What is PiG?

White LEDs (WLEDs) have become a conventional light source these days due to its high luminous efficacy and long lifespan compared to traditional fluorescent lamps. A white LED normally consists of a blue or violet chip and phosphor that converts the narrow band emission of the chip to a broader spectrum. Conventionally, the phosphor is mixed with organic or silicone resin so that it could be mounted on top of the LED chip, however, the defects of thermal and chemical stability of the binders cannot satisfy the recent development of high power WLEDs.

To overcome the inherent defects of the resin substrates, there are many inorganic alternatives to the resin-based phosphor, such as phosphor ceramics, bulk glass phosphor, single-crystal phosphor. Among them, Phosphor in Glass (PiG) is the most practical and promising solution due to its relatively simple manufacturing process and advanced photonic characteristics like color conversion efficiency compared to other ceramic or glass phosphor. PiG is manufactured by sintering the mixture of phosphor and glass powder to glass plates at atmospheric pressure with a temperature of less than 800°C. By replacing resin with glass, PiG improves the performance of thermal and chemical stability, which gives it the potential for high power WLED applications. In addition, PiG provides homogeneous distribution of phosphor particles in the substrate where the nonuniformity is caused by the viscosity of resin. Thus, PiG has a huge potential in various applications in the near future.

Why Changing from Resin to Glass?

Visualization of illumination process of traditional resin phosphor

Normal white LEDs use red and green phosphor mixing with silicone, epoxy or other resins. The mixture is cast onto the chip to convert the blue light emitted from the chip into red and green light. Although this approach is simple to prepare, it has some defects like, resin is susceptible to heat and water and the nonuniformity distribution of phosphor particles affects the chromaticity of output light.

Visualization of illumination process of PiG

PiG on the other hand, is a solid plate, which can be cut to fit the shape of LED chip perfectly. In addition, the phosphor particles are dispersed more homogenously in the glass than resin and thus the chromaticity and spatial distribution of the converted light are near to perfect. The glass is also more stable than resin to protect phosphor from the damage of heat and water vapor.

Features

High Luminance density
Thermal conductivity of PiG is normally 1 – 20 W/(K·m) compared to that of resin is generally < 0.2 W/(K·m). Larger Thermal conductivity and better thermal stability contribute to the endurance of high luminance density of PiG as a result of the ability to conduct heat away and reduce the temperature. The luminance density of PiG could reach 1000 lm/mm^2 and above, in contrast of that resin can bear less than 200 lm/mm^2.
Homogenous Illumination
The area of traditional silicone phosphor is larger than the surface of the chip (or diode). This mismatch causes yellow spot at the around. However, PiG can be cut to any shape and thus can fit the chip perfectly, which solves the problem.
Consistent Chromaticity
The homogenous distribution of the phosphor particles in PiG results in the more concentrated chromaticity coordinates and thus the color of the emission light is more accurate. The color deviation is small enough for omitting the binning process.
Long Lifespan
PiG is stable under high temperature and high humidity. So it is more reliable either at working or storage condition and has a long life time. Our test shows that PiG has a much slower attenuation (< 4%) than silicon phosphor (~18%) after 1500h at an operation current of 1A.

Yuji PiG

Yuji brings its mature phosphor technology to the remote phosphor field.

Showcase

A bulk of uncut PiG is a glass plate with color of the phosphor it contains. The images show Yuji PiG plates with two different CCTs and third one reveals a square piece of PiG illuminated by a blue LED chip.

Specifications

Yuji PiG shows high performance and versatile in every aspect.

Material properties
Uniformity< 500K
Glass transition Temperature (Tg )650~850K
Thermal Expansion Coefficient8~17 ppm/K
Thermal Conductivity1.01~3.44 W/m*K
Surface finish (Ra)6~12
Shape and Size
Rectangle (1mm * 1mm and above)Round (Ф1.5mm and above)Exotic
Yuji PiG is flexible in shape and size. The PiG plate can be cut to rectangle, round and even anomalous shape. The minimum is 1mm for rectangle side length or 1.5mm for round diameter.
Thickness
The thickness of Yuji PiG could also be variable between 150 um ~ 300 um or as clients request.
CCT
Yuji PiG is available for a large range of CCT between 2700K and 6500K including cold, neutral and warm white. The white light emitted focuses closely on the black-body curve and has a very tight tolerance.
General color rendering index (Ra)
High CRI is always the pursuit of Yuji’s products. Benefits from the advanced phosphor technology, The Ra of Yuji PiG rarely falls below 90 and breaks the stereotype that LEDs are impossible to have high luminous and high CRI at the same time.
Optical parameters
CCTIF
(mA)
VF
(V)
Φ
(lm)
Efficiency
(lm/W)
xyRa
ANSI_2700K1203.129.279.50.4530.41892.5
ANSI_3000K1203.131.686.20.4360.40691.3
ANSI_5700K1203.134.092.60.3240.34991.4
ANSI_6500K1203.133.891.90.3130.33390.6
Typical Spectrum
Yuji PiG mimics the spectrum of black-body radiation. The spectrum follows the spectral of incandescent lamps at 3000K and that of daylight at 5000K, with a broad range covering all the visible section of wavelengths.

Applications

Due to the long-term stability of PiG under high operating temperature, it is suitable for applications required high power LEDs.

Besides high power applications, PiG can also be applied to artificial lighting source for plant growing, or the substrate for OLED.

Finally, as a result of the high reliability and long lifespan, PiG can reduce the maintenance cost of its application field.

Automobile Headlamps

Projector

Floodlight for Sports Facilities

City and Road Lighting

Customization

Yuji is also able to do customizations to fulfill customers’ special requirements. This includes optical characteristics like CCT, CRI, or the whole spectrum, and physical properties like shape and dimensions.

For more information, please contact us at info@yujigroup.com.