Research And Optimization Of Thermal Congestion Effect Of High Power CSP White LED Flip Chip

Light emitting semiconductor(abbreviation: LED)lighting is a typical energy-saving,environmentally friendly green lighting source.Since the light emitting surface of the CSP package device is a five-sided light source,it has the characteristics of small size,light weight,high color saturation,wide color gamut,high efficiency and low consumption,long life,energy saving and environmental protection.Therefore,CSP-LED products will soon be applied to the use of backlights and car headlight light sources.This change has led to a vigorous development in the automotive lighting and liquid crystal industries.However,due to the small size of the high-power LED chip,the narrow emission spectrum,and the absence of infrared bands,the generated heat cannot be dissipated by heat radiation,so compared with the local heat flux density of traditional halogen lamps and xenon lamps Larger,especially for integrated light sources composed of multiple LED light source modules densely packaged in series or parallel,such densely distributed design requirements will inevitably lead to more complicated circuits and more serious heat accumulation problems,and It will reduce the luminous flux of the chip,deviation of the luminous color,and even cause the electronic components and equipment to burn out or aging,resulting in a reduction in the service life of the chip.Therefore,effective thermal management is the most effective way to improve LED performance.In this thesis,the electro-luminescence characteristics(EL)are used to study and optimize the thermal congestion effect of high-power blue and CSP white LED chip device structures.First,this paper gives a brief introduction to the characteristics,basic structure,and working principle of LEDs,and clarifies a series of adverse effects of the increase in junction temperature on LED performance.At the same time,it introduces the LED's characteristic parameters,heat transfer principle,heat dissipation theory and chip CSP packaging structure.Secondly,this paper studies the thermal congestion effect of blue chip and CSP-LEDchip devices by using electroluminescence characteristics(EL)by changing the arrangement pitch of the chips on the aluminum substrate.In this paper,the LED electroluminescence test system was used to characterize the EL spectrum,lumen efficiency,luminous flux,correlated color temperature and other photoelectric properties of samples with different arrangement intervals under variable current conditions.The results show that under low current(20mA ~400mA),with the increase of injection current,the photoelectric properties of blue and white light samples with different arrangement intervals show the same change rule,that is,the luminous flux and optical power increase linearly The luminous efficiency remains basically stable;however,the luminous efficiency and luminous flux of blue LEDs are lower than those of white chips.At high currents(1A ~ 1.5A),as the arrangement pitch decreases,the integrated intensity of the EL spectrum decreases,the color temperature rises,and the red ratio decreases;the luminous flux with an arrangement pitch of 0.2 mm is attenuated by84.58%,compared to the row The luminous flux attenuation of the cloth spacing of 3mm and5 mm is significantly slowed down,which is 8.96% and 3.58%,respectively.These phenomena are related to the band gap width,thermal stress,non-radiative recombination and other factors.Considering the actual production cost,when the arrangement pitch is 3mm,it is conducive to the heat dissipation,thereby improving the LED photoelectric performance characteristics and its own service life.In this paper,the area of high-power CSP-LED chip package ceramic plate is studied on the thermal congestion effect of the chip,and the photoelectric performance and structure optimization of the two chips packaged by phosphor and ceramic phosphor chip are characterized.In order to reduce the experimental cost and shorten the experimental period,eight chips are used to make four chips and six chips are used to make three chips.The experiment rules are analyzed to design a reasonable ceramic plate size and chip gap.The experimental results show that when the drive current reaches 0.5A of a single chip,the CSP of the eight-chip and six-chip self-heats and congests.The larger the current,the more light isblocked.When the current of the single chip is greater than 1A,the light intensity is almost No more increase;the white glue around the chip 4 will affect the proportion of blue light entering the air.Because the refractive index of silica gel is different from that of air,the light flux of the eight chip is lower than that of the four chip after thermal equilibrium;when the current increases to an extreme current above 1A The luminous flux of the ceramic fluorescent chip corresponding to the chip decreases more obviously,and the luminous efficiency of the ceramic fluorescent film is lower than that of the phosphor powder,indicating that the thermal congestion effect of the eight-chip and six-chip is more obvious,and the ceramic fluorescent film is more likely to cause the thermal congestion effect.The results of this experiment can provide a very meaningful reference value for the performance of products,the amount of materials used and the cost reduction in actual production.In summary,this paper mainly studies the heat dissipation performance of high-power CSP-LED devices through thermal characteristics test experiments,and optimizes the thermal congestion effect of CSP-LEDs reasonably.The reliability of high-power CSP-LED heat dissipation design was verified,and the reasonable spacing and packaging structure design of multi-core high-power CSP-LED chip were optimized.The experimental results obtained in this paper have certain guiding significance for the heat dissipation design of high-power CSP-LED.