Solid-state lighting (SSL) using light-emitting diode (LED) as an alternative light source is an emerging technology. Compared with conventional light sources, LEDs have superior characteristics such as low energy consumption, long operation life, no toxic ingredient, and fast response time. Industrial emphasis has been placed on high power LEDs which are most likely to compete with conventional light sources. As the emerging illumination applications require white LEDs to provide higher performance while reducing cost to an acceptable range for consumers, therefore, low cost and high throughput manufacturing processes for LEDs are in urgent demand. The objective of this thesis is to introduce a low cost and high throughput method for the automation of LED mass production....[ Read more ]

Solid-state lighting (SSL) using light-emitting diode (LED) as an alternative light source is an emerging technology. Compared with conventional light sources, LEDs have superior characteristics such as low energy consumption, long operation life, no toxic ingredient, and fast response time. Industrial emphasis has been placed on high power LEDs which are most likely to compete with conventional light sources. As the emerging illumination applications require white LEDs to provide higher performance while reducing cost to an acceptable range for consumers, therefore, low cost and high throughput manufacturing processes for LEDs are in urgent demand. The objective of this thesis is to introduce a low cost and high throughput method for the automation of LED mass production.

Phosphor converted LEDs (pc-LEDs), which employ blue LEDs with yellow phosphor deposition to generate white light illumination is a widely used solid-state lighting source. This paper presents the integration of two major processes, namely, phosphor screen printing and moldless encapsulant dispensing, for wafer level pc-LED packaging. In the present study, the processing procedures and parameters of phosphor screen printing were developed and investigated in detail. The attributes of the phosphor layer by screen printing such as packing density, thickness, uniformity and adhesive strength, which control the performance of final white light illumination, were characterized. The results of the proposed screen-printing method in terms of packing density and thickness uniformity of yellow phosphor layer are comparable to those of settling and EPD methods.

Subsequently a moldless encapsulant dispensing process was applied at the wafer level. Silicone is selected as encapsulant material for its long term optical stability in elevated temperature. The processing procedures and parameters of the automatic moldless encapsulant dispensing were also investigated. The geometry characterization of the silicone encapsulation dome demonstrated a good control over the dome shape with the double-line microgrooves.

Optical performance of the packaged LEDs was evaluated. The chromaticity of the generated white light is close to the ideal white light. Meanwhile, a good uniformity in the color distribution was observed. The prototype of 4x4 and 5x5 white light LED arrays demonstrated that a LED wafer level packaging can be achieved with the integration of the two novel processes.