## 4 Discussion
### Modeling of Generalized Coupled Acceleration Model  
Under high-temperature and high-humidity environments, metals and certain organic materials are prone to corrosion, resulting in the degradation of the performance of electrical connection components and packaging materials and increasing the risk of moisture penetration into LED packaging materials, which may cause physical and chemical changes in the materials, such as discoloration, softening, or deterioration. Therefore, it is believed that there is a coupling relationship between temperature and humidity; high temperature will accelerate the aging process of LED materials, especially organic materials (such as packaging resins) and certain semiconductor materials (such as chips and connecting wires) may fail or deteriorate due to high temperature. High current will cause increased heat inside the LED device, which may exceed the thermal capacity of the material and the processing capacity of the heat dissipation design, thereby affecting the stability and life of the material. Therefore, it is believed that there is a coupling relationship between temperature and current; in a high-humidity environment, water vapor can easily penetrate into the LED packaging material, causing the mechanical properties of the material to deteriorate, such as yellowing and cracking. Under high current, the heat generated by the LEDs increases, which will further aggravate the degradation of the material. This coupling of environment and electrical stress will accelerate the degradation process of the LEDs and shorten their life. Humidity will affect the interface between the LED chip and the package, which may cause current leakage, short circuit, and other problems. Under high current conditions, the interface problem will be more serious, which will lead to the degradation of the electrical performance of the LEDs, such as reduced luminous efficiency and color temperature drift. The combined effect of high humidity and high current will enhance the electromigration effect; that is, the metal atoms in the metal wire migrate under the action of the electric field, resulting in the breakage of the wire or increased resistance. This phenomenon is particularly significant under high current density and may eventually lead to the failure of the LEDs. Under the coupling of humidity and current, the failure mode of the LEDs may be more complex and difficult to predict. In this case, the reliability test results of the LEDs may be worse than under a single stress condition, and the failure rate in actual application will also be higher. In this experiment, increasing the current stress under humid conditions will reduce life, so it is believed that there is a coupling relationship between humidity and current. That is, this experiment has coupling terms of temperature and humidity, temperature and current, and humidity and current with three stresses. According to the acceleration model, the three-stress acceleration models without considering coupling, without considering wet-electric coupling, and considering the actual situation are as follows in Equation (15):  
\[ \begin{array}{l}\ln L_{1}(\alpha_{10},\alpha_{11},\ldots,\alpha_{14})=\ln \alpha_{10}-\alpha_{11}\xi_{1}-\alpha_{12}\xi_{2}-\alpha_{13}\xi_{3}\\ \ln L_{2}(\alpha_{20},\alpha_{21},\ldots,\alpha_{25})=\ln\alpha_{20}-\alpha_{2 1}\xi_{1}-\alpha_{22}\xi_{2}-\alpha_{23}\xi_{3}-\alpha_{24}\xi_{1}\xi_{2}- \alpha_{25}\xi_{1}\xi_{3}\\ \ln L_{3}(\alpha_{30},\alpha_{31},\ldots,\alpha_{37})=\ln\alpha_{30}-\alpha_{3 1}\xi_{1}-\alpha_{32}\xi_{2}-\alpha_{33}\xi_{3}-\alpha_{34}\xi_{1}\xi_{2}- \alpha_{35}\xi_{1}\xi_{3}\\ -\alpha_{36}\xi_{2}\xi_{3}-\alpha_{37}\xi_{1}\xi_{2}\xi_{3}\end{array}