Preparation And Research Of Dielectric Pastes For 304 Stainless Steel Substrate

This paper came into being on the base of the attention and the sufficiently survey about the newest development of the thick film material of the world. At the same time, the actual state of the work group and the market demanding of the new pattern thick film heating element were considered. The 304 stainless-steel was chosen to be the substrate of the thick film circuit. The fundamental work about the dielectric paste using for the substrate was studied and the dielectric pastes based on 304 stainless-steel were designed and prepared.According to the theories about glass and the TEC (Coefficient of thermal expansion) of the 304 stainless-steel, glass in dielectric paste is made of the compositions of BaO-Al₂O₃-SiO₂. The sintering mechanism and the crystallization kinetics of high Ba containing BAS glass has been analyzed with DTA, XRD, SEM/EDS as well as tested insulation property. The influencing factors of the TEC and the insulation properties of the dielectric were pointed out.A series of the dielectric thick film pastes for the 304 stainless-steel were prepared by designed composition of glass. These pastes can became dielectric on stainless-steel by screen printed and sintered. The optimal composition was chosen with the linking strength between the stainless-steel and the dielectric and the metamorphosis of the sintered substrate.The results showed that the sintered dielectric was a kind of glass-ceramics. The crystals in the dielectric included Hexacelsian and Celsian. Celsian would affect the insulation properties of the dielectric seriously. The adding of ZrO₂ could suppress the appearance of the Celsian during the sintering process and then improve the insulation properties of the dielectric, result in stainless-steel satisfy the thick film circuit's needs. The glass in the optimal composition had a transition temperature of 750℃ and a start nucleating temperature of 840℃. When the thickness of sintered dielectric layer was more than 90μm, the layer could resist 2kV, the substrate accorded with GB1408 —78. The dielectric pastes manufactured in this paper could screen-print on the 304 stainless-steel directly and then became a production by sintered in stove. The pastes were fit for industrialized manufacture.