Sources and control of volatile gases hazardous to hermeticelectronic enclosures

Four gases that threaten operating reliability may be present in hermetic electronic enclosures. Condensates of moisture and/or ammonia can cause metallization corrosion. Hydrogen is a rapid diffuser that can degrade metal-oxide-semiconductor (MOS) device operation. Oxygen can cause oxidation and ensuing failure of solder attachment materials within the sealed package. Other gases, such as carbon dioxide, helium, argon, and organic volatiles are not threats to reliability, but do provide clues to package materials behavior. Knowing sealed package ambient gas composition helps improve materials and processes for hermetic sealing and enables process control to assure reliable products. This paper describes the analysis method for hermetic microelectronics, residual gas analysis (RGA), available at only a few laboratories worldwide. It discusses sealing processes and package piece part materials that are sources of volatiles hazardous to product reliability. It presents materials selection and improvement considerations to reduce and control dangerous volatiles in hermetic packages     

密封胶粘剂在高可靠微电子封装中的应用

阐述了高可靠微电子封装对密封胶粘剂的性能要求.通过试验优选出一种能实现高可靠、高气密粘接封帽的环氧树脂胶粘剂,用该胶粘剂封帽的外壳通过了严苛的可靠性考核.详细介绍了胶粘封帽工艺过程,并对影响封帽质量及可靠性的因素进行了探讨.     

Water vapor penetration rate into enclosures with known air leak rates

The rate at which water vapor penetrates a faulty seal in a "hermetically sealed" device has been examined both experimentally and theoretically in this study. The experimental data were generated by studying the rate of moisture ingress into two types of packages; a TO-5 can and a ¼ × ¼ in ceramic flatpack. The TO-5 packages were fitted with capillary tubes of varying diameters with known air leak rates and represented the gross leak range (down to 10^-5atm . cm³/s) while the ¼ × ¼ in ceramic flatpacks were used to study the fine leak range (10^-6to 10^-8atm . cm³/s). Both type packages were fitted with miniature moisture sensors (surface conductivity type) and calibrated at known relative humidities prior to sealing. The finished test packages were then exposed to constant high-humidity conditions and monitored for moisture content as a function of time. A theoretical analysis was performed by using conventional leak rate equations to convert air leak rates, at standard test conditions, to water vapor leak rates at partial pressure differentials seen typically at room ambient conditions. These data compared favorably with the experimental results in the range tested and suggests that present hermeticity specifications are too lenient for long-term reliability requirements.     

平行缝焊工艺抗盐雾腐蚀技术研究

抗盐雾腐蚀是提高集成电路封装可靠性的重要手段之一.根据金属腐蚀机理,通过优化封焊工艺和AuSn合金焊料平行缝焊封盖工艺,以及在封盖后再次进行电镀修复损伤等措施,提高了平行缝焊集成电路的杭盐雾腐蚀能力.     

基于平行缝焊工艺的AuSn合金焊料封盖技术研究

为了解决聚合物粘结电路的质量与长期可靠性问题,提出了一种采用平行缝焊工艺对AuSn合金焊料熔封器件进行封盖的新方法。通过对平行缝焊工艺的深入研究,解决了该类器件封盖的气密性与外观质量问题,从而找到了一种有效解决熔封外壳组装的低温聚合物粘结电路水汽含量、抗剪强度、键合强度控制的新方法。     

密封封装内部水汽含量判据研究

密封封装内部的水汽对于半导体器件的可靠性是一种威胁,由此导致的硅表面铝金属线的腐蚀是一种主要的失效机理。为了防止密封封装内部发生腐蚀失效,从而提高器件的可靠性,美军标和我国国军标均给出了内部水汽含量的试验流程和判据。然而另一些研究表明,水汽的单独存在并不会导致铝线腐蚀失效。研究了水汽在密封器件的腐蚀失效机理中的作用,对硅表面铝线的腐蚀过程进行了数学描述,分析了目前标准中内部水汽含量判据,并给出了防止密封器件腐蚀失效的建议。     

Design and Test Results of an Optical Fiber Feedthrough for an Optical Submarine Repeater

A new hermetic sealing structure is described in which optical fibers are metal coated and sealed off. The gap between the fibers and the metal pipe is filled with solder. The sealing structure is used as a feedthrough of a repeater for a long-haul optical fiber submarine cable system. According to theoretical study, airtightness was found reliable for a long period of time by utilizing a self-seal effect operating at the time of pressurizing through the structure where circumferences of fibers are soldered for sealing. Manufacture on trial proved that perfect airtightness was achieved even after a heat cycle test (60°C- -10°C) and shock test (50 G). The incremental loss due to temperature changes in the range from 60°C to - 10°C was less than 0.015 dB and an incremental loss of 0.06 dB or less was observed when the structure was pressurized by 800 kg/cm2, however no residual loss could be found.     

可伐合金气密封接的预氧化

可伐合金和硅硼硬玻璃是通过可伐合金表面的氧化物与玻璃互溶而紧密结合在一起的,所以可伐合金的预氧化是金属外壳制造的一个非常重要的工艺环节,是直接影响气密封接的一个重要因素。为实现气密封接,可伐合金预氧化需要得到的氧化物应是Fe_3O_4和FeO,而不希望得到Fe_2O_3。同时,氧化膜的厚度要控制在一定的范围内;氧化膜过薄则氧化物完全溶于玻璃,造成玻璃与金属基体表面的直接封接,使封接强度下降;氧化膜过厚则造成金属表面氧化物较粗糙疏松,封接件容易漏气。为达到上述两个目的,可以从可伐合金氧化的热力学和动力学出发,通过控制氧化气氛,氧化温度和时间来实现。     

Measurement of Moisture Inside the Hermetic Package of Semiconductor Device

The mositure content inside the hermetic package of semiconductor de-vice has been quantitatively measured by using in-site sensor technique and computer-aided-test system.The principle and apparatus for measurement are introduced.The results show good repeatability and consistency.This technology can be used as a stan-dard test for controlling the moisture content within semiconductor device package.     

Wafer-Level Package With Simultaneous TSV Connection and Cavity Hermetic Sealing by Solder Bonding for MEMS Device

In this paper, a wafer-level package with simultaneous through silicon via (TSV) connection and cavity hermetic sealing by low-temperature solder bonding for microelectromechanical system (MEMS) device such as resonator is presented. Wet etching technique combined with dry etching technique is utilized to achieve a “Y-shaped” through wafer interconnection structure to shorten the TSV in order to reduce cost. Ansoft ${hbox {HFSS}}^{rm TM}$ 3-D electromagnetic simulator is used to assess the transition properties of signal with frequency of the new interconnection structure. Sn solder bonding is utilized to achieve simultaneous TSV connection and cavity hermetic sealing. Average shear strength of 19.5 Mpa and excellent leak rate of around ${hbox {1.9}} times {hbox {10}} ^{-9}~{hbox {atm cc/s}}$ have been achieved, which meet the requirements of MIL-STD-883E. Kevin structure is also fabricated to measure the resistance of the metallized TSV, the resistance of the “Y-shaped” through wafer interconnection and the contact resistance of the Cu/Sn IMC bond joint.      

Cu–Cu Hermetic Seal Enhancement Using Self-Assembled Monolayer Passivation

Low-temperature Cu–Cu thermocompression bonding enabled by self-assembled monolayer (SAM) passivation for hermetic sealing application is investigated in this work. Cavities are etched to a volume of 1.4 × 10^?3 cm³ in accordance with the MIL-STD-883E standard prescribed for microelectronics packaging. The wafer pairs (nonfunctional cavity wafer and cap wafer) are annealed and bonded at 250°C under a bonding force of 5500 N. The encapsulated cavities undergo helium overpressure in a bombing chamber, and the helium leak rate is detected by a mass spectrometer. The measurement results show that the cavities sealed with Cu–Cu bonding after SAM passivation exhibit excellent hermeticity with a leak rate below 10^?9 atm cm³/s, which is an improvement of at least 2× compared with the control sample without SAM passivation.     

采用金锡合金的气密性封装工艺研究

根据功率器件的气密性封装要求,设计了完整的金锡封焊工艺方法和流程,研究了工艺中的技术难点,提出了确保封装工艺稳定性和可靠性的技术要点.实验选甩Au80Sn20预成型焊环作为封接材料对器件进行气密性封装.通过大量试验得出了最佳工艺曲线(包括温度、时间、气氛和压力等).密封后的产品在经受各项环境试验和机械试验后,其结构完整性、电学特性、机械牢固性和封装气密性均能很好地满足要求,证明了采用倒置型装配的金锡封焊工艺的可行性及优越性.     

氢对金属封装密封元器件可靠性的影响

氢气作为金属封装密封电子元器件中可能存在的一种内部气氛,能够参与其失效过程,影响其性能、寿命与可靠性,在大部分情况下是有害的。研究了密封腔中氢气的来源,分析了与氢有关的水汽、裂纹、金属性质变化以及半导体功能退化等各种失效原因以及检测方法。并提出了一些可行的解决办法。     

基于LTCC腔体结构的新型微波多芯片组件研究

 传统的微波多芯片组件(MMCM)金属壳体气密封装存在需要增加重量、互连线和成本等缺点.采用低温共烧陶瓷(LTCC)腔体技术为MMCM研制提供了一种实现微波互连基板和封装外壳一体化的理想解决方案.本文采用微波分析软件对微波LTCC腔体及其过渡结构进行了仿真和优化,并与LTCC腔体试验样品的测试结果进行了对比,两者吻合较好.采用微波LTCC腔体技术研制成功一个X波段T/R组件接收支路.     

A Novel Wafer-Level Hermetic Packaging for MEMS Devices

Some emerging microelectromechanical systems (MEMS) devices such as high-performance inertial sensors and high-speed actuators must be operated in a high vacuum and in order to create this vacuum environment, specific packaging is required. To satisfy this demand, this paper presents a novel method for hermetic and near-vacuum packaging of MEMS devices. We use wafer-level bonding technology to combine with vacuum packaging, simultaneously. For this packaging solution, the wafers with air-guided micro-through-holes were placed on a custom-built design housed in a vacuum chamber maintained at a low-pressure environment of sub-10 mtorr. Packaging structure is then sealed by solder ball reflow process with the lower heating temperature of 300degC to fill up micro-through-hole. Experimental results shown the hermetical packaging technique using solder sealing is adapted to the wafer-level microfabrication process for MEMS devices and can achieve better yield and performance. Thus, this technique is very useful for many applications with high performance and low packaging cost can be obtained due to wafer-level processing.     

封装腔体内氢气含量控制

目前,对密封腔体内的水汽、二氧化碳、氧气含量的研究比较多,内部水汽含量控制在≤5 000 ppm、氧气控制在≤2 000 ppm、二氧化碳控制在≤4 000 ppm、氦气控制在≤1 000 ppm的密封工艺技术已解决[9],氢气含量控制的研究则未见报道。对于一些气密性要求高的封装应用领域,还需要控制氢气含量,如MEMS、GaAs电路等。分析了平行缝焊、Au80Sn20合金封帽的导电胶、合金烧结的器件的内部氢气含量,并分析了125℃168 h和125℃1 000 h贮存前后氢气含量的变化情况;在试验的基础上,提出了氢气的主要来源和针对性的工艺措施,并取得了期望的结果：密封器件经过125℃、1 000 h贮存后的氢气含量也能控制在≤4 000 ppm。     

陶瓷封装腔体内气体含量分析与控制

气密性封装技术应用广泛,内部水汽的含量能很好地控制在5 000×10-6以下。但在气密性封装器件的失效分析中发现,失效器件的某些失效与其内部除水汽之外的其他气氛含量异常有关,如锡基焊料焊接芯片长期贮存后抗剪/抗拉强度下降,与内部氧气含量高有关;银玻璃烧结的,长期贮存后抗剪/抗拉强度下降,与内部二氧化碳含量异常相关;内部...     

X射线在陶瓷气密封装空洞检查中的不足

在集成电路的陶瓷气密封装中，往往使用X射线照相技术来检查密封区的空洞情况并由此判断密封质量的好坏。通常情况下，X射线的检测结果是可信的，但是也存在由于某种原因导致焊接空洞无法为X射线所探测的情形。此外，部分具有底部热沉的陶瓷外壳，其热沉材料本身对X射线的吸收很大，会对焊接区存在的空洞的成像进行覆盖，并造成漏判。另外，X射线对于不同层面的空洞会进行图像叠加，从而无法对空洞部位进行准确定位。文中从X射线照相的原理上对此类X射线照相中的空洞漏判等现象进行了分析和探讨。     

A low cost multichip packaging technology for monolithic microwaveintegrated circuits

This paper describes a multichip module technology based on highly impermeable liquid crystal polymers (LCPs) to interconnect and package monolithic microwave integrated circuits (MMICs). Because of the low moisture permeability of the LCPs, the packages can be made hermetic without heavy expensive housings can be two to four times lighter and one-fifth the cost of conventional ceramic based transmit/receive (T/R) modules. The LCP material has a low dielectric constant (2.65) and low-loss tangent and is manufacturable using high volume, large-area processing methods that provide very reliable high-performance circuits at low cost. Using flip-chip bonded MMICs attached to a high thermal conductivity, low coefficient of thermal expansion substrate, this innovative technology can meet a variety of commercial, military, and NASA requirements     

摩擦涂敷铟封工艺

本文叙述了“摩擦涂敷”铟封工艺,报导了用这种工艺封接的 He-Ne 激光管、标准脉冲氙灯及玻璃与铜、玻璃与不锈钢、石英与铝等的封接技术。