Effects of Four Key Process Variables on Size Shrinkages of Low Temperature Co-Fired Ceramic Substrates

The effects of four key process variables on the size shrinkages of low temperature co-fired ceramic substrates were investigated using the methods of design of experiments (DOE), analysis of variance (ANOVA), and multivariable regression. The process variables investigated were raw tape thickness, laminating pressure, coining pressure, and coining time. The results revealed that coining pressure had the most significant effect on the size shrinkages of the low temperature co-fired ceramic samples under the process conditions set in this study. The average lateral size shrinkage and thickness shrinkage of the LTCC samples produced with a coining pressure of 320 MPa were significantly lower and higher than those produced with a coining pressure of 50 MPa with shrinkage differences of 3.6% and 6.2%, respectively. The effects of tape thickness, the interaction of tape thickness, laminating pressure, and coining pressure, the interaction of tape thickness and coining pressure, and the interaction of tape thickness and laminating pressure were also significant. Two regression equations were obtained and the shrinkage values could be estimated using them. The coefficients of determination R² were 99.9% and 98.9%, respectively, and the P values were smaller than 0.001 for the two regression equations. This can allow engineers to calculate the dimensions especially lateral dimensions and features such as pad pitches at the design stage and to set the process parameters at the manufacturing stage.     

1Cr13不锈钢静叶片精压工艺研究

本文对径向挤压成形的汽轮机静叶片进行了精压工艺研究。设计、制作了一套热精压模具、进行了工艺试验，精压后的零件达到了预期的要求。     

Development of an industrial process for minting a new type of bimetallic coin

This paper introduces a technology for minting a new type of bimetallic coin. The coin is manufactured from two metal disks of different materials, one being very thin, joined together by mechanical means during the impartion of the surface details by the minting dies. The proposed technology is based on a multi-stage process consisting of three cold metal forming operations (preforming, rimming and coining) and one intermediate annealing before the coining operation.

The main objective of this work is to present the theoretical and experimental results obtained during the development of the process, which are essential for producing this new type of bimetallic coin. The theoretical analysis was based on the utilization of the finite-element method to characterize metal flow, to establish the process sequence and related intermediate disk geometries, and to design an appropriate geometry for the mechanical joint between the two metal disks.

Experiments consisted on the coinage of several bimetallic prototypes in order to confirm the theoretical predictions and to validate the new proposed technology, which latter can be seen as an alternative to the existing bimetallic coin technology based on the utilization of an outer ring and a central disk.     

Metal direct nanoimprinting for photonics

In this paper metal direct nanoimprinting (embossing) for the production of metallic microparts is discussed, with a main focus on its suitability for the fabrication of metal-containing optical devices such as photonic crystals, plasmon waveguides or chiral structures. Silver and gold were chosen, since they have the lowest light absorption in the near infrared and visible range. They are also easily formable due to their good ductility, which can be further enhanced by processing at elevated temperature. The mold material, which may form part of the optical device, usually consisted of silicon, but other dielectric materials such as silicon oxide and silicon nitride were also successfully tested.Cylindrical and line-shaped holes with lateral dimensions down to 250 nm and aspect ratios of up to 5 were etched in silicon wafers. All the structures were successfully filled with silver and gold, and the filling of smaller dimensions is also deemed possible. This technique is therefore suitable for producing metal-containing optical devices working in the infrared, at least down to the standard telecom wavelength of 1.5 μm, which requires metallic dimensions of 200-300 nm.     

Effects of Key Process Conditions on Warpage and Via Protrusion of LTCC Substrate

The effects of key process conditions on the protrusion of via conductors and warpage of low temperature co-fired ceramic (LTCC) substrates were investigated using the design of experiments and analysis of variance. The results revealed that tape thickness, via size and coining pressure had highly significant effects and the interaction of via size and coining pressure had a significant effect on the via protrusion heights of the LTCC samples. A combination of via size of 0.12 mm, raw tape thickness of 0.254 mm and coining pressure of 50 MPa produced minimized protrusion. Tape thickness, coining pressure and the interaction of them had highly significant effects on the warpage of the LTCC samples. A combination of tape thickness of 0.127 mm and coining pressure of 50 MPa produced minimized warpage. A combination of the factor settings was also recommended for obtaining low heights of both protrusion and warpage.     

钢铁产品点阵式打印机字符高度变换研究

在分析钢铁产品点阵式打印机字符高度变换原理的基础上 ,导出了与字符高度有关的各种因素及其相互关系 ,引入了字符高度变换系数的概念 ,提出了限制条件 ,为打印头设计和字符成型控制奠定了理论基础     

Prediction and elimination of springback in straight flanging using computer-aided design methods: Part 2: FEM predictions and tool design

Part 1 of this two-part paper presents the laboratory experiments on straight flanging, in which the influence of process variables, such as die shoulder radius, punch-die clearance, punch nose radius, pad force and material properties were discussed. This second part summarizes the FEM predictions for flanging and compares these results with some experimental data. Furthermore, flanging with coining to reduce springback has been investigated and evaluated by FEM for better dimensional control in flanging and hemming processes.     

金刚石印压微孔工艺参数优化分析

为提高室温金刚石纳米印压铜片所得微孔的质量,减少微裂纹以及获得孔径更小的微孔,提出加热辅助印压新工艺方法,借助加热影响铜片的组织与性能,改善成孔效果。建立微孔边缘裂纹与工件晶粒微观组织、金刚石压头和加热温度之间关系,并对这三方面进行分析,通过DEFORM软件对印压微孔进行模拟,并结合实验研究,对加热印压纯铜动态再结晶细化晶粒进行分析,确定了加热印压最佳工艺参数。结果表明：加热印压微孔时最佳成形温度为200 ℃,最佳下压速率为0.01 mm/s。     

A multi-region model for numerical simulation of micro bulk forming

Due to the small billet size in micro forming, each grain, especially that on the surface layer, has direct influence on the deformation behavior of the billet. The multi-region model was proposed for simulating the micro bulk forming process in this paper. The object in the model is divided into three different regions: the inner polycrystal region, the grain interior of the surface region and the grain-boundary layer in the surface region. Each surface grain has different orientation. Depending on the Hall-Petch formula, which is applicable to describe polycrystal materials, and introducing scale parameters, the constitutive equation of each region is deduced based on the unidirectional compression tests data of the copper specimen. Using the multi-region model, the coining process with micro feature is simulated to investigate the size effect in micro forming. Moreover, an experiment of coining process with micro-feature is performed to verify the correctness of the multi-region simulation model. The experimental results show a good agreement with those in numerical simulation.