Active solid-state devices (e.g. – transistors – solid-state diode – Housing or package – Insulating material
Patent
1998-06-26
2000-05-09
Saadat, Mahshid
Active solid-state devices (e.g., transistors, solid-state diode
Housing or package
Insulating material
257678, 257699, H01L 2302, H01L 2304
Patent
active
060607769
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to a rectifier diode. It is known for medium- and higher-power rectifier diodes to be embodied as press-fit diodes. The press-fit diodes have a press-fit base, which is press-fitted into a corresponding recess in a rectifier arrangement. In this process the press-fit base at the same time accomplishes durable thermal and electrical connection of the rectifier diode to the rectifier arrangement. Such arrangements are known in automotive engineering, for instance, where they are used as rectifiers in the motor vehicle generators. The press-fit base there has a fastening region to which a semiconductor chip is secured, for instance by soldering. A so-called head wire is secured in turn on the semiconductor chip, again for instance by soldering, and it is then firmly connected electrically to a phase supply line of the motor vehicle generator, for instance by soldering or welding.
When the rectifier diode is press-fitted into an intended opening of a rectifier arrangement, mechanical forces engage the edge of the rectifier diode. These mechanical forces are transmitted via the press-fit base to the fastening region of the semiconductor chip. In the press-fitting operation, the semiconductor chip mounted on the fastening region undergoes bending stress. The solder layers between the semiconductor chip and the press-fit base and between the semiconductor chip and the head wire are also affected by the bending stress.
In German Patent Disclosure DE 41 12 286 A1, the press-fit base is made of solid metal, specifically in the form of a centrally disposed pedestal on which the semiconductor chip is mounted. This already provides spatial separation of the semiconductor chip from the edge of the press-fit base that is acted upon by the press-fitting forces. Despite the separation, the chip and the solder layers surrounding it undergo bending stress, which can lead to the immediate failure or later premature aging of the press-fit diode.
In an alternative construction of a rectifier diode without a pedestal or a bulwark surrounding such a pedestal, the sturdiness and reliability of the component depends on the chip's being secured in an exactly centered manner in production.
SUMMARY OF THE INVENTION
Accordingly, it is an object of present invention to provide a rectifier diode which avoids the disadvantages of the prior art.
In keeping with these objects, one feature of the present invention resides, briefly stated, in a rectifier diode in which, in order to mechanically stabilize the base, the bottom of the base in the region of the pedestal has a bulwark surrounding the pedestal, the bulwark separated from the pedestal by a trench is integral with the bottom of the base, a pressing region for absorbing forces oriented at right angle tot he plane of the semiconductor chip is disposed on the side of the bulwark remote from the trench between the bulwark and a substantially cylindrical wall of the base disposed substantially perpendicular to the base bottom, and the trench embodied between the bulwark and the pedestal has a radial extent that is approximately twice as great as the height of the bulwark measured from the trench upwards.
When the rectifier diode is designed in accordance with the present invention it has the advantage over the prior art that sturdiness, with regard to deformation, for instance in the press-fitting operation, is achieved in a simple way. Because the base bottom, in the region of the pedestal, has a bulwark that surrounds this pedestal and is integral with the base bottom, the stiffness of the entire base can be improved by simple geometrical variations in the height of the bulwark and in its spacing from the pedestal.
Advantageous refinements of and improvements to the rectifier diode defined by the main claim are possible with the provisions recited in the dependent claims.
The disposition of a press-fit region on the side of the bulwark remote from the trench is especially advantageous. This assures sturdiness of the rectifier diode t
REFERENCES:
patent: 3823339 (1974-07-01), Borneman et al.
patent: 4532539 (1985-07-01), Frister
patent: 5760425 (1998-06-01), Kobayashi et al.
Schuler Siegfried
Spitz Richard
Clark Jhihan B
Robert & Bosch GmbH
Saadat Mahshid
Striker Michael J.
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