Browse Prior Art Database

Removal Technique

IP.com Disclosure Number: IPCOM000089491D
Original Publication Date: 1977-Nov-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 2 page(s) / 52K

Publishing Venue

IBM

Related People

Johnson, C: AUTHOR [+3]

Abstract

At least certain integrated circuit chips use pad limiting metallurgy (PLM) that has a chrome-copper-gold metal pattern (Fig. 1) with a lead-tin or lead-indium pad. These pads are used to connect the chip to a module via flip chip bonding. At times, the pads or a single pad must be removed.

This text was extracted from a PDF file.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 100% of the total text.

Page 1 of 2

Removal Technique

At least certain integrated circuit chips use pad limiting metallurgy (PLM) that has a chrome-copper-gold metal pattern (Fig. 1) with a lead-tin or lead-indium pad. These pads are used to connect the chip to a module via flip chip bonding. At times, the pads or a single pad must be removed.

The disclosed technique allows a single pad or multiple pads to be removed without using known hand/masking/etching techniques. A positive potential is applied to the pad to be removed. A negative potential is placed on the quartz insulator adjacent to the pad to be removed. A weak electrolyte is applied to the region between the pad and the negative probe. The electrolyte can extend beyond the pad to be removed, but the reaction will be limited to the pad that is probed. The reaction is electrochemical.

Chromium/chromium oxide mixture deposited as a thin film (~~1000 Angstroms) by an evaporation process, or the like, can be converted into a liquid. The technique (Fig. 2) involves applying a voltage of 1 volt to 20 volts or more between the chrome film and an electrode. A weak electrolyte is applied between the chrome film and the electrode. The positive potential is on the chrome film. The chrome film will slowly convert to a liquid with the reaction front heading towards the contact on the chrome film. The liquified chrome may then be removed with water.

1

Page 2 of 2

2

[This page contains 3 pictures or other non-text objects]