Micro-rolling Forming of Light Extraction Structure on Substrate for LED Chip-on-Board Package

Abstract

The light extraction structure (LES) on substrate for chip-on-board (COB) packaging light-emitting diodes is an effective means to address the intrinsic problem—the total internal reflection occurred within a COB packaging device. This work develops a new manufacturing method—micro-rolling forming to machine inverted pyramid LESs with high efficiency and low cost. In this method, a roller with closely arrayed micro pyramid teeth is designed and rolled on a copper substrate. A finite element model is established to analyze the forming process of the inverted pyramids and the forming process can be divided into four stages: elastic stage, yielding stage, hardening stage, full plastic deformation stage. The stress and strain mainly concentrate on the contact zone with the micro tooth abdomen. In this contact zone, the stress plateaus in the full plastic deformation stage are high and long, which drives the inverted pyramid formation. The side length of the inverted pyramid increases, while the cone angle decreases with the rolling depth increasing. Whereas the side length and cone angle vary slightly with the rolling speed increasing. The better rolling depth and speed for LES forming are 0.3–0.4 mm and 10–20 mm/s, respectively.