The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Dec. 10, 2002
Filed:
Sep. 21, 2001
Chon C. Lei, Poughkeepsie, NY (US);
Jac A. Burke, Lake Katrine, NY (US);
William F. Beausoleil, Hopewell Junction, NY (US);
N. James Tomassetti, Kingston, NY (US);
Lawrence A. Thomas, West Hurley, NY (US);
Tak-kwong Ng, Hyde Park, NY (US);
Michael Kessler, Herrenberg, DE;
International Business Machines Corporation, Armonk, NY (US);
Abstract
Chips requiring high temperature reflow for attachment to a module substrate are attached first and then a eutectic water soluble solder paste and/or water soluble flux is dispensed on both the TSOP and the PBGA chip pads instead of using the paste screening techniques. The dispensing is done by injecting solder on the solder sites individually. Characteristics of the solder paste used is that it must be fluid enough to be injected onto the individual sites yet have enough body that it remains in place and does not run from site to site once dispensed. A paste capable of providing such characteristics is one having: a ) a very fine particle size in the range of 400 to 500 mesh and preferably between 400 and 450 mesh; b) a low viscosity (below 500 k centerpoise and preferably between 425 to 375 cps); and c) a solid content of 86% or lower and preferably between 84 and 80%. The chips to be joined to the module using low temperature module joining are then placed on the module substrate surface and then put in an oven for reflow to attach these chips to the surface. After the joining process, the modules are cleaned by spraying deionized water on them to remove any flux or solder residues and the modules are electrically tested to determine if the joining process has resulted in connection with the proper mechanical and electrical characteristics.