Interfacial reactions in the pb-free composite solders with indium layers

A Pb-free composite solder is prepared with a Pb-free solder substrate and a plated-indium layer. The indium layer melts during the soldering process, wets the substrates, and forms a sound solder joint. Since the melting temperature of indium is 156.6°C, lower than that of the eutectic Sn-Pb, which is at 183°C, the soldering process can be carried out at a temperature lower than that of the conventional soldering process. Composite solder joints with three different Pb-free solders, Sn, Sn-3.5 wt.% Ag, and Sn-3.5 wt.% Ag-0.5 wt.% Cu, and two substrates, Ni and Cu, are prepared. The interfaces between the indium layer, Pb-free solder, and Ni and Cu substrate are examined. A good solder joint is formed after a 2-min reflow at 170°C. A very thick reaction zone at the indium/Pb-free solder interface and a thin reaction layer at the indium/substrate interface are observed.     

三相异步感应式电磁泵波峰焊机控制系统研究

介绍了一种利用微机实现的三相异步感应电磁泵单／双波峰焊机的控制系统,对波峰焊机的控制提出了一种新的控制方法及尝试。     

Effect of ultrasonic vibration time on the Cu/Sn-Ag-Cu/Cu joint soldered by low-power-high-frequency ultrasonic-assisted reflow soldering

Techniques to improve solder joint reliability have been the recent research focus in the electronic packaging industry. In this study, Cu/SAC305/Cu solder joints were fabricated using a low-power high-frequency ultrasonic-assisted reflow soldering approach where non-ultrasonic-treated samples were served as control sample. The effect of ultrasonic vibration (USV) time (within 6 s) on the solder joint properties was characterized systematically. Results showed that the solder matrix microstructure was refined at 1.5 s of USV, but coarsen when the USV time reached 3 s and above. The solder matrix hardness increased when the solder matrix was refined, but decreased when the solder matrix coarsened. The interfacial intermetallic compound (IMC) layer thickness was found to decrease with increasing USV time, except for the USV-treated sample with 1.5 s. This is attributed to the insufficient USV time during the reflow stage and consequently accelerated the Cu dissolution at the joint interface during the post-ultrasonic reflow stage. All the USV-treated samples possessed higher shear strength than the control sample due to the USV-induced-degassing effect. The shear strength of the USV-treated sample with 6 s was the lowest among the USV-treated samples due to the formation of plate-like Ag₃Sn that may act as the crack initiation site.     

0.5mm间距CSP/BGA器件无铅焊接工艺技术研究

芯片级封装器件因其小尺寸、低阻抗、低噪声等优点广泛应用于电子信息系统中.从器件封装、印制板焊盘设计、焊膏印刷、贴装以及回流焊接等方面探讨了0.5 mm间距CSP/BGA器件无铅焊接工艺技术.     

Interdiffusion analysis of the soldering reactions in Sn-3.5Ag/Cu couples

Extensive microstructural and kinetic studies on the formation and growth of the intermetallics of Sn-rich solder/Cu couples have been reported. However, experimental data on the interdiffusion mechanisms during soldering reactions are limited and in conflict. The interdiffusion processes for soldering of Sn-3.5Ag alloy/Cu couples were investigated by using the Cr-evaporated surface as a reference line. At the beginning of soldering, Cu was observed to outdiffuse to the molten Sn−3.5Ag alloy until saturation, and the Sn−Ag solder dissolved with Cu collapsed below the reference line. As a result, the scallop-shaped Cu₆Sn₅ intermetallic compound was formed at the newly-formed Sn−Ag−Cu solder/Cu interface below the original Cu surface. When the soldered joint was reflowed at the lower temperature to suppress the Cu dissolution, the Cu₆Sn₅/Cu interface moved into the Cu substrate. Therefore, Sn is the dominant diffusing species for the intermetallic formation during the soldering process, although the extensive Cu dissolution occurs at the early stage of soldering.     

感应式电磁泵波峰焊技术的发展及对环境保护

传统的波峰焊接设备技术,在使用锡铅钎料时将对环境造成明显的污染。感应式电磁泵波峰焊接设备技术,在抑制高温熔融状态下锡铅钎料氧化能力效果明显。重点分析单相交流感应式液态金属电磁泵波峰焊接设备技术的工作原理、技术特征;论述了其抑制钎料氧化技术机理。     

Fluxless wetting propeities of one-side-coated under bump metallurgy and top surface metallurgy

The wetting balance test was performed in an attempt to estimate the fluxless wetting properties of under bump metallurgy (UBM)-coated Si-wafer and top surface metallurgy (TSM)-coated glass substrate to SnPb solder. The wetting curves of the single-and double-side-coated UBM had a similar shape and the parameters characterizing the curve shape showed a similar tendency as a function of temperature. Wetting property estimation was possible with the new wettability indices from the wetting curves of one side-coated specimens; F_min, F_s, and t_s. Au/Cu/Cr UBM was better than Au/Ni/Ti UBM from the point of wetting time. For TSM, it was more effective to use Cu as a wetting layer with Au as a protection layer than to use Au as a wetting layer alone. The contact angle of one-side-coated Si-plate to SnPb solder can be calculated from the force balance equation by measuring static state force and tilt angle. The contact angles of Au/Cu/Cr and Au/Ni/Ti UBM of Si-wafer to SnPb solder were 59.9° and 63.9°, respectively. The contact angles of Au/Cu/Cr and Au/Cr TSM of glass to SnPb were 78.9 and 76.1°, respectively.     

基于加热因子的回流曲线的优化与控制

回流焊形成的焊点质量与回流焊过程密切相关。基于加热因子Qη对回流焊接过程进行优化控制。根据焊点疲劳寿命随加热因子分布的特点,提出了对冷点加热因子取最优范围下限值控制策略(冷点代表回流过程中经历的加热因子最小焊点),以使所有焊点的加热因子尽可能都在最优范围之内。冷点下限控制策略满足了大部分焊点的高可靠性,而少部分超出最优范围上限的焊点的可靠性虽略微下降,仍可形成良好焊接。由于加热因子理论不对回流曲线形状做严格要求,定义了两个组合参数:形状参数Ht和移动参数Hb,对冷点的加热因子进行控制。并且根据统计学原理利用实验建立Qη与Ht和Hb的回归关系,发现Qη与Ht、Qη与Hb大体上成线性关系,其为Qη的预测和控制带来了极大的便利,从而使焊接可靠性易于得到保证。     

焊膏厚度对CBGA组装板可靠性的影响

为了研究焊膏厚度对氮气保护再流焊CBGA组装板可靠性的影响 ,设计采用 0 .10mm、0 .15mm、0 .2 0mm三种厚度的焊膏和压缩空气与氮气保护再流焊来准备CBGA组装板可靠性试样。通过对组装板试样进行剪切强度、弯曲疲劳、热冲击和振动疲劳等可靠性试验来优化组装工艺过程。试验结果显示出 0 .15mm厚度的焊膏具有最佳的机械性能 ,氮气保护对改进组装板的性能起明显的作用。理论模型也定量给出了焊膏厚度与焊点性能之间的关系。     

无铅制程导入面临问题及解决方案

无铅化是国际电子整机业发展的必然趋势,无铅制程的导入给企业带来新的挑战与机遇。针对无铅化电子组装带来的问题给出了相应的解决方案,其中包括无铅化生产实施步骤、物料与设备的选择、工艺的制定、有毒有害物质的检测及运行成本等。