Tubulation techniques for locating fine-leak sites in hermetic electronic packages

Bubble testing is often regarded, at best, as a poor method for locating gross leaks. However, it is demonstrated that, under proper conditions, bubble testing can be used to detect both gross and fine leaks, as well as their precise locations. Although not applicable in all situations, these leak-tests offer rapid and effective methods for identifying leak locations in components that are not adversely affected by the increased differential pressure. This method offers additional advantages such as not being fooled by virtual leaks, and indicating exact leak-location of single or multiple leaks in both the gross and fine leak regimes.     

Forward-stepwise regression analysis for fine leak batch testing of wafer-level hermetic MEMS packages

An advanced regression scheme is proposed to analyze fine leak batch testing data of multiple MEMS packages. The scheme employs the forward-stepwise regression method to infer the information of leaky packages from a batch test data. The analysis predicts the number of leaky packages and the true leak rate of each leaky package in a progressive manner. The scheme is implemented successfully using an actual batch test data obtained from wafer-level hermetic MEMS packages. An error analysis is followed to define the applicable domain of the scheme. Advanced formulations are also suggested to extend the applicable domain.     

插入BGA器件

利用管脚插入形式将电子元件固定到电脑主板上,作为一项非常流行的制造技术已经有二十多年的历史了.     

Non-metal hermetic encapsulation of a hybrid circuit

A cheap hermetic non-metal encapsulation was evaluated for use with a high reliability hybrid circuit subject to severe climatic environment for precise magnetic field measurements over 20 years lifetime.For this purpose a literature scan has been carried out establishing roughly the following results:

1. a) Humidity is the largest single risk faktor concerning reliability and expected life time of the device.

2. b) Plastic sealing does not represent a barrier against humidity for a long time.

3. c) There is no off-the-shelf solution available as usual real hermetic encapsulations are ruled out due to electrical, magnetic and price considerations.

Therefore a simple ceramic cover soldered by an AuSn preform directly to the ceramic substrate supporting the sensor and the thick film circuit has been developped to meet all requirements of a cheap, hermetic enclosure.This paper presents both the considerations taken into account to evaluate an appropriate encapsulation method as well as the final solution.     

光耦合器的BGA封装

导言光耦合器也称为光隔离器，它是允许电信号在电路或系统之间传输的半导体器件，同时确保这些电路或系统彼此之间电绝缘。典型的光耦合器是将两个电子组件—红外(IR)发光二极管(LED)和输出光电探测器集合到一个双列直插式封装(DIP)中。当正向电流(If)流经发光二极管时，电子转换为光子，辐射能量通过光耦介质传输，落在探测器的表面，在这里光子又转换为电子。光电探测器(在大多数情况下为光电晶体管)设计为具有较大的基极面积，因此基极-集电极结点的面积较大，而发射极的面积较小。如果基极和发射极接地，在光电晶体管的集电极施加…     

A wafer-level hermetic encapsulation for MEMS manufacture application

In order to simplify the processing complexity and cut down the manufacturing cost, a new wafer bonding technique using ultraviolet (UV) curable adhesive is introduced here for microelectromechanical systems (MEMS) device packaging and manufacturing applications. UV curable adhesive is cured through UV light exposure without any heating process that is suitable for the packaging of temperature-sensitive materials or devices. A Pyrex 7740 glass is chemically wet etched to form microcavities and utilized as the protection cap substrate. After a UV-curable adhesive is spin-coated onto the glass substrate, the substrate is then aligned and bonded through UV light exposure with a device substrate below. Electrical contact pad opening and die separation are done simultaneously by dicing. Two different testing devices, a dew point sensor and capacitive accelerometer, are built to evaluate the package strength and hermeticity. After the dicing process, no structural damage or stiction phenomenon is found in the packaged parallel capacitor. The acceleration test results also indicate that the package using the Loctite 3491 UV adhesive with 150 /spl mu/m bond width can survive more than 300 days at a 25/spl deg/C and 100% relative humidity working environment.     

A hermetic wireless subretinal neurostimulator for vision prostheses

A miniaturized, hermetically encased, wirelessly operated retinal prosthesis has been developed for preclinical studies in the Yucatan minipig, and includes several design improvements over our previously reported device. The prosthesis attaches conformally to the outside of the eye and electrically drives a microfabricated thin-film polyimide array of sputtered iridium oxide film electrodes. This array is implanted into the subretinal space using a customized ab externo surgical technique. The implanted device includes a hermetic titanium case containing a 15-channel stimulator chip and discrete circuit components. Feedthroughs in the case connect the stimulator chip to secondary power and data receiving coils on the eye and to the electrode array under the retina. Long-term in vitro pulse testing of the electrodes projected a lifetime consistent with typical devices in industry. The final assembly was tested in vitro to verify wireless operation of the system in physiological saline using a custom RF transmitter and primary coils. Stimulation pulse strength, duration, and frequency were programmed wirelessly from a Peripheral Component Interconnect eXtensions for Instrumentation (PXI) computer. Operation of the retinal implant has been verified in two pigs for up to five and a half months by detecting stimulus artifacts generated by the implanted device.     

美国CLEC在艰难中求生存

这两年来,美国的竞争性本地运营商(CLEC)可谓备受煎熬,不少公司面临破产,幸存者们也大多仍在苦难中挣扎。New Paradigm ResourcesGroup的数据显示,美国CLEC们的员工已经减少了35%,资本投资额也下滑了三分之二,CLEC拥有的数据交换机数目也比兴盛时期的2000年有所减少。然而令人惊奇的是,2002年CLEC们的总收入却不断增长,其接入线也在增加。看来,在行业低潮时,经历优胜劣汰和行业重组的CLEC们,正在走上正常的发展轨道。 美国CLEC在艰难中求生存     

Hydrogen permeation in optical fibres with hermetic carbon coatings

Hydrogen permeation has been measured for optical fibres with hermetic carbon coatings. Data obtained at elevated temperatures and high hydrogen pressures lead to predictions of extremely low permeation rates at typical operating conditions. In situ loss measurements have shown the existence of a lag time, during which no hydrogen reaches a fibre's interior     

Ceramic packages for liquid-nitrogen operation

To evaluate their compatibility for use in a liquid-nitrogen computer, metallized ceramic packages with test chips using controlled-collapse solder (Pb-Sn) technology were cycled between 30°C and liquid-nitrogen temperature. Room-temperature electrical resistance measurements were made at regular intervals of cycles to determine whether solder failure accompanied by a significant resistance increase had occurred. For the failed solder joints characterized by the highest thermal shear strain amplitude of 3.3%, it was possible to estimate the number of liquid-nitrogen cycles needed to produce the corresponding failure rate using a room-temperature solder lifetime model. Cross-sectional examination of the failed solder joints using scanning electron microscopy (SEM) and energy-dispersive X-ray analysis indicated solder cracking occurring at the solder-ceramic interface. Chip-pull tests on cycled packages yielded strengths far exceeding the minimal requirement. Mechanisms involving the formation of intermetallics are proposed to account for the observed solder fracture modes after liquid-nitrogen cycling and after chip pull. SEM examination of pulled chips in cycled packages found no apparent sign of cracking in quartz and polyimide for chip insulation     

CCGA packages for space applications

Commercial-off-the-shelf (COTS) area array packaging technologies in high reliability versions are now being considered for applications, including use in a number of NASA electronic systems being utilized for both the Space Shuttle and Mars Rover missions. Indeed, recently a ceramic package version specifically tailored for high reliability applications was used to provide the processing power required for the Spirit and Opportunity Mars Rovers built by NASA-JPL. Both Rovers successfully completed their 3-months mission requirements and continued exploring the Martian surface for many more moths, providing amazing new information on previous environmental conditions of Mars and strong evidence that water exists on Mars.Understanding process, reliability, and quality assurance (QA) indicators for reliability are important for low risk insertion of these newly available packages in high reliability applications. In a previous investigation, thermal cycle test results for a non-functional daisy-chained peripheral ceramic column grid array (CCGA) and its plastic ball grid array (PBGA) version, both having 560 I/Os, were gathered and are presented here. Test results included environmental data for three different thermal cycle regimes (−55/125 °C, −55/100 °C, and −50/75 °C). Detailed information on these—especially failure type for assemblies with high and low solder volumes—are presented. The thermal cycle test procedure followed those recommended by IPC-9701 for tin–lead solder joint assemblies. Its revision A covers guideline thermal cycle requirements for Pb-free solder joints. Key points on this specification are also discussed.In a recent investigation a fully populated CCGA with 717 I/Os was considered for assembly reliability evaluation. The functional package is a field-programmable gate array that has much higher processing power than its previous version. This new package is smaller in dimension, has no interposer, and has a thinner column wrapped with copper for reliability improvement. This paper will also present thermal cycle test results for assemblies of this and its plastic package version with 728 I/Os, both of which were exposed to four different cycle regimes. Two of these cycle profiles are specified by IPC-9701A for tin–lead, namely, −55 to 100 °C and −55 to 125 °C. One is a cycle profile specified by Mil-Std-883, namely, −65/150 °C, generally used for ceramic hybrid packages screening and qualification. The last cycle is in the range of −120 to 85 °C, a representative of electronic systems directly exposed to the Martian environment without use in a thermal control enclosure. Per IPC-9701A, test vehicles were built using daisy chain packages and were continuously monitored and/or manually checked for opens at intervals. The effects of many process and assembly variables—including corner staking commonly used for improving resistance to mechanical loading such as drop and vibration loads—were also considered as part of the test matrix. Optical photomicrographs were taken at various thermal cycle intervals to document damage progress and behavior. Representative samples of these are presented along with cross-sectional photomicrographs at higher magnification taken by scanning electron microscopy (SEM) to determine crack propagation and failure analyses for packages.     

Reliability issues for flip-chip packages

In this article, we review the reliability issues for plastic flip-chip packages, which have become an enabling technology for future packaging development. The evolution of area-array interconnects with high I/O counts and power dissipation has made thermal deformation an important reliability concern for flip-chip packages. Significant advances have been made in understanding the thermo-mechanical behavior of flip-chip packages based on recent studies using moiré interferometry. Results from moiré studies are reviewed by focusing on the role of the underfill to show how it reduces the shear strains of the solder balls but shifts the reliability concern to delamination of the underfill interfaces. The development of the high-resolution moiré interferometry based on the phase-shift technique provided a powerful method for quantitative analysis of thermal deformation and strain distribution for high-density flip-chip packages. This method has been applied to study plastic flip-chip packages and the results and impacts on delamination at the die/underfill interface and in the underfill region above the plated through-hole via are discussed. Here a related reliability problem of die cracking during packaging assembly and test is also discussed. Finally, we discuss briefly two emerging reliability issues for advanced flip-chip packages, one on the packaging effect on Cu/low k interconnect reliability and the other on electromigration of solder balls in flip-chip packages.     

Chip corrosion in plastic packages

The corrosion performance of both unencapsulated and plastic encapsulated parts has been studied under temperature-humidity-bias (THB) stresses using a patterned test chip with aluminum metallization. The effect of encapsulation materials and ionic contaminants purposely introduced on the chip surface has been determined for both accelerated THB and severe, real life conditions.Unencapsulated test chips exhibited very different THB performance characteristics from encapsulated parts including a near-zero induction time and a shallow post-induction slope on the % failures vs time curve. The induction time and mean-time-to-failure (MTF) for encapsulated devices were strong functions of both the polymeric class of encapsulant and the particular compound employed. At least part of the difference in performance between molding compounds has been attributed to impurities inherent in the compounds. Impurities contributed from conductive epoxies used for die attach also adversely affect the device's MTF, as do normal contaminants present on as-plated leadframes.The environmental factors of temperature, relative humidity and bias greatly affect the performance of encapsulated devices. In this study, the MTF decreased dramatically with bias between 5 and 30 volts, the range over which most devices operate. The acceleration factors relating device performance in an 85°C/85%RH environment to severe, real life conditions were surprisingly small and somewhat dependent on the encapsulant.     

Thermal modelling of semiconductor packages

This paper presents an improved approach for thermal characterization and simulation of semiconductor packages. The model can significantly reduce the simulation efforts for the design of complex technical thermal systems. It will be shown that the principle of superposition can be used to overcome the problems of thermal resistance narrowings. As the model structure implements a biunique mapping between a special set of border conditions and its parameters, a simple characterization procedure can be applied and the accuracy of the model is found to be independent of the boundary conditions.     

Ni-Ti基合金机械气密封装方法研究

研究发现Ni-Ti合金能够在电子组件机械气密封装领域发挥重要作用。为此,开展了某型Ni-Ti基合金机械气密封装方法研究,并在行业内首次设计了Ni-Ti基合金机械气密封装结构,该结构包含某型Ni-Ti基合金环、销钉柱和腔体壁。通过开展厚度分别为2.0,1.5,1.0,0.5和0.25 mm腔体壁的Ni-Ti基合金样件气密封装和环境试验验证后,表明:基于Ni-Ti基合金的机械气密封装方法切实可行,工艺实现难度不大。其中,腔体壁厚为0.5mm和0.25 mm的销钉柱气密性最容易满足GJB548B—2005的验收要求,且成品率可达100%。     

Silicon-based micromachined packages for high-frequencyapplications

A novel low-cost packaging approach is presented in this paper, which is appropriate for high-frequency electronic circuits in discrete, as well as integrated, configurations. This approach is based on silicon micromachining and can effectively provide on-wafer and discrete packaging for high-quality high-precision miniature components. The required fabrication techniques are compatible with standard integrated-circuit processing and, for this reason, are low in fabrication costs. As an example, this paper presents the development of a Ka-band package that can shield and electromagnetically isolate monolithic-microwave integrated-circuit components, such as a phase shifter. The performance of this package is compared to that of a ceramic one and demonstrates excellent electrical response in addition to high design versatility     

Multichip modules: next-generation packages

Multichip modules (MCMs), which interconnect multiple bare dice by means of a stack of conductive and dielectric thin films, are discussed. Among their advantages are reduced delays between chips, simplified power distribution, and enhanced dissipation capabilities. Key design demands that should be weighed by IC design engineers planning to use MCMs are examined. They concern transmission delays, power distribution, heat dissipation, and temperature, as well as testing, burn-in, and rework. The various approaches to MCM packages are described. Factory-programmable versus user-programmable options are considered. Techniques for connecting chips to substrates are discussed     

长期贮存对气密性封装的影响研究

密封微电子器件在对可靠性要求较高领域占有绝对的地位,为了研究长期室内自然贮存对密封微电子封装性能的影响,对贮存在北京某研究所库房的多种气密性封装微电子器件进行试验分析。运用破坏性物理分析(DPA)方法检验样品的密封性、内部形貌、键合强度和芯片粘贴强度等,总结出长期贮存对气密性封装器件封装性能影响的结论;并根据密封性测试结果对器件分组,分别得到密封合格与不合格产品长期贮存后封装性能的实测数据,对密封性能对元器件贮存可靠性的影响进行研究,为元器件的筛选和贮存提供借鉴。     

Assembly-level reliability of flex-substrate BGA, elastomer-on-flex packages and 0.5 mm pitch partial array packages

The assembly-level reliability of the 0.8 mm pitch flex-substrate BGA, 0.65 mm pitch elastomer-on-flex package, and 0.5 mm pitch partial array BGA has been characterized in thermal fatigue, out-of-plane deformation, low frequency repeated bending, and thermal aging. Non-linear finite element models have been used to identify and predict the dominant failure mechanisms and identify the assembly parameters which have a dominant impact on reliability. The model predictions have been verified with accelerated test data. The results have been bench marked against other technologies including 1.5 mm pitch OMPAC^TM and 1 mm pitch, 196 I/O Glob-top BGA.