PROCESSING OF ELECTRONIC CERAMICS

Electronic ceramics enjoy widespread commercial exploitation in components such as thermistors, capacitors, transducers, variators, etc. Their use in these areas has developed for a variety of technical, historical and economic reasons. Amongst the most prominent are  

1) The novel electronic properties of electronic cereutiics. Many of these materials cannot be prepared by single crystal routes because of a) their complicated chemical composition or b) their dependence upon their granular structure for their properties, e.g. grain boundary layer capacitors, ZnO varistors, BaTiOg PTC thermistors. 

2) The relative ease with which these properties can be tailored to suit specific applications. This is particularly true in the case of some crystal structures. The perovskite structure is an example where a wide range of solid solutions can be accommodated. In this structure cation dopants can be used to great effect. For example, donors or acceptors can be used to produce soft or hard piejoelectric lead zirconate titanate. 

The properties of many electronic ceramics permit the construction of devices which otherwise may not be realised. This is in marked contrast to 

Developments in this field, permitting controlled deposition of complex chemical compositions will lead to greater exploitation of these processes. Although these techniques will not be discussed further here, (see chapter 9) there are lessons arising from them which can be applied to the powder-fabrication-sintering route. The most important of these is the small number 

---

Cannell, D. and Trigg, R, Processing of electronic ceramics, in Binner, J.G.P., Ed., Advanced Ceramic Processing and Technology, NJ Noyes, 1990, p>p. 95-121. Young, W.S. and Knickerbocker, S.H., Multilayer ceramic technology, in Buchanan, R.C., Ed., Ceramic Materials for Electronics, New York Marcel Dekker, 1991, pp. 489-526. 

Alternative Thin-Film Fabrication Approaches. Thin films of electronic ceramic materials have also been prepared by sputtering, electron beam evaporation, laser ablation, chemical beam deposition, and chemical vapor deposition (CVD). In the sputtering process, targets may be metal... 

Hollingsworth, J. A. Buhro, W. E. Hepp, A. F. Jenkins, P. P. Stan, M. A. 1998. Spray chemical vapor deposition of CuInS2 thin films for application in solar cell devices. Chemical Aspects of Electronic Ceramics Processing, edited by Kumta, P. N. et al., MRS Symp. Proc., Vol. 495, Materials Research Society, Pittsburgh, PA, pp. 171-176. 

Dickinson, J. T. Doering, D. L. Langford, S. C. In Atomic and Molecular Processing of Electronic and Ceramic Materials Preparation, Characterization, and Properties, Aksay, I. H. et al. Eds. Materials Research Society Pittsburgh, 1988, pp 39-46. 

Barium Minerals Barite (BaS04) and witherite (BaCOs) are commonly used to supply barium in ceramic formulations. Purified barium carbonate, made by dissolution and repredpitation, is used most frequently in ceramic processes and as fluxing compounds in the grazes, ass, and enamels of electronic ceramics and in heavy day products to prevent scumming. The use of these minerals have the drawback that upon heating they give off gas, which can cause cracks. 

Samuels "Atomic and Molecular Processing of Electronic and ceramic Materials Preparation, Characterization and Properties" Materials Research Society, Pittsburgh, 1988, 127. 

H. Windlass, P. M. Raj, S. K. Bhattacharya, and R. R. Tummala, Processing of Polymer-Ceramic Nanocomposites for System-on-Package Application , Proceeding of2001 Electronic Components and Technology Conference, (2001), pp. 1201-1206. 

The many and varied chemical preparation routes for the production of electronic ceramic powders are too numerous to discuss in detail here. Typical precursors include chlorides organometallics such as oxalates and alcohol-based complexes The processes involved include hydrothermal synthesis coprecipitation precipitation of one component followed by coatings of successive dopants, sol-gel preparation polyiner1sation etc. It will be some time before the benefits of the processes can be assessed. Questions concerning their flexibility for producing different compositions, the quality of results and the problems of cost and scaling up still need to be resolved. What is not in doubt is that chemical methods offer potentially much improved powders compared to those prepared by traditional mixed oxide routes. 

Fabrication technologies for ah electronic ceramic materials have the same basic process steps, regardless of the appHcation powder preparation, powder processing, green forming, and densiftcation. 

---