	US 7,523,852 B2
	Solder interconnect structure and method using injection molded solder
Stephen L. Buchwalter, Hopewell Junction, N.Y. (US); Claudius Feger, Poughkeepsie, N.Y. (US); Peter A. Gruber, Mohegan Lake, N.Y. (US); Sung K. Kang, Chappaqua, N.Y. (US); Paul A. Lauro, Brewster, N.Y. (US); and Da-Yuan Shih, Poughkeepsie, N.Y. (US)
Assigned to International Business Machines Corporation, Armonk, N.Y. (US)
Filed on Dec. 05, 2004, as Appl. No. 11/5,557.
Prior Publication US 2006/0118604 A1, Jun. 08, 2006
Int. Cl. B23K 35/12 (2006.01)

U.S. Cl. 228—246 [228/56.3]

13 Claims

1. A method for connecting an electrical device having first electrical connection surfaces to a substrate having corresponding second electrical connection surfaces, comprising:

forming a plurality of columns at least partially of solder so as to be electrically connected to one of said first electrical connection surfaces and said second electrical connection surfaces; wherein electrical connections are made between first ends of said plurality of columns and said first electrical connection surfaces;

forming electrical connections between said second electrical connection surfaces and second ends of respective ones of said plurality of columns;

mixing particles with solder when the solder is in a molten state;

forming said columns in cavities of a mold plate by injection molded soldering of said solder, said columns having an aspect ratio of between 1.5 and ten;

coating, by electroplating, elongate metal conductors of a material other than solder with a solder-wettable metal;

placing said metal conductors within respective columns in said mold plate prior to injecting solder into said cavities;

aligning, with an array of cavities in the mold plate, an array of through-holes in a plate, the through-holes being slightly larger in diameter than the conductors;

removably fastening the plate to the mold plate;

placing conductors in the vicinity of the through-holes;

agitating the conductors over the through-holes until a respective conductor moves into each of the cavities;

providing first optical components on said electrical device and second optical components on said substrate, said first optical components and said second optical components being positioned with respect to one another so that there is a respective optical path between each one of said first optical components and a respective one of said second optical components, said optical paths having no underfill material; wherein:

said columns are formed of a first solder with a first melting point temperature, further comprising soldering said columns to the other of said first surfaces and second surfaces with a second solder having a second melting point temperature lower than said first melting point temperature; and

said second solder is applied to at least one of said first electrical connection surfaces and said second electrical connection surfaces prior to connecting second ends of said columns to said first surface and said second surfaces.