(io) Patent Number: US RE37,707 E
(45) Date of Reissued Patent: May 21,2002
4,963,975 A 10/1990 Sawaya 357/81
4,965,642 A * 10/1990 Titterington 257/787
5,073,817 A * 12/1991 Ueda 257/787
FOREIGN PATENT DOCUMENTS
JP 0124678 9/1979
JP 0053752 3/1986
Hitachi Power Mosfet Data Book, Aug., 1995, #D11, p. 201, 2SK511, Silicon N-Channel MOS FET. International Rectifier, Product Digest, Short Form Catalog 90, HEXFET Power MOSFETs Case Outlines, pp. 1 and 140, 1990.
* cited by examiner
Primary Examiner—Sheila V. Clark
(74) Attorney, Agent, or Firm—Lisa K. Jorgenson; James H. Morris
An improved leadframe for packages of integrated power devices which, by virtue of its configuration, allows to press the dissipator on the bottom of the shell during the molding of the plastic case, without the dissipator having exposed portions of its inner face (which is in contact with the chip). In order to achieve this, the leadframe according to the invention comprises a monolithic body which defines a perimetric frame, the leads and the dissipator. The dissipator extends in a depressed plane with respect to the frame and is connected to the frame and to the leads in at least three step-like points which are mutually spaced and non-aligned. During the molding of the plastic case, a pressure is exerted on the frame and is transmitted to the dissipator by the three step-like points, so that the dissipator is effectively pressed flat against the bottom of the mold without using pushers which pass through the plastic case.
39 Claims, 5 Drawing Sheets