BGA焊点界面化合物纳米压痕力学行为

利用纳米压痕法对BGA焊点(Cu,Ni)₆Sn₅,Cu₆Sn₅,Cu₃Sn界面化合物(IMC)进行了压痕试验.基于Oliver-Pharr法确定了(Cu,Ni)₆Sn₅,Cu₆Sn₅,Cu₃Sn的弹性模量和压痕硬度,研究了加载速率对IMC纳米压痕力学行为的影响及其变化规律.结果表明,锯齿流变效应与加载速率的大小是相关的.在加载速率较小的情况下(Cu,Ni)₆Sn₅,Cu₆Sn₅,Cu₃Sn都具有锯齿流变效应,但程度不同;在加载速率较大的情况下(Cu,Ni)₆Sn₅,Cu₃Sn锯齿流变效应不明显,而Cu₆Sn₅的锯齿流变效应相对明显.(Cu,Ni)₆Sn₅,Cu₆Sn₅,Cu₃Sn界面IMC的弹性模量分别为126,118,135 GPa;压痕硬度分别为6.5,6.3,5.8 GPa;含镍的(Cu,Ni)₆Sn₅化合物弹性模量和压痕硬度均比Cu₆Sn₅的值要高.     

基于纳米压痕法的无铅BGA焊点的循环力学行为

采用纳米压痕法通过循环加载卸载方式研究了最大载荷、循环次数及保载时间对Sn-3.0Ag-0.5Cu和Sn-0.3Ag-0.7Cu 2种钎料BGA焊点循环性能的影响.结果表明,Sn-Ag-Cu系无铅BGA焊点的循环性能具有很大的载荷依赖性,随着最大载荷的增加,BGA焊点的损伤累积增加且前几周循环中损伤累积很大,其后逐渐减小并趋于稳定;循环次数增加,使BGA焊点抵抗变形的能力稍有降低;保载时间增加,蠕变位移不断增加,蠕变和疲劳共同作用会加速焊点失效;Sn-0.3Ag-0.7Cu钎料BGA焊点的能量损耗大于Sn-3.0Ag-0.5Cu钎料BGA焊点.     

ADB610钢焊接接头概率疲劳裂纹扩展分析

采用焊条电弧焊方法对ADB610钢进行焊接,对焊接接头进行疲劳裂纹扩展试验,研究其概率疲劳裂纹扩展规律.采用两步七点递增多项式拟合方法,计算了一系列相同裂纹长度下母材区、热影响区和焊缝区的对数裂纹扩展速率方差和存活率分别为50%,90%,95%,99%,99.9%的裂纹扩展速率.结果表明,总体上母材区的裂纹扩展分散性最小,热影响区其次,焊缝区分散性最大;而且总体上存活率相同时,在裂纹扩展的初期,母材区的裂纹扩展速率最快,焊缝区的裂纹扩展速率最慢;在裂纹扩展末期,三区域的裂纹扩展快慢相当;随着存活率增大,三区域裂纹扩展快慢差别不大时所对应的裂纹长度减小.     

含全埋藏裂纹的T10钢焊接接头电磁热止裂分析

通过有限元分析方法,计算出含有圆形全埋藏裂纹的焊接接头电磁热止裂温度场分布,并通过ZL-2放电装置,对含圆形埋藏裂纹的T10钢焊接接头进行电磁热止裂试验。研究结果表明,止裂瞬间,焊接接头中埋藏裂纹裂尖处温升超过金属熔点,裂尖熔化、钝化,阻止了裂纹的进一步扩展;止裂后,在裂尖附近有白亮层组织出现。止裂前后的T10钢焊接接头力学性能测试表明,止裂后焊接接头所能承受的最大扭矩和抗扭强度提高了约17%。     

BGA封装器件焊点抗剪强度的试验

采用微焊点强度测试仪研究了Sn-Pb共晶钎料BGA（球栅阵列封装技术）封装器件焊点的抗剪强度，并对不同直径的BGA球焊点的抗剪强度进行了比较。研究结果表明，在相同条件下，BGA球直径越大，抗剪强度越小，共晶钎料BGA球焊点的抗剪强度比锡铅合金钎糕点自身的抗剪强度大。     

无铅BGA焊点温度循环失效机理

随着无铅化进程的逐渐深入,针对无铅焊点的长期可靠性,业界已经做了大量研究,但是试验参数的选取一直也是业界比较有争议的问题,其关注点也是基于失效机理和失效模式的考虑。文中主要从金相和断口的角度出发,对温度循环焊点的失效特征进行了总结,指导后续可靠性试验及失效分析的开展。     

Fatigue crack propagation behavior in dual-phase steel

The fatigue crack propagation in dual-phase steel was studied with the objective of developing ferriticmartensitic microstructures via intercritical annealing and thermomechanical processing. It was found that the changes in fatigue crack propagation rates and in the threshold stress intensity range, ΔK _th, resulting from microstructural variations, were directly related to tensile strength in the same manner that was observed in other types of structural steels. It was also observed that the relationship between tensile strength and fatigue crack propagation in intercritically annealed and thermomechanically processed dual-phase steel was much the same as for conventional steels of similar strength level.     

TC4ELI合金疲劳裂纹尖端塑性区对裂纹扩展的影响

研究了TC4ELI合金片层组织与短棒α组织中的疲劳裂纹尖端塑性区及裂纹扩展行为.首先通过SEM及TEM观察比较两种显微组织下的疲劳裂纹尖端塑性区,讨论两种显微组织中裂纹尖端塑性区对疲劳裂纹扩展路径及扩展断口的影响,分析裂纹扩展路径和裂纹尖端塑性区对裂纹闭合及裂纹扩展速率的影响.结果表明:与短棒α组织相比,片层组织中具有较大的裂纹尖端塑性区及曲折的裂纹扩展路径,并最终从疲劳裂纹闭合的角度,解释了片层组织具有较低的疲劳裂纹扩展速率的原因.     

The influence of temperature on creep behavior of Cu particle enhanced SnPb based composite soldered joints

Creep property of solder alloys is one of the important factors to affect the reliability of soldered joints in SMT(surface mount technology). Particle-enhancement is a way to improve the properties of solder alloys and has caused much more attention than before. Temperatures applied to soldered joints are one of the primary factors of affecting creep properties of particle enhancement composite soldered joints. In this paper single shear lap creep specimens with a 1 mm2 cross-sectional area were fabricated using Cu particle enhancement 63Sn37Pb based composite soldered joints and 63Sn37Pb eutectic soldered joints to examine the influence of temperature on creep behavior of soldered joints. Results indicated that the creep resistance of soldered joints of Cu particle enhancement 63Sn37Pb based composite soldered joint was generally superior to that of the conventional 63Sn37Pb soldered joint. At the same time, creep rupture life of the composite soldered joint was declined with increasing temperature and drop faster than that of the conventional 63Sn37Pb eutectic soldered joint.     

The influence of temperature enhanced SnPb based on creep behavior of Cu particle composite soldered joints

Creep property of solder alloys is one of the important factors to affect the reliabdity of soldered joints in SMT （surface mount technology）. Particle-enhancement is a way to improve the properties of solder alloys and has caused much more attention than before. Temperatures applied to soldered joints are one of the primary factors of affecting creep properties of particle enhancement composite soldered joints. In this paper single shear lap creep specimens with a 1 mm^2 cross-sectional area were fabricated using Cu particle enhancement 63Sn37 Pb based composite soldered joints and 63Sn37 Pb eutectic soldered joints to examine the influence of temperature on creep behavior of soldered joints. Results indicated that the creep resistance of soldered joints of Cu particle enhancement 63Sn37Pb based composite soldered joint was generally superior to that of the conventional 63Sn37Pb soldered joint. At the same time, creep rupture life of the composite soldered joint was declined with increasing temperature and drop faster than that of the conventional 63Sn37 Pb eutectic soldered joint.     

基于原位SEM的激光-MIG复合焊接7075-T6铝合金疲劳裂纹扩展行为

通过扫描电镜原位观察激光复合焊接头各区裂纹的扩展行为. 结果表明,焊缝各区组织的不同使得疲劳裂纹扩展行为发生明显改变,疲劳裂纹位于焊缝中心时,裂纹总体沿着垂直于载荷主轴的方向扩展;疲劳裂纹位于热影响区时,裂纹大致成"Z"字型路径进行扩展;疲劳裂纹在焊缝中心和热影响区扩展时都存在二次裂纹;疲劳裂纹在母材区扩展时,呈现出单一和典型的裂纹扩展模式. 此外,通过原位SEM观察获得不同循环周期下的裂纹扩展长度,进而推算得到7075-T6铝合金接头各区内疲劳裂纹扩展速率的Paris公式.     

WLCSP器件结构优化模拟及无铅焊点可靠性

构建WLCSP144器件四分之一模型,研究无铅焊点阵列的应力-应变响应.结果表明,焊点应力-应变大小和焊点的位置有密切关系,中心焊点的应力-应变最小,拐角焊点的应力-应变最大,应力和焊点位置的关系为σ(x,y)=1.78x+1.78y+0.33,焊点蠕变应变和焊点位置的关系为ε(x,y)=0.006x+0.006y+0.009.同时发现焊点可靠性与器件结构有明显关系,在结构中选择聚合物作为封装材料对应的焊点可靠性较低,应该选择与PCB线膨胀系数较为匹配的材料最为适宜.焊点阵列数(焊点间距相同)的增加会降低焊点的可靠性,这主要是和阵列拐角焊点与芯片中心的距离有明显的关系.     

2397合金高周疲劳性能及裂纹萌生扩展行为

研究了2397-T87铝锂合金的高周疲劳性能及裂纹萌生扩展行为。结果表明:在应力比R=0.1时,2397-T87铝锂合金L方向、LT方向和ST方向光滑试样(K_t=1.0)的疲劳寿命极限分别约为192,243和151 MPa;缺口试样(K_t=3.0)的疲劳寿命极限分别约为72,78和70 MPa。其疲劳裂纹主要萌生于试样表面,以及氧化物、夹杂等脱落形成的空洞,Al(CuFeMn)第二相杂质粒子。驻留滑移带(PSB)和晶粒取向对其疲劳裂纹早期扩展有重要影响。     

63Sn37Pb钎焊接头稳态蠕变本构方程的建立

采用高温蠕变测试装置，以简化的Dorn公式为基础．对63Sn37Pb微型单搭接钎焊接头蠕变应变进行了测试．确定了应力指数、蠕变激活能以及相关常数。建立了63Snd7Pb钎焊接头稳态蠕变本构方程，描述了稳态蠕变速率与应力和温度相关性。结果表明，钎焊接头应力指数和激活能均低于钎料本身的应力指数和激活能．说明钎料本身蠕变行为并不能完全代表钎焊接头的蠕变行为。     

CuCGA器件焊点热疲劳行为数值模拟

基于蠕变模型构建 Sn3.9Ag0.6Cu 和 63Sn37Pb 钎料的本构方程,分析铜柱栅阵列封装(CuCGA)器件在不同温度循环载荷下焊点的应力-应变分布.结果表明,不论温度循环如何变化,距器件中心最远处焊点的等效蠕变值总是最大,且均有明显的应力集中现象,在热循环作用下,很容易在该焊点处最先产生裂纹,导致器件失效,是整个器件最脆弱的焊点.同样温度载荷下,Sn3.9Ag0.6Cu 焊点的应力应变总是小于 63Sn37Pb 焊点,而随着温度循环范围的减小,两种钎料的应力和蠕变值均有所降低.另外,预测发现同样温度循环载荷条件下 Sn3.9Ag0.6Cu 焊点具有较高的疲劳寿命.

Abstract：

The constitutive equation of Sn3. 9Ag0.6Cu and 63Sn37Pb were established based on creep law, and the stress-strain distribution of soldered joints in copper column grid array (CuCGA)devices was analyzed under the loadings of different temperature cycles. Results indicate that no matter how the change of temperature cycle range, the maximum creep strain is located in the soldered joint where the location from the device center is foremost, in which the stress concentration is found and cracks appear, therefore, the comer soldered joint is the most fragile area in the whole device.Creep strain of Sn3.9Ag0. 6Cu soldered joints is smaller than that of 63Sn37Pb soldered joints. Low er stress and creep strain are exhibited for both Sn3.9Ag0.6Cu and 63Sn37Pb when the temperature cycles range is shortened. Sn3.9Ag0.6Cu soldered joints show higher thermal fatigue life than 63Sn37Pb soldered joints under the same temperature cycle.     

A6N01-T5合金FSW和MIG焊接头疲劳裂纹扩展行为的对比

研究了6N01-T5铝合金搅拌摩擦焊(FSW)和氩弧焊(MIG)接头不同部位的疲劳裂纹扩展性能, 并对疲劳断口和接头组织进行了分析. 结果表明,对于FSW和MIG焊接头, 其裂纹扩展速率从高到低的部位依次为焊缝(核)区、热影响区和母材. 裂纹在FSW和MIG焊接头相同区域的扩展速率无明显差别, 然而裂纹在FSW接头细晶组织中开始扩展所需的门槛值ΔK要比对应的MIG焊接头高, 总体上其裂纹在FSW焊核区的抗疲劳裂纹扩展性能要优于对应的MIG焊缝区. 裂纹在FSW和MIG焊接头焊核(缝)区扩展的疲劳断口表现为脆性断裂, 而在热影响区则以规则和光滑的疲劳条纹形式扩展.     

QFP器件微焊点热疲劳行为分析

通过数值模拟可知,蠕变应变和塑性应变在时间历程处理过程中,以阶梯状累积增加.基于 Shine and Fox 模型和 Solomon 模型,运用等效应变进行 SnPb 和 SnAgCu 焊点的疲劳寿命评估,分别为 937 次和 1391 次.结果表明,焊点的拉伸力均随着热循环次数的增加而减小;SnAgCu 焊点的热循环可靠性优于 SnPb 焊点,焊点在热循环后的断裂形式已由韧性断裂转变为脆性断裂.随着热循环次数的增加,焊点界面处的金属间化合物层不断的生长,脆性的金属间化合物使得焊点的可靠性严重削弱,导致焊点的拉伸力下降.

Abstract：

The crrep strain and plastic strain of soldered joints in time history are studied and analyzed with numerical simulation method, which are found to be accumulated as ladder form.Based on Solomon and Shine and Fox models, the fatigue life values of the Sn-Pb and SnAgCu soldered joints are evaluated by equivalent strain, which are about 937 and 1 391 respectively. The experimental results showed both in experiment and simulation results indicate that the tensile force of soldered joints will be decreased with the increase of thermal cychng times, the reliability of SnAgCu after thermal cycling is better than that of Sn-Pb, the fracture mode of the soldered joints transforms from toughness fracture into brittle fracture,and the brittle intermetallic compounds at the interface of soldered joints will grow up gradually with the increase of thermal cycling times during thermal cycling process, which give a strong impact to the reliability of soldered joints and reduce the tensile force of soldered joints at the same time.