Advanced Materials & Processes

NOV-DEC 2013

Covers developments in engineering materials selection, processing, fabrication, testing/characterization, materials engineering trends, and emerging technologies, industrial and consumer applications, as well as business and management trends

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i T S S e temperature ceramics and metals. Considerable research is underway, which deserves a focused review not included in the present discussion. This article seeks to examine application of thermal spray technology in thick film or mesoscale electronic devices and sensor materials where an untapped opportunity clearly exists. 10 Thick film electronics based on devices with dimensions in the 10 µm to mm range represent a multibillion dollar industry. These devices rely on ceramic and metal components typically built via screen printing techniques with appropriate co-firing at temperatures from 700° to 1400°C, depending on the nature of the ceramic material or device. This technique—although the mainstay of the power electronics industry—has limitations, as it is built on traditional 2D stacking and co-firing. Numerous opportunities to incorporate thermal spray technology exist, for example, in component-integrated electronics and thick film sensors where there is a need to integrate electronics or sensors with a structural component. Further, many applications seek ceramic or metallic interconnection and device integration with polymeric carrier materials. It is in precisely these situations that thermal spray offers a novel extension to traditional thick film technology. Thermal spray also offers the ability for high throughput with in situ application of metals, ceramics, and polymers, in most cases without requiring significant thermal input to the substrate. The technology also can be adopted for 3D 70 ADVANCED MATERIALS & PROCESSES • NOVEMBER-DECEMBER 2013 manufacturing and is customizable for a range of dimensions. What is more, the process allows significant materials versatility along with the ability to integrate with other hybrid manufacturing systems, such as laser annealing or micromachining. Thermal spray can readily fabricate insulated metal substrates, but with specialized configurations, it can also be used for fine scale printing or direct writing. This has led to considerable interest in applying the technology in electronics and sensor manufacturing. Figure 1 showcases potential opportunities for thermal spray in functional materials and electronics. Critical challenges remain in order to realize this potential. The key issue is to understand the process-structureproperty relationships for functional systems. In addition, the rapid heating and cooling cycles of thermal spray processes can affect not only extrinsic defects (e.g., porosity, interfaces), but also intrinsic materials issues such as metastability, stoichiometric variations, and oxidation states. The technology can only be harnessed if adequate material properties are achieved. Advances in process science, technological precision, and an enhanced understanding of materials behavior have spurred slow but steady penetration of thermal spray technology into various applications, and this is iTSSe only expected to grow over the coming decades. Sanjay Sampath is professor at Stony Brook University, Center for Thermal Spray Research, Rm 130, Heavy Engineering Building, NY 11794, 631/6329512, ssampath@ms.cc.sunyb.edu, www.ctsr-sunysb.org.

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