半导体生产线动态调度方法研究

为了满足半导体生产线多目标优化要求,提出了多目标优化动态调度规则。它由正常状态调度规则、瓶颈设备较低在制品水平的调度规则、非瓶颈设备较高在制品水平的调度规则、多批加工设备调度规则以及紧急工件调度规则五种类型的调度规则组成。使用具有半导体生产线本质特征的简化模型,将多目标优化动态调度规则与先入先出法、最早交货期法、临界值法进行了比较,结果表明,多目标优化动态调度规则能够改善半导体生产线的整体性能,更好地优化模型的生产率、加工周期与在制品水平,最终提高准时交货率。     

Work-in-process scheduling by evolutionary tuned fuzzy controllers

In this paper, an evolutionary algorithm (EA) strategy for the optimization of generic work-in-process (WIP) scheduling fuzzy controllers is presented. The EA strategy is used to tune a set of fuzzy control modules that are used for distributed and supervisory WIP scheduling. The distributed controllers objective is to control the rate in each production stage in a way that satisfies the demand for final products while reducing WIP within the production system. The EA identifies those sets of parameters for which the fuzzy controller performs optimal with respect to WIP and backlog minimization. The proposed EA strategy is compared with known heuristically tuned distributed and supervised fuzzy control approaches. Extensive simulation results show that the EA strategy significantly improves the system’s performance.     

Flexibility analysis of a surface mount technology electronic assembly plant: An integrated model using simulation

This paper focuses on developing an integrated model using simulation to evaluate the effect of several independent variables on the performance of a surface mount technology (SMT) production line. Real data and an existing SMT line from a high product mix/low volume electronics manufacturer are used to conduct the analysis. The independent variables used are set-up formation policies (group technology based family grouping methods), machine feeder types, similarity factor in set-up formation, parts reduction at design step of products, and inter-families and intra-family scheduling rules. In addition, a new method of grouping products is proposed. The measures of performance evaluated by the model are average lead time, average work-in-process (WIP) inventory and average set-up time. Data analysis shows that the proposed method of grouping products will reduce set-up time and lead time while slightly increasing WIP. The proposed simulation model helps assess the effects of some of the independent variables on line performance. Recommendations are made in order to help the user choose the best alternative to improve production line productivity and flexibility.     

Job releasing and throughput planning for wafer fabrication under demand fluctuating make-to-stock environment

In the semiconductor industry, dynamic changes in demand force companies changing the product mix makes the production planning challenging. This paper aims at an environment where product mix changes periodically and presents a production scheduling system to plan the wafer lot release and throughput. The proposed system is designed on the make-to-stock basis with the objective of meeting demand forecast while maintaining production smoothness. Two modules are included in the system. Preliminary analysis module analyzes throughput and cycle time distributions for different product mixes so as to determine relative parameters to be used as the inputs to the job releasing plan. In the production scheduling module, with the considerations of the attainment of demand forecast, production smoothness, and commitment of the due dates of the released job orders, the job release schedule and completion time table are prepared. A simulation model of a semiconductor fab is used as the base case to demonstrate the effectiveness and efficiency of the proposed system.     

半导体生产线全局修正式重调度方法研究

基于群体智能思想,提出了全局修正式半导体生产线重调度方法。首先,给出了基于群体智能思想的重调度模型;然后,在此模型基础上,给出了全局修正式重调度算法;最后,基于实际生产线的仿真模型对全局修正式重调度算法与企业原有算法进行了对比分析。仿真结果表明,在不确定的半导体生产线环境下,在适当的时候使用全局修正式重调度算法生成重调度方案,能够更好地优化模型的在制品移动次数、在制品移动速率与工件操作准时交货率等短期性能指标。目前,该方法已在某实际半导体生产线中应用并取得了良好的效果。     

瓶颈工序影响下汽车电子生产车间排程研究

针对汽车电子生产车间作业排产面临的在制品(Work In Process,WIP)堆积、生产周期长和订单准时交付率低等问题,梳理汽车电子零/部件生产车间排程逻辑,依托于约束理论(Theory Of Constraint,TOC)和“鼓-缓冲-绳子”(Drum-Buffer-Rope,DBR)方法,识别瓶颈工序,以完工期限最早优先(Earliest Due Date,EDD)和提高产出率为原则,引入交付紧迫系数,建立了瓶颈工序影响下的订单优先排产计划模型。以某汽车电子零/部件企业的印刷线路板(PCBA)生产车间实际生产数据为例,结合订单优先排产计划模型对PCBA订单进行作业时间排程,验证了该模型的有效性,为汽车电子生产车间排程提供了一种新的可行方案。     

基于Flexsim的某半导体制造企业人机比建模与分析

介绍了Flexsim仿真软件的建模流程以及人机比分析研究过程,通过利用一个半导体制造企业生产现场仿真建模的例子,阐明了人机比分析在生产现场中的应用.首先利用Flexsim对某半导体制造企业生产现场进行仿真建模,然后通过对仿真得到的机器利用率、人员利用率以及产量这三个数据的分析,得出最佳人机比,从而为管理人员安排人员生产、提高生产效率提供有力的数据支撑.同时模型具有通用性,当产品发生变化或生产流程改进后,只需要通过更新参数设置即可得出最佳人机比.     

SWARM INTELLIGENCE BASED DYNAMIC REAL-TIME SCHEDULING APPROACH FOR SEMICONDUCTOR WAFER FAB

Based on the analysis of collective activities of ant colonies, the typical example of swarm intelligence, a new approach to construct swarm intelligence based multi-agent-system (SMAS) for dynamic real-time scheduling for semiconductor wafer fab is proposed. The relevant algorithm, pheromone-based dynamic real-time scheduling algorithm (PBDR), is given. MIMAC test bed data set mini-fab is used to compare PBDR with FIFO (first in first out), SRPT(shortest remaining processing time) and CR(critical ratio) under three different release rules, i.e. deterministic rule, Poisson rule and CONWIP (constant WIP). It is shown that PBDR is prior to FIFO, SRPT and CR with better performance of cycle time, throughput, and on-time delivery, especially for on-time delivery performance.     

Single machine scheduling with multiple objectives in semiconductor manufacturing

To deal with today’s stiff competition in the logistics of semiconductor manufacturing, the development of an efficient scheduling approach for the complex semiconductor back-end testing operations is very essential, where more than one objective, such as cycle time, machine utilization and due date accuracy are kept in the focus to various degrees simultaneously. In this paper, the problem of scheduling N independent jobs on a single testing machine with due dates and sequence-dependent setup times is addressed, where the multiple objectives are to minimize average cycle time and average tardiness and to maximize machine utilization. A near optimal solution, which is not inferior to any other feasible solution in terms of all objectives, is generated combining the analytically optimal and conjunctive simulated scheduling approach. First, the machine-scheduling problem is modeled using the discrete event simulation approach and the problem is divided into simulation clock-based lot selection sub-problems. Then, at each decision instance in simulated time, a Pareto optimal lot is selected using the compromise programming technique for multi-objective optimization. With the help of a broad experimental design, this developed solution is then compared with common heuristic-dispatching rules used in industry such as the shortest processing time (SPT) and earliest due date (EDD). The developed scheduling method shows better results for all the objectives over a wide range of problems. It shows approximately 16.7% reduction in average cycle time, 25.6% reduction in average tardiness, and 21.6% improvement in machine utilization over the common dispatching rules, SPT and EDD.     

Robust production control policies considering WIP balance and setup time in a semiconductor fabrication line

This paper discusses the problem of determining workload in a semiconductor fabrication line for providing robust production control. A mathematical model is proposed to determine the amount of wafers to be processed on equipment in a photolithography process where the setup time is incurred if the type of wafers is changed on the equipment. The objective of the model is to control the fabrication line by maintaining the target work-in-process (WIP) level as close as possible for the purpose of short cycle time and by minimizing the setup time loss for maximal throughput. The proposed model is formulated using mixed integer programming (MIP) to minimize the weighted sum of two objective functions. A heuristic approach is suggested using linear relaxation and its adjustment. Performances are evaluated for the optimal solution with computational cost and for the heuristics. It is shown that the heuristics give good solutions which are 10% away, on average, from the optimal solution, but which can be obtained in a few seconds.     

Heuristic scheduling policies for a semiconductor wafer fabrication facility: minimizing variation of cycle times

This paper presents heuristic scheduling policies for semiconductor wafer fabrication facilities. The proposed heuristic scheduling policies include the advanced operation due date (OPNDD) for a sequence control policy and the adaptive constant work-in-process (CONWIP) for an input release control policy. The objective of the proposed scheduling policies is to reduce the variation of cycle times in the wafer fab. The advanced OPNDD sets the higher priority to the front opening unified pod (FOUP) with the smallest operation due date that is computed using a generalized stochastic Petri net model, and at the same time regulates the queue lengths of the FOUPs in each stoker by preventing excessive queue lengths in bottleneck workstations. The adaptive CONWIP controls dynamically the input release time of FOUPs using the adaptive WIP level according to the current status of the wafer fab. The simulation experiments show that the proposed scheduling method is efficient in reducing the variation of cycle times.     

Development and evaluation of feature-focused dynamic routing policy

This paper reports on a development of feature-focused dynamic routing policy and its evaluation in a flexible manufacturing systems (FMS) simulation framework. The dynamic policy is based on an integrative methodology in which process planning system IMPlanner is integrated with FMS simulation module. IMPlanner’s rule-based system process selection system performs knowledge-intensive task of generating alternative processing options for each feature for parts in production plan. Generated alternative routings (process plan network) for each part are utilized in the FMS simulation module such that routing decision in FMS are made on periodic intervals by considering alternative processes for each feature and making decision based on the current system status and performance. The proposed framework has been evaluated in an experimental FMS simulation module, implemented in Arena, in which two performance criteria, machine utilization and WIP, were used to make routing decisions. The feature-focused approach is compared with traditional static decision-making, and its improved performance is demonstrated.     

基于JIT的加工和装配计划集成方法及其应用

针对订单生产型企业JIT准时供货的要求,建立了加工和装配计划集成模型,该模型的目标函数是为了保证产品交货期的要求;为保证计划的可行性,约束函数包括加工能力约束、装配能力约束、加工和装配顺序约束;模型为两层混合规划模型,运用了遗传算法和启发式规则,提出了混合启发式算法。最后,针对某按订单制造型企业进行了实例应用,对产品制造过程进行了分解,采用先由装配计划得出各工件的交货期,然后根据工件的交货期确定工件的加工和装配计划。     

并行传送带式摩托车流水线调度模型与求解

针对一类摩托车制造柔性流水线中的调度问题,提出一种考虑工位差异的并行传送带式流水线调度模型。考虑不同在制品在生产线上不同工位的不同最大加工速度对传送带速度的影响因素,引入射频识别技术实时采集线上在制品的信息,通过及时调整传送带速度提高生产效率;根据生产实际需求,在生产线上不同种类在制品之间插入调整间隔,为更换车型提供准备时间。在此基础上,考虑模型以最小化最大完工时间为目标,采用基于极坐标编码的改进人工鱼群算法进行求解,说明了求解过程中的编码方法、母体迭代方式、人工鱼个体距离等关键技术。通过某摩托车生产企业的实际生产数据验证了该模型的有效性。     

串行生产线生产率的最优控制

基于计时Petri网和极大代数理论构建了串行生产线的稳态方程,并对其进行了周期分析。以此为基础,建立了串行生产线生产率控制模型。应用变分法求解模型,并在Matlab平台上对模型进行了仿真运算。结果表明,在满足生产工艺要求的前提下,要保证生产线的高生产率,生产线上瓶颈工作站的位置应尽量靠近生产线尾端;生产线上各工作站的生产率应呈依次下降的趋势;每个缓冲区理想的在制品库存量应尽量接近其初始库存量。在进行串行生产线设计时,这些结论具有实际参考价值。     

基于物联网技术的航空复合材料在制品跟踪管理系统研究

首先对航空复合材料在制品跟踪现状和物联网技术的概念进行了阐述,对条形码和射频识别2种数据采集方式优缺点进行了对比,提出了采用条形码和射频识别相融合的在制品跟踪方法,其次对航空复合材料生产流程及特点进行了分析,构建了基于物联网技术的复合材料在制品跟踪系统硬件结构和系统软件结构,最后就系统实现的关键策略进行了相关说明,并对系统进行了实例验证。     

面向代理的半导体生产线建模技术研究

为了有效分析和评价基于多代理的半导体生产线调度与控制性能,提出了面向代理的有色赋时Petri网的半导体生产线建模方法。将设备代理内部行为进行封装,建立了设备代理的有色赋时Petri网模型。同时,将半导体生产线多代理模型按层次划分为设备代理层、设备组层和系统层,有效地降低了模型的复杂性,提高了模型的可重用性。建立了分布式半导体生产线仿真平台,以实现基于面向代理的着色赋时Petri网的半导体生产线仿真定量分析与评价。以上海某半导体制造企业6英寸晶圆生产线为例,其仿真结果验证了建模与仿真的有效性。     

Data acquisition system of compound semiconductor fabrication

Though compound semiconductor manufacturing technologies are very much similar to those of the silicon series memory devices, the production process control technologies tend to rely on the experiences of operators and managers because the production technology suitable for the characteristics of compound semiconductor fabrication has not yet been sufficiently developed, compared with that of silicon semiconductors. In addition, the semiconductor industry is being converted into mass customization production and an open foundry service for cooperation between businesses. In this study, a process data acquisition system suitable for compound semiconductors which collects data by operator input and equipment information extraction by using GEM was developed. The developed system was implemented in a real production system and compared with the conventional job card method. Through the application of the developed system, a foundation for constructing a real-time based MES (Manufacturing Execution System) was developed, with such expected effects as process information monitoring, meeting delivery schedule, and reducing lead-time.     

基于EM-PLANT的某制造企业设施布局仿真研究

利用EM_PIANT软件将原有生产设施布局和优化后的布局分别建立仿真模型并运行,分析仿真模型的运行状况及结果.通过生产设施布局的仿真参数得到平均生产周期、总物流量、组装线稼动率、搬运车稼动率、WIP等指标,再做出统计分析.最终对生产系统不同布局的优劣状况做出评价.选择合理布局方案.为生产设施布局优化问题提出一种有效、直观的解决途径.