电子组装中助焊剂的选择（续完）

助焊剂是电子组装技术中最重要的材料之一,其通过去除材料表面氧化膜及污染物等,保证钎料和母材之间很好的润湿,形成良好焊点.介绍了助焊剂的作用与组成、分类与性能要求以及涂覆方式和工艺评定,有助于实际生产中助焊剂的选择与使用.     

电子组装中助焊剂的选择 (续一)

助焊剂是电子组装技术中最重要的材料之一,其通过去除材料表面氧化膜及污染物等,保证钎料和母材之间很好的润湿,形成良好焊点。介绍了助焊剂的作用与组成、分类与性能要求以及涂覆方式和工艺评定,有助于实际生产中助焊剂的选择与使用。     

Cookson推出助焊剂选择服务

为了帮助电路板组装商在一定的应用中选择合适的助焊剂，Cookson电子组装材料公司推出在线互动服务：ALPHA波峰焊助焊剂选择工具。选择工具将根据用户要求的参数选择助焊剂。[第一段]     

绿色电子制造用水基助焊剂的研究

水基助焊剂是绿色电子制造的一种重要材料,是传统溶剂型助焊剂的替代品。本文简述了水基助焊剂的研究背景、研究方向以及对绿色电子产业的促进作用等。     

电子设备焊接用的助焊剂(其动态和存在问题)

在以电子工业为主的所有工业领域里,广泛采用的焊接技术中,助焊剂是最重要的材料之一,这是不言而喻的。谁都知道助焊剂的好坏,不仅直接影响焊接质量,而且对焊接效率也有重大的影响。除此以外,对于接合部份的机械可靠性,各种电气性能的可靠性也有显著影响。尽管它是重要的材料,但是关于助焊剂的基本知识还没有普及。对助焊剂一般的性质、成份,作用等还不为人所知。这在近代工业中焊接占有的重要性来看是很     

不使用CFC的SMT和PTH焊接流程和工艺——PCB组装的免洗和有机水溶性助焊剂及焊锡膏

国际环境计划（ＵＮＥＰ）１９９０年修改了蒙特利尔公约，要求在２０００年以前停止氟氯碳化合物（ＣＦＣ）的生产。因此，电子工业正在急切寻找不需用ＣＦＣ溶剂的替代清洗材料和助焊剂。经过电子工业在生产中评价后，低固态“免洗”助焊剂和有机水溶性助焊剂成为主流。对于这些类型的助焊剂，必须了解助焊剂的化学性质、焊接性、信赖性（可靠性）以及对于焊接过程的考虑，来决定对于某一焊接流程所能接受的助焊剂的类型     

不使用CFC的SMT和PTH焊流程和工艺：PCB组装的免洗和有机水溶？…

国际环境计划署（ＵＮＥＰ）１９９０年修改了蒙特利尔公约，要求在２０００年以前停止氟氯碳化合物（ＣＦＣ）的生产。因此，电子工业正在急切找不需用ＣＦＣ溶剂的替代清洗材料和助焊剂。经过电子工业在生产中评价后，低固态“免洗”助焊剂和有机水溶性助焊剂成为主流。对于这些类型的助焊剂，必须了解助焊剂的化学性质、焊接性、信赖性（可靠性）以及对于焊接过程的考虑，来决定对于某一焊接流程所能接受的助焊剂的类型。     

不使用CFC的SMT和PTH焊接流程和工艺：PCB组装的免洗和有机水溶性助…

国际环境计划１９９０年个性了蒙特利尔公约，要求在２０００年以前停止氟氯碳化合物的生产。因此，电子工业正在急切寻找不需要用ＣＦＣ溶剂的替代清洗材料和助焊剂，经过电子工业在生产中评价后，低固成“免洗”助焊剂和有机溶性助焊剂成为主流。     

一种醇基低固含量免清洗助焊剂的研制

通过无铅焊料的焊点铺展及润湿力实验考察了活性剂对助焊剂润湿性能的影响,并据此研制出了一种以乙醇为溶剂、以有机酸和有机胺为活性剂并使用复合表面活性剂的免清洗助焊剂.结果表明:使用复合表面活性剂的助焊剂的润湿效果要好于使用单一表面活性剂的助焊剂.其中,以使用Op-4与壬基酚聚氧乙烯醚质量比为8:1的复合表面活性剂的助焊剂的...     

国外工艺文献导读

20060101无铅波峰焊接中的焊剂喷涂—SanjuArora,Stanley Soderstrom.Circuits Assembly,2005,16(9):36~39(英文)为了在使用喷涂助焊剂进行无铅波峰焊的过程中获得良好的焊点,需要为喷涂应用专门开发助焊剂,而且需要能够在所需地方上喷涂助焊剂的高效喷涂装置。助焊剂气化时应会产生细雾,从焊接表面去除氧化膜。喷涂助焊剂系统需能够重复、均匀并完整地在所在暴露在熔化焊料中的表面喷涂助焊剂。助焊剂喷涂取决于助焊剂流率、横移速度和间距,而且这些参数应加以优化,以便在波峰焊过程中只需使用最少的助焊剂获得良好焊点。20060102无铅工…     

Experimental Wetting Dynamics Study of Eutectic and Lead-Free Solders With Various Fluxes, Isothermal Conditions, and Bond Pad Metallizations

Demands on solder bump interconnects have increased in modern electronics. This is characterized by high density, small size, and fine-pitch devices. In solder bump interconnects, solder wetting onto bond pads is the key factor that determines the interconnect process yield and the solder joint reliability. Solder wetting involves various physical phenomena such as surface tension imbalance, viscous dissipation, molecular kinetic motion, chemical reaction, and diffusion. In this paper, an experimental study on solder wetting dynamics will be presented. The effects of solder reflow process parameters and bonding materials will be discussed, as they relate to the physics of solder wetting and ultimately the interconnect process yield and solder joint reliability. The experimental setup consists of a high-speed image acquisition system and a temperature chamber which were used to measure the time dependent behavior of molten solder spheres onto bond pads under an isothermal condition. The solder materials investigated were eutectic tin–lead solder and lead-free 95.5Sn–4.0Ag–0.5Cu solder. The wetting dynamics of the solder materials were investigated on pure Cu bond pads and Cu/Ni/Au bond pads, with several different flux systems, at different environmental temperatures and with various solder sphere sizes. The experimental observations indicate that the wetting dynamics clearly depend on temperature, solder materials, and substrate metallization but do not depend significantly on the flux system or the solder sphere size.     

Ethylene glycol ether free solder paste development

There are growing concerns in the electronics industry for not only finding alternatives to lead but also other potentially hazardous materials as well. This paper summarizes the development of ethylene glycol ether (EGE)-free solder flux for the formulation of lead-free solder pastes. Replacing the toxic components in the flux was only the first challenge, the criteria of commercially proven pastes also had to be met. Both commercial and in-house solder paste formulations were evaluated for printability, reflow, wetting, flux residue removal, and solder void characteristics. Two critical issues, solder bump boids and flux residue removal, were identified and associated with the high temperature reflow of Pb-free pastes. These issues were not effectively improved by the existing commercial EGE-free solder pastes. New solder paste formulations were developed utilizing alternative chemistry than those found in traditional solder paste fluxes. These pastes, some, of which are also water soluble, reduced void frequency and size by more than 4x as compared to vendors' pastes. Solder bump height uniformity of 135 4 m within each die was consistently achieved. Thermal-mechanical reliability tests were performed on various lead-free solder alloys using the new flux formulations. The reliability of flip chip assembled DCA on organic boards with both OSP/Cu and Cu/Ni/au pad metallizations were comparable to eutectic Sn63Pb37 bumped assemblies using commerical pastes.     

Influence of halogen-free compound and lead-free solder paste on on-board reliability of green CSP (chip scale package)

In the past few years, many studies have reported on the formula of solder metal alloy materials. This paper discusses the influence of organic materials characters, the decomposing rate of flux in lead-free solder paste and coefficients of thermal expansion (CTE) of halogen-free mold compounds during the on-board reliability test, and the failure mechanism in both 63Sn/37Pb and Sn–3.5Ag–0.5Cu lead-free solder balls was reported.The thermal decomposing behavior of flux in the solder paste induced voids in solder joints was examined by thermo-gravimetric analysis (TGA) and X-ray perspective, respectively. On-board temperature cycle test (TCT) reliability failed specimens were sectioned and analyzed by the optical microscope (OM) and X-ray. The evolutions of package warpage change of two kinds of potential halogen-free compounds during the TCT reliability process were monitored by specially designed thermal mechanic analysis (TMA) experiments.The experimental results show that higher IR-reflow peak temperature induced voids forming in the solder joints and then failure mode change from interface between intermetallic and solder to cracks cut across the big voids during TCT test, worse TCT reliability performance ensued. Moreover, according to on-board reliability testing data show that the compound with larger package warpage change generated larger cumulate plastic work in solder joint that caused early failure during TCT process.     

Fluxless Wafer Bonding in Vacuum Using Electroplated Sn–Ag Layers

A wafer-to-wafer bonding process using Sn-Ag solder without any flux is successfully developed. This fluxless or flux-free feature makes void-free and uniform bonding layers possible. This is in contrast to the fluxing process employed in nearly all soldering processes adapted in the electronic industry. With the use of flux, the flux or flux residues are easily trapped in the solder joint, resulting in voids and uneven solder layers. This is particularly true if the bonding area is large, such as the entire wafer. Thus, void-free wafer bonding using solders has never been reported. It is thus clear that the key to achieve void-free wafer soldering is to eliminate flux completely. The new fluxless process is performed in a vacuum furnace built in house to inhibit solder oxidation. To prevent oxidation during solder manufacturing, a thin Ag capping layer is plated over the Sn layer right after the Sn layer is plated over an entire 2-in silicon wafer having Cr/Au under bump metallurgy (UBM). This outer Ag layer is critical in preventing the inner Sn layer from oxidation when the wafer is exposed to air. The Si wafer with Cr/Au/Sn/Ag structure is bonded with another Si wafer with Cr/Au at 240degC in the vacuum furnace. To evaluate the joint quality and study the microstructure and composition, scanning acoustic microscopy (SAM), scanning electron microscopy (SEM), and energy dispersive X-ray spectroscopy (EDX) are used. A solder joint with only 1% void area is accomplished. The initial success of this process illustrates that it is indeed possible to bond entire wafers together with a thin metallic joint of high quality. This fluxless bonding technique can be extended to bonding wafers of different materials for new device and packaging applications.     

A study of electromigration in 3-D flip Chip Solder joint using numerical Simulation of heat flux and current density

This paper applies an analogy between heat flow and current flow to examine the current density distribution in a solder interconnect, which has a direct relationship with the atomic flux movement. From a three-dimensional heat conduction analysis, we discover that the heat flux distribution in the solder bump is a strong function of the direction of heat flow. If the heat flow turns 90/spl deg/ when it leaves the solder bump, the high heat flux region will also turn 90/spl deg/. From a cross-sectional view of the mean heat flux, the high heat flux (or current flux) region in the solder moves from the top of the under-bump-metallurgy region to the lower right corner, and the right side of the solder has the highest flux density. This result correlates well with the experimental data where the measured atomic flux in the left side of the solder is less than in the right side. Two other cases with 0 and 180/spl deg/ heat flows also illustrate the difference in heat flux distribution. This suggests that the current density distribution in the solder changes as the direction of the current flow changes.     

焊膏配用焊剂的研制

详细介绍了一种焊膏配用焊剂的研制过程，主要介绍焊剂体系的各种组份及其对焊剂和烛地膏性能的影响。     

新型焊接技术——免清洗焊剂和无铅焊锡膏

鉴于全球电子制造业正向着绿色生产的方向发展,美国、日本、欧洲等一些国家制定了专项法规,保护人居环境。为此,本文重点介绍了绿色焊接材料——免清洗焊剂和无铅焊锡膏的发展历程及其主要性能、特点以及存在的问题。阐述了国内外免清洗焊剂和无铅焊锡膏的研究现状及其在电子组装技术中的应用前景。     

无铅转化给波峰焊工艺所带来的问题研究

无铅焊料的应用使得波峰焊设备问题更加突出,其中主要的问题是设备的腐蚀及材料的寿命.无铅焊料和助焊剂的特性决定了无铅波峰焊设备在结构和材料选用上有很大不同.无铅钎料的成分配比不同于有铅钎料,因此在无铅钎焊时,其工艺流程、工艺参数也有所改变.从焊接温度、波峰高度、浸锡时间、冷却系统、传输系统等方面分析了无铅波峰焊的工艺要求...     

绿色电子制造及绿色电子封装材料

阐述了绿色电子制造(包括电子封装)概念起源、定义以及基本内涵和范畴,并从电子封装用互连材料、被连接材料和封装后清洗过程这三个方面全面阐述了绿色电子封装的主要内容,重点评述了目前绿色电子封装材料(包括无铅钎料、钎剂、焊膏和导电胶等)的研究现状和面临的问题.最后,展望了绿色电子制造及绿色电子封装材料的未来发展趋势.