【作者】 陈桐；

【导师】 树学峰；

【作者基本信息】 太原理工大学 ， 固体力学， 2010， 博士

【摘要】 环氧模塑料是电子封装中芯片的外包封材料,是一种新型复合材料,它保证芯片免受灰尘、水分、冲击、振动和化学物质等外界因素的干扰,保证电子元器件正常工作。本文利用实验研究和数值模拟相结合的方法对环氧模塑料的微观力学性能和高应变率下的动态力学性能进行了研究,得到了以下结论：1.采用纳米压痕技术对电子封装用KL-4500-1 S型环氧模塑料进行了测试,得到了环氧模塑料的载荷位移曲线,弹性模量和硬度。利用纳米压痕硬度测得的实验数据,采用数值模拟的方法,建立了环氧模塑料压痕实验中载荷-位移曲线与其弹塑性材料参数之间的关系,确定环氧模塑料的特征应力和特征应变。建立了电子封装用KL-4500-1S型环氧模塑料的幂指数本构关系模型。2.利用带温控系统的微型霍普金森压杆(SHPB)装置,对直径6mm,高3mm的环氧模塑料圆柱形饼料试件进行了动态压缩实验,与准静态实验对比。研究结果表明环氧模塑料在准静态试验条件下,体现出脆性性质；在动态试验中随着应变率的增加,材料的屈服强度和流动应力有显著的提高,材料表现出应变率效应。在温度20℃-160℃范围内,随着温度的升高,环氧模塑料有轻微的软化,强度减弱,反之则材料变硬,强度增大。此外,环氧模塑料表现出应变硬化特征,即流动应力随应变增加而增加的现象。建立了电子产品正常工作温度60℃下的环氧模塑料的Cowper-Symonds弹塑性本构模型和朱-王-唐非线性粘弹性本构模型,确定了本构模型的材料常数,得到了环氧模塑料的动态本构关系。3.采用ANSYS/LSDYNA有限元软件,根据Input-G方法,以JEDEC规范中冲击条件B,作用时间为0.5ms的半正弦的加速度脉冲作为载荷,对VFBGA封装在板级跌落条件下环氧模塑料的可靠性进行了分析,得到以下结论：在跌落冲击条件下,机械冲击引起的PCB板弯曲或振动是导致环氧模塑料层发生破坏的根本原因；数值模拟分析结果发现,在跌落冲击中环氧模塑料的垂直应力是包封层发生破坏的主要应力；环氧模塑料层中部受到的破坏应力远大于其四周受到的应力；对应电路板长边方向受到的应力小于短边方向的应力。更多还原

【Abstract】 As the outer packaging of chips, Epoxy Molding Compound (EMC) is used to avoid the interference of external factors, such as dust, moisture, impact, vibration and chemical materials, etc. It is a kind of new-style composite material. So, electrical components would work normally with it. Combining experimental studies and FEM analysis, the micro-mechanical properties and dynamic properties under high strain rates of EMC were studied. The main procedures and conclusions are as following.1. The KL-4500-1S EMC was tested by using Hysitron’s nanomechanical testing instrument. The load-displacement curve, elastic module and hardness of EMC were obtained. Using reverse analysis method and numerical simulation, the relationship of load-displacement and elasto-plastic parameters of EMC were ascertained and the representative stress and representative strain of EMC were gained. Then the elastic-plastic constitutive equation for EMC was achieved.2. Using a micro Hopkinson pressure bar which includes temperature controlling system,a series of dynamic compressive experiments of EMC with diameter of 6mm and height of 3mm were conduct. Compared with quasistatic tests, the results indicate that EMC has fragility in quasistatic experiments, while in dynamic experiments, the yield strength and flow stress increase remarkably with the increase of strain rate. Therefore, EMC has effects of strain rate. Between the temperature of 20℃and 160℃, EMC is slightly softened and its strength decreases along the increase of temperature, on the contrary, if it becomes harder, its intensity will increase. Further more, EMC has properties of strain hardening, i.e. the flow stress increases with the increase of strain. When the adjacent temperature is 60℃, Cowper-Symonds elasto-plastic constitutive model and Zhu-Wang-Tang constitutive model were adopted. Using experimental results, the constants of above constitutive relationships were obtained, so, the constitutive equation of EMC was determined.3. Adopting Input-G method, limited in the B condition of JEDEC standards, the reliabilities of EMC loaded with Half-Sine Accelerate wave on which the action time was 0.5ms were analysed by using software ANSYS/LSDYNA, when VFBGA packaging was in the drop impact conditions. The results indicate that the bending and vibration of PCB caused by mechanical impact are the basic reason for EMC’s failure. The damage of packaging layer is aroused by vertical stress of EMC. Failure stress in the center of EMC is higher than that in the periphery and corresponding circuit board has higher stress in the long edge than in the short edge.更多还原