Thermal characteristics evaluation for board-level high performance flip-chip package equipped with vapor chamber as heat spreader

Thermal analysis was performed in this work to compare the thermal performance of a board-level high performance flip-chip ball grid array package equipped with solid Cu or vapor chamber (VC) as the heat spreader and Al-filler gel or In solder as the thermal interface material (TIM). The effect of different heat source sizes was also examined. Numerical results indicate that for the particular test vehicle under a power dissipation of 160 W, the thermal performance is remarkably enhanced by switching TIM from Al-filler gel to In solder while the enhancement by using VC instead of solid Cu heat spreader is only observable when In solder is incorporated. Moreover, the performance of VC gradually enhances then retards as the heat source size decreases. The retardation can be attributed to the more dominant role of die in heat dissipation when the heat source size gradually shrinks.     

Interconnect resistance characteristics of several flip-chip bumping and assembly techniques

Several flip-chip interconnection methods were compared by measuring interconnect resistance before and after exposure to environments including pre-conditioning, 85°C/85% RH exposure, 150°C storage, and 0–100°C temperature cycling. The goal was to determine an acceptable low-cost, reliable method for bumping and assembling chips to flexible or rigid substrates using flip-chip assembly techniques. Alternative flip-chip bumping methods are compared to a traditional wafer solder bumping method. Flip-chip interconnection methods evaluated included high lead content solder, silver filled conductive adhesive, and gold stud bumps. Under bump metallurgies evaluated included bare aluminum, evaporated Cr/Cr–Cu/Cu, and electroless nickel plating.     

大功率LED灯具散热器的优化设计研究

LED的散热性能对其寿命有至关重要的影响,而现阶段LED的散热器设计方法很多依靠的是经验值。本文针对这一问题,提出一种散热器的优化设计方法,该方法首先基于大量实验数据研究了散热器翅片单一因素（包括翅片高度、翅片间距、翅片厚度、底板厚度）对散热性能的影响,然后运用正交试验法,综合分析了各因素对散热性能的影响程度,最终得到了翅片参数的最优水平组合。最后本文利用此方法,设计了一款新的散热器,实验表明该LED灯源芯片温度降低,并计算了优化后翅片的效率。