. A platform was fabricated to make full use of the novel vertical sintering method. The dependence of viscosity on the density was determined for the three investigated systems, which exhibited a non-linear relationship. The viscosity was low in a relatively low density region, but increased dramatically in the high density region. The experimentally measured viscosities of DU, FE and YF films were consistent with those predicted by the Raj’s model. The activation energy for the uniaxial viscosity of DU films was obtained based on the Arrenhnuis function and the value was determined to be290±47kJ/mol. Lastly, the sintering behavior of YF films constrained by the alumina substrate was also studied in this paper. A quartz rocking arm was designed for the measurement of the film thickness during densification. Through the magnification effect of the quartz arm, the thickness change of the constrained film could be precisely determined. The sintering behavior of three constrained film with different thickness was experimently determined, through which the relationship between densities, densification rate and film thickness could be obtained.