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Wettability Test for Alumina Powder in MLC, as an Indicator of Sodium Content on the Surface

IP.com Disclosure Number: IPCOM000049886D
Original Publication Date: 1982-Aug-01
Included in the Prior Art Database: 2005-Feb-09
Document File: 2 page(s) / 29K

Publishing Venue

IBM

Related People

Verkuil, RL: AUTHOR

Abstract

The sodium content on the surface of alumina powder is a significant contributor to the degree of MLC (multilayer ceramic) module shrinkage during firing. This proposal provides a convenient method for measuring sodium content by means of wetting the powder surface with a controlled humidity environment and examining the effective change in the dielectric constant of the alumina powder.

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Wettability Test for Alumina Powder in MLC, as an Indicator of Sodium Content on the Surface

The sodium content on the surface of alumina powder is a significant contributor to the degree of MLC (multilayer ceramic) module shrinkage during firing. This proposal provides a convenient method for measuring sodium content by means of wetting the powder surface with a controlled humidity environment and examining the effective change in the dielectric constant of the alumina powder.

The apparatus for the measurement is shown in the drawing. In a humidity chamber 1 a parallel plate capacitor is placed which is formed by compressing a fixed weight of alumina powder 2 to a fixed thickness between a metal plate 3 and a metal mesh 4 of fixed diameter. A reference capacitor C is connected in series with the powder-filled capacitor and a variable frequency AC voltage source, Vin, is used to determine the frequency-dependent voltage division of the resultant network. The frequency of Vin is adjusted until the amplitude of Vout is equal to 0.5 Vin. This resultant frequency is defined as polarization frequency Fp. Measurements have shown a good agreement between Fp and the sodium content measured by a standard leaching technique with a correlation factor of
0.947.

The principle of operation of the measurement is based on the space charge polarization effect due to sodium ions that are free to move on the moist surface of the powder. The relatively slow ion motion produces an ef...