LED灯珠光衰和失效试验及原因分析

LED Package Light Degradation and Failure Test and Cause Analysis

通过对LED灯珠光衰及失效的3种对比试验发现:在高温硫化试验中10pcs的LED灯珠平均光通量由初始时的69. 35 lm下降到62. 51 lm,平均光衰减率为9. 87%,且有5pcs的LED灯珠光衰减率> 10%;在高低温冷热冲击试验中10pcs的LED灯珠中有2pcs的LED灯珠不亮失效;在高温燃点老化试验中5pcs的LED灯珠的平均光通量由初始的74. 80 lm下降至65. 21 lm,光维为原来的87. 20%,平均色温由初始的3 950 K增加至4 079. 75 K,色温偏移129. 75 K。高温硫化试验中LED灯珠光衰在于环境中的硫化物与灯珠支架上的银发生反应生成黑色的硫化银;高低温冷热冲击试验中LED灯珠失效在于封装胶发生热胀冷缩,使封装胶移位,导致金线被拉断;高温燃点老化试验中LED灯珠光衰在于封装荧光胶在高温条件下透光性和气密性变差以及荧光粉性能变差,LED蓝光芯片发出的蓝光直接从封装胶的气孔中射出,导致光衰和色温漂移。

Three kinds of tests on the light degradation and failure of LED packages were conducted. It was found that the average luminous flux of 10 pcs LED packages dropped from the initial 69. 35 lm to 62.51 lm with an average ratio of light degradation around 9. 87% and the ratio higher than10% for 5 pcs LED packages in the high temperature vulcanization test. There were 2 pcs LED packages failed to light in10 pcs LED packages during the cycle of low temperature and high temperature test. The average luminous flux of 5 pcs LED packages dropped from the initial 74. 80 lm to 65. 21 lm in the high temperature aging test,with a luminous flux maintenance of 87. 20%. The average color temperature increased from the initial 3950 K to 4079. 75 K,with a color temperature shift of 129. 75 K. The reason of light degradation of the LED packages in the high temperature vulcanization test is that the sulfide in the environment reacted with the silver on the package holder producing black silver sulfide; And the failure of the LED packages in the lower temperature and high temperature test is due to a thermal expansion and contraction of the packaging glue resulting in the gold wire broken. The light degradation of the LED packages in the high temperature aging test is a result from a worse light transmittance and gas tightness of the packaging glue,and a deterioration of the performance of the phosphor,so that the blue light emitted from the LEDchip is directly radiated from the pores of the packaging glue resulting in the light degradation and color temperature shift.