JP2019046839A - Power semiconductor module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a short-circuit breakdown due to creeping discharge even when the surface electrode area on an insulating substrate is enlarged and the creepage distance is reduced in order to ensure high insulation reliability while realizing a large capacity of a power semiconductor module. A power semiconductor module is provided. A power semiconductor module 100 has a power obtained by joining a first electrode 7-1 and a second electrode 7-2 on the front and back surfaces of the insulating substrate 2 and the first electrode 7-1. The insulating substrate 2 and the power semiconductor are disposed in a space formed by the semiconductor chip 1, the metal base 3 joined to the second electrode 7-2, the insulating case 5, and the metal base 3 and the insulating case 5. A side surface of the insulating substrate 2 that faces each other or the side surface of the insulating case 5 that faces the insulating substrate 2 and the side surface of the insulating substrate 2 are bonded with a hard resin 8. The hard resin 8 is characterized in that it covers a part of the portion where the insulating substrate 2 is exposed from the first electrode 7-1 and a part of the side surface of the insulating substrate 2. [Selection] Figure 1

Description

  The present invention relates to a high withstand voltage power semiconductor module that requires high insulation reliability.

  Power converters (converters or inverters) equipped with power semiconductor modules are widely used in various fields such as railways, automobiles, industries, and power / social infrastructure.

  Conventionally, as a technique for improving the reliability of resin sealing relating to a semiconductor device operating particularly at a high temperature, an insulating substrate on which a front electrode pattern and a back electrode pattern are formed and a semiconductor element bonded to the front electrode pattern are provided. In addition to sealing with a first sealing resin containing an epoxy resin or the like, a portion of the insulating substrate on which the front electrode pattern or the back electrode pattern is not formed and the first sealing resin are replaced with the first sealing resin. By covering the semiconductor device with a second sealing resin containing a silicone resin or the like having a smaller elastic modulus, the stress is relieved with the second sealing resin having a smaller elastic modulus during high-temperature operation, and the first There has been a technique for alleviating stress concentration at the end of the sealing resin (see, for example, Patent Document 1).

  Conventionally, as a technique for improving the insulation reliability of a resin-sealed inverter module, an inorganic substrate (insulating substrate) bonded on a base metal plate and an inorganic substrate so as to expose the peripheral portion of the inorganic substrate are exposed. The conductive foil (electrode) formed on the semiconductor foil and the semiconductor element mounted on the conductive foil are sealed with silicone gel, and the outer peripheral side portion of the conductive foil and the peripheral portion of the inorganic substrate are broken higher than the silicone gel. By covering the inverter module with a thermosetting resin coating with voltage, the electric field can be relaxed even if the creeping distance from the edge of the inorganic substrate to the conductor foil is short. There has been a technique for improving reliability and reducing the size and increasing the capacity (for example, see Patent Document 2).

JP 2013-16684 A JP 2004-14919 A

  Power semiconductor modules that handle high voltages are required to have high insulation reliability. The outer periphery of the power semiconductor module is insulated by the creeping surface of air / insulator, and the spatial distance and the creeping distance are determined by a standard (for example, IEC60664) so as not to cause a short circuit or discharge in a predetermined environment. In addition, it is difficult to secure insulation by increasing the spatial distance and creepage distance inside the module where power semiconductor chips, insulating substrates, bonding wires, etc. are mounted at high density. Is sealed with an insulating resin to insulate between the members.

  The insulating resin material that seals the inside of the module is roughly divided into two types: hard resin such as epoxy resin and soft resin such as silicone gel. For example, in a low-capacity and small-sized power semiconductor module with a rated current of about several tens of amperes, a hard resin is generally used as the insulating sealing resin. For example, the insulating sealing resin described in Patent Document 1 is used. This is considered to be the case. Hard resin-encapsulated power semiconductor modules are generally small in size, so even if distortion / stress occurs between the components inside the module due to the encapsulation of the hard resin, the distortion / stress is small. This is almost never a problem.

  On the other hand, in contrast to such hard resin-encapsulated power semiconductor modules, soft semiconductors such as silicone gel are used as insulating encapsulating resins in power semiconductor modules with large capacity (rated current of 100 amps or more) and large module size. For example, it is considered that the insulating sealing resin described in Patent Document 2 corresponds to this. If the inside of the module to which the power semiconductor chip, insulating substrate, bonding wire, etc. are bonded is sealed with a hard resin with high rigidity, a large strain or stress is generated between the members, causing mechanical damage to the internal members. In order to avoid this, a soft resin that is soft and absorbs and relaxes strain and stress between members may be used. The

  FIG. 5 shows the structure of a general power semiconductor module that is insulated and sealed with a soft resin. The power semiconductor module 500 includes a power semiconductor chip 1 such as an IGBT (Insulated Gate Bipolar Transistor) and a MOSFET (Metal-Oxide-Semiconductor Field Effect Transistor), and an insulating substrate. 2, a metal base 3, a bonding wire 4, an insulating case 5, and a silicone gel 6 which is an insulating sealing material and is a soft resin. The insulating substrate 2 has a surface electrode 7-1 and a back electrode 7-2 brazed to one surface (for example, the front surface) and the other surface (for example, the back surface), respectively, and the power semiconductor chip 1 is attached to the surface electrode 7-1. Are soldered together, and the back electrode 7-2 and the metal base 3 are soldered together. The power semiconductor chip 1 and the surface electrode 7-1 on the insulating substrate 2 are electrically connected to each other by a bonding wire 4. The insulating case 5 is fixed to the peripheral edge of the metal base 3 with an adhesive, and the silicone gel 6 is stored in the space formed by the metal base 3 and the insulating case 5 so that the front electrode 7-1 and the back surface The insulating substrate 2 with the electrode 7-2 and the power semiconductor chip 1 are sealed inside the space. Since the dielectric breakdown strength of the silicone gel is relatively small compared to the hard resin, and there is a risk of causing breakdown of the power semiconductor module and equipment using the same when an electric field strength exceeding it is applied to the silicone gel 6, Measures to avoid it are taken.

  The portion where the electric field concentrates in the power semiconductor module 500 is the end portion of the insulating substrate 2. When the electric field strength of the portion exceeds the dielectric breakdown electric field strength of the silicone gel 6, Then, local dielectric breakdown occurs, heat and gas are generated, and voids are formed in the soft silicone gel 6. The dielectric breakdown strength of the void is smaller than that of the insulating resin such as the silicone gel 6, and the local dielectric breakdown further occurs in the void portion, so that a new void is generated. These local breakdowns progress in a chain, and the discharge due to the breakdown in the silicone gel is caused by the metal base 3 (low potential part) from the end of the electrode on the insulating substrate 2 along the surface / side surface of the insulating substrate 2. Creeping discharge occurs until the power semiconductor module 500 is finally short-circuited. In order to avoid this, conventionally, the creeping discharge is ensured by securing a long creepage distance between the end of the insulating substrate 2 and the end of the surface electrode 7-1 (for example, securing about 1 mm to 2 mm). It was made the aspect which suppresses.

  However, the power semiconductor module 500 is required to have a high capacity and a large capacity. In order to increase the size of the power semiconductor chip 1 as the capacity increases, it is necessary to increase the size of the insulating substrate 2 on which the power semiconductor chip 1 is mounted. On the other hand, the package size of the power semiconductor module 500 is It is desirable to reduce the size as much as possible (or maintain the general-purpose current size without increasing the size). Therefore, by enlarging only the area of the electrodes 7-1 and 7-2 on the insulating substrate 2 without increasing the size of the insulating substrate 2, it is possible to mount the enlarged power semiconductor chip 1. Is required. However, if the area of the electrodes 7-1 and 7-2 is increased without changing the size of the insulating substrate 2, the creeping surface between the end portions of the insulating substrate 2 and the end portions of the electrodes 7-1 and 7-2. There was a problem that the distance was shortened and the insulation reliability was lowered.

  With respect to this problem, the technique described in Patent Document 2 coats a hard resin (resin coating 10) having a higher dielectric breakdown strength than the silicone gel 8 on the end portion of the surface electrode 1 where the electric field concentrates, whereby the silicone gel 8 is prevented, and even if the creeping distance is short, short-circuit breakdown due to creeping discharge is suppressed to ensure insulation reliability. However, in the technique of Patent Document 2, even if the dielectric breakdown of the silicone gel 8 at the lower end of the electrode 1 end can be prevented, the upper end of the electrode 1 end is in contact with the silicone gel 8, so that There was a problem that the gel 8 might break down and cause a short circuit breakdown due to creeping discharge.

  Therefore, in order to ensure high insulation reliability while realizing a large capacity of power semiconductor modules, even if the surface electrode area on the insulating substrate is enlarged and the creepage distance is reduced, short circuit breakdown due to creeping discharge is prevented. It is a problem to provide a power semiconductor module that enables the above.

  In order to solve the above problems, main features of the power semiconductor module of the present invention are as follows.

  That is, the power semiconductor module of the present invention includes at least one insulating substrate and a first surface fixed to the first surface of the insulating substrate and a second surface that is the surface opposite to the first surface. And a second electrode; a power semiconductor chip bonded to the first electrode of the insulating substrate; a metal base bonded to the second electrode of the insulating substrate; the insulating substrate; An insulating case that accommodates both the first electrode, the second electrode, and the power semiconductor chip; and a space formed by the metal base and the insulating case; and the insulating substrate and the first electrode A power semiconductor module having a silicone gel that seals both the electrode, the second electrode, and the power semiconductor chip, between the mutually facing side surfaces of the insulating substrate, and the At least one of a side surface of the insulating case facing the edge substrate and a side surface of the insulating substrate is bonded to each other with a hard resin, and the hard resin is the first surface of the insulating substrate, and One of a part exposed from the first electrode or a part of the second surface of the insulating substrate that is exposed from the second electrode, and a side surface of the insulating substrate It is characterized by covering a part of.

  According to the present invention, even when the creepage distance is reduced by increasing the area of the surface electrode on the insulating substrate in order to ensure high insulation reliability while realizing a large capacity of the power semiconductor module, a short circuit due to creeping discharge. A power semiconductor module that can prevent destruction can be provided.

It is a figure which shows the structure of the power semiconductor module which concerns on the 1st Embodiment (Example 1) of this invention. It is a figure which shows the structure of the power semiconductor module which concerns on the 2nd Embodiment (Example 2) of this invention. It is a manufacturing process flowchart (flowchart) which shows the manufacturing method of the power semiconductor module which concerns on the 2nd Embodiment (Example 2) of this invention. It is a figure which shows the structure of the power semiconductor module which concerns on the 3rd Embodiment (Example 3) of this invention. It is a figure which shows the structure of the conventional power semiconductor module.

  Hereinafter, an example of an embodiment of a power semiconductor module of the present invention will be described as each example with reference to the drawings. In addition, in each Example, the same code | symbol is used for the same component.

  FIG. 1 shows the configuration of a power semiconductor module according to the first embodiment (Example 1) of the present invention.

  As shown in the figure, the power semiconductor module 100 of this embodiment includes a power semiconductor chip 1, an insulating substrate 2, a metal base 3, a bonding wire 4, an insulating case 5, a silicone gel that is an insulating sealing material and is a soft resin. 6 and hard resin 8. Specifically, the power semiconductor module 100 is fixed to, for example, at least one insulating substrate 2 and a first surface of the insulating substrate 2 and a second surface that is the surface opposite to the first surface. The first electrode 7-1 and the second electrode 7-2, the power semiconductor chip 1 joined to the first electrode 7-1 of the insulating substrate 2, and the second electrode 7-2 of the insulating substrate 2 A metal base 3 bonded to each other, an insulating case 5 that accommodates the insulating substrate 2, the first electrode 7-1, the second electrode 7-2, and the power semiconductor chip 1, and the metal base 3 and the insulating case 5 And a silicone gel that seals the insulating substrate 2, the first electrode 7-1, the second electrode 7-2, and the power semiconductor chip 1 together. Is done. At least one of the side surfaces of the insulating substrate 2 facing each other and between the side surface of the insulating case 5 facing the insulating substrate 2 and the side surface of the insulating substrate 2 are bonded to each other with a hard resin. The hard resin is a part of the first surface (for example, the front surface) of the insulating substrate 2 that is exposed from the first electrode 7-1 or the second surface (for example, the back surface) of the insulating substrate 2. Thus, either one of the portions exposed from the second electrode 7-2 and a portion of the side surface of the insulating substrate 2 are covered.

  A surface electrode 7-1 and a back surface electrode 7-2 are brazed to the first surface and the second surface, respectively, on the insulating substrate 2, and the power semiconductor chip 1 is soldered onto the surface electrode 7-1. The back electrode 7-2 and the metal base 3 are soldered together. The power semiconductor chip 1 and the surface electrode 7-1 of the insulating substrate 2 are electrically connected to each other by a bonding wire 4. An insulating case 5 is fixed to the peripheral edge of the metal base 3 with an adhesive, and a silicone gel 6 is disposed inside a space formed by the metal base 3 and the insulating case 5 and is stored in the space. Thus, the insulating substrate 2 and the power semiconductor chip 1 with the front electrode 7-1 and the back electrode 7-2 are sealed inside the space. The side surface of the insulating substrate 2 and the side surface (inner wall surface) of the insulating case 5 are bonded to each other with a hard resin 8. For example, when two insulating substrates 2 are provided, the two insulating substrates 2 are mutually connected. Opposing side surfaces are joined to each other by the hard resin 8. The upper side of the hard resin is filled with the silicone gel 6. When dielectric breakdown occurs in the silicone gel 6 near the end of the surface electrode 7-1 of the insulating substrate 2, heat and gas are generated in the silicone gel, and there are voids in the silicone gel 6 that is a soft resin depending on the situation. Will occur. Since the dielectric breakdown strength of the void is low compared to the insulating resin, if the conventional technology, further dielectric breakdown occurs in the generated void, these dielectric breakdown are chained through the insulating substrate surface, and further through its side, The discharge in the silicone gel will proceed. When this discharge reaches the metal base 3, a short circuit breakage occurs. However, in the present invention, the structure is such that the hard resin 8 is necessarily interposed on the creeping discharge path between the end portion of the surface electrode 7-1 and the metal base 3, and is also seen in the dielectric breakdown of the silicone gel 6. In addition, since the discharge proceeding in a chain while generating voids does not occur in the hard resin 8, if there is a hard resin 8 such as a solid resin having a predetermined thickness, the discharge stops there, thereby preventing a short circuit failure. be able to. Here, the predetermined thickness refers to a solid having a dielectric breakdown strength of 40 kVrms / mm when a voltage of 10 kVrms is applied between the surface electrode (high potential portion) of the power semiconductor module 100 and the metal base 3 (low potential portion), for example. When resin is applied, the thickness is at least about 0.25 mm (10 kVrms / 40 kVrms / mm).

  According to the present embodiment, when the creepage distance is reduced by increasing the area of the surface electrode 7-1 on the insulating substrate 2 in order to ensure high insulation reliability while realizing an increase in capacity of the power semiconductor module 100. However, it is possible to provide the power semiconductor module 100 that can prevent the short-circuit breakdown due to creeping discharge.

  FIG. 2 shows a configuration of a power semiconductor module according to the second embodiment (Example 2) of the present invention.

  As shown in the figure, the power semiconductor module 200 of this example differs from that of Example 1 in that the silicone gel 6 is disposed above and below the hard resin 8 such as a solid resin, as compared with Example 1. Other configurations except for this point are the same as those in the first embodiment.

  When the space between the insulating substrate 2 and the metal base 3 is sealed with the hard resin 8 having a high viscosity as in the first embodiment, a gap is likely to be generated. The configuration of Example 1 is effective under conditions in which local dielectric breakdown (partial discharge) does not occur even when such voids are present and insulation reliability does not deteriorate. If not, another embodiment may be required. The configuration of the present embodiment is proposed in view of such a case, and a silicone gel 6 having low viscosity and high fluidity is disposed in the gap between the insulating substrate 2 and the metal base 3. Since the portion is sealed, the insulating resin can be filled without forming a gap in the portion.

  FIG. 3 shows a manufacturing process flowchart (flowchart) 300 corresponding to the manufacturing method of the power semiconductor module 200 in this embodiment. After the power semiconductor chip 1 is joined to the collector electrode on the surface electrode 7-1 of the insulating substrate 2 by soldering, the power semiconductor chip 1 and the emitter electrode / gate electrode on the surface electrode 7-1 of the insulating substrate 2 are bonded to the bonding wire. The back surface electrode 7-2 of the insulating substrate 2 and the metal base 3 are electrically connected to each other with solder. After the metal base 3 and the insulating case 5 are connected to each other with an adhesive, an amount of silicone gel 6 filling the space between the insulating substrate 2 and the metal base 3 is injected and cured, and then the side surface of the insulating substrate 2 and the insulating case Hard resin (thermosetting resin) 8 is injected between 5 and 5 and cured. When a plurality of insulating substrates 2 are used, a hard resin (thermosetting resin) 8 is injected and cured between the side surfaces of the insulating substrates 2 facing each other. A main terminal (not shown), which is a lead-out wiring to the outside of the module, and the surface electrode 7-1 of the insulating substrate 2 are joined to each other with solder, and the lid of the insulating case 5 is bonded to the side member of the insulating case 5 A space is formed by the metal base 3 and the insulating case 5. Finally, the silicone gel 6 is injected into the space and cured.

  According to the present embodiment, the capacity of the power semiconductor module 200 can be increased even under conditions where local insulation breakdown (partial discharge) is liable to occur if a gap exists between the insulating substrate 2 and the metal base 3. In order to ensure high insulation reliability, a power semiconductor module capable of preventing short-circuit breakdown due to creeping discharge even when the surface electrode 7-1 on the insulating substrate 2 is enlarged and the creeping distance is reduced. 200 can be provided.

  FIG. 4 shows the configuration of a power semiconductor module according to the third embodiment (Example 3) of the present invention.

  As shown in the figure, the power semiconductor module 400 of this example has a protrusion 9 on a part of the inner wall surface of the insulating case 5 as compared with Example 2, and the protrusion 9 and a part of the insulating substrate 2 are Although different from the second embodiment in that they are joined to each other by the hard resin 8, other configurations except for this point are common to the second embodiment. After the projection 9 and the hard resin 8 are bonded to each other, the silicone gel 6 is injected and cured. Here, the protrusion 2 may be provided with a slit penetrating between the upper part and the lower part of the protrusion 2. In that case, since there is a slit, the silicone gel 6 can be injected and arranged also below the insulating substrate 2 through the slit. In Example 2, the silicone gel 6 is injected / cured below the insulating substrate 2 before the hard resin 8 is applied / cured, and the silicone gel 6 is injected into the entire module after the hard resin 8 is applied / cured. -The injection / curing process of the silicone gel 6, such as curing, was required twice. On the other hand, in this embodiment, since the injection / curing process of the silicone gel 6 can be reduced to one time, the production of the power semiconductor module 400 becomes easier.

  According to the present embodiment, in order to ensure high insulation reliability while realizing a large capacity of the power semiconductor module 400, the area of the surface electrode 7-1 on the insulating substrate 2 is enlarged and the creepage distance is reduced. However, it is possible to provide the power semiconductor module 400 that can prevent short-circuit breakdown due to creeping discharge with a simpler manufacturing process.

DESCRIPTION OF SYMBOLS 1 Power semiconductor chip 2 Insulating substrate 3 Metal base board 4 Bonding wire 5 Insulating case 6 Silicone gel 7-1 Insulating substrate electrode (surface electrode)
7-2 Insulated substrate electrode (back electrode)
8 Hard resin 9 Case protrusion

Claims (6)

At least one insulating substrate;
A first electrode and a second electrode respectively fixed to a first surface of the insulating substrate and a second surface which is a surface opposite to the first surface;
A power semiconductor chip bonded to the first electrode of the insulating substrate;
A metal base bonded to the second electrode of the insulating substrate;
An insulating case for accommodating both the insulating substrate, the first electrode, the second electrode, and the power semiconductor chip;
A silicone gel is disposed in a space formed by the metal base and the insulating case and seals the insulating substrate, the first electrode, the second electrode, and the power semiconductor chip together. A power semiconductor module,
Between the mutually facing side surfaces of the insulating substrate, and at least one of the side surface of the insulating case and the side surface of the insulating substrate facing the insulating substrate is bonded to each other with a hard resin,
The hard resin is a part of the first surface of the insulating substrate that is exposed from the first electrode or the second surface of the insulating substrate from the second electrode. One of the exposed portions and a portion of the side surface of the insulating substrate are covered. The power semiconductor module according to claim 1,
A portion of the first surface of the insulating substrate exposed from the first electrode and a part of a side surface of the insulating substrate are covered with the silicone gel,
The second surface of the insulating substrate that is exposed from the second electrode and the other part of the side surface of the insulating substrate are covered with the hard resin,
When the first surface of the insulating substrate is the upper side and the second surface is the lower side, the upper side of the hard resin is in contact with the silicone gel, and the lower side of the hard resin is in contact with the metal base. Power semiconductor module characterized by The power semiconductor module according to claim 1,
Between the mutually opposing side surfaces of the insulating substrate are bonded to each other with the hard resin,
Between the sides facing each other of the insulating substrate,
A portion of the first surface of the insulating substrate that is exposed from the first electrode and a portion of the side surface of the insulating substrate are covered with the hard resin;
A portion of the second surface of the insulating substrate exposed from the second electrode and another portion of the side surface of the insulating substrate are covered with the silicone gel;
The power semiconductor module, wherein the upper and lower sides of the hard resin are in contact with the silicone gel when the first surface of the insulating substrate is the upper side and the second surface is the lower side. In the power semiconductor module according to claim 3,
Between the side surface of the insulating case facing the insulating substrate and the side surface of the insulating substrate are bonded to each other with the hard resin,
Between the side surface of the insulating case facing the insulating substrate and the side surface of the insulating substrate,
A portion of the first surface of the insulating substrate that is exposed from the first electrode and a portion of the side surface of the insulating substrate are covered with the hard resin;
A portion of the second surface of the insulating substrate exposed from the second electrode and another portion of the side surface of the insulating substrate are covered with the silicone gel;
When the first surface of the insulating substrate is the upper side and the second surface is the lower side, the upper and lower sides of the hard resin are in contact with the silicone gel,
The hard semiconductor is further in contact with the inner wall surface of the insulating case. In the power semiconductor module according to claim 3,
Between the side surface of the insulating case facing the insulating substrate and the side surface of the insulating substrate are indirectly bonded to each other with the hard resin,
A protrusion is formed on the inner wall surface of the insulating case, and the protrusion and a part of the first surface of the insulating substrate exposed from the first electrode are A power semiconductor module, wherein the side surface of the insulating case and the side surface of the insulating substrate facing the insulating substrate are bonded to each other by being bonded to each other with a hard resin. The power semiconductor module according to claim 5, wherein
The protrusion has a slit penetrating between an upper portion and a lower portion of the protrusion when the first surface of the insulating substrate is the upper side and the second surface is a lower side. module.

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