Patent ID: 6348115
Filing Date: 2002-02-19
Classification: B32B,C04B,H01L

Abstract:
A method for forming a ceramic diaphragm structure comprising the steps of:a) providing a laminate, comprising: i) a ceramic green substrate having at least one window therethrough and a plurality of layers; and ii) a thin ceramic green sheet having at least one layer superposed on the ceramic green substrate to cover the at least one window; b) firing the laminate so that the ceramic green sheet provides a diaphragm portion protruding in a direction away from the at least one window; and c) subjecting the fired laminate to a second firing step under load; wherein the ceramic green substrate and the ceramic green sheet satisfy the formulae 1), 2) and 3): S(substrate)âˆ’S(sheet)&gE;âˆ’0.08{T70(substrate)âˆ’T70(sheet)}âˆ’1â€ƒâ€ƒ1) 0&lE;T70(substrate)âˆ’T70(sheet)&lE;300,â€ƒâ€ƒ2) andS(substrate)âˆ’S(sheet)&lE;20â€ƒâ€ƒ3) wherein S(substrate) and S(sheet) denote shrinkage rates (%) of the ceramic green substrate and the ceramic green sheet, respectively, and T70(substrate) and T70 (sheet) denote mid-sintering temperatures (Â° C.) of the ceramic green substrate and the ceramic green sheet, respectively, and an average mid-sintering temperature difference of the ceramic green substrate, shown by the following formula 4), is smaller than 0: 4)&it;â€ƒ&it;&Sum;n=1N&it;T70&af;(substrate)n&it;&Integral;tntn+1&it;Ã—&dd;xwherein N denotes the number of layers constituting the ceramic green substrate, T70(substrate)n denotes a mid-sintering temperature (Â° C.) of a layer positioned in the nth place from the bottom of the laminate in the ceramic green substrate having the ceramic green sheet thereon, and tn and tn+1 denote distances from the lower and upper surfaces, respectively, of the layer positioned in number n place to a neutral line of the substrate after firing the unitary laminate, using (âˆ’) for a surface under the neutral line and (+) for a surface over the neutral line, and an average shrinkage-rate difference of the ceramic green .substrate, shown by the following formula 5), is smaller than 0: 5)&it;â€ƒ&it;&Sum;n=1N&it;S&af;(substrate)n&it;&Integral;tntn+1&it;Ã—&dd;xwherein N denotes the number of layers constituting the ceramic green substrate, S(substrate)n denotes a shrinkage rate (%) of a layer positioned in the nth place from the bottom of the laminate in the ceramic green substrate having the ceramic green sheet thereon, and tn and tn+1 denote distances from the lower and upper surfaces, respectively, of the layer positioned in the nth place to a neutral line of the substrate after firing the unitary laminate, using (âˆ’) for a surface under the neutral line and (+) for a surface over the neutral line.