Microstructure of aluminum/copper clad composite fabricated by casting-cold extrusion forming

An aluminum/copper clad composite was fabricated by the casting-cold extrusion forming technology and the microstructures of the products were observed and analyzed.It is found that aluminum grains at the interface are refined in the radial profiles of cone-shaped deformation zone,but the grains in the center maintain the original state and the grain size is non-uniform.A clear boundary presents between the refined area and center area.In contrast,the copper grains in the radial profiles have been significantly refined.In the center area of the copper,the grains are bigger than those at the boundary.On the surface of the deformable body,the grain size is the smallest,but with irregular grain morphology.After the product is entirely extruded,all the copper and aluminum grains are refined with small and uniform morphology.In the center area,the average diameter of aluminum grains is smaller than 5 μm,and the copper grain on the surface is about 10 μm.At the interface,the grain size is very small,with a good combination of copper and aluminum.The thickness of interface is in the range of 10-15 μm.Energy spectrum analysis shows that CuAl3 phase presents at the interface.

Cu-Al interfacial compounds and formation mechanism of copper cladding aluminum composites

Copper cladding aluminum(CCA)rods with the section dimensions of12mm in diameter and2mm in sheath thickness were fabricated by vertical core-filling continuous casting(VCFC)technology.The kinds and morphology of interfacial intermetallic compounds(IMCs)were investigated by SEM,XRD and TEM.The results showed that the interfacial structure of Cu/Al was mainly composed of layeredγ1(Cu9Al4),cellularθ(CuAl2),andα(Al)+θ(CuAl2)phases.Moreover,residual acicularε2(Cu3Al2+x)phase was observed at the Cu/Al interface.By comparing the driving force of formation forε2(Cu3Al2+x)andγ1(Cu9Al4)phases,the conclusion was drawn that theε2(Cu3Al2+x)formed firstly at the Cu/Al interface.In addition,the interfacial formation mechanism of copper cladding aluminum composites was revealed completely.

Numerical simulation of temperature field in horizontal core-filling continuous casting for copper cladding aluminum rods

The steady-state temperature field of horizontal core-filling continuous casting （HCFC） for producing copper cladding aluminum rods was simulated by finite element method to investigate the effects of key processing parameters on the positions of solid-liquid interfaces （SLIs） of copper and aluminum. It is found that mandrel tube length and mean withdrawing speed have significant effects on the SLI positions of both copper and aluminum. Aluminum casting temperature （TAI） （1003-1123 K） and secondary cooling water flux （600-900 L.h-1） have little effect on the SLI of copper but cause the SLI of aluminum to move 2-4 mm. When TA1 is in a range of 1043-1123 K, the liquid aluminum can fill continuously into the pre-solidified copper tube. Based on the numerical simulation, reasonable processing parameters were determined.

Orthogonal tests of copper-clad aluminum bimetal continuous casting by nitrogen pressure core-illing

To provide theoretical basis and practical guidance for preparing composite rods by direct continuous casting, copper-clad aluminum composite rods of external copper layer diameter 12 mm and inner aluminum core diameter 8 mm were manufactured. Orthogonal tests consisted of three factors and three levels were carried out to research the effects of melting copper temperature, continuous casting speed and nitrogen pressure on the performance of composite rods. Results showed that nitrogen pressure is the most important factor in influencing the surface quality; continuous casting speed is the most important factor in influencing copper & aluminum inter diffusion amount. Nitrogen pressure can noticeably improve the surface quality and make the rods easily be drawn out, but the surface quality does not show visible improvement when the nitrogen pressure is above 0.05 MPa. Measured by tests, the compound layer can be divided into three types according to its cladding layer degree: deficient cladding, normal cladding and excess cladding. The diameter of normal copper-clad aluminum composite rods can be successfully drawn less than 0.6 mm without annealing.

Vision-based detection of weld pool width in TIG welding of copper-clad aluminum cable

In order to realize automatic control of the width of weld pool, a visual sensor system for the width of weld pool detection is developed. By initiative arc light, the image of copper plate weld pool is taken back of the torch through the process of weakening and filtering arc light. In order to decrease the time of processing video signals, analog circuit is applied in the processing where video signals is magnified, trimmed and processed into binary on the datum of dynamic average value, therefore the waveform of video signals of weld pool is obtained. The method that is used for detecting the width of weld pool is established. Results show that the vision sensing method for real-time detecting weld pool width to copper-clad aluminum wire TIG welding is feasible. The response cycle of this system is no more than 50 ms, and the testing precision is less than 0. 1 mm.

Laser cladding of Ni-based alloy on copper substrate

The laser cladding of Ni1015 alloy on Cu substrate was prepared by a high power continuous wave CO2 laser. Its microstructure was analyzed by optical microscope （OM）, scanning electron microscope （SEM）, and X-Ray diffraction （XRD）. The average microhardness of the cladding coating was Hv 280, which was almost three times of that of the Cu substrate （Hv 85）. OM and SEM observations showed that the obtained coating had a smooth and uniform surface, as well as a metallurgical combination with the Cu substrate without cracks and pores at the interface. With the addition of copper into the nickel-based alloy, the differences of thermal expansion coefficient and melting point between the interlayer and cladding were reduced, which resulted in low stresses during rapid cooling. Moreover, large amount of （Cu, Ni） solid solution formed a metallurgical bonding between the cladding coating and the substrate, which also relaxed the stresses, leading to the reduction of interfacial cracks and pores after laser cladding.

Effect of continuous induction annealing on the microstructure and mechanical properties of copper-clad aluminum flat bars

Copper-clad aluminum （CCA） flat bars produced by the continuous casting-rolling process were subjected to continuous induction heating annealing （CIHA）, and the effects of induction heating temperature and holding time on the microstructure, interface, and mechanical properties of the fiat bars were investigated. The results showed that complete recrystallization of the copper sheath occurred under CIHA at 460℃ for 5 s, 480℃ for 3 s, or 500℃ for 1 s and that the average grain size in the copper sheath was approximately 10.0 μm. In the case of specimens subjected to CIHA at 460-500℃ for longer than 1 s, complete recrystallization occurred in the aluminum core. In the case of CIHA at 460-500℃ for 1-5 s, a continuous interracial layer with a thickness of 2.5-5.5 μm formed and the thickness mainly increased with increasing annealing temperature. After CIHA, the interracial layer consisted primarily of a Cu9A14 layer and a CuA12 layer; the average interface shear strength of the CCA flat bars treated by CIHA at 460-500℃ for 1-5 s was 45-52 MPa. After full softening annealing, the hardness values of the copper sheath and the aluminum core were HV 65 and HV 24, respectively, and the hardness along the cross section of the CCA flat bar was uniform.

Microstructure and properties of pure iron/copper composite cladding layers on carbon steel

In the present study, pure iron/copper composite metal cladding was deposited onto carbon steel by tungsten inert gas welding. The study focused on interfacial morphological, microstructural, and mechanical analyses of the composite cladding layers. Iron liquid–solid-phase zones were formed at copper/steel and iron interfaces because of the melting of the steel substrate and iron. Iron concentrated in the copper cladding layer was observed to exhibit belt, globule, and dendrite morphologies. The appearance of iron-rich globules indicated the occurrence of liquid phase separation（LPS） prior to solidification, and iron-rich dendrites crystallized without the occurrence of LPS. The maximum microhardness of the iron/steel interface was lower than that of the copper/steel interface because of the diffusion of elemental carbon. All samples fractured in the cladding layers. Because of a relatively lower strength of the copper layer, a short plateau region appeared when shear movement was from copper to iron.

Novel Reduced-friction Materials by Laser Cladding of Copper Alloy on Cast Iron

Copper alloys suitable for laser cladding on cast iron are selected trom rune types of conventional powders. There are a poor spreading ability and porosity of copper alloy over the surface of castiron. Copper alloy surface is easily oxidized in atmosphere. These shortages have been overcome by ad- ding deoxidizers of Si and H_3BO_3. Laser parameters, stress and coefficient of friction have been ex- amined, and the larger smooth surface of Cu/cast iron for friction by laser cladding has been made for the application of the guide shoes of machine.

热塑型聚酰亚胺的制备及其粘接性能研究

为了改善两层型挠性覆铜板(2L-FCCL)中热塑型聚酰亚胺(TPI)对热固型聚酰亚胺(PI)薄膜和铜箔的粘接性,本文选用具有柔性结构的芳香二酐单体和芳香或脂环的二异氰酸酯单体通过一步反应制备得到TPI样品,然后将其直接涂覆在表面经过预处理的商品化热固型PI薄膜上得到复合膜,最后经过高温热压得到相应的2L-FCCL。通过观察所得TPI反应液的状态并进行DSC测试,选定了有机溶剂可溶且Tg为226.5℃的TPI-8;然后通过TGA、TMA和拉伸试验测得TPI-8的2%热分解温度(T2%)为464℃、50~200℃的热膨胀系数(CTE)为64.25×10^(-6)℃^(-1)、拉伸强度为64.52MPa、弹性模量为1.75 GPa、断裂伸长率为62%,并通过FTIR对其化学结构进行了确认;最后分别研究了两种热固型PI薄膜的碱水预处理时间对所得FCCL粘接性能的影响,发现其中SPI膜经60℃碱水处理1 min和3 min后得到的FCCL90°剥离强度(90°PS)≥0.7 N/mm且最大值达到0.94 N/mm,而UPI膜经同样热碱水处理1~7 min后得到的FCCL 90°PS均≤0.6 N/mm。因此,采用本方法可一步快速简单的制备可溶解且热学性能、力学性能、尺寸稳定性较好的TPI,同时其对铜箔以及表面经过碱水预处理的SPI具有较好的粘接性能,满足FCCL相关标准的要求。

碳氢树脂高频覆铜板的研究进展

本文综述了高频覆铜板的特点,并对其基体树脂的介电性能进行对比,重点介绍了碳氢树脂(PCH)高频覆铜板的研究进展。通过对目前碳氢树脂高频覆铜板研究的总结,找出现存的问题并对其未来发展趋势进行展望。

国产聚酰亚胺柔性覆铜板材料介电性能测评

介绍了聚酰亚胺柔性覆铜板的主要电性能指标及其典型应用场景,明确了柔性覆铜板介电性能测评流程。在完成谐振环仿真及设计后,开展ASG-TL00060UF2国产高性能聚酰亚胺柔性覆铜板与进口板材的常温和湿热试验,进行介电性能对比测试计算。最后给出了国产聚酰亚胺柔性覆铜板材料介电性能测评结论。

低温固化低介电聚酰亚胺的合成及其在覆铜板上的应用

为降低聚酰亚胺(PI)材料的介电性能及亚胺化温度以获得较好性能的PI覆铜板,本文采用4,4′-(六氟异丙烯)二酞酸酐(6FDA)、4,4′-二氨基二苯醚(ODA)、1,3-双(4′-氨基苯氧基)苯(TPE-R)、双酚型二醚二酐(BPADA)4种单体合成聚酰胺酸(PAA)溶液,然后向PAA溶液中引入3种可降低亚胺化温度的催化剂[喹啉(QL)、苯并咪唑(BI)、三乙胺(Et_(3)N)],在较低温下进行热亚胺化制备成PI材料,并对该材料进行热稳定性、拉伸性能、黏接性能、光学性能的表征与测试。结果表明,3种催化剂固化的PI薄膜均具有较好的热稳定性和优异的光学性能,PI/QL的拉伸强度(70.23 MPa)最佳,PI/QL的吸水率下降至0.26%,PI/Et_(3)N的介电常数(2.54)最低,PI/Et_(3)N能维持原PI的剥离强度(1.56 N/mm),3种低温固化PI的最高耐锡焊温度为296℃。

可溶解热塑性聚酰亚胺薄膜的制备和性能研究

为了改善传统热塑性聚酰亚胺(TPI)的溶液加工性并提高其耐热性和粘接性,采用不同的商品化二酐单体分别与自制的主链含有吡啶和二苯醚结构及活性苯酚侧基或苯侧基的二胺单体通过两步法制备了一系列可溶解热塑性聚酰亚胺(TPI)树脂,随后制备了相应的TPI薄膜以及挠性覆铜板(FCCL)。通过溶解性试验和凝胶渗透色谱(GPC)分析TPI树脂的性能,然后测试分析了TPI薄膜的结构、吸水率、力学性能、热学性能和介电性能,并对其FCCL的相关性能进行测试。结果表明:TPI树脂均能溶解于NMP等强极性有机溶剂,相应薄膜的玻璃化转变温度(T_(g))均为236.8~325.6℃,5%热失重温度(T_(5%))为508.7~553.7℃,800℃残留率(R_(800))均高于64%,热膨胀系数(CTE)为56.36×10^(-6)~78.30×10^(-6)℃^(-1),拉伸强度为64.93~109.18 MPa,断裂伸长率为9.09%~24.60%,吸水率为0.74%~3.75%。综合性能相对较优的TPI-4的介电常数和介质损耗因数也相对较低,相应FCCL的剥离强度达到0.95 N/mm,但只能通过288℃/10 s的耐浮焊测试。此外,TPI-4中极性的苯酚侧基不仅保证了其有机溶解性,对其耐热性和机械强度也有明显的增强作用,同时还降低了其CTE值。具有反应活性的苯酚侧基为TPI的后续化学改性提供了极大的便利,通过加入少量的氰酸酯树脂(CE01)对其进行改性可以明显改善其与热固性PI薄膜或铜箔的粘接性能并提高相应FCCL的耐浮焊性。

铝基板阳极氧化封孔工艺对覆铜板性能的影响

[目的]探究铝基板阳极氧化封孔工艺对覆铜板性能的影响。[方法]先采用草酸对7075铝合金阳极氧化,再在真空条件下采用Al_(2)O_(3)溶胶或/和ZnO溶胶进行封孔处理,并在300℃下加热固化。研究了两种溶胶单独封孔或组合封孔及封孔次数对阳极氧化膜导热系数与耐电压强度的影响。此外,还采用封孔样品为基板,分别通过溅射镀铜与热压合工艺制备铝基覆铜板。[结果]采用Al_(2)O_(3)溶胶和ZnO溶胶交替封孔4次可将阳极氧化膜的耐电压强度提升2.90倍左右,但会使其导热性略微变差。通过溅射镀铜所得覆铜板的剥离强度高达1.15N/mm,并且耐热性良好。[结论]对铝基板进行阳极氧化封孔能够显著改善覆铜板的性能。

Cu-Ti复合焊料钎焊Si_(3)N_(4)陶瓷/Cu的显微结构和力学性能研究

本研究采用Cu-Ti复合焊料在不同温度和保温时间钎焊了Si_(3)N_(4)/Cu接头,研究了不同钎焊参数对接头显微组织和力学性能的影响。实验结果表明,接头的相组成主要是TiN、Ti_(5)Si_(3)和Cu-Ti化合物。在较低温度(890℃)下,Ti_(5)Si_(3)率先生长,较少的Ti扩散到了Cu里生成Cu_(3)Ti;当延长保温时间或提升钎焊温度(920℃)时,TiN在界面处沉积成薄层,Cu_(3)Ti也转变成了CuTi,同时,Ti_(5)Si_(3)在Cu里也有一定的扩散;当钎焊温度过高(950℃)时,Ti和Si_(3)N_(4)的反应程度较大,Cu-Ti化合物作为反应的中间相被消耗,剥离强度随着温度的升高呈现先升高后下降的趋势。在920℃钎焊60 min的接头中,TiN逐渐剥离出薄层,进一步优化界面组织,接头剥离强度最高,达到16.69 N·mm^(-1)。

SiC功率模块封装材料的研究进展

随着SiC功率模块的高频高速、高压大电流、高温、高散热和高可靠发展趋势,基于封装结构和封装材料的SiC功率模块封装技术也在不断地更新换代。与封装结构相比,SiC功率模块封装材料的相关研究报道较少。该文从封装材料角度出发,综述近年来陶瓷覆铜基板、散热底板、黏结材料、互连材料及灌封材料的研究进展,同时引出相关封装材料的研究重点,以满足SiC功率模块的应用需求。

高孔隙率聚酰亚胺微孔膜的制备及其介电性能

以3,3′,4,4′-联苯四甲酸二酐(BPDA)和4,4′-二氨基-2,2′-二甲基-联苯(mTB)为单体,加入致孔剂,利用热致相分离原理,控制聚酰胺酸的高温热亚胺化过程,制备高孔隙率聚酰亚胺薄膜,并对薄膜的微孔形貌、力学性能及介电性能等进行分析。结果表明:多孔薄膜的孔隙率可达50%~60%,其中试样PI-1-250-4 h在10 GHz下的介电常数为2.14,介质损耗因数为0.0028,同时保持了良好的力学性能和耐热性。由于刚性联苯结构单元的引入,多孔薄膜仍然保持了较低的热膨胀系数。将多孔薄膜与热塑性聚酰亚胺(TPI)复合,高温压合铜箔后,所组成的无胶双面覆铜板具有较好的界面粘接性和耐焊锡性,可应用于高频高速挠性覆铜板领域。

微波多腔体外壳导电胶粘接覆铜板失效原因分析与解决

[目的]某微波多腔体外壳(可伐材料)镀镍/金后,在通过导电胶粘接覆铜板时出现导电胶与可伐腔体不浸润、导电胶开裂、覆铜板从可伐腔体外壳上剥离等不良现象。[方法]通过建立故障树,结合能谱分析、水滴试验和剪切力测试,对上述问题的主要影响因素逐一进行分析。[结果]导电胶粘接失效的主要原因是镀金后浸泡金保护剂工艺参数不当,以及转运过程中所用包装盒上的微量硅油沾污了外壳表面。[结论]在导电胶粘接前对微波多腔体外壳进行化学清洗,以及禁用含硅油的包装盒后,未再出现粘接失效现象。

倒角结晶器铜板镀层崩边原因分析及控制

针对倒角结晶器窄面铜板镀层崩边问题,从结晶器传热、铜板结构、镀层性能等角度分析原因,提出采用激光熔覆技术对铜板表面进行强化的解决方案,并开展了工业试验进行验证。研究结果表明:铜板角部温度高、镀层厚度大、镀层与铜板热变形差异大、在线调宽状态下铜板侧面清渣不彻底是影响镀层发生崩边的重要原因。采用激光熔覆技术后,倒角窄面铜板的过钢量由5万t提高到10万t以上,当过钢量达到8.7万t时,熔覆层仍未出现角部崩边、剥落及因磨损过大引起的局部露铜现象。