| At present,LED(Light Emitting Diode)is the fourth generation light source,with the advantage of energy saving,environmental protection and radiation free.The application of LED is more and more extensive,and industrialization has been realized gradually.The flexible FC-LED filament lamp based on flip chip packaging technology with the advantages of lower working voltage,lower power consumption and higher luminous efficiency,and is replacing the traditional light product.As the demand of LED lighting market is increasing,LED output power is increased,so higher requirements are put forward for the packaging technology level of inverted LED filament.Flexible FC-LED filament generated heat in the flip chip when working normally,and the heat accumulation increased the thermal resistance and junction temperature,which decreased the reliability and optical performance of flip chip.The existence of filament junction temperature has become an important issue affecting life,and the heat dissipation effect of the flexible FC-LED filament depends to a large extent on the heat transfer ability of the solder layer and the optimization of welding process of filament plays a key role.This article focuses on improving the welding process of flexible FC-LED filaments.The specific research results are as follows:1.The differences of the electric heating performance of the filament produced by different baking temperatures are compared.The results show that the soldering effect of the filament can be changed by adjusting the soldering temperature and the precise peaking temperature range.The soldering effect will be poor if the soldering temperature is too high or too low.The soldering effect is not good within the reasonable temperature range The best performance of inverted LED filament products.The reliability of the inverted LED filament is the highest in the peaking soldering range of 250-270?,the shearing strength of the solder joint is higher and the optical property is better.Besides,the junction temperature,the thermal resistance and the surface temperature are lowest in the temperature range of 250-270?,therefore,the welding temperature between 250-270? is more suitable for the flexible FC-LED filament welding process.2.The flexible FC-LED filament was prepared by using two kinds of lead free solder paste materials,Sn90Sb10 and SAC0307.Then,the differences of the optical,electrical and thermal properties of the two types of inverted LED lamps were compared by a series of tests.The results show that the shearing force of solder joints of filament bonded by Sn90Sb10 solder is higher,and the photoelectric properties of Sn90Sb10 filament are better.The junction temperatures and thermal images show that the PN junction temperature and surface temperature of Sn90Sb10 solder are lower than the filament soldered by SAC0307 solder.The higher thermal conductivity bonding material can improve the heat dissipation efficiency of PN junction of flip chip,thus reduces the junction temperature of the filament.At the same time,the void distribution of Sn90Sb10 solder layer is relatively small,and the void rate is relatively low.In conclusion,the soldering reliability and photoelectric properties of flexible FC-LED filament was improved by selecting the Sn90Sb10 solder paste.3.The influence of different solder paste coating processes on the photoelectric and thermal performance of flexible FC-LED filaments is focused on,and two different solder paste coating processes are used to bond the chips.Samples are prepared by post-baking.Because the soldering process uses a die-bonding machine to directly coat the solder paste one by one,while printing uses a printing machine for a large area,the squeegee will be printed on the substrate through the screen.Flexible FC-LED filament packaged by printing solder has higher shearing strength,lower junction temperature and higher luminous flux maintenance rate,and higher efficiency than that of the printing process filament. |
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