LEDs provide an environmental friendly light source for general lighting. They offer high efficiency, a long life span and do not contain hazardous substances. Wafer level packaging (WLP) was proposed to provide a new concept of packaging strategy, in which LED chips are assembled onto silicon wafer. WLP is a promising candidate for LED manufacturing, with the benefits of price competiveness, compact package integration and improved thermal performance. It allows the packaging of LED panels in a more efficient way.

Phosphor converted LEDs are the most commonly used components in generating white light luminaire. In traditional dispensing methods the phosphor particles are in direct contact with the LED chip. This might bring settling problem and thermal issues. Moreover, the c...[ Read more ]

LEDs provide an environmental friendly light source for general lighting. They offer high efficiency, a long life span and do not contain hazardous substances. Wafer level packaging (WLP) was proposed to provide a new concept of packaging strategy, in which LED chips are assembled onto silicon wafer. WLP is a promising candidate for LED manufacturing, with the benefits of price competiveness, compact package integration and improved thermal performance. It allows the packaging of LED panels in a more efficient way.

Phosphor converted LEDs are the most commonly used components in generating white light luminaire. In traditional dispensing methods the phosphor particles are in direct contact with the LED chip. This might bring settling problem and thermal issues. Moreover, the chip absorption of the back scattered light results in optical power lost. The situation can be improved by using a remote phosphor deposition method, in which the phosphor particles are separated away from the chip. The tightly controlled phosphor distribution contributes to improved light uniformity; less thermal issues were generated. Moreover, the back scattered light gets larger chance to be reflected by the substrate material and escape from the package.

Because of the leadframe structure, the implementation of the remote phosphor in traditional surface mount LED device (SMD) such as 3528, 5050 and high power package is very difficult to be achieved. Some luminaires realize the remote phosphor in a system level application by blending phosphor into the lighting diffuser. However, this method will consume a lot of phosphor material and hence substantially increases the total cost. The silicon wafer submount in WLP provides a flatbed structure instead of using a reflector cup to embed LEDs. This provides an excellent benefit for implementing remote phosphor in package level LEDs.

In this thesis, remote phosphor deposition method is combined with LED WLP technology to achieve a package level LED design. Two configurations were developed in sequence: at first the LED WLP with a phosphor cap structure was proposed; then a second structure was raised as an optimization of the first one, which uses LED WLP with a waffle pack shaped phosphor layer. For both packages, not only concept design, but also prototyping was made. Then the packages went through optical characterization for performance inspection. It was shown that by adapting the phosphor concentration, the packages can generate white light illumination covering a wide correlated color temperature (CCT) ranges from cold white to warm white. The packages produced uniform light distribution as well as good color consistency along different viewing angles.

Afterwards, the two packages were modeled in ray tracing optical simulation tool for parametric study. First the two key tracing parameters, the number of rays and the tracing threshold were investigated for the proposed model. Then the two packages went through simulation using the proper tracing parameters. The changes in light extraction and in light distribution were studied by changing the relative position and geometry of package components. Finally, the package was implemented into a light bulb system for study. The planar light distribution was investigated. A light bulb system containing high power components was also measured in the same scenario for comparison.