Study into grinding force in back grinding of wafer with outer rim

Back grinding of wafer with outer rim (BGWOR) is a new method for carrier-less thinning of silicon wafers. At present, the effects of process parameters on the grinding force remain debatable. Therefore, a BGWOR normal grinding force model based on grain depth-of-cut was established, and the relationship between grinding parameters (wheel infeed rate, wheel rotational speed, and chuck rotational speed) and normal grinding force was discussed. Further, a series of experiments were performed to verify the BGWOR normal grinding force model. This study proves that the BGWOR normal grinding force is related to the rotational direction of the wheel and chuck, and the effect of grinding mark density on the BGWOR normal grinding force cannot be ignored. Moreover, this study provides methods for reducing the grinding force and optimizing the back thinning process of the silicon wafer.The full text can be downloaded at https://link.springer.com/article/10.1007/s40436-020-00316-z     

Sensitivity analysis of the surface integrity of monocrystalline silicon to grinding speed with same grain depth-of-cut

Mechanisms for removal of materials during the grinding process of monocrystalline silicon have been extensively studied in the past several decades. However, debates over whether the cutting speed significantly affects the surface integrity are ongoing. To address this debate, this study comprehensively investigates the effects of cutting speed on surface roughness, subsurface damage, residual stress, and grinding force for a constant grain depth-of-cut. The results illustrate that the changes in the surface roughness and subsurface damage relative to the grinding speed are less obvious when the material is removed in ductile-mode as opposed to in the brittle-ductile mixed mode. A notable finding is that there is no positive correlation between grinding force and surface integrity. The results of this study could be useful for further investigations on fundamental and technical analysis of the precision grinding of brittle materials.The full text can be downloaded at https://link.springer.com/content/pdf/10.1007%2Fs40436-020-00291-5.pdf     

The effect of pretinning on the strength of a chip carrier solder joint

Pretinning of gold-plated components is often done to avoid the formation of brittle Au/Sn intermetallic compounds, which may lower the mechanical strength of the joints. In this investigation the reliability of 32LCCs surface mounted on alumina boards is tested in internal and external temperature cycling, as well as in shear tests, and the effect of pretinning is studied. One thousand times of temperature cycling between ?55 and +125°C and 2000 h of power cycling with an upper joint temperature of +75°C did not cause any electrical opens. Shear tests made after a 168 h heat treatment at +125°C and 1000 temperature cycles showed that forces of approximately 1000 N were required to break the chip carrier joints. The microstructure of Sn62/Pb36/Ag2 solder joints containing gold was examined and the existing phases were identified using electron diffraction X-ray analysis. The joints fail at the Au/Sn intermetallics at the chip carrier metallization or at the Cu/Sn compounds formed at the substrate thick film/solder interface. No deterioration of the overall joint strength due to Au/Sn intermetallics was seen, when the gold content in the joints was approximately 4 weight per cent.     

The effect of silicon dioxide content of natural stones on their strength properties,material removal rate and power consumption in diamond grinding

The paper addresses the influence of silicon dioxide content of natural stones on their Mohs hardness, ultimate uniaxial compression strength, microhardness as well as on the removal rate and power consumption in diamond grinding of these materials. An increase in the amount of this constituent in natural stones is demonstrated to have an effect on strength properties and power consumption in grinding and a considerable effect on removal rate in diamond grinding.     

高强度铸铁基cBN砂轮修整实验研究

消失模铸造制备的奥-贝球墨铸铁基cBN砂轮具有胎体强度高、胎体对磨粒把持力大等优点,但也存在着铸造砂轮毛坯尺寸精度不高、磨削层修整余量大、修整较为困难等不足之处.本文针对铸造铸铁基大粒度cBN砂轮毛坯,分别进行机械修整、电解修整和电解-机械-电解复合修整试验,探究不同修整方式下的最优工艺参数和修整效率,以及修整后磨粒的破碎和出刃情况.研究结果表明:采用Si C修整轮修整,当转速比为+0.3时修整效率最高,但修整效率随着时间的增加逐渐减小,修整至120 min才能够达到砂轮的目标精度;采用电解修整,砂轮在最优工艺参数下修整30 min后将产生钝化,电解修整难以继续进行;采用电解-机械-电解复合修整,不仅其修整效率比机械修整有所提高,而且砂轮表面磨粒破碎较少,磨粒出刃高度较大.     

Study on grinding of pre-sintered zirconia using diamond wheel

Zirconia-based ceramics are the most preferred materials used in implants due to their excellent mechanical properties compared with other alternatives. These materials available in the pre-sintered form are appropriate to grind due to their soft nature. However, it is challenging to achieve a required surface finish in grinding these ceramic materials owing to chipping, which limits its usage in industries. In this work, the pre-sintered yttria stabilized tetragonal zirconia (Y-TZP) component was ground using a resin-bonded diamond-grinding wheel under different cooling environments. The components ground under the minimum quantity lubrication conditions exhibited a reduced grinding force with better surface finish compared to wet (flood coolant) and dry conditions. The resultant specific energy was reduced with the increase in maximum chip thickness for different cooling conditions. The critical depth of cut estimated from the pre-sintered zirconia was witnessed to be higher, which indicated that the initiation of ductile to brittle transition occurred at a deeper depth of cut. The material removal mechanism observed in the pre-sintered zirconia was dominated by brittle fracture. This was evident from the obtained chips and ground surface morphology.     

低压下碱性铜抛光液对300mm多层铜布线平坦化的研究

随着微电子技术进一步发展,低k介质的引入使得铜的化学机械平坦化(CMP)须在低压下进行。提出了一种新型碱性铜抛光液,其不含常用的腐蚀抑制剂,并研究了其在低压下抛光及平坦化性能。静态条件下,铜的腐蚀速率较低仅为2nm/min。在低压10.34kPa时,铜的平均去除速率可达633.3nm/min,片内非均匀性(WIWNU)为2.44%。平坦化效率较高,8层铜布线平坦化结果表明,60s即可消去约794.6nm的高低差,且抛光后表面粗糙度低(0.178nm),表面状态好,结果表明此抛光液可用于多层铜布线的平坦化。     

MgO与Li2O摩尔比及烧结温度对结合剂及cBN磨具性能的影响

以ZnO-Na₂O-SiO₂-Al₂O₃-B₂O₃陶瓷体系为基础, 制备了添加不同摩尔比Li₂O和MgO的陶瓷结合剂及立方氮化硼(cBN)磨具。利用X衍射测试仪、线性热膨胀测试仪、扫描电镜等研究了MgO∶Li₂O摩尔比( M 值)和烧结温度对陶瓷结合剂及磨具性能的影响。结果表明: 随着 M 值增加, 结合剂的软化点温度增加, 耐火度及化学稳定性均增强, 线性热膨胀系数先增加后降低。当 M 值为0.67时, 随着烧结温度的升高, 石英晶相的析出被抑制, 诱导析出Mg(Zn)Al₂O₄晶相, 且含量逐渐增加, 尺寸先减小后增加; 当温度为870 ℃时, Mg(Zn)-Al₂O₄晶粒尺寸最小, 约为2 μm, 结合剂结构最为致密, 抗折强度达到最大值136.28 MPa。随着烧结温度的提高, cBN磨具气孔率和吸水率先降低后增加, 体积密度、硬度、抗折强度、磨耗比以及磨削效率先增加后降低; 当烧结温度为890 ℃, 磨耗比及磨削效率最高, 分别为98.72%和1.3675 g·min^-1。     

A new material platform of Si photonics for implementing architecture of dense wavelength division multiplexing on Si bulk wafer

Abstract

A new materials group to implement dense wavelength division multiplexing (DWDM) in Si photonics is proposed. A large thermo-optic (TO) coefficient of Si malfunctions multiplexer/demultiplexer (MUX/DEMUX) on a chip under thermal fluctuation, and thus DWDM implementation, has been one of the most challenging targets in Si photonics. The present study specifies an optical materials group for DWDM by a systematic survey of their TO coefficients and refractive indices. The group is classified as mid-index contrast optics (MiDex) materials, and non-stoichiometric silicon nitride (SiN_x) is chosen to demonstrate its significant thermal stability. The TO coefficient of non-stoichiometric SiN_x is precisely measured in the temperature range 24–76 °C using the SiN_x rings prepared by two methods: chemical vapor deposition (CVD) and physical vapor deposition (PVD). The CVD-SiN_x ring reveals nearly the same TO coefficient reported for stoichiometric CVD-Si₃N₄, while the value for the PVD-SiN_x ring is slightly higher. Both SiN_x rings lock their resonance frequencies within 100 GHz in this temperature range. Since CVD-SiN_x needs a high temperature annealing to reduce N–H bond absorption, it is concluded that PVD-SiN_x is suited as a MiDex material introduced in the CMOS back-end-of-line. Further stabilization is required, considering the crosstalk between two channels; a ‘silicone’ polymer is employed to compensate for the temperature fluctuation using its negative TO coefficient, called athermalization. This demonstrates that the resonance of these SiN_x rings is locked within 50 GHz at the same temperature range in the wavelength range 1460–1620 nm (the so-called S, C, and L bands in optical fiber communication networks). A further survey on the MiDex materials strongly suggests that Al₂O₃, Ga₂O₃ Ta₂O₅, HfO₂ and their alloys should provide even more stable platforms for DWDM implementation in MiDex photonics. It is discussed that the MiDex photonics will find various applications such as medical and environmental sensing and in-vehicle data-communication.     

沉底水雷目标强度预报

文章利用板块元方法和物理声学方法对界面附近目标的目标强度计算理论预报沉底水雷的目标强度。计算对比了无界面和淤泥界面附近水雷型目标的目标强度,为进一步研究界面附近水中复杂目标的目标强度提供了一种实用的方法。     

RNSS射频基带一体化芯片测试方法研究

随着卫星导航产业的快速发展,导航芯片成为民用卫星导航应用的核心竞争力。拥有诸多优势的射频基带一体化芯片是导航芯片发展的主流方向之一,本文依托某应用推广项目,对国产的该类芯片进行测试验证,通过不同模态下对其定位精度和跟踪灵敏度的考核,验证了芯片的基本功能,对该类芯片的测试方法进行了初步研究。     

An experimental investigation as to the effect of cutting parameters on roundness error and surface roughness in cylindrical grinding

This paper presents the results of an experimental investigation as to the effects of grinding parameters on roundness error and surface roughness in cylindrical grinding. Many variables including the wheel materials, wheel loading and dressing, workpiece metallurgy, work drive mechanisms, work holding methods, coolant types, feeds and speeds, machine stiffness and age, surface conditions, centre conditions, floor vibrations all influence the quality of ground parts. However, the composite sum of these grinding parameters creates static and dynamic forces. It is obvious that the roundness error and surface roughness are created by many parameters, but in this study, only the effects of the depth of cut, work speed and feed rate which create the grinding forces in cylindrical grinding are investigated. The grinding experiments were planned according to the principles of orthogonal arrays (OAs), developed by Taguchi, and were performed so as to understand the effects of these parameters on roundness error and surface roughness. The experimental data was analysed by using statistical tools: the percent contribution from an analysis of variance (ANOVA) and the correlation between machining parameters with roundness error (R) and also surface roughness (Ra). Roundness was found to be the most related with the cutting speed, grinding force and depth of cut, while surface roughness is related to feed rate and work speed.     

Jet mill grinding of portland cement,limestone, and fly ash: Impact on particle size,hydration rate,and strength

While the majority of commercial ordinary portland cement (OPC) is ground using a ball mill or a vertical roller mill, other industries have shown that jet mill grinding can be an alternative approach for grinding materials. This paper investigates the potential application of jet mill grinding for two systems. The first system is a blend of OPC and 15% limestone, and the second system is a blend of OPC and 40% fly ash. It was observed that when jet mill grinding is used, the average particle size of the powders is decreased to approximately 4 μm or less with a narrower particle size distribution than that achieved using ball milling. In addition to evaluating the size and shape of the particles obtained from the jet mill grinding process, this paper focuses on evaluating, using isothermal calorimetry, the effect these changes in particle size and distribution have on the extent and rate of hydration as well as their effect on the compressive strength of cement pastes or mortars.This study also investigated differences between inter-grinding and blending separately ground materials to form an OPC/limestone mixture. Both inter-ground and separately ground OPC/limestone mortars demonstrated an accelerated hydration at early ages accompanied by an increase in early age strength. This appears to be primarily due to the increased surface area of the finer particles that provides more available surface for the hydration reaction. The inter-grinding appeared to be more effective than grinding the materials separately because an improved graded particle size distribution was obtained. The inter-ground OPC/limestone mixture shows accelerated initial hydration at water to powder ratios (w/p, where powder = cement + limestone) of 0.50 and 0.35 when compared with the samples before grinding. At the lower w/p of 0.35, the OPC/limestone mixture appears much more efficient. In the OPC/fly ash mixture, jet mill grinding also accelerates the rate of hydration and strength development.     

高强度凝胶的制备方法研究

采用一种新方法合成了具有不同交联度的聚丙烯酸凝胶和聚2-丙烯酰胺基-2-甲基丙磺酸(PAMPS)凝胶．并对其力学性能及微观结构进行了研究。结果表明：二次凝胶比其一次凝胶压缩模量明显提高,且其模量随有效交联密度(ρx)增加呈线性增大。其中聚丙烯酸二次凝胶的剪切模量最大可提高2．3倍;PAMPS凝胶最大可提高5．5倍。对聚丙烯酸凝胶微观形态的研究发现这种二次凝胶具有更为紧密的微观结构。     

引气轻集料混凝土工作性和力学性能的研究

为配制高性能轻集料混凝土,研究了优质引气剂对大流动性轻集料混凝土的工作性及力学性能的影响规律.研究表明:引气剂对大流动性轻集料混凝土的坍落度的影响不大,对黏度影响较大;引气可减少离析、泌水及坍落度损失,明显改善轻集料混凝土拌合物的工作性能;一定范围内,引气对轻集料混凝土的力学性能有益;含气量小于5.5%时,抗压强度未降低,而是有所提高,提高幅度约3%～4%;含气量小于5.5%时,抗折强度提高,提高幅度约8%～10%.     

充水透声结构声目标强度预报方法研究

充水透声结构是水下航行体重要的结构类型之一,主动声呐作用于目标时,声波可以透射充水透声结构外表面进入结构内部,在充水透声壳体结构内表面产生内部散射,从而影响目标的目标强度.文章提出了一种适用于透声结构目标强度预报的考虑透声的修正板块元方法,此方法假设散射声场近似为内表面板块散射声场和与之对应的外表面板块散射声场叠加,基...     

磁控溅射法制备铁氧体薄膜的界面结合强度研究

利用磁控溅射法在单硅晶基底和玻璃基底上沉积铁氧体薄膜,采用AFM观察薄膜的微观形貌,采用划痕法测试薄膜的界面结合强度,测试结果表明:由于两种不同材质上沉积的薄膜粗糙度缘故,硅晶/铁氧体薄膜的临界载荷为19.7N,其划痕形貌为裂纹状扩展,玻璃/铁氧体薄膜的临界载荷为5.3N,其划痕形貌为剥落状。     

Influence of T-stress, cohesive strength and yield strength on the competition between decohesion and plastic flow in a crack edge vicinity

The discussion is based on the cell model of materials. Each cell contains one dominant kernel of micro-separation, for instance a particle. A cell is either in a cohesive or a decohesive state, the latter implying instability at load control. The process region consists of cells which have reached the decohesive state. The cells are characterized by their linear size and their cohesion-decohesion relation. The process region develops either in an elastic or in a plastic environment. In the latter case, it may be more or less deeply embedded in the plastic region. In some cases there will be no process region, only plastic flow. The ratio between the cohesive strength and the yield strength is an important parameter for describing this competition between decohesion and plastic flow, but the T-stress also plays a part. The fracture toughness depends on the area under the cohesion-decohesion curve and on the embedment of the process region.     

6016与H70板的冲压变形连接过程及剥离强度分析

对6016与H70板的冲压变形连接和剥离过程进行了物理实验和连续数值模拟,分析了不同模具与工艺参数对连接点颈部厚度、互锁及金属流动的影响.研究表明:随着凸模圆角半径(Rp)增大,颈厚值(Tn)增大,互锁值(Tu)减小;凹模深度(Hd)增大,Tn减小、Tu增加.底部厚度X取决于凸模下压量,过大底部材料流动不到位影响互锁,过小则底部太薄,推荐X取总板厚的25%.采用L型试样测剥离抗拉强度时应考虑加载力臂的影响.利用数值模拟可以预测连接强度,并为工艺与模具设计提供有效指导.     

制膜条件对聚丙烯中空纤维微孔膜强度的影响研究

用热致相分离法制备了聚丙烯中空纤维膜,研究了制膜过程中等规聚丙烯熔融指数、初始浓度以及凝固浴温度等因素对所制备膜强度的影响,提出了用热致相分离法制备等规聚丙烯中空纤维膜的适宜工艺条件.对影响合成高分子膜强度的各因素进行了分析和讨论.