Metal fusion bonding – Process – Preplacing solid filler
Patent
1999-09-30
2000-12-12
Ryan, Patrick
Metal fusion bonding
Process
Preplacing solid filler
228254, B23K 3102, B23K 3514
Patent
active
061586501
ABSTRACT:
Methods 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 solder paste retained by the template and stencil pattern is shaped during reflow to selectively form on the underlying contacts of the printed circuit board. Thereafter the board is subjected to previously practiced depositions of flux in preparation for fine and coarse pitch component placement and ensuing solder reflow. An alternate practice of the invention involves a method for controlling the volume of solder on select electrically conducting contacts of a substrate. A shaped solder deposit formed by a method which comprises: positioning a template in intimate contact with a substrate for shaping the side wall and height of a solder deposit; depositing solder paste within the confines of said template; heating said deposited solder paste to drive off volatile components and soften solder; and cooling the thus deposited solder to form the shaped solder deposit within said template. The shaped solder deposit formed by the above process.
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Holzmann Richard T.
Mask Technology, Inc.
Ryan Patrick
Stoner Kiley
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