铜含量对Sn-Cu钎料与Cu、Ni基板钎焊界面IMC的影响

研究了不同铜含量的Sn-xCu钎料(x=0,0.1%,0.3%,0.7%,0.9%,1.5%)与Cu板和Ni板在260、280和290℃钎焊后界面金属间化合物(IMC)的成分和形貌。研究结果表明:钎料与Cu板钎焊时,钎焊温度越高,界面处形成的Cu6Sn5IMC厚度越大,而在同一钎焊温度下,随着钎料中铜含量的增加,IMC的厚度先减少后增加;与Ni板钎焊时,界面IMC的厚度随着铜含量的增加而增加,同时界面化合物的成分和形貌均发生了显著变化;当Cu含量小于0.3%(质量分数)时,界面处形成了连续的(CuxNi1-x)3Sn4层;而当Cu含量为0.7%时,界面处同时存在着短棒状(CuxNi1-x)3Sn4和大块状(CuxNi1-x)6Sn5IMC;当铜含量继续增大时(0.9%~1.5%),(CuxNi1-x)3Sn4IMC消失,只发现了棒状(CuxNi1-x)6Sn5IMC。讨论了钎料中Cu含量对与Cu、Ni基板钎焊接头界面化合物生长的影响,并进一步讨论了(CuxNi1-x)6Sn5IMC的形成和长大机理。     

Sn-6.5Zn钎料/Cu基板焊点界面特征与金属间化合物的形成机理

对255℃时Sn-6.5Zn钎料/Cu基板界面反应及金属间化合物的形成与转化进行热力学计算与分析,并利用SEM、EDS、XRD研究分析255℃不同钎焊时间条件下钎料/Cu基板界面组织与IMC层形态特征。结果表明:Sn-6.5Zn钎料/Cu焊点界面紧靠Cu基板侧形成CuZn层;CuZn IMC有与钎料中的Zn原子继续反应生成Cu5Zn8 IMC的趋势;在相同钎焊温度条件下,不同钎焊时间对界面厚度影响不大;随钎焊时间延长,Sn-6.5Zn钎料/Cu基板焊点界面IMC层的平均厚度增大,界面粗糙度则由于不同钎焊时间IMC在液态钎料中生长与溶解的差异,呈现先增大而后降低到一个均衡值的变化趋势。     

La对Sn-Ag-Cu无铅钎料与铜钎焊接头金属间化合物的影响

研究微量稀土La在钎焊和时效过程中对Sn-3.0Ag-0.5Cu无铅钎料与铜基板的钎焊界面及钎料内部金属间化合物(IMC)的形成与生长行为的影响.结果表明:钎焊后钎焊界面形成连续的扇形Cu6Sn5化合物层,其厚度随La含量的增加而减小;在150℃时效100h后,连续的Cu3Sn化合物层在Cu6Sn5化合物层和铜基板之间析出,且Cu6Sn5层里嵌有Ag3Sn颗粒;界面金属间化合物总厚度随时效时间的延长而增厚,且在相同时效条件下随La含量的增加而减小;时效过程中金属间化合物生长动力学的时间系数(n)随着La含量的增加逐渐增大;钎焊后钎料内部Ag仍以共晶形式存在,时效后Ag3Sn颗粒沿钎料内部的共晶组织网络析出.     

钎焊时间对Sn-3.0Ag-0.5Cu/Cu钎焊接头界面化合物的影响

研究了不同钎焊时间下Sn-3.0Ag-0.5Cu/Cu焊点界面金属间化合物生长变化规律和剪切强度变化。结果表明:随着钎焊时间增加,界面化合物平均厚度逐渐增加,且生长的时间指数为0.4。钎焊60s内界面化合物的生长速率较大;随着钎焊时间的增加,钎焊接头的抗剪切强度先增加后降低,这与界面处脆硬相Cu6Sn5生长行为密切相关。     

SnCu钎料合金镀层钎焊连接机理及界面反应

通过在LD31铝合金表面电刷镀Ni,Cu后再沉积SnCu钎料合金镀层的钎焊实验,研究了钎料镀层的连接机理及界面反应,改进了可降低Ni层应力的电刷镀镀Ni液的配方,开发出适合镀层钎焊的SnCu钎料合金镀液,钎焊时钎料润湿为附着润湿,研究了在300℃钎焊时焊缝界面金属间化合物的生长规律,结果表明：焊缝中Cu-SnCu界面处生成了球状和棒状的Cu6Sn5金属间化合物;拉伸时焊缝主要沿着SnCu金属间化合物和富Sn相之间的界面断裂。     

超声波和电场共同作用下SnAgCuRE/Cu钎焊接头的时效特性

研究了时效对电场和超声振动共同作用下Sn2.5Ag0.7Cu0.1RE/Cu钎焊接头组织与性能的影响。结果表明:Sn2.5Ag0.7Cu0.1RE/Cu钎焊接头界面生成的IMC主要由靠近钎料合金一侧的Cu6Sn5相,而时效后界面靠近Cu一侧出现Cu3Sn。时效过程中,随着时效时间和时效温度的增加,Sn2.5Ag0.7Cu0.1RE/Cu界面区生长受扩散机制控制,IMC总厚度增加,力学性能下降。     

SnAgCu/Cu钎焊接头等温时效下组织性能分析

Sn3.0Ag0.5Cu/Cu钎焊接头在125,150,175℃三种温度下分别进行了36,72,216,360,720 h等温时效,对钎焊接头微观组织及力学性能在时效过程中的演变规律进行了研究.结果表明,界面金属间化合物(IMC)在横截面上呈细小锯齿状,随着时效温度升高及时间延长,界面IMC的尺寸不断增加,增长速度随时效温度升高而增加,随时效时间延长而减小.界面IMC齿数不断减少、齿径变大、齿高变长、齿距变宽.分析得出一种科学的表征界面IMC尺寸的方法.计算时效后界面IMC层等效厚度,发现界面IMC层的等效厚度与时效时间及温度之间具有一定的数学关系,同时可计算出界面IMC的生长激活能为88 kJ/mol.此外研究了时效对钎焊接头抗拉强度的影响,随时效时间增加接头抗拉强度先增大后减小,这主要与接头残余应力释放及界面IMC的演变有关.     

Sn-2.5Ag-0.7Cu-0.1RE/Cu钎焊界面区IMC及接头性能

采用扫描电镜和X射线衍射等检测手段,研究了钎焊工艺参数对Sn 2.5Ag 0.7Cu 0.1RE/Cu界面金属间化合物(IMC)长大及钎焊接头剪切强度的影响.结果表明,Sn 2.5Ag 0.7Cu 0.1RE/Cu钎焊界面区形成了波浪状Cu6Sn5金属间化合物(IMC).随钎焊时间延长、钎焊温度升高,界面波浪状Cu6Sn5相转变为较大尺寸的扇贝状,其厚度及界面粗糙度相应增大.当钎焊温度为270 ℃、钎焊时间为180 s时,Cu6Sn5相厚度较薄,为2.2 μm;界面光滑,其粗糙度为1.26 μm,接头剪切强度值最高.     

Ti90及其优化合金的组织与力学性能研究

研究了钎焊与时效过程中,在Sn0.7Ag0.5Cu(SAC0705)钎料与Cu基板和石墨烯Cu基板界面处金属间化合物(IMC)的形成与演变。采用加热平台制备焊接试样并在120℃时效600h。结果表明,界面金属间化合物在时效过程中增厚。SAC0705/Cu和SAC0705/G-Cu 2种焊接界面金属间化合物均为Cu6Sn5。当钎料中添加Ni元素后,Cu6Sn5化合物转变为(Cu,Ni)6Sn5。随着钎料中Ni元素含量的增大,2种基板上的界面金属间化合物厚度先增加后减小。此外,随着Ni含量增大,化合物生长速率降低。石墨烯Cu基板表面的石墨烯层起到扩散阻挡层效果,因此,石墨烯Cu板上的化合物厚度小于常规Cu基板,同时其界面化合物生长速率较低。     

外能辅助下Sn2.5Ag0.7Cu0.1RE0.05Ni/Cu钎焊接头组织与性能

采用SEM、EDS、XRD等方法研究了超声、电场外能辅助下Sn2.5Ag0.7Cu0.1RE0.05Ni/Cu钎焊接头的组织与性能。结果表明,借助于超声、超声-电场外能辅助能细化Sn2.5Ag0.7Cu0.1RE0.05Ni/Cu钎焊接头钎缝组织并使共晶组织比例增加,界面区金属间化合物(IMC)平均厚度、粗糙度和界面IMC颗粒尺寸减小。超声和电场外能辅助下Sn2.5Ag0.7Cu0.1RE0.05Ni/Cu钎焊接头强度与其界面IMC层粗糙度密切相关,超声的作用更为显著,在超声-电场外能辅助钎焊接头界面IMC层粗糙度降低中占主导作用,施加超声-电场外能辅助下钎焊接头剪切强度与传统钎焊相比提高24.1%;施加超声、超声-电场外能辅助使Sn2.5Ag0.7Cu0.1RE0.05Ni/Cu钎焊接头断裂途径由钎缝和界面IMC层组成的界面过渡区向钎缝侧迁移,呈界面(Cu,Ni)_6Sn_5 IMC解理和钎缝解理+韧窝的脆-韧混合型断裂机制,使接头剪切断口塑性区比例增加,从而提高接头剪切强度。     

The growth and roughness evolution of intermetallic compounds of Sn–Ag–Cu/Cu interface during soldering reaction

The growth behavior and roughness evolution of intermetallic compounds (IMCs) layer between Sn–3.5Ag, Sn–3.5Ag–0.7Cu, Sn–3.5Ag–1.7Cu and Sn–0.5Ag–4Cu lead-free solder alloys and Cu substrate are investigated during soldering under 250 °C. With the increase of Cu content in Sn–3.5Ag, Sn–3.5Ag–0.7Cu and Sn–3.5Ag–1.7Cu solders, the IMC thickness increases due to the decrease of the dissolution rate of the IMCs. The IMC thickness of Sn–0.5Ag–4Cu is quite thinner in a short soldering time. However, with the increase of soldering time, the IMCs layer grows quickly due to the precipitation effect of the Cu₆Sn₅ in the liquid solder. With the increase of soldering time, the roughness of all the IMC layers increases. The roughness of Sn–3.5Ag–0.7Cu and Sn–3.5Ag–1.7Cu interfaces is larger than that of Sn–3.5Ag while Sn–0.5Ag–4Cu/Cu interface has the smallest roughness value. It is believed that the small IMC roughness of Sn–3.5Ag/Cu interface is caused by the IMCs dissolution, and the large IMC/liquid solder interfacial energy maybe the reason for Sn–0.5Ag–4Cu/Cu interface obtaining the smallest IMC roughness.     

热-剪切循环条件下Sn-3．5Ag-0．5Cu／Cu（Ni）界面化合物生长行为研究

对热-剪切循环条件下Sn-3．5Ag-0．5Cu钎料在Cu和Ni界面上原子扩散和化合物的生长行为进行了研究。结果表明：再流焊后，在Sn-3．5Ag-0．5Cu／Ni界面上形成（CuxNi1-x）6Sn5化合物；热-剪切循环200周次后，（NixCu1-x）Sn3化合物在（CuxNi1-x）6Sn5化合物周围以片状快速长大；而Sn-3．5Ag-0．5Cu／Cu界面从钎焊到热-剪切循环720周次始终只存在Cu6Sn5金属化合物层。随着热-剪切循环周数的增加，（CuxNi1-x）6Sn5和Cu6Sn5化合物形态均从笋状向平面状生长。界面金属间化合物的厚度随循环周数的增加而增加，且生长基本遵循抛物线规律，说明Cu原子的扩散控制了（CuxNi1-x）6Sns和Cu6Sn5化合物的生长。     

微连接用Sn-2.5Ag-0.7Cu(0.1RE)钎料焊点界面Cu6Sn5的长大行为

利用XRD、SEM及EDAX研究了钎焊和时效过程中低银Sn-2.5Ag-0.7Cu(0.1RE)/Cu焊点界面区显微组织和Cu6Sn5金属间化合物的生长行为。结果表明,钎焊过程中焊点界面区Cu6Sn5金属间化合物的厚度是溶解和生长两方面共同作用的结果;随时效时间的增加,焊点界面区Cu6Sn5的形貌由扇贝状转变为层状,其长大动力学符合抛物线规律,由扩散机制控制;添加0.1%(质量分数,下同)的RE能有效减慢界面Cu6Sn5金属间化合物在钎焊及时效过程中的长大速度,改变焊点的断裂机制,提高其可靠性。     

Cu和Al箔扩散结合界面相生长行为研究

采用等离子活化烧结方法实现了Cu箔和Al箔的固相扩散结合,考察了673～773K温度范围内界面金属间化合物(IMCs)层的生成过程和生长动力学。结果表明:界面IMCs生成过程主要包括物理接触、IMCs形核、IMCs沿界面相连和IMCs层连续增厚4个阶段;界面主要由Al4Cu9、AlCu和Al2Cu层构成;各层厚度与反应时间的关系均符合抛物线规律,表明IMCs生长动力学由体扩散所控制;各层生长速率常数与反应温度之间满足Arrhenius关系,且整个IMCs界面层以及Al4Cu9、AlCu和Al2Cu各单层的生长激活能分别为80.78、89.79、84.63和71.12kJ/mol。     

Bismuth segregation enhances intermetallic compound growth in SnBi/Cu microelectronic interconnect

There was a sudden increase of intermetallic compound (IMC) Cu₆Sn₅ growth rate in the eutectic Sn58wt. %Bi/Cu joint during aging process. With aging time increasing, Bi accumulated at the Cu₃Sn/Cu interface and gradually induced the fracture mode of the joint to change from ductile to brittle one along this interface. Bi segregation enhanced IMC Cu₆Sn₅ growth by means of promoting the interfacial reaction at Cu₃Sn/Cu interface, which was concluded from IMCs (Cu₆Sn₅ and Cu₃Sn) growth behavior for pure Sn/Cu and Sn10wt. %Bi/Cu interconnects at the same temperature.     

Ni改性GNSs对SnAgCuRE/Cu钎焊接头热老化特性的影响

以Sn2.5Ag0.7Cu0.1RE0.05Ni无铅钎料合金为研究对象,基于石墨烯纳米片（GNS）独特的结构、优异的物理性能和力学性能,以其为复合钎料的增强相,开展基于Ni改性GNSs（Ni-GNSs）增强SnAgCuRE系复合钎料/Cu的钎焊和钎焊接头热老化试验,探讨Ni-GNSs对复合钎料组织及钎焊接头热老化失效断裂机制的影响。结果表明：Ni-GNSs的加入,抑制了复合钎料的线膨胀,产生晶格畸变,导致位错产生,金属间化合物（IMC）颗粒分布在位错线附近,与位错发生交互作用,阻碍位错运动,强化复合钎料,进而强化复合钎料接头。随着热老化时间延长,钎焊接头界面IMC层厚度增加,剪切强度降低;其中,添加0.05%（质量分数）GNSs的复合钎料接头剪切强度降幅最小,为8.9%,且热老化384 h后,其剪切强度仍高于Sn2.5Ag0.7Cu0.1RE0.05Ni/Cu合金接头热老化前的剪切强度。Ni-GNSs的加入,使复合钎料钎焊接头界面IMC的生长系数明显降低,有效缓解了复合钎料/Cu钎焊接头热老化过程中力学性能的降低,进而改变复合钎料/Cu钎焊接头的热老化失效断裂机制,最终影响接头的可靠性。Sn2.5Ag0.7Cu0.1RE0.05Ni/Cu钎焊接头的断裂位置由热老化前的钎缝区向钎缝/界面IMC移动,变为韧脆混合断裂;而添加0.05%（质量分数）GNSs复合钎料接头的断裂位置均在钎缝区,为韧性断裂,钎焊接头可靠性较高。     

Interfacial reactions between Sn–8Zn–3Bi–xAg lead-free solders and Cu substrate

The formation and the growth of the intermetallic compounds (IMCs) at the interface between the Sn–8Zn–3Bi–xAg (x = 0, 0.5, and 1 wt.%) lead-free solder alloys and Cu substrate soldered at 250 °C for different durations from 5 to 60 min were investigated. It was found that Cu₅Zn₈ and CuZn₅ formed at Sn–8Zn–3Bi/Cu interface, and Cu₅Zn₈ and AgZn₃ formed at the solder/Cu interface when the solder was added with Ag. The thickness of IMC layers in different solder/Cu systems increased with increasing the soldering time. And the growth of the IMCs was found to be mainly controlled by a diffusion mechanism. Additionally, the growth of the IMC layers decreased with increasing content of Ag in the soldering process.     

Early stages of intermetallic compound formation and growth during lead-free soldering

We investigate the early stages of the morphological evolution of intermetallic compounds (IMCs) during lead-free soldering involving liquid Sn-based solder and Cu substrate considering the heterogeneous nucleation of the IMCs. The simulation is performed through the multi-phase-field approach [20], [25]. Initially, the liquid Sn-based solder and the Cu substrate are considered to be at metastable local equilibrium. Nucleation at the solder/substrate interface is modeled by considering it to be a Poisson process. The phase-field simulation accounts for variations in grain boundary diffusion in the η phase and interface energies between the η phase and liquid solder, and uses these variations to investigate the multiplicity of soldering reactions, and make comparisons with previous work [23]. The simulations address the kinetics of the IMC growth during lead-free soldering under the effect of nucleation at an early stage, illustrating the variation in Cu substrate thickness, IMC thickness and number of grains that nucleate or disappear due to grain growth-induced coalescence.     

Experimental and computational study of the morphological evolution of intermetallic compound (Cu6Sn5) layers at the Cu/Sn interface under isothermal soldering conditions

Cu/Sn soldering alloys have emerged as a viable alternative to Pb-based solders, and thus have been extensively explored in the past decade, although the fine-scale behavior of the resulting intermetallic compounds (IMCs), particularly during the early stages of interface formation, is still a source of debate. In this work, the microstructural evolution of Cu₆Sn₅, in a Cu/Sn soldering reaction at 523 K, was experimentally investigated by dipping a single Cu sample into molten Sn at a near-constant speed, yielding a continuous set of time evolution samples. The thickness, coarsening and morphology evolution of the Cu₆Sn₅ layer is investigated through the use of scanning electron microscopy. The experimental results are also compared to phase-field simulations of the microstructural evolution of the Cu₆Sn₅ layer. The influence of model parameters on the kinetics and morphological evolution of the IMC layer was examined. In general, good qualitative agreement is found between experiments and simulations and for a limited parameter set there appears to be good quantitative agreement between the growth kinetics of the Cu₆Sn₅ layer, the grain boundary (GB) effect on grain coarsening, and the substrate/IMC interface roughness evolution. Furthermore, the parametric investigations of the model suggests that good agreement between experiments and simulations is achieved when the dominant transport mechanism for the reacting elements (Cu and Sn) is GB diffusion.