用于大功率半导体激光器的Ag-In焊料研究

大功率半导体激光器的封装对焊料选择极其重要,因为焊料导热或导电性差,激光器工作产生的大量热量使焊料焊接失效,激光器也会遭到损坏。为此,文中研究了软焊料In及其保护层Ag作为一种焊料组合,通过真空蒸发镀膜仪蒸发蒸镀Ag-In与Ag-In-Ag-In两种薄膜方式。根据微结构知识及扩散动力学与热动力学相结合讨论了Ag-In焊料产生间隙的原因,通过XRD衍射仪了解到薄膜间界面化合物AgIn2的生成可能导致表面微结构的改变,结果表明Ag层对In层易被氧化的性质起到了保护作用,多层的Ag-In焊料层可抑制大量间隙的产生,提高器件工作可靠性及稳定性。     

烧结温度对AuSn焊料薄膜及封装激光器性能的影响

采用不同温度对Au80Sn20共晶合金焊料进行烧结实验,研究了AuSn焊料薄膜在烧结后的形貌、物相组成以及对封装激光器的性能影响等.焊料在烧结后形成ξ相Au5Sn和δ相AuSn两种金属间化合物,随着烧结温度的上升,两相晶粒均明显长大,而ξ相Au5Sn趋向于形成枝晶.较低温度下烧结的焊料表面粗糙度较高,不利于激光器管芯的贴装.高温过烧焊料薄膜的导电导热性能有少许提升,对封装激光器管芯的功率没有明显影响,但焊料薄膜中残余应力较高,使激射波长有所蓝移.该结果将为AuSn焊料的烧结参数优化和硬焊料封装激光器的性能分析提供参考和指导.     

感应自加热重熔无铅焊料凸台的剪切失效模式

通过两次高频感应重熔制备了Cu焊盘上S n3．5Ag焊料和Sn3．0Ag0．5Cu焊料凸台,并进行了120℃下的老化试验以及老化试件的剪切强度试验,分析了不同老化时间下两种无铅焊料凸台的剪切断裂模式。焊料凸台的剪切载荷-位移曲线的特征以及对焊料凸台剪切断口的扫描电镜形貌分析结果表明,不同老化时间下无铅焊料凸台的剪切断裂表现为塑性、韧性和脆性三种断裂模式。对凸台焊料合金的组织以及界面观察结果表明,随老化时间不断生长的脆性金属间化合物层以及焊料组织粗大是致使断裂失效模式转变的根本原因。     

微波功率器件中AuGe合金焊接界面特征

在微观尺度上,焊点的可靠性取决于焊料同焊盘之间界面反应生成的界面金属间化合物(IMC)的结构。通过金锗合金焊点的界面反应及微观结构随环境的变化表征了焊点的可靠性,研究了AuGe合金焊料与不同金层厚度的Ni/Au焊盘共晶焊接后其界面特征,同时总结了AuGe合金焊料在Cu和Ni等常见焊盘上的焊接润湿性及其焊接界面特征。切片分析结果显示,在共晶焊接后,厚金样品焊接界面冷却时焊料层析出富Au相形成不规则焊接结合层,Au层厚度减薄50%～60%;薄金样品的Au层全部消失,并在界面处形成很薄的一层富Ni的NiGe化合物。实验结果显示,厚Au层样品未出现Ni向焊接层扩散的现象和NiGe化合物的生成,厚Au层起到了阻挡层作用;薄金样品时,Ni通过互扩散缓慢与Ge形成NiGe化合物,在长期使用中焊接层会通过元素扩散等形式演变,使整个焊接层转变为含氧化层、富P层、NiGe层和AuCuGe合金层等多层结构的IMC,降低了焊点强度,严重影响焊接层可靠性。这说明IMC在焊接过程中主要以界面化学反应方式形成,服役过程中主要以元素扩散方式演变。     

微波电路中In/Au合金焊点的失效分析

本文针对微波电路元件焊接脱落问题,分析了In/Au合金焊点的微观结构及成分, 研究了In/Au芯片焊接的失效模式.找出了焊点脱落的主要原因:温度控制不当引起焊点的过热吃金或焊料的氧化引起的浸润不良,导致焊点的结合强度不够,致使焊点脱落.根据分析提出了严格控制温度及焊接时使用氮气保护的改进意见,较好的解决了In/Au合金焊接脱落问题,支撑了微波电路的生产工艺.     

Sn—Bi无铅焊料的研究

通过总结传统Sn-Pb焊料的特点和研制无铅焊料的条件,综述Sn-Bi无铅焊料低熔点等优点以及脆性大、易偏析的缺点,分析添加In,Ag,AI,Sb等微量合金元素对Sn-Bi无铅焊料微观组织及性能的影响,提出了此合金系焊料的抗蠕变性、导电性、润湿性、拉伸性能等尚待完善的性能及可采用合金化、开发新型焊剂等新方法使Sn-Bi焊料成为理想的无铅焊料,为无铅焊料的进一步研究提供一定的参考.     

高功率二极管激光器Au80Sn20焊料焊接实验研究

半导体激光器封装工艺过程对于激光器的输出特性、寿命等性能有重要影响,其中焊料的选择和焊接工艺是最关键的因素。本文采用磁控溅射的方法,在 WCu 热沉上制备了Au80Sn20合金焊料,取代了传统的In焊料,并对焊接工艺进行了改进。国外沉积的和我们制备的Au80Sn20合金焊料焊接DL芯片后的性能参数很接近。充分说明双靶分层溅射镀膜可以实现二极管激光器的封装要求,从而为优化半导体激光器制备工艺和提高半导体激光器的性能奠定基础。     

两步合金法制作p-GaN高反电极

利用两步合金法获得了能与p-GaN形成良好欧姆接触的高反射电极.电极的构成采用透明电极 高反射金属方案,厚的Ag层或Al层覆盖在合金后的Ni/Au上以提高电极的反射率,以Pt和Au作为覆盖层,可有效地防止Ag的氧化和团聚,短时间的热处理有助于Ag基电极反射率的提高.可靠性测试表明Ag基电极的稳定性较好,对于Al基电极,热处理后反射镜上出现暗斑,导致其反射率的下降.最终获得了波长在460nm处反射率为74%的Ag基高反射电极.     

微量元素添加对多元Sn-Bi系焊料合金组织与性能的影响

传统焊料合金由于熔点温度高,不能满足部分有机基板、温度敏感器件以及3D封装等多层封装形式的低温封装要求。以Sn-Bi合金为基体,通过添加微量Ag、Cu、Co和Ni元素形成新型多元合金,对多元合金的熔化性能、润湿性能、微观组织和力学性能进行研究。结果表明:微量元素的添加(质量分数0~1%)对多元Sn-Bi系合金的固相线温度影响很小,降低了SnBi57AgCuCo合金的液相线温度和熔程;添加微量元素降低了合金的表面能,提高了润湿性;多元Sn-Bi系合金的微观组织由SnBi共晶组织、β-Sn相和块状富Bi相组成,微量元素的添加细化了β-Sn相中的Bi相颗粒。组织中的金属间化合物颗粒提高了多元Sn-Bi系合金抗拉强度和延伸率;断口形貌表明合金主要沿Bi相晶界断裂,Bi相的细化可改善焊料合金的力学性能。     

基于InPb合金的非制冷焦平面探测器窗口低温焊接工艺研究

研究了采用纯度为99.9%的In70Pb30合金作为焊料片的低温焊接技术,分析了焊接时候的影响因素:焊料片的影响、升温速率、焊接温度、真空度,通过采用甲酸对焊料片预处理去除氧化层,在215℃、5×10~(-7) torr的真空环境下进行了焊接,焊接后的样品采用X-ray、拉力测试系统、检漏仪测试了样品的孔洞率、焊接强度、漏率,结果表明:焊接后焊接区域合金均匀、无缝隙、孔洞率少、剪切力高、气密性好,能够满足非制冷焦平面的窗口封接的气密性要求。     

A fluxless flip-chip bonding for VCSEL arrays using silver-coated indium solder bumps

Alloys of lead-tin system are the most common solder alloys used today. However, there are environmental and health issues concerning the toxicity of lead present in these lead-tin solder alloys. Also, the flux residue removal is mandatory and leads to environmental threats. More importantly, the use of flux may contaminate the optically active surface by organic residue leftover, and a conventional cleaning method may not be effective for optoelectronic assemblies. Therefore, it is necessary to look for fluxless soldering processes for soldering optoelectronic systems. In the present study, we have conducted low-temperature flip-chip bonding of vertical-cavity surface-emitting laser (VCSEL) arrays on a glass substrate that provides propagation paths of laser beams and also supports a polymeric waveguide. Considering both the die shear test and the spreading test, the appropriate bonding temperature and pressure using indium solder bump were found to be about 150/spl deg/C/500 gf. The fracture occured between the indium solder bump and the VCSEL chip pad during the die shear test. It is inferred that both the low bonding temperature and the oxide layer which is formed on the surface of the indium solder prevented the bump from interacting with the chip pad. We expect the thin silver layer coating on the indium bump to protect the inner indium solder from oxidation and to decrease the melting temperature of the indium solder. Thus, we try coating a thin silver layer onto the indium surface. An eutectic reaction occurs at 97 wt.% of In with an eutectic point of 144/spl deg/C and the outer silver layer interacts with indium to form a AgIn/sub 2/ compound layer due to the high interdiffusion coefficient. As a result, the thin silver layer coated on the solder bump is very effective to enhance the adhesion strength between the indium bump and the VCSEL chip pads by decreasing the melting temperature of the indium solder bump locally.     

Sn-8Zn无铅钎料性能的研究

研究了不同微量合金元素(Bi、Ag)对Sn-8Zn无铅钎料高温抗氧化性能及接头剪切强度的影响,采用氧化质量增加△m值的方法,在高温下观察钎料表面氧化膜形状和颜色的变化并对氧化膜进行X射线衍射分析,探讨了钎料的高温抗氧化性能的机理,通过对钎料的金相显微组织观察和对热处理后钎焊接头的剪切强度试验,分析了提高接头剪切强度的原因.试验结果表明:在Sn-8Zn钎料中加入适量的合金元素(Bi、Ag)均可以改善和提高钎料的高温抗氧化性能和接头的剪切强度.     

Metallurgical reactions in composite 90Pb10Sn/lead-free solder joints and their effect on reliability of LTCC/PWB assembly

Use of 90Pb10Sn solder as a noncollapsible sphere material with 95.5Sn 4Ag0.5Cu and SnInAgCu lead-free solders is investigated. Practical reflow conditions led to strong Pb dissolution into liquid solder, resulting in >20 at.% Pb content in the original lead-free solders. The failure mechanism of the test joints is solder cracking due to thermal fatigue, but the characteristic lifetime of 90Pb10Sn/SnInAgCu joints is almost double that of 90Pb10Sn/95.5Sn4Ag0.5Cu in a thermal cycling test (TCT) over the temperature range from −40°C to 125°C. It is predicted that this is mainly a consequence of the better fatigue resistance of the SnPbInAgCu alloy compared with the SnPbAgCu alloy. Indium accelerates the growth of the intermetallic compound (IMC) layer at the low temperature co-fired ceramic (LTCC) metallization/solder interface and causes coarsening of IMC particles during the TCT, but these phenomena do not have a major effect on the creep/fatigue endurance of the test joints.     

合金焊料盖板选择与质量控制

在平行缝焊、储能焊、玻璃熔封、激光焊、合金焊料熔封等密封工艺中,合金焊料密封是高可靠密封的优选工艺。文章针对合金焊料密封工艺中常遇到的密封强度、密封内部气氛、焊缝及盖板耐腐蚀、薄形封装易短路等问题,介绍了通过合金焊料盖板的选择,从而控制密封强度、密封内部气氛、耐蚀性能和电性能等的质量。     

Interfacial reactions in the pb-free composite solders with indium layers

A Pb-free composite solder is prepared with a Pb-free solder substrate and a plated-indium layer. The indium layer melts during the soldering process, wets the substrates, and forms a sound solder joint. Since the melting temperature of indium is 156.6°C, lower than that of the eutectic Sn-Pb, which is at 183°C, the soldering process can be carried out at a temperature lower than that of the conventional soldering process. Composite solder joints with three different Pb-free solders, Sn, Sn-3.5 wt.% Ag, and Sn-3.5 wt.% Ag-0.5 wt.% Cu, and two substrates, Ni and Cu, are prepared. The interfaces between the indium layer, Pb-free solder, and Ni and Cu substrate are examined. A good solder joint is formed after a 2-min reflow at 170°C. A very thick reaction zone at the indium/Pb-free solder interface and a thin reaction layer at the indium/substrate interface are observed.     

VL020回流炉中半导体激光器芯片In焊接研究

利用VL020真空烧结炉,选用In焊料对半导体激光器芯片的焊接技术进行较为深入的研究,分别对焊接时气体保护、焊接前期芯片、热沉的处理、真空工艺过程压力的施加、夹具设计和烧结工艺曲线等因素进行实验分析。结果表明,以上参数对半导体激光器芯片的焊接均有显著的影响,在N2/H2体积分数为95%/5%气体的保护下,通过对夹具施加适当的静压力,In焊料与Au能够充分和快速润湿,实现较高的焊接质量。蔡司显微镜检测结果表明,采用焊接技术可以使半导体激光器芯片具有较低的空洞率,高达90%以上的焊透率,其焊接过程主要通过夹具装配完成,人为影响因素少,成品率高,并适用于小批量生产。     

电子封装用银合金线性能的研究

研究了不同钯(Pd)含量银合金线的电阻率、铝挤出、可靠性及横截面的情况,并分析了Pd抑制银离子迁移的原理。结果表明,银合金线中加入Pd后,Pd的含量越高,线材的FAB硬度越大,铝挤出越多,Pd有助于提高合金线的可靠性,同时Pd的质量分数到3%以上时其可靠性更好。Pd能够抑制银离子迁移的原因是表面形成了一个PdO层,PdO富集在表面阻碍银离子扩散及迁移。银合金线的Ag-Al焊球界面主要形成Ag2Al及Ag3Al,Ag2Al比Ag3Al具有更高的抗腐蚀能力。     

Intermetallic Reaction of Indium and Silver in an Electroplating Process

The reaction of indium (In) and silver (Ag) during the electroplating process of indium over a thick silver layer was investigated. It was found that the plated In atoms react with Ag to form AgIn₂ intermetallic compounds at room temperature. Indium is commonly used in the electronics industry to bond delicate devices due to its low yield strength and low melting temperature. In this study, copper (Cu) substrates were electroplated with a 60-μm-thick Ag layer, followed by electroplating an In layer with a thickness of 5 μm or 10 μm, at room temperature. To investigate the chemical reaction between In and Ag, the microstructure and composition on the surface and the cross section of samples were observed by scanning electron microscopy (SEM) with energy-dispersive x-ray spectroscopy (EDX). The x-ray diffraction method (XRD) was also employed for phase identification. It was clear that indium atoms reacted with underlying Ag to form AgIn₂ during the plating process. After the sample was stored at room temperature in air for 1 day, AgIn₂ grew to 5 μm in thickness. With longer storage time, AgIn₂ continued to grow until all indium atoms were consumed. The indium layer, thus, disappeared and could barely be detected by XRD. Jong S. Kim now with Applied Materials.