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Method and apparatus for jetting, manufacturing and attaching uniform solder balls

United States Patent

5,855,323
January 5, 1999
View the Complete Patent at the US Patent & Trademark Office
Sandia National Laboratories - Visit the Intellectual Property Management and Licensing Website
An apparatus and process for jetting molten solder in the form of balls directly onto all the metallized interconnects lands for a ball grid array package in one step with no solder paste required. Molten solder is jetted out of a grid of holes using a piston attached to a piezoelectric crystal. When voltage is applied to the crystal it expands forcing the piston to extrude a desired volume of solder through holes in the aperture plate. When the voltage is decreased the piston reverses motion creating an instability in the molten solder at the aperture plate surface and thereby forming spherical solder balls that fall onto a metallized substrate. The molten solder balls land on the substrate and form a metallurgical bond with the metallized lands. The size of the solder balls is determined by a combination of the size of the holes in the aperture plate, the duration of the piston pulse, and the displacement of the piston. The layout of the balls is dictated by the location of the hooks in the grid. Changes in ball size and layout can be easily accomplished by changing the grid plate. This invention also allows simple preparation of uniform balls for subsequent supply to BGA users.
Yost; Frederick G. (Cedar Crest, NM), Frear; Darrel R. (Albuquerque, NM), Schmale; David T. (Albuquerque, NM)
Sandia Corporation (Albuquerque, NM)
08/ 746,602
November 13, 1996
GOVERNMENT RIGHTS The Government has rights to this invention pursuant to Contract No. DE-AC04-76DP00789 awarded by the U.S. Department of Energy.