Thin Film Transistor Liquid Crystal Display Production Research Articles

Using image analysis techniques to enhance TFT-LCD manufacturing yield through timely detection of PI alignment layer defects

This study aims to develop a solution to the manufacturing process defects of thin-film transistor liquid crystal display (TFT-LCD) panels. Specifically, it focuses on online image analysis for detecting uneven coatings of the polyimide (PI) alignment layers, which are crucial in the TFT-LCD manufacturing process. The PI solution is typically applied to a substrate surface using an array of nozzles via droplet deposition. During this process, nozzle clogging can cause a series of defects in the form of spots on the alignment layer. These defects impact the alignment of liquid crystal molecules in the TFT-LCD, leading to decreased display quality, reduced visibility, uneven brightness, and compromised image details. If suspected signs of alignment layer spots are identified, the image analysis technology assists online inspectors with prompt responses to minimize TFT-LCD production errors. The results of this study demonstrate timely detection of alignment layer spots, prevention of their progression, and significant reduction of the time required for manual inspection to improve manufacturing yield. This newly developed approach is applicable to not only TFT-LCD production monitoring but also smart display panel manufacturing, thereby providing significant value in high-volume and large-area panel fabrication processes.

A two-phase decoding genetic algorithm for TFT-LCD array photolithography stage scheduling problem with constrained waiting time

Abstract The thin-film-transistor liquid crystal display (TFT-LCD) array process is usually the longest process in TFT-LCD production. During the TFT-LCD array process, the scheduling problem of the photolithography stage entails complicated constraints such as photo mask availability, available machines for jobs, and limited waiting time. This study proposes a two-phase decoding genetic algorithm (TDGA) to maximize utilization in the photolithography stage, which is usually the bottleneck. An empirical study was conducted at a leading TFT-LCD manufacturing company. To compare the performance of the TDGA with other metaheuristics, eight scenarios were simulated based on the empirical data. The experimental results show the practical viability of the proposed TDGA.

Tutorial on Applying the VM Technology for TFT-LCD Manufacturing

In the high-tech industries, on-line quality monitoring on each workpiece under processing is required to ensure process stability and improve yield rate. However, conducting workpiece-by-workpiece actual metrology is very expensive and time-consuming. In this case, a novel idea is to use “virtual metrology” (VM) that conjectures workpiece quality based on process data collected from production equipment with a slight supplement of actual metrology data. The purpose of this tutorial paper is to select the thin film transistor-liquid crystal display (TFT-LCD) manufacturing processes as the illustrative examples for demonstrating the methodology of fab-wide implementation of the VM technology systematically. To begin with, a survey of VM-related literature is performed. Then, the features of an effective and refined VM system are presented with the automatic VM (AVM) system developed by the authors as a case study, followed by introduction of the TFT-LCD production tools and manufacturing processes. After that, the generic deployment schemes of the VM technology for the TFT-LCD tools are proposed. Finally, illustrative examples with the AVM system as a case study are presented to show how the VM technology applies to TFT-LCD manufacturing.

Quality Improvement in Cleaning Process for TFT-LCD Production

Thin Film Transistor Liquid Crystal Display (TFT-LCD) production pastes the polarizer onto glass panel using paste roller. TFT-LCD quality is affected by some inefficient cleaning work in polarizer pasting process to cause panel deface and leave residual glue behind in light leak. The clean processing becomes the key in quality assurance of TFT-LCD production. This paper adopts the Taguchi Experiment Method in experiment design and test to improve the G8.5 42＂ TFT-LCD production quality control. The affecting parameters concerning brush direction, speed, nip and conveyer speed are considered into the orthogonal array for experiments to find the best control adjustment. The objective of this study investigates the quality assurance in automatic TFT production. From production line tests, the production yield accomplishes 0.06% improvement of residual variation from 0.19% to 0.13%. It is significant improvement in TFT-LCD mass production.

TFT-LCD 제조 공정의 Slim MES를 위한 생산계획 프레임워크

본 논문에서는 TFT-LCD(Thin Film Transistor-Liquid Crystal Display) 제조 공정 중 Module 공정의 Slim MES(Manufacturing Execution System)를 위한 생산계획 프레임워크(framework)개발에 관해 연구한다. TFT-LCD 제조 공정 중 Module 공정의 라인 구성 및 기능은 각 제조 현장마다 차이가 있다. 본 논문은 이러한 차이를 반영하는 제조현장 맞춤형 MES를 위한 생산계획 프레임워크를 제시한다. 먼저 TFT-LCD Module 공정의 분석을 통해 생산계획 프로세스를 파악한다. 그런 다음 현장 상황 제약조건을 반영한 수리적 모델링을 제시하고 이에 대한 최적 스케줄의 도출을 사례를 통해 제시한다. 또한 현장 상황을 반영한 디스패칭(dispatching) 룰에 의한 스케줄 생성 과정을 제시하고 성능실험 결과를 제시한다. 마지막으로 Slim MES를 위한 생산계획 프레임워크 설계 과정을 제시한다. This paper presents a framework for production planning for a Slim MES(Manufacturing Execution System) of module operations in TFT-LCD(Thin Film Transistor-Liquid Crystal Display) production lines. There are differences in the line configurations and functions among the module operations in the TFT-LCD production systems. This paper presents the framework for the customized MES reflecting these differences. First, a production process is figured out through the analysis of the TFT-LCD module operations. Next, a mathematical modeling is presented reflecting the constraints of shop floors and an optimal schedule is presented through a case example. And a scheduling process using the dispatching rules reflecting the status of shop floors is presented and the performances are measured and compared. Finally, a design process for the Slim MES framework is presented.

A model for batch available-to-promise in order fulfillment processes for TFT-LCD production chains

The main purpose of this study is to explicitly highlight several special production characteristics in a thin-film transistor liquid crystal display (TFT-LCD) manufacturing industry and to present an available-to-promise (ATP) model that supports decision-making in order fulfillment processes for TFT-LCD manufacturing. A TFT-LCD production chain differs from others in its special production characteristics such as alternative bill-of-materials (BOMs), grade transition, etc., which are significant factors driving a success in an ATP implementation. Customers may specify a quality level and the materials to be used in a finished product in inquiry orders. The quality of the working-in-process can be altered using different assembled components. The ATP model enhances the responsiveness of order fulfillment processes. The ATP model directly links available material resources and capacity with inquiries or existing customer orders to improve the overall performance of the production chain. A case study using the model demonstrates the effectiveness and efficiency of the proposed ATP model in a TFT-LCD production chain and investigates the sensitivity of TFT-LCD plant performance to changes in order batching intervals.

Robust production and transportation planning in thin film transistor-liquid crystal display (TFT-LCD) industry under demand and price uncertainties

This paper studies the production and transportation control (PTC) problems under demand and price uncertainties in a multi-product, two-echelon, and hybrid thin film transistor-liquid crystal display (TFT-LCD) production chain. The unique characteristics of the TFT-LCD industry, including quality grades and alternative bill-of-materials (BOMs), are considered in this study. The objective is to determine a production and transportation policy that is robust to price and demand uncertainties. This two-echelon PTC problem is formulated as several two-stage robust optimisation models. An iterative procedure is developed to apply and solve these two-stage models in a TFT-LCD production chain. Our simulation study shows that the proposed method can significantly increase profits while reducing transportation and inventory costs. In addition to improving mean and variance of profits, we use several risk measures to verify the robustness of the iterative optimisation procedure.

An effective and efficient defect inspection system for TFT-LCD polarised films using adaptive thresholds and shape-based image analyses

Defect inspection of polarised films is a crucial process in TFT-LCD (thin film transistor–liquid crystal display) production. In this paper we propose a defect inspection system for TFT-LCD film images that detects film defects in a real-time production environment and classifies them based on the type of a defect. The proposed system is designed to locate defects promptly using an adaptive threshold technique and determines the defect type through image analysis using various features, such as the geometric characteristics and the shape descriptor with intensity distribution called the shape + ID descriptor. The experimental results using a set of test images obtained in a real production line are quite promising. Compared with existing methods, our method identifies defects effectively and efficiently enough to be used in a real-time environment. It also achieves a high correctness in classifying the defect type for various types of defects. In addition, it demonstrates robustness with respect to scale and rotational transformation.

Logistics lean integration strategies: case study of Samsung Electronics LCD inbound logistics

The electronics industry is a key industry in South Korea. To improve efficiency and maintain a competitive edge in fast-paced technological age it is critical to synchronize production supply with market demand. This paper focuses on the strategies which make the “just in time” production system within the electronic supply chain. The presented case study of Samsung Electronics Thin Film Transistor-Liquid Crystal Display (TFT-LCD) Inbound Logistics provides a solid example of process integration in the areas of: packaging, transportation and information sharing. The problems faced by Samsung Electronics in the early 2000’s were a direct result of an imbalance between increased traffic/demand and existing production capacity. The most detrimental of these problems caused delays in supply, shortage of space in the hub center and the bottlenecking of supply transportation. This paper demonstrates how Samsung Electronics reexamined and systematically streamlined their existing processes and how they successfully integrated “lean thinking” strategies to all areas of TFT-LCD production. As a result of the integration of these strategies, Samsung Electronics began using a line-to-line packing system which focused on packing items in a group using a standardized, returnable packing system. Additionally, they opted to replace their paper invoice system for an improved transportation system through which a data could reflect flows of information and materials in real time. The integration of these strategies gave Samsung Electronics a new approach to TFT-LCD Inbound Logistics which allowed them to overcome their dilemmas and resulted in successful outcomes, decreased lead times, higher quality products and an reduction in total costs.

Critical material planning for TFT-LCD production industry

This research focuses on the material planning problem in the thin-film transistor liquid crystal display (TFT-LCD) manufacturing industry. With the growth in TFT-LCD display applications, TFT-LCD manufacturing has become the new high-technology industry after semiconductor manufacturing. The final process of the TFT-LCD industry, the module process, is a material-oriented assembly production system that fabricates the panels produced from the preceding process and critical materials such as integrated circuit ( IC), printed circuit board ( PCB), and backlight ( BL) into customized TFT-LCD products according to different customer requirements. In addition, there are many specific characteristics such as alternative bill of material (ABOM), customer preference for ABOM, and purchase quantity ratio occurring in the TFT-LCD industry. However, because of the uniqueness of the TFT-LCD industry, material planning called critical material planning (CMP) must use a feasible and optimal purchase plan under these specific characteristics and constraints; also, the traditional material requirement planning (MRP) mechanism is no longer enough to deal with its planning problems. In response to this challenge, the current paper formulates a single-period and multi-period CMP problem as nonlinear programming models represented by the network graph. The purpose of this is to optimize the purchase quantity from suppliers while satisfying demand under the existence of specific characteristics. Additionally, we illustrate a numerical example from a real TFT-LCD manufacturer to clarify the multi-period CMP model; the managerial implications of the customer preference factors and the purchase quantity ratio are also correspondingly discussed.

Logistics lean integration strategies: case study of Samsung Electronics LCD inbound logistics

The electronics industry is a key industry in South Korea. To improve efficiency and maintain a competitive edge in fast-paced technological age it is critical to synchronize production supply with market demand. This paper focuses on the strategies which make the “just in time” production system within the electronic supply chain. The presented case study of Samsung Electronics Thin Film Transistor-Liquid Crystal Display (TFT-LCD) Inbound Logistics provides a solid example of process integration in the areas of: packaging, transportation and information sharing. The problems faced by Samsung Electronics in the early 2000‘s were a direct result of an imbalance between increased traffic/demand and existing production capacity. The most detrimental of these problems caused delays in supply, shortage of space in the hub center and the bottlenecking of supply transportation. This paper demonstrates how Samsung Electronics reexamined and systematically streamlined their existing processes and how they successfully integrated “lean thinking” strategies to all areas of TFT-LCD production. As a result of the integration of these strategies, Samsung Electronics began using a line-to-line packing system which focused on packing items in a group using a standardized, returnable packing system. Additionally, they opted to replace their paper invoice system for an improved transportation system through which a data could reflect flows of information and materials in real time. The integration of these strategies gave Samsung Electronics a new approach to TFT-LCD Inbound Logistics which allowed them to overcome their dilemmas and resulted in successful outcomes, decreased lead times, higher quality products and an reduction in total costs.