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In the em simulation of MMICs and packages it is often advantageous to use vias with rectangular cross-section instead of cicular ones, because this allows for more efficient meshing thus reducing numerical expense. This paper provides detailed results on how the dimensions should be chosen to achieve equivalent electrical behavior. The investigations show that, if the rectangular via is chosen properly, the deviations in electrical behavior compared to the cylindrical version remain very low over a broad bandwidth of frequencies.

The addition of a standard fiberglass surfactant, 3‐aminopropyltriethoxysilane (APS), improves whisker and powder dispersion of silicon nitride aqueous suspensions. Aqueous suspensions of APS‐coated silicon nitride have lower viscosities, increased consolidation, and higher dried green‐body densities compared to uncoated silicon nitride in suspensions with pH values ≤8. The APS coating shifts the isoelectric point (IEP) of silicon nitride to a more basic value, dependent on the concentration of APS coating. Suspension pH measurements indicate that APS extracts one hydrogen ion for each APS molecule either chemisorbed on the particle surface or dissolved in the solution. Optical microscopy reveals that dilute suspensions coated with APS at pH 10 are qualitatively more dispersed than uncoated silicon nitride at pH 7. Our results show increased dispersion of APS‐coated silicon nitride in acidic environments, with a 12% increase in green density under identical wetpressing conditions.

No abstract

To improve the processing of silicon nitride, boehmite and yttrium oxide were coated on silicon nitride particles by an aqueous sol-gel method. It is shown that boehmite and Y2O3 can be coated on Si3N4 particles from aqueous solutions. However, the Y2O3 coating is not as complete as boehmite coating. The coating of a yttria coating followed by a boehmite coating was attempted and the TEM showed a coating twice as thick as the Y2O3 or AlOOH coating. Hydrothermal treatment of yttrium nitrate hydrous hydroxide results in the formation and growth of Y(OH)3 fibers which can be calcined and transformed into Y2O3 fibers at 500°C.