JP2012209469A - Power semiconductor device - Google Patents

Abstract

An object of the present invention is to obtain a highly reliable power semiconductor device that maintains a withstand voltage even when an operating temperature range becomes high.
A lead frame in which power semiconductor elements are mounted on one surface of a circuit portion and a surface opposite to a heat radiating surface with respect to the other surface of the circuit portion are insulating films. 7, at least heat radiation of the heat sink 8, the heat sink 8, the recess 8 d formed in the gap 5 Cs opposite to the gap 5 Cs of the circuit portion 5 C, and formed in the gap 5 Cs. A sealing body 11 for sealing the power semiconductor device 1 except for the surface 8r, and a through hole 7h corresponding to the position of the recess 8d of the heat radiating plate 8 is formed in the insulating film 7. The body 11 bites into the inside of the recess 8d of the heat sink 8 through the gap 5Cs between the plate-like wiring members and the through-hole 7h of the insulating film 7 from the side of the circuit surface 5C where the semiconductor elements 2 and 3 are mounted. It comprised so that it might have.
[Selection] Figure 2

Description

  The present invention relates to a power semiconductor device, and more particularly to a power semiconductor device in which a heat sink is bonded to a lead frame on which a semiconductor element is mounted via an insulating film and integrated with a sealing resin.

Among semiconductor devices, power semiconductor devices are used to control and rectify relatively large power in vehicles such as railway vehicles, hybrid cars, and electric vehicles, home appliances, and industrial machines. Therefore, a semiconductor element used for a power semiconductor device is required to be energized at a high current density exceeding 100 A / cm ² . Therefore, in recent years, silicon carbide (SiC), which is a wide band gap semiconductor material, has attracted attention as a semiconductor material that replaces silicon (Si), and a semiconductor element made of SiC can operate at a current density exceeding 500 A / cm ^2. It is. Further, SiC is capable of stable operation even at a high temperature of 150 ° C. to 300 ° C., and is expected as a semiconductor material capable of achieving both high current density operation and high temperature operation.

  As a configuration of such a semiconductor device, a heat radiating plate is joined to a surface of the lead frame opposite to the surface on which the semiconductor element is mounted via an insulating film so as to efficiently dissipate heat generated by the semiconductor element. At the same time, the circuit member is held by sealing the whole with the resin except for the heat radiating surface (see, for example, Patent Document 1). However, since the temperature of the semiconductor device changes with the start and stop, thermal stress is generated between members having different linear expansion coefficients, and the adhesion between the sealing resin and the heat radiating plate may be lowered. When the adhesiveness is lowered and the insulating film is peeled off from the heat sink or the lead frame, the potential gradient is concentrated on the boundary between the peeled portion and the non-peeled portion, partial discharge is generated, and the withstand voltage is lowered. In particular, the wide band gap semiconductor as described above requires an insulating film with high heat dissipation to adapt to high current density and high temperature operation. In order to enhance the heat dissipation of the insulating film, the filler is generally highly filled. However, since the adhesive strength is lowered due to the relative reduction of the binder ratio responsible for adhesion, the influence becomes significant.

  On the other hand, when joining a semiconductor element with solder to a metal plate, it is a configuration for preventing the solder from spreading, but by providing irregularities in a portion other than the region where the semiconductor element is mounted in the metal plate, There has been proposed a semiconductor device that also requires ensuring the adhesion between a sealing resin and a metal plate (see, for example, Patent Document 2).

JP 2004-172239 A (paragraphs 0013 to 0018, FIGS. 1 to 4) JP 2004-186622 A (paragraphs 0011 to 0013, FIGS. 1 and 2)

  In view of this, for example, the metal plate structure described in Patent Document 2 may be incorporated in the heat dissipation plate of the semiconductor device of Patent Document 1. However, the semiconductor device of Patent Document 2 does not have an idea of insulating the metal plate and the lead frame. Therefore, simply taking in the concavo-convex structure as described above to ensure the adhesion between the sealing body and the heat sink, a portion where the thickness of the insulating layer changes between the lead frame and the heat sink, As with the case where the insulating film is peeled off, the withstand voltage is lowered.

  The present invention has been made in order to solve the above-described problems, and an object of the present invention is to obtain a highly reliable power semiconductor device that maintains a withstand voltage even when an operating temperature range becomes high.

  The power semiconductor device of the present invention has a power semiconductor element, a circuit portion formed by arranging a plurality of plate-like wiring members and formed flat, and a connection terminal to an external circuit. A lead frame mounted on one surface of the circuit part and a surface opposite to the heat radiating surface are joined to the other surface of the circuit part via an insulating film, and the plate-like wiring of the circuit part The power semiconductor device is sealed except for a heat sink in which a recess is formed facing the gap between the materials and opened in the gap, and at least the heat radiating surface of the lead frame connection terminal and the heat sink. A through hole corresponding to the position of the depression of the heat sink is formed in the insulating film, and the sealing body is formed from the surface side of the circuit surface on which the semiconductor element is mounted. Front through the gap between the plate-like wiring members and the through hole of the insulating film It characterized by having a bite portion biting into the inside of the recess of the radiating plate.

  According to the power semiconductor device of the present invention, a part of the sealing body bites into the recess of the heat sink and acts as an anchor, so that the insulating film adheres to the lead frame and the heat sink even when the operating temperature range is high. Thus, a highly reliable power semiconductor device can be obtained while maintaining the withstand voltage.

It is an external view for demonstrating the structure of the power semiconductor device concerning Embodiment 1 of this invention. It is sectional drawing for demonstrating the structure of the semiconductor device for electric power concerning Embodiment 1 of this invention. It is a top view which shows the heat sink and circuit part for demonstrating the structure of the power semiconductor device concerning Embodiment 1 of this invention. It is the top view and sectional drawing which show the heat sink and insulating film part for demonstrating the structure of the power semiconductor device concerning Embodiment 1 of this invention. It is sectional drawing which shows the hollow part vicinity part of the heat sink for demonstrating the structure of the power semiconductor device concerning Embodiment 1 of this invention. It is a top view which shows the heat sink and circuit part for demonstrating the structure of the power semiconductor device concerning Embodiment 2 of this invention. It is sectional drawing which shows the hollow part vicinity part of the heat sink for demonstrating the structure of the power semiconductor device concerning Embodiment 2 of this invention, and the state in a manufacturing process. It is sectional drawing which shows the hollow part vicinity part of the heat sink for demonstrating the effect by the structure of the power semiconductor device concerning Embodiment 2 of this invention. It is sectional drawing which shows the hollow part vicinity part of the heat sink for demonstrating the structure of the power semiconductor device concerning Embodiment 3 of this invention. It is sectional drawing which shows the hollow part vicinity part of the heat sink for demonstrating the structure of the power semiconductor device concerning Embodiment 4 of this invention. It is the top view and sectional drawing which show the heat sink and insulating film part for demonstrating the structure of the power semiconductor device concerning Embodiment 5 of this invention.

Embodiment 1 FIG.
1 to 5 are diagrams for explaining a power semiconductor device according to a first embodiment of the present invention. FIG. 1 shows an appearance of the power semiconductor device, and FIG. 1B is a side view from the b direction in FIG. 1A among the side surfaces in the longitudinal direction, and FIG. 1C is the c direction in FIG. 1A among the side surfaces in the longitudinal direction. FIG. 1D is a side view from the d direction of FIG. 1A among the side surfaces in the short side direction. 2 is a cross-sectional view of the cross-sectional view seen from the direction d in FIG. 1 (a). FIG. 2 (a) is a cross-sectional view taken along the line AA, and FIG. 2 (b) is a cross-sectional view taken along the line BB. FIG. FIG. 3 is a plan view of a power semiconductor device in which a heat sink and a power lead frame are extracted. 4 is a view in which the power lead frame portion is further excluded from FIG. 3, FIG. 4 (a) is a plan view seen from the insulating film side of the heat sink, and FIG. 4 (b) is FIG. 4 (a). It is sectional drawing in the DD line. FIG. 5 is a partial cross-sectional view taken along the line CC of FIG. 3 for explaining the configuration in the vicinity of the recess provided in the heat sink. The power semiconductor device according to the first embodiment is characterized by the structure between the heat sink and the sealing resin sandwiching the insulating film and the lead frame. First, the basic configuration of the power semiconductor device and members is described. explain.

  As shown in FIG. 1, the power semiconductor device 1 is a DIP (Dual Inline Package) type power semiconductor device in which power lead terminals 5 </ b> L and control lead terminals 6 </ b> L are arranged on both side surfaces in the longitudinal direction. As shown in FIGS. 2 and 3, a power circuit lead frame 5 (power lead) and a control circuit lead frame 6 (control lead) formed by punching a copper plate are provided. A diode 2 as a rectifying element made of a wide band gap semiconductor material such as silicon carbide (SiC) and a MOSFET (Metal Oxide Semiconductor Field-Effect-Transistor) transistor 3 as a switching element are mounted. A power circuit that controls the flow of the main current for power in the power semiconductor device is formed. The control lead 6 is mounted with an IC 4 that is an integrated circuit of a semiconductor element made of, for example, silicon (Si), and a control circuit for controlling the operation of the transistor 3 that is a power semiconductor is formed. Yes.

  The power lead 5 has a die pad for mounting the diode 2 and the transistor 3 by arranging a plurality of plate-like wiring members, and a flat circuit portion 5C having a wiring pattern structure for forming a power circuit on one end side. A power lead terminal 5L, which is a connection terminal for forming a main current path to the external circuit, is formed on the other end side. Similarly, a circuit portion 6C having a die pad for mounting the IC 4 and a wiring structure for forming the control circuit and a relay terminal with the power circuit is formed on one end side of the control lead 6, and connected to an external circuit. A control lead terminal 5L, which is a connection terminal, is formed on the other end side. Six sets of diodes 2 and transistors 3 are bonded to the surface of the die pad in the circuit portion 5C of the power lead 5 with solder 9a, respectively, and the IC 4 is electrically conductive adhesive to the surface of the die pad in the circuit portion 6C of the control lead 6. It is fixed at 9b. Note that the control lead 6 and the power lead 5 have a complicated and complicated shape when seen in a plan view, and originally a divided part and a continuous part are mixed in a cross section cut by one straight line. In FIG. 2, for the sake of simplification, portions other than those that should be distinguished in the description are drawn in a connected state.

  As described above, the diode 2 and the transistor 3 constituting the power circuit are mainly composed of SiC, which is a wide band gap semiconductor material, and are used at a high temperature (200 to 300 ° C.) during actual operation. A high melting point is required. Furthermore, in consideration of the environment, so-called lead-free solder that does not contain Pb is preferable, for example, Sn—Sb system and Au—Sn system are preferable.

  The connection between the diode 2 or the transistor 3 and the circuit unit 5C is not limited to solder, and any material having excellent conductivity such as a conductive adhesive such as a sinterable silver paste may be used. Considering the temperature during actual operation, it is preferable that the usable temperature is 200 ° C. or higher and has a certain degree of adhesive strength.

  Of the upper electrode of the transistor 3, an electrode (for example, a source electrode) through which a main current for power that becomes a large current flows and the diode 2 are electrically connected by a wiring member 10 a made of an aluminum wire, and the diode 2 The base portion of the power lead terminal 5L is also electrically connected by a wiring member 10a made of an aluminum wire. The transistor 3 and the relay terminal of the control lead 6 are also connected by a wiring member 10a. In the wiring member 10a, for example, between the transistor 3, the diode 2, and the lead terminal 5L may be formed continuously as shown in FIG. Further, the wiring member 10a is not limited to aluminum, and an alloy containing aluminum as a main component or other metals may be used.

  On the other hand, the IC 4 in the control circuit, the base portion of the control lead terminal 6L, and the relay terminal of the circuit portion 6C are electrically connected by a metal thin wire 10b made of gold. The fine metal wire 10b is for applying a voltage for control, and does not require a large current to flow, and is required to be connected to a narrow electrode formed on the integrated circuit IC4. A wire having a diameter smaller than 10a is preferable. Gold is preferable as a material because of its ease of joining with IC4. However, if these specifications are satisfied, an alloy containing gold as a main component, other metals such as copper, aluminum, or alloys thereof may be used. You may use.

Of the power lead 5, an insulating film 7 having high heat dissipation and insulating properties is bonded to the back surface of the circuit portion 5 </ b> C (the surface opposite to the surface where the semiconductor elements 2 and 3 are bonded). Further, a heat radiating plate 8 (heat sink) made of aluminum for heat dissipation is bonded thereto. The insulating film 7 is composed of an inorganic filler such as Al ₂ O ₃ and SiO ₂ having high insulation and thermal conductivity, and an organic binder such as epoxy resin having high electrical resistivity, and has both high heat dissipation and insulation. ing. The filler may be a material other than the ceramic material described above as long as it has a high thermal conductivity and an insulating property. The binder may contain an organic component other than the epoxy resin, or may not contain the epoxy resin.

  Of the members, the power lead terminal 5L portion, the control lead terminal 6L portion, and the portion excluding the heat radiating surface 8r of the heat radiating plate 8 are packaged (molded) by sealing with the sealing resin 11. . As a result, the power semiconductor device 1 is a so-called 6 in 1 three-phase inverter circuit as a power circuit, and becomes a transfer mold type IPM (Intelligent Power Module) in which an IC is incorporated in a control circuit. It should be noted that attachment holes 11h for attachment to heat radiation fins (not shown) are provided in the sealing body 11 at or near the longitudinal ends of the heat radiation plate 8 of the power semiconductor device 1. This is because, when the power semiconductor device 1 is actually used, screws are fixed to the heat radiating surface 8r of the heat radiating plate 8 of the power semiconductor device 1 through external heat radiating fins or the like and heat conductive grease as necessary. By installing the attachment holes 11h at both ends of the heat radiating plate 8 or in the vicinity thereof, the heat radiating surface 8r and the external heat radiating fins can be securely fixed, and thus excellent heat dissipation can be secured.

Next, features of the power semiconductor device according to the first embodiment will be described.
As shown in FIG. 4, the heat sink 8 is provided with a recess 8d, and the insulating film 7 is provided with a through hole 7h. The insulating film 7 is overlaid on the heat radiating plate 8 so that the recessed portion 8d and the through hole 7h are in the same position in the planar direction. Then, when the power leads 5 are stacked, as shown in FIGS. 3 and 5, the opening portion by the recess 8d and the through hole 7h is designed to fit within the gap 5Cs formed in the circuit portion 5C. is there. That is, the plate-like wiring material (metal plate portion) of the circuit portion 5C is prevented from covering the recess 8d and the opening of the through hole 7h. As will be described later, a part of the sealing body 11 bites into the recessed portion 8d. The through hole 7h does not necessarily have the same shape as the opening of the recessed portion 8d, and may have a diameter that allows resin to pass as described later.

A method for manufacturing the power semiconductor device 1 using the above members will be described.
The lead frames 5 and 6 are positioned and fixed using a jig (not shown), and circuit mounting is performed. As shown in FIGS. 2 and 3, the diced IC 4 is fixed to the die pad formed on the circuit portion 6C formed on the control lead 6 portion by the conductive adhesive 9b. Next, the diode 2 and the transistor 3 are each die-bonded to the die pad formed on the circuit portion 5C of the power lead 5 with the solder 9a.

  Then, the transistor 3 on the power circuit side and the diode 2 are electrically connected by wire bonding using an aluminum wire wiring member 10a, and the diode 2 and the power lead terminal 5L are wired using an aluminum wire wiring member 10a. Electrical connection by bonding. Further, the relay terminals of the transistor 3 and the control lead 5 are electrically connected by wire bonding. Subsequently, the IC 4 in the control circuit, the control lead terminal 6L, and the relay terminal are electrically connected by wire bonding using a fine metal wire 10b made of gold. Thereby, the circuit member provided with the power circuit and the control circuit which controls the power circuit is formed.

  Apart from the formation of the circuit member, the heat sink 8 is prepared. A metal plate (for example, an aluminum plate) having a predetermined thickness is punched into a heat sink shape with a press, and then the recess 8 d is processed to form the heat sink 8. An insulating film previously formed in a sheet shape is cut out, and a through hole is formed at a predetermined position to form the insulating film 7. The insulating film 7 is overlaid on the heat radiating plate 8 so that the through hole 7h is located at the position of the opening of the recess 8d in the planar direction. Then, both members are temporarily bonded by applying temperature and pressure with a press. At this time, it is desirable to put a cushioning material such as paper between the press and the insulating film 7 so that the pressure is uniformly applied. Thereby, the heat sink 8 to which the insulating film 7 is temporarily bonded can be prepared.

  The heat radiating surface 8r side of the heat radiating plate 8 is placed on a heat source, and the circuit member is installed on the upper surface of the insulating film 7. At this time, the recessed portion 8d and the opening portion formed by the through hole 7h are installed so as to be within the range of the gap 5Cs formed in the power lead 5. And after mold clamping, sealing resin 11R which comprises the sealing body 11 is poured, and it seals. At this time, since the binder constituting the insulating film 7 is also cured, the insulating film 7 is firmly bonded to the heat sink 8 and the power lead 5. Further, the sealing resin 11R flows into the recess 8d through the gap 5Cs between the plate-like wiring members of the power lead 5 and the through hole 7h of the insulating film 7. The sealing resin 11R that has flowed into the hollow portion 8d is integrally cured with the main body of the sealing body 11 to form a biting portion 11a (see FIG. 2B) that bites into the heat radiating plate 8.

  The power lead terminal 5L, the control lead terminal 6L, and the heat radiating surface 8r of the heat radiating plate 8 are exposed from the sealing resin 11 to the outside. The power semiconductor device 1 is completed by performing lead forming so that the power lead terminal 5L and the control lead terminal 6L exposed from the sealing resin have a predetermined lead shape. The surfaces of the lead frames 5 and 6 are subjected to surface processing by a technique such as plating as necessary.

  In the above-described molding process, since the resin is generally cured and contracted, the contracted resin pulls the heat sink toward the center when returning to room temperature after transfer molding. On the other hand, the reaction force to return the heat sink to its original shape works as residual stress. When exposed to an environment with a temperature difference in this state, a thermal stress due to a difference in linear expansion coefficient acts between the heat sink and the insulating film or between the insulating film and the sealing body, thereby reducing the adhesive strength. When SiC is used as the power semiconductor element, it may be exposed to a very large temperature difference such that the high temperature side is 175 ° C. and the low temperature side is room temperature. In the worst case, delamination may occur at the part where the adhesive strength is weak, and when peeling occurs, the potential gradient concentrates on the boundary between the peeled part and the part that has not peeled off, causing partial discharge, Becomes lower. In particular, in order to cope with high temperature operation, it is necessary to increase the filler filling rate in order to increase the heat dissipation of the insulating film, and the ratio of the binder responsible for adhesion is relatively reduced, and the adhesive strength is lowered. For this reason, the higher the operating temperature, the greater the thermal stress, whereas the adhesive strength to counteract it decreases, so peeling is more likely to occur and the pressure resistance performance also tends to decrease. End up.

  On the other hand, in the power semiconductor device 1 according to the first exemplary embodiment of the present invention, the sealing body 11 bites into the heat sink 8 through the gap (5Cs, 7h) between the circuit portion 5C and the insulating film 7. It has. Since the biting portion 11a exhibits an anchor effect on the heat sink 8, even if a temperature cycle occurs, the heat sink 8 is warped or distorted with respect to the seal 11, or the seal 11 is warped with respect to the heat sink 8. Distortion is suppressed. That is, the distance between the sealing body 11 and the heat radiating plate 8 sandwiching the circuit portion 5C and the insulating film 7 is limited to the change in the expansion and contraction of the member that is interposed therebetween, and the change in parallelism is suppressed. In other words, there is no room for a local release layer between the heat sink 8 to the insulating film 7 to the circuit portion 5C to the sealing body 11, so that the plate-like wiring material and the heat sink 8 constituting the circuit portion 5 of the insulating film 7 are eliminated. Peeling can be suppressed, and the pressure resistance performance can be maintained. Therefore, the performance of a wide band gap semiconductor such as SiC can be exhibited, and long-term insulation can be ensured even when used at a higher temperature than a conventional Si semiconductor such as 175 ° C. Furthermore, since no release layer is formed, heat transfer is ensured, and high heat dissipation efficiency is ensured for a long period of time.

  In addition, the insulating film 7 may entrain air in the process of mixing the raw materials and the like, and bubbles may be generated during the transfer molding process. At this time, bubbles generated near the center of the insulating film are difficult to escape and may be trapped in the insulating film or at the interface. In particular, the larger the area of the insulating film, the more easily trapped.

  On the other hand, in the power semiconductor device 1 according to the first embodiment of the present invention, since the through-hole 7h is provided in the insulating film 7, bubbles generated when heated are removed from the through-hole 7h. For this reason, voids as bubbles do not remain in the insulating film 7, a decrease in dielectric strength is suppressed, and insulation reliability can be ensured even when a larger current is handled. Preventing voids from remaining also leads to securing heat transfer properties, and also has the effect of securing high heat dissipation efficiency for a long period of time.

  On the other hand, the insulating film 7 is once softened into a gel when thermally cured. Therefore, even if the hole diameter of the through-hole 8h of the insulating film 7 is the same as the hole diameter of the recessed portion 8d of the heat sink 8 at the stage of temporary bonding, as shown in FIG. After the film 7 partially protrudes toward the inside of the opening of the recess 8d, the film 7 is cured and remains as the protrusion 7e. Since the protruding portion 7 e functions as an anchor for the heat sink 8, the adhesive strength between the insulating film 7 and the heat sink 8 is further increased.

In addition, since it is necessary to secure an insulation distance between the plate-like wiring member, which is a conductive portion of the power lead 5 (circuit portion 5C), and the heat radiating plate 8, the through hole 7h in the gap 5Cs of the circuit portion 5C. The gap 5Cs (the width D _Lh ) between the plate-like wiring members that surround the plate is made wider than the gap (the width D _Ln ) between the plate-like wiring members that do not surround the through hole 7h. Moreover, although the opening shape of the hollow part 8d has described about the square thing in the figure, it does not need to be a rectangle and may be a round shape or a polygon.

  As described above, according to the power semiconductor device 1 according to the first embodiment of the present invention, the power semiconductor elements 2 and 3 and the circuit portion 5C formed flat by arranging a plurality of plate-like wiring members, A lead frame 5 having a connection terminal 5L to an external circuit, the power semiconductor elements 2 and 3 being mounted on one surface of the circuit portion 5C, and a heat dissipation surface 8r with respect to the other surface of the circuit portion 5C. The opposite surface of the heat sink is bonded via the insulating film 7, and the heat sink is formed with a recess 8d facing the gap 5Cs between the plate-like wiring members of the circuit portion 5C and opening within the gap. 8 and a sealing body 11 that seals the power semiconductor device 1 except for the connection terminal 5L of the lead frame 5 and at least the heat radiating surface 8r of the heat radiating plate 8, and the insulating film 7 includes a heat radiating plate 8 The through hole 7h corresponding to the position of the recess 8d is formed, and the sealing body 11 is It is configured to have a biting portion 11a that bites into the inside of the recess 8d of the heat sink 8 from the surface side where the semiconductor elements 2 and 3 of the road surface 5C are mounted through the gap 5Cs between the plate-like wiring members and the through hole 7h of the insulating film 7. Therefore, the biting portion 11 a of the sealing body 11 serves as an anchor to the heat radiating plate 8, and the circuit portion 5 C of the lead frame 5 and the insulating film 7 can be sandwiched between the sealing body 11 and the heat radiating plate 8. Therefore, even if the adhesiveness is reduced by increasing the filler filling rate in order to prioritize the heat dissipation of the insulating film 7, the insulating film 7 is not peeled off from the circuit portion 5 </ b> C or the heat sink 8 of the lead frame 5. Thus, a highly reliable power semiconductor device can be obtained while maintaining the withstand voltage.

In particular, the recess 8d is formed so as to be opposed to a large gap among the gaps between the plate-like wiring members. Alternatively, the circuit portion 5C is formed so that the gap 5Cs (width D _Lh ) facing the depression 8d is wider than the gap (width D _Ln ) between other plate-like wiring members. With this configuration, it is possible to maintain the insulation distance around the depression 8d and increase the withstand voltage.

Embodiment 2. FIG.
The power semiconductor device according to the second embodiment is different from the power semiconductor device according to the first embodiment in the shape of the recess provided in the heat sink. Since other members are the same as those of the power semiconductor device according to the first embodiment, description thereof is omitted. 6 to 8 are diagrams for explaining the configuration of the power semiconductor device according to the second embodiment. FIG. 6 is a plan view of the power semiconductor device in which a heat sink and a power lead frame portion are extracted. It is. FIG. 7 is a diagram for explaining the configuration near the recess provided in the heat sink, FIG. 7 (a) is a partial cross-sectional view taken along line EE of FIG. 6, and FIG. The fragmentary sectional view which shows the state at the time of temporarily bonding an insulating film is shown. FIG. 8 is a partial cross-sectional view for explaining the difference in the configuration near the recess provided in the heat sink according to the second embodiment and the first embodiment, and FIG. 8 (a) is shown in FIG. 6 (a). FIG. 8B corresponds to FIG. 5, and some lines visible in the background are omitted in order to clarify the dimension object.

  As shown in FIGS. 6 and 7A, the power semiconductor device 201 according to the second embodiment has an inclined portion 208da at the opening (inlet) portion of the recess 208d provided in the heat sink 208. It is a thing. Then, as shown in FIG. 7B, the press mold 20 when the insulating film sheet 207S is temporarily bonded to the heat radiating plate 208 is provided with a triangular projection 20p that matches the shape of the inclined portion 208da. Yes. If the protrusion 20p is pressed in accordance with the inclined portion 208da of the recess 208d of the heat sink 208 during pressing, the pressing pressure can be uniformly applied to the inclined portion 208da through the insulating film 207. At this time, the cushioning material 21 is placed between the press die 20 and the insulating film sheet 207S, and the triangular protrusion 20p breaks through the cushioning material 21 and the insulating film sheet 207S and presses the inclined portion 208da during pressing. As a result, as shown in FIG. 6, the insulating film 207 can be formed with a through hole 207h corresponding to the recess 208d. As shown in FIG. 7A, the inclined portion 208da has an inclined portion. The insulating film 7 is adhered along 208da.

In this manner, the fact that the size of the power semiconductor device can be reduced as compared with the first embodiment by deforming the depression so as to have the inclined portion 208da will be described with reference to FIG. FIG. 8 illustrates the insulation distance between the plate-like wiring members of the circuit portion that is joined to the heat sink via the insulating film in the power leads, and the interval between the plate-like wiring members that surround the through holes. The relationship between D _Lh and the creeping distance D _cr between the plate-like wiring member and the heat sink is shown. In the figure, the creepage distance D _cr2 (FIG. 8A) between the circuit unit 205C and the heat sink 208 in the power semiconductor device according to the second embodiment and the power semiconductor device according to the first embodiment The creepage distance D _cr1 (FIG. 8B) between the circuit portion 5C and the heat sink 8 is set to be substantially the same. However, when the power semiconductor device according to the second embodiment, the insulating film 207 along the inclined portion 208Ad, since the advance to the depth direction of the recess 208, to secure the same creepage distance D _cr, performed The interval D _Lh2 between the plate-like wiring _members can be set shorter than the interval D _Lh1 between the plate-like wiring _members surrounding the through hole 8d in the circuit portion 5C of the power lead in the power semiconductor device of the first embodiment. Therefore, the product itself can be reduced in size by reducing the size of the circuit portion 205C of the power lead 205.

  Further, the insulating film 207 is bonded along the inclined portion 208da, and the insulating film 207 becomes an anchor to the heat sink 208 in the recessed portion by the inclined portion 208da, thereby increasing the adhesive strength and maintaining long-term insulation even at higher temperatures. be able to.

  In the second embodiment, the example in which the projection 20p becomes a punching tool and the through hole is punched in the insulating film sheet 207S by the press at the time of temporary bonding is shown. However, the hole is previously punched in the sheet. You may make it leave. In that case, it is necessary to align the position of the drilled through hole with the position of the recess 208d of the heat sink, but the hole shape becomes constant, and it is possible to prevent cracks and the like from being generated around the through hole.

  As described above, according to the power semiconductor device 201 of the second embodiment, the recess 208d is configured such that the inclined portion 208da that becomes narrower as it becomes deeper from the opening is formed. By sticking the insulating film 7 along the line, the adhesion between the insulating film 207 and the heat sink 208 is improved, and peeling can be further suppressed.

  Further, by passing through the inclined portion 208da, the creepage distance between the circuit portion 205C and the heat radiating plate 8 can be increased even if the interval between the plate-like wiring members is narrowed, so the size of the circuit portion 205C is reduced. In addition, the entire apparatus can be made compact.

Embodiment 3 FIG.
The power semiconductor device according to the third embodiment is different from the power semiconductor devices according to the first and second embodiments in the shape of the recess provided in the heat sink. Since other members are the same as those of the power semiconductor device according to the first and second embodiments, description thereof is omitted. FIG. 9 is a partial cross-sectional view for illustrating the configuration of the power semiconductor device according to the third embodiment and showing the configuration of the vicinity of the recess provided in the heat sink.

  As shown in FIG. 9, in the power semiconductor device 301 according to the third embodiment, the recess 308 d provided in the heat sink 308 has an uneven inner surface along the depth direction like a screw hole. It is that. The recess 308d can be formed by cutting a tap. When the sealing resin 11R flows into the thread-like depression 308d and hardens, the anchor effect becomes stronger, the peeling is effectively suppressed, and the adhesive strength is increased even when thermal stress is applied at higher temperatures. Can be maintained.

  It should be noted that the inner surface of the recess is not limited to a screw, but may be uneven along the depth direction. For example, a spiral groove may be provided on the inner surface.

  As described above, according to the power semiconductor device 301 of the third embodiment, the recess 308d has grooves formed on the inner surface so as to be uneven along the thickness direction of the heat sink 308. As a result, the anchor effect is further strengthened, peeling can be suppressed, and the withstand voltage can be maintained.

Embodiment 4 FIG.
In the power semiconductor device according to the fourth embodiment, the recess provided in the heat sink is penetrated to the opposite side of the power semiconductor device according to the first to third embodiments. Since other members are the same as those of the power semiconductor device according to the first to third embodiments, description thereof is omitted. FIG. 10 is a partial cross-sectional view illustrating the configuration of the power semiconductor device according to the fourth embodiment and the configuration in the vicinity of the recess provided in the heat sink.

  As shown in the figure, in the power semiconductor device 401 according to the fourth embodiment, the recess 408d provided in the heat radiating plate 408 penetrates from the front surface side of the heat radiating plate 408 to the heat radiating surface 408r side of the back surface. In addition, although the dent 408d should originally be called a “hole”, it is common to the other embodiments in that it is recessed when viewed from the front surface side, and is therefore referred to as a “dent”. Other parts are the same as those of the other embodiments. At this time, for example, if the depression 408d is inclined (tapered) so that the diameter on the heat radiation surface 408r side is wider than the surface side, the anchor effect acting in the thickness direction can be further strengthened. Further, for example, if the inclined portion as in the second embodiment is formed in the opening portion on the heat radiation surface 408r side of the heat radiation plate 208 of the hollow portion 408d, the sealing body 11 bites on the back surface of the heat radiation plate 408, so that the anchor The effect can be further strengthened. Therefore, prevention of peeling is strengthened.

  Furthermore, since the dent 408d penetrates to the heat radiating surface 408r side of the heat radiating plate 408, bubbles can be extracted through the dent 208d during transfer molding. For this reason, bubbles can be discharged more efficiently, and the generation of voids can be suppressed.

  As described above, according to the power semiconductor device 401 according to the fourth embodiment, since the recess 408d is configured to penetrate through to the heat radiation surface 408r, the anchor effect is high. Furthermore, since the penetrating recess 408d becomes a vent hole, generation of voids can be suppressed.

  Further, if the dent 408d is perforated from the heat radiating surface 408r side and the heat radiating surface 408r side is formed in a wide tapered shape, the anchor effect can be further enhanced.

Embodiment 5 FIG.
In the power semiconductor device according to the fifth embodiment, the power semiconductor device according to the first to fourth embodiments is formed in a so-called groove shape in which a recess provided in the heat sink is extended in the surface direction. is there. Since other members are the same as those of the power semiconductor device according to the first to fourth embodiments, description thereof will be omitted. 11A and 11B are diagrams for explaining the configuration of the power semiconductor device according to the fifth embodiment. FIG. 11A is a plan view of a heat sink with an insulating sheet temporarily bonded thereto, and FIG. 11B is a diagram. It is sectional drawing in the FF line of 11 (a).

  The recessed portion 508d has a groove shape extending in a direction perpendicular to the longitudinal direction of the heat dissipation plate 508, and the through hole 507h accordingly has the same slit shape. In addition, a gap 505Cs wider than the opening is formed in the circuit portion 505C of the lead frame 505 (not shown), which is overlapped in a subsequent process, corresponding to the opening of the recessed portion 508d. Therefore, when the lead frame 505 is overlapped, the opening of the recessed portion 508d fits in the gap 505Cs of the circuit portion 505C, and the recessed portion 508d is not covered with the plate-like wiring material of the circuit portion 505C. Yes.

  And since the extending direction of the hollow part 508d is formed so as to be along (parallel) the injection direction of the sealing resin, when the sealing resin 11 is injected by transfer molding, the sealing resin 11R is formed in the hollow part 508d. The encapsulating resin 11R can be prevented from entraining air bubbles without hindering the flow. Further, after the sealing body is heated, it shrinks when it is cooled and cured. At this time, a force pulling the insulating film 507 and the heat radiating plate 508 to the inside acts, and the heat radiating plate 508 is warped with the back surface convex. For this reason, a force acts in the direction away from the interface between the insulating film 507 and the heat sink 508, and peeling off may occur when the force is increased at a high temperature. On the other hand, when the recess 508d extending in the direction perpendicular to the longitudinal direction of the heat sink 508 is provided, the recess 508d lowers the bending rigidity in the longitudinal direction, so that the warpage is reduced and the peeling force is suppressed.

  As described above, according to the power semiconductor device 501 of the fifth embodiment, since the recess 508d extends in the direction perpendicular to the longitudinal direction in the surface direction of the heat sink 508, the resin 11R is placed in that direction. If it is made to flow, the sealing body 11 can be formed without entraining bubbles. Moreover, since the rigidity with respect to the deformation | transformation of the longitudinal direction of the heat sink 508 falls, the curvature by a temperature change is reduced and peeling of the insulating film 507 can be suppressed.

  In each of the above embodiments, the case where a MOSFET is used as the transistor 3 serving as a switching element has been described. However, an IGBT (Insulated Gate Bipolar Transistor) may be used. In addition to silicon carbide, a material such as gallium nitride (GaN) or diamond may be used as the wide band gap semiconductor element material. Furthermore, it may be a case where only a MOSFET is used and a rectifying element such as a diode is not required.

  In each of the above embodiments, examples of so-called wide band gap semiconductor elements formed of silicon carbide have been shown as the semiconductor elements 2 and 3 that function as rectifier elements (diodes) and switching elements (transistors). However, the present invention is not limited to this, and it may be formed of silicon (Si). However, as described above, the operating temperature range is higher when silicon carbide, a gallium nitride-based material, or diamond that can form a so-called wide gap semiconductor having a larger band gap than silicon is used. Can be further exhibited.

DESCRIPTION OF SYMBOLS 1 Power semiconductor device, 2 Diode (power semiconductor element), 3 Transistor (power semiconductor element), 4 IC (control semiconductor element (integrated circuit)), 5 Power lead (lead frame (5C: circuit part, 5Cs: clearance, 5L: power lead terminal)),
6 control lead (lead frame (6C: circuit part, 6L: control lead terminal)), 7 insulating film (7h: through hole, 7S: insulating film sheet before processing), 8 heat sink (8d: recessed part ( 8da: inclined portion), 8r: heat dissipation surface), 9 conductive joining member (9a: solder, 9b: conductive adhesive), 10 wiring member, 11 sealing body (11a: biting portion),
20 press mold (20p: protrusion), 21 cushioning material,
D _Lh gap width, D _cr creepage distance,
The difference in the hundreds indicates the difference in configuration according to the embodiment.

Claims (8)

A power semiconductor element;
A lead frame in which a plurality of plate-like wiring members are arranged and formed flat and a connection terminal to an external circuit, and the power semiconductor element is mounted on one surface of the circuit portion,
The other surface of the circuit portion is opposite to the heat dissipation surface through an insulating film, and is opposed to the gap between the plate-like wiring members of the circuit portion, and is opened in the gap. A heat sink in which a recess is formed;
A sealing body that seals the power semiconductor device except for the connection terminal of the lead frame and at least the heat dissipation surface of the heat dissipation plate;
In the insulating film, a through hole corresponding to the position of the depression of the heat sink is formed,
The sealing body has a biting portion that bites into the inside of the recess of the heat sink from the side of the circuit surface where the semiconductor element is mounted through the gap between the plate-like wiring members and the through hole of the insulating film. A power semiconductor device characterized by the above.   2. The power semiconductor device according to claim 1, wherein the recess is formed to be opposed to a large gap among the gaps between the plate-like wiring members.   The power semiconductor device according to claim 1, wherein the recess is formed with an inclined portion that becomes narrower as it becomes deeper from the opening.   4. The power semiconductor device according to claim 1, wherein the recess has a groove formed on an inner surface so as to be uneven along the thickness direction of the heat radiating plate. 5.   5. The power semiconductor device according to claim 1, wherein the recess penetrates to the heat radiation surface. 6.   6. The power semiconductor device according to claim 1, wherein the recess extends in a direction orthogonal to a longitudinal direction in a surface direction of the heat radiating plate.   7. The power semiconductor device according to claim 1, wherein the power semiconductor element is made of a wide band gap semiconductor material.   The power semiconductor device according to claim 7, wherein the wide band gap semiconductor material is any one of silicon carbide, gallium nitride, and diamond.

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