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Plating Rate Monitor of High Reliability

IP.com Disclosure Number: IPCOM000062255D
Original Publication Date: 1986-Oct-01
Included in the Prior Art Database: 2005-Mar-09
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Chu, FR: AUTHOR [+5]

Abstract

We have developed a quartz monitor which, when it is immersed in a plating bath, measures the rate at which plating is deposited on it. The essential element is a quartz crystal oscillating in the shear mode. The crystal must be mounted as described below so that the monitor is reliable under long time immersion at high temperatures (approaching 100 degrees C). 1. Only one face of the crystal must be exposed to the solution to prevent shorting of the electrodes. 2. The mounting must not introduce strain in the crystal or otherwise constrain its oscillation. 3. Electrical contacts must be reliable but not stress the crystal. 4. The probe housing must be leakproof even with frequent immersions and large temperature changes. 5.

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Plating Rate Monitor of High Reliability

We have developed a quartz monitor which, when it is immersed in a plating bath, measures the rate at which plating is deposited on it. The essential element is a quartz crystal oscillating in the shear mode. The crystal must be mounted as described below so that the monitor is reliable under long time immersion at high temperatures (approaching 100 degrees C). 1. Only one face of the crystal must be exposed to the solution to prevent shorting of the electrodes. 2. The mounting must not introduce strain in the crystal or otherwise constrain its oscillation. 3. Electrical contacts must be reliable but not stress the crystal. 4. The probe housing must be leakproof even with frequent immersions and large temperature changes. 5. The crystal must be located close to the oscillator circuitry to minimize shunting capacitance effe

The illustrated design accomplishes all the requirements. It: 1. Exposes only one side of the crystal to the solution. 2. Holds the crystal between two "O" rings in such a way as to stress it evenly on its periphery and maintain its flatness. 3. Makes reliable contact between the leads of the P.C. Board and the crystal even though the contact pressure is less than 10 grams per contact; the key is the use of proper material for the springs (platinum or gold plated copper) and giving them a special shape which holds them steady in spite of vibrations. 4. Avoids differential expansions when the monitor is i...