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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
21

Critical Area Driven Dummy Fill Insertion to Improve Manufacturing Yield

Dhumane, Nishant 01 January 2012 (has links) (PDF)
Non-planar surface may cause incorrect transfer of patterns during lithography. In today’s IC manufacturing, chemical mechanical polishing (CMP) is used for topographical planarization. Since polish rates for metals and oxides are different, dummy metal fills in layout is used to minimize post-CMP thickness variability. Traditional metal fill solutions focus on satisfying density target determined by layout density analysis techniques. These solutions may potentially reduce yield by increasing probability of failure (POF) due to particulate defects and also impact design performance. Layout design solutions that minimize POF and also improve surface planarity via dummy fill insertions have competing requirements for line spacing. In this thesis, I present a formulation to balance these competing goals and provide a comparative study of greedy (or fixed spacing), variable spacing and LP formulation based fill insertions based on scalability and quality of solution. I extend the variable spacing fill to allow non-preferred direction routing of fill patterns in order to further improve the CA. Traditional fill solutions impact design performance due to increase coupling capacitance on signal nets. I present a fill insertion algorithm that minimizes this increase in coupling capacitance due to fill. Finally, I extend the critical area based solution to include SRAF insertion in order to account for optical diffraction in lithography. Thus the proposed solution addresses both lithography and particulate related defects and minimizes the fill impact on design performance at the same time. Experimental results based on layout of ISCAS 85 benchmark circuits show that the variable spacing and the LP formulation based fill insertion techniques result in substantially reduced critical area while satisfying the layout density and uniformity criteria. The coupling capacitance minimization fill solution reduces the fill impact on coupling capacitance while at the same time minimizing the critical area.
22

Some aspects on designing for metal Powder Bed Fusion

Hällgren, Sebastian January 2017 (has links)
Additive Manufacturing (AM) using the Powder Bed Fusion (PBF) is a relatively new manufacturing method that is capable of creating shapes that was previously practically impossible to manufacture. Many think it will revolutionize how manufacturing will be done in the future. This thesis is about some aspects of when and how to Design for Additive Manufacturing (DfAM) when using the PBF method in metal materials. Designing complex shapes is neither easy nor always needed, so when to design for AM is a question with different answers depending on industry or product. The cost versus performance is an important metric in making that selection. How to design for AM can be divided into how to improve performance and how to improve additive manufacturability where how to improve performance once depends on product, company and customer needs. Using advanced part shaping techniques like using Lattices or Topology Optimization (TO) to lower part mass may increase customer value in addition to lowering part cost due to faster part builds and less powder and energy use. Improving PBF manufacturability is then warranted for parts that reach series production, where determining an optimal build direction is key as it affects many properties of PBF parts. Complex shapes which are designed for optimal performance are usually more sensitive to defects which might reduce the expected performance of the part. Non Destructive Evaluation (NDE) might be needed to certify a part for dimensional accuracy and internal defects prior use. The licentiate thesis covers some aspects of both when to DfAM and how to DfAM of products destined for series production. It uses design by Lattices and Topology Optimization to reduce mass and looks at the effect on part cost and mass. It also shows effects on geometry translation accuracies from design to AM caused by differences in geometric definitions. Finally it shows the effect on how different NDE methods are capable of detecting defects in additively manufactured parts.
23

Development of Deployable Wings for Small Unmanned Aerial Vehicles Using Compliant Mechanisms

Landon, Steven D. 06 July 2007 (has links) (PDF)
Unmanned Air Vehicles (UAVs) have recently gained attention due to their increased ability to perform sophisticated missions with less cost and/or risk than their manned counterparts. This thesis develops approaches to the use of compliant mechanisms in the design of deployable wings for small UAVs. Although deployable wings with rigid-link mechanisms have been used in the past to maintain flight endurance while minimizing required storage volume, compliant mechanisms offer many advantages in manufacturability and potential space savings due to function sharing of components. A number of compliant, deployable wing concepts are generated and a classification system for them is formed. The pool of generated concepts serves as a basis for stimulating future concept ideas. A methodology is also proposed for evaluating concepts for a given application. The approach to developing compliant designs for certain applications is illustrated through two example designs, which demonstrate key portions of the proposed design process. Each is modeled and analyzed to demonstrate viability.

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