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。     

200℃等温时效下SAC305/Co-5％P焊点的界面组织及断裂模式演变

目的研究BGA封装的SAC305/Co-5%P焊点在200℃等温时效下的界面反应。方法制备SAC305/Co-5%P的BGA焊点,200℃等温时效0, 200, 400, 600, 1000 h,采用场发射扫描电镜(配EDS)观察不同时效时间下SAC305/Co-5%P焊点界面的IMC形貌与断口特征,采用焊点接合强度测试仪测试相应的剪切强度变化。结果时效1000 h时,在钎料/Co Sn3的IMC层界面处生成(Cu, Co)_6Sn_5,界面CoSn3的IMC之间的通道得到填充,界面形貌变得平整。随着时效时间的增加,焊点的剪切强度先增后降,位于Sn层断口的断裂模式由韧性断裂向韧脆混合型断裂转变。结论随着时效时间的增加,界面IMC层厚度不断增加,界面IMC形貌发生改变。     

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.     

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。     

纳米Ni 颗粒对焊锡膏的界面IMC 影响

目的研究纳米Ni对SnAg0.3Cu0.7无铅焊锡膏的焊点界面IMC影响。方法采用在助焊剂中添加纳米Ni颗粒,制备出纳米Ni颗粒增强的SnAg0.3Cu0.7焊锡膏,分析纳米Ni在150℃时效中对IMC的影响。结果在150℃时效中界面IMC的厚度随着时效时间延长而增大,形貌变成平缓层状;添加Ni质量分数为0.025%时,对界面IMC几乎无影响,当添加质量分数为0.05%和0.1%的纳米Ni能促进IMC的生长,但抑制Cu3Sn层的生长。结论通过添加纳米Ni颗粒,在150℃时效中可促进IMC的生长,抑制Cu3Sn层的生长。     

回流冷却与等温时效过程中Sn-35Bi-1Ag/Ni-P/Cu焊点组织演变

通过回流焊接方法,采用水、炉两种冷却方式分别制备了Sn-35Bi-1Ag/Ni-P/Cu快、慢冷钎焊接头。利用等温时效法对两种焊点界面IMCs层的生长动力学进行研究。采用SEM和EDS对界面层的微观结构和物相组成进行表征。结果表明:快冷条件的钎焊界面为(Ni,Cu)3Sn4+Ni3P的复合结构;慢冷条件下界面结构为(Ni,Cu)3Sn4+Ni3P+(Cu,Ni)6Sn5。等温时效过程中Ni-P层逐渐消耗,(Ni,Cu)3Sn4生长变慢,(Cu,Ni)6Sn5生长遵循时间的平方根动力学,界面IMCs的生长表现为扩散机制控制。两种焊点界面层最终均演化为(Cu,Ni)6Sn5+(Ni,Cu)3Sn4+(Cu,Ni)6Sn5的复合结构。钎焊时效中慢冷焊点IMCs层厚度均大于同等条件的快冷IMCs层,慢冷时界面层IMCs生长速率为4.670×10-18 m2/s,快冷时为3.816×10-18 m2/s,表明钎焊冷却速率影响钎焊及服役过程中焊点的老化行为。     

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。     

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。     

回流次数对无铅焊点组织演变及可靠性的影响

目的研究不同回流次数对焊点形貌以及组织演变的影响,并通过力学性能来表征不同回流次数下焊点的可靠性。方法利用置球法将Sn3Ag0.5Cu小球置于Cu基板表面,随后在回流焊机中形成焊点,并进行不同次数回流焊接得到所需焊点,横截镶样打磨腐蚀后,利用光学显微镜、扫描电子显微镜进行显微组织观察,并用推拉试验机进行剪切测试。结果在焊点反应过程中,由于熔融焊料中析出的过饱和Cu和Sn会在焊料部分形成中空的Cu6Sn5管状物和片状的Sn基体,但随着反应的持续,这些物质逐渐消失。在IMC层的形成过程中,伴随着大量Cu6Sn5颗粒的产生,随着反应的持续,颗粒数量逐渐减少,IMC层厚度逐渐增加,但增加速度减缓。结论在IMC层的生长过程中,大块IMC会吞噬Cu6Sn5小颗粒来增加自身体积,从而抑制小颗粒的产生,最终减缓自身的生长。此外随着回流次数的增加,焊点由韧性断裂逐渐转变为韧脆性混合断裂,对焊点可靠性的降低具有一定影响。     

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。     

Interfacial reaction and mechanical reliability of eutectic Sn–0·7Cu/immersion Ag-plated Cu solder joint

Abstract

In this study, the interfacial reaction and joint reliability of immersion Ag-plated Cu substrate with the Sn–0·7Cu (wt-%) ball–grid array (BGA) solder was investigated. During reflow, the Ag plating layer was dissolved completely into the molten Sn–Cu solder and some of the Cu layer was also dissolved into the molten solder. The dissolved Ag and Cu were precipitated as Ag₃Sn and Cu₆Sn₅ intermetallic compounds (IMCs) in the solder matrix. Upon reflow, the Sn–Cu solder exhibits an off-eutectic reaction to produce the eutectic phase and precipitate (Cu₆Sn₅ and Ag₃Sn). The Cu–Sn IMC layer was formed at the solder/Cu interface after reflow, and the IMC layer grew during aging treatment. During the shear tests, the failure mode switched from a bulk-related failure to an interface-related failure. After aging for 250 h, the joint failed partially at the solder/Cu₆Sn₅ interface. The brittle fracture was linked to the formation of thick Cu–Sn IMC layer.     

时效处理对Sn-Bi系无铅焊料的影响研究

为解决Sn-Bi焊料在焊接时容易产生凝固偏析、降低焊点力学性能的问题,采用对焊点进行时效处理的方法来消除Bi的粗化结晶,从而增强焊料的机械性能.研究表明,焊点在125℃时效处理16 h,粗大块状的Bi全部消融,呈颗粒状均匀分布,焊料中的Sn与焊盘上的Cu生成一层厚度约为3μm的Cu6Sn5金属间化合物,使焊点的剪切强度由40 MPa升高到54 MPa.研究还发现,时效处理后的焊点在100℃下长时间放置,微观组织不再发生变化,说明时效处理提高了焊料基体的抗热性能,因此,可以将125℃/16 h的时效处理作为表面贴装生产工艺流程的一道必要工序,使Sn-Bi焊料真正满足实用要求.     

Suppression effect of Cu and Ag on Cu3Sn layer in solder joints

Cu₃Sn intermetallic compound (IMC) layer is usually formed in solder joints. Since the formation of Cu₃Sn could induce large volume shrinkage, and further cause a lot of reliability issues, many works focused on suppressing the formation or growth of the Cu₃Sn layer. This work explored that Cu and Ag alloying elements also have benefit in suppressing the Cu₃Sn growth during isothermal aging stage. The Cu₆Sn₅ IMC layer seems to be much stable in the Sn/Cu solder joint during aged at 150 and 180 °C, its thickness changed little, while the Cu₃Sn IMC layer grew much quickly. After about 300 h, the thickness of Cu₃Sn layer exceeds that of Cu₆Sn₅ layer. For the Sn-3.5Ag/Cu and Sn-0.7Cu/Cu solder joints, the thickness of Cu₃Sn layer is near half of that of Cu₆Sn₅ layer. According to the relation between interface location and aging time, the reaction generated at the Cu₆Sn₅/Cu₃Sn interface, which is governed by atom fluxes, controls the growth of Cu₃Sn IMC layer. Since Ag and Cu alloying elements suppress the coarsening of Cu₆Sn₅ IMC grains, the diffusion paths for Cu atoms toward the solder are more for Ag or Cu containing solder joints. Therefore, the growth of the Cu₃Sn layer by consuming Cu₆Sn₅ layer is slower in the SnAg/Cu and SnCu/Cu solder joints than that in the Sn/Cu joints.     

感应加热重熔无铅钎料凸台的界面反应及剪切性能

感应自发热重熔（ISHR）技术在电子互连的应用中具有明显的三维选择性加热和快速加热等优点．该方法能够很好地解决由于无铅钎料的应用引起的日益严重的诸多问题，如球栅阵列中各钎料球受热不均匀和芯片基板与钎料球同时受热等．为此，采用ISHR进行了无铅钎料Sn3．5Ag在Au／Ni／Cu焊盘上的重熔实验、高温老化实验以及凸台剪切实验．由实验结果可知钎料凸台可以提供足够的剪切强度．文中讨论了界面反应和金属间化合物的演化．在老化期间界面处生长了连续的Ni3Sn4金属间化合物层，同时在钎料体内部生成了分散的（Aux，Ni1-x）Sn4化合物．金属间化合物的生长速度与老化时间的平方根成正比。由此可以判断金属间化合物的生长是一种扩散控制过程．     

Effect of Bismuth on Intermetallic Compound Growth in Lead Free Solder/Cu Microelectronic Interconnect

The intermetallic compound (IMC) growth kinetics in pure Sn/Cu and Sn10 wt%Bi/Cu solder joints was studied, respectively, after they were aged at 160-210°C for different time. It was found that the total IMC in Sn10 wt%Bi/Cu joint developed faster than it did in pure Sn/Cu solder joint, when they were aged at the same temperature. And the activation energy Qa for total IMC in Sn10 wt%Bi/Cu joint was lower than that for pure Sn/Cu interconnect. The IMC growth process was discussed. The IMC Cu6Sn5 was enhanced in compensation of reduced IMC Cu3Sn growth. The work reveals that Bi element containing in lead free solder alloys with 10 wt% can enhance IMC growth in lead free solder/Cu joint during service.     

Co颗粒含量对SnBi/Cu接头微观组织与性能的影响EI北大核心CSCD

采用扫描电镜(SEM)观察Sn35Bi-x Co(x=0%,0.3%,0.7%,1.0%,1.2%,1.5%,质量分数,下同)复合钎料/Cu接头的微观组织,结合能谱(EDS)和XRD分析,研究接头组织差异。利用万能试验机测试接头力学性能,研究Co颗粒含量对SnBi/Cu接头组织及性能的影响机制。结果表明:随Co颗粒含量增加,Sn35Bi-Co复合钎料的润湿性呈现先增大后降低的趋势,当Co颗粒含量为0.7%时,润湿性最佳;在凝固阶段,向Sn35Bi/Cu接头中加入适量的Co颗粒后,能有效细化焊缝组织,界面IMC层更为平坦,焊缝中Co原子置换界面Cu_(6)Sn_(5)层中Cu原子,生成(Cu,Co)_(6)Sn_(5)固溶体,对界面IMC层具有固溶强化作用;Sn35Bi-Co/Cu接头的抗剪强度随Co颗粒含量增加先增大后降低,当Co颗粒含量为0.7%时,获得最大值54.09 MPa。     

Relation between Kirkendall voids and intermetallic compound layers in the SnAg/Cu solder joints

Several different kinds of intermetallic compound (IMC) layers were fabricated through adding trace elements into the Sn-3.5Ag solder, to investigate the relationship between the Kirkendall void (KV) and the IMC layers. The results show that a considerable amount of KVs were observed at the Cu₃Sn/Cu interface in the Sn-3.5Ag/Cu joint after isothermal aging. A proper amount of Zn (0.5 wt%) and Ge (0.1 and 0.3 wt%) were found to effectively suppress the formation of the Cu₃Sn layer, and no obvious KVs were observed at the Cu₆Sn₅/Cu interface, while more Zn induced the formation of the Cu₆Sn₅ plus Cu–Zn mixed IMC layer, and voids (not KVs) were observed at the Cu₆Sn₅/Cu–Zn interface. (Cu,Ni)₆Sn₅ IMC layer replaced the initial Cu₆Sn₅ at the SnAg-Ni/Cu joints, likewise, the Cu₃Sn was suppressed at the thermal aging stage. Moreover, voids were found at the IMC/solder interface, while not at the IMC/Cu. Therefore, the formation of KVs is greatly determined by the characteristic of the IMC layer, this is consistent with the previous reports. On other hand, the KV can be suppressed by controlling the interfacial phase through adding trace elements into the solder.     

三价铈离子掺杂氯化钾的光致发光性能

采用水热蒸发法制备了KCl∶Ce3+荧光粉。测量并分析了材料在室温下的真空紫外激发光谱及相应的发射光谱。结果表明激发谱显示6个峰,峰位分别为149、194、206、219、233和251nm。其中149nm的激发峰是基质吸收引起的;194、206、219、233和251nm是Ce3+离子的4f→5d跃迁引起的。发射峰显示双峰结构,峰位分别是311和326nm。此峰对应于Ce3+离子的5d→4f(2F5/2,2F7/2)跃迁。