Core mass-production issues for PiG (Phosphor in Glass) and comprehensive mitigation strategies (Item 5)

If the glass softening point is too low or the high-temperature holding time is excessive, unsupported green bodies will collapse during sintering. Thin PiGF films suffer edge curling and dimensional distortion, making them incompatible with LED chips or automotive lighting substrates.

Rapid heating or cooling rates, together with mismatched thermal expansion coefficients between glass and phosphor powders, generate internal thermal stress that triggers microcracks and edge chipping. Uneven compaction pressure creates an internal density gradient inside green bodies, leading to delamination due to inconsistent sintering shrinkage.

Batch variations in powder mixing ratios and green body compacted density cause irregular shrinkage in length, width and thickness of finished products, resulting in out-of-spec dimensions.

Place green bodies on high-purity alumina flat plates and use limiting molds during sintering. Ultra-thin PiGF films shall be carried by sapphire substrates to restrain high-temperature flow. Adopt glass systems with higher softening temperature to improve high-temperature structural rigidity.

Apply slow low-temperature heating at 1~3°C/min to fully remove moisture and organic binders. Implement multi-stage slow cooling after sintering with a cooling rate ≤5°C/min. Match the thermal expansion coefficients of glass matrix and phosphor powders to minimize interfacial thermal stress.

Unify powder filling weight, pressure ramping profile and pressure holding duration; calibrate hydraulic press pressure regularly. Use granulated powder to improve density uniformity of green bodies and control shrinkage fluctuation within less than 1%.