Heat Transfer Characteristics Of Electronic Device And Its Fatigue Analysis

With the development of electronic packaging technology, the performance of highly-centralized electronic products is substantially improved, while the heat flux dissipated by electronic device keeps increasing. According to statistic results, about 55% of electronic device's failures are caused by temperature load. Especially in a severe environment, heat failures is the key factor that determines the reliability of a system.The heat fatigue failure of solder joints is the main factor that causes failures to an electronic package structure. However, the relationship between electronic device's thermal characteristics and heat fatigue life is not clear, especially the coupling effect between thermal field, flow field and stress field of electronic devices under thermal cycle load is not completely known. In this context, thermal performance and heat stress of ball grid array(BGA) products under thermal cycle load is simulated and the influence factors of heat fatigue life is studied. For further applications in polar environment, the heattransfer characteristic of solid-state drive(SSD) under polarenvironment is carried out.In order to explore the thermal characteristic of electronic devices" plate-level components under thermal cycle load, anunsteady coupled model of heat transfer and thermal stress for BGA products is developed to verify the dynamic performance of flow field, thermal field and stress field. The model is numerically analyzed by finite element method to study how the physical fields affected by thermal load, which takes the time-dependency of power as thermal cycle. The results indicate that the point with the highest temperature among thermal load period always locates in the chip, which is considered as the heat source in this model, and the point with the maximum stress lies in the juncture between chip and the outermost solder joint of BGA.With the purpose of analyzing the role of environmental and power parameters on electronic devices" heat fatigue life, Darveaux method is used to predict the heat fatigue life of solder joints on the basis of the numerical calculation for BGA. The results indicate that the critical solder joint among BGA with the shortest heat fatigue life is locked in the outermost one of the joints array and the fatigue cracks appears in the upper part of this joint, connecting to chip. Moreover, more power, shorter shifting time, higher temperature and lower atmospheric pressure may lead to the shortening of critical joint's heat fatigue life, on which the effect of power and temperature is much more significant than that of shifting time and atmospheric pressure. When the environmental condition is constant, heat fatigue life is shortened 10730 times as the power rises from20MW/m~3to 100MW/m~3. On condition that the power is constant, heat fatigue life is shortened 107 times as the environmental temperature rises from -20? to 20?, meanwhile heat fatigue life drops by 37.4% as the atmospheric pressure decreases from 1bar to 0.1bar.Aiming to the special application of electronic devices, a simulation platform for polar environment is described and constructed to carry out thermal performance test experiment for SSD. The influence of polar environment on the thermal performance of solid-state drive (SSD) is presented. In this experiment, the working state of SSD are divided into the standby state and work state, and dynamic variation of different working state in polar environment is tested and monitored. The results indicate that there is always uneven temperature tendency when SSD is under standby state and work state, the temperature difference among printed circuit board of standby state is 2?, while the difference of work state is 5?. In the created polar environment(13?,0.55bar), the temperature rise of standby state(rated power 0.5W) is about 8?, while the rise of work state(rated power 2W) is 14?. On condition that the environmental temperature is constant, the temperature rise of standby state increases by 1.5?, and the temperature rise of work state increases by 2.5? as the atmospheric pressure decreases from 0.95bar to 0.15bar.