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Gas Plasma Cleaning Process for Multiwire Boards

IP.com Disclosure Number: IPCOM000045495D
Original Publication Date: 1983-Apr-01
Included in the Prior Art Database: 2005-Feb-07
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Horwath, R: AUTHOR [+2]

Abstract

This article describes a gas plasma process for cleaning holes drilled through multiwire boards and for etching back wire insulation to provide a better mechanical bond between the wire ends and plating material deposited in the drilled holes. The process, which includes an intermediate cooling step, replaces a costly and potentially hazardous potassium permanganate/chromic acid wet process.

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Gas Plasma Cleaning Process for Multiwire Boards

This article describes a gas plasma process for cleaning holes drilled through multiwire boards and for etching back wire insulation to provide a better mechanical bond between the wire ends and plating material deposited in the drilled holes. The process, which includes an intermediate cooling step, replaces a costly and potentially hazardous potassium permanganate/chromic acid wet process.

STEP 1 - Dry Cure. The board to be cleaned is oven-baked at a temperature in the range of 250 degrees (120 degrees C) for a length of time sufficient to remove moisture, and finally both the board material and any adhesive exposed by drill holes are cured.

STEP 2 - Gas Plasma - First Burn Cycle. The board is placed in a standard parallel plate gas plasma machine which is flooded with a roughly two to one mixture of oxygen and carbon tetrafluoride. RF power is applied for a limited period of time. During this burn cycle, the majority of drill smears are removed and 25%-50% of the necessary amount of insulation is etched back from the wire end.

STEP 3 - Gas Plasma Cooling Cycle. To prevent excess heat buildup up, the first burn cycle is followed by a cooling cycle of substantially the same duration. The RF power is turned off, and nitrogen is pumped through the plasma chamber.

STEP 4 - Gas Plasma Second Burn Cycle. The cooling cycle is followed by a second burn cycle having substantially the same parameters as the first burn cycl...