铝真空针焊—预处理的影响

1、引言随着散热器的不断铝化,铝的硬钎焊也取得了发展。现在使用钎剂的浸渍钎焊,炉焊与无钎剂钎焊技术都被采用。虽然钎剂可取得良好的流动性,但还存在残余钎剂的去除,钎剂清洗不净而造成的母材的腐蚀,污水排水管道及夹具的损坏等问题。近年来,无钎剂钎焊的研究得到了发展。真空钎焊与有钎剂钎焊一样,可以说,母材及焊缝表面存在着氧化膜还原和清除的强度决定了钎焊的性质。     

铜与铝软钎焊技术的研究现状

综述了近年来铜与铝软钎焊在钎焊方法、钎料及钎剂三个方面的技术发展现状,指出铜铝软钎焊的技术优势以及铜与铝软钎焊技术应用前景广阔。     

真空／控制气氛无钎剂激光软钎焊系统的研制

结合激光软钎焊技术的特点，研制了真空／控制气氛无钎剂激光软钎焊系统，以便利用激光软钎焊的优点，进行真空／控制气氛下激光非接触加热的无钎剂技术研究。     

铝波导钎焊QF型氟化物钎剂的研究

铝波导生产中目前广泛采用201类型氯化物钎剂料402火焰钎焊。由于氯化物钎剂钎渣的强烈吸潮性,致使铝波导钎焊接头产生翻浆、长白毛、烂缝、鼓包等腐蚀现象,造成铝波导加工生产及存放使用中因腐蚀而报废。本文对QF型氟化物钎剂从组成、配制、工艺性能、对母材的腐蚀性能、使用性能等方面进行了系统试验研究指出:QF型氟化物钎剂不吸潮,去膜能力强,钎焊接头耐蚀性好,钎缝致密性好,钎渣易于去除,适用于普通炉中钎焊、惰性气体保护炉钎焊及气体火焰钎焊等,采用QF型钎剂能显著提高铝波导钎焊接头耐蚀性,为解决目前铝波导钎焊生产中的腐蚀问题提供了有效的途径。     

铝的无钎剂氩气保护钎焊工艺研究

目前,气保护下无钎剂普通铝板钎焊已有应用,但由于钎焊接头往往难以形成良好的外形(钎焊圆角),应用范围受到限制。本文为此试图利用接触反应和镁的作用,实现接头良好成型,为普通型无钎剂气保护铝钎焊探索新途径。     

氧化膜厚度对铝真空钎焊性能的影响

一、引言铝表面有一层致密而稳定的氧化膜,尽管这种氧化膜只有几个 nm(数十(?)),但它却明显地影响着钎焊性能。因此,铝钎焊时去除氧化膜是极为重要的。在一般的钎焊中,使用氯化物和氟化物钎剂,具有破坏和去除氧化膜的作用。目前,工业上使用的真空钎焊,是在钎料里添加镁来代替钎剂的活性,起着破除氧化膜的作用。可是,有的报告认为这种钎剂起不到破除氧化膜的作用,钎焊性能会随着氧化膜增厚而降低。     

H701型铝钎剂的试制

前言铝波导的火焰钎焊和炉中钎焊,目前较广泛使用的是仿苏34A型铝钎剂,用Al—6Si—28Cu钎料。但由于这种钎料脆性大,抗腐蚀性能较差,所以北大同我厂共同研制了129A、1712B等钎剂[1],和Al—Si—Be钎料[6]。此钎料克服了34A钎料、钎剂的某些缺点,钎料的韧性好,钎剂的流动性好,焊缝表面光滑,易清洗。但由于氯化物钎剂本身的物理化学性质所决定,钎剂易吸潮失效,残留物有吸湿性,放久后有腐蚀斑     

铜与铝软钎焊技术的研究现状

铝铜接头一般采用压焊、扩散焊、超声波焊、镀覆过渡层气体保护焊等焊接方法,由于设备复杂,生产成本高,生产周期长,限制了这些方法的使用.近几年,铜铝的直接软钎焊成为研究的热点.综述了近年来铜与铝软钎焊在钎焊方法、钎料及钎剂三个方面的技术发展现状.指出铜铝软钎焊的技术优势,铜与铝软钎焊技术应用前景广阔.     

铝波导真空钎焊

前言近年来,国外对铝及其合金的真空钎焊进行了多方面的研究,其目的是以真空钎焊代替老的钎剂钎焊和盐浴钎焊。铝及其合金的真空钎焊比钎剂钎焊和盐浴钎焊具有明显的优点:第一,无毒和无污染;第二,不需焊后清洗,节省人力物力,且不会造成焊后腐蚀;第三,变形量小,不需焊后修正。这些突出的优点对焊后无法清洗和无法修正的高精度铝波导是非常必要的。所以,铝波导采用真空钎焊工艺是一个合理方案。另外,     

加热速度和炉中气氛对无腐蚀铝钎剂性能的影响

无腐蚀钎剂(non—corrosiveflux)是近两年引起广大焊接工作者关切的铝钎焊的钎剂。本文从加热速度和炉中气氛对无腐蚀钎剂的影响方面进行了一些初步的研究和探讨。从而定性地提出了一些减少钎剂失效的方法。     

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.     

Study of fluxless soldering using formic acid vapor

This paper presents a systematic study of the use of formic acid vapor fluxless soldering with eutectic Pb/Sn solder. The study focused on the solder joint self-aligning process and the final alignment accuracy. The main effect considered was the formic acid vapor concentration. In addition, other effects of solder joint height and background vibration were studied. The self-alignment characteristics of the fluxless soldering process was as good as those using liquid flux at 220°C. 2 μm alignment accuracy could be achieved within 10 s. The most important parameter was the formic acid vapor concentration in the reflow chamber. The effective concentration window was found to be greater than 0.7% in volume     

A fluxless process of producing tin-rich gold-tin joints in air

A soldering process performed in ambient air without the use of any flux is reported. We believe that this is the first time fluxless soldering process is successfully done in air without prior fluorine treatment. The fluxless process is implemented using Au-Sn binary system. It is based on Au-Sn multilayer design that is substantially tin-rich, namely, with 95 at.% Sn (91.8 wt.% Sn) and 5 at.% Au (8.2 wt.% Au). Over the past 15 years, we have developed numerous fluxless bonding processes. These processes require environments such as H/sub 2/ or N/sub 2/ during the bonding process to inhibit solder oxidation. This requirement is not compatible with the pick-and-place bonding machines widely employed in the industry. Thus, fluxless processing in air has been our lifelong endeavor. After many attempts, we finally achieved some initial success. The bonding process is carried out at 225/spl deg/C. The resulting joints are nearly void-free as confirmed by scanning acoustic microscopy (SAM). To study the microstructure and composition of the samples, scanning electron microscopy (SEM) with energy dispersive X-ray (EDX) spectroscopy was performed on the joint cross-section. The results show that the joint is composed of AuSn/sub 4/ intermetallic grains embedded in a Sn matrix. Re-melting temperatures of the solder joints were measured to range from 214/spl deg/C to 220/spl deg/C, which are consistent with data on the Au-Sn phase diagram.     

Fluxless Soldering of Copper Substrates Using Self-Assembled Monolayers for Preservation

Self-assembled monolayers (SAMs) of octadecanethiol have been used as a preservative to enable fluxless soldering of copper substrates. The SAMs were deposited onto copper surfaces that had previously been etched to remove any existing oxide layers and wetting balance testing under an inert atmosphere was used to measure their fluxless solderability as a function of storage time and environment. It was found that SAM coated samples could be stored in air at room temperature for a short period of time before they became unwettable as a result of oxidation, however this storage time could be greatly increased by keeping them at low temperature. X-ray photoelectron spectroscopy was used to monitor the level of oxidation within the materials, which was found to correlate with the fluxless solderability. The SAM is thought to present a barrier to the penetration of oxygen to the copper surface, but at the same time can be readily displaced by heat and molten solder.     

大功率激光二极管无助焊剂烧焊技术

烧焊质量对大功率激光二极管的可靠性及寿命影响很大.为获得良好的烧焊质量通常在烧焊过程中使用助焊剂,但是助焊剂残留物会因腐蚀作用对激光二极管的性能及寿命产生不利影响.对蚁酸气体保护下的激光二极管无助焊剂烧焊技术进行了研究,介绍了几种去除焊料表面氧化层的方法,重点对蚁酸气体保护的烧焊进行了原理分析,并结合实际经验给出了合适的工艺曲线,利用此曲线烧焊出一定数量的样品,与氢气保护烧焊的器件进行了相关参数比较,证实了蚁酸保护烧焊在焊料的浸润性、器件的热阻及剪切力方面具有明显优势.     

Selective bonding and encapsulation for wafer-level vacuum packaging of MEMS and related micro systems

A laser-assisted bonding technique is demonstrated for low temperature region selective processing. A continuous wave carbon dioxide (CO₂) laser (λ=10.6 μm) is used for solder (Pb37/Sn63) bonding of metallized silicon substrates (chips or wafers) for MEMS applications. Laser-assisted selective heating of silicon led to the reflow of an electroplated, or screen-printed, intermediate solder layer which produced silicon–solder–silicon joints. The bonding process was performed on fixtures in a vacuum chamber at an air pressure of 10⁻³ Torr to achieve fluxless soldering and vacuum encapsulation. The bonding temperature at the sealing ring was controlled to be close to the reflow temperature of the solder. Pull test results showed that the joint was sufficiently strong. Helium leak testing showed that the leak rate of the package met the requirements of MIL-STD-883E under optimized bonding conditions and bonded packages survived thermal shock testing. The testing, based on a design of experiments method, indicated that both laser incident power and scribe velocity significantly influenced bonding results. This novel method is especially suitable for encapsulation and vacuum packaging of chips or wafers containing MEMS and other micro devices with low temperature budgets, where managing stress distribution is important. Further, released and encapsulated devices on the sealed wafers can be diced without damaging the MEMS devices at wafer level.     

The effect of gold-nickel metallization microstructure on fluxless soldering

Gold plating is used in the microelectronics industry to maintain the wettability of metal substrates. The nature of wetting during soldering of gold plated metals is discussed, and the results of experiments on the fluxless wettability and oxidation of gold plated nickel are described. The results suggest that electrodeposition of a thin gold plate (0.14 (xm) and the concurrent reduction of nickel oxide produce a gold-nickel system which will wet without flux. Oxidation of nickel was observed to occur via nickel out-diffusion and by direct exposure of the substrate through pinhole plating defects. Auger chemical analysis indicates that pinholes do not produce oxidation of the surrounding substrate area.     

Kinetics of Dissolution and Isothermal Solidification for Gold-Enriched Solid–Liquid Interdiffusion (SLID) Bonding

This paper presents the development and characterization of a fluxless die-attach soldering process based on gold-enriched solid–liquid interdiffusion (SLID). Eutectic Au-Sn and pure Au were deposited by jet vapor deposition (JVD) onto two substrates, assembled in a sandwiched structure, and processed in a vacuum furnace using different temperatures and times. Microstructural characterization, based on scanning electron microscopy (SEM) and energy dispersive x-ray spectroscopy (EDS) analysis, revealed the formation of sound joints governed by the interdiffusion of the main constituents. Kinetic studies for the dissolution and the isothermal solidification stages were conducted. Differential scanning calorimetry (DSC) revealed a solder joint that is thermally stable up to 498°C, thus demonstrating the effectiveness of using the SLID process for the production of joints which require a lower processing temperature compared with their remelting point. Based on these findings, the recommended final bonding parameters are processing temperature and time of 340°C (310°C < T _P < 340°C) and 5 min, respectively.     

Characteristics of the Sn-Pb eutectic solder bump formed via fluxless laser reflow soldering

In an attempt to develop a fluxless reflow solder bumping process, the effects of processing variables, which include energy input rate and time, and the shape of solder disk on the microstructure of the solder/Cu pad interface and the shear strength of the joints were investigated. It was demonstrated that a proper combination of the variables could lead to the formation of a spherical solder bump with shear strength comparable to that formed via the conventional reflow soldering process. In addition, the kinetics of Cu pad dissolution into the solder during laser heating was modeled numerically to elucidate intermetallic formation mechanism at the solder/Cu pad interface. Jointly appointed by CAAM at POSTECH