Influence of particle diameter of alumina and specific surface area of glass flux on the packing density of green sheets

When the alumina particle diameter was in the range 0.8 to 3.6 μm and the flux specific surface area was 1 to 20 m2/g, the packing density was 61 vol%, nearly the same as the theoretical packing density (60.45 vol%) of monosized powder. However, the packing density decreased to 60 vol% when the particle diameter was 0.5 μm. It also decreased to 55 vol% or to 38% when the flux specific surface area was 100 m2/g, or 380 m2$//g. For the alumina/flux powder mixture, the larger alumina particle diameter, the smaller the flux specific surface area and the higher the packing density. The packing density remained unchanged (61 vol%) even when the amount of binder varied within the range 3 to 18 weight%. When the amount of binder was more than 18 weight%, the packing density decreased linearly as the amount of binder increased, regardless of whether the binder was polyvinyl butyral or polymethylmethacrylate.