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61.
Cu-containing solder alloys have been used to identify their interfacial reactions with electroless NiP. As-reflowed, AuSn4 intermetallic compounds (IMCs) are formed in the Sn-Cu and Sn-Ag-Cu solders, but in the cases of Sn-Ag-Cu-In, In-Sn-Au IMCs
are formed and are uniformly distributed in the solder. Different types of IMCs such as high-Cu (>30 at.%), medium-Cu (30-15
at.%), and low-Cu (<15 at.%) containing IMCs are formed at the interface. High-Cu and medium-Cu containing ternary intermetallic
compounds (TIMCs) are found in the Sn-Cu and Sn-Ag-Cu solder joints, respectively. Medium-Cu containing quaternary intermetallic
compounds (QIMCs) are found in the Sn-Ag-Cu-In joints. Initially, TIMCs and QIMCs have higher growth rates, resulting in the
entrapment of some Pb-rich phase in the high-Cu containing TIMCs and some In-Sn-Au phase in the QIMCs. High-Cu containing
TIMCs have a lower growth rate and consume less of the NiP layer. The spalling of medium-Cu containing TIMCs in the Sn-Ag-Cu
solder increases both the growth rate of TIMCs and the consumption rate of the NiP layer. Low-Cu containing QIMCs in the Sn-Ag-Cu-In
solder are stable on P-rich Ni and reduce the dissolution rate of the NiP layer. Consumption of the NiP layer can be reduced
by adding Cu or In, because of the changes of the interfacial IMCs phases, which are stable and adhere well to the P-rich
Ni layer during reflow. 相似文献
63.
Recent Observations on Tin Pest Formation in Solder Alloys 总被引:1,自引:0,他引:1
W.J. Plumbridge 《Journal of Electronic Materials》2008,37(2):218-223
The most recent observations of the response of bulk samples of several lead-free solder alloys, exposed to temperatures below
the allotropic transition for tin for extended periods, are reported. Tin pest has been observed in Sn-0.5Cu, Sn-3.5Ag, Sn-3.8Ag-0.7Cu,
and Sn-3.0Ag-0.5Cu alloys at both −18°C and −40°C. The process is slow and inconsistent, usually requiring several years,
but may eventually result in complete disintegration of the sample. No tin pest was detected in Sn-Zn-3Bi or in the traditional
Sn-37Pb solder alloy after exposure for up to 4 and 10 years, respectively. It is suggested that nucleation is affected by
local composition and that extremely small amounts of either intentional solute or impurity are influential. Growth of tin
pest is accompanied by a large volume change, and it is likely that stress relaxation ahead of the expanding grey tin front
is a controlling factor. A stronger matrix would be more resistant in this case, and at the temperatures of exposure Sn-37Pb
is stronger than either Sn-3.5Ag or Sn-0.5Cu. The absence of tin pest, to date, on actual joints is attributed to their restricted
free surface area and the greater strength associated with very small samples. 相似文献
64.
随着LED显示屏控制技术和校正技术的发展,各厂家的显示效果优劣差距在进一步缩小,这个时候,显示屏外观结构件对其的影响就凸显起来,本文将从提高对比度、降低马赛克、增强耐候性三个方面来论述面罩、壳体的设计对LED显示屏在黑屏和亮屏时产生的不同影响。 相似文献
65.
文章通过对单器件的分立IGBT的封装结构进行分析,针对其结构特点和封装技术要求,特别是封装关键工艺芯片切割的影响,对装片、焊接方面进行工艺研究。并通过试验分析解决实际生产所出现的技术问题,由此形成一套适应于大批量封装生产的IGBT封装工艺技术,成功地应用于分立IGBT器件的批量生产,保证了产品的可靠性,取得了很好的生产效益。 相似文献
66.
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69.
We have studied two kinds of solder reactions between eutectic SnPb and Cu. The first is wetting reaction above the melting
point of the solder, and the second is solid state aging below the melting point of the solder. In wetting reaction, the intermetallic
compound (IMC) formation has a scallop-type morphology. There are channels between the scallops. In solid state aging, the
IMC formation has a layer-type morphology. There are no channels but grain boundaries between the IMC grains. Why scallops
are stable in wetting reactions has been an unanswered question of fundamental interest. We have confirmed that the scallop-type
morphology is stable in wetting reaction by re-wetting the layer-type IMC by molten eutectic SnPb solder. In less than 1 min,
a layer-type Cu6Sn5 is transformed back to scallops by the molten solder at 200 C. In analyzing these reactions, we conclude that the scallop-type
morphology is thermodynamically stable in wetting reaction, but the layer-type morphology is thermodynamically stable in solid
state aging, due to minimization of interfacial and grain boundary energies. 相似文献
70.