Visual Research On Thermal Mismatch Between Package Colloid And Lead Frame In Light-Emitting Diodes

With the development of society and economy, global energy and environmental issues isbecoming increasingly prominent. As a solid state lighting, LEDs have become human’sconcernced object because of its environmental protection, energy-saving, etc. As a newtechnology research field, there are many problems that need to be resolved quickly, whilereliability issues is the most basic one. The LED devices will inevitably experience the reflowsoldering process in the course of using, which the temperature is too high resulting packagecolloid’s cracking failures that affect the reliability of LEDs. In this paper, first of all, acontrolled temperature heating platform is designed by referencing the structure of reflowoven and the soldering temperature curve of LED devices. Then the process of thermalmismatch between package colloid and lead frame in light-emitting diodes is simulatedthrough thermal-stress analysis. After that, the visual experiment on thermal mismatchbetween package colloid and lead frame in light-emitting diodes is researched. At last, beforeand after thermal mismatch between package colloid and lead frame in light-emitting diodes,the air-tightness and photoelectric parameters are analysed comparatively. The main researchcontents are as follows:(1) Controlled temperature heating platform design for LEDs thermal mismatch researchThe controlled temperature heating platform is designed by referencing the structure ofreflow oven and the soldering temperature curve of LED devices, mainly including the overalllayout design of heating platform, the design of temperature curve and the adjustments of PIDparameters. This controlled temperature heating platform can debug the approximate reflowsoldering temperature curve, which has the ability to accurately simulate the failure process ofLED devices’reflow soldering course.(2)Numerical analysis of thermal mismatch between package colloid and lead frame inLEDsThe thermal mismatch process of LEDs is analysed by utilizing the commonly usedfinite element analysis software ANSYS workbench V13.0. The temperature distribution, theequivalent stress distribution, the equivalent strain distribution and the equivalent deformationdistribution of LEDs that have two different type of package colloids and different lead framestructures at a specific temperature load are researched respectively, which can providetheoretical guidance for experimental research of thermal mismatch between package colloidand lead frame in LEDs. (3) Visual experimental research of thermal mismatch between package colloid and leadframeFirstly, the thermal characteristics of two LED package colloids are studied, confirmedthe thermal properity differences between them. Secondly, the thermal mismatch process ofLEDs that have two different type of package colloids and different lead frame structures areresearched experimentally and visually at two different temperature curves, which can obtainthe performance parameters such as whether to crack, initial temperature of cracking, endedtemperature of cracking and total time of cracking etc. Then the influence degree of differentaffecting factors about thermal mismatch between package colloid and lead frame in LEDswill be observed. Finally, the air-tightness and photoelectric parameters are analysed beforeand after thermal mismatch between package colloid and lead frame in light-emitting diodescomparatively.