Active solid-state devices (e.g. – transistors – solid-state diode – Lead frame – With heat sink means
Reexamination Certificate
1999-12-07
2002-02-19
Graybill, David E. (Department: 2814)
Active solid-state devices (e.g., transistors, solid-state diode
Lead frame
With heat sink means
C257S676000, C257S692000, C257S713000, C257S730000, C257S796000, C257S732000
Reexamination Certificate
active
06348727
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to semiconductor device packages and more specifically relates to a novel package having a plastic housing and a conductive tab.
Discrete semiconductor devices such as diodes are available for high current applications in a variety of package styles. For example, a standard package known as a TQ-247 package is available at low cost for high current application while higher current devices are generally housed in more expensive metal cases or in power modules. There is a need for a high current package of lower cost than the metal package or module and a low cost package of higher current capacity than the TQ-247. In particular, a need exists for a low cost package for Schottky diodes with a rated voltage of about 45 volts and rated current of 100 to 175 amperes. Similarly, a need exists for such packages for fast recovery diodes and standard rectifiers having reverse voltages up to about 1200 volts or higher and forward currents of 70 to 85 amperes.
BRIEF DESCRIPTION OF THE INVENTION
In accordance with the present invention, a novel device package is provided in which a lead frame has a heat sink portion for receiving one or more die and an oppositely extending thin flat tab in a plane displaced from the plane of the heat sink. The heat sink portion and die mounted thereon is encapsulated in plastic with the heat sink having an extension through one wall of the plastic housing and the thin flat tab extends from an opposite end wall of the housing. Significantly, the thin tab has a pair of slots closely spaced from the housing wall to limit the transfer of stress from the tab to the housing which might chip or crack the housing.
The novel package provides a sturdy low cost high current device with a low profile and an excellent die-to-footprint ratio. The thin extending exposed tab provides an optimum connection of high-current capability and efficient heat sinking. The tab may also contain printed circuit board (PCB) insertion fingers so that the power density of existing circuits can be easily increased with little or no printed circuit board changes. The package also features large creepage distance, low internal resistance, and low stray inductance, ensuring optimum performance in high and low voltage applications.
REFERENCES:
patent: 3893161 (1975-07-01), Pesak, Jr.
patent: 4259685 (1981-03-01), Romano
patent: 5661342 (1997-08-01), Kawamodo
Ewer Peter R.
Guerra Alberto
Westmarland Paul C.
Graybill David E.
International Rectifier Corporation
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