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We have improved charge character on the surface of phosphor particles by dispersed sub micro miter size sulfonate polystryrene beads and polyelectrolyte dispersant. The surface of TAG (Terbium Aluminum Garnet) phosphor was analyzed with TOF-SIMS (Time Of Flight-Secondary Ion Mass Spectrometer). Many hydrocarbon molecules were existed on the TAG phosphor. We could exchange the hydrocarbon into polyelectrolyte and sulfonated polystyrene beads. Characterization of the chemical bonging of polystyrene beads adhered on the surface of the TAG phosphor was archieved with x-ray photoemission spectroscopy (XPS) and FT-Raman. We could measure light efficiency of the white LED with integrating sphere spectrophotometer. Adhering sub micro miter size sulfonated polystyrene beads on the surface of TAG phosphor has enhanced extraction efficiency of light from phosphor. The sulfonated ligand and reduced difference of refractive index between phosphor and encapsulant material are responsible for the enhancement of extraction efficiency light from phosphor. Additional increase of light extraction has been observed when the phosphor particles were coated only on and near the LED chip. Surface modified phosphor particle and phosphor layer have improved LED light efficiency about ten percents.

A new LTCC (low-temperature cofired ceramic) system containing Al 2 O 3 platelets instead of conventional Al 2 O 3 particles as a filler material was investigated. As the Al 2 O 3 platelets were arranged parallel to the casting direction during tape casting and had preferred orientation in the green tape, the linear shrinkage of the green body took place mainly in the direction perpendicular to the platelet planes with just a little shrinkage in the horizontal without any external force during sintering. The intended anisotropic shrinkage of the new LTCC system made the constrained sintering of 10-mm-thick ceramic body possible, which decreased the sintering shrinkage tolerance in the x-y directions of the 10-mm-thick ceramic body from 0.5% to 0.05%. The new LTCC system showed equivalent electrical properties and remarkable physical properties in comparison with a conventional LTCC system.

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