高强度耐候钢Q355对接接头多次焊修力学行为研究

通过焊接工艺评定试验以及疲劳试验,分析高强度耐候钢Q355GNHD正常对接接头和3次焊修接头的显微组织、常规力学性能以及疲劳结果差异。结果表明:3次焊修接头熔合良好,显微组织未见马氏体;3次焊修焊接接头和正常焊接接头的拉伸、弯曲及硬度等常规力学性能未见明显差异;3次焊修接头过热区组织粗大,冲击功有所降低,但均满足标准规定的焊接接头技术条件;两种焊接接头的疲劳性能相近,符合设计要求。     

CCGA封装特性及其在航天产品中的应用

介绍了CCGA封装的基本组成及焊柱的3种连接技术,对CCGA如何实现高互联密度、高性能、高可靠性的大尺寸封装进行了详细描述。CCGA板级装配的热循环试验结果表明CCGA封装技术达到甚至超过了典型卫星对航天电子设备可靠性的要求;CCGA散热时施加在器件顶部的压力超过极限值后将对可靠性产生严重影响。板级装配设计的关键要素和板级组装的关键工艺在文中也进行了概括性的叙述。     

热疲劳载荷作用下不同成分BGA焊点可靠性

针对微电子组装中常见的BGA封装形式,对比采用3种不同成分的BGA焊球和焊膏组合(锡铅共晶焊球和锡铅共晶焊膏Sn63Pb37、Sn3Ag0.5Cu焊球和锡铅共晶焊膏以及Sn3Ag0.5Cu焊球和Sn3Ag0.5Cu焊膏)焊接得到的BGA焊接界面。经过不同周期的热疲劳试验后,在金相显微镜和电子背散射衍射下观察,发现Sn3Ag0.5Cu焊球和锡铅共晶焊膏混装形成的BGA焊点中黑色的富锡相均匀弥散分布在焊球内,在热循环载荷作用下极难形成再结晶,抗热疲劳性能最好。     

Thermomechanical Stress and Strain in Solder Joints During Electromigration

Thermomechanical stress and strain in the solder joints of a dummy area array package were studied as electromigration occurred. A current density of 0.4 × 10⁴ A/cm² was applied to this package, constructed with 9 × 9 solder joints in a daisy chain, to perform the electromigration test. After 37 h, the first joint on the path of the electron flow broke off at the cathode, and the first three solder joints all exhibited a typical accumulation of intermetallic compounds at the anode. Different solder joints exhibited dissimilar electromigration states, such as steady state and nonsteady state. Finite element analysis indicated that during steady-state electromigration, although the symmetrical structure produced uniform distributions of current density and Joule heating in all solder joints, the distribution of temperature was nonuniform. This was due to the imbalanced heat dissipation, which in turn affected the distribution of thermomechanical stress and strain in the solder joints. The maximum thermomechanical stress and strain, as well the highest temperature and current crowding, appeared in the Ni/Cu layer of each joint. The strain in the Ni/Cu layer was significant along the z-axis, but was constrained in the x–y plane. The thermomechanical stress and strain increased with advancing electromigration; thus, a potential delamination between the Ni/Cu layer and the printed circuit board could occur.     

Effect of silver content on thermal fatigue life of Sn-xAg-0.5Cu flip-chip interconnects

The thermal fatigue properties of Sn-xAg-0.5Cu (x=1, 2, 3, and 4 in mass%) flip-chip interconnects were investigated to study the effect of silver content on thermal fatigue endurance. The solder joints with lower silver context (x=1 and 2) had a greater failure rate compared to those with higher silver content (x=3 and 4) in thermal fatigue testing. Cracks developed in the solders near the solder/chip interface for all joints tested. This crack propagation may be mainly governed by the nature of the solders themselves because the strain-concentrated area was similar for tested alloys independent of the silver content. From the microstructural observation, the fracture was a mixed mode, transgranular and intergranular, independent of the silver content. Higher silver content alloys (x=3 and 4) had finer Sn grains before thermal cycling according to the dispersion of the Ag₃Sn intermetallic compound, and even after the cycling, they suppressed microstructural coarsening, which degrades the fatigue resistance. The fatigue endurance of the solder joints was strongly correlated to the silver content, and solder joints with higher silver content had better fatigue resistance.     

等温时效对SnSb4.5CuNi/Cu焊接接头力学性能的影响

SnSb4.5CuNi/Cu焊点在175℃进行等温时效,分析了不同时效时间的SnSb4.5CuNi/Cu焊点中金属间化合物(IMC)组织形貌演变,通过纳米压痕法测量SnSb4.5CuNi/Cu焊点界面IMC的硬度和弹性模量,对焊接接头进行拉伸强度和低周疲劳测试。结果表明,时效48 h的焊缝中Cu6Sn5呈曲率半径均匀的半圆扇贝状特征,IMC的弹性模量与铜基板很接近,在恒幅对称应变条件下焊点的抗低周疲劳的性能最佳,焊点的抗拉强度高;当时效时间大于48 h,焊接接口的抗疲劳性能和抗拉伸强度逐渐变差。     

拉丝环境湿度对高强度光纤动态疲劳的影响

文章研究了高强度石英玻璃光纤的动态疲劳性能与拉丝环境相对湿度的函数关系。光纤是在采用石墨感应加热炉加热,并在控制温度、相对湿度和拉丝环境尘埃粒子数的条件下拉制的。所谓拉丝环境指的是从感应加热拉丝炉至涂覆点之间的空间。通常,人们采用两种不同的加载方式,即拉伸和两点弯曲来测量拉制的光纤的动态疲劳。业已发现,拉丝湿度对用张力法加载方式测得的光纤的动态疲劳起着决定性的影响。     

钢板厚度及混凝土强度对粘钢补强梁疲劳性能的影响

本文通过钢筋混凝土芯梁及粘贴钢板补强混凝土复合梁的疲劳试验，研究了它们在疲劳试验过程中载荷和加载线位移及跨中挠度的变化规律。同时，还探讨了混凝土强度、补强钢板厚度等因素对粘钢补强梁的疲劳性能影响。     

激光喷丸强化ZK60变形镁合金的疲劳性能研究

为研究激光喷丸对高强度变形镁合金ZK60疲劳性能的影响机理,使之适应交变应力结构件的工作需要,进行了激光喷丸强化表面改性和拉伸疲劳性能实验。实验结果表明,在激光喷丸强化区域获得有益的残余压应力,产生硬化效应,表面塑性变形的微小区域,变形轮廓曲线波动范围较基体小,增加喷丸次数可增强激光喷丸的强化效应。经3次激光喷丸后,中心孔疲劳试样的平均疲劳寿命由未喷丸试样的78023次提高到125641次,寿命增益达61%。从断口来看,激光喷丸强化主要是改变了裂纹源萌生位置,延缓了裂纹扩展速率,对瞬断区无明显影响。激光喷丸强化为镁合金的抗疲劳制造提供了新的途径。     

电路板嵌入元器件有机模块技术的开发

为了提高电子组装密度,基板嵌入元器件的三维安装模式受到人们更多的关注.介绍了一种以铜芯为基板核心材料的元器件嵌入技术(EOMIN),详细叙述了其外形结构和制造工艺,并通过实验与FR-4基板嵌入元器件和低温共烧陶瓷基板(LTCC)安装元器件进行比较,通过实验数据对比得出EOMIN元器件嵌入技术具有导热性能好,抗疲劳性强,承受热冲击时铜的塑性变形量小,连接可靠性高等优良特性的结论.