Semiconductor device manufacturing: process – Packaging or treatment of packaged semiconductor
Reexamination Certificate
2000-05-03
2001-09-18
Potter, Roy (Department: 2822)
Semiconductor device manufacturing: process
Packaging or treatment of packaged semiconductor
C438S112000, C438S124000
Reexamination Certificate
active
06291262
ABSTRACT:
FIELD OF INVENTION
The present invention relates to a package for semiconductor devices and, more specifically, to a novel surface mount TO-220 device package.
BACKGROUND OF THE INVENTION
The TO-220 package is a known industry standard. The package includes a thermally conductive base which is preferably metal and on which a semiconductor device is mounted with low thermal impedance between the device and the base. The device may also be electrically connected to the base. The semiconductor device and a portion of the frame are typically encapsulated by a resin material, which protects the device from its environment. A locking projection typically extends from the base to the outside of the protective epoxy and is fastened to the external mounting surface to draw heat from the device. Also included are lead terminals which extend outside the resin body and include bonding pads to which a wire bond connection is provided from the device to the leads.
In a surface mount device, the surface of the base that is adjacent to the circuit board and opposite from the device is exposed for electrical contact to the circuit board.
Typically, the leads are bent outside the resin body to contact the surface and provide electrical connection to the circuit board. This bend in the leads, however, can cause mechanical stresses in the resin body.
Moreover, two gauges of metal are typically used. A thick gauge metal is used for the base, and a thin gauge metal is used for the leads so that they may be bent. This use of two gauges increases the complexity of the manufacture of the package device.
SUMMARY OF THE INVENTION
The present invention provides for a surface mount TO-220 package in which the leads are bent prior to molding the resin body around the device and frame to minimize the mechanical stress on the leads. Also, a single gauge of lead frame material is used for both the leads and the main pad area, which minimizes material costs and reduces the height of the package body. The length of the leads outside of the package is also shortened. Though the combined length of the leads inside and outside the package is increased, the built-in resistance and inductance of the package is substantially reduced because the thickness of the leads is the same as that of the main pad area. The lead frame configuration also improves assembly yield. The package is suitable to be a drop-in replacement for existing surface mount design TO-220 type packages but can accept larger die sizes than existing size 4 die.
REFERENCES:
patent: 4987473 (1991-01-01), Johnson
patent: 5083368 (1992-01-01), Frank
patent: 5191403 (1993-03-01), Nakazawa
patent: 5291059 (1994-03-01), Ishitsuka et al.
patent: 6178628 (2001-01-01), Clemens
Kotani Hiroshi
Udagawa Hisao
International Rectifier Corp.
Ostrolenk Faber Gerb & Soffen, LLP
Potter Roy
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