JP2016225365A - Power semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power semiconductor device which enables improvement of the reliability and reduces a mounting area of a chip type electronic component to achieve downsizing.SOLUTION: A power semiconductor device 100 includes: a lead frame including a first electrode 11 and a second electrode 12 which are separated from each other; a power semiconductor element mounted on the lead frame; a multilayer ceramic capacitor 30 which is disposed on the first electrode 11 and provided with external electrodes 32, 33 located at both sides; and an electric insulator which seals a part of the lead frame, the power semiconductor element, and the capacitor 30. The lower external electrode 32 of the capacitor 30 is joined to the first electrode 11, and the upper external electrode 33 is joined to the second electrode 12 through a conductor member 80 having an L-shaped part 81. The conductor member 80 has rigidity lower than that of the capacitor 30.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a power semiconductor device in which a power semiconductor element is mounted on a lead frame, and more particularly to a power semiconductor device mounted on an in-vehicle device.

  Conventionally, as a power semiconductor device mounted on an in-vehicle device, a case type in which a power semiconductor element is soldered on an electrically insulating substrate on which a wiring pattern is formed, and connected with a wiring member is resin-sealed. A combination of a power semiconductor device and a discrete power semiconductor device in which a power semiconductor element such as a diode or MOSFET is transfer-molded has been used.

  In switching elements such as MOSFETs and IGBTs (Insulated Gate Bipolar Transistors) among power semiconductor elements, current flows intermittently due to switching and voltage fluctuation occurs. In order to reduce this voltage variation, a capacitor is generally provided in the vicinity of the element. However, when a capacitor is provided, there is a problem that the semiconductor device is increased in size, and this problem is particularly remarkable in a power semiconductor device that is mounted on an in-vehicle device having a limited arrangement space.

  Patent Document 1 discloses a semiconductor device in which an integrated circuit (IC chip) that handles low power is molded, and a chip between a power supply electrode and a die pad that supports an IC chip mounting stage in a lead frame. A type capacitor is disclosed. This chip type capacitor functions as a bypass capacitor for connecting the power source and the ground. According to this semiconductor device, the mounting density is improved by molding the whole.

  Further, Patent Document 2 is a method of mounting an electronic component on a substrate on which electrodes separated from each other are formed, and a spacer such as an electric insulating film is temporarily disposed on the substrate so that the electronic component is mounted. A method is disclosed in which leads provided on both sides of an electronic component are joined to electrodes of a substrate using solder in a state where the height is secured. According to this method, by increasing the thickness of the solder, the stress concentration caused by the difference in thermal expansion coefficient between the substrate and the electronic component is alleviated when subjected to a temperature cycle, and the deterioration of the solder and the electronic component Can be prevented.

JP 59-072757 A JP 2004-31768 A

  However, as described in Patent Document 1, when a chip-type electronic component such as a capacitor is mounted on a die pad of a lead frame and molded, a power semiconductor element that handles high power undergoes a temperature cycle. In addition, stress concentration occurs in the capacitor due to a difference in linear expansion coefficient between the metal member constituting the apparatus and the mold resin. As a result, there is a possibility that the capacitor may deteriorate or break down, which is problematic in terms of reliability.

  Further, in the method described in Patent Document 2, since the leads provided on both sides of the electronic component are joined to the electrodes, the mounting area of the electronic component is increased, and miniaturization of the power semiconductor device is prevented.

  The present invention has been made to solve the above-described problems, and has an object to provide a power semiconductor device that is reduced in size by improving reliability and reducing the mounting area of a chip-type electronic component. To do.

  To achieve the above object, a power semiconductor device according to the present invention includes a lead frame including a first electrode and a second electrode separated from each other, a power semiconductor element mounted on the lead frame, and a first electrode. A chip-type electronic component disposed on the both ends and provided with external electrodes at both ends, and a part of the lead frame, a power semiconductor element, and an insulator that seals the chip-type electronic component. The external electrode is joined to the first electrode, the other external electrode of the chip-type electronic component is joined to the second electrode via a conductor member having an L-shaped part, and the conductor member is more than the chip-type electronic component. It is characterized by low rigidity.

  According to the present invention, when the chip-type electronic component is joined onto the second electrode via the conductor member having the L-shaped portion having lower rigidity than the chip-type electronic component, the conductor member is subjected to stress. Since the L-shaped part of this is preferentially deformed, stress concentration on the chip-type electronic component can be alleviated. In this way, the reliability of the power semiconductor device can be improved.

  In addition, since only one external electrode of the chip-type electronic component is bonded to the first electrode, the bonding area between the conductor member and the second electrode is reduced, so that the mounting area of the chip-type electronic component is reduced, and the power semiconductor The device can be miniaturized.

It is sectional drawing which looked at the power semiconductor device which concerns on Embodiment 1 of this invention from upper direction. It is sectional drawing which looked at the multilayer ceramic capacitor part of FIG. 1 from the side. It is sectional drawing corresponding to FIG. 2 which shows the power semiconductor device which concerns on Embodiment 2 of this invention. It is a perspective view which shows a part of conductor member of the power semiconductor device which concerns on the 1st modification of Embodiment 2 of this invention. 5A is a perspective view corresponding to FIG. 4 and FIG. 5B is a cross-sectional view showing a part of a conductor member of a power semiconductor device according to a second modification of the second embodiment of the present invention. It is a perspective view which shows a part of power semiconductor device which concerns on Embodiment 3 of this invention.

  Hereinafter, a power semiconductor device according to an embodiment of the present invention will be described with reference to the drawings. In each figure, the same or similar components are denoted by the same reference numerals. Further, the terms “upper, lower, right, left, horizontal, vertical” and the like representing the direction are for the purpose of specifying the direction in the drawing, and do not limit the installation direction of the apparatus.

Embodiment 1 FIG.
1 is a cross-sectional view of a power semiconductor device according to a first embodiment of the present invention as viewed from above, and FIG. 2 is a cross-sectional view of a part of FIG. 1 as viewed from the side. In the figure, the direction in the xy plane defined by the x direction and the y direction perpendicular to each other is referred to as the horizontal direction, and the z direction perpendicular to the horizontal plane is referred to as the vertical direction.
As shown in FIG. 1, the power semiconductor device 100 includes a lead frame 10, power semiconductor elements 21 to 23, a multilayer ceramic capacitor 30, a resistance element 40, and an insulator (electrical insulator) 50. The power semiconductor elements 21 to 23, the multilayer ceramic capacitor 30 and the resistance element 40 are chip-type electronic components.

  The power semiconductor device 100 is fixed to an object to be fixed, for example, an in-vehicle device via an electrically insulating adhesive, a substrate, a sheet, or the like. Alternatively, the power semiconductor device 100 may have an insulating layer on the surface facing the object to be fixed, and may be pressure-fixed to the object to be fixed using solder, heat radiation grease, or the like.

  The lead frame 10 is formed in a wiring pattern. The lead frame 10 has power terminals 11 to 15 through which a large current of several A to several hundreds A flows, and signal terminals 16 to 18 that transmit control signals (for example, gate signals) to the power semiconductor elements 21 to 23. The terminals 11 to 18 are separated from each other and protrude from the insulator 50 to the outside. The power terminals 12 and 14 are connected by a resistance element 40 constituting an attenuator. The power terminals 11 to 15 are connected to a power supply device and a power source (battery or the like) via a relay member. The signal terminals 16 to 18 are connected to the control board.

  Each of the terminals 11 to 18 of the lead frame 10 is formed by pressing, etching, or the like. By this molding process, a step (a difference in length (height) in the vertical direction) of several μm to several hundred μm inevitably occurs between the upper surfaces (main surfaces) of the terminals 11 to 18. Thus, each terminal 11-18 is arrange | positioned in the substantially same plane. The lead frame 10 is made of metal, for example, Kovar, copper plate, copper alloy plate plated with nickel (Ni) is used.

  The power semiconductor elements 21 to 23 are switching elements such as MOSFETs and IGBTs. The power semiconductor elements 21, 22, and 23 are mounted on the power terminals 11, 13, and 14, respectively, using a conductive bonding material such as solder and conductive paste (for example, silver paste). The main electrodes of the power semiconductor elements 21, 22, and 23 are electrically connected to the power terminals 13, 14, and 15 by two wiring members 61, 62, and 63, respectively. The control electrodes of the power semiconductor elements 21, 22, and 23 are electrically connected to the signal terminals 16, 17, and 18 by wiring members 64, 65, and 66, respectively. For example, the wiring members 61 to 66 may be aluminum (or copper) circular cross-section (or rectangular cross-section) wire-like members provided by ultrasonic bonding, or may be soldered metal terminals. Good.

  The power semiconductor elements 21 to 23 may be formed of silicon (Si), or may be formed of a wide gap semiconductor material having a band gap larger than that of silicon. The wide gap semiconductor material is, for example, silicon carbide (SiC), gallium nitride (GaN) -based material, or diamond. The power semiconductor elements 21 to 23 formed of a wide gap semiconductor material have a high withstand voltage and a high allowable current density, and thus can be miniaturized. By using the miniaturized power semiconductor elements 21 to 23, the power semiconductor device 100 incorporating this can also be miniaturized.

  A multilayer ceramic capacitor (hereinafter referred to as a capacitor) 30 is disposed on the power terminal 11. The capacitor 30 has a function of reducing voltage fluctuation due to switching of the power semiconductor elements 21 to 23. In order to fulfill this function, the capacitor 30 is preferably arranged in the vicinity of the power semiconductor element 21. The capacitor 30 includes a multilayer body 31 and external electrodes 32 and 33 provided at both ends of the multilayer body 31. Inside the multilayer body 31, ceramic dielectric bodies 31a and internal electrodes 31b are alternately laminated as shown in FIG. The capacitor 30 is arranged so that the stacking direction of the ceramic dielectric 31a and the internal electrode 31b matches (or substantially matches) the horizontal direction. In FIG. 2, the stacking direction is the x direction, but it may be in the horizontal direction. Thereby, the external electrodes 32 and 33 face each other vertically. The external electrodes 32 and 33 are alternately connected to the internal electrode 31 b of the multilayer body 31.

  One (lower) external electrode (lower external electrode) 32 of the capacitor 30 is bonded to the power terminal 11 using a conductive bonding material 71. The other (upper) external electrode (upper external electrode) 33 of the capacitor 30 is bonded to the conductor member 80 using a conductive bonding material 72. The conductor member 80 is bonded to the power terminal 12 using a conductive bonding material 73. The rigidity of the conductor member 80 is lower than that of the capacitor 30 and the conductive bonding materials 71 to 73. The conductive bonding materials 71 to 73 are, for example, solder or conductive paste (for example, silver paste).

  In use, the power terminal 11 has a higher potential than the power terminal 12. Thus, the capacitor 30 is mounted between two adjacent terminals having different potentials when used. The power terminals 11 and 12 are examples of the first electrode and the second electrode, respectively.

  The conductor member 80 includes an L-shaped portion 81, a plate-shaped bonded portion 84 that extends in the horizontal direction (x direction in the drawing) from one end (lower end) of the L-shaped portion 81 and is bonded to the power terminal 12. Have The L-shaped portion 81 is joined to the upper external electrode 33 of the capacitor 30 and extends along the horizontal direction (x direction in the figure), and is connected to the first plate portion 82 at one end and the other. The second plate portion 83 is joined to the joined portion 84 at the end and extends along the vertical direction. As described above, the conductor member 80 bridges the two power terminals 11 and 12 three-dimensionally. The first plate portion 82 and the second plate portion 83 do not have to be orthogonal. The area of the bonded portion 84 is smaller than the area of the lower external electrode 32.

  As shown in FIG. 2, the bonded portion 84 extends a distance D from the lower end of the second plate portion 83 in the horizontal direction (x direction in the drawing). The length (height) of the second plate portion 83 in the vertical direction is H. The height of the second plate portion 83, that is, the height H of the conductor member 80 is preferably 2 times or more and 5 times or less the distance D. It has been found that by setting the height H of the conductor member 80 within this range, the rigidity of the L-shaped portion 81 of the conductor member 80 can be reduced and the L-shaped portion 81 can be preferentially deformed. Yes.

  The conductor member 80 may be formed by bending a single conductor plate, or may be formed by joining a plurality of conductor plates. There is an advantage that the conductor member 80 can be easily formed by molding the conductor member 80 with a single conductor plate.

  The insulator 50 is, for example, an epoxy resin, and seals a part of the lead frame 10, the power semiconductor elements 21 to 23, the capacitor 30, the resistance element 40, and the like provided on the lead frame 10.

The power semiconductor device 100 having the above configuration can be manufactured, for example, by the following steps S1 to S3.
(S1) Each chip component is bonded onto the lead frame 10 arranged in a wiring pattern using a conductive bonding material.
(S2) The wiring member 3 is ultrasonically bonded to the power semiconductor elements 21 to 23 and the terminals 11 to 18 to manufacture an intermediate structure.
(S3) The intermediate structure is transfer molded using the insulator 50.
In step S1, the capacitor 30 joins the lower external electrode 32 on the power terminal 11 using the conductive bonding material 71, and then uses the conductive bonding materials 72 and 73 to connect the upper external electrode 33 and the power terminal. It is mounted by bonding a conductor member 80 on 12.

  In the power semiconductor device 100, the power semiconductor elements 21 to 23 are switched by the control signals transmitted from the signal terminals 16 to 18 connected to the control board, and the amount of current supplied to the power terminals 11 to 15 for output is controlled. Is done.

Next, effects obtained by the first embodiment will be described.
In the description of this effect, the structure in which the external electrodes at both ends of the capacitor are joined between the two terminals of the lead frame as in the first embodiment is referred to as a “comparative example”. In the comparative example, in the first embodiment, the external electrodes 32 and 33 are joined to the power terminals 11 and 12, respectively. That is, in the conventional structure, the external electrodes 32 and 33 are opposed to the left and right.

  Generally, the temperature of an in-vehicle power semiconductor device varies greatly due to the operation of the in-vehicle device, the change in atmosphere in which the power semiconductor element is installed, the energization of the power semiconductor element, and the like. Therefore, when a capacitor is mounted on a lead frame and molded, the structure of the comparative example causes stress concentration in the capacitor due to the difference in coefficient of linear expansion between the metal member constituting the device and the mold resin. May occur. Also, when the intermediate structure before transfer molding (produced in the above-described step S2 in the first embodiment) is transported on the production line, due to vibration during transport or external force acting during transport, There is a risk of stress concentration in the capacitor. Further, as described above, there is a step of about several μm to several hundred μm between the terminals constituting the lead frame. When the intermediate structure is molded, the molding pressure reaches about 100 atm. When the mold is clamped, stress may act to reduce this step. As a result, a crack occurs in the capacitor or solder, and problems such as breakage of the joint between the capacitor and the lead frame, deterioration of the capacitor, and failure may occur.

  According to the first embodiment, since the rigidity of the conductor member 80 is lower than that of the capacitor 30, the L-shaped portion 81 of the conductor member 80 is preferentially deformed when stress is applied particularly in the horizontal direction. The stress concentration on is relaxed. Further, by disposing the capacitor 30 so that the external electrodes 32 and 33 face each other vertically, the strength of the capacitor 30 can be improved against stress acting in the vertical direction as compared with the comparative example.

In this way, breakage of the joint between the capacitor 30 and the lead frame 10, deterioration of the capacitor 30, failure, and the like are prevented. In addition, it is possible to prevent a failure or the like during transfer of the intermediate structure of the power semiconductor device 100 and improve the yield. Furthermore, when the power semiconductor device 100 is molded, the generation of cracks in the capacitor or solder is suppressed, and the yield can be further improved.
These effects can be obtained more remarkably by not only the rigidity of the conductor member 80 being lower than that of the capacitor 30 but also being lower than that of the conductive bonding materials 71 to 73.

  In addition, the mounting area of the capacitor 30 is the sum of the bonding area of the lower external electrode 32 of the capacitor 30 and the bonding area of the bonded portion 84 of the conductor member 80, and the bonded portion 84 as in the first embodiment. By making this area smaller than the area of the lower external electrode 32, the mounting area of the capacitor 30 can be reduced as compared with the comparative example, and the power semiconductor device 100 can be downsized in the horizontal direction.

Further, in the comparative example, when the lead frame terminal interval is reduced in order to obtain a high mounting density, the solder scoops up the external electrodes of the capacitor, and the external electrodes may be short-circuited, which may deteriorate the yield.
In the first embodiment, even when the distance between the power terminals 11 and 12 is reduced, the external electrodes 32 and 33 due to solder rising are provided by providing the conductor member 80 that bridges the power terminals 3 and 3 in a three-dimensional manner. A short circuit between is prevented.

In the comparative example, when the power semiconductor element is formed of a wide gap semiconductor material, the withstand voltage and allowable current density of the element are increased, so that the ambient temperature becomes higher depending on the use mode, and stress concentration occurs in the capacitor. There is a fear. Therefore, it is necessary to increase the heat dissipation area in the power semiconductor device, and it may be difficult to reduce the size.
On the other hand, in the first embodiment, since the stress concentration is reduced by providing the conductor member 80 as described above, the apparatus 100 even when the power semiconductor elements 21 to 23 using the wide gap semiconductor material are mounted. Can be reduced in size.

Embodiment 2. FIG.
FIG. 3 is a cross-sectional view corresponding to FIG. 2, showing a power semiconductor device according to Embodiment 2 of the present invention.
The second embodiment is different from the first embodiment (power terminal 12) in the structure of the power terminal 112 to which the joined portion 84 of the conductor member 80 is joined. Specifically, the power terminal 112 has a recess 112 a that receives the conductor member 80. The recess 112a includes a bottom surface 112b and a side wall 112c. The bonded portion 84 is bonded onto the bottom surface 112b of the recess 112a.

  According to the second embodiment, when the conductor member 80 is bonded to the power terminal 12 using the conductive bonding material 73, there is an advantage that the horizontal position shift of the conductor member 80 can be controlled by the recess 112a. Further, when the conductor member 80 is joined to the upper external electrode 33 and the power terminal 12 of the capacitor 30, there is an advantage that the inclination in the rear side and front side direction (in the yz plane in the drawing) of FIG. is there. Furthermore, after molding, the insulator 50 is filled in the recess 112a, and the bonded portion 84 is covered and fixed by the insulator 50, so that the fixing strength of the conductor member 80 can be increased.

FIG. 4 is a perspective view showing a part of a conductor member of a power semiconductor device according to a first modification of the second embodiment.
In the first modification, the structure of the bonded portion 184 of the conductor member 180 is different from that shown in FIG. 3 (the bonded portion 84 of the conductor member 80). Specifically, in FIG. 3, the bonded portion 84 protrudes only in one horizontal direction (+ x direction) with respect to the second plate portion 83 to form an L shape. The joint portion 184 protrudes on both sides in the horizontal direction with respect to the second plate portion 183 to form a T shape. In the first modification, the shape of the power terminal 112 may be the same as that in FIG. According to the first modification, the effect obtained by the second embodiment can be enhanced.

5A is a perspective view and FIG. 5B is a cross-sectional view illustrating a part of a conductor member of a power semiconductor device according to a second modification of the second embodiment.
In the second modification, the structures of the joined portion 284 and the power terminal 212 of the conductor member 280 are different from those shown in FIG. 3 (the joined portion 84 of the conductor member 80 and the power terminal 112). Specifically, as in the first modification, the bonded portion 284 includes a protruding portion 285 that protrudes on both sides in the horizontal direction with respect to the second plate portion 283 to form a T-shape, and a horizontal direction (x Direction) and a bifurcated portion 286 extending vertically from both ends. Next, the power terminal 212 has recesses 212 a and 212 b that receive the bifurcated portion 286 of the conductor member 280. According to the first modification, the effect obtained by the second embodiment can be enhanced.

Embodiment 3 FIG.
FIG. 6 is a perspective view showing a part of the power semiconductor device according to the third embodiment of the present invention.
The third embodiment is applied to a configuration in which two or more capacitors are mounted on the power terminal 11 and the capacitors are connected in parallel. The capacitance of two or more capacitors may be the same or different.

  In FIG. 6, two capacitors 331 and 332 (corresponding to the capacitor 30 of the first embodiment) are provided as an example. The conductor member 380 (corresponding to the conductor member 80 of the first embodiment) has an L-shaped portion 381 and a joined portion 384 as in the first and second embodiments. The conductor member 380 further includes a plate-like connection terminal portion 385 that connects the capacitors 331 and 332 in parallel. The connection terminal portion 385 is connected to the end portion of the L-shaped portion 381 extending along the first horizontal direction (x direction in the drawing), and is in the second horizontal direction (y direction) perpendicular to the first horizontal direction. It extends along. The connection terminal portion 385 is bonded to the external electrode on the upper side of the capacitors 331 and 332 using a conductive bonding material (not shown).

  According to the third embodiment, in the configuration in which two or more capacitors are mounted on the power terminal 11, the advantages described in the first embodiment can be obtained.

  Although the present invention has been described with reference to the first to third embodiments, the present invention is not limited to these embodiments. Various modifications and improvements may be added to the embodiment. The features described in each embodiment may be freely combined.

  For example, in the above-described embodiment, a multilayer ceramic capacitor is connected between the terminals 11 and 12 of the lead frame 10, but the present invention is not limited to this, and a configuration in which a chip-type electronic component is provided between the terminals 11 and 12 by bonding. The present invention can be applied.

  In the above embodiment, the lower external electrode 32 and the power terminal 11, the upper external electrode 33 and the conductor member 80, and the conductor member 80 and the power terminal 12 are bonded using the conductive bonding materials 71 to 73, respectively. However, the effect of the above embodiment can be obtained even when ultrasonic bonding or welding is performed.

DESCRIPTION OF SYMBOLS 10 Lead frame, 11-15 Power terminal, 16-18 Signal terminal, 21-23 Power semiconductor element, 30 Multilayer ceramic capacitor, 32, 33 External electrode, 50 Insulator, 61-66 Wiring member, 71-73 Conductive joining Material, 80 conductor member, 81 L-shaped part, 84 joined part, 100 power semiconductor device

Claims (7)

A lead frame including a first electrode and a second electrode separated from each other;
A power semiconductor element mounted on the lead frame;
A chip-type electronic component disposed on the first electrode and provided with external electrodes at both ends;
A part of the lead frame, the power semiconductor element and an insulator for sealing the chip-type electronic component;
One external electrode of the chip-type electronic component is bonded to the first electrode,
The other external electrode of the chip-type electronic component is joined to the second electrode via a conductor member having an L-shaped part,
The power semiconductor device, wherein the conductor member has lower rigidity than the chip-type electronic component. The second electrode has a recess for receiving the conductor member,
The power semiconductor device according to claim 1. Two or more chip-type electronic components are provided,
The conductor member has a connection terminal portion for connecting the two or more chip-type electronic components in parallel.
The power semiconductor device according to claim 1 or 2. One external electrode and the first electrode of the chip-type electronic component, the other external electrode of the chip-type electronic component and the conductor member, and the conductor member and the second electrode are each more rigid than the conductor member. Bonded using high conductive bonding material, ultrasonic bonded or welded,
The power semiconductor device according to claim 1. The conductor member has a joined portion that extends in a horizontal direction D from one end of the L-shaped portion and is joined to the second electrode;
The height H of the conductor member has a size of 2 to 5 times the predetermined distance D,
The power semiconductor device according to claim 1. The conductor member is a single conductor plate,
The power semiconductor device according to claim 1. The chip-type electronic component is a multilayer ceramic capacitor,
The power semiconductor device according to claim 1.

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