JP2006186035A - Semiconductor device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a semiconductor device capable of dispensing with separate provision of an external terminal and of reducing the number of components and the number of assembling processes. <P>SOLUTION: Semiconductor chips 2, 3 are accommodated in an accommodation space formed with an upper casing 4 and a lower casing 5. The upper casing 4 is formed by insert molding an electrode plate 41 with insulating resin, and a frame member 42 and the electrode plate 41 are integrated. In the same fashion, the lower casing 5 is also formed by insert molding an electrode plate 51 with insulating resin, and a frame member 52 and the electrode plate 51 are integrated. A module 1 is formed by soldering the semiconductor chips 2, 3 onto the electrode plate 51, placing contact electrodes 8 on the semiconductor chips 2, 3 respectively, covering the lower casing 5 with the upper casing 4, and joining the frame members 42, 52 using an adhesive or the like while pressurizing the electrode plates 41, 51 from upper and lower. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a pressure contact type semiconductor device.

  An insulated gate bipolar transistor (IGBT) is used as a power switching device, for example, as an inverter element of an electric vehicle. In a semiconductor device in which a semiconductor chip such as an IGBT is incorporated into a package to form a module, a pressure contact type structure has been proposed in order to improve heat dissipation and suppress internal wiring inductance (for example, patents). Reference 1).

  In the IGBT, electrodes are formed on both front and back surfaces of the chip. In the pressure contact type semiconductor device described in Patent Document 1, the semiconductor chip is sandwiched between two electrode plates and pressed to perform pressure contact with the chip electrode. ing. The semiconductor device is provided with an insulating outer cylinder made of ceramic so as to surround the semiconductor chip, and the peripheral portions of the upper and lower electrode plates are joined to the upper and lower end surfaces of the insulating outer cylinder, respectively.

JP-A-7-94673

  By the way, the sealed space surrounded by the upper and lower electrode plates and the insulating outer cylinder is filled with an inert gas, and the upper and lower electrode plates and the insulating outer cylinder are joined by welding in order to prevent the leakage of the inert gas. ing. For this reason, it is necessary to reduce the heat capacity of the portion of the upper and lower electrode plates that contacts the outer cylinder so that the upper and lower electrode plates can be welded to the insulating outer cylinder, and it is necessary to reduce the thickness of the electrode plate in that portion. It was. As a result, when the electrode plate is extended to the outside of the semiconductor device as an external terminal, the thickness of the external terminal (extended electrode plate) is reduced. It is necessary to provide a separate external terminal for leading to the device, resulting in an increase in the size and cost of the device.

  The present invention relates to a semiconductor device in which semiconductor chips each having electrodes formed on the front and back surfaces are housed in a casing composed of two divided casings forming a bottomed cylindrical body, and a peripheral wall of the bottomed cylindrical body Is formed of an insulating member, the bottom of the bottomed cylindrical body is formed of a first electrode plate, and a first external terminal formed by extending a part of the first electrode plate to the outside of the casing is provided. The divided casing and the peripheral wall of the bottomed cylindrical body are formed of an insulating member, the bottom of the bottomed cylindrical body is formed of the second electrode plate, and a part of the second electrode plate extends outside the casing And a second divided casing having a second external terminal, and pressurizing the first and second electrode plates in the direction of the semiconductor chip so as to sandwich the front and back surfaces of the semiconductor chip, Each formed electrode is electrically connected to the electrode plate facing it. .

  According to the present invention, the casing in which the semiconductor chip is accommodated is constituted by the first and second divided casings that form a bottomed cylindrical body, and the bottom surface of each bottomed cylindrical body is an electrode plate, and the electrodes Since part of the plate is extended to the outside of the casing to be an external terminal, it can be led out without reducing the thickness of the electrode plate, and it is necessary to provide a separate external terminal as in the past Therefore, the number of parts can be reduced, the apparatus can be downsized, and the number of assembly steps can be reduced.

  Hereinafter, the best mode for carrying out the present invention will be described with reference to the drawings. 1 and 2 are diagrams showing an embodiment of a semiconductor device according to the present invention. FIG. 1 is a plan view showing a schematic configuration of a semiconductor device, and FIG. 2 is a cross-sectional view taken along line AA of FIG. The semiconductor device shown in FIGS. 1 and 2 shows a module 1 for one phase of a three-phase inverter, and semiconductor chips 2 and 3 are provided in a casing of the module 1. Examples of the switching element used in the inverter include an IGBT and a MOSFET. Hereinafter, an example using an IGBT will be described. The semiconductor chip 2 is an IGBT and the semiconductor chip 3 is a diode. Reference numeral 41 denotes an electrode plate (bus bar) provided on the upper surface of the module 1. In FIG. 1, a part of the electrode plate 41 has a broken surface.

  The semiconductor chips 2 and 3 are provided with electrodes on both front and back surfaces of the chip. In the case of the semiconductor chip 2 which is an IGBT, a collector electrode is provided on the back surface side, and an emitter electrode and a gate electrode are provided on the front surface side. An electrode plate 51 is disposed on the lower surface of the module 1, and the semiconductor chips 2 and 3 are mounted on the electrode plate 51 by soldering the electrodes on the back surface side to the electrode plate 51. The member indicated by reference numeral 6 is solder. The gate electrode of the semiconductor chip 2 is connected to the control terminal 53 by a bonding wire 7. The electrode plates 41 and 51 are made of a metal material having high electrical conductivity and thermal conductivity, such as copper or aluminum, or an alloy containing them as a main component.

  Contact electrodes 8 for protecting the electrodes of the semiconductor chips 2 and 3 are placed on the upper surfaces of the semiconductor chips 2 and 3, respectively. The contact electrode 8 is a member that electrically and thermally connects the surface side electrodes of the semiconductor chips 2 and 3 and the electrode plate 41, but the thermal stress due to the linear expansion difference between the electrode plate 41 and the semiconductor chips 2 and 3 It also has a function to reduce. Also, it functions as a thermal mass that relieves the rapid temperature rise of the semiconductor chips 2 and 3.

  For example, when the electrode plate 41 is formed of a copper material, the contact electrode 8 is also formed of a copper block. On the chip-side surface of the copper block, a metal layer having a linear expansion coefficient close to Si (silicon), which is the material of the semiconductor chips 2 and 3, and made of Mo (molybdenum) or W (tungsten) is provided. Keep it. If the semiconductor chips 2 and 3 are brought into direct contact with the electrode plate 41 made of a copper material, the chip surfaces of the semiconductor chips 2 and 3 may be rubbed due to expansion or contraction due to temperature change. However, since the difference in the coefficient of linear expansion between the semiconductor chip side of the contact electrode 8 and the semiconductor chips 2 and 3 is small, the occurrence of such a problem can be prevented.

  By pressing the electrode plates 41 and 51 from above and below so that the contact electrode 8 is sandwiched between the semiconductor chips 2 and 3 and the electrode plate 41, the surface electrodes of the semiconductor chips 2 and 3 and the electrode plate 41 are electrically connected. Connected. When the solder 6 is plastically deformed at the time of pressurization, it is possible to prevent an uneven load from being applied to the semiconductor chips 2 and 3. Even if there is a slight difference in the thickness of the semiconductor chips 2 and 3, the dimensional difference can be absorbed by the plastic deformation of the solder 6. Note that the illustration of the pressurizing mechanism is omitted.

  In this embodiment, only the front surface side of the semiconductor chips 2 and 3 has a pressure contact structure, but not only the front surface side but also the back surface side may have a pressure contact structure. In that case, the contact electrodes 8 are provided on both the front and back surfaces of the semiconductor chips 2 and 3. Moreover, you may make it connect the electrode of both front and back to the electrode plates 41 and 51 by soldering. Further, although the semiconductor chips 2 and 3 are fixed to the lower electrode plate 51 using the solder 6, silver paste, conductive adhesive, or the like may be used as the conductive fixing means instead of the solder 6.

  In the present embodiment, the casing in which the semiconductor chips 2 and 3 are housed is the upper casing 4 in which the electrode plate 41 and the frame member 42 as shown in FIG. 3 are integrated, the electrode plate 51 as shown in FIG. It is comprised by the lower casing 5 with which the frame member 52 was integrated.

  3A is a plan view of the upper casing 4, FIG. 3B is a sectional view, and FIG. 3C is a bottom view. The electrode plate 41 includes a rectangular portion 41a constituting a part of the casing and a terminal portion 41b for connecting the electrode plate 41 to the outside. The frame member 42 is formed in a rectangular cylindrical shape at the peripheral edge of the rectangular portion 41 a of the electrode plate 41. The frame member 42 is formed with a hole 42a penetrating vertically and a hole 42b penetrating inside and outside the casing. The electrode plate 41 is provided such that the peripheral edge of the rectangular portion 41 a is placed on the stepped portion 42 c of the frame member 42, and is exposed on the upper surface side of the upper casing 4.

  In the present embodiment, the frame member 42 is made of an insulating resin, and the upper casing 4 is integrally formed by insert molding of the frame portion 42 and the electrode plate 41. In addition, after the frame member 42 is molded, the integral upper casing 4 may be formed by bonding the rectangular portion 41a of the electrode plate 41 to the stepped portion 42c.

  On the other hand, FIG. 4 is a figure which shows the lower casing 5, (a) is a top view of the lower casing 5, (b) is sectional drawing, (c) is a bottom view. Similarly to the electrode plate 41, the electrode plate 51 also has a rectangular portion 51a constituting a part of the casing and a terminal portion 51b for connecting the electrode plate 51 to the outside. An L-shaped control terminal 53 is provided on the upper surface side of the frame portion 52 provided at the peripheral edge of the rectangular portion 51 a of the electrode plate 51. The bonding portion 53a of the control terminal 53 is provided in contact with the frame member 52, and the bonding wire 7 is connected to the bonding portion 53a as shown in FIG. The electrode plate 51 is provided such that the peripheral edge of the rectangular portion 51 a is in contact with the stepped portion 52 a of the frame member 52, and is exposed on the lower surface side of the lower casing 5.

  The frame member 52 is also made of the same insulating resin as the frame member 42. The lower casing 5 is also formed by insert molding similarly to the upper casing 4, and the frame portion 52, the electrode plate 51 and the control electrode 53 are integrally molded. Also in the case of the lower casing 5, after the frame member 52 is molded, the rectangular portion 51 a of the electrode plate 51 is bonded to the stepped portion 52 c, and the control electrode 53 is bonded and fixed to the upper surface of the frame member 52. You may make it do.

  The module 1 is assembled in the following procedure. First, the semiconductor chips 2 and 3 are soldered on the electrode plate 51 of the lower casing 5, and the gate electrode provided on the upper surface of the semiconductor chip 2 and the control terminal 53 provided on the frame member 52 are connected by the bonding wire 7. Connecting. Thereafter, the contact electrode 8 is placed on the upper surfaces of the semiconductor chips 2 and 3, and the upper casing 4 is attached to the lower casing 5 and joined. At this time, the upper casing 4 is mounted so that the control electrode 53 is inserted into the hole 42 a of the frame member 42. The casings 4 and 5 are joined to each other by bonding or screwing the frame members 42 and 52 together.

  Next, an insulating resin having high adhesion and elasticity, such as silicon gel, is filled into the casing from the through hole 42 b formed in the frame member 42. After filling, the through hole 42b is sealed. The insulating resin is not limited to silicon, but may be epoxy or urethane. When air is present in the casing, the electrode and the like are oxidized. By filling the resin in this way, the electrode surface is covered with the resin, and oxidation can be prevented. Further, the upper and lower surfaces of the semiconductor chip 2 are different electrodes and have a large potential difference, which may cause creeping discharge. However, creeping discharge can be prevented by filling the resin and covering the space between the electrodes. In addition, you may make it fill the inside of a casing with an inert gas by joining an upper and lower casing in inert gas atmosphere, without forming the through-hole 42b.

[Modification 1]
5-7 is a figure which shows the modification 1 of embodiment mentioned above. 5 and 6 are views showing the upper casing 4 and the lower casing 5, respectively. As shown in FIGS. 5B and 5C, convex portions 42 d and 42 e are formed on the mating surface of the upper casing 4 with the lower casing 5 of the frame member 42. Furthermore, a positioning portion 42 f for positioning the contact electrode 8 placed on the semiconductor chips 2 and 3 is formed on the lower surface of the electrode plate 41. In the positioning portion 42f, rectangular holes H1 and H2 into which the contact electrodes 8 are fitted are formed at positions facing the semiconductor chips 2 and 3.

  On the other hand, as shown in FIGS. 6A and 6B, the lower casing 5 has convex portions at positions facing the convex portions 42 d and 42 e of the mating surface of the frame member 52 with the upper casing 4. Concave portions 52b and 52c that are mated with 42d and 42e are formed. When the upper casing 4 is attached to the lower casing 5 as shown by a two-dot chain line in FIG. 7, convex portions 42 d and 42 e formed on the frame member 42 are formed on the frame member 52 of the lower casing 5. It engages with the recesses 52b and 52c, respectively.

  In other words, the positioning between the casings 4 and 5 is achieved by the convex portions 42d and 42e engaging with the concave portions 52b and 52c. Further, the contact electrodes 8 are positioned with respect to the semiconductor chips 2 and 3 by being fitted into the rectangular holes H1 and H2 so that the upper side of each contact electrode 8 is guided by the positioning portion 42f of the upper casing 4. A positioning portion for positioning the solder 6 and the semiconductor chips 2 and 3 may also be formed on the lower electrode plate 1.

[Modification 2]
FIGS. 8A and 8B are diagrams showing Modification Example 2. FIG. 8A is a plan view of the module 1, FIG. 8B is a cross-sectional view, and FIG. 8C is a bottom view. In the casings 4 and 5, the same parts as those in the above-described embodiment are given the same reference numerals, and different parts will be mainly described below. As shown in FIG. 2, the module 1 is pressurized from above and below by a pressure mechanism in order to cause the electrode plate 41 and the semiconductor chips 2 and 3 to be pressed. However, since the internal contact electrode 8 is fixed in the casing, the contact electrode 8 must be pressed against the semiconductor chips 2 and 3 by the electrode plate 41 even in the case of the module 1 alone before pressurization. There is.

  For example, it is set so that a minute gap is formed between the frame members 42 and 52 when the casings 4 and 5 are combined, and the electrode plates 41 and 51 are set so that the gap is zero when the frame members are joined. Is configured to be slightly deformed. In such a case, a reaction force that is pushed out of the casing acts on the electrode plates 41 and 51, and the electrode plates 41 and 51 may be detached from the frame members 42 and 52.

  Therefore, in the second modification, the detachment preventing portions 42g and 52g that prevent the electrode plates 41 and 51 from detaching from the frame members 42 and 52 are formed in the frame members 42 and 52, respectively. In the example shown in FIG. 8, the frame members 42 and 52 are run on the entire circumference of the rectangular portions 41 a and 51 a of the electrode plates 41 and 51 (in other words, the front and back surfaces of the electrode plates 41 and 51 are covered with the frame members 42 and 52). The separation preventing portions 42g and 52g are formed in such a manner as described above. By forming such separation preventing portions 42g and 52g, it is possible to prevent the electrode plates 41 and 51 from being detached outside due to a reaction force.

[Modification 3]
FIG. 9 is a diagram for explaining a third modification. Since the electrode plates 41 and 51 provided in the module 1 are dissimilar electrodes, the withstand voltage between the electrode plates 41 and 51 is set to be higher than the withstand voltage of the semiconductor chips 2 and 3 in order to prevent creeping discharge. There is a need. In the module 1, since the resin is filled in the casing, creeping discharge in the module is prevented, but the outside of the module 1 is exposed to the atmosphere, so that it is necessary to ensure creeping insulation.

  Therefore, in the module 1 shown in FIG. 9, irregularities are formed on the outer peripheral surfaces 42 k and 52 k of the frame members 42 and 52. Specifically, a plurality of grooves that circulate around the side surfaces of the frame members 42 and 52 were formed. Thereby, the creeping distance between the electrode plate 41 and the electrode plate 51 is increased, and the creeping insulation can be improved, and the creeping discharge can be prevented.

  In the embodiment described above, the control terminal 53 is molded on the frame member 52, and the control terminal 53 and the gate electrode of the semiconductor chip 2 are connected by the bonding wire 7. However, as shown in FIG. The pin 100 may be in pressure contact with the gate electrode of the semiconductor chip 2. An insulating resin insert 101 is provided so as to penetrate the electrode plate 41, and the pin 100 is brought into contact with the gate electrode through a through hole formed in the insert 101. Although not shown, the pin 100 is pressed against the gate electrode by a biasing means such as a spring.

The characteristics of the present embodiment described above are summarized as follows.
(A) The upper casing 4 in which the electrode plate 41 and the frame member 42 are integrated, and the lower casing 5 in which the electrode plate 51 and the frame member 52 are integrated are separately formed, and they are joined together. Since the sealed casing is configured, it is not necessary to weld the electrode plate and the insulating outer cylinder for the conventional sealing. Since part of the electrode plates 41 and 51 are extended to the sides of the frame members 42 and 52 as terminal portions 41b and 51b, they are led out to the outside without reducing the thickness of the terminal portions 41b and 51b. Therefore, it is not necessary to provide a separate external terminal, and the module 1 can be downsized and the number of parts can be reduced. In particular, the electrode plate 41 and the frame member 42, and the electrode plate 51 and the frame member 52 are integrally formed to form the casings 4 and 5, so that the assembly process can be simplified, and the electrode plates 41 and 51 and the frame member 42, The reliability of joining with 52 can be improved.

(B) By providing the frame members 42 and 52 with the separation preventing portions 42g and 52g formed so as to ride on the electrode plates 41 and 51 (covering the front and back surfaces of the electrode plates 41 and 51), the electrode plates 41 and 52 are provided. It is possible to prevent them from being detached from the frame members 42 and 52 when they are pressed. In addition, by forming the outer peripheral surfaces 42k and 52k of the frame members 42 and 52 into a concavo-convex shape, the creeping distance between the electrode plates 41 and 51 becomes longer, and the occurrence of creeping discharge can be suppressed. Further, since the convex portions 42d and 42e and the concave portions 52b and 52c that are engaged with each other are formed on the surfaces of the frame members 42 and 52 that are joined to each other, the positioning when the casings 4 and 5 are overlapped is facilitated.

(C) Even in the pressure contact structure, the semiconductor chip 2 is fixed to the lower electrode plate 51 by means of conductive fixing means such as solder 6, conductive adhesive, or silver paste, so that it is provided on the frame member 52. The semiconductor chip 2 is fixed to the control terminal 53, and wire bonding work can be simplified. Further, when the solder 6 is used as the conductive fixing means, the unbalanced load applied to the semiconductor chips 2 and 3 can be alleviated by the plastic deformation of the solder 6 during the pressure contact.

(D) Since the contact electrode 8 as a thermal stress buffer material is provided between the semiconductor chips 2 and 3 and the electrode plates 41 and 51, the line between the contact electrode 8 and the semiconductor chips 2 and 3 in the mutual contact portion. The expansion coefficient difference is small, and it is possible to prevent the chip surfaces of the semiconductor chips 2 and 3 from being rubbed due to expansion and contraction due to temperature changes. Since the positioning portion 42f is formed in the upper casing 4, each contact electrode 8 is guided by the positioning portion 42f when the upper and lower casings 4 and 5 are put together, and is accurately positioned on the semiconductor chips 2 and 3. The
(E) Since the insulating resin is filled in the casing formed by the upper and lower casings 4 and 5, oxidation of the electrode surfaces of the semiconductor chips 2 and 3 and creeping discharge between the electrodes can be prevented. .

  In the correspondence between the embodiment described above and the elements of the claims, the frame members 42 and 52 are peripheral walls, the electrode plate 41 is a first electrode plate, the electrode plate 51 is a second electrode plate, and the upper side. The casing 4 is a first divided casing, the lower casing 5 is a second divided casing, the terminal portion 41b is a first external terminal, the terminal portion 51b is a second external terminal, and convex portions 42d and 42e and The recesses 52b and 52c constitute engaging portions, the solder 6 constitutes a conductive fixing means, and the contact electrode 8 constitutes a protective member. The above description is merely an example, and when interpreting the invention, there is no limitation or restriction on the correspondence between the items described in the above embodiment and the items described in the claims.

1 is a diagram illustrating an embodiment of a semiconductor device according to the present invention, and is a plan view illustrating a schematic configuration of the semiconductor device. It is AA sectional drawing of FIG. It is a figure which shows the upper casing 4, (a) is a top view, (b) is sectional drawing, (c) is a bottom view. It is a figure which shows the lower casing 5, (a) is a top view, (b) is sectional drawing, (c) is a bottom view. It is a figure which shows the upper casing 4 in the modification 1, (a) is a top view, (b) is sectional drawing, (c) is a bottom view. It is a figure which shows the lower casing 5 in the modification 1, (a) is a top view, (b) is sectional drawing, (c) is a bottom view. It is a figure explaining positioning of the contact electrode 8 by the positioning part 42f. It is a figure which shows the module 1 in the modification 2, (a) is a top view, (b) is sectional drawing, (c) is a bottom view. It is a figure explaining the modification 3. FIG. FIG. 3 is a diagram showing a needle-like pin 100 that is in pressure contact with a gate electrode of a semiconductor chip 2.

Explanation of symbols

1 Module 2, 3 Semiconductor chip 4 Upper casing 5 Lower casing 6 Solder 8 Contact electrode 41, 51 Electrode plate 41a, 51a Rectangular portion 41b, 51b Terminal portion 42, 52 Frame member 42d, 42e Protruding portion 42f Positioning portion 42g, 52g Detachment prevention part 42k, 52k Outer peripheral surface 52b, 52c Recess 53 Control terminal H1, H2 Rectangular hole

Claims (9)

A semiconductor device in which semiconductor chips each having electrodes formed on the front and back surfaces are housed in a casing composed of two divided casings forming a bottomed cylindrical body,
A peripheral wall of the bottomed cylindrical body is formed of an insulating member, a bottom portion of the bottomed cylindrical body is formed of a first electrode plate, and a part of the first electrode plate is extended outside the casing. A first split casing having a first external terminal comprising:
A peripheral wall of the bottomed cylindrical body is formed of an insulating member, a bottom portion of the bottomed cylindrical body is formed of a second electrode plate, and a part of the second electrode plate extends outside the casing. A second split casing having a second external terminal comprising:
The first and second electrode plates are pressed in the direction of the semiconductor chip so as to sandwich the front and back surfaces of the semiconductor chip, and the electrodes formed on the front and back surfaces and the electrode plates facing the electrodes are electrically connected to each other. A semiconductor device characterized by being connected to a semiconductor device. The semiconductor device according to claim 1,
An insulating resin is used as the insulating member, and the insulating member and the electrode plate of the first and second divided casings are formed by integral molding. The semiconductor device according to claim 1 or 2,
2. A semiconductor device according to claim 1, wherein a separation preventing portion is provided on the peripheral wall so as to cover the front and back surfaces of the electrode plate and prevent the electrode plate from separating from the peripheral wall due to the pressurization. The semiconductor device according to claim 1,
A semiconductor device characterized in that an outer peripheral surface of the peripheral wall has an uneven shape. In the semiconductor device according to claim 1,
The casing is formed by abutting and joining the peripheral walls of the first and second divided casings, and an engagement portion that engages with each other is formed at the joint portion of each peripheral wall. apparatus. In the semiconductor device according to claim 1,
A semiconductor device, wherein at least one of the electrodes formed on the front and back surfaces of the semiconductor chip is fixed to the electrode plate opposed thereto by a conductive fixing means. The semiconductor device according to claim 6.
A semiconductor device characterized in that solder is used for the conductive fixing means. In the semiconductor device according to claim 1,
A material that is disposed between at least one of the first and second electrode plates and the semiconductor chip, and has a coefficient of linear expansion of a contact surface with the semiconductor chip contact portion that is closer to the semiconductor chip than the electrode plate. A protective member formed and protecting the contact surface of the semiconductor chip;
A positioning portion extending from the peripheral wall toward the inside of the semiconductor device and positioning the protective member on the chip surface of the semiconductor chip is provided in at least one of the first divided casing and the second divided casing. A semiconductor device. The semiconductor device according to claim 1,
A semiconductor device characterized in that an insulating resin is filled in a semiconductor chip housing space of the casing formed by the first and second divided casings.

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