Active solid-state devices (e.g. – transistors – solid-state diode – Housing or package – With contact or lead
Reexamination Certificate
1997-03-12
2001-12-25
Chaudhuri, Olik (Department: 2814)
Active solid-state devices (e.g., transistors, solid-state diode
Housing or package
With contact or lead
C257S731000
Reexamination Certificate
active
06333550
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a surface mount semiconductor diode device.
BACKGROUND OF THE INVENTION
Surface mount semiconductor diode devices typically comprise a semiconductor element electrically mounted on a first surface of a heat sink. A second opposing surface of the heat sink provides a first contact for the device. A conductive tab or leg is coupled to an opposing surface of the semiconductor element and is bent so that an end of the tab is substantially coplanar with the first contact, the end forming the second contact of the device.
In the surface mount diode U5ZA27 manufactured by Toshiba, the tab is connected directly to the surface of the semiconductor element. However, it is also known, for example with the surface mount diode MR2535S supplied by Motorola, Inc., to have an additional heat sink coupled to the opposing surface of the semiconductor element with the tab connected to the heat sink.
With both such types of devices, the surface areas of the first and second contacts are significantly large. Having large contact surface areas can lead to soldering difficulties when mounting such devices on, say, a circuit board. Ea addition, the heat sinks of such devices are large and the devices are arranged so that once mounted on a circuit board, the heat sinks are located on the board. With such arrangements, however, heat is transferred to the circuit board solder junction which can result in circuit board solder failures.
The semiconductor elements of both types of devices are encapsulated in a molding compound, typically molded epoxy, by injecting epoxy at high pressure. The stress caused by such a high pressure process step reduces the reliability of a device since molding stress can result in cracked die, mold voids and mold flashes.
The latter type of devices, in which the tab is connected to the heat sink, suffer from additional problems. Since the tab must be soldered to the heat sink, these type of devices require an additional step in their manufacture which increases their manufacturing cost. Furthermore, the step of attaching the tab to the heat sink typically requires a high temperature which may damage the semiconductor element leading to device failure. A further disadvantage with using tabs is that with the second process step of soldering the tab to the heat sink, it can be difficult ensuring that the tab is the correct height and hence that the first and second contacts are coplanar.
It would therefore be desirable to provide an improved surface mount semiconductor diode device in which the above problems and disadvantages are mitigated.
SUMMARY OF THE INVENTION
In accordance with the present invention there is provided a surface mount semiconductor diode device having first and second coplanar contacts, the device comprising:
a semiconductor element having a first surface electrically mounted on a surface of a first member formed of conductive material, the first member having an arm which extends in a direction away from the surface of the first member, an end of the arm forming the first contact; and
a cup member formed of a conductive material and comprising a wall extending from a bottom portion so as to form an opening surrounded by the wall and having the bottom portion as a base,
wherein the semiconductor element and first member are mounted within the opening such that a second surface of the semiconductor element is electrically coupled to the bottom portion of the cup member and the end of the arm extends above a top surface of the wall,
wherein the cup member further comprises a leg portion integral with and extending from the top surface of the wall such that an end of the leg portion is coplanar with the end of the arm, the end of the leg portion forming the second contact.
Thus, the present invention provides a surface mount semiconductor diode device having two coplanar contacts which is simple to manufacture and which does not require additional steps to attach tabs for one of the contacts.
REFERENCES:
patent: 3209209 (1965-09-01), Mueller
patent: 4758875 (1988-07-01), Fujisaki et al.
Martin Jean-Baptiste
Wasmer William D.
Chaudhuri Olik
Semiconductor Components Industries LLC
Wille Douglas A.
LandOfFree
Surface mount semiconductor diode device does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Surface mount semiconductor diode device, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Surface mount semiconductor diode device will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2580858