Expanding the Vision of Sensor Materials (1995) / Chapter Skim
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CHAPTER 3: SELECTED SENSOR APPLICATIONS IN MANUFACTURING
CHAPTER 3: SELECTED SENSOR APPLICATIONS IN MANUFACTURING
Pages 33-46
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From page 33... ...
In this approach, sensors monitor process parameters, such as temperature, gas pressure, and composition. However, as the sophistication and complexity of materials processing increase, sensors will be needed to directly monitor changes in the product, such as grain size growth during processing; location of nucleation sites in epitaxial grown thin films; and chemical composition, morphology, and nanoscale thickness of fiber interface coatings for ceramic and metal matrix composites.
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From page 34... ...
In short, a self-directed system generates a control path in response to changes in material behavior that are denoted as process events, as opposed to some pre-established schedule of process parameters. Intelligent processing systems exemplify a process control strategy whereby process events regarding material changes, such as chemical-state change, flow, deformation, and growth, are continually evaluated for dynamic adjustment and prediction of process parameters that affect product quality metrics, which include process repeatability, process yield, and consistent properties.
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From page 35... ...
In summary, intelligent processing is process control by objectives rather than control by following prescribed parameters. Applications of intelligent processing vary widely and range from the processing of thin-film engineered materials2 to the processing of polymers and polymeric composites, metals, and ceramics for bulk structural applications.
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From page 36... ...
This mapping, depicted in Figure 3-2, is often referred to as an "influence diagram." It relates process contro! variables to in situ material behavior to resultant material properties.5 It can serve to identify and prioritize relationships needecl for self-directed process control as well as establish sensing technology requirements (LeCIair and Abrams, 1989~.
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From page 37... ...
To identify various levels of candidate improvements, the framework presented in Chapter 2 was applied to relate sensing needs (e.g., resin temperature) to the currently available sensor technology (e.g., thermocouple)
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From page 38... ...
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From page 39... ...
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From page 40... ...
cannot be directly obtained, since their measurement requires part destruction (University of Delaware, 1989~. Void content, a commonly used measure of laminate quality, can be measured by x-rays, ultrasonic pulses, or determination of local electrical or by thermal conductivity using infrared sensors.
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From page 41... ...
For example, accurate control of even such commonly used processes as rapid thermal processing and plasma deposition and etch requires new sensor materials and approaches. And environmentally conscious manufacturing will require recycling and reuse of chemicals, not only for waste minimization but also for cost reduction.
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From page 42... ...
These epitaxial growth processes require sensors for control of layer thickness, alloy concentration, interface sharpness, composition, etc., to enable low-cost, reproducible, uniform, and tailorable structures. Research in new sensor materials and technologies for molecular beam epitaxy and chemical vapor deposition includes work on reflection mass spectrometry (Brennan et al., 1992; Chalmers and Killeen, 1993; Chalmers et al., 1993~; Resorption mass spectrometry (Evans et al., 1993a, by, and ellipsometry (Patterson et al., 1992~.
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From page 43... ...
Laser-fiberoptic sensor technology has been demonstrated to perform in situ chemical analysis of polyimide and epoxy to determine degree-ofcure and infer the molecular weight during processing (Maguire et al., 1992~. This accomplishment in laser-fiberoptic sensing technology has enabled the intelligent processing of new polyimide composites that are more difficult to process and for which conventional sensing of physical parameters such as temperature and viscosity has been insufficient.
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From page 44... ...
Thus there is a requirement for the development of a matrix modulus sensor. Manufacturing Integrated Circuits Accurate control of even such commonly used processes as rapid thermal processing and plasma deposition and etch requires new sensor materials and approaches.
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From page 45... ...
In situ material behavior refers to those parameters that capture chemical and physical changes in the material during processing. Desired material properties primarily relate to customerestablished product-quality metrics.
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From page 46... ...
8. Out-of-autoclave fabrication involves using mechanical methods instead of heated high-pressure air to form and con 46 solidate the material to the desired geometric configuration and strength.
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