Al-Ni超声楔焊中输入功率与界面键合的特征分析

为了研究超声键合中在超声能量作用下金属间形成键合界面而构成键合力的机理,确定金属间吸收的超声能量与形成的界面质量的关系,在超声楔焊键合试验中,对Al-Ni楔焊通过改变焊接参数而获得完全键合和半键合的界面,并对其界面特征进行扫描电镜测试分析;同时,利用示波器采集超声键合机焊接时的电信号,分析了PZT驱动的输入阻抗和功率特性,并与界面质量对比.研究结果表明:超声键合而形成的Al-Ni界面为中央未键合的椭圆界面;相同参数条件下,一焊输入阻抗和吸收功率大于二焊,一焊的界面质量也高于二焊.     

Mechanisms of Peeling Failures of Bonds During Ultrasonic Wedge Bonding

The metallization of wire bonding pads on Si-based integrated circuits (ICs) contains Ti, TiN, and Al layers with vertical W-plugs located through the Ti and TiN layers. One percent Si-Al wire (32 µm in diameter) was bonded on the pads by an ultrasonic transducer using a wire bonding machine. Peeling failures occurred during the ultrasonic bonding process. The peeling fractures were examined using a scanning electron microscope (SEM) with an energy-dispersive spectroscopy (EDS) system. The results showed that bonds peeled off from the interface between the Al layer and the top surface of the W-plugs or from the interface between the Si-base and the bottom surface of the W-plugs. The distribution of W-plugs also affected the bond peeling from the top or bottom surfaces of the W-plugs. Mechanisms giving rise to the peeling failure of bonds were analyzed based on the acoustic impedance of materials, which determined the amount of ultrasonic energy transmitted from one material to another. Two different paths of ultrasonic energy transmission occurred during the bonding process due to the different acoustic impedances of the materials. One is from the Al layer, through the TiN and Ti layers, to the IC. The other is from the Al layer, through the W-plugs, to the IC. The different distributions of ultrasonic energy at the positions with W-plugs and without W-plugs caused stress concentrations around the top or bottom surfaces of the W-plugs, which resulted in peeling failures of the bonds.     

Effect of Ni interlayer on characteristics of diffusion bonded Mg/Al joints

Magnesium and aluminium were joined through diffusing bonding with a Ni interlayer prepared by plasma spraying for the first time. Examination of the microstructure and phase constitution of interfacial regions indicated that Mg–Al reaction was successfully prevented in the presence of the Ni interlayer. With the elevation of temperature, a reaction layer of Mg₂Ni intermetallic was formed at Mg/Ni interface but few Al–Ni intermetallic was generated at Al/Ni interface. The mechanical test results showed that the tensile strength of the Mg/Al joint was substantially improved compared to that of the direct joint of Mg and Al. A maximum value of 5.8?MPa was obtained at 420°C for the joint with Ni interlayer.     

Fundamentals of thermo-sonic copper wire bonding in microelectronics packaging

Fine copper wire bonding is capable of making reliable electrical interconnections in microelectronic packages. Copper wires of 0.8–6 mil diameter have been successfully bonded to different bond pad metallized and plated substrate materials such as Al, Cu, Ag, Au and Pd. The three metallurgical related factors; solid-solubility and diffusion of dissimilar contact metals, oxide film breakage and plastic deformation of asperities play a critical role in the bonding. Plastic deformation of an asperity is the most significant factor one has to consider to attain good bonding. Soft aluminum metal (30–40 VHN), with a lower % asperity threshold deformation is easier to wire bond than harder metallic surfaces (Ni, W, Mo, Cr, Co, Ta) of 150–500 VHN. Good adhesion of wire bonding is achieved for the surface roughness (Ra) of 0.01–0.15 μm and 0.02–0.6 μm of bare and plated surfaces respectively. It is rationalized that the application of ultrasonic energy principally breaks the oxide film and deform the asperities, while a compressive force increases the proximity of asperities. Hence wire welds to bond pad surface by molecular attraction and inter diffusion. Storage of copper ball bonds at 175 °C for 100–1,000 h forms copper aluminide at the interface. EDAX and Auger analysis reveal 22 at% Al + 78 at% Cu composition of the aluminides and Cu₃Al₂ empirical formula is calculated, which, does not match with any of the reported copper aluminides. Hardness of the copper ball bonds and stitch bonds are higher than wire exhibiting work hardening of the bonds on processing.     

Effect of Wetting and NiAl_2O_4 Spinel Formation on the Bonding between Al_2O_3 and Ni

Al2O3-Ni interface formed under vacuum condition is non-wetting and weak. Severe instantaneous intedecial reaction (i.e. wetting) at the Al2O3-Ni interface promoted by oxygen can create a strengthened interface. The NiAl2O4 spinel-Ni intedece is weak and growth of the spinel interphase is detrimental to the Al2O3-Ni intedecial bonding. A proper control of the oxygen partial pressure can achieve wetting while avoiding the existence of spinel at the interface, producing stronger interfaces by both mechanical interlocking and more intimate chemical bonding in an Al2O3-20 vol pct Ni composite.     

Improvement of Joint Strength of SiCp/Al Metal Matrix Composite in Transient Liquid Phase Bonding Using Cu/Ni/Cu Film Interlayer

The compact oxide on the surface of SiCp/Al metal matrix composite （SiCp/Al MMC） greatly depends on the property of the joint. Inlaid sputtering target was applied to etch the oxide completely on the bonding surface of SiCp/Al MMC by plasma erosion. Cu/Ni/Cu film of 5μm in thickness was prepared by magnetron sputtering method on the clean bonding surface in the same vacuum chamber, which was acted as an interlayer in transient liquid phase （TLP） bonding process. Compared with the same thickness of single Cu foil and Ni foil interlayer, the shear strength of 200 MPa was obtained using Cu/Ni/Cu film interlayer during TLP bonding, which was 89.7% that of base metal. In addition, homogenization of the bonding region and no particle segregation in interfacial region were found by analysis of the joint microstructure. Scanning electron microscopy （SEM） was used to observe the micrograph of the joint interface. The result shows that a homogenous microstructure of joint was achieved, which is similar with that of based metal.     

Microstructural characteristics of Au/Al bonded interfaces

Fracture characteristics at the interface of ultrasonic bonds between Au and Al were characterized by SEM following pull-testing to effect separation of the bonded joints. Vertical sections at the bonding point were produced by ion-sputter thinning, and were examined by TEM. Results show that the thickness of the Au/Al atomic diffusion interface was about 500 nm due to combined effects of ultrasonic and thermal energy. Ultrasonic vibration activates dislocations in the crystalline lattice and increases atomic diffusion. The fracture morphology on the lift-off interface was dimpled rupture. Tensile fracture occurred during the pull-test not at the bonded interface but in the base material; the bond strength at the interface was enhanced by the diffusion reactions that occurred across the interface due to the combined ultrasonic and thermal energy.     

Al-Cu双金属复合结构的扩散连接试验研究

应用扩散连方法进行了Al-Cu双金属复合结构的试验研究，比较了不同的焊接工艺，材料组合以及母材状态情况Al合金与Cu的连接性，观察了接头区域的微观组织结构，研究表明，固相扩散连接是一种适用于异种材料连接的有效方法，通过在连接区域形成Al-Cu金属间化合物，达到Al和Cu的有效连接，材料组合，母材原始状态以及连接工艺参数对Al合金与Cu的扩散连接存在着明显的影响。表面镀Ni工艺不但能够有效阻止Al和Cu之间形成脆性相，而且Al和Ni之间形成了良好的扩散连接，改善了接头性能。     

Effect of process parameters on semi-solid TLP bonding of Ti–6Al–4V to Mg–AZ31

The semi-solid transient liquid-phase bonding (Semi-solid TLP bonding) of titanium alloy Ti–6Al–4V to magnesium alloy Mg–AZ31 was performed using a eutectic forming nickel foil. The process parameters were optimized to achieve higher shear strength. The effect of temperature and pressure on microstructure evolution and mechanical characteristics were examined for bonding time between 5 and 60 min. Three reaction layers L1, L2 at Ni/Mg–AZ31 interface and L3 along the Ni/Ti–6Al–4V interface were determined within joint zone at a bonding temperature of 515 °C. The L1 and L2 reaction layers continued to be seen when the bonding temperature increased to 540 °C. When the bonding pressure increases from 0.2 to 0.7 MPa, a new reaction layer L4, at the Ni/Ti–6Al–4V interface was observed. The results showed that as the bonding time increased up to 60 min, the width of the joint decreased due to isothermal solidification. Maximum shear strength of 39 MPa was obtained for 540 °C and 0.2 MPa with a holding time of 20 min. However, further increase in bonding time to 60 min resulted in a decrease in shear strength to 8 MPa, and this decrease in strength was attributed to the increase in intermetallics forming within the joint zone.     

Improving friction stir weldability of Al/Mg alloys via ultrasonically diminishing pin adhesion

Formation of intermetallic compounds (IMCs) during friction stir welding (FSW) of aluminum/magnesium (Al/Mg) alloys easily results in the pin adhesion and then deteriorates joint formation. The severe pin adhesion transformed the tapered-and-screwed pin into a tapered pin at a low welding speed of 30 mm/min. The pin adhesion problem was solved with the help of ultrasonic. The weldability of Al/Mg alloys was significantly improved due to the good material flow induced by mechanical vibration and the fragments of the IMCs on the surface of a rotating pin caused by acoustic streaming, respectively. A sound joint with ultrasonic contained long Al/Mg interface joining length and complex mixture of Al/Mg alloys in the stir zone, thereby achieving perfect metallurgical bonding and mechanical interlocking. The ultrasonic could broaden process window and then improve tensile properties. The tensile strength of the Al/Mg joint with ultrasonic reached 115 MPa.     

Brazing of WC–8Co cemented carbide to steel using Cu–Ni–Al alloys as filler metal: Microstructures and joint mechanical behavior

Three novel Cu–Ni–Al brazing filler alloys with Cu/Ni weight ratio of 4:1 and 2.5–10 wt% Al were developed and characterized, and the wetting of three Cu–Ni–Al alloys on WC–8 Co cemented carbide were investigated at 1190–1210?C by the sessile drop technique. Vacuum brazing of the WC–8 Co cemented carbide to SAE1045 steel using the three Cu–Ni–Al alloys as filler metal was further carried out based on the wetting test results. The interfacial interactions and joint mechanical behaviors involving microhardness, shear strength and fracture were analyzed and discussed. The experimental results show that all the three wetting systems present excellent wettability with final contact angles of less than 5?and fast spreading. An obvious degeneration layer with continuous thin strip forms in the cemented carbide adjacent to the Cu–Ni–Al/WC–8 Co interface. The variation of microhardness in the joint cross-section is closely related to the interactions(such as diffusion and solid solution) of WC–8 Co/Cu–Ni–Al/steel system. Compared with the other two brazed joints, the WC–8 Co/Cu–19 Ni–5 Al/steel brazed joint presents more reliable interlayer microstructure and mechanical property while brazing at the corresponding wetting temperatures for 5 min, and its average shear strength is over 200 MPa after further optimizing the brazing temperature and holding time. The joint shear fracture path passes along the degeneration layer, Cu–Ni–Al/WC–8 Co interface and brazing interlayer, showing a mixed ductile-brittle fracture.     

Comparative performance of gold wire bonding on rigid and flexible substrates

This paper reports comparative performance of wire bondability of electrolytically plated Au/Ni/Cu bond pads on rigid FR-4 and bismaleimide trazine (BT) PCBs, as well as flexible polyimide (PI) substrate. The metallization surfaces were treated with plasma to study the effect of bond pad surface cleanliness on wire bondability. Process windows were constructed as a function of bonding temperature and bond power for the individual substrate materials. Significant improvements of wire pull strength and process window were noted after plasma treatment with a substantial reduction in minimum bonding temperature from 120°C to 60°C for both the rigid and flexible substrates. The minimum bond power required to produce successful bonds decreased with increasing bonding temperature. At a bonding temperature of 120°C, the process window for the flexible substrate was wider than the rigid substrates. The wire bondability and wire pull strength of rigid substrates decreased with increasing bonding temperature above 120°C due to softening of the substrate which adversely affected the effective bond force and the transmission of ultrasonic energy. In contrast, the wirebonding performance of the flexible substrate remained stable at 120°C or above because the thermo-mechanical properties of flexible PI substrate were rather insensitive to temperature. The process windows of flexible substrates with and without stiffener showed similar bondability.     

Effect of Ni interlayer on strength and microstructure of diffusion-bonded Mo/Cu joints

Mo and Cu were bonded successfully by means of diffusion bonding using a Ni interlayer. The tensile strength of the joint increases firstly and then decreases with the bonding temperature or holding time increases. Compared with 79 MPa which was the maximum value of Mo/Cu joint, the maximum tensile strength of joint with Ni interlayer was 97 MPa. The interfacial structure of the joints was studied by SEM, EPMA, EDS and XRD, the results showed that the different atoms diffused to each other in the bonding process and no intermetallic compound appeared. MoNi and NiCu solid solutions formed in the joint. The fracture of the joint had taken place in the Mo/Ni interface rather than in the Ni/Cu interface and the fracture way of the joints was brittle fracture.     

NiCuMn对C/Al扩散焊界面结合性能的影响

研究了高强碳纤维镀Ni和镀NiCuMn对C/Al扩散焊界面结合性能的影响,重点分析了Mn元素提高C/Al界面结合性能的机理,并根据不同锰含量下的δ和σc值,建立了δ与σc的数学模型。     

镍铝复合丝和镍铝合金丝及其涂层

介绍了镍铝复合丝和镍铝合金丝及其涂层的成分、相结构 ,比较分析了涂层的结合强度 ,分析了涂层自结合作用机理 ,估算了喷涂一平方米面积所消耗的丝材及相应用丝材成本 ,介绍了两种材料适用的对象及设备     

Effect of Cr and Ni on diffusion bonding of Fe3Al with steel

Microstructure at the diffusion bonding interface between Fe₃Al and steel including Q235 low carbon steel and Cr18-Ni8 stainless steel was analysed and compared by means of scanning electron microscopy and transmission electron microscopy. The effect of Cr and Ni on microstructure at the Fe₃Al/steel diffusion bonding interface was discussed. The experimental results indicate that it is favourable for the diffusion of Cr and Ni at the interface to accelerate combination of Fe₃Al and steel during bonding. Therefore, the width of Fe₃Al/Cr18-Ni8 interface transition zone is more than that of Fe₃Al/Q235. And Fe₃Al dislocation couples with different distances, even dislocation net occurs at the Fe₃Al/Cr18-Ni8 interface because of the dispersive distribution of Cr and Ni in Fe₃Al phase.     

Interfacial structure and strength on Ti(C,N) joint using liquid phase diffusion bonding with Ti/Ni interlayer

Abstract

Partial transient liquid phase diffusion bonding (PTLP-DB) on Ti(C,N) cermet was studied in the present paper using Ti/Ni/Ti foil sandwich structure as the interlayer. The interfacial structure and element distribution at the interface were observed using SEM, electron probe microanalysis and X-ray diffraction. The joint strength was measured using four-point bending test. The results showed that metallurgical bonding between Ti(C,N) cermet was achieved using PTLP-DB. Near Ti(C,N) cermet side, a strong chemical reaction occurred to produce an interfacial multilayer containing Ti–Al and Ti–Ni intermetallics. Different bonding times during PTLP-DB were also studied, and there was an optimum time during bonding. With a shorter bonding time, voids were observed at the interface, while with a prolonged time, the bending strength on the joints also decreased due to the overgrowth on intermetallic layer and the existence of high gradient residual stress at the interface.     

Transient liquid phase (TLP) bonding of Al7075 to Ti–6Al–4V alloy

TLP diffusion bonding of two dissimilar aerospace alloys, Ti–6Al–4V and Al7075, was carried out at 500 °C using 22 μm thick Cu interlayers for various bonding times. Joint formation was attributed to the solid-state diffusion of Cu into the Ti alloy and Al7075 alloy followed by eutectic formation and isothermal solidification along the Cu/Al7075 interface. Examination of the joint region using SEM, EDS and XPS showed the formation of eutectic phases such as, ?(Al₂Cu), T(Al₂Mg₃Zn₃) and Al₁₃Fe along grain boundaries within the Al7075 matrix. At the Cu/Ti alloy bond interface a solid-state bond formed resulting in a Cu₃Ti₂ phase formation along this interface. The joint region homogenized with increasing bonding time and gave the highest bond strength of 19.5 MPa after a bonding time of 30 min.     

Wettability of CuNi-Ti Alloys on Si_3N_4 and Interfacial Reaction Products

Based on the alloy Cu55Ni45 (at pct), holding the proportion of Cu to Ni in constant and in the temperature range of 1233~1573 K, the wetting angles of CuNi-0~56 at pct Ti alloys on Si3N4 have been measured by the sessile drop method. With the increase of Ti content, the wetting angles decreased. The equilibrium wetting angle was 5° when Ti content ≥32 at pct.In the case of same Ti content, the activity of Ti in CuNiTi alloy was weaker than that in CuTi alloy The cross-section of the CuNiTi-Si3N4 interface and the elements distribution were examined by scanning electron microscope with X-ray wave-dispersion spectrometer, and the reaction products formed at the interface were determined by X-ray diffiaction analysis method.     

Influence of Water Vapor on the Isothermal Oxidation Behavior of Thermal Barrier Coatings

The oxidation of specimens with thermal barrier coating (TBC) consisted of nickel-base superalloy, low-pressure plasma sprayed Ni-28Cr-6AI-0.4Y (wt pct) bond coating and electron beam physical vapor deposited 7.5 wt pct yttria stabilized zirconia (YSZ) top coating was studied at 1050℃ respectively in flows of 02, and mixture of O2 and 5%H2O under atmospheric pressure. The thermal barrier coating has relatively low oxidation rate at 1050℃ in pure O2. Oxidation rate of thermal barrier coating in the atmosphere of O% and 5%H2O is increased The oxidation kinetics obeys almost linear law after long exposure time in the presence of 5% water vapor. Oxide formed along the interface between bond coat and top coat after oxidation at 1050℃ in pure O2 consisted of Al2O3, whereas interfacial scales formed after oxidation at 1050℃ in a mixture of O2 and 5%H2O were mainly composed of Ni(AI,Cr)2O4,NiO and AI2O3. It is suggested that the effect of water vapor on the oxidation of the NiCrAlY coating may be attributed