United States Patent 3,458,925
August 5, 1969

Method Of Forming Solder Mounds On Substrates
John Napier
Raeman P. Sopher
Paul A. Totta
David DeWitt
Clarence Karan

Filed January 20, 1966
Image of US PATENT 3,458,925

Abstract of the Disclosure

A method of forming mounds of solder on integrated circuit chips having lands thereon comprising masking the surface of the chips so as to expose only the land and the area immediately thereround, evaporating a layer of solder in the mask and subsequently heating the solder above its melting point whereby the solder de-wets the area around the lands and contracts to form solder mounds on the lands.
Figure descriptions: cover graphic

  • Figure 1 shows a cut-away side view of an integrated circuit chip with a ball limiting land formed on one surface thereof.
  • Figure 2 shows the same land and chip after a layer of solder has been evaporated thereon through a metal mask.
  • Figure 3 shows the finished solder mound after the originally evaporated layer has been re-melted to de-wet the ceramic.
  • Figures 4a and 4b illustrate how different sized solder mounds can be formed by controlling the diameters of the evaporated solder circles.
  • Figure 5 shows a circuit chip provided with both active and passive solder mounds assembled to a mounting board.

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3,310,711 03/1967 Hangstefer 2,781,282 02/1957 Morgan 3,292,240 12/1966 McNutt 3,235,959 02/1966 Bartoszak 3,293,076 12/1966 Allen 3,261,713 07/1966 Groten 3,303,393 02/1967 Hymes 3,286,340 11/1966 Kritzler 3,322,517 05/1967 Miller
National Museum of American History
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