Core Mass-Production Issues and Comprehensive Mitigation Strategies for PiG (Phosphor in Glass) (Item 2)

Glass powder and phosphor powder absorb moisture; carbonates decompose to release CO₂, while nitrates produce NOₓ. Air gets trapped during powder blending and green body compaction. Gases fail to escape in the early sintering stage, resulting in large bubbles and continuous gray bubble clusters. This drastically reduces transmittance, causes local darkening and uneven light spots.

Unbalanced dosage of fining agents (CeO₂, Sb₂O₃) or excessively fast cooling leads to supersaturation of dissolved gas inside molten glass, precipitating tiny microbubbles. Closed pores inside green bodies fail to fuse during sintering and form micron-scale voids.

Uneven dry mixing, inadequate pressing pressure and short holding time leave massive inter-particle gaps. Interconnected internal pores remain after sintering, resulting in extremely low mechanical strength and edge chipping during cutting.

Vacuum-dry glass powder and phosphor powder at 120–180°C for 4–12 hours to completely eliminate adsorbed water. Adopt low-decomposition glass powder and reduce the proportion of carbonate raw materials.

Replace dry mixing with wet ball milling using anhydrous ethanol or isopropanol as the medium to achieve uniform powder dispersion and eliminate entrapped air. Conduct low-temperature vacuum drying after ball milling to avoid agglomeration with trapped bubbles. Control a narrow particle size distribution of phosphors to minimize inter-particle gaps.

• Adopt segmented uniaxial hydraulic pressing: slow pressure rise → hold pressure for 30–120 s → slow pressure relief to release internal air and prevent rebound voids.
• Apply Cold Isostatic Pressing (CIP) for high-end products to achieve uniform green body density and lower porosity below 1%.
• For thin-film PiGF, perform vacuum defoaming of slurry and static degassing before screen printing.