Cu基板表面镀镍浸金保护层对无铅焊点可靠性的影响

结合Sn-3.5Ag和Sn-3.0Ag-0.5Cu两种无铅钎料研究了镀镍浸金层(Electroless Nickel Immersion Gold,ENIG)表面层对焊点界面反应以及力学性能的影响。结果表明,钎焊后在Sn-3.5Ag/ENIG/Cu界面主要生成(Ni_yCu_(1-y))_3Sn_4,在Sn-3.0Ag-0.5Cu/ENIG/Cu界面主要生成(Cu_xNi_(1-x))_6Sn_5。在Sn基钎料/ENIG(Ni)/Cu界面处生成金属间化合物的种类及形貌由焊点中Cu原子含量决定。在时效过程中,ENIG表面层中Ni层有效抑制了焊点界面处金属间化合物的生长,减缓了焊点剪切性能的下降。在钎焊过程中ENIG表面层中的Au层不参与界面反应而是进入钎料基体与Sn反应,但是在时效过程中Au原子向界面迁移并造成焊点界面金属间化合物成分和焊点剪切强度的明显变化。     

Sn8Zn3Bi-xCu/Cu焊接接头界面反应及力学性能研究

以Sn8Zn3Bi为研究对象,采用微合金化方法研究了不同含量的Cu元素对其显微组织、钎料合金与Cu基板钎焊后的界面金属间化合物(IMC)层尺寸及焊接接头剪切强度的影响。结果表明,Sn8Zn3Bi-xCu/Cu(x=0.3,0.5,0.8,1.0,1.5)焊接界面IMC主要为层状Cu5Zn8相。随着Cu含量的增加,界面IMC层的厚度逐渐减小,接头的剪切强度逐渐提高,Sn8Zn3Bi-1.5Cu/Cu接头剪切强度较Sn8Zn3Bi/Cu显著提高。经120℃时效处理后,Sn8Zn3BixCu/Cu(x=0,0.3,0.5,0.8,1.0,1.5)焊接接头剪切强度都明显下降,接头断裂方式由韧性断裂转为局部脆性断裂,但添加了Cu元素的钎料界面IMC生长速度较Sn8Zn3Bi钎料慢,因此Cu元素的添加抑制了界面IMC层的生长。     

纳米Cr颗粒对Sn-Zn-Bi-In/Cu钎焊焊点性能的影响

通过向Sn-Zn-Bi-In钎料中添加不同含量的纳米Cr颗粒制成新型复合钎料Sn-5Zn-10Bi-10In-xCr(x=0％,0.1％,0.3％,0.5％,质量分数),探讨纳米C r颗粒对时效前后钎焊焊点的组织形貌、元素分布、物相组成和力学性能的影响.结果表明:纳米Cr颗粒的添加能够抑制焊点金属间化合物(IMCs)的生长,随着纳米Cr颗粒含量的增加,IMCs扩散层厚度逐渐降低;界面处IMCs扩散层靠近母材Cu一侧为Cu5 Zn8相,靠近钎料区一侧为Cu6 Sn5相;随时效时间的增加,钎料侧部分Cu5 Zn8化合物长大分解,Cu3 Sn相形成;纳米Cr颗粒抑制了时效过程中IMCs扩散层的进一步长大;随着纳米Cr颗粒含量的增加,焊接焊点的剪切强度和显微硬度均先增加后下降,Sn-5Zn-10Bi-10In-0.3Cr/Cu焊点的剪切强度和硬度最高;时效后焊件的剪切强度比时效前均有所下降,但纳米Cr颗粒的添加使焊点保持了良好的剪切强度,时效后焊点钎料区显微硬度比时效前有所上升,但也始终保持在30HV0.1以下.     

Sn-3.5Ag/Cu界面金属间化合物的生长行为研究

研究了Sn-3.5Ag无铅钎料和Cu基体在钎焊和时效过程中界面金属间化合物的形成和生长行为.结果表明,在钎焊过程中,由于钎料中存在着Cu的溶解度,界面处生成的金属间化合物存在着分解现象.因此Sn-3.5Ag/Cu界面金属间化合物层厚度与化合物层的分解有着密切关系.由于吸附作用,金属间化合物表面形成了纳米级的Ag3Sn颗粒.当钎焊接头在70,125,170℃时效时,钎焊时形成的扇贝状金属间化合物转变为层状.金属间化合物的生长厚度与时效时间的平方根呈线性关系,其生长受扩散机制控制.整个金属间化合物层和Cu6Sn5层的生长激活能分别为75.16 kJ/mol,58.59kJ/mol.     

热循环对SnAgCu(纳米Al)/Cu焊点界面与性能影响

研究了纳米0.1%(质量分数)Al颗粒对SnAgCu无铅钎料与铜基板之间界面反应的影响,研究两种无铅钎料界面在-55~125℃热循环过程中的生长行为及其焊点力学性能变化。结果表明:随着热循环次数的增加,界面层金属间化合物的厚度明显增加,焊后界面层金属间化合物为Cu6Sn5相,在热循环过程中在Cu6Sn5和Cu基板之间出现Cu3Sn相。发现纳米Al颗粒的添加,界面层金属间化合物的厚度明显减少,纳米颗粒对界面层的生长具有明显的抑制作用。同时对焊点在热循环过程中的可靠性进行分析,发现焊点的拉伸力随着循环次数的增加逐渐降低,含纳米Al颗粒的焊点具有明显的优越性,在焊点服役期间,焊点失效路径为Cu6Sn5/Cu3Sn的界面处。     

时效对无铅焊料Ni-P/Cu焊点的影响

研究了150℃等温时效为62Sn36Bp2Ag/Ni-P/Cu及共晶SnAg/Ni-P/Cu表面贴装焊点微结构及塑切强度的影响,结果表明,在钎料与Ni-P间的界面存在Ni3Sn4金属间化合物层,其厚度随时效时间增加,Ni-P层的厚度减小,时效后,SnPbAg,SnAg焊点的剪切强度下降,对于SnAg焊点,时效250h后其剪切强度剧烈下降,断裂发生在Ni-P/Cu界面上,在长时间时效后焊点一侧的Ni-P层中P的含量较主可能是Ni-P/Cu结合强度变差的主要原因,SnPbAg焊点保持着较高的剪切强度。     

SnAgCu-xBi/Cu焊点界面反应及微观组织演化

本工作在Sn-3.0Ag-0.5Cu焊料中添加不同含量的Bi(0.1%,0.5%,1.0%(质量分数)),以此来研究Bi含量对Sn-3.0Ag-0.5Cu/Cu焊点的界面反应及金属间化合物微观组织演化的影响。结果发现:回流反应之后,焊点界面形成扇贝状的Cu_6Sn_5,对焊点进行时效处理后发现,在Cu_6Sn_5层与Cu基板之间又出现了一层Cu_3Sn,并且Cu_6Sn_5层的上表面及焊料中出现了颗粒状的Ag_3Sn,Ag_3Sn颗粒的数量随着时效时间的延长而增多;5d的时效处理之后,在Cu基板的上表面和Cu_3Sn层中发现了柯肯达尔孔洞,同时在大多数焊点界面的Cu_6Sn_5层的上表面和Cu_6Sn_5层中出现了裂纹,推测裂纹是由于热膨胀系数差导致的残余应力而形成的。时效过程中,焊点界面金属间化合物(IMC)层的厚度不断增加,并且IMC的平均厚度与时效时间的平方根呈线性关系。对比未添加Bi元素的Sn-3.0Ag-0.5Cu/Cu焊点发现,添加微量的Bi元素对IMC层生长有抑制作用,当Bi含量为1.0%时,抑制作用最为明显,而Bi含量为0.5%时,抑制作用最弱。Cu_6Sn_5晶粒的平均直径随着时效时间的延长而增加,且Cu_6Sn_5晶粒的平均直径与时效时间的立方根呈线性关系。     

Cu/Sn37Pb/Cu钎焊接头界面微观结构及其剪切性能

本工作借助扫描电镜(SEM)等手段,针对Cu/Sn37Pb/Cu钎焊接头进行剪切断裂实验,考察并分析钎焊及等温时效处理后焊点接头金属间化合物(IMC)的生长情况以及搭接焊点的剪切强度和断裂模式,旨在深入研究高体积分数界面IMC层对钎焊接头剪切性能及断裂形貌的影响。实验结果表明:在时效处理过程中,界面Cu3Sn层逐渐增厚且逐渐变得平坦。此外,在Cu3Sn/Cu界面观察到柯肯达尔空洞现象,随着时效时间的延长,空洞数量增多且尺寸变大。随着界面IMC层厚度增加,接头的剪切强度先增加后下降,这可能是由于脆性IMC厚度过大或粗化的富Pb相和富Sn相增多引起的。当时效时间与钎焊时间较短时,焊点具有较高体积分数的本体焊料,焊点断裂模式为韧性断裂,随着时效时间或钎焊时间的延长,焊点内IMC体积分数逐渐升高,焊点断裂模式开始转变为韧脆混合断裂,最后转变为脆性断裂。     

Sn0.3Ag0.7Cu-xPr无铅钎料显微组织和力学性能研究

本文对Sn0.3Ag0.7Cu-x Pr钎料的显微组织和力学性能进行了试验研究。结果表明,微量稀土Pr的添加可以有效细化Sn0.3Ag0.7Cu钎料的显微组织和显著提高钎料的拉伸强度。Sn0.3Ag0.7Cu-0.1Pr钎料的基体组织得到最大程度的细化以及均匀化,金属间化合物颗粒尺寸明显减小,钎料的拉伸强度和延展性也达到了最大值,拉伸断口出现细小均匀的韧窝,呈明显的韧性断裂特征。当稀土Pr含量继续升高时,钎料的力学性能恶化,这与基体组织中出现的大块PrSn_3稀土相有关。     

液态Sn3.0Ag0.5Cu钎料与Cu、Fe及Co基板界面反应研究

研究了在固定温度380℃和不同钎焊时间条件下,液态Sn3.0Ag0.5Cu钎料与Cu、Fe、Co等3种金属基板的界面反应及其界面化合物(IMC)。研究结果表明,随着钎焊时间的增加,三者界面金属间化合物的平均厚度逐渐增加。Sn3.0Ag0.5Cu/Cu界面IMC主要由Cu_6Sn_5和Cu_3Sn组成,经过长时间钎焊后界面化合物大部分是Cu_3Sn。Sn3.0Ag0.5Cu/Fe界面化合物成分是FeSn2,相比另外两种界面,IMC在钎焊过程中生长最慢,形成的厚度最小。Sn3.0Ag0.5Cu/Co界面在短时间钎焊时(1min)会出现分层现象,认为是少量CoSn2和Sn原子在靠近钎料一侧反应生成CoSn3,靠近基板一侧生成CoSn2。长时间钎焊后观察到界面化合物只有CoSn3。通过对数据拟合可得到Sn3.0Ag0.5Cu/Cu、Fe、Co 3种液固反应界面的IMC层的生长率常数分别为9.55×10-6t 0.34,1.51×10~(-6)t~(0.18),0.85×10~(-6)t~(0.45)。比较3种基板,液态Sn基钎料与Cu基板的界面反应速率最快,IMC平均厚度也更厚。     

Cu Diffusion in Co/Cu/TiN Films for Cu Metallization

Some information on how to use in-situ determined diffusion coefficient of Cu to make barrier layer of Cu metallization in ultra large scale integrations （ULSIs） was provided. Diffusion coefficients of Cu in Co at low temperature were determined to analyze Cu migration to Co surface layer. The diffusion depths were analyzed using X-ray photoelectron spectroscopy （XPS） depth profile to investigate the diffusion effect of Cu in Co at different temperatures. The possible pretreatment temperature and time of barrier layer can be predicted according to the diffusion coefficients of Cu in Co.     

A Cu/ZnO Nanowire/Cu Resistive Switching Device

Nano-Micro Letters - A new device has been realized using flip-chip joining two printed circuit boards (PCBs) on which zinc oxide (ZnO) nanowires were synthesized. Energy dispersive X-ray...     

Optimization of Magneto-Optical Kerr Effect in Cu/Fe/Cu Nano-structure

We use an analytical approach to describe the optical response of a magnetoplasmonic structure upon surface plasmon polariton (SPP) excitation in glass/Cu/Fe/Cu multilayer. The proposed structure is based on Kretschmann prism couplers, Fe layer as magneto-optical (MO) medium, and Cu layer as plasmonic metal layer, to enhance the MO effects thanks to the resonant excitation of surface plasmons. The influence of constituent layer thicknesses and layer order is investigated to obtain the maximum MO Kerr signal and figure of merit (FOM) in polar geometry. In addition, we show a range of parameters to determine the maximum Kerr rotation accompanied by minimum Kerr ellipticity which is desirable for data storage applications. Results demonstrate the important role of film thicknesses and incidence angle distribution on resonant excitation of surface plasmons.     

Interdiffusion phenomena in Au/Cu and Cu/Au bilayers

The microstructures of epitaxial deposits of (111) Cu/(111) Au and (111) Au/(111) Cu at various stages of interdiffusion are described. The most prominent microstructural features of Au/Cu films (where gold deposition occurred at temperatures less than 400 °C) were (Matthews) coincidence lattice misfit dislocations lying along < 1$\text{1}$0 > directions in the film plane with $\text{|b| =}\text{a}\text{2}\text{< 110 >}$ directed out of the film plane. Their spacings, transmission electron microscopy (TEM) hot stage behavior and generation mechanisms are discussed. For more severe diffusion anneals, the coincidence dislocation density decreased and hexagonal networks identified as ( van der Merwe) natural lattice misfit dislocations became resolvable. They are edge type (lying along <11$\text{2}$> directions in the film plane) with $\text{|b| =}\text{a}\text{2}\text{< 1}\text{1}\text{0 >}$. For the case of Cu/(111) Au bilayers, copper deposited at and below 315 °C with a 20 min anneal again showed coincidence misfit networks. Higher temperature deposition of copper (or hot stage annealing) resulted in natural lattice misfit dislocations in the microstructure. The densities of both types of dislocations were determined and their TEM hot stage behavior was investigated. The method by which the two networks contribute to the relief of misfit strain in both bilayers is discussed.     

Ceramic joining III bonding of alumina via Cu/Nb/Cu interlayers

A method of ceramic-ceramic joining that exploits a multilayer interlayer designed to form a thin, potentially transient layer of liquid phase has been used to join alumina to alumina. Microdesigned multilayer Cu/Nb interlayers were used to achieve bonding at 1150 °C. Flexure strengths of as-bonded samples ranged from 119 to 255 MPa, with an average of 181 MPa. The ability to form strong ceramic/metal interfaces is also indicated by instances of ceramic failure. Microstructural and chemical characteristics of fracture surfaces were evaluated using SEM, EDS and microprobe. The impact of post-bonding anneals of 10 h duration at 1000 °C in gettered argon on room-temperature joint strength was assessed. High strengths (198 to 238 MPa) were obtained. The retention of strength following annealing in low oxygen partial pressure argon differs from the behaviour previously observed in Cu/Pt bonded alumina. Effects of the anneal on interfacial microstructure were determined, and an explanation for this difference in behaviour is proposed.     

Cu surface segregation in Ni/Cu system

We report experimental evidence of Cu surface segregation in Ni/Cu system, during deposition of Ni film onto Cu substrate at room temperature and during heat treatment in vacuum. Auger electron spectroscopy (AES) and X-ray photoelectron spectroscopy (XPS) by Tougaard's analysis results show that surface segregation defeats in competition with increase in Ni thickness and terminates when thickness of Ni increase to more than 4 nm. Surface energy and concentration were calculated using contact angle measurements and the results confirm that segregation reduces the surface energy. Surface segregation during heat treatment at 150-220 °C range as a function of time initially shows linear mass transfer. By solving Fick's equation and taking empirical diffusion coefficient, 125 ± 20 kJ/mol is obtained for activation enthalpy of effective diffusion.     

Cr/Cu/Ag/Cu/Cr新型银基复合薄膜电极的防氧化性能研究

采用直流磁控溅射技术和光刻工艺制备了Cr/Cu/Ag/Cu/Cr复合薄膜及其电极,研究不同温度热处理对复合薄膜和电极结构、表面形貌和电性能的影响。Ag层与最外层的Cr层之间的Cu层不仅增强了Cr和Ag之间的粘附力,而且起到了牺牲层和氧气阻挡层的作用;Cr和Cu对Ag的双重保护使得薄膜电极在温度小于500℃时电阻率保持较为稳定,约为3.0×10-8~4.2×10-8Ω·m之间。然而由于电极表面氧化和边沿氧化的共同作用,薄膜电极的电阻率在热处理温度超过575℃出现了显著的上升。尽管如此,Cr/Cu/Ag/Cu/Cr薄膜电极仍然是一种能够承受高温热处理并且保持较低电阻率的新型电极,满足场发射平板显示器封接过程中的热处理要求。