共查询到20条相似文献,搜索用时 93 毫秒
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本文给出了倒装焊(flip-chip)焊点形态的能量控制方程,采用Surface Evolver软件模拟了倒装焊复合SnPb焊点(高Pb焊料凸点,共晶SnPb焊料焊点)的三维形态.利用焊点形态模拟的数据,分析了芯片和基板之间SnPb焊点的高度与焊点设计和焊接工艺参数的关系.研究表明:共晶SnPb焊料量存在临界值,当共晶SnPb焊料量小于临界值时,焊点的高度等于芯片上高Pb焊料凸点的半径值;当共晶SnPb焊料量大于临界值时,焊点的高度随共晶SnPb焊料量的增加而增加.另外,采用无量纲的形式给出了焊点高度与共晶焊料量、焊盘尺寸、芯片凸点的尺寸,芯片重量之间的关系模型,研究结果对倒装焊焊点形态的控制、工艺参数的优化和提高焊点可靠性具有指导意义. 相似文献
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模板开口的尺寸和厚度决定应用于PCB板上焊膏的量,从而决定了回流焊后生成的焊点形态。本文根据IPC-7525模板设计理论,拟定多组开口方案,设计了16组模板结构参数,并通过软件Surface Evolver输入数据文件,得到16组倒装焊焊点形态,用有限元软件进行焊点寿命分析,得到了模板结构参数与热疲劳寿命的关系,探讨不同的开口尺寸和厚度对焊点形态的影响。 相似文献
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本文通过用于焊点形态预测软件SURFACE EVOLVER的输入数据文件,得到倒装焊焊点形态.参考模板开口指导说明(IPC-7525),拟定模板开口方案,得到相应的焊点形态.通过建立有限元模型,运用ANSYS软件对含铅焊点在热循环加载条件下的应力应变和疲劳寿命进行分析.根据预测得到的热疲劳寿命,找出了适合本文模型的模板结构参数,同时分析了其它设计与工艺参数和焊点可靠性之间的关系. 相似文献
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在从含铅制程到无铅制程的转换过程中会遇到四种不同的焊点冶金组合:无铅焊料和无铅元件;无铅焊料和含铅元件;锡铅焊料和无铅元件;锡铅焊料和含铅元件。为了更好的优化工艺参数并获得高可靠性的焊点,我们必须研究上述不同冶金组合焊点的冶金过程和组织特性。本研究工作中,Sn-3.8Ag-0.7Cu、Sn-37Pb两种BGA焊球和Sn-3.8Ag-0.7Cu、Sn-37Pb两种锡膏分别组合焊接在表面无电解镀镍/浸金(Ni/Au)的试验板上,得到四种不同冶金组合的焊点。部分制成的试验板叉分别经过150℃310小时、480小时、2160d小时的老化。对上述焊点分别进行剪切力测试并使用X-射线透视.仪、光学显微镜、扫描电子显微镜、散射X-射线光谱仪等试验设备对焊点进行检测。对部分未经过老化的焊点用差示扫描量热法进行了分析。我们着重对四种不同冶金组合的焊点的微观结构及组织构成、金属间化合物构成、表面粗糙度以及焊点空洞问题进行了研究,并对四种不同冶金组合的焊点的相似处和不同处进行了讨论。研究揭示了焊点微观组织结构对焊点剪切强度和断裂模式的影响。 相似文献
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对板上倒装芯片底充胶进行吸湿实验,并结合有限元分析软件研究了底充胶在湿敏感元件实验标准MSL—1条件下吸湿和热循环阶段的解吸附过程,测定了湿热环境对Sn3.8Ag0.7Cu焊料焊点可靠性的影响,并用蠕变变形预测了无铅焊点的疲劳寿命。结果表明:在湿热环境下,底充胶材料内部残留的湿气提高了焊点的应力水平。当分别采用累积蠕变应变和累积蠕变应变能量密度寿命预测模型时,无铅焊点的寿命只有1740和1866次循环周期。 相似文献
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Sang-Su Ha Jong-Woong Kim Jeong-Won Yoon Sang-Ok Ha Seung-Boo Jung 《Journal of Electronic Materials》2009,38(1):70-77
The electromigration of conventional Sn-37Pb and Pb-free Sn-3.0Ag-0.5Cu (in wt.%) solder bumps was investigated with a high
current density of 2.5 × 104 A/cm2 at 423 K using flip-chip specimens comprised of an upper Si chip and a lower bismaleimide triazine (BT) substrate. Electromigration
failure of the Sn-37Pb and Sn-3.0Ag-0.5Cu solder bumps occurred with complete consumption of electroless Ni immersion Au (ENIG)
underbump metallization (UBM) and void formation at the cathode side of the solder bump. Finite element analysis and computational
simulations indicated high current crowding of electrons in the patterned Cu on the Si chip side, whereas the solder bumps
and Cu line of the BT substrate had a relatively low density of flowing electrons. These findings were confirmed by the experimental
results. The electromigration reliability of the Sn-3.0Ag-0.5Cu solder joint was superior to that of Sn-37Pb. 相似文献
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In flip-chip solder joints, thick Cu and Ni films have been used as under bump metallization (UBM) for Pb-free solders. In
addition, electromigration has become a crucial reliability concern for fine-pitch flip-chip solder joints. In this paper,
the three-dimensional (3-D) finite element method was employed to simulate the current-density and temperature distributions
for the eutectic SnPb solder joints with 5-μm Cu, 10-μm Cu, 25-μm Cu, and 25-μm Ni UBMs. It was found that the thicker the UBM is the lower the maximum current density inside the solder. The maximum current
density is 4.37 × 104 A/cm2, 1.69 × 104 A/cm2, 7.54 × 103 A/cm2, and 1.34 × 104 A/cm2, respectively, when the solder joints with the above four UBMs are stressed by 0.567 A. The solder joints with thick UBMs
can effectively relieve the current crowding effect inside the solder. In addition, the joint with the thicker Cu UBM has
a lower Joule heating effect in the solder. The joint with the 25-μm Ni UBM has the highest Joule heating effect among the four models. 相似文献
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The Cu pillar is a thick underbump metallurgy (UBM) structure developed to alleviate current crowding in a flip-chip solder
joint under operating conditions. We present in this work an examination of the electromigration reliability and morphologies
of Cu pillar flip-chip solder joints formed by joining Ti/Cu/Ni UBM with largely elongated ∼62 μm Cu onto Cu substrate pad metallization using the Sn-3Ag-0.5Cu solder alloy. Three test conditions that controlled average
current densities in solder joints and ambient temperatures were considered: 10 kA/cm2 at 150°C, 10 kA/cm2 at 160°C, and 15 kA/cm2 at 125°C. Electromigration reliability of this particular solder joint turns out to be greatly enhanced compared to a conventional
solder joint with a thin-film-stack UBM. Cross-sectional examinations of solder joints upon failure indicate that cracks formed
in (Cu,Ni)6Sn5 or Cu6Sn5 intermetallic compounds (IMCs) near the cathode side of the solder joint. Moreover, the ~52-μm-thick Sn-Ag-Cu solder after long-term current stressing has turned into a combination of ~80% Cu-Ni-Sn IMC and ~20% Sn-rich
phases, which appeared in the form of large aggregates that in general were distributed on the cathode side of the solder
joint. 相似文献
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采用Cu-Ni/Solder/Ni-Cu互连结构,在加载的电流密度为0.4×104 A/cm2的条件下,得到了界面阴极处金属原子的电迁移.数值模拟揭示了其原因是由于凸点互连结构的特殊性,电子流在流经凸点时会发生流向改变进而形成电流聚集,此处的电流密度超过电迁移的门槛值,从而诱发电迁移.运用高对流系数的热传导方法降低了互连焊点的实际温度,在电迁移的扩展阶段显著减小了高温引起的原子热迁移对电迁移的干扰;因此电迁移力是原子迁移的主要驱动力.在电迁移的快速失效阶段,原子的迁移是热迁移和电迁移共同作用的结果:电迁移力驱动阴极处原子的迁移,造成局部区域的快速温升,从而加剧此处原子的热迁移. 相似文献
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采用Cu-Ni/Solder/Ni-Cu互连结构,在加载的电流密度为0.4×104 A/cm2的条件下,得到了界面阴极处金属原子的电迁移.数值模拟揭示了其原因是由于凸点互连结构的特殊性,电子流在流经凸点时会发生流向改变进而形成电流聚集,此处的电流密度超过电迁移的门槛值,从而诱发电迁移.运用高对流系数的热传导方法降低了互连焊点的实际温度,在电迁移的扩展阶段显著减小了高温引起的原子热迁移对电迁移的干扰;因此电迁移力是原子迁移的主要驱动力.在电迁移的快速失效阶段,原子的迁移是热迁移和电迁移共同作用的结果:电迁移力驱动阴极处原子的迁移,造成局部区域的快速温升,从而加剧此处原子的热迁移. 相似文献
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Flip-chip solder joints with Cu/Ni/Al underbump metallurgy (UBM) on the chip and an Au/Ni surface finish on the substrate
were studied under current stressing at an ambient temperature of 150°C. Three different Ni thicknesses in the Cu/Ni/Al UBM
(0.3, 0.5, and 0.8 μm) were used in order to investigate the effect of the Ni thickness on reliability. The solder used was eutectic Pb-Sn, and
the applied current density was 5 × 103 A/cm2. The results show that the combined effect of current crowding and the local Joule heating near the entry points of electrons
into the joints induced asymmetric Ni UBM consumption. Once the Ni was exhausted in a certain region, this region became nonconductive
and the flow of electrons was diverted to the neighboring region. This neighboring region then became the place where electrons
entered the joint, and the Ni UBM there was consumed at an accelerated rate. This process repeated itself, and the Ni-depleted
region continued to extend, creating an ever larger nonconductive region. The solder joints eventually failed when the nonconductive
region extended across the entire contact window of the joints. This failure model supports the observation that joints with
a thicker Ni tend to have a longer average lifetime. 相似文献
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In flip-chip interconnects under current stressing, the primary current crowding effect occurs at the entrance edge of the
contact interface with the highest current density. In this study, an increased current density also occurred at the other
edge of the contact interface, followed by a selective dissolution of under bump metallization. After primary current crowding,
the rest of electrons flow to the metallization edge, followed by an abrupt change in direction toward the anode. Primary
current crowding is attributed to the electrical field change whereas the secondary crowding effect is due to the physical
blocking of the electron flow. Because this effect is not as great as that of primary current crowding, it must be assisted
by thermal diffusion. 相似文献
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Aditya Kumar Ying Yang Chee C. Wong Vaidhyanathan Kripesh Zhong Chen 《Journal of Electronic Materials》2009,38(1):78-87
The effect of moderate electric current density (1 × 103 to 3 × 103 A/cm2) on the mechanical properties of Ni-P/Sn-3.5Ag/Ni-P and Ni/Sn-3.5Ag/Ni solder joints was investigated using a microtensile
test. Thermal aging was carried out at 160°C for 100 h while the current was passed. The interfacial microstructure and intermetallic
compound (IMC) growth were analyzed. It was found that, at these levels of current density, there were no observable voids
or hillocks. Samples aged at 160°C without current stressing failed mostly inside the bulk solder with significant prior plastic
deformation. The passage of current was found to cause brittle failure of the solder joints and this tendency for brittle
failure increased with increasing current density. Fractographic analysis showed that, in most of the electrically stressed
samples, fracture occurred at the interface region between the solder and the joining metals. The critical current density
that caused brittle fracture was about 2 × 103 A/cm2. Once brittle fracture occurred, the tensile toughness, defined as the energy per unit fractured area, was usually lower
than ~5 kJ/m2, compared with the case of ductile fracture where this value was typically greater than ~9 kJ/m2. When comparing the two types of joint, the brittle failure was found to be more severe with the Ni than with the Ni-P joint.
This work also found that the passage of electric current affects the IMC growth rate more significantly in the Ni than in
the Ni-P joint. In the case of the Ni joint, the Ni3Sn4 IMC at the anode side was appreciably thicker than that formed at the cathode side. However, in the case of electroless Ni-P
metallization, this difference was much smaller. 相似文献