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Patent Issued for Power Semiconductor Device

February 19, 2014



By a News Reporter-Staff News Editor at Electronics Newsweekly -- A patent by the inventors Nakazato, Shigeyuki (Chiyoda-ku, JP); Goto, Yoichi (Chiyoda-ku, JP); Kitai, Kiyofumi (Chiyoda-ku, JP); Kimura, Toru (Chiyoda-ku, JP), filed on July 31, 2012, was published online on February 4, 2014, according to news reporting originating from Alexandria, Virginia, by VerticalNews correspondents.

Patent number 8643171 is assigned to Mitsubishi Electric Corporation (Tokyo, JP).

The following quote was obtained by the news editors from the background information supplied by the inventors: "Conventionally, when a heat sink is attached for cooling electronic components (power semiconductor elements) that generate a large amount of heat such as a CPU (central processing unit) and a power transistor, application of thermal grease is widely performed to fill a minute gap between a contact surface of the electronic components and that of the heat sink to improve heat dissipation performance.

"The thermal conductivity of the thermal grease is quite lower than those of metals. Accordingly, a radiation-fin-integrated power semiconductor device having radiation fins integrated with a base plate of a metallic part of the power semiconductor device without using the thermal grease is also realized to further improve the heat dissipation performance. In the radiation-fin-integrated power semiconductor device, grooves for joining the radiation fins are provided in the base plate, resin molding is performed in a state of exposing a part of the surface of the base plate including a portion in which these grooves are formed, and the radiation fins are inserted into the grooves of the base plate and then swaged to be fixedly attached to the grooves, thereby integrating the base plate with the radiation fins to improve the heat dissipation performance.

"In relation to the power semiconductor device adapted to improve the heat dissipation performance, it is known that radiation noise from power semiconductor elements and malfunction is suppressed by inserting a metal plate between the radiation fins and the base plate and by causing this metal plate to function to connect the power semiconductor device to an earth potential (see Patent Literature 1)."

In addition to the background information obtained for this patent, VerticalNews journalists also obtained the inventors' summary information for this patent: "Technical Problem

"In the conventional technique, heating and cooling is carried out at a time of sealing the power semiconductor elements with resin. This often causes a module of the power semiconductor device to be completed in a warped state or causes the metal plate to be inserted itself to be warped. Therefore, the conventional technique has a problem that a gap is generated between the metal plate and the base plate, which increases the electrical resistance between the metal plate and the base plate. Furthermore, an oxide film is formed in the atmosphere on the surface of the base plate that is a metal, and the oxide film on the metal is higher than the metal itself in the electrical resistance. With the conventional technique, an electrical contact between the metal plate and the base plate is realized by placing the metal plate between the radiation fins and the base plate. Accordingly, the metal plate and the base plate are electrically connected to each other via the oxide film formed on the surface of the base plate except for minute regions where the oxide film on the surface of the base plate is damaged as a result of the contact of the metal plate with the base plate and where the metal is exposed. For this reason, even if neither the metal plate nor the base plate is warped and the base plate comes in surface contact with the metal plate, a ratio of portions that are made conductive as a result of the contact of the metals is low, disadvantageously resulting in a high electrical resistance between the base plate and the metal plate.

"The present invention has been achieved to solve the above problems, and an object of the present invention is to provide a power semiconductor device having an enhanced effect of suppressing radiation noise from a power semiconductor element and malfunction.

"Solution to Problem

"There is provided a power semiconductor device comprising: a mold unit that includes a power semiconductor element, a base plate, and a mold resin, the power semiconductor element being mounted on one surface of the base plate, a convex portion being formed on an other surface of the base plate, the convex portion including a plurality of grooves, the power semiconductor element being sealed with the mold resin in such a manner as to expose the convex portion; a plurality of radiation fins inserted into the grooves, respectively, and fixedly attached to the base plate by swaging; and a metal plate that includes a cut-off portion into which the convex portion is inserted, the metal plate being arranged between the mold unit and the radiation fins with the convex portion inserted into the cut-off portion, wherein the metal plate includes a protrusion that protrudes from an edge of the cut-off portion and that digs into a side surface of the convex portion when the convex portion is inserted into the cut-off portion.

"Advantageous Effects of Invention

"The power semiconductor device according to the present invention can reduce the electrical resistance between a base plate and a metal plate and enhance the effect of suppressing radiation noise from power semiconductor elements and malfunction."

URL and more information on this patent, see: Nakazato, Shigeyuki; Goto, Yoichi; Kitai, Kiyofumi; Kimura, Toru. Power Semiconductor Device. U.S. Patent Number 8643171, filed July 31, 2012, and published online on February 4, 2014. Patent URL: http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO2&Sect2=HITOFF&p=69&u=%2Fnetahtml%2FPTO%2Fsearch-bool.html&r=3438&f=G&l=50&co1=AND&d=PTXT&s1=20140204.PD.&OS=ISD/20140204&RS=ISD/20140204

Keywords for this news article include: Semiconductor, Electronic Components, Mitsubishi Electric Corporation.

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Source: Electronics Newsweekly


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