Study On Performance And Reliability Of High Power Density COB LED Module

With the LED chip power continues to increase and the LED module size continues to decrease,high-power LED modules generate more and more heat,if the heat cannot be dissipated in time,life and reliability will greatly reduce,also may lead to quality problems.In this paper,a 25W high power density white LED module bonded with nano-silver paste is introduced.First,the encapsulation materials,interconnection process and aging test system are introduced and analyzed,we analyzed the change of the photoelectric parameters of the 25W high power density white LED module with different die attach materials and different ambient temperatures.Temperature has a great impact on the reliability of LED modules.As the environment increased,the light output decreased,the junction temperature increased,the relative brightness decreased.When the ambient temperature is above 200~oC,LED module will quickly failed in a short time.The LED module use nano-silver paste has obvious advantages than the silver epoxy.Thirdly,the mechanical reliability of 25W high power density white LED module was investigated by thermal cycling test.The effect of thermal shock on the bonding strength between chip and substrate was analyzed.First,We use die shearing tester to test the shear strength after one specific thermal cycle.Then,the cross-section of the LED module after shear test was analyzed.At the same time,the LED module with encapsulated silicone and without-encapsulated silicone were tested to distinguish the differences in failure modes.Finally,an accelerated test method for lumen decay failure under high temperature conditions is introduced to shorten the experimental time to 2000 hours.The required for the accelerated test method is obtained by calculating the lumen-maintain critical curve at the accelerated test temperature.In addition,We took life expectancy prediction of the 25W high power density white LED module under normal working conditions at room temperature,the room temperature life is about4.07×10~6 hours.