Browse Prior Art Database

Improved Microstructure of Bumped Tape for TAB Application

IP.com Disclosure Number: IPCOM000038431D
Original Publication Date: 1987-Jan-01
Included in the Prior Art Database: 2005-Jan-31
Document File: 2 page(s) / 74K

Publishing Venue

IBM

Related People

Kang, SK: AUTHOR

Abstract

Tape Automated Bonding (TAB) is one of the advanced packaging technologies available to the application of very large-scale integration (VLSI). Depending upon the location of bumps, which serve as a stand- off for the interconnection, there are two different schemes of TAB: bumped-chip and bumped-tape TAB (BTAB). Copper bumps used in BTAB have poor bondability, compared to gold bumps mostly used in the bumped-chip TAB. The bumped tape is produced either by etching off a thicker copper beam tape or by electroplating bumps onto a copper tape. Because of the fine beam structure of very many input/output leads, the copper tape is desired to have a high modulus and strength.

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Improved Microstructure of Bumped Tape for TAB Application

Tape Automated Bonding (TAB) is one of the advanced packaging technologies available to the application of very large-scale integration (VLSI). Depending upon the location of bumps, which serve as a stand- off for the interconnection, there are two different schemes of TAB: bumped-chip and bumped-tape TAB (BTAB). Copper bumps used in BTAB have poor bondability, compared to gold bumps mostly used in the bumped-chip TAB. The bumped tape is produced either by etching off a thicker copper beam tape or by electroplating bumps onto a copper tape. Because of the fine beam structure of very many input/output leads, the copper tape is desired to have a high modulus and strength. This requirement for mechanical properties is unfavorable in terms of bondability, because it requires high temperatures and pressures during thermocom pression bonding of high strength materials. This method produces an improved bumped tape by controlling the microstructure of electroplated copper for both the beam and the bump. The resultant bumped-tape has a dual microstructure, in which the copper beam has a high modulus/ strength, while the copper bump has a low modulus/strength. Mechanical properties of electroplated metals vary greatly by controlling the electroplating conditions, i.e., plating solution, addition agents, voltage, current density, impurities, etc. Extensive literature is available on the subject of electroplated Cu (for example, W. H. Safranek, Handbook of the Properties of Electrodeposited Metals and Alloys, American Elsevier, 1974). A method for the improved BTAB structure is a double electroplating scheme, as shown schematically in Fig. 1. Initially, the Cu electroplating conditions are chosen for producing strong/rigid Cu beams, and then the plating conditions are changed to produce soft Cu bumps 10 on the hard Cu beams 11. Fig. 1 shows the dual microstructure of a bumped tape showing large grains of soft C...