波峰焊及再流焊无铅焊点组织演变规律的研究

以电子封装线上的波峰焊无铅焊点Sn-0.7Cu/Cu、回流焊无铅焊点Sn-3Ag-0.5Cu/Cu为对象,研究了150 ℃时效过程中无铅焊点处金属间化合物(IMC)、焊料合金组织的演化规律及界面处金属间化合物生长的动力学.试验结果表明:两种无铅焊点处IMC层的厚度随着时效时间的延长而增加,IMC层的生长基本上符合抛物线规律,因此IMC层的长大受元素扩散控制;且两种无铅焊点处IMC层的生长速率常数相近,但Sn-0.7Cu焊料中Sn的晶粒尺寸较Sn-3Ag-0.5Cu中的大;长期时效后,在试样的IMC层内发现有孔洞产生.     

微量Ni对Sn-3.0Ag-0.5Cu钎料及焊点界面的影响

研究了Ni的含量对无铅钎料Sn-3.0Ag-0.5Cu润湿性、熔点、重熔及老化条件下界面化合物(IMC)的影响。结果表明:微量Ni的加入使SnAgCu润湿力增加6%;使合金熔点略升高约3℃;重熔时在界面形成了(Cu,Ni)6Sn5IMC层,且IMC厚度远高于SnAgCu/Cu的Cu6Sn5IMC厚度。在150℃老化过程中,SnAgCuNi/Cu重熔焊点IMC随着时间的增加,其增幅小于SnAgCu/Cu的增幅,此时Ni对IMC的增长有一定抑制作用。     

SnAgCu系钎料的合金组织和力学性能

研究了Cu含量对SnAgCu系钎料合金显微组织及其与化学镀Ni基板钎焊接头力学性能的影响。结果表明:高Cu含量SnAgCu合金会产生较多的(CuxNi1-x)6Sn5金属间化合物,从而减少镀Ni层的消耗,进一步提高钎焊接头的剪切强度。与Sn-3.0Ag-0.3Cu相比,Sn-3.0Ag-1.0Cu钎焊接头剪切强度提高了6.78%。经过150℃时效1000h后,界面Ni3(P,Sn)层的增长率从Sn-3.0Ag-0.3Cu合金的约66%降低到Sn-3.0Ag-1.0Cu合金的约40%。     

Sn-58Bi-0.5Ce/Cu界面金属间化合物的性能研究

研究了Sn-58Bi-0.5Ce/Cu钎焊接头在120℃时效过程中界面组织形貌及金属间化合物层(IMC)的厚度变化。结果表明:在Sn-58Bi-0.5Ce/Cu钎焊接头界面处形成了较为平坦的双层金属间化合物,靠近钎料的上层为Cu6Sn5相,邻近Cu基板的下层为Cu3Sn相。等温时效处理后,IMC层逐渐凸起,且随着时效时间的增加,IMC层不断增厚。通过对实验数据进行拟合,得到钎焊接头界面IMC层的生长速度常数为5.77×10–17m2/s。     

Sn-9Zn/Cu 焊点界面反应及其化合物生长行为

通过扫描电镜(SEM)等手段研究了Sn-9Zn/Cu在不同浸焊时间与时效时间等条件下的界面反应及其金属间化合物(IMC)生长行为。结果表明:在浸焊后,Sn-9Zn/Cu钎焊接头界面形成了扇贝状的界面化合物Cu5Zn8,IMC层厚度随着浸焊时间与时效处理时间的增加而增加,未时效处理的焊点界面IMC与铜基板接触的一面较为平直,而与钎料接触的一侧呈现出锯齿状,随着时效时间的增加,界面变得越来越不平整;另外在IMC层与焊料之间产生裂缝现象,分析认为是由于钎料与IMC之间的热膨胀系数差异导致热应力形成裂缝。浸焊600 s后的试样在时效15 d后IMC层与Cu基板接触侧产生了与初始金属间化合物Cu5Zn8不同的三元化合物Cu6(Sn,Zn)5。     

Sn0.7Cu-xEr/Cu焊点界面反应及其化合物层生长行为研究

通过回流焊工艺制备了Sn0.7Cu-x Er/Cu(x=0,0.1,0.5)钎焊接头,研究钎焊温度及等温时效时间对接头的界面金属间化合物(IMC)的形成与生长行为的影响。结果表明:Sn0.7Cu钎料中微量稀土Er元素的添加,能有效抑制钎焊及时效过程中界面IMC的形成与生长。在等温时效处理过程中,随着时效时间的延长,界面反应IMC层不断增厚,在相同时效处理条件下,Sn0.7Cu0.5Er/Cu焊点界面IMC层的厚度略小于Sn0.7Cu0.1Er/Cu焊点界面的厚度。通过线性拟合方法,得到Sn0.7Cu0.1Er/Cu和Sn0.7Cu0.5Er/Cu焊点界面IMC层的生长速率常数分别为3.03×10–17 m2/s和2.67×10–17 m2/s。     

回流焊对SnAgCu焊点IMC及剪切强度的影响

研究了回流焊次数对Sn-0.3Ag-0.7Cu-xNi/Cu(x=0,0.05)焊点的界面反应及其剪切强度的影响。结果表明:随着回流焊次数的增加,界面金属间化合物(IMC)Cu6Sn5和(Cu1-xNix)6Sn5的厚度均增加。在钎料中添加w(Ni)为0.05%,可有效抑制IMC的生长,与回流焊次数无关。回流焊次数对Sn-0.3Ag-0.7Cu/Cu和Sn-0.3Ag-0.7Cu-0.05Ni/Cu的剪切强度影响都不大,五次回流焊后剪切强度略有下降,剪切强度分别为21MPa和25MPa。发现断裂面部分在钎料中,部分在钎料和IMC之间。     

SnBiEr/Cu界面反应及时效过程中IMC的研究

采用SEM观察等手段研究了Sn58BixEr(x=0,0.1,0.5;表示添加质量分数0.01%,0.5%的Er)/Cu钎焊接头界面反应以及在120℃时效过程中金属间化合物(IMC)的生长行为。实验结果表明:Sn58BixEr/Cu钎焊接头IMC层厚度随着钎焊温度的升高而增厚,添加微量的Er能够有效抑制界面IMC的生长。在时效过程中,界面IMC层的厚度随着时效时间的增加而逐渐增厚。通过对实验数据进行拟合,得出120℃时效温度下Sn58Bi0.1Er/Cu和Sn58Bi0.5Er/Cu的IMC层的生长速率常数分别为3.42×10–16 m2/s和2.84×10–16 m2/s。     

Ga元素含量对305钎料组织及性能的影响

通过在Sn-3Ag-0.5Cu钎料中添加不同含量的Ga，并采用差示扫描量热法（DSC）、万能试验机测试方法配制合金材料的熔化特性曲线、力学性能、金相结构、焊接润湿扩展率等性质，研究Ga含量对Sn-3Ag-0.5Cu钎料的熔化过程、焊接润湿扩展性以及组织和力学性能方面的影响。结果表明，Sn-3Ag-0.5Cu钎料中加入Ga元素以后，随着Ga增加，钎料的熔点显著降低，熔程也逐渐增大；适量的Ga元素可以改善Sn-3Ag-0.5Cu钎料的润湿性能；当Ga元素的添加量质量分数达到0.5%时，Sn-3Ag-0.5Cu钎料的组织均匀，晶粒明显细化，钎料的力学性能最佳，但Ga元素含量进一步增加时，在晶界处析出黑色富Ga相，对钎料力学性能产生了不利影响。     

时效处理对Sn-9Zn/Cu界面组织及剪切性能的影响

采用扫描电子显微镜及万能材料实验机,研究分析了Sn-9Zn/Cu钎焊接头在150 ℃下长期时效过程中界面形貌及接头剪切性能的变化.结果表明:时效前,Sn-9Zn/Cu界面为薄且平直的Cu-Zn金属间化合物层(IMC).经过时效处理后,IMC层厚度明显增加,变得粗大不平,而且有Cu-Sn化合物生成.同时,Sn-9Zn/Cu钎焊接头的剪切强度明显下降,时效至1 000 h时剪切强度仅为初始的40.65%.时效过程中剪切断口的脆性断裂趋势逐渐增大.     

Resolution Enhancement Technology:Integrated Process Solutions using OPC

DUV lithography, using the 248 nm wavelength, is a viable manufacturing option for devices with features at 130 nm and less. Given the low kl value of the lithography, integrated process development is a necessary method for achieving acceptable process latitude. The application of assist features for rule based OPC requires the simultaneous optimization of the mask, illumination optics and the resist.Described in this paper are the details involved in optimizing each of these aspects for line and space imaging.A reference pitch is first chosen to determine how the optics will be set. The ideal sigma setting is determined by a simple geometrically derived expression. The inner and outer machine settings are determined, in turn,with the simulation of a figure of merit. The maximum value of the response surface of this FOM occurs at the optimal sigma settings. Experimental confirmation of this is shown in the paper.Assist features are used to modify the aerial image of the more isolated images on the mask. The effect that the diffraction of the scattering bars (SBs) has on the image intensity distribution is explained. Rules for determining the size and placement of SBs are also given.Resist is optimized for use with off-axis illumination and assist features. A general explanation of the material' s effect is discussed along with the affect on the through-pitch bias. The paper culminates with the showing of the lithographic results from the fully optimized system.     

Cost-effective test solutions for smart card and other integrated flash applications

From its emergence in the late 1980s as a lower cost alternative to early EEPROM technologies, flash memory has evolved to higher densities and speedsand rapidly growing acceptance in mobile applications.In the process, flash memory devices have placed increased test requirements on manufacturers. Today, as flash device test grows in importance in China, manufacturers face growing pressure for reduced cost-oftest, increased throughput and greater return on investment for test equipment. At the same time, the move to integrated flash packages for contactless smart card applications adds a significant further challenge to manufacturers seeking rapid, low-cost test.     

An improved parallel thinning algorithm with two subiterations

The parallel thinning algorithm with two subiterations is improved in this paper. By analyzing the notions of connected components and passes, a conclusion is drawn that the number of passes and the number of eight-connected components are equal. Then the expression of the number of eight-connected components is obtained which replaces the old one in the algorithm. And a reserving condition is proposed by experiments, which alleviates the excess deletion where a diagonal line and a beeline intersect. The experimental results demonstrate that the thinned curve is almost located in the middle of the original curve connectivelv with single pixel width and the processing speed is high.     

Theoretical analysis of the relationship between the Brillouin gain coefficient and the strain in the optical-fiber sensors

The relation between the power of the Brillouin signal and the strain is one of the bases of the distributed fiber sensors of temperature and strain. The coefficient of the Bfillouin gain can be changed by the temperature and the strain that will affect the power of the Brillouin scattering. The relation between the change of the Brillouin gain coefficient and the strain is thought to be linear by many researchers. However, it is not always linear based on the theoretical analysis and numerical simulation. Therefore, errors will be caused if the relation between the change of the Brillouin gain coefficient and the strain is regarded as to be linear approximately for measuring the temperature and the strain. For this reason, the influence of the parameters on the Brillouin gain coefficient is proposed through theoretical analysis and numerical simulation.     

Novel fiber-optical interferometer with miniaturized probe for in-hole measurements

Today, micro-system technology and the development of new MEMS （Micro-Electro-Mechanical Systems） are emerging rapidly. In order for this development to become a success in the long run, measurement systems have to ensure product quality. Most often, MEMS have to be tested by means of functionality or destructive tests. One reason for this is that there are no suitable systems or sensing probes available which can be used for the measurement of quasi inaccessible features like small holes or cavities. We present a measurement system that could be used for these kinds of measurements. The system combines a fiber optical, miniaturized sensing probe with low-coherence interferometry, so that absolute distance measurements with nanometer accuracy are possible.     

Study of waveguide coupling efficiency in hybrid silicon lasers

This paper presents a new method to increase the waveguide coupling efficiency in hybrid silicon lasers. We find that the propagation constant of the InGaAsP emitting layer can be equal to that of the Si resonant layer through improving the design size of the InP waveguide. The coupling power achieves 42% of the total power in the hybrid lasers when the thickness of the bonding layer is 100 nm. Our result is very close to 50% of the total power reported by Intel when the thickness of the thin bonding layer is less than 5 nm. Therefore, our invariable coupling power technique is simpler than Intel＇s.     

Curved crystal spectrometer for the measurement of X-ray lines from laser-produced plasmas

In order to diagnose the laser-produced plasmas, a focusing curved crystal spectrometer has been developed for measuring the X-ray lines radiated from a laser-produced plasmas. The design is based on the fact that the ray emitted from a source located at one focus of an ellipse will converge on the other focus by the reflection of the elliptical surface. The focal length and the eccentricity of the ellipse are 1350 mm and 0.9586, respectively. The spectrometer can be used to measure the X- ray lines in the wavelength range of 0.2-0.37 nm, and a LiF crystal （200） （2d = 0.4027 nm） is used as dispersive element covering Bragg angle from 30° to 67.5°. The spectrometer was tested on Shengnang- Ⅱ which can deliver laser energy of 60-80 J/pulse and the laser wavelength is 0.35 μm. Photographs of spectra including the 1 s2p ^1P1-1s^2 ^1S0 resonance line（w）, the 1s2p ^3P2-1s^2 1S0 magnetic quadrupole line（x）, the 1s2p ^3P1-1 s^2 ^1S0 intercombination lines（y）, the 1 s2p ^3S~1-1 s^2 ^1S0 forbidden line（z） in helium-like Ti Ⅹ Ⅺ and the 1 s2s2p ^2P3/2-1 s622s ^2S1/2 line（q） in lithium-like Ti Ⅹ Ⅹhave been recorded with a X-ray CCD camera. The experimental result shows that the wavelength resolution（λ/△ 2） is above 1000 and the elliptical crystal spectrometer is suitable for X-ray spectroscopy.     

Preparation and Characterization of TaN ALD Precursors

High purity organic-tantalum precursors for thin film ALD TaN were synthesized and characterized.Vapor pressure and thermal stability of these precursors were studied.From the vapor pressure analysis,it was found that TBTEMT has a higher vapor pressure than any other published liquid TaN precursor,including TBTDET,TAITMATA,and IPTDET.Thermal stability of the alkyl groups on the precursors was investigated using a 1H NMR technique.The results indicated that the tertbutylimino group is the most stable group on TBTDET and TBTEMT as compared to the dialkylamido groups.Thermal stability of TaN precursors decreased in the following order:TBTDET ＞ PDMAT ＞ TBTEMT.In conclusion,precursor vapor pressure and thermal stability were tuned by making slight variations in the ligand sphere around the metal center.     

Electronic Structure of Semiconductor Nanocrystals

This paper reviews our recent development of the use of the large-scale pseudopotential method to calculate the electronic structure of semiconductor nanocrystals, such as quantum dots and wires, which often contain tens of thousands of atoms. The calculated size-dependent exciton energies and absorption spectra of quantum dots and wires are in good agreement with experiments. We show that the electronic structure of a nanocrystal can be tuned not only by its size,but also by its shape. Finally,we show that defect properties in quantum dots can be significantly different from those in bulk semiconductors.     

A rigorous proof of MIMO channel capacity’s increase with antenna number

It is well known that adding more antennas at the transmitter or at the receiver may offer larger channel capacity in the multiple-input multiple-output（MIMO） communication systems. In this letter, a simple proof is presented for the fact that the channel capacity increases with an increase in the number of receiving antennas. The proof is based on the famous capacity formula of Foschini and Gans with matrix theory.