无铅钎料/Cu焊盘接头的界面反应

研究了无铅钎料Sn-3．8Ag-0．5Cu与Cu焊盘接头Cu-Sn界面金属间化合物的形成与长大机理。采用CALPHAD方法利用Thermo Calc软件进行了Sn-3．8Ag-0．5Cu／Cu合金体系亚稳相图计算,比较了界面处局部平衡时各相形成驱动力大小,预测了体系界面反应过程中的金属间化合物形成类型和反应通道;预测结果表明,界面金属间化合物有Cu6Sn5、Cu3Sn,第一析出相为Cu6Sn5;通过SEM和EDX分析,验证了预测的准确性。根据金属学固液界面的扩散与溶解规律,分析了界面金属间化合物的形成和长大特点。     

Sn-58Bi无Pb焊料与化学镀Ni-P层之间的界面反应

研究了Sn-58Bi共晶焊料与Cu的界面反应以及在Cu基体上化学镀Ni-P层的界面反应．焊接温度为180℃，焊接后时效温度范围为60-120℃，时间为5-30d．利用SEM，EDAX，XRD对反应产物进行了鉴定．结果表明，焊料与Cu的界面反应产物为Cu6Sn5，与化学镀Ni-P层的界面反应产物为Ni3Sn4，在Ni3Sn4与Ni-P层之间存在一层富P层．在同样条件下，Cu6Sn5的生长速度要快于Ni3Sn4的速度．化学镀Ni-P层中P含量较高时进一步抑制Ni／Sn界面反应生成Ni3Sn4的速度．界面金属间化合物层生长动力学符合x=(kt)^1/2关系，表明界面反应由扩散机制控制．由实验结果计算，Cu6sn5的表观激活能为90．87kJ／mol；Ni3Sn4的表观激活能则与化学镀Ni-P层中P含量有关，当镀层P含量为9％与16％(原子分数)时，其表观激活能分别是101．43kJ／mol与117．31kJ／mol．     

钎焊及其设备

1．0％Zn,Ni对Sn-3．5Ag／Cu界面反应及化合物生长的影响;银铜钛合金与立方氮化硼磨粒钎焊界面显微分层结构及形成机理;铝／钛异种合金激光熔钎焊接头界面特性;矩形片式电阻半导体激光钎焊无铅焊点的热循环试验     

钎焊及其设备

1．0％Zn,Ni对Sn-3．5Ag／Cu界面反应及化合物生长的影响;银铜钛合金与立方氮化硼磨粒钎焊界面显微分层结构及形成机理;铝／钛异种合金激光熔钎焊接头界面特性;矩形片式电阻半导体激光钎焊无铅焊点的热循环试验     

钎焊及其设备

CVD金刚石膜的钎焊界面反应层及显微结构；铝锂合金钎焊接头断口组织与性能；Sn-3Ag／Cu接头在钎焊和时效中IMC的生长和晶体取向分析；铜-铝合金（PU散热器钎焊技术研究；碳化硅质焊料连接氮化硅／碳化硅陶瓷的性能研究.     

老化对Sn-Ag-Cu焊料/Ni-P镀层界面结构和剪切强度的影响

对Sn-3．5Ag-0．7Cu／Ni—P界面上的焊点进行了150℃固相老化和250℃液相回流老化实验．两种条件下焊料体内和界面处金属间化合物的成分、长大速率及形貌均有较大差异．在液相回流条件下金属间化合物长大更快，对焊点的可靠性有较大的影响．延长固相老化时间，焊点内生成大尺寸的Ag3Sn相；高温液相回流有Ni3P层生成，降低焊点的焊接强度．     

1.0%Zn,Ni对Sn-3.5Ag/Cu界面反应及化合物生长的影响

在微电子互连结构中,反应界面化合物层的形貌及厚度是决定焊点可靠性的一个重要因素.通过向Sn-3.5Ag共晶钎料中添加第三元素,分别研究元素Zn和Nj对Sn-3.5Ag/Cu界面反应的影响.结果表明,对于Sn-3.5Ag/Cu界面,液态反应初始生成物为Cu6Sn5,在随后的热老化阶段形成Cu3Sn化合物层;Zn元素不影响界面的初始生成相及其厚度,但在150℃老化阶段,Cu3Sn化合物的形成受到抑制,取代的是非连续的Cu5Zn化合物层,并且,化合物层增厚速度减慢;然而,当添加1.0%(质量分数)的Ni元素后,界面初始生成相为(Cu,Ni)6Sn5,该化合物层厚度明显大于前者,老化阶段界面无其它相生成.     

微量Ag对Sn-0.7Cu-3Bi焊料微观组织及性能的影响

在Sn-0.7Cu-3Bi焊料的基础上,掺加不同比例的Ag元素,形成Sn-0.7Cu-3Bi-xAg合金,研究不同掺量的Ag对Sn-0.7Cu-3Bi焊料的熔化温度、润湿性及焊接接头的微观组织形貌的影响.结果表明:添加微量Ag能够降低焊料的熔点,但会导致增大其熔程；Ag掺量(wAg)为0.3％时,急剧降低了Sn-0.7Cu-3Bi焊料的润湿性,虽然后续随Ag掺量的继续增加,润湿性逐渐变好,但效果不理想；Ag掺量为0.3％时,焊接接头接触不良,界面化合物厚度极薄,后续随Ag掺量的继续增加,界面化合物厚度有所增厚,但当Ag掺量为0.7％时,界面化合物的晶体颗粒尺寸较大.     

Sn-3.5Ag-0.5Cu/Cu界面的显微结构

研究了热-剪切循环条件下Sn-3．5Ag-0．5Cu钎料／Cu界面的显微结构，分析了界面金属间化合物的生长行为，并与恒温时效后的Sn-3．5Ag-0．5Cu／Cu界面进行了对比。结果表明：恒温时效至100h，Sn-3．5Ag-0．5Cu／Cu界面上已形成Cu6Sn5和Cu3Sn两层金属间化合物；而热-剪切循环至720周Sn-3．5Ag-0．5Cu／Cu界面上只存在Cu6Sn5金属间化合物层，无Cu3Sn层生成，在界面近域的钎料内，颗粒状的Ag3Sn聚集长大成块状；在热-剪切循环和恒温时效过程中，界面金属间化合物的形态初始都为扇贝状，随着时效时间的延长逐渐趋于平缓，最终以层状形式生长。     

Ag-Cu-Sn-In中温焊膏的性能与初步应用试验

采用氮气雾化法将Ag-22．4Cu-15Sn-5In焊料制成粉体，利用丙烯酸酯类化合物为载体将其调配成膏状焊料。应用试验表明，所配制的新型焊膏易于涂布，焊接性能良好，焊后残渣少，无需再清洗。该新型焊膏能进行可伐与钨铜、可伐与陶瓷等材料的焊接，有着广阔的应用前景。钎焊界面分析发现，钎料主要是由富Ag相，少量Cu7In4相、Cu39Sn11相以及Cu3Sn相组成。在钎焊过程中，镍基板上的镍与钎料中的元素铜存在元素扩散。这对改善钎料与基体之间的结合状况是有益的。     

Cu颗粒增强的Sn-9Zn复合钎料/Cu钎焊接头界面反应

研究了长时间再流焊条件下,在粉状Sn-9Zn无铅钎料中加入Cu颗粒增强质点(复合钎料)对Sn-9Zn/Cu钎焊接头界面反应的影响.结果表明,在Sn-9Zn无铅钎料中加入Cu颗粒,可有效降低Sn-9Zn/Cu钎焊接头界面金属间化合物(IMC)的生长速度,从而减小界面IMC层的厚度,减少IMC层内的柯肯达尔(Kirkendall)缺陷;IMC层的厚度随再流焊时间的增加而增加,随Cu颗粒加入量的增加而减小.在现试验条件下,IMC层由Cu-Zn金属间化合物组成,未检测到Cu-Sn金属间化合物的存在.     

Sn-Ag-Cu and Sn-Cu solders: Interfacial reactions with platinum

The interfacial reaction and intermetallic formation at the interface between tin solders containing a small amount of copper with platinum were investigated in this study. Sn-0.7Cu and Sn-1.7Cu solders were reacted with platinum by dipping Pt/Ti/Si specimens into the molten solder at 260°C. Sn-3.8Ag-0.7Cu solder was reacted with platinum by reflowing solder paste on a Pt/Ti/Si substrate at 250°C. PtSn₄ intermetallic formed in all specimens while Cu₆Sn₅ interfacial intermetallic was not observed at the solder/platinum interfaces in any specimens. A parabolic relationship existed between the thickness of the Pt-Sn intermetallic and reaction time, which indicates the intermetallic formation in the solder/platinum interface is diffusion controlled. For more information, contact Young-Ho Kim, Hanyang University, Department of Materials Engineering, Seoul, 133-791, Korea; e-mail kimyh@hanyang.ac.kr.     

Interfacial reactions of liquid Sn and Sn-3.5Ag solders with Ag thick films

The interfacial reactions of liquid Sn and Sn-3.5Ag solders with Ag thick films are investigated in the temperature range from 250–325 °C, and the morphology of intermetallic compounds formed after such soldering reactions is observed. In kinetics analysis of the growths of intermetallic compounds, it was found that both Sn/Ag and Sn-3.5Ag/Ag reactions were interfacial-controlled, and the growth rates for both cases were similar. The rate of Ag dissolution into liquid solder attendant on the formation of interfacial intermetallic compounds after Sn/Ag reaction was about four times higher than that after Sn-3.5Ag/Ag reaction, as evidenced by experimental results.     

Understanding the Influence of Copper Nanoparticles on Thermal Characteristics and Microstructural Development of a Tin-Silver Solder

This paper presents and discusses issues relevant to solidification of a chosen lead-free solder, the eutectic Sn-3.5%Ag, and its composite counterparts. Direct temperature recordings for the no-clean solder paste during the simulated reflow process revealed a significant amount of undercooling to occur prior to the initiation of solidification of the eutectic Sn-3.5%Ag solder, which is 6.5 °C, and for the composite counterparts, it is dependent on the percentage of copper nanopowder. Temperature recordings revealed the same temperature level of 221 °C for both melting (from solid to liquid) and final solidification (after recalescence) of the Sn-3.5%Ag solder. Addition of copper nanoparticles was observed to have no appreciable influence on melting temperature of the composite solder. However, it does influence solidification of the composite solder. The addition of 0.5 wt.% copper nanoparticles lowered the solidification temperature to 219.5 °C, while addition of 1.0 wt.% copper nanoparticles lowered the solidification temperature to 217.5 °C, which is close to the melting point of the ternary eutectic Sn-Ag-Cu solder alloy, Sn-3.7Ag-0.9Cu. This indicates the copper nanoparticles are completely dissolved in the eutectic Sn-3.5%Ag solder and precipitate as the Cu₆Sn₅, which reinforces the eutectic solder. Optical microscopy observations revealed the addition of 1.0 wt.% of copper nanoparticles to the Sn-3.5%Ag solder results in the formation and presence of the intermetallic compound Cu₆Sn_5. These particles are polygonal in morphology and dispersed randomly through the solder matrix. Addition of microsized copper particles cannot completely dissolve in the eutectic solder and projects a sunflower morphology with the solid copper particle surrounded by the Cu₆Sn₅ intermetallic compound coupled with residual porosity present in the solder sample. Microhardness measurements revealed the addition of copper nanopowder to the eutectic Sn-3.5%Ag solder resulted in higher hardness.     

Pb-free solders for flip-chip interconnects

A variety of lead-free solder alloys were studied for use as flip-chip interconnects including Sn-3.5Ag, Sn-0.7Cu, Sn-3.8Ag-0.7Cu, and eutectic Sn-37Pb as a baseline. The reaction behavior and reliability of these solders were determined in a flip-chip configuration using a variety of under-bump metallurgies (TiW/Cu, electrolytic nickel, and electroless Ni-P/Au). The solder micro-structure and intermetallic reaction products and kinetics were determined. The Sn-0.7Cu solder has a large grain structure and the Sn-3.5Ag and Sn-3.8Ag-0.7Cu have a fine lamellar two-phase structure of tin and Ag₃Sn. The intermetallic compounds were similar for all the lead-free alloys. On Ni, Ni₃Sn₄ formed and on copper, Cu₆Sn₅Cu₃Sn formed. During reflow, the intermetallic growth rate was faster for the lead-free alloys, compared to eutectic tin-lead. In solidstate aging, however, the interfacial intermetallic compounds grew faster with the tinlead solder than for the lead-free alloys. The reliability tests performed included shear strength and thermomechanical fatigue. The lower strength Sn-0.7Cu alloy also had the best thermomechanical fatigue behavior. Failures occurred near the solder/intermetallic interface for all the alloys except Sn-0.7Cu, which deformed by grain sliding and failed in the center of the joint. Based on this study, the optimal solder alloy for flip-chip applications is identified as eutectic Sn-0.7Cu. Editor’s Note: A hypertext-enhanced version of this article can be found at www.tms.org/pubs/journals/JOM/0106/Frear-0106.html For more information, contact D.R. Frear, Interconnect Systems Laboratories, Motorola, Tempe, AZ 85284; (480) 413-6655; fax (480) 413-4511; e-mail darrel.frear@motorola.com.     

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。     

Effect of rare earth metal Ce addition to Sn-Ag solder on interfacial reactions with Cu substrate

The effect of adding a small amount of rare earth cerium (Ce) element to low Ag containing Sn-1wt%Ag Pb-free solder on its interfacial reactions with Cu substrate was investigated. The growth of intermetallic compounds (IMCs) between three Sn-1Ag-xCe solders with different Ce contents and a Cu substrate was studied and the results were compared to those obtained for the Ce-free Sn-1Ag/Cu systems. In the solid-state reactions of the Sn-1Ag(-xCe)/Cu solder joints, the two IMC layers, Cu₆Sn₅ and Cu₃Sn, grew as aging time increased. Compared to the Sn-1Ag/Cu joint, the growth of the Cu₆Sn₅ and Cu₃Sn layers was depressed for the Ce-containing Sn-1Ag-xCe/Cu joint. The addition of Ce to the Sn-Ag solder reduced the growth of the interfacial Cu-Sn IMCs and prevented the IMCs from spalling from the interface. The evenly-distributed Ce elements in the solder region blocked the diffusion of Sn atoms to the interface and retarded the growth of the interfacial IMC layer.     

Comparative Study on Solid-State and Metastable Liquid-State Aging for SAC305/Cu Joints

In order to study the in?uence of the physical state of solder on the interfacial reaction of dip-soldered Sn-3.0 Ag-0.5 Cu/Cu system, two kinds of experiments were designed, including:(1) solid-state aging between the solder and Cu substrate;(2)liquid-state aging between the metastable supercooled liquid-state solder and Cu substrate. The aging times were 30, 60,120 and 180 min, respectively, and the aging temperature was 8 ℃ lower than the melting point of the Sn-3.0 Ag-0.5 Cu(SAC305) alloy(217 ℃). The experimental data revealed that the physical state of the solder obviously affected the formation of the intermetallic compound(IMC), and resulted in the difference in the diffusion of atoms on the interface between the SAC305 solder and Cu substrate. The IMC interface after aging for 30 min presents unique characteristics compared with that of the sample after dip soldering. The IMC interface of solid-state aged SAC305/Cu couple is relatively planar, while the IMC interface under metastable supercooled liquid-state aging conditions presents scallop-like shape.     

Nd对Sn-3.8Ag-0.7Cu/Cu焊点高温可靠性的影响

通过研究150 ℃时效条件下Sn-3.8Ag-0.7Cu-0.05Nd/Cu焊点剪切力变化和界面微观结构演变,探讨稀土元素Nd对焊点高温可靠性的影响及其影响机制. 结果表明,不同时效时间后Sn-3.8Ag-0.7Cu-0.05Nd/Cu焊点剪切力明显高于Sn-3.8Ag-0.7Cu/Cu焊点,且时效过程中Sn-3.8Ag-0.7Cu-0.05Nd/Cu焊点剪切力的下降速率低于原焊点. 这是由于0.05%Nd可将界面原子扩散系数由1.88 × 10?10 cm2/h降低至1.10 × 10?10 cm2/h,即通过抑制界面金属间化合物的粗化来提高焊点的高温可靠性.     

热循环对Sn58Bi(纳米Ti)/Cu焊点界面与性能影响

为了改善Sn-58Bi低温钎料的性能,通过在Sn-58Bi低温钎料中添加质量分数为0.1%的纳米Ti颗粒制备了Sn-58Bi-0.1Ti纳米增强复合钎料。在本文中,研究了纳米Ti颗粒的添加对-55～125 _^oC热循环过程中Sn-58Bi/Cu焊点的界面金属间化合物(IMC)生长行为的影响。研究结果表明：回流焊后,在Sn-58Bi/Cu焊点和Sn-58Bi-0.1Ti/Cu焊点的界面处都形成一层扇贝状的Cu₆Sn₅ IMC层。在热循环300次后,在Cu₆Sn₅/Cu界面处形成了一层Cu₃Sn IMC。Sn-58Bi/Cu焊点和Sn-58Bi-0.1Ti/Cu焊点的IMC层厚度均和热循环时间的平方根呈线性关系。但是,Sn-58Bi-0.1Ti/Cu焊点的IMC层厚度明显低于Sn-58B/Cu焊点,这表明纳米Ti颗粒的添加能有效抑制热循环过程中界面IMC的过度生长。另外计算了这两种焊点的IMC层扩散系数,结果发现Sn-58Bi-0.1Ti/Cu焊点的IMC层扩散系数(整体IMC、Cu₆Sn₅和Cu₃Sn IMC)明显比Sn-58Bi/Cu焊点小,这在一定程度上解释了Ti纳米颗粒对界面IMC层的抑制作用。