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Ultrasonic Removal of Broken Drill Bits

IP.com Disclosure Number: IPCOM000084803D
Original Publication Date: 1976-Jan-01
Included in the Prior Art Database: 2005-Mar-02
Document File: 1 page(s) / 11K

Publishing Venue

IBM

Related People

Reynolds, MJ: AUTHOR

Abstract

Frequently, in drilling printed-circuit boards, drill bits are broken off and remain in the printed-circuit board. It then becomes necessary to remove the broken drill bits, preferably with minimal damage to the board. This problem becomes more complicated with smaller diameter holes, especially where there is a high-aspect ratio between board thickness and hole diameter, e.g., greater than 5:1.

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Ultrasonic Removal of Broken Drill Bits

Frequently, in drilling printed-circuit boards, drill bits are broken off and remain in the printed-circuit board. It then becomes necessary to remove the broken drill bits, preferably with minimal damage to the board. This problem becomes more complicated with smaller diameter holes, especially where there is a high-aspect ratio between board thickness and hole diameter, e.g., greater than 5:1.

Most of the broken drill bits are at varying depths in the board when the break occurs. To remove the broken bit, the following procedure is followed. First, a hole is drilled from the back side of the board until contact is made with the broken drill bit. The printed-circuit board is then positioned upside down and an ultrasonic tip, smaller in diameter than the hole size, is inserted into the hole.

The ultrasonic tip is lowered until it makes contact with the broken drill bit and then the ultrasonic power supply is energized, creating a high-frequency vibration in the tip that pushes on the broken drill bit. This technique is continued until the broken drill bit is pushed out of the board.

In a typical application with a hole size on the order of 20 mils, this technique has proved satisfactory where the ultrasonic tip is about 1 mil smaller in diameter than the hole and the ultrasonic power supply provided energy at a frequency of 20 kilohertz.

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