【作者】 李智；

【导师】 游敏；

【作者基本信息】 三峡大学 ， 机械设计及理论， 2008， 硕士

【摘要】 本文采用数值模拟的方法,以单搭接接头及常见到的QFP电子封装受载胶接接头为主要的研究对象,以优化胶接接头应力分布、提高胶接接头的强度为目标,对在动载荷和温度载荷作用下的上述胶接接头的应力响应及其影响因素进行了研究,得出了如下主要结论:1)在塑性模型的基础上,用APDL高级语言编制循环程序,研究了加载速率对单搭接接头应力分布的影响。计算结果表明:终止载荷一定时,加载速率对接头应力分布有一定的影响:当加载速率比较大时,SEQV等效应力峰值较小;反之,当加载速率比较小时,SEQV等效应力峰值较大。实际应用过程中,胶接接头承受不同加载速率载荷的可能性很高,这对了解实际应用中的胶接接头的承载有着重要意义。2)在弹塑性模型的基础上,首次研究了冲击载荷对胶接接头应力分布的影响。计算结果表明:加载速率为3m/s至7m/s时,胶层中最高应力所在点的SEQV等效应力从101MPa提高到156MPa,当冲击载荷作用到上部被粘物的一瞬间,胶层中的最大应力即超过了胶粘剂的强度极限,胶层可能被迅速撕裂而导致接头分离;当加载速率为0.3m/s至0.7m/s时,随着速率的增大,胶层中最高应力所在点的SEQV等效应力从20.2MPa提高到55.6MPa,胶层中发生了弹塑性变形,在撞击结束后,胶层中最大应力又快速下降,且发生粘弹性响应;在冲击载荷的作用下,应力波首先从接触点处开始传播,当脱离接触后,应力波向后部传播并迅速减小,即胶粘剂本体的卸载扰动(如弹性作用)产生了反向加载波,与外载波的作用相互抵消。3)用数值模拟的方法研究了胶层不同程度的吸湿对单搭接接头应力分布的影响,计算结果表明:随着吸湿程度的增大,胶粘剂的屈服强度下降很快;胶层中的应力由胶瘤承载逐渐转变为搭接区中央的胶层承载,胶瘤的作用越来越弱化;在相同承载条件下,随着胶层吸湿程度的增加,接头的承载能力下降。4)建立了单搭接接头的断裂力学模型,研究了不同裂纹长度对单搭接接头应力分布的影响,计算结果表明:随裂纹长度的增加,裂纹尖端SEQV等效应力逐渐增大,并且裂纹尖端的应力远大于搭接区中央的胶层应力,由此可知高值的裂纹尖端应力为裂纹在胶层中的扩展提供了驱动力;研究了I型和II型断裂因子同初始裂纹长度及外载荷大小的关系,结果表明:随裂纹长度的增加,I型和II型断裂因子呈逐渐增大的趋势;随外载荷的增大,I型和II型断裂因子也呈逐渐增大的趋势。5)在黏塑性模型的基础上,用APDL高级语言编制的循环程序,用数值模拟的方法研究了温度加载率、保温时间以及循环次数这三个因素对广泛应用的焊料63Sn37Pb温度循环下QFP焊点界面应力的影响。计算结果表明:温度加载率对63Sn37Pb焊点界面应力的影响非常大:温度加载率越大,应力峰值越高;保温时间对63Sn37Pb焊点界面应力也有一定影响,时间越长,应力峰值越大;循环次数对63Sn37Pb焊点界面应力也有影响,但在循环10次后这种影响开始减弱。6)在多线性随动强化模型的基础上,用APDL高级语言编制的循环程序,首次研究了温度载荷作用下的QFP微电子封装结构中不同种常用封装胶粘剂形成的胶点的界面应力及其应力应变滞后环,计算结果表明:3种常用封装胶粘剂与FR-4板界面处的应力相差较大,以ASA丙烯腈胶形成的胶点的SEQV等效应力最小,有利于提高电子封装器件的连接可靠性;经历10次温度循环加载后,ASA丙烯腈胶形成的胶点上应力累积的最大值一般出现在左端倒角、右端内倒角交界处这两个部位。更多还原

【Abstract】 In this paper, a single-lap joints and electronic package to the common electronic QFP package containing the plastic joints as the main object has been studied by finite element method to optimize the distribution of joint stress and improve the joint strength, the plastic joints of the stress response and its impact factors under the dynamic load and load temperature have been investigated, the results indicated that:1) Based on the plastic model, the effect of the loading rate on stress distribution of single-lap joint was studied though high-level language of the APDL cycle process. The results shows that, the loading rate on joint stress distribution have a certain impact on termination of certain load: When loading rate is relatively larger, SEQV peak was smaller. Contrarily, loading rate is relatively smaller, SEQV peak was larger. The plastic joints possibly bear different loading rate in practical application, which has great significance of understanding the practical application of the plastic bearing joints.2) The effect of high or low-speed impact load on stress distribution of joints was studied using elasto-plastic model. The results show that, the stress of the most dangerous point in adhesive layer didn’t change greatly with time under high-speed loading, which because when the hammer hit by stick-on, the adhesive layer was torn quickly. Under low rate loading, with the increase of the rate, the stress of the most dangerous point in adhesive layer increased. When the hammer was hit on the adherend, the stress of adhesive layer increased rapidly. The stress of adhesive layer has viscoelastic response to time after the collision.3) The effect of different levels of moisture in adhesive layer on the stress distribution of single-lap joint was studied by numerical simulation .The results showed that, With the increased level of moisture, the yield strength of adhesives decreased greatly; main load was born by the adhesive layer in fillet transferred to middle zone with the weak function of the fillet. Under the same condition, the load bearing of joint declines as the moisture level of adhesive layer increases.4) Based on the fracture mechanics model of a single-lap joint, the effect of crack length on the distribution of stress in a single-lap joint was studied. The results showed that, crack point SEQV equivalent stress gradually increased as the increase of the crack length, and the stress of the crack point is far greater than the stress of the adhesive layer in the central area of the overlap, thus the high-value stress of the crack point provided a driving to the expansion of the crack in the adhesive layer; studied on the relationship between the fracture gene of the type I and type II and the initial crack length and the size of the load, the results showed that, the fracture gene of the type I and type II gradually increased trend as the increase of the crack length; with the increasing load, I and type II-type fracture Factor was also gradually increasing trend. As the size of the load increasing, the fracture gene was also gradually increasing trend.5)Based on the viscous plasticity model, using the cycle process which workout by the APDL senior language, the first time studied on the effect of temperature loading rate, holding time and cycle times on the QFP spot interface stress in the wider application of the solder temperature cycle under 63Sn37Pb the impact by the numerical simulation. The results showed that, temperature loading rate had a great impact on 63Sn37Pb spot interface stress: the greater the temperature loading rate, the higher the peak stress; holding time had a certain impact on 63Sn37Pb spot interface stress: the longer the time, the higher the peak stress; the number of recycling also had the impact on the 63Sn37Pb spot interface stress, but the impact began weakened after the loop 10 times.6) Based on the multilinear kinematic hardening model, using the cycle process which workout by the APDL senior language, the first time studied on the interface stress and stress-strain loop which formed by different common packaging adhesive in the QFP Microelectronics Packaging under the temperature impact, pointed out: the interface stress between this three kinds of commonly used packaging adhesives and FR-4 board was very different, the SEQV equivalent stress in the adhesive point which formed by ASA acrylonitrile is minimum, would help improve the reliability of the connection in the electronic packaging device; after experiencing 10 times the temperature cyclic loading, the maximum of the stress accumulated which formed by ASA acrylonitrile was generally in the left chamfer and the right inner chamfer crossing.更多还原