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Effect of Fixtures on Deformation and Warpage

Study on the Effect of Fixtures on Deformation and Warpage of the Double-Sided Flexible Printed Circuit Board Through Reflow Using DIC Abstract – Flexible electronics provide new design options not afforded by rigid electronics in a variety of applications including wearable electronics, robotics and automotive systems. However, the processes for the manufacturing of complex electronic assemblies using fine-pitch components are not as well developed as those for rigid electronics. The lack of structural rigidity of flexible printed circuit cards requires the use of fixtures or palletes for component placement and subsequent reflow. In addition, mechanisms are needed to compensate for the deformation and warpage of the flexible substrate and components during assembly. In this paper, two different fixture options have been presented for the manufacture of flexible circuits. The first fixture option includes the use of a pallete with tensioners. The second fixture option includes the use of vacuum fixture during reflow of the flex circuit assembly. The deformation of the flex circuit assemblies during reflow has been studied using a combination of low-speed high resolution cameras in conjunction with digital image correlation. The double-sided board used for the experiment is of BGA – combination with dummy components, A-PBGA–mm-mm and A-CABGA–mm-mm. Firstly, warping of the flexible circuit with only PBGA on the front side was studied, then CABGA was placed on the back side using the pick and place machine, and warping was studied again, both using DIC. Two low speed Point Grey Cameras were used to capture many frames of flexible circuit going through every stage in reflow and a DIC software Vic 3D was used to get the warpage measurements. Both of the warping data has been presented in this paper and compared with the results in rigid circuit boards. Keywords – Digital Image Correlation (DIC), flexible circuit, warpage, BGA package, flexible circuit fixtures. INTRODUCTION Since the last few decades, flexible electronics have been replacing rigid electronics, and are found in everything from as common as notebooks, mobile phones, to as sophisticated as military and avionics systems. This transition itself is major evidence of a major technical revolution. Although the flexible circuit technology evolved recently, it has long been envisioned by famous researchers at the turn of the 20th century. Flexible Printed Circuits (FPCs) provides whole range of benefits that surpasses and cannot be achieved from rigid Printed Circuit Boards (PCBs), such as more design freedom, dynamic flexing, and many more. To meet ever increasing demand for innovative electronics and designs, flexible circuit technology has been branching out significantly from its initial role of wire replacement. Warpage is defined as the out-of-plane displacement a package or a PCB experiences due to CTE (coefficient of thermal expansion) mismatch between different materials, processing conditions, and package architecture. Many studies have been performed in the past to examine the warpage that occurs in electronic packages mounted on a rigid board during solder reflow [1], [2], [3]. Warpage, when in excess, may result in many problems, if not addressed, such as open connections, loss-of-coplanarity, which significantly influences the reliability and performance of electronic packages and boards. Since the electronic assemblies have a greater tendency to experience warping at high and low temperatures, warpage during a solder reflow is a key factor to consider to do reliability analysis of FPCs. Shadow Moiré or Moiré interferometery, a conventional, non-contact full optical method was used initially to measure out-of-plane displacement to learn the warpage behavior of electronic packages [4]. Later, Digital Image Correlation (DIC) was introduced by Park et al [5], a non-contact, non-optical method to measure the deformation and strain fields due to its robustness and simplicity. DIC, a state-of-art technique has been used by many researchers in various scenarios, such as transient-shock, drop impact, thermal analysis of BGA packages, deformation of a solder joint of BGA assembly, to get full-field deformation and strains [6], [7], [8], [9]. The effect of package architecture, material properties, and process conditions which greatly affect the warpage has also been studied in detail for a Package-on-Package module using FEA [10]. But there are not many open literatures present for the warpage in FPCs. Flexible circuits, because of their flexibility, they require fixtures to keep them flat during fabrication process. However, FPCs still warp and show deformation when put through reflow oven as temperature increases. In this article, two fixtures have been exploited: a pallete with four fixed pins and two tensioners, and a vacuum fixture. Both of the fixtures are shown in Fig. – . Test Vehicle Description The test vehicle is designed to investigate the temperature effect on the flex circuit and understand the warping behavior during solder reflow. The double-sided flex circuit is shown in Fig. – . The circuit is designed to accommodate two surface-mount BGA components: A-PBGA256-1.0mm-17mm and A-CABGA144-1.0mm-13mm. Both of the BGAs are daisy-chained mechanical dummy samples shown in Fig. .Package specifications are shown in Table 1. Figure 5. Dummy Packages. PBGA (left) and CABGA (right). Table 1. Packages Specifications Part Description I/O count Pitch Ball Height Body Size Ball Matrix A-PBGA256-1.0mm-17mm mm mm mm x A-CABGA144-1.0mm-13mm mm mm mm x The double-sided flexible circuit consists of a base film of polyimide of m, one copper layer on both sides of the film of m, top and bottom film thickness of m and m respectively, and ENIG (Electroless nickel immersion gold) surface finish of . The flex circuit of x has a total thickness of mm. The cross section of the flex circuit is shown in Fig. . Figure 6: Flexible Circuit Composition. The warpage of the flex circuit with BGA components is studied using 3D digital image correlation. Principle of DIC The basic principle of DIC requires taking digital images of the specimen surface from a CCD camera before and after deformation and iteratively, computing the motion of each image point in a subset by comparing both images using computer program that is developed based on well-established algorithms and interpolation schemes to obtain the desired displacement and strain fields. Fig. shows a schematic of the DIC principle. The computer program Vic 3D is widely used and accepted by many researchers to perform DIC. However, there are certain requirements to be met to get an accurate displacement or strain field from DIC, such as: (1) the specimen surface must have a random gray intensity distribution or speckle pattern; (2) the CCD cameras should not be moved while taking the digital images, and must be calibrated before running DIC; (3) the subset size should be carefully selected before running DIC. It should be large enough that contains sufficient distinctive pattern and small enough that can accurately approximate deformation field using subset shape function. Study on subset size selection has been studied by many researchers [11], [12]. Vic D, when the above mentioned requirements are met, performs the correlation using pre-defined algorithms and provides us with the full-field displacement and strain values. Figure 7[3]. DIC Schematic. EXPERIMENT DIC, whether it is D or D, provides the displacements and strains acting on a specimen surface. The main difference is that 3D provides out-of-plane displacements while 2D provides in-plane displacements. It further demands the surface should have a random intensity pattern or speckle pattern to get the most accurate results. In this study, the most conventional technique used in obtaining the speckles, the spray paint method is used. A layer of white paint is sprayed on the surface and black paint is sprinkled onto it to create a fine speckle pattern. An image of a pattern is shown in the Fig . D DIC is performed by correlating digital images: reference and deformed, from two CCD cameras focusing on the specimen surface. Studies have been performed on the different parameters, such as the angle between the two cameras, facet size, facet step, which affects the displacement/strain results [13]. Flexible circuits tend to bend and requires the use of a pallete or a fixture to keep them flat while surface-mounting the components and during reflow. In this study, two types of fixtures have been used: pallete with tensioners, and a vacuum fixture. Pallete The pallete, as shown in Fig. consists of two tensioners and four fixed pins which are used to keep the circuit flat during all the processes. To perform DIC on the back surface of the circuit which has CABGA , the pallete has a pocket in which front package, PBGA can be flushed in while surface mounting and reflow of CABGA . Figure 8. Pallete with Tensioners. Vacuum Fixture A vacuum fixture, shown in Fig. consists of a porous sintered block of stainless steel which when attached to a vacuum pump with a silicone hose, creates a suction force which keeps the flexible circuit flat during the reflow process. This fixture, due to lack of a pocket to flush PBGA package, cannot be used to perform DIC on CABGA . Therefore, DIC was only performed on the front side of the circuit, which is PBGA . Test Procedure In order to keep the flexible circuit flat, both of the fixtures have been used during all the stages of assembly: pre-baking, placement, speckle pattern, reflow. The test procedure follows the following steps: Pre-bake Flexible circuits, made of polyimide layer are very hygroscopic in nature and readily absorb moisture when kept at room temperature. Therefore, before placement of components, flexible circuits are pre-baked at for hours to remove any moisture from the circuits. Placement of BGA Packages First, PBGA is placed on the circuit using standard pick and place machine. A stencil printer was used to place SAC solder on the circuit. During placement of the solder and package, flex circuit needs to be flat to perfectly mount the component and to avoid any resistivity errors. Therefore, both, pallete and vacuum fixture were used to keep the circuit flat during this process. For CABGA , only pallete was used because of the pocket to flush in PBGA , which vacuum fixture lacks in. Fabricated circuits on the pallete are shown in Fig. . From the Fig. , it can be seen that the size of the sintered stainless steel block is greater than the size of the flex circuit. Therefore, Kapton tape was used as shown in Fig. to cover the exposed area and the through-holes on the circuit to direct the vacuum suction force on the circuit and on the area where package is placed. Figure 10. Fabricated Packages on the Pallete. Figure 11. Kapton Tape on Vacuum Fixture. Packages were also placed, both sides on the rigid circuit boards, shown in Fig. . Speckle Pattern 3D DIC demands the surface to have an intensity pattern or speckle pattern to track points on the specimen surface to obtain displacements and strains. Conventional spraying method has been used to create artificial speckle pattern. White paint is sprayed on the circuit surface, and then the black paint is sprinkled onto the top to create a distinctive pattern. An example of a speckle pattern on a flexible circuit board is shown in Fig. . Camera Calibration To generate useful and accurate displacement and strain results, calibration of the cameras must be performed before starting the reflow process. Calibration is a key process and has a major influence on the performance of the whole system. DIC calibration provides us with two types of parameters: Intrinsic and Extrinsic. Intrinsic parameters indicate the internal optical characteristics of the camera such as focal length of the lenses, position between the lenses, sensor center. Extrinsic parameters indicate the external characteristics between camera and the specimen surface such as the distance between the lens and surface, translation vector, distance between the cameras. To achieve a sub-pixel accuracy, a calibration grid or calibration target, with known distance between the points, as shown in Fig. is used to calibrate the stereo system in Vic D software. An error of less than ___ was achieved in all of the experimental tests. Detail description on the camera calibration can be found in literature [14]. Figure 14. Calibration Target. Reflow Process After creating speckle pattern and calibrating the cameras, reflow profile was selected, with the maximum temperature going up to for the flexible board and for rigid boards, and the process was started. Reflow profiles for the flexible circuit board and rigid circuit board are shown in Fig. and Fig. respectively. At the same time cameras were also turned on to start the recording. Features of Vic D software were used to make sure that the cameras starts recording at the same time the reflow process starts. Test Setup for the reflow process can be seen in Fig. . Figure 15. Test Setup. Figure 16. Reflow Profile (Flexible Board). Figure 17. Reflow Profile (Rigid Board). RESULTS Warpage study has been performed on the double-sided flexible printed circuit board using D DIC using two fixtures to keep the flex circuit flat: pallete with tensioners, and a vacuum fixture. Multiple warpage results for both the fixtures have been performed to check if the repeatability in the warpage occurs. DIC was also performed on the double-sided rigid circuit boards to compare the warpage results between flexible and rigid boards. Full-field displacements are plotted for the points along the diagonal at the maximum temperature and the z-displacements has been plotted as a function of temperature as it increases to the maximum temperature. Warpage values are only considered till the reflow zone of the profile. Pallete Warpage results of both sides of the flexible circuit with packages PBGA and CABGA using pallete with tensioners have been presented. Reflow of PBGA was performed first, which implies there is no package on the bottom, while reflow of CABGA was performed second, which implies there is package on the bottom, and furthermore the package is PBGA . Fig. –shows the comparison of two warpage tests displacements for the points along the diagonal at the maximum temperature in x, y, and z-direction and near the edges of the package versus the temperature increase for the front side of flexible board. Similarly, Fig. –shows the warpage results for the back side of the flexible board when there is package on the bottom of CABGA . Vacuum Fixture Warpage results of the flexible board for only one side, with PBGA have been presented. Due to lack of pocket to flush in package as compared to the pallete, reflow and DIC of CABGA was not performed on the vacuum fixture. Fig. – shows the comparison of warpage tests performed on the front side of the flexible circuit. Comparison with Rigid Boards Warpage measurements of the double-sided flexible circuit board have been compared with the rigid circuit board in this section. The rigid boards are of the same configuration with two packages. DIC was performed on both sides of the board and the warpage has been plotted in Fig. – for the front side of the board, and Fig. – for the back side when there is a package on the bottom. The negative values presented in below warpage results should not be interpreted as the contraction of material. The negative value signifies that the point at which displacement is extracted, experiences displacement in negative direction from the origin defined in reference frame, which is at the start of the reflow process. Before starting the DIC process, origin in a reference frame is specified to be at the center of the package. Results-I(a): Flexible Circuit Board (PBGA on Pallete The graphs below shows the warpage in a flexible circuit for the points along the diagonal from bottom-left to top-left and near the edges of PBGA . Fig. – shows the increase in x and y displacement as points on diagonal move from bottom-left to top-right. Fig. also shows the increase in z-displacement initially till the point where tensioners come in place which leads to decrease in warpage as they work to keep the circuit flat and decreases to the minimum to the point where tensioners are. Fig. – shows the increase in z-displacement as the temperature increases and reaches to the maximum in the reflow profile. The maximum displacement in Fig. – can be seen in the middle, which it should be because of the fixed pins and tensioners on the corners of the board. Figure 19. Y-Displacement Warpage (along the diagonal). Figure 20. Z-Displacement Warpage (along the diagonal). 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PHIL 3015 Application of Philosophical Arguments to Modern Day Issues Paper.

Topic for Analysis 2: For our second analysis, please choose two philosophers from Week 10: Wolff, Locke, or Mill and apply their philosophical argument to a modern-day issue or event. To do this, you will need to clearly articulate their premise and then explain why it is the best approach to a contemporary issue – alternatively, you are welcome to explain how a contemporary political figure or organization embodies this philosophy.philosophers Wolff, Locke, or Mill:Robert Paul Wolff: In Defense of Anarchism, p 571-575.John Locke: The Democratic Answer: The Justification of the State Is Its Promotion of Security and Natural Human Rights, p 586-590.John Stuart Mill: A Classical Liberal Answer: Government Must Promote Freedom, p 591-597These contents are in the textbook (in the files)You must choose two who are on different sides of the debate. Clearly articulate the key premise and key supports of each and conclude with a critique paragraph that argues for the one or the other. Submission Requirements:This essay should be a minimum of three pages and should address the topic below.The primary texts in the chapter must be used and cited appropriately – you must provide evidence for your argument.All quotations (lines from the texts) must be included grammatically in your own sentences and commented on specifically.Outside sources should not be used at any point in this essay.Remember to use our discussions as a starting point to frame your argument – our discussions are specifically designed to allow you to do so.Please be sure to cite sources used both within your essay and as a separate works cited page. You must use MLA Style and Format. Remember that there are additional resources in the course to help you develop this essay:(How to) Write About Philosophy.Grading: You will be evaluated and graded using the rubric (in the files)
PHIL 3015 Application of Philosophical Arguments to Modern Day Issues Paper

SEC Wk 4 Should the Minimum Living Wage Be Raised Persuasive Essay

SEC Wk 4 Should the Minimum Living Wage Be Raised Persuasive Essay.

This week you will prepare for the Final Persuasive Essay by completing a Writing Plan. The Writing Plan will help you identify the main elements necessary to compose an effective essay. Attached below is a Worksheet, which you will download, complete and submit for a grade. Following are the directions for the essay that is due in Week Four. You will need to select a topic, find relevant sources from the Library and then complete the worksheet.Persuasive Essay (Due Week Four)The persuasive essay requires you to argue a position on a debatable topic. You will support your position by conducting research, evaluating evidence, and presenting it in a well-organized essay. This assignment is based on research. It is not simply a preference or an expression of your opinion. The goal is to persuade a reader to adopt a certain point of view by using reliable sources, statistics and facts, logic, examples, and expert opinions.The essay should address an opposing view, and respectfully state why your position is stronger.The final essay should include a thesis statement, clear position on chosen topic, acknowledgement of the opposing view, clear purpose and direction, and effective conclusion.Revised essay should be error free and consistent in tone, point of view and verb tense.Three reliable sources are required to support your position.Reliable sources include Keiser Library, Google scholar, and others approved by your instructor.Final Persuasive Essay should be a polished error-free document. It is recommended that you review and complete the revision worksheet before finalize submission.The Final essay should include a thesis statement, clear position on chosen topic, acknowledgment of the opposing view, clear purpose and direction, and effective conclusion.Revised essay should be error free and consistent in tone, point of view and verb tense.Three reliable sources are required to support your position.Reliable sources include Keiser Library, Google scholar, and others approved by your instructor.See Revision Worksheet and Rubric for guidance and assessment of you work.Choose one of the following Writing Suggestions or you may choose a topic relevant to your career or studies. The topic must be debatable (have two opposing sides), research based (use facts, not personal opinion) and relevant to your career. See page 172 for further guidance.IMMIGRATION: Should the U.S. offer a path to citizenship/legal residency for illegal immigrants?MINIMUM WAGE: Should the minimum wage be raised from its current $7.25 per hour?ENVIRONMENT: Should the US support initiatives that restrict carbon emissions (or carbon pollution)?REQUIREMENTS1000 words (minimum) persuasive essayMinimum of three sources with in-text citationsMicrosoft word document in APA format including title page, reference page.Submission to OWL is recommendedHOW TO FORMAT YOUR PAPERPlease review attached document for the proper format for your papers. Please note the following:All papers must be Microsoft Word documents.The paper has a running head that is the title of your paper in ALL CAPS. It is accompanied by a page number. Use your header function to create this line. Do not type it as text in the actual text area for your writing. (See your help function for information on creating headers and section breaks.)The paper is double-spaced in Times New Roman, size 12, and has no extra spaces between the paragraphs.The paper uses one-inch margins and half-inch indentions for the beginning of paragraphs. You can set this up in Microsoft Word to automatically default to these settings for your paper.Paper should include title page, abstract and reference page.
SEC Wk 4 Should the Minimum Living Wage Be Raised Persuasive Essay

University of Michigan Population Trends in South Africa Analytical Review

programming assignment help University of Michigan Population Trends in South Africa Analytical Review.

I’m working on a writing Essay and need a reference to help me learn.

The region I choose is : South AfricaHere is the writing requirement. Need to write at least 550 words. Need to choose at least two graphs or images to help support arguments. Chose ONE of the following prompts. Prompt 1We often think of the Cold War as a dispute between the US (and Europe) and the Soviet Union. However, the Cold War influenced policy around the globe as the West and the Soviets vied for power and influence. Some of the legacies are nuclear testing, wars, militarization, and economic policies. Find how the Cold War influenced your region or specific states (countries) within your region. How were the US or the Soviets involved? What were the alliances? What was the result?Prompt 2Almost every state in the world has ethnic minority groups. How does a state in your region assert control over that ethnic minority in order to bring it under control of the dominant group? Consider this week we talked about Russification and the migration of Han Chinese into the Central Asia regions of China. Last week we introduced European colonialism. There are various strategies ranging from violent repression of difference to creating autonomy for minority groups. What happens in your region? Prompt 3Demographic challenges vary between regions. What do the population pyramids and other demographic indicators say about population trends in your region? What are the potential challenges that governments face? Do they have responses yet? If so, what are they? Are the populations rapidly growing? Decreasing? Uneven with respect to gender? Can you explain these patterns? You do not need to do this for every state in your region, but pick a few that might contrast or otherwise make an interesting discussion about the factors that influence demographics and government responses to them.
University of Michigan Population Trends in South Africa Analytical Review

Subtitling Software’ Significance for Subtitlers: WinCap Essay

The importance of subtitling software for interpreters can hardly be overrated – it provides a significant advantage for the professionals, who are assigned with the task of writing down the captions for a certain movie, TV program, a recording, etc. A range of people view subtitling software as a form of cheating; others believe that a subtitling software may fail a professional easily due to the mispronunciation of certain words and, therefore, the failure to capture the right one. However, when viewing subtitling software, such as WinCap, as a tool for providing support for a subtitler instead of doing the job of the latter, the above-mentioned program can be considered an essential tool for improving time management and the quality of subtitling and translation. The use of software as a part of the subtitling process is often looked down at as a cheap substitute for an actual subtitler. The given statement can be viewed as true to a considerable degree; indeed, there is a possibility that it can be used as a lazy way of transcribing the speech without putting any actual effort into the process (Quah 7). The above-mentioned concern is, in fact, an integral part of the criticism for any equipment used as assistance in the process of translation or transcribing – the incorporation of the technology in question simplifies the process of subtitling (Cintas and Remael 13). As a result, the latter is reduced to editing the information supplied by the WinCap program, which might be efficient in terms of the output (Austermühl 3), yet may result in a significant drop in the proficiency of the person using it. It should be noted, though, that WinCap cannot be considered the ultimate tool for creating subtitles without putting any actual effort into the process. Although the program does feature a range of innovative technologies and can even detect actual speech, providing subtitles in the process, it still identifies only a limited amount of sound variations (Gambier and Gottlieb 111). Specifically, the WinCap program may fail in case when a subtitler has to deal with a specific accentor to work with a recording of a speech pronounced in a specific dialect. Finally, the quality of the recording may affect the actual output to a considerable degree, turning the text generated by the software into gibberish. Despite the above-mentioned issues, the technology is still admittedly impressive. Simplifying the job of a subtitler to checking the accuracy of the words recorded and making sure that the subtitles coincide with the recording, the WinCap program can be viewed as a huge breakthrough (Cintas and Remael 15). The properties of the software allow for integrating the visual and the audio information successfully (Bowker and Pearson 18) so that the user of the software could receive both types of information and process them accordingly; as a result, the output quality is increased significantly due to a more careful and a practically uninterrupted process of data analysis (Gambier and Gottlieb 112). The addition of the automatic time option can be interpreted as a major advantage for the people, who write subtitles with the help of the program in question. To be more exact, the above-mentioned function can be viewed as a major assistance in timing the process of subtitling in accordance with the specifics of the working process and the environment, in which the person using the software has to work. Finally, the issue of data storage deserves to be mentioned. While having an extensive memory is one of the subtitler’s prime assets, it is practically impossible to memorize every single bit of the information flow. Therefore, whenever a specific word or collocation used previously and requiring significant spelling skills emerges, going back in the notes in an attempt to locate the specified word or phrase and transcribe it properly is barely possible. This is the point, at which the subtitling software, such as WinCap, factors in as an essential tool for capturing data and retaining it for the further use. Therefore, the usefulness of the program can be evaluated as moderate. Though the program has its flaws and may clearly be used for increasing the quantity of the work done instead of the quality thereof, it still supports a subtitler in the process of capturing the essential data required for putting a complex piece of text together. While WinCap is certainly not to be overused, it should be considered by professional subtitlers as a key tool to incorporate into their production process. Get your 100% original paper on any topic done in as little as 3 hours Learn More Though subtitling technologies, such as WinCap, can only be viewed as a support for an interpreter and not the substitute for actual subtitling skills, they still provide major assistance for translators, as they allow the latter to manage their time more efficiently and locate the appropriate equivalents for specific words in a faster manner. The WinCap technology, therefore, should be regarded as a major support for a subtitler and an impressive foot forward in the design of translation technology. Works Cited Austermühl, Frank. Electronic Tools for Translators. Manchester, UK: St. Jerome, 2001. Print. Bowker, Lynne and Jennifer Pearson. Working with Specialized Language: A Practical Guide to Using Corpora. London, UK: Routledge, 2002. Print. Cintas, Jorge Díaz and Aline Remael. Audiovisual Translation: Subtitling. Manchester, UK: Routledge, 2007. Print. Gambier, Jerome Y. and Hans Gottlieb. (Multi) Media Translation. Amsterdam: John Benjamins, 2001. Print. Quah, Chiew Kin. Translation and Technology. Basingstoke: Palgrave, 2007. Print.

Module Four Discussion hybrid channel system

Module Four Discussion hybrid channel system.

Today, some of the countries more successful companies are using a hybrid channel system to increase its effectiveness of reaching the consumer. The text uses the examples of IBM, Charles Schwab, and others and notes that channel integration and its features are what the consumer prefers. Choose or find one additional example of a firm using the hybrid system, and comment on how they see this system delivering value to the consumer. Student answers should be directed toward the three features of channel integration found in the textbook.less than 300 wordsi have some examples in attachment, you can use it as referencen but dou’t use same company
Module Four Discussion hybrid channel system

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