Power semiconductor device suitable for automation of production

Abstract: The feature of the construction of this invention lies in a direct bond copper (DBC) plate. That is, a first Cu plate (11) on which a semiconductor pellet (15) is formed is fixed on the ceramic plate (12) to continuously extend from the front surface of the ceramic plate (12) to the rear surface thereof via one side surface thereof. Second Cu plates (13) serving as electrodes of the semiconductor pellet (15) are fixed on both sides of the first Cu plate (11) on the surface of the ceramic plate (12) on which the semiconductor pellet (15) is disposed. Electrode pads (17) formed on the semiconductor pellet (15) fixed on the first Cu plate (11) are electrically connected to the second Cu plates by means of bonding wires (18). Since the first Cu plate (11) is continuously formed on the rear surface of the ceramic plate (12) which is opposite to the surface on which the semiconductor pellet (15) is mounted, the fixation surface of the semiconductor pellet is electrically connected to a heat sink plate (19).

Description: This invention relates to a power semiconductor device suitable for automation of production, comprising: a ceramic-series insulative plate; a first conductive plate fixed on said ceramic-series insulative plate; second conductive plates fixed on both sides of said first conductive plate on the surface of said ceramic-series insulative plate; a semiconductor pellet fixed on said first conductive plate; wiring means for connecting electrode pads formed on said semiconductor pellet to said second conductive plates; and a heat sink plate. A power semiconductor device of this kind is known from EP-A-0 144 866. In a power semiconductor module, the technique utilizing the direct bonding of copper to ceramic is disclosed in, for example, IEEE TRANSACTIONS ON ELECTRON DEVICES, VOL. ED-23, No. 8, August 1976, p 964, "A New Hybrid Power Technique Utilizing a Direct Copper to Ceramic Bond". In the power semiconductor module utilizing the above technique, a built-in device is fixed on a plate called a direct bond copper (DBC) plate and constituted by directly attaching copper (Cu) to a ceramic plate. A heat sink is fixed on the rear surace of the DBC plate which is the opposite surface of the fixing surface of the device. With this construction, the number of manufacturing steps and the number of parts used can be reduced. Fig. 1 is a perspective view of a convention DBC plate fixed on a heat sink. A heat sink 1 may be formed of a Cu plate plated with nickel or aluminium plate, for example. A DBC plate 2 is fixed on the heat sink 1. The DBC plate 2 has a Cu plate 4 which is fixed on the surface of a ceramic plate 3 and on which a semiconductor pellet (not shown) is mounted and Cu plates 5 used as electrodes of the semiconductor pellet and fixed on the surface of the ceramic plate. The ceramic plate 3 and the Cu plates 4 and 5 are fixed together in a high-temperature oxidation atmosphere, for example. Although not shown in Fig. 1, a Cu plate is also fixed on the rear surface of the ceramic plate 3. The DBC plate 2 is fixed on the heat sink 1 by soldering, for example. The ceramic plate 4 which is insulative is disposed between the Cu plate 4 and the heat sink 1. In a case where a product requiring that the Cu plate 4 on which the semiconductor pellet is disposed and the heat sink 1 are electrically connected is manufactured, a terminal metal member 6 is formed. The terminal metal member 6 is bonded at one end to the Cu plate 4 and bonded at the other end to the heat sink 1. With this connection, the Cu plate 4 on which the semiconductor pellet is disposed is electrically connected tot he heat sink 1. However, mounting of the terminal metal member 6 makes it difficult to attain automation of the mass-production line. First, it is difficult to use the mass-production line together with a mass-production line in which mounting of the terminal metal member 6 is not ncessary. Secondly, enhancement of the mass-productivity is prevented by the adhesive quality and the precision of the mounting position of the terminal metal member 6. From EP-A-0 181 975 a semiconductor device is known, comprising a transistor chip directly secured onto a metal plate. Accordingly, an object of this invention is to provide a power semiconductor device capable of reducing the number of parts used and the number of manufacturing steps and attaining automation of an assembling line. According to the present invention this object is solved in that said first conductive plate (11) continuously extends from the front surface of said ceramic-series insulative plate (12) to the rear surface thereof via one side surface thereof; and said heat sink plate is fixed on that portion of said first conductive plate which is formed on the rear surface of said ceramic-series insulative plate which is opposite to the surface thereon on which said semiconductor pellet is fixed. In this invention, since the conductive plate on which the semiconductor pellet is mounted is fixed on the ceramic-series insulative plate to continuously extend from the front surface of the ceramic-series insulative plate to the rear surface thereof via one side surface thereof, the number of manufacturing steps can be significantly reduced. Further, since the heat sink to be fixed in the later manufacturing step is electrically connected to the semiconductor pellet without using an additional part, mass-production can be easiliy and efficiently attained. This invention can be more fully understood from the following detailed description when taken in conjunction with the accompanying drawings, in which: Fig. 1 is a perspective view showing the construction of a conventional DBC plate; Figs. 2A and 2B are perspective views showing the construction of a DBC plate according to one embodiment of this invention; Fig. 2C is a cross sectional view taken along the line 2C-2C' of Fig. 2A, Fig. 3 is a side view showing the construction of a power semiconductor device manufactured by use of the DBC plate shown in Fig. 2A to 2C; and Fig. 4 is a top plan view of the power semiconductor device of Fig. 3. There will now be described an embodiment of this invention with reference to the accompanying drawings. Figs. 2A and 2B are perspective views showing the construction of a DBC plate according to one embodiment of this invention. Fig. 2A shows the surface (front surface) of the plate on which a semiconductor pellet is disposed and Fig. 2B shows the surface (rear surface) of the plate on which a heat sink is fixed. Fig. 2C is a cross sectional view taken along the line 2C-2C' of Fig. 2A. A Cu plate 11 on which a semiconductor pellet (not shown) is disposed is fixed on a ceramic plate 12 to continuously extend from the front surface of the plate 12 to the rear surface thereof via one side surface thereof. Cu plates 13 serving as electrodes of a semiconductor pellet (not shown) are disposed on both sides of the Cu plate 11 on the surface of the ceramic plate 12 on which the semiconductor pellet is disposed. For example, the ceramic plate 12, Cu plates 11 and 13 are fixed together in a high-temperature oxidation atmosphere. Thus, a DBC plate 14 is formed. With the construction of the above embodiment, the Cu plate 11 is formed in a "letter-U" shape as shown in Fig. 2C, and the ceramic plate 12 is inserted into the groove defined by the "U"-shaped plate. Thus, the DBC plate 14 can be made simple in construction, can be easily fixed, and has a high degree of heat conduction from the front to the rear surface. Fig. 3 is a side view showing the construction of a power semiconductor module manufactured by use of the DBC plate 14 of the above construction. In this case, Fig. 3 shows the construction from which an external casing and external leads are omitted. A semiconductor pellet 15 is mounted on the Cu plate 11 by use of solder 16 or the like. The Cu plates 13 (electrodes) and electrode pads 17 on the semiconductor pellet 15 are electrically connected together via bonding wires 18 formed of aluminum. The DBC plate 14 on which the semiconductor pellet 15 is mounted is fixed on a heat sink 19. In this case, since the Cu plate 11 is formed to continuously extend from the front surface of the insulative ceramic plate 12 to the rear surface thereof, the heat sink 19 and the DBC plate 14 can be electrically connected to each other by normal bonding using the solder 16 or the like. In a case where the semiconductor pellet 15 is a bipolar transistor, the heat sink 19 and the Cu plate 11 connected to the collector of the transistor are electrically connected to each other. Therefore, the terminal metal member 6 becomes unnecessary. According to the above embodiment, it is possible to provide an assembling line in which the number of assembling steps is reduced and which can be used together with a mass-production line in which mounting of the terminal metal member 6 is not necessary. As a result, the manufacturing cost can be reduced. As described above, according to this invention, it is possible to provide a power semiconductor device in which the number of parts used can be reduced, the number of manufacturing steps can be reduced and automation of the assembling line can be easily attained by forming the Cu plate on which the semiconductor pellet is mounted to continuously extend from the front surface to the rear surface of the DBC plate.

Claims: A power semiconductor device suitable for automation of production, comprising: a ceramic-series insulative plate (12); a first conductive plate (11) fixed on said ceramic-series insulative plate (12); second conductive plates (13) fixed on both sides of said first conductive plate (11) on the surface of said ceramic-series insulative plate (12); a semiconductor pellet (15) fixed on said first conductive plate (11); wiring means for connecting electrode pads (17)formed on said semiconductor pellet (15) to said second conductive plates (13); and a heat sink plate (19); characterized in that said first conductive plate (11) continuously extends from the front surface of said ceramic-series insulative plate (12) to the rear surface thereof via one side surface thereof; and said heat sink plate (1) is fixed on that portion of said first conductive plate (11) which is formed on the rear surface of said ceramic-series insulative plate (12) which is opposite to the surface thereon on which said semiconductor pellet (15) is fixed. A power semiconductor device according to claim 1, characterized in that said first conductive plate (11) and second conductive plate (13) are conductive plates containing copper as a main component. A power semiconductor device according to claim 1, characterized in that said first conductive plate (11) is electrically connected to said heat sink plate (19). A power semiconductor device according to claim 1, characterized in that said semiconductor pellet (15) is a bipolar transistor and the surface thereof fixed on said first conductive plate (11) is a collector.

Inventors: NAKAO JUNICHI, NAKAO, JUNICHI, Nakao, Junichi, c/o Intellectual Property Division
Applicants: TOSHIBA KK, KABUSHIKI KAISHA TOSHIBA
Application year: 1991
Main classification: H01L23
IPC codes: H01L23