Fuzzy regression approach to modelling transfer moulding for microchip encapsulation

Transfer moulding is one of the popular processes to perform microchip encapsulation for electronic packages. Existing analytical models, such as generalised Hele–Shaw model, seem to be inadequate to model the process accurately in real world environment due to the complex inter-relationships among the encapsulant properties, process conditions, mould design parameters and overall moulding performance and the inherent fuzziness of the moulding systems. It is quite often that the observed values from the transfer moulding for microchip encapsulation may not be regular. Although statistical regression method could be used to perform the modelling, high degree of fuzziness inherent in transfer moulding systems for microchip encapsulation makes the obtained models having wide possibility range.

In this paper, the fuzzy regression concept and its application in modelling transfer moulding for microchip encapsulation are described. Fuzzy regression is a well-known method to deal with the problems with a high degree of fuzziness. Thirty-two experiments were firstly conducted based on an 2_iv⁸⁻² experimental plan in this study that involved eight process parameters and three quality characteristics. The experimental settings and results of the 30 experiments were then used to develop three fuzzy linear regression models, which relate various process parameters and the three quality characteristics, respectively. With the use of these models, proper process conditions and prediction range of individual quality measures can be obtained. Two validation tests were carried out to evaluate the developed models. Results of the tests show that the actual values of all the quality measures were found within the corresponding prediction ranges. The calculated prediction errors for the three output measures were all less than 5%.     

钻孔法中的残余应力场Ⅰ.理论分析

钻孔法测量残余应力时,由于切削力的作用,会在孔口附近产生加工硬化层。硬化层内材料的特性会发生明显变化,从而影响残余应力的释放。通过增大孔口附近区域材料的弹性模量的方式,将硬化层简化为一个异质圆环,利用弹性力学方法求得了无限大板在双向均布载荷作用下钻孔后的释放应力的解析解。应用有限元软件MSC／Patran ＆ Nastran,对304不锈钢板在二向应力状态下的释放应力进行了数值计算,并与文中的解析解进行了比较。结果表明,将硬化层简化为异质圆环的分析模型是有效的,文中推导的解析解是正确的,钻孔法测量残余应力时考虑硬化层的影响会有助于提高测量精度。     

Structural analysis and optimisation of press brakes

A model of the bending process in Press Brakes is established using Timoshenko beam theory. Expressions for the workpiece bending error are derived that explicitly consider the influence of shape, dimensions and initial deformation of the machine structural components on its bending accuracy. The minimization of the bending error is formulated in terms of optimisation problems that are solved numerically using a genetic algorithm. The methodology presented in this paper permits the analysis of existing Press Brake design solutions, the optimisation of their performance and the development of new solutions.     

Riveted assembly modelling: Study and numerical characterisation of a riveting process

In the field of structural stress analysis and especially in transitory dynamics (crash and impact simulations), study/design accuracy requires increasingly predictive models. A compromise between cost and precision entails modelling and simplification of all the link elements. Riveting is a particularly sensitive case. The characteristics needed to ensure effective modelling are indeed difficult to measure. This paper presents adjustment of a numerical model simulating a riveted link using a number of different approaches. The results analysis considerably improve knowledge about the riveting process and behaviour of riveted links. This study will pave the way for resistance tests to be conducted in order to numerically characterise riveted links under load. The aim is to develop an approach that reduces the model size and calculation time without adversely affecting the validity of the simulation results, and to show the effect of strains and residual stresses on the link in post-riveting.     

基于PLC的液位模糊自适应PID控制研究与应用

将模糊控制器与PID控制器结合起来,选取合适的隶属度函数和模糊控制规则,分析输入变量的量化因子和输出变量的比例因子在模糊控制系统中对系统性能的影响,离线计算出模糊控制规则表,利用S7-300 PLC设计一个液位模糊PID控制器。在单容水箱进行实际液位控制实验,并用WinCC对系统进行监控。实验结果表明:采用模糊PID控制水箱液位,系统具有良好的动静态性能。     

Dimensional accuracy optimisation of multi-stage planetary EDM

The use of multi-stage planetary EDM is the best option when it comes to the reduction of the machining time required to achieve the specifications of dimensional accuracy and surface finish of an EDM operation. Furthermore, this strategy allows the user to reduce costs by reducing the number of electrodes required to complete the operation. However, it is not always easy to optimize the design of this kind of operation due to the large number of parameters involved. This is especially so in the case of dimensional accuracy, which is influenced by the different error sources present during the process.

In this work, the validity of different multi-stage planetary EDM strategies is assessed from the point of view of machining time and surface finish. However, the optimum choice under those criteria does not assure that dimensional accuracy requirements are met. Thus, the different error sources are analyzed, paying most attention to thermally induced errors, which are numerically simulated from experimental data collected during the process.     

Hot Deformation Behavior of a New Nuclear Use Reduced Activation Ferritic/Martensitic Steel

The hot deformation behavior and workability of a new reduced activation ferritic/martensitic steel named SIMP steel for accelerator-driven system were studied.The flow curve and its microstructure were studied at 900-1200℃ and strain rate range of 0.001-10 s~(-1).The results showed that the deformation behavior of the SIMP steel during hot compression could be manifested by the Zener-Hollomon parameter in an exponent-type equation.Based on the obtained constitutive equation,the calculated flow stresses were in agreement with the experimentally measured ones,and the average activity energies QDRV and QHW for the initiation of dynamic recrystallization and the peak strain were calculated to be 476.1 kJ/mol and 462.7 kJ/mol,respectively.Furthermore,based on the processing maps and microstructure evolution,the optimum processing condition for the SIMP steel was determined to be 1050-1200 ℃/0.001-0.1 s~(-1).     

压弯量对轧件矫直变形影响的有限元分析

采用显式动力学有限元软件ANSYS/LS-DYNA分析了中厚板在热矫直时,不同压弯量对轧件矫直变形的影响。模拟结果表明,入口压弯量在达到一定程度(即塑性比拐点)时,入口处轧件塑性变形区沿长度方向扩展迅速,而沿厚度方向增加缓慢,此时矫直效率降低;对厚度不同的轧件,随着厚度的增加,塑性比拐点出现较晚;另外塑性比拐点以下,使塑性比达60%~85%的入口压弯量引起的残余应力值变化不大,只是残余应力分布状况不同,而当入口压弯量超过塑性比拐点时,轧件的残余应力在某些区域则发生较大变化。该模拟结果对确定中厚板热矫直模型,掌握矫直变形规律具有一定的指导意义。     

浅谈电气控制工艺设计

电气控制工艺设计包括总体配置设计，元件布置图的设计与绘制，电器部件接线图的绘制，电气控制柜及非标准零件图的设计等工作。     

Structure optimisation of metallic load introduction elements embedded in CFRP

The combination of construction parts made of fibre-reinforced plastics (FRP) and metal holds great lightweight design potential but places high demands on the necessary joining technologies. Metallic load introduction elements that are embedded in the manufacturing process of FRP components are a promising joining technology. In order to fully exploit the potential of this technology, approaches to increase the load bearing capacity of inserts, particularly under pull-out loads, have been missing. The aim is therefore to derive a method for the simulative structural optimisation of embedded inserts. The load bearing capacity increases under pull-out loads through smoothing of failure-critical stress peaks using the optimisation of the thickness distribution of the insert’s base plate. The increase of the load bearing capacity of the optimised insert geometry is confirmed through experimental validation.     

基于Pro/E的镶嵌玻璃板注塑模具的设计

以冰箱面板零件为载体,介绍了镶嵌有玻璃板的注塑件基于Pro/E的模具设计,模具的结构特点和注塑中的特点。镶嵌有玻璃板的注塑件注塑模具,其主要特征是玻璃板的放置和定位方法与结构特征,以及模具设计中的0收缩率设定。采用此结构的镶嵌有玻璃板的注塑模具在生产中能保证质量。     

Investigation of lubrication effect on the backward extrusion of thin-walled rectangular aluminum case with large aspect ratio

Backward extrusion processes are being increasingly considered for the manufacture of thin-walled rectangular aluminum case with large aspect ratio in lieu of multi-stage deep drawing processes. In order to design an optimized backward extrusion process, it is necessary to determine optimal frictional conditions by studying the effects of lubrication.

In this study, numerical analysis based on the finite volume method is performed for investigating the effects of solid lubricants in aluminum backward extrusion processes. Various shear friction factors are used in the numerical study for investigating the friction effects.

Lubrication is found to have a significant effect on the final shape. Larger friction factors are associated with increased forming heights on the wide side of the rectangular container and decreased forming heights on the narrow side. Lubrication is also found to have a significant effect on earing phenomena and a friction factor of 0.2 is found to be optimal for minimizing it. The analysis results presented herein are further validated by comparing them with experimental results.     

Optimal Design of Co/In/Cu Sputtering Target Assembly Using Finite Element Method and Taguchi Method

Target assembly is a key consumable material for producing thin fi lm used in the electronic packaging and devices. The residual stresses induced during the process of soldering are detrimental to the performance of target assembly. In this work, the intensity and distribution of the soldering residual stress of Co/In/Cu target assembly subjected to a 20 W/(m~2 K) cooling condition corresponding to the actual air cooling process were studied, based on fi nite element simulation and Taguchi method, to optimize the sputtering target assembly. Effects of different control factors, including solder material, thickness of solder layer, target and backing plate, on the soldering residual stress of target assembly are investigated. The maximum residual stress is calculated as 9.28 MPa in the target located at 0.16 mm from target–solder layer interface and at a distance of 0.78 mm from symmetry axis. The optimal design in target assembly has the combination of indium solder material, cobalt target at 12 mm thick, solder layer at 0.8 mm thick, copper backing plate at 15 mm thick. Moreover, solder material is the most important factor among control factors in the target assembly.     

基于温度控制系统的模糊自整定PID算法设计

考虑到温度的控制特性,以及常规PID控制器参数整定方法不能获得满意控制性能的问题,提出了一种基于模糊自整定参数的PID算法.针对隶属度函数对模糊推理模型的精度影响和控制算法的特点,建立了模糊PID控制参数规则调整表.该方法不仅具有模糊控制的动态性能好、上升时间快和超调小的特点,而且具有PID控制器的鲁捧性好、动态跟踪品质高和稳态精度高的特性.结合实际的温度控制系统,对水的三相点、沸点以及水温进行了测试与控制,得到了实际控制的温度教据.     

Application of the LCR ultrasonic technique for evaluation of post-weld heat treatment in steel plates

Ultrasonic travel times obtained with the LcR wave are able to distinguish between stress relieved and non-stress relieved 13 mm (1/2 in) thick, steel plates. Two 1.22 m (48 in) square plates were patch welded in the centre to create a residual stress field, and one of the plates was stress relieved. The LcR ultrasonic technique sends a critically refracted longitudinal wave travelling beneath the plate surface, and the stresses in the plate affect the travel times through the acoustoelastic relationship. The L_CR travel-time measurements not only distinguished between residual stress states in the plate, but also gave some information on their distribution and magnitude. Neither texture nor localized residual stresses affect the results. These findings demonstrate the potential usefulness of the technique for evaluating the state of post-weld heat treatment in structural steels.     

Some experimental data on workability of aluminium-particulate-reinforced metal matrix composites

The workability of aluminium–SiC and Al₂O₃-reinforced metal matrix composites (APMMCs) prepared by stir-casting, squeeze-casting and powder metallurgy techniques has been studied by using up-set test. Different parameters of APMMC were considered such as type of Al matrix alloy, type of particulate reinforcement and particulate volume fraction and size. The up-set test was conducted on cylindrical specimens with 8 mm diameter and 8 mm height, successively as repeated compressions with intermediate heat treatment (IHT).

Generally, the workability index (WI) has been positively affected by decreasing particulate size and volume fraction (V_f). Stir casting resulted in a slightly better workability than that obtained in case of powder metallurgy, while squeeze casting showed promising behavior in the case of composites with high-particulate V_f.

The highest workability index (WI), was obtained in case of APMMC with wrought Al matrix and SiC reinforcement. Some rolling experiments were additionally conducted on such composite, where WI estimated was compared to that of the up-set tests.     

Fuzzy neural networks for arc welding quality control

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中厚板多孔位大型冲孔模设计

介绍了以汽车车架纵梁冲孔模为代表的中厚板、多孔位、大型冲孔模的结构特点、所采用的降低冲裁力的措施以及此类大型冲孔模的设计共性问题和设计要点。     

某轿车C柱内板冲压分析与成形模设计

C柱内板是轿车中重要的结构件,冲压变形复杂。首先,对C柱内板零件进行冲压成形分析,确定其成形方案和成形毛坯。在三维计算模型基础上,采用Autoform软件对零件的成形进行数值模拟,得出零件的成形极限图。根据数值模拟结果,分析零件整体成形性能、材料变薄率,预测C柱内板成形过程中的起皱、拉裂等冲压缺陷,结果表明,零件整体成形到位,材料局部位置变薄超过20%,有拉裂危险。其次,基于UG和CAD软件设计了成形模具的上模、压边圈和下模。最后,通过生产实践压制出合格的C柱内板零件,验证了冲压分析的合理性和模具设计的正确性。     

考虑模糊失效准则的机床主轴刚度可靠性分析

将许用挠度看作模糊变量,将载荷、材料参数、几何尺寸等不确定因素视为随机变量,提出了考虑模糊失效准则的机床主轴刚度靠性分析模型。给出了机床主轴模糊失效的几何意义,推导了其隶属度函数。利用Gauss-Hermite积分,建立了机床主轴模糊可靠性的数值计算方法。数值算例表明,该方法不仅有效地减少了计算量,精度高,而且与实际情况更接近,计算结果更为保守。