Structure And Thermal Simulation Analysis Of Chip Scale Packaged LED

Chip scale package has been applied to the LED industry in recent years,but its thermal performance still needs to be sufficiently studied.In order to supplement the blank in this field,thermal performance of chip scale packaged LED was studied in this paper.By the method of modeling and simulation,the influence of solder materials?substrates and underfills was studied,and quantified by influence factor through inferring and fitting the relationship of performance and conductivity.Moreover,the influence of the separation distance between chips and package density of multi-chip package module was studied.Finally,the simulation results were verified by experiments.The main work and achievements can be summarized as the following:(1)Thermal performance of chip scale packaged LED was influenced by thermal conductivity of solders?substrates and underfills.Thermal conductivity of substrates had the greatest influence on the performance with an influence factor of 120.60.The influence of solders was in the second place with an influence factor of 8.54 and underfills has a lowest effect.Its influence factor was 4.13.Thus,increasing the thermal conductivity of substrate will have a significant effect on the performance of thermal conductivity of chip scale packaged LED.(2)For chip scale packaged LED with total power of 18 W using the radiator mentioned in this paper,the temperature of P-N junction was 125.6 ? and relevant thermal resistance was 1.75 K/W under the condition of natural convection and the thermal conductivity of solders tended to be infinite;when thermal conductivity of substrates tended to be infinite,the junction temperature was 120.32 ? and relevant thermal resistance was 1.41 K/W;when thermal conductivity of underfills tended to be infinite,the junction temperature was 123.11 ? and relevant thermal resistance was 1.62 K/W.(3)The influence of substrates thickness on thermal performance of chip scale packaged LED was related with the thermal conductivity of the substrates.When the thermal conductivity of the substrate was low,thermal performance was improved with the decreasing of thickness.When thermal conductivity was high,there was an optimal thickness which provides the best thermal performance and the optimal thickness will increase with the increasing of thermal conductivity of substrates.(4)Thermal performance of chip scale packaged LED modules which were packaged upon an aluminum substrate with a diameter of 25 mm and a thickness of 1 mm were computed and the study showed that the chip junction temperature was closely related to chip power and distance between chips.To achieve technical requirement of junction temperature below 120 ?,distance and chip power both need to be considered.When the distance was 3.5 mm only the single chip power of 0.5 W could meet the requirement.As the distance increased the chip power could rise gradually.When the distance was 7.25 mm chips whose power was less than 3 W could be applicable to the packaging.While the total input power was certain thermal resistance of module decreased with the increased of packing density.When the packing density was 15.13 % module thermal resistance dropped to 2.26 K/W.Chip scale package is development direction of the next generation of LED packaging because of its lower thermal resistance.