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Browse Prior Art Database

Via Hole Cleaning by Microwave Etching With a Microwave Plasma Extender

IP.com Disclosure Number: IPCOM000039492D
Original Publication Date: 1987-Jun-01
Included in the Prior Art Database: 2005-Feb-01
Document File: 2 page(s) / 112K

Publishing Venue

IBM

Related People

Chou, NJ: AUTHOR [+5]

Abstract

This article describes a microwave etching technique which can effectively clean via holes in multilayer printed circuit (PC) boards after they are formed by mechanical and/or laser drilling. (Image Omitted) The technique disclosed herein is schematically shown in Fig. 1. Microwave power is applied to cavity 1. By means of coupling, a plasma is produced in the microwave extender 2, which can move vertically in the view part table 3. The extender is equipped with a sealing ring 6, at its end. The PC board 5 is mounted on a holder frame capable of executing x and y translating motions in the vacuum chamber 4. Etching and cleaning of via holes occurs when the extender is lowered to form intimate contact with the PC board and plasma is forced through the via holes.

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Via Hole Cleaning by Microwave Etching With a Microwave Plasma Extender

This article describes a microwave etching technique which can effectively clean via holes in multilayer printed circuit (PC) boards after they are formed by mechanical and/or laser drilling.

(Image Omitted)

The technique disclosed herein is schematically shown in Fig. 1. Microwave power is applied to cavity 1. By means of coupling, a plasma is produced in the microwave extender 2, which can move vertically in the view part table 3. The extender is equipped with a sealing ring 6, at its end. The PC board 5 is mounted on a holder frame capable of executing x and y translating motions in the vacuum chamber 4. Etching and cleaning of via holes occurs when the extender is lowered to form intimate contact with the PC board and plasma is forced through the via holes.

With x, y motion of the PC board and z motion of the extender, the entire area of the board can be accessed and cleaned. An alternative but less desirable way is for the board to execute x, y, z motions with the extender fixed in space. The effectiveness of the disclosed technique was demonstrated in a simple experimental arrangement shown in Fig. 2. A plasma in a gas mixture of 10% CF4 and 90% O2 was produced in quartz tube 10 through cavity coupling 11. The plasma passes 30 mil diameter holes drilled in a piece 12 cut out of a PC board. The microwave power used was approximately 100 watts (not optimized), and etching lasted three min...