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.     

超大面积芯片烧结技术研究

随着半导体大功率器件的发展,芯片的散热一直是制约功率器件发展的因素之一。而器件内部散热主要是通过芯片背面向外传导,芯片焊接工艺是直接影响器件散热好坏的关键因素之一,合金焊料的一个显著优点就是其导热性能好,因此在散热要求高的大功率器件中使用较为广泛(如Au80Sn20、Au99.4Sb0.6等),但由于合金焊料烧结后会产生较大的残余应力,在尺寸大于8 mm×8 mm的芯片上,烧结工艺应用较少。文章针对11.5 mm×11.5 mm超大面积芯片进行金锡合金烧结试验,经过对应力产生的原因进行分析,从材料、封装工艺等方面采取措施来降低缓释应力,并对封装产品进行可靠性考核验证。试验结果表明,没有芯片存在裂纹、碎裂现象,产品通过了可靠性验证。     

Au20Sn箔材焊料及其应用

使用单辊法制备Au20Sn箔材,通过XRD衍射仪测试其晶态结构和相组成;采用差热分析法(DTA)测试其熔化温度;应用环境扫描显微镜(ESEM)观察其常温下微观组织。对比了单辊法制备的金锡焊料和叠层法制备的金锡焊料焊接光纤接头和大功率LED固晶接头的显微结构。结果表明:单辊法工艺可以制备Au20Sn箔材,其物理性能和显微组织都与理论的Au20Sn焊料一致;单辊法制备的金锡焊料的焊接性能比叠层法制备的焊料好。     

激光器芯片烧结用AuSn薄膜焊料制造技术研究

共晶成分的金锡合金焊料AuSn20,具有较高的热导率、剪切强度、抗热疲劳性和抗腐蚀性,在高功率电子器件和光电子器件封装中应用广泛。本文在AlN陶瓷基板上,通过分层电镀Au/Sn/Au三层薄膜并合金化的方法,在AlN陶瓷表面制备了一种预制AuSn20合金焊料的基板。分析了焊料的成分及性能,结果满足国军标GJB 548B-2005 《微电子器件试验方法和程序》的剪切强度要求。用该基板封装激光二极管后达到设计功率,光功率效率为35%。     

覆Ag层对用于LD封装的In焊料性能的影响

In焊料由于其优越的可塑性以及优良的导电、导热特性,被广泛用于半导体激光器(LD)的封装。但是In焊料遇空气易氧化,尤其在焊接加热的过程中,氧化现象更加明显,因此一般当天制备当天使用。为防止氧化,可以在In焊料表面镀一层Ag或Au作为保护层,因为Ag成本较Au低,可作为首选的保护层。关于In-Ag合金性能的研究已有过相关报道,但关于In-Ag合金的表面形貌及Ag层厚度对内部In的影响的报道还很少。文章通过扫描电子显微镜、XRD对不同样品进行了表面和成分的分析,得到了关于Ag对内部焊料的影响以及不同冷却速率下焊料的表面形貌。     

真空炉金锡封焊

文章在介绍半导体金锡焊料封装工艺的基础上,重点对金锡焊料、炉温曲线设置等工艺技术问题进行了深入研究。基于大量的金锡焊料真空焊接封装实验及理论分析,研究了器件气密封装技术。讨论了封焊夹具、管帽镀层、合金状态、封接面表面、压块、焊料厚度以及加热程序对焊接质量的影响。密封后的产品在经过环境试验和机械试验考核后,封装气密性能很好地满足要求。并且结合应用背景证明了所采用的合金及封装工艺的可行性。     

大功率半导体激光器高可靠烧结技术研究

近几年大功率半导体激光器的应用领域越来越广,许多应用领域都要求半导体激光器能够高可靠性工作.工作焊接质量直接影响着大功率半导体激光器的可靠性,焊接缺陷会导致激光器迅速退化.目前国内普遍采用的铟焊料和锡铅焊料都是软焊料,焊层有形成晶须和热疲劳等可靠性问题.为提高烧结可靠性,采用了金锡焊料烧结激光器新技术.金锡焊料是硬焊料,焊接强度高,抗疲劳性好,对金层无浸蚀现象.通过实验研究掌握了金锡焊料的制备和烧结技术,并与铟焊料、锡铅焊料进行了对比实验.实验结果显示采用金锡焊料烧结激光器可获得更好的性能,是提高半导体激光器可靠性的有效途径.     

一种半导体探测器气密性封装结构和工艺优化

结构和工艺设计优化已经成为封装必不可少的步骤。随着探测器封装尺寸越来越小以及可靠性要求的不断提高,气密性封装结构向表面贴装、超薄型、芯片与封装体面积比更高的方向转变,封装结构和封装工艺的设计成为可靠性、成品率和成本的关键。骑跨式贴片半导体辐射探测器陶瓷封装中,存在芯片粘接衬底、密封环、引脚与HTCC陶瓷件钎焊处有Ag72Cu28焊料堆积、爬行的现象,以及芯片的Au80Sn20焊接层存在空洞大而又无法通过X射线照相或芯片粘接的超声检测来筛选剔除不合格的问题,分析原因并通过优化封装结构、改进封装工艺等解决封装的质量和可靠性。实际生产结果表明,结构优化、工艺改进有效地简化了外壳结构,减少了制造工序步骤,并提高了芯片烧结质量和成品率,降低了封装成本。     

塑料生物芯片的激光焊接封装系统研究

介绍了采用半导体激光器在塑料生物芯片焊接封装系统的应用 ,论述了塑料生物芯片焊接封装原理和工艺 ,提出了基于 80 8nm半导体激光器的塑料焊接封装系统的设计方法 ,分析了焊接封装的参数选择 ,实现了部分塑料之间的成功焊接     

电镜原位电子束辐照下Au85 Sn15纳米线的动态熔化过程（英文）

金锡合金焊料由于其良好的性能逐渐成为一种可能替代锡铅焊料的无铅焊料,并且利用电子束辐照的焊接方式,一维金锡纳米线已经成功用于TiO_2纳米线的焊接,这为钛基半导体氧化物纳米材料的焊接提供了实验经验。然而,金锡焊料在电子束焊接时的熔化机制和动态过程的研究还很贫乏。在本文中,我们通过电化学沉积的方法制备了一维Au₈₅ Sn₁₅合金纳米焊料,并详细地研究了在透射电镜中的电子束辐照下,其形貌,晶体结构,化学元素分布的演化过程,并进一步探究了电子束辐照熔化纳米焊料的机理。研究发现,在电子束辐照下,一维Au₈₅ Sn₁₅合金纳米焊料的形貌由线状熔化为液滴状;其晶体结构由AuSn和Au_5 Sn为主,少量Au,β-Sn,SnO_2的混合相转化为单一的Au_5 Sn相;其化学元素在电子束辐照下发生质量损失,该过程既有物理相变又有化学相变。在电子束辐照传递的能量作用下,原子的流动或扩散迁移和重新排列是形成新的结合层的动力学机制。该工作不仅为应用纳米焊料进行电子束焊接提供了实验依据,而且为电子束辐照熔化金锡纳米合金纳米焊料的内在机制的研究提供了宝贵经验。     

微波GaAs功率芯片的低空洞率真空焊接技术研究

文章选用80Au20Sn焊料对微波GaAs功率芯片的焊接技术进行了较为系统深入的研究,通过对共晶焊接设备与真空烧结设备分别对焊接时气体保护、焊片大小、真空工艺过程的施加和夹具设计等因素进行了试验分析。结果表明,以上参数对微波GaAs功率芯片焊接均有显著的影响,在保护气体流量为1.5L·min^-1的氮气保护下,通过施加适当的夹具静压力和金锡焊料熔化时的抽真空应用,AuSn焊料能够充分和快速润湿,实现较高的焊接质量。X射线检测结果表明,微波GaAs功率芯片焊接具有较低的空洞率,焊透率高达90％以上,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。     

Characterization of 63Sn37Pb and 80Au2OSn solder sealed opticalfiber feedthroughs subjected to repetitive thermal cycling

A highly accurate prediction of hermeticity lifetime is made for eutectic 63Sn37Pb and 80Au20Sn alloy solder sealed optical fiber-Kovar ^TM nosetube feedthroughs subjected to repetitive thermal cycling. Thermal fatigue fracture of the Sn-Pb solder/Kovar^TM interface develops when cracks, initially generated from creep deformation of the solder, propagate gradually through the junction in the axial direction. A nonlinear axisymmetric finite element analysis of the 63Sn37Pb fiber feedthrough seal is performed using a thermo-elastic creep constitutive equation, and solder joint fatigue based on accumulated strain energy associated with solder creep imposed by temperature cycling is analyzed. Additionally, thermal effective stress and plastic strain is studied for alternative 80Au20Sn solder by the finite element method with results indicating significant increase in useful life as compared to 63Sn37Pb. SEM/EDX metallurgical analysis of the solder/Ni-Au plated Kovar^TM nosetube interface indicates that AuSn₄ intermetallic formed during soldering with 63Sn37Pb also contributes to joint weakening, whereas no brittle intermetallic is observed for 80Au20Sn. Hermetic carbon coated optical fibers metallized with Ni,P-Ni underplate and electrolytic Au overplating exhibit correspondingly similar metallurgy at the solder/fiber interface. Combined hermeticity testing and metallurgical analysis carried out on 63Sn37Pb and 80Au20Sn alloy solder sealed optical fiber feedthroughs after repetitive temperature cycling between -65 and +150°C, and -40 and +125°C validated the analytical approach     

Modified Face-Down Bonding of Ridge-Waveguide Lasers Using Hard Solder

A modified face-down bonding technique of ridge-waveguide laser diodes (LDs) using 80Au20Sn solder has been performed. For ease of manufacturability, a bonding window with good bonding integrity and improved optical performance was determined. Metallographical investigation showed that the solder joint comprised of a layer of delta phase compound near the solder/heatsink interface, a layer of (Au,Ni)Sn intermetallic compound (IMC) at the solder/heatsink interface, and zeta' phase Au/Sn compound at the center of the solder joint. The delta phase shifted to the interfaces after reflow was postulated by its lower surface tension than zeta' phase Au/Sn compound. Good bonding integrity was observed with LD residues still adhering onto the bond pad after die shear testing. Scanning electron microscopy (SEM)/energy dispersive X-ray (EDX) analyses of the fracture surface showed that the fracture occurred within the LD, at the GaAs/SiN interface. LDs bonded with this modified bonding process achieved an optical improvement of 2.5-3X compared to the unbonded LDs due to its good thermal management. These bonded LDs further exhibited good long-term reliability with no significant degradation in optical performance and no significant microstructure evolution in the solder joint after 500 thermal cycling test.     

Mounting of high power laser diodes on boron nitride heat sinksusing an optimized Au/Sn metallurgy

High power diode lasers have become more and more important to industrial and medical applications. In contrast to low power applications, long cavity lasers or laser bars are used in this field and mounting quality influences considerably laser performance and life time. In this paper we focus on the solder metallurgy and stress-induced laser behavior after mounting. The laser chips have been bonded fluxless epi-side down on translucent cubic boron nitride (T-cBN) using Au/Sn solder. The laser behavior has been tested with different chip metallizations preserving the eutectic solder composition or forming the Au rich ζ-phase during reflow. The resulting additional stress in the lasing region has been independently indicated by polarization measurements of the emitted light. A metallization scheme has been developed which forms the highly melting ζ-phase during soldering within a wide process window. This procedure yields better results then using eutectic Au/Sn which has a higher hardness than the ζ-phase. Laser diodes up to a cavity length of 2000 μm and an aperture of 200 μm have successfully been mounted on T-cBN. State of the art laser data, excellent thermal stability, high yield and reliability have been obtained     

Development of lead-free wave soldering process

Lead-free wave soldering was studied in this work using a 95.5Sn/3.8Ag/0.7Cu alloy. A process DOE was developed, with three variables (solder bath temperature, conveyor speed, and soldering atmosphere), using a dual wave system. Four no-clean flux systems, including alcohol- and water-based types, were included in the evaluation. A specially designed "Lead-Free Solder Test Vehicle", which has various types of components, was used in the experiments. Both organic solderability preservative (OSP) and electroless nickel/immersion gold (Ni/Au, or ENIG) surface finishes were studied. Soldering performance (bridging, wetting and hole filling) was used as the responses for the DOE. In addition, dross formation was measured at different solder bath temperatures and atmospheres. Dross formation with Sn/Ag/Cu bath was compared to that with eutectic Sn/Pb bath. Regarding the connector-type component, a pad design giving the best soldering performance was evaluated based on the DOE results. Finally, a confirmation run with the optimum flux and process parameters was carried out using the Sn/Ag/Cu solder, and a comparative run was made with the Sn/Pb solder alloy and a no-clean flux used in production. The soldering results between the two runs indicate that with optimum flux and process parameters, it is possible to achieve acceptable process performance with the Sn/Ag/Cu alloy.     

Fluxless Bonding of Large Silicon Chips to Ceramic Packages Using Electroplated Eutectic Au/Sn/Au Structures

A fluxless process of bonding large silicon chips to ceramic packages has been developed using a Au-Sn eutectic solder. The solder was initially electroplated in the form of a Au/Sn/Au multilayer structure on a ceramic package and reflowed at 430°C for 10 min to achieve a uniform eutectic 80Au-20Sn composition. A 9 mm × 9 mm silicon chip deposited with Cr/Au dual layers was then bonded to the ceramic package at 320°C for 3 min. The reflow and bonding processes were performed in a 50-mTorr vacuum to suppress oxidation. Therefore, no flux was used. Even without any flux, high-quality joints were produced. Microstructure and composition of the joints were studied using scanning electron microscopy with energy-dispersive x-ray spectro- scopy. Scanning acoustic microscopy was used to verify the joint quality over the entire bonding area. To employ the x-ray diffraction method, samples were made by reflowing the Au/Sn/Au structure plated on a package. This was followed by a bonding process, without a Si chip, so that x-rays could scan the solder surface. Joints exhibited a typical eutectic structure and consisted of (Au,Ni)Sn and (Au,Ni)₅Sn phases. This novel fluxless bonding method can be applied to packaging of a variety of devices on ceramic packages. Its fluxless nature is particularly valuable for packaging devices that cannot be exposed to flux such as sensors, optical devices, medical devices, and laser diodes.     

Microstructure of eutectic 80Au/20Sn solder joint in laser diode package

Laser diodes (LD) are usually bonded onto heat sinks for the purposes of heat dissipation, mechanical support and electrical interconnect. In this study, energy dispersive X-ray analysis (EDX) and electron backscatter diffraction (EBSD) are employed to investigate the microstructure evolution of 80Au/20Sn solder joint in LD package. During reflow, Pt-Sn and (Au, Ni)Sn IMCs were formed at the respective LD/solder and solder/heatsink interfaces, while δ, β and ζ′ phases of Au/Sn intermetallics were found in the solder joint. The Au-rich β and ζ′ phases in the solder joint limit the growth of interfacial IMCs. Chip shear testing showed that the failure occurred within the LD, with partial brittle fracture at the GaAs substrate and partial interfacial delamination at the GaAs/SiN interface. The strong solder bond can be attributed to the high mechanical strength of 80Au/20Sn solder, which provides improved stability for high temperature applications.