贵金属微异型复合丝材

阐述断面〈１ｍｍ＾２的贵金属微异型复合材料的特点功能及用途，并介绍昆明贵金属研究所用室温固相复合和滚焊复合法制作的Ａｕ／Ｃｕ、Ａｕ／Ａｇ－５００Ｐｂ、Ａｇ／Ｎｉ等微异型复合丝的性能和试验结果。     

键合界面金属间化合物对可靠性影响的研究现状

在微电子封装过程中,键合丝被广泛应用,而键合可靠性对于产品的应用性能有着极大的影响,受到人们的广泛关注。键合丝与常用的铝焊盘之间是异质材料,在应用和服役的过程中会在界面上产生金属间化合物(IMC),对器件可靠性产生影响,同时,键合强度也与键合丝和焊盘之间的界面反应联系密切,因此了解键合丝与铝焊盘之间金属间化合物的形成与演变对键合可靠性的影响是有必要的。本文综述了Au/Al、Ag/Al和Cu/Al三种键合界面上金属间化合物的形成与演变的研究现状,并根据目前的应用状况,展望了未来的应用发展前景。     

变形量对Ag-20Cu形变宏观复合材料力学性能的影响

采用包覆-挤压-拉拔法制备了Ag-20Cu(质量分数,下同)形变宏观复合材料丝材.测试了不同变形量下Ag-20Cu复合丝材的极限抗拉强度、各相的显微硬度,扫描电镜测量了各相的尺寸,研究了变形过程中Ag-20Cu复合丝材力学性能的变化规律.结果表明,由于形变引起复合材料内部各相发生不同程度的加工硬化和回复,复合材料的力学性能随变形量的增加表现出不同的变化趋势,低应变阶段,由于各相的加工硬化和位错在复合界面处塞积,其力学性能随变形量的增大而增大;高应变阶段,主要由于基体Ag相的回复效应,其力学性能随变形量的增加而减小.     

Intermetallic growth in gold ball bonds aged at 175°C: comparison between two 4N wires of different chemistry

Gold wires of different chemistry (denoted as Types A and B) are ballbonded on identical metallization and isothermally aged at 175°C. In both wire types the same intermetallic compounds Au₄Al and Au₈Al₃ grow with parabolic time dependence as long as there is a supply of Al from the bondpad. After Al is completely reacted, composition of intermetallics in Type A wire remains unchanged but in Type B wire, the Au₈Al₃ compound undergoes a phase transformation into a second layer of Au Al. The phase transformation does not affect mechanical reliability of the ballbonds. Intermetallic growth kinetics, growth sequence and the possible origins of the phase transformation are discussed.     

Corrosion behaviour and biocompatibility of a new dental noble AuPdAgTi alloy

The aims of the study were to investigate the electrochemical response of a new dental Au‐20Pd‐10Ag‐5Ti alloy in artificial Carter‐Brugirard saliva and to assess its biocompatibility using gingival fibroblast culture. Electrochemical techniques of potentiodynamic and linear polarization were used. Also, the open circuit potentials and the corresponding open circuit potential gradients were monitored for 5000 exposure hours. The gingival fibroblast response to Au‐20Pd‐10Ag‐5Ti alloy was estimated by LDH‐cytotoxicity, MTT cell proliferation assays, the assessment of substrate‐dependent changes in extracellular fibronectin network, cell morphology and actin cytoskeleton organization. The cyclic potentiodynamic curves of Au‐20Pd‐10Ag‐5Ti alloy exhibited a passive behaviour with transpassive dissolution of silver, without pitting corrosion. Open circuit potentials were finally stable at noble values. Open circuit potential gradients have low values that could not generate galvanic or local corrosion. The new Au‐20Pd‐10Ag‐5Ti alloy did not promote cell damage and alterations in cell adhesion and morphological features, exhibiting a good biocompatibility.     

大塑性变形Ag-20Cu复合丝材各相变形特征

采用包覆法制备了Ag-20Cu(体积分数,%,下同)复合材料初始锭坯,热挤压成复合线材,再通过冷拉拔大变形制得Ag-20Cu复合丝。分别测量了不同真应变η下复合丝材的力学性能;通过扫描电镜测量不同真应变η下Ag和Cu两相尺寸变化,观察了其断裂形貌。通过上述实验研究了变形过程中Ag-20Cu复合材料的各相变形特征。研究结果表明:变形过程中,由于复合材料各组成相的力学性能不同,Ag和Cu两相发生协调变形,且不同变形阶段两相的协调变形方式不同;由于各相在变形过程中存在不同程度的加工硬化和回复,不同的变形阶段,复合材料的性能变化趋势不同,各相对复合材料性能的影响也不相同。     

Electrochemical study on effect of Au,Ag, Pd and Pt on corrosion behaviour of Fe3Al in molten NaCl–KCl

The corrosion behaviour of Fe₃Al intermetallic alloyed with 1 at-%Ag, Au, Pt and Pd in NaCl–KCl (1∶1M) at 700°C, typical of waste gasification environments, has been evaluated using polarisation curves, linear polarisation resistance and electrochemical impedance spectroscopy measurements and compared with an Ni based alloy, namely Inconel 600. Results have shown that, for short testing times, the addition of noble elements increased the corrosion rate for base Fe₃Al intermetallic alloy, but it was decreased for long testing times by forming a protective corrosion product layer. Additionally, base Fe₃Al intermetallic alloy had higher corrosion rates than Inconel 600.     

New Sorption Materials Based on Organosilicon Derivatives of Thiosemicarbazides

The synthesis of organosilicon derivative monomers and polymers characterized with sorption properties has been performed. The synthesized organosilicon polymers have been investigated as sorbents for heavy (Hg(II)) and noble (Ag(I), Au(III), Rh(II), Pd(II), and Pt(IV)) metals. The coefficients of the interphase metal distribution have been estimated.     

Laser brazing of alloy 600 with precious filler metals

Abstract

The diode laser brazing of Ni base heat resistant alloy with precious filler metals has been conducted using the tandem beam for preheating and brazing. A couple of 1 mm thick plates of alloy 600 (Inconel 600) were butt brazed using Au–18Ni, Ag–10Pd and Ag–21Cu–25Pd filler metals of 0·5 mm diameter with a brazing flux. Sound butt joints which were free from brazing defects such as porosity and lack of penetration could be obtained at brazing clearances of 0·1–1·5 mm. The tensile strength of the braze joint produced using Ag–Pd filler metal increased with decreasing brazing clearance and reached ～70% of the base metal strength at a brazing clearance of 0·1 mm while those obtained by using Au–Ni and Ag–Cu–Pd filler metals were comparable with the base metal strength at any clearances between 0·1 and 1·5 mm. The laser brazing technique could be successfully applied to the brazing of Ni base superalloy to attain a joint with high performance and reliability.     

The polarization characteristics of Pb-free Sn-8.5Zn-XAg-0.1Al-0.05Ga alloy in 3.5% NaCl solution

The polarization characteristics of Pb-free Sn-8.5Zn-XAg-0.1Al-0.05Ga alloy with varying Ag content were investigated in 3.5% NaCl solution. The value of Ag content i.e X varied from 0.1 wt% to 2 wt%. An increase in the Ag content up to 2 wt% resulted in a progressive increase in the corrosion current density and shifted the corrosion potential (E_corr) towards more active values. These changes were also reflected in the corrosion rate of the solder alloy. However the linear polarization resistance values decreased with increase in the weight content of silver. Increasing the Ag content from 0.1 to 2 wt% did not show a significant improvement in the passivation behaviour of the solder alloy as reflected in the passivation current density (i_p) and critical current density (i_cc) values. XPS and SIMS depth profile results revealed that the oxides of Zn and Sn were present in high concentrations on the outer surface of the solder alloy along with very low concentration of Al₂O₃.     

Influence of turbulent flow on the corrosion of Al‐Zn‐Mg galvanic anode in artificial seawater media

The effect of hydrodynamics on the corrosion of Al(14 wt%)‐Zn(8 wt%)‐Mg alloy in artificial seawater media at room temperature was studied in a rotating cylinder electrode (RCE) system under turbulent flow conditions. Five different rotation rates were studied: 100, 1000, 3000, 5000, and 7000 rpm. The corrosion rates were measured by electrochemical impedance spectroscopy (EIS). For the system studied, the steady‐state corrosion potential increased with increase in rotation rate. The effect of increasing the rotation rate is to increase the availability of oxygen at the surface, which in turn will polarize the corrosion reaction in the more noble direction. The corrosion rate also increases with increase in RCE rotation rate. This reflects the fact that the rate of corrosion is controlled, at least in part, by the rate of mass transfer. In this case, the effect of increase in the rotation rate on the corrosion rate is to increase the interfacial concentration of the reactant (oxygen).     

Characterization of graphene-based supercapacitors fabricated on Al foils using Au or Pd thin films as interlayers

We demonstrate that an Au or Pd interlayer between graphene and an Al-foil current collector plays an important role in enhancing supercapacitor performance. Graphene was prepared by scalable chemical exfoliation and mild thermal reduction (～150 °C) processes. Working electrodes were prepared by coating the graphene on Au/Al or Pd/Al by drop-dry method. The graphene deposited on the noble metals Au and Pd demonstrated excellent supercapacitor performance. Estimated specific energy and specific power of supercapacitors were ～40 Wh/kg and ～40 kW/kg at the current density of ～33 A/g, when operated in organic solution. Altogether, we demonstrate that employing noble metals in the fabrication of graphene-based supercapacitors can lead to excellent performance, and this could be a critical basis for further development of graphene-based supercapacitors.     

The electrochemical behavior of Sn–Ag binary alloys in sulfate solutions

The corrosion and passivation behavior of four binary xSn–Ag (x = 26, 50, 70, and 96.5 wt%) alloys and their pure metal components was investigated in sodium sulfate solutions using electrochemical techniques. The influence of two different electrolytic parameters, namely, concentration (0.01–1.0 M ) and pH (3.0–11.0) were studied while the specimens were potentiodynamically polarized between ?1000 and 500 mV versus saturated calomel electrode (SCE). The results showed that the corrosion current density (i_corr) increases with increasing either the tin content in the alloy or the ions concentration in the electrolyte. Increasing the pH value of a constant composition sulfate solution was found to improve the corrosion resistance of the tin‐richer alloys (x = 50–96.5 wt%), and decreases a little the stability of the silver‐rich one (74 wt% Ag). Impedance measurements at the free corrosion potential (E_corr) give good support for these results, where a small addition of tin to silver up to the intermetallic ratio (x = 26 wt%) gives an alloy with better corrosion resistance to the aggressive sulfate medium. In terms of the tin ratio, the order of surface film stability on the tested samples, generally follows the ranking: 26 > 96.5 > 50 > Ag > 70 > Sn. The good corrosion resistance of the tin‐rich alloy (x = 96.5 wt%), surpassing those for the pure constituents tin and silver can be attributed to the homogenous phase structure of this eutectic mixture.     

Q235上电弧喷涂Zn55Al涂层在3.5wt%溶液中的腐蚀行为研究

本文使用电弧喷涂通过包套挤压+拉拔的方法制备的Zn55Al伪合金丝材成功的在Q235钢上喷涂出了Zn55Al涂层。通过扫描电镜和微区XRD研究了Zn55Al 伪合金丝材的显微结构。通过浸泡腐蚀实验和电化学方法研究了Zn55Al涂层、Zn15Al涂层和 Al涂层的腐蚀行为,并对比了三种涂层之间的差异。结果表明Zn55Al伪合金丝材由纯锌和纯铝组成,在整个成型过程中没有产生合金化。Zn55Al涂层由层片状的富锌相和富铝相组成。经过20天的浸泡实验,Zn55Al涂层形成了一层致密的钝化膜,比其他两种涂层有更好的耐腐蚀性。Zn55Al涂层的自腐蚀电位大约是-1.25v,高于Zn15Al涂层低于纯Al涂层和Q235基体.电偶腐蚀实验表明,Zn55Al涂层比Zn15Al涂层具有更好的点虎穴保护作用。这些结果说明Zn55Al涂层具有更好的耐腐蚀性和可以给Q235基体提供更强的电化学保护.本文也讨论了Zn55Al涂层的的腐蚀机理。     

微电子封装银合金键合线的研究及发展前景

论述了微电子封装中常用的键合金线、键合铜线和键合银线的局限性,从机械性能、键合性能、可靠性等方面分析了键合银合金线的特征及作为键合引线的优势,并在此基础上阐述了键合银合金线重点研究方向以及在未来集成电路封装中的发展前景。     

贵金属嵌入原子参数及贵金属二元合金稀溶解热的计算

采用修正的嵌入原子模型（modified embedded atom method，（MEAM）），给出了Cu，Ag，Au，Ni，Pd，Pt，Rh，Ir等元素的所有嵌入原子参数，用所给参数计算了上述元素的单空位形成能、双空位结合能、结构能量差及由它们构成的二元合金的稀溶解热。计算的稀溶解热与实验结果及已有的理论计算结果进行了比较，现在的计算值与已有的实验结果和Miedema理论计算结果符合得比较好。     

微电子封装用键合金丝替代产品的研究现状

随着电子封装技术的发展,传统键合金丝在性能和价格上已经不具备优势。采用复合和改性等方法可以开发出满足要求的键合金丝替代品。总结了金包银复合键合丝、钯包铜复合键合丝、金合金键合丝和银合金键合丝共4种键合金丝替代产品的性能特点、成分配比、生产技术难点和关键点,介绍了部分典型产品,并对替代产品的发展趋势进行了展望。     

Electrochemical and surface studies on the passivity of a dental Pd-based casting alloy in alkaline sulphide solution

The corrosion and tarnish behavior of a dental casting Pd-25Ag-18Cu-12Au alloy in 0.1% Na₂S solution at 37 °C was investigated using potentiodynamic polarization and spectrocolorimetric techniques. The surface film was characterized by X-ray photoelectron spectroscopy (XPS).This alloy exhibited markedly higher resistance to corrosion and tarnish than did the Ag-20Pd-18Cu-12Au alloy in current clinical use. XPS spectra indicated the presence of a thin sulphide film composed of PdS. It was found that the PdS film is very protective and is responsible for the passivity of the Pd-25Ag-18Cu-12Au alloy in 0.1% Na₂S solution.     

Enhancement of the photoluminescence of porous silicon by sputter deposition of semitransparent metal films

Optoelectronic devices based on porous silicon (PS) undergo substantial degradation in luminescence with aging due to atmospheric oxidation. The passivation of PS has been reported with a transparent conducting material or a semi-transparent metal. In this paper, we report enhancement of the photoluminescence (PL) of PS by the passivation of PS with ultrathin metal films such as silver (Ag), aluminum (Al), and gold (Au). It has been found that Ag and Au are respectively most and least effective in enhancing the PL of PS among those three different metals. The highest PL enhancing effect of Ag is mostly attributed to the high electrical conductivity of Ag, whereas the lowest PL enhancing effect of Au is due to the lowest optical transmittance of Au. The details of the PL enhancing effect of metal passivation are discussed with the aid of FTIR analysis results.     

引线键合中材料参数对硅基板应力状态的影响

利用＂热—力—超声＂增量耦合有限元模型,对采用不同引线（金,铜）以及采用铜引线在不同银镀层厚度（48,1,6μm）条件下的键合过程进行了模拟.结果表明,在其它条件不变的情况下,金引线键合过程对硅基板内应力状态的影响远小于铜引线,且应力集中的位置更接近键合中心;随着镀层厚度的增加,基板所受到的压应力逐渐减小,但基板所受到的最大压应力在硅的抗压力范围之内;同时基板所受到的剪应力也逐渐减小,由于剪应力是硅基板损坏的决定性因素,因此采用厚度为16μm的镀层对减小基板损坏更有利.