Wafer level encapsulation process for LED array packaging

Solid-state lighting (SSL) using high brightness light emitting diodes (HB-LEDs) is the emerging trend for general lighting applications. It is expected a substantial portion of conventional incandescent and fluorescent lighting will be replaced by SSL in the next 5-10 years. There are two major factors controlling the propagation of HB-LEDs for SSL applications. One is the optoelectronic efficiency and the other is the cost. Both factors are closely related to the packaging of LEDs. Currently most LEDs are packaged on an individual component basis. Such a component level packaging process has relatively low throughput. Consequently it is more difficult to implement automation for large scale mass production, which is a critical element for low cost manufacturing. Therefore, a more efficient packaging process is in demand in the LED industry. In the present study, a wafer level encapsulation process for LED array packaging is developed. The silicon wafer is pre-fabricated with a pattern of grooves which serve as stoppers for epoxy flow in the subsequent encapsulation process. Epoxy encapsulant is dispensed from a syringe onto the wafer, and then is cured by UV light to complete the encapsulation process. This process can be easily automated and, hence, may increase the production throughput and reduce the manufacturing cost of LED packaging. In order to optimize the quality of this newly developed encapsulation process, there are several design and processing considerations to be investigated. These include the volume of encapsulant, the geometry of grooves, and some epoxy dispensing and curing parameters. A prototype with encapsulated LED arrays on a silicon wafer will be illustrated. Detailed discussion on those critical processing parameters will be given.