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Recovery Process for Wafers That Missed the BLM Operation

IP.com Disclosure Number: IPCOM000043971D
Original Publication Date: 1984-Oct-01
Included in the Prior Art Database: 2005-Feb-05
Document File: 1 page(s) / 11K

Publishing Venue

IBM

Related People

Boyar, S: AUTHOR [+2]

Abstract

A process is described in this article for removing Pb-Sn solder-balls and associated debris inadvertently deposited on wafers lacking the required underlay metallurgy (BLM operation). This metallurgy is necessary to electrically and mechanically connect terminal solder pads to chips, its omission resulting in defective connections. Wafers exhibiting this problem can be recovered successfully for return to normal terminal metal processing starting with the BLM operation, if removed prior to reflow and reworked by the process here disclosed. The Pb-Sn pads are first removed from the wafer by etching with 1:1 acetic acid/hydrogen-peroxide solution for approximately five minutes. Any remaining residues (lead oxides, etc.) on the quartz can be cleaned by etching with 5:1 BHF = 1.2% glycerine for one-half minute at 30ŒC.

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Recovery Process for Wafers That Missed the BLM Operation

A process is described in this article for removing Pb-Sn solder-balls and associated debris inadvertently deposited on wafers lacking the required underlay metallurgy (BLM operation). This metallurgy is necessary to electrically and mechanically connect terminal solder pads to chips, its omission resulting in defective connections. Wafers exhibiting this problem can be recovered successfully for return to normal terminal metal processing starting with the BLM operation, if removed prior to reflow and reworked by the process here disclosed. The Pb-Sn pads are first removed from the wafer by etching with 1:1 acetic acid/hydrogen-peroxide solution for approximately five minutes. Any remaining residues (lead oxides, etc.) on the quartz can be cleaned by etching with 5:1 BHF = 1.2% glycerine for one-half minute at 30OEC. This process assures complete removal of Pb-Sn from the wafer, thereby precluding any adverse reaction between the solder and the aluminum-copper contacts during the reflow operation as well as preventing contamination of the evaporator during follow-on sputter cleaning.

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