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:
Aug. 23, 2011
Filed:
Apr. 24, 2007
Tasao Soga, Hitachi, JP;
Daisuke Kawase, Mito, JP;
Kazuhiro Suzuki, Mito, JP;
Eiichi Morisaki, Kasama, JP;
Katsuaki Saito, Iwaki, JP;
Hanae Shimokawa, Yokohama, JP;
Tasao Soga, Hitachi, JP;
Daisuke Kawase, Mito, JP;
Kazuhiro Suzuki, Mito, JP;
Eiichi Morisaki, Kasama, JP;
Katsuaki Saito, Iwaki, JP;
Hanae Shimokawa, Yokohama, JP;
Hitachi, Ltd., Tokyo, JP;
Abstract
Use of Pb-free solder has become essential due to the environmental problem. A power module is formed by soldering substrates with large areas. It is known that in Sn-3Ag-0.5Cu which hardly creeps and deforms with respect to large deformation followed by warpage of the substrate, life is significantly shortened with respect to the temperature cycle test, and the conventional module structure is in the situation having difficulty in securing high reliability. Thus, the present invention has an object to select compositions from which increase in life can be expected at a low strain rate. In Sn solder, by doping In by 3 to 7% and Ag by 2 to 4.5%, the effect of delaying crack development at a low strain rate is found out, and as a representative composition stable at a high temperature, Sn-3Ag-0.5Cu-5In is selected. Further, for enhancement of reliability, a method for partially coating a solder end portion with a resin is shown.