减少锡须

组建iNEMI锡须用户研究小组的目的就是为了把锡须引起的故障风险减至最小程度。本文回顾了该小组的推荐意见，它反映了现在可以获得的有关锡须形成和控制的最新资料．包括常用的无铅处理涂层的信息及其帮助减少锡须的效果。[编者按]     

Foreword Special Section on Tin Whiskers

The four papers in this special section focus on tin whiskers. Two of the four papers are based on presentations given at the Tin Whisker Workshop sponsored by the ECTC, iNEMI, and NIST on May 30, 2006. The papers are briefly summarized here.     

Crystallographic Texture and Whiskers in Electrodeposited Tin Films

Electron back scatter diffraction (EBSD) analysis was used to determine texture for electrodeposited tin films, and the results were compared to standard X-ray "times random" and full pole figure texture analysis. The data showed that EBSD and X-ray texture results differed as to primary and secondary texture determinations with some degree of correlation between texture determinations when primary/secondary/tertiary calculations were disregarded. It is these authors' opinion that film texture cannot be accurately determined using "times random" X-ray diffraction (XRD) techniques, and that there is considerable room for error with X-ray pole figure analyses. These data must be considered preliminary due to the small sample size, but these results indicate that electroplaters may have better control over as-deposited tin film texture than is currently believed, and that there is a relationship between as-deposited texture and film stress     

Analysis of the Effects of Tin Whiskers at High Frequencies

The initiative to remove lead from microelectronics packages has led to increased use of pure tin plating as the final finish on the leads of some parts. This finish can spontaneously grow whiskers on its surface. This paper presents results of a study by electromagnetic modeling into the possible effect of these whiskers on high-frequency signals. These results show that realistic configurations of whisker size and distribution will have only a very small effect on signal quality     

Mitigative Tin Whisker Growth Under Mechanically Applied Tensile Stress

Sn whisker/hillock growth is a result of the release of compressive stress in a Sn thin film. Filamentary Sn whiskers were formed on an electrodeposited Sn thin film aged at room temperature, while Sn hillocks were formed as the aging temperature was raised to 80°C and 150°C. By mechanically applying a tensile stress on the Sn thin film, the growth of the Sn whisker/hillock was significantly mitigated. This mitigation growth suggests that part of the compressive stress in the Sn thin film was neutralized by the mechanically applied tensile stress.     

Oxidation Behavior of Molten Tin Doped with Phosphorus

The oxidation process of molten tin in air at 280°C was studied. We found that a trace addition of phosphorus to the tin reduced the surface oxidation greatly by forming a protective film. The total thickness of the oxide film formed on the molten Sn-0.007wt.%P alloy was about 36 nm, which was composed of a layer of 6 nm SnO₂, 10–15 nm (Sn, P)O, and a transition layer. This oxide film was approximately a quarter of the thickness that formed on pure tin. The oxidized surfaces of different tin alloys were studied by scanning electronic microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). Much higher segregation of phosphorus was observed on the subsurface of the oxide film, and the concentration of phosphorus in the oxide film was about 500 times greater than that of the bulk concentration. Based on this result, the segregation of phosphorus on the molten surface could result in the formation of a new protective (Sn, P)O film on the subsurface of the molten tin. It is also suggested that the crystal structure of the oxide film should be studied in the future to confirm the mechanism.     

铟锡氧化程度对ITO薄膜光电特性的影响

采用直流磁控溅射法在普通载玻片上制备了氧化铟锡透明导电薄膜(ITO)。制备出的薄膜在大气环境下退火,退火温度分别为100℃、200℃和300℃,保温时间为1h。对薄膜中铟锡原子的氧化程度及其光电特性进行了测试与分析。结果表明:退火温度的升高,有助于提高ITO薄膜中Sn原子氧化程度,从而提高了薄膜在可见光范围内的透射率;退火温度为200℃时,In原子氧化程度较高,薄膜中氧空位数量最多,电阻率最低为6.2×10-3Ω.cm。     

含有限晶粒的微小接头的拉伸变形行为研究

采用了电子背散射衍射技术和在扫描电镜下原位拉神实验手段相结合的方法对Sn3．0Ag0．5Cu／Cu接头在拉力作用下的变形行为进行了研究。首先,利用电子背散射衍射技术分析了接头钎料表面的晶粒分布。其次,在原位拉伸实验中注意观察分析不同晶粒在拉伸过程中的变化。结果表明：试样接头钎料上晶粒个数有限。在拉力作用下,不同的晶粒中激活的滑移系不同,因而其塑性变形行为也不一样,这种不协调的塑性变形导致晶界处易产生裂纹。在变形过程中,钎料会出现动态回复,使晶粒碎化。某些碎化后的晶粒通过扭转使其晶体取向改变,新的取向使其变形变得更容易。这些晶粒会产生很大的塑性变形。     

Tensile and Fatigue Behavior of Al-1Si Wire Used in Wire Bonding

In this work, the mechanical properties of Al-1Si microelectronic wire were studied. The microstructure of the wire was examined to characterize the distribution of Al-Si inclusions and grain size. The wires had a diameter of 63.3 ± 0.1 μm and an elongated grain structure due to the hot extrusion process used to fabricate them. The transverse grain size was measured to be 1.1 ± 0.3 μm. The anisotropy in grain structure was characterized by dual-beam focused ion beam (FIB). The Young’s modulus was measured by conducting experiments at various gage lengths. The measured modulus was 71.7 ± 6.1 GPa, similar to that of bulk Al-Si. Strength data were measured for many wires, and the variability evaluated by Weibull statistics. The wires had a strength slightly less than 200 MPa and strain to failure of over 2%. A Weibull modulus of 110 was obtained, indicating very low variability in the data. Stress versus fatigue cycles was also conducted. Specimens that survived 10⁶ cycles exhibited a significant decrease in strength over the as-processed material. Fractographic analysis showed a significant amount of plastic flow and fracture by necking to a single point.     

Nonreciprocal Coupling with Single-Crystal Ferrites

A calculation of nonreciprocal coupling in microwave circuits with small ferrite samples tuned to ferromagnetic resonance is presented. It is shown that this coupling may be applied to the construction of simple resonant isolators, gyrators and circulators. Experimental results for the coupling in rectangular and ridge guides, applying YIG spheres, are presented. The construction of a simple X-band waveguide junction, acting as a 4-port resonant circulator, is described. Such a filter circulator, which may act as a switch or a frequency selective power divider, can be made tunable over the waveguide frequency range, with a bandwidth in the order of 10 Mc, and with values of insertion loss and isolation, which are comparable to those of conventional circulators.     

Microstructure Development of Mechanical-Deformation-Induced Sn Whiskers

The development of the microstructure of mechanical-deformation-induced Sn whiskers on electroplated films has been examined using a focused ion beam system (FIB). The 6-μm-thick matte Sn films were compressed by using a ZrO₂ ball indenter under ambient conditions. After compression, tin whiskers and small nodules were found adjacent to, and several grains further away from, the indents. The cross-sectional microstructures of the indents and whiskers indicate that the lateral boundaries of the newly created grains caused by recrystallization are the main routes for stress relaxation.     

VLS机制下SiC晶须的生长

采用化学气相沉积(CVD)法以气-液-固(VLS)机制生长了碳化硅(SiC)晶须,系统研究了基片表面的气流状况、生长温度和反应室总气压等对SiC晶须形貌的影响。研究结果表明:当基片表面存在较强的平流状态时,以生长SiC薄膜为主,很难形成晶须;生长温度及反应室总气压对晶须的直径有较大影响,合适的生长温度以及较高的总压有利于晶须的生长。     

锡涂覆层—SERA锡评价提供了对锡性能的深入理解

热风焊料整平(HASL)的技术、经济和环境因素迫使人们寻找其取代物。这些因素中包括新的元件如BGA、GOB和倒装芯片等的安装对PCB要求有更平整的连接盘,同时铅的特性也威胁着人类的健康。取代物的研究朝着两个方     

氮化硅晶须显微结构的研究

利用透射电子显微镜对气固相法制备的α－Ｓｉ＿３Ｎ＿４和β－Ｓｉ＿３Ｎ＿４晶须的显微结构进行了研究。实验发现α－Ｓｉ＿３Ｎ＿４晶须具有何（１０１０），（１０１１）和［０００１］三个生长方向，并且α－Ｓｉ＿３Ｎ＿４晶须中有大量的生长缺陷。而β－Ｓｉ＿３Ｎ＿４晶须的生长方向只有（１０１０）一个，且几乎观察不到任何缺陷。     

Temperature Dependence of the Conductivity of Tellurium Whiskers

Semiconductors - A comparative analysis of the electrical conductivity of whisker, epitaxial film, and single crystal of tellurium was undertaken in the 77–273 K temperature range. The...     

退锡废水中锡的分离实验研究

文章以碱中和退锡废水所得锡泥为原料,研究了碱浸法分离锡泥中的锡,在煮沸转化液固比为2,氢氧化钠与锡摩尔比为7～8,微沸(100℃～110℃)时间为2h,水洗液固比为5时,锡的分离率可以达到98%以上。     

元器件纯锡镀层表面晶须风险评估与对策

讨论了各种锡晶须的形态以及其长度的具体测量方法,并在试验研究的基础上进一步分析抑制非光滑(哑光)纯锡镀层上锡晶须生长的对策.研究结果表明,增加锡镀层厚度(＞7 μm),或通过使用添加剂来产生更加粗糙的表面以适当增大晶粒尺寸,电镀完成后及时进行退火程序是进一步减轻雾锡镀层上锡晶须困扰的有效手段.如果引入Ni作为中间镀层,则需要达到一定的厚度(估计＞0.7 μm),方可达到预期的效果.     

四针状氧化锌晶须吸波性能的改进

采用化学气相沉积的方法制备了铁包覆四角状氧化锌（T-ZnO）晶须的复合粉体。使用X射线衍射分析仪（XRD）进行了物相分析,用扫描电镜（SEM）观察了粉体的形貌,并运用能谱仪（EDS）进行了成分分析。结果表明,通过化学气相法进行表面包覆处理的晶须,外观形貌仍保持四针状结构,包覆层为单质铁。对复合粉体的电磁参数测试表明,改性晶须的磁性能明显增强,磁导率（μ’）在1．0～1．8之间,磁损耗（μ＂）在0．3～0．5之间;通过反射率曲线模拟发现,在8GHz点反射率可达-21dB,吸收频率的峰值向低频移动,这样有利于拓宽吸收频带。