Research on COB-LED light source with tunable CCT based on screen printing and flip chip technology

Based on the fact that flip chip without front-side bonding wire, a correlated color temperature (CCT) tunable chip on board (COB) light emittin g diodes (LED) light source was fabricated, by screen printing technology before the phosphor was coated on the whole luminous surface. A part of the blue LED chips in the light source excites the fluorescent glue to produce a warm white light (CCT = 2631 K), and the other part produces cool white light (CCT = 6181 K). When changing the driving current ratio of the two parts of the chips, the CCT of COB LED light source can be continuously adjusted between warm and cool white light. According to the measured data, the relationship between the CCT and the current ratio of the two parts is obtained by fitting. Within the tunable range of the CCT (2631 K to 6181 K), the color rendering index (CRI) is about 90. The minimum is 89.3 and the maximum is 93.1. While achieving tunable CCT and high CRI, the LED light source has a luminous flux of 1938.76 lm on a circular surface with a diameter of 11 mm. The overall luminous efficiency is close to 100 lm/W.