Diagnosis of systematic defects based on design-for-manufacturability guidelines

All products in the Very-Large-Scale-Integrated-Circuit (VLSIC) industry go through three major stages of production - Design, Verification and Manufacturing. Unfortunately, neither of these stages are truly perfect, hence we need two more sub-stages of manufacturing, namely Testing and Defect Diagnosis to prevent imperfections in ICs. Testing is used to generate test vectors to validate the functionality of the Device-under-Test (DUT), and Defect Diagnosis is the process of identifying the root-cause of a failing chip, i.e., the location and nature of defect. Systematic defects are unintended structural and material changes at specific locations with a higher probability of failure due to repeating manufacturing imperfections. While Design-For-Manufacturability (DFM) guidelines are not always applied due to limited resources like circuit area and design time, enforcing these guidelines helps in ensuring sufficient product yields by preventing systematic defects. However, even if the DFM guidelines are strictly enforced, systematic defects may still occur as complete information about the process and manufacturing is not available due to reducing available time-to-market for chips. ^ An earlier work used DFM guidelines as a basis for modeling of defects, and diagnostic test generation. Under this framework, a circuit is processed to identify layout locations that violate DFM rules. Next, these coordinates are mapped and translated to faults based on different fault models including stuck-at-faults, bridging faults and transition faults. ^ The goal of this thesis is to perform systematic defect diagnosis and analyze the accuracy of diagnosis under the same DFM framework. Thus, systematic defect candidates are generated from DFM guidelines and the generated faultlist is used to perform diagnosis. Because defects may not always be systematic, a new heuristic to dynamically switch between DFM and non-DFM faultlists has also been implemented. This presents us with the best option to follow to further optimize the accuracy of diagnosis. The results demonstrate that the DFM framework can be used to improve the accuracy of diagnosis with minimal resource requirements

Design for manufacturability and assembly

This report presents a study of the various concepts of design for manufacturability and assembly with some case studies, and examples. The goal of DFM is reduction of parts and simplifying assembly process. A simple faucet has been studied and attempts have been made at re-designing the same using the techniques of design for manufaturability as postulated by Boothroyd, Dewhurst and Henry Stoll

Design for Producibility in Fabricated Aerospace Components - A framework for predicting and controlling geometrical variation and weld quality defects during multidisciplinary design

In the aerospace industry, weight reduction has been one of the key factors in making aircraft more fuel efficient in order to satisfy environmental demands and increase competitiveness. One strategy adopted by aircraft component suppliers to reduce weight has been fabrication, in which small cast or forged parts are welded together into a final shape. Fabrication increases design freedom due to the possibility of configuring several materials and geometries, which broadens out the design space and allows multioptimization in product weight, performance quality and cost. However, with fabrication, the number of assembly steps and the complexity of the manufacturing process have increased. The use of welding has brought to the forefront important producibility problems related to geometrical variation and weld quality.The goal of this research is to analyze the current situation in industry and academia and propose methods and tools within Engineering Design and Quality Engineering to solve producibility problems involving welded high performance integrated components. The research group “Geometry Assurance and Robust Design” at Chalmers University of Technology, in which this thesis has been produced, has the objective to simulate and foresee geometrical quality problems during the early phases of the product realization process to allow the development of robust concepts and the optimization of tolerances, thus solving producibility problems. Virtual manufacturing is a key within the multidisciplinary design process of aerospace components, in which automated processes analyze broad sets of design variants to trade-off requirements among various disciplines. However, as studied in this thesis, existing methods and tools to analyze producibility do not cover all aspects that define the quality of welded structures. Furthermore, to this day, not all phenomena related to welding can be virtually modelled. Understanding causes and effects still relies on expert judgements and physical experimentation to a great deal. However, when it comes to assessing the capability of many geometrical variants, such an effort might be costly. This deficiency indicates the need for virtual assessment methods and systematic experimentation to analyze the producibility of the design variants and produce process capability data that can be reused in future projects.To fulfill that need, this thesis provides support to designers in assessing producibility by virtually and rapidly predicting the welding quality of a large number of product design variants during the multidisciplinary design space process of fabricated aerospace components.The first step has been to map the fabrication process during which producibility problems might potentially occur. The producibility conceptual model has been proposed to represent the fabrication process in order to understand how variation is originated and propagated. With this representation at hand, a number of methods have been developed and employed to provide support to: 1) Identify and 2) Measure what affects producibility; 3) Analyze the effect of the interaction between factors that affect producibility and 4)Predict producibility. These activities and methods constitute the core of the proposed Design for Producibility framework. This framework combines specialized information about welding problems (know-hows), and inspection, testing and simulation data to systematically predict and evaluate the welding producibility of a set of product design variants. Through this thesis, producibility evaluations are no longer limited to a single geometry and the study of the process parameter window. Instead, a set of geometrical variants within the design space can be analyzed. The results can be used to perform optimization and evaluate trade-offs among different disciplines during design space exploration and analysis, thus supporting the multidisciplinary design process of fabricated (welded) aerospace components

On the test of single via related defects in digital VLSI designs

Vias are critical for digital circuit manufacturing, as they represent a common defect location, and a general DfM rule suggests replicating every instance for redundancy. When this is not achievable, a mandatory requirement is that the remaining single vias must be tested. We propose an automated method for generating tests and accurately evaluating test coverage of such defects, ready for use in any digital implementation flow and for integration within EDA tools, and also providing a useful quality metric. A prototype tool implementation and experimental results for an industrial case study are presented

An empirical investigation of knowledge management support for software projects.

Projects are unique by definition. Due to this novelty software development projects, in common with all other projects, require knowledge for effective implementation. Most knowledge management frameworks reported in the literature address the organisational need to manage knowledge. The existing frameworks typically discuss the dichotomy between tacit and explicit knowledge, and lay an emphasis on managing the latter. However, software development projects rely upon the experience, creativity and intuition of individual team members to address unstructured situations typified by inherent uncertainty, ambiguity and change. Therefore software projects require the facilitation and interaction of tacit knowledge along with managing and leveraging explicit knowledge.This research examines how tacit and explicit knowledge generated while implementing a software development project can be leveraged and effectively reused in future software projects. In order to address the need to provide knowledge management support to software projects an extended case study was conducted at one of the world's largest software project-based organisations. The aim of the research was to identify and analyse the flow of knowledge, and the capabilities required to support this flow. The research design utilised a combination of open-ended interviews, survey questionnaires, observations of team functioning, work methods and development practices, and a detailed examination of the knowledge management infrastructure and process capabilities. The extensive and exceptional access negotiated for this project enabled the research to focus on a single organisation and resulted in 100 hours of interviews and 340 hours of observations from 98 ongoing projects. Established case study protocols were used for data collection. The data analysis focused on determining categories from the different streams of activities and assigning attributes using Nudist software for data reduction and displaying group-nodes, and conclusion drawing. This enabled the research to establish the 'processual' nature of knowledge, and identify the capabilities required to mobilise and utilise knowledge assets. The research critically analysed the three parallel themes of knowledge management, project management and software engineering, and the outcome of the conceptual synthesis and validation is a dynamic model which represents the knowledge processes that facilitate the flow of tacit and explicit knowledge between software projects. The model depicts the relationships and interactions between the functional areas of the development effort, and presents a continuous and long-term view of supporting the implementation of software projects and developing knowledge practices. For software project-based organisations this research has implications for their ability to manage context, provide feedback and facilitate interaction, and thus build upon their existing knowledge resources and capabilities. The research provides such organisations with a perspective to achieve excellence not only through optimisation of software process improvement, but also through learning, and, the creation and sharing of tacit and explicit knowledge as facilitated by the proposed model

Requirements of a Better Secure Program Coding

Secure program coding refers to how manage the risks determined by the security breaches because of the program source code. The papers reviews the best practices must be doing during the software development life cycle for secure software assurance, the methods and techniques used for a secure coding assurance, the most known and common vulnerabilities determined by a bad coding process and how the security risks are managed and mitigated. As a tool of the better secure program coding, the code review process is presented, together with objective measures for code review assurance and estimation of the effort for the code improvement

Concurrent engineering and design for manufacture in the medical device industry

Concurrent Engineering (CE) is an approach to product development in which engineers work on design and manufacturability at the same time. The ultimate goal of concurrent engineering is to reduce the time-to-market while improving quality. This thesis goes into details about the tools necessary to achieve successful product development in the Medical Device Industry. The novelty of this thesis is not in the tools themselves but rather in the way that they are applied to the medical device industry. The need for the CE approach is of utmost importance because of the vast competition in the medical device industry. The times now require changes. These changes are depicted in detail early in this thesis. This latter suggests that manufacturing is to be perceived like another science. The axiomatic approach to manufacturing answers these needs. A new way of designing a product and collecting data is relevant. It is known as the technique of Quality function Deployment (QFD). Finally, all these tools are managed with the phase approach to management. I sincerely think that this thesis will constitute an invaluable tool for managers and engineers in the medical industry

Design for automated manufacture of composite structures

New trends in manufacturing highlight the growing use of composite materials to produce lightweight, high performance structures. This requires the design stage to account for complex manufacturing constraints, and as industry begins to move towards automated manufacturing of composites, the more complex manufacturing constraints can introduce severe limitations to the design space, reducing the opportunity for designers to optimise a product. To address these limitations, this research proposes strategies for implementing design for manufacture specifically accounting for automated manufacture of composite structures. As a composite design develops, more detail is added, increasing the design fidelity. Typically design for manufacturing practices are only applied when the design fidelity is detailed enough to see individual plies. However, by implementing design for manufacturing practice at earlier stages of the design, when the design fidelity is low and design change is easy to implement, the greatest performance and manufacturing gains can be achieved. This research aims to develop a design process that uses digital technology to facilitate design for automated manufacture for composite structures. This research uses a systematic approach to create a generic design process and supporting tools, capable of identifying the key manufacturing constraints, and accounting for them at the earliest possible stages of the design. The proposed design process uses a strategy to apply design for manufacture using digital tools, and identifies actions required to enable automated composite manufacturing. The development of the design process is guided by the capture of the current industrial design practices. The proposed process is validated through the design and manufacture of an industrial demonstration structure, produced using an automated composite manufacturing process. The results from validation confirm the hypothesis that it is possible to have a generic design process to support the design for automated manufacturing of composites components