Metal fusion bonding – Process – Preplacing solid filler
Patent
1997-07-09
1999-11-16
Ryan, Patrick
Metal fusion bonding
Process
Preplacing solid filler
2282481, 228224, 118504, 118505, B23K 3512, B23K 3102
Patent
active
059841664
ABSTRACT:
A method by which low melting point solder for reflow connection of components is formed on select fine and coarse pitch contacts of a printed circuit board simultaneously. A template with openings to select fine pitch circuit board contacts is placed in contact with fine pitch contacts. The fine and coarse pitch contacts of the board are exposed through holes in a stencil characterized in its ability to withstand solder reflow temperatures, not be wettable by solder, and have a coefficient of thermal expansion relatively matching the printed circuit board. Low temperature solder paste is screen deposited into the stencil openings. The stencil is removed and a mesh is fixedly positioned on the board, the solder paste retained by the stencil pattern is reflowed to selectively form on the underlying contacts of the printed circuit board. Thereafter, according to a preferred practice of the invention, the mesh is removed from the board and the board is subjected to previously practiced depositions of flux and paste in preparation for fine and coarse pitch component placement and ensuing solder reflow. Alternate practices of the invention involve concurrent deposition of fine pitch solder through a template and coarse pitch solder in the conventional manner in the absence of mesh with removal of the stencil prior to solder reflow.
REFERENCES:
patent: 5395040 (1995-03-01), Holzmann
patent: 5460316 (1995-10-01), Hefele
patent: 5492226 (1996-02-01), Hoebener et al.
patent: 5681387 (1997-10-01), Schmidt
patent: 5804248 (1998-09-01), Hewett
patent: 5813331 (1998-09-01), Tan et al.
patent: 5825629 (1998-10-01), Hoebener et al.
Gamino Carlos
Holzmann Richard T.
Mask Technology, Inc.
Ryan Patrick
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