Metal fusion bonding – Process – Critical work component – temperature – or pressure
Patent
1989-02-09
1990-05-01
Godici, Nicholas P.
Metal fusion bonding
Process
Critical work component, temperature, or pressure
357 71, 228123, H01L 2348
Patent
active
049223224
ABSTRACT:
In a semiconductor device tape assembly bonding process the fingers of a copper tape are reflow soldered to metal bumps located on the semiconductor device. First, the semiconductor wafer is covered with a conductive film composed of thin layers of alumimum, nickel-vanadium alloy and gold. The bumps are then created by electroplating gold through openings in a photoresist mask. The gold bumps are overcoated with a controlled thickness tin layer and the tin is overcoated with a thin gold anticorrosion layer. The copper assembly tape is coated with a thin gold layer and are lightly pressed against the bumps by means of a thermode. The thermode is quickly heated to a temperature well above the gold-tin eutectic melting temperature and then rapidly cooled. The tin layer on the bump will combine with the adjacent gold to form a liquid phase eutetic which will form and contact both the copper finger and the gold bump. Upon cooling the eutectic melt will solder the finger to the bump. Since all of the tin is combined with the gold there is no metallic tin left in the system and the problems of tin whiskers and tin electromigration are avoided.
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Glenn Michael A.
Godici Nicholas P.
Heinrich Samuel M.
National Semiconductor Corporation
Patch Lee
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