Method for forming bumps on a substrate

Details Method for forming bumps on a substrate Method for forming bumps on a substrate

1997-05-01

1998-06-09

Ramsey, Kenneth J.

Metal fusion bonding

Process

Plural joints

2282481, 228254, 437183, B23K 3500, H01L 21441

Patent

active

057622590

ABSTRACT:
Solder bumps are formed on a substrate, such as a semiconductor die (28) or wafer, using a screen printing and reflow operation. Solder paste (18) is screened into openings (14) of a stencil (10). The paste is reflowed within the stencil to produce a solder preform (22). The stencil and solder preforms are then aligned over the substrate to be bumped so that the preform aligns with a metal pad (30) on the substrate. The solder preforms are again reflowed, and the solder within the openings of the stencil is drawn onto the metal pad. To facilitate the transfer of the solder from the stencil to the metal pad, a second stencil (12) can be used to form a protrusion (27) on the solder preform. The protrusion contacts the metal pad during the transfer reflow operation to facilitate removing the solder from the stencil.

REFERENCES:
patent: 4865654 (1989-09-01), McLellan
patent: 5048747 (1991-09-01), Clark et al.
patent: 5219117 (1993-06-01), Lin
patent: 5281684 (1994-01-01), Moore et al.
patent: 5346118 (1994-09-01), Degani et al.
patent: 5492266 (1996-02-01), Hoebener et al.
John R. Morris and Thaddeus Wojcik, "Stencil Printing of Solder Paste for Fine-Pitch Surface Mount Assembly", IEEE Transact ions on components, Hybrids and Manufacturing Technology, Sep. 1991, vol. 14, No. 3, pp. 560-566.

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