JPH0758282A - Power semiconductor module and inverter device for vehicle - Google Patents

Abstract

PURPOSE:To restrain a mounting board from being stripped at the bonding part of a case, to prevent the degradation of dielectric strength characteristics or element characteristics and to easily change a high-reliability and high-breakdown-strehgth semiconductor device into a module by a method wherein the coating of a rubberlike synthetic resin is formed on the inner face of the bonding part of the case to the mounting board. CONSTITUTION:In a power semiconductor module, a metal plate 105 to which a semiconductor element 104 and an electrode terminal 106 have been attached is stacked on a mounting board 101 via an insulating board 102, a synthetic-resin case 109 is bonded to a peripheral bonding part 113 on the mounting board 101 by an adhensive 108, and the case is sealed. After that, a gellike synthetic resin layer 111 and a rigid synthetic-resin layer 112 are formed at the inside, and in addition, a rubberlike synthetic resin layer 110 is formed the inner face of the bonding part 113 of the case 109 up to the edge of the metal plate 105. Thereby, it is possible to restrain the case 109 from being stripped from the mounting board 101 and to eliminate the creeping of moisture. In addition, since the rubberlike synthetic-resin layer 110 is rich in elasticity, there is no fear that a crack is caused.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power semiconductor element having a synthetic resin sealing structure with an insulating container, and more particularly to a power semiconductor module suitable for a vehicle inverter device having a relatively high voltage.

[0002]

2. Description of the Related Art Power semiconductors such as diodes, transistors, IGBTs (insulated gate bipolar transistors) and GTOs (gate turn-off thyristors) used in relatively high voltage and high power devices such as inverters for railway vehicles. As the element, a flat element has conventionally been the mainstream, but in recent years, a so-called power semiconductor module that is encapsulated in an insulating container to be modularized has been proposed and used, and an example thereof is being used. JP-A-60-
It can be found in JP-A-178650, JP-A-61-218151, JP-A-63-143850 and the like.

A conventional example of this power semiconductor module will be described with reference to FIG. 3. Usually, a module mounting substrate 203 made of a copper plate is provided, to which a semiconductor element 207 such as a diode is brazed via a plate made of molybdenum or the like. A conductive portion 201 made of a copper plate or the like is brazed and joined via an insulating plate 202 made of ceramics such as alumina or AlN (aluminum nitride), and this is sealed with a case 204 made of synthetic resin.

The case 204 is attached to the peripheral portion of the mounting substrate 203 by adhesion, and a gel-like synthetic resin 205 is enclosed inside so as to cover the current-carrying portion 201. Further, the current-carrying part 201 is provided with an electrode terminal, which allows external connection to necessary parts of the current-carrying part 201.

As described above, as the semiconductor element 207, an arbitrary element such as a diode is mounted as necessary. Above all, the IGBT is a voltage control element, so that it is easy to control and has a large current capacity. It is widely used because it is easy to obtain a large one and can operate at a high frequency.

[0006]

The above-mentioned prior art cannot be said to give sufficient consideration to modularization of a high breakdown voltage semiconductor element, and has a problem in providing high breakdown voltage and high reliability. For example, when applied to an inverter device for railway vehicles, etc., the power supply voltage is 600 V or 1500
Since it is a high voltage such as V, an effective voltage of 5400V withstand voltage is required between the current-carrying part of the module and the mounting substrate with high reliability such as humidity resistance.

However, in the above-mentioned conventional technique, as described below, it is difficult to sufficiently cope with both high withstand voltage characteristics and high reliability. That is, first,
In the technique of Japanese Patent Laid-Open No. 178650, the adhesive portion of the case 204 to the mounting substrate 203 is easily peeled off due to an increase in internal pressure due to the temperature rise of the element, and the adhesiveness of the gel synthetic resin 205 to the insulating plate 202 is poor. As a result, moisture penetrates, passes through the interface between the mounting substrate 203 and the gel-like synthetic resin 205, reaches the withstand voltage holding portion 206 on the surface of the insulating plate 202, and further reaches the semiconductor element 207 to reach the insulation characteristic and the element characteristic. Deterioration is likely to occur, and thus it is difficult to provide sufficient withstand voltage characteristics and reliability.

On the other hand, in the technique described in Japanese Patent Laid-Open No. 61-218151, a hard synthetic resin is filled between the insulating substrate and the mounting substrate and the case. Therefore, according to this technique, the mounting substrate is Although the problem of peeling the case from the case is reduced, this filled hard synthetic resin is likely to crack at the corners of the case, and discharge will occur at this crack part, and also deterioration of insulation characteristics is avoided. There was a problem that I could not.

An object of the present invention is to provide a power semiconductor module using a synthetic resin mold which has the necessary high withstand voltage characteristics and can easily have sufficiently high reliability. Another object of the present invention is to provide a highly reliable vehicle inverter device by using the above power semiconductor module.

[0010]

SUMMARY OF THE INVENTION The above-mentioned object is to energize a current-carrying portion, to which a semiconductor element and an electrode terminal are attached, by stacking it on an attachment substrate via an insulating substrate and adhering a case to the periphery of the attachment substrate. This is achieved by providing a rubber-like synthetic resin coating on the inner surface of the bonding portion of the case to the mounting substrate in the power semiconductor module of the type in which the parts are sealed.

Further, the above object is achieved by providing a rubber-like synthetic resin coating on the creeping surface extending from the peripheral portion of the mounting substrate to the peripheral portion of the insulating substrate to at least the peripheral portion of the conducting portion. .

[0012]

Since the rubber-like synthetic resin provided on the surface extending from the peripheral portion of the mounting substrate to the peripheral end face of the insulating substrate to at least the peripheral end face of the conducting portion covers the inner surface of the adhesive portion of the case to the mounting substrate. , It works to suppress peeling in this part. Therefore, there is no fear that the reliability may decrease due to the peeling of the case.

Further, since this rubber-like synthetic resin is rich in elasticity, there is no fear of cracking even at the corners of the case, and furthermore, it adheres surely to the surface of the insulating substrate, so that the pressure resistance at this part is high. There is no fear of characteristic deterioration. Therefore, it is possible to reliably obtain a highly reliable power semiconductor module having a high breakdown voltage.

Further, according to the present invention, by encapsulating the gel-like synthetic resin so as to cover the surface of the semiconductor element inside the module, the connecting portion such as the bonding wire with the semiconductor element is heated by the synthetic resin for sealing. Since it is possible to eliminate the risk of stress being applied, there is no risk of peeling at the wire bonding portion, and corrosion of the wire is less likely to occur, further improving reliability.

Further, at this time, by setting the creepage distance from the current-carrying portion in the dielectric strength holding portion on the surface of the insulating substrate covered with the rubber-like synthetic resin to the mounting substrate to be at least 2 mm, insulation of an effective voltage of 5400 V or more is obtained. Proof strength can be easily imparted.

[0016]

The power semiconductor module according to the present invention will be described in detail below with reference to the embodiments shown in the drawings. 1 and 2 show an embodiment in which the power semiconductor module according to the present invention is implemented as a diode. FIG. 1 is a sectional view,
FIG. 2 is also a plan view of the inside, which is a cross section taken along the line AA ′ of FIG. 1. In these figures, 101 is a mounting substrate,
102 is an insulating substrate, 103 is a conducting part, 104 is a semiconductor element, 105 is a metal plate, 106 is an electrode terminal, and 107 is Al.
A wire, 108 is an adhesive, 109 is a synthetic resin case, 110 is a rubber-like synthetic resin layer, 111 is a gel-like synthetic resin layer, 112 is a hard synthetic resin layer, 113 is an adhesive portion, and 114 is a dielectric strength holding portion. Respectively.

The mounting substrate 101 is made of a material having a high thermal conductivity such as copper (Cu), and one surface of the mounting substrate 101 is covered with an insulating substrate 102 made of ceramics such as alumina or AlN (aluminum nitride). The current-carrying portion 103 is brazed and joined with a brazing material such as solder or silver solder.

The current-carrying portion 103 is a metal plate 105 made of a material such as copper, and the semiconductor element 1 brazed to the surface thereof.
04, and the electrode terminal 106. Then, between the semiconductor element 104 and the one electrode terminal 106,
Bonding is performed with a plurality of Al wires 107.
Therefore, as shown in the figure, the electrode terminal 1
06 is attached to the metal plate 105 via an insulator base. The reason why a plurality of Al wires 107 are used is to increase the current capacity.

As described above, FIG. 2 is a plan view of the inside, but the gel-like synthetic resin layer 111 is omitted here. Then, as is apparent from FIG. 2, in this embodiment, three semiconductor elements 104 are mounted to form a module having a large current capacity.

In this embodiment, the metal plate 105 is
In the figure, the upper surface is made trapezoidal, and the semiconductor element 104 is brazed to this trapezoidal portion, but this is not necessarily a necessary condition. Further, it goes without saying that a metal plate 105 joined to a molybdenum plate may be used as the metal plate 105.

The case 109 is, for example, PPS (polyphenylene sulfite) or PBT (polybutylene.
Mounting board 1 made of synthetic resin such as terephthalate)
The adhesive portion 108 is adhered to the adhesive portion 113 in the peripheral portion of 01. The case 109 is provided with a hole through which the electrode terminal 106 passes, and the electrode terminal 10 is inserted into this hole.
6 is attached to the mounting substrate 101 with the inserted state, and then
The portion of the electrode terminal 106 that is exposed to the outside is bent and molded into the state shown in the figure.

In this embodiment, after the case 109 has been bonded in this way, a rubber-like synthetic resin made of, for example, silicone rubber, a gel-like synthetic resin made of silicone gel, and an epoxy resin are provided inside. A hard synthetic resin such as a resin is sequentially injected, and a rubber-like synthetic resin layer 110, a gel-like synthetic resin layer 111, and a hard synthetic resin layer 112 are respectively provided to cover and seal necessary parts.

The encapsulation of these synthetic resins is carried out by using an injecting device which controls the injected resin amount to an appropriate amount while detecting it by, for example, light or sound waves. First, a rubber-like synthetic resin is injected to form a rubber-like synthetic resin layer 110, and the mounting substrate 101
The adhesion portion 113 between the case 109 and the case 109 is covered with the withstand voltage holding portion 114 on the surface of the insulating substrate 102.

Next, a gel-like synthetic resin is injected onto the rubber-like synthetic resin layer 110 to form a gel-like synthetic resin layer 111 so that the semiconductor element 104, the wire 107, and the electrode terminal 106 are covered. To do. Then, after that, an epoxy resin is injected and cured to form a hard synthetic resin layer 112, fill the remaining space, and fix the electrode terminal 106.

FIG. 4 is an enlarged view showing the filled state of the rubber-like synthetic resin layer 110 by enlarging the vicinity of the withstand voltage holding portion 114 of the insulating substrate 102. The withstand voltage in this embodiment is the same as that of the conducting portion 103. It depends on the insulation distance from the mounting substrate 101, but at this time, the insulation distance is minimized in the portion directly below the current-carrying portion 103.

However, the insulating substrate 10 is provided in this portion.
Since there are two, by setting the thickness to, for example, 0.635 mm, it is possible to easily obtain an effective voltage of 10,000 V or more as the withstand voltage in this portion.

On the other hand, in this embodiment, the creeping distance between the current-carrying part 103 and the mounting substrate 101 is a part to be taken into consideration in order to obtain the necessary withstand voltage. If this creepage distance is L, this is the sum of the length L1 of the end portion of the insulating substrate 102 exposed from the end portion of the conducting portion 103 and the thickness L2 thereof, that is, L =
It becomes L1 + L2.

In this embodiment, since the rubber-like synthetic resin layer 110 is covered here, when the material is silicone rubber as described above, the creeping distance L
As a result, by setting 2 mm or more, the effective voltage 54
A withstand voltage of 00 V or higher can be stably obtained. Therefore, as described above, when the thickness L2 of the insulating substrate 102 is 0.635 mm, the length L1 is 1.36.
It should be done so that 5 mm or more is given.

Further, in this embodiment, as is clear from FIGS. 1, 2 and 4, the rubber-like synthetic resin layer 110.
Is also provided so as to cover the case 109 and the adhesive portion 113 of the mounting substrate 101, and since the adhesive strength is high, the case due to temperature changes during the module assembly process or when the finished product is used. Even when the internal pressure of 109 changes, the adhesive portion 113 between the case 109 and the mounting substrate 101
There is almost no possibility that peeling will occur, and since the rubber-like synthetic resin layer 110 will not crack even when peeling a little, there is no risk of water intrusion, and therefore,
Since the moisture resistance is sufficiently maintained, the insulation characteristics and element characteristics are not deteriorated, and high reliability can be reliably obtained.

On the other hand, in this embodiment, the rubber-like synthetic resin layer 110 is provided only in the peripheral portion of the metal plate 105,
It is not applied to the surface of the semiconductor element 104. Therefore, even if stress is generated in the rubber-like synthetic resin layer 110 when the temperature changes, stress is not applied to the wire 107, and therefore the risk of disconnection failure due to peeling of the wire can be sufficiently eliminated. it can.

For this purpose, it is necessary to strictly control the injection amount of the rubber-like synthetic resin, but according to this embodiment, since the metal plate 105 is provided, its thickness is
For example, if the distance is set to 1 mm or more, the position of the semiconductor element 104 and the mounting position of the electrode terminal 106 to the metal plate 105 can be set to a position sufficiently higher than the insulating substrate 102. There is no problem even if the thickness fluctuates a little, and therefore strict control of the injection amount of the rubber-like synthetic resin is not required, and it is possible to obtain the desired performance even with an appropriate injection work. There is.

By the way, as the material of the rubber-like synthetic resin layer 110 in this embodiment, a silicone type synthetic resin may be used as described above, but a polyimide type synthetic resin may be used.

Further, in the above embodiment, the hard synthetic resin layer 112 is further enclosed on the gel synthetic resin layer 111, but the present invention can be implemented even if the hard synthetic resin layer 112 is omitted. It is possible.

Next, FIG. 5 shows another embodiment of the present invention.
In this embodiment, a so-called DBC (Direct Bonded Copper) substrate 102A in which a metal plate is previously brazed on the insulating substrate is used in place of the insulating substrate 102 and the metal plate 105 in the embodiment of FIGS. It was what I had.

As a result, in this embodiment, since the metal plate to which the semiconductor element 104 is brazed is not trapezoidal but has a flat shape and the thickness thereof is thin, the rubber is reduced. The cross-sectional shape of the synthetic resin layer 110 is molded as illustrated.

Next, FIGS. 6 and 7 show an embodiment in which the present invention is implemented as an IGBT power module.
Is a sectional view, and FIG. 7 is a plan view showing a section taken along the line BB ′. This embodiment is, for example, an IGBT power module suitable as a switching element of an inverter device. Therefore, as apparent from FIG.
One IGBT semiconductor element 104A and two diode semiconductor elements 104B are mounted. Here, the semiconductor element 104A is for a switching element, and the semiconductor element 104
B is for the flywheel diode.

Also, in this embodiment, the other structure is the same as that of the embodiment described with reference to FIGS. 1 and 2, and the rubber-like synthetic resin layer 110 is provided. Therefore, according to this embodiment, the module of the module is also provided. Even when the internal pressure of the case 109 changes due to temperature changes during the assembly process or when using the finished product, the adhesive portion 11 between the case 109 and the mounting substrate 101
There is almost no risk of peeling in No. 3, and even when peeling a little, there is no risk of cracks in the rubber-like synthetic resin layer 110, so there is no risk of water intrusion, and therefore moisture resistance is high. Since it is sufficiently held, there is no deterioration in insulation characteristics and element characteristics, and high reliability can be reliably obtained.

Next, FIGS. 8 and 9 show an embodiment in which a part of the embodiment described with reference to FIGS. 1 and 2 is modified, and FIG. 8 is a sectional view taken along the line CC ′. FIG. 9 is a plan view showing a cross section. The embodiment of FIGS. 8 and 9 differs from the embodiment of FIGS. 1 and 2 in that the range in which the rubber-like synthetic resin layer 110 is provided is not limited to the peripheral portion of the metal plate 105. As shown in the figure, only the point that the peripheral edge portion of the semiconductor element 104 extends to a part of the upper surface, and the rubber-like synthetic resin layer 110A is also provided there, the other configuration is as shown in FIG. This is the same as the embodiment of FIG.

The semiconductor element 104 is a diode element as described in the embodiments of FIGS. 1 and 2, and therefore has a planar termination region formed of a pn junction on its peripheral end face. The thickness of the planar termination region varies depending on the breakdown voltage of the element, but is usually around 1 mm, and the thickness of this region is 1000 mm.
The device withstands a device breakdown voltage of from V to 4000 V, and is therefore significantly affected by moisture and the like, and the breakdown voltage of the device is extremely likely to deteriorate.

However, in this embodiment, the rubber-like synthetic resin layer 110 extends from the planar termination region of the semiconductor element 104 to the upper surface thereof, and the rubber-like synthetic resin layer 110A is formed there. Therefore,
This planar termination region is sufficiently protected from intrusion of moisture and the like, and therefore, higher reliability can be obtained.

Next, FIG. 12 shows still another embodiment of the present invention. In the figure, reference numeral 120 is a partition member, and other structures are the same as those of the embodiment shown in FIGS.

The partition member 120 is made of, for example, a synthetic resin material of the same material as that of the case 109 so as to have a frame shape whose plan view seen from above is substantially the same as that of the metal plate 105. It is designed to partition the outside and inside of the peripheral part. The partition member 120 is placed on the metal plate 105, and the rubber-like synthetic resin is selectively injected into the outer side of the metal plate 105 to form the rubber-like synthetic resin layer 1.
By forming 10, it is adapted to be fixed in the module.

Then, after that, a gel-like synthetic resin is injected into the inside of the partition member 120 to cover the entire conducting portion including the semiconductor element 104 with the gel-like synthetic resin layer 111, and thereafter, the hard synthetic resin layer 112 is formed. Form it to complete the module.

According to this embodiment, the gel-like synthetic resin layer 1
Since the injection range of 11 can be limited, the total amount (volume) of the rubber-like synthetic resin layer 110 and the gel-like synthetic resin layer 111 having a large thermal expansion coefficient can be reduced, and as a result, the internal temperature rise due to the heat generation of the semiconductor element 104. The increase of the internal pressure at the time is suppressed, and the stress on the solder joint portion is relieved, so that the reliability is improved.

In this embodiment as well, similar to the embodiment of FIGS. 8 and 9, the rubber-like synthetic resin layer 110 may be provided up to the peripheral portion of the semiconductor element 104. Alternatively, the hard synthetic resin layer 112 may be omitted.

Incidentally, although not particularly mentioned in the above description, at least the surfaces of the mounting substrate 101 and the insulating substrate 102 and the inner surface of the case 109, which are in contact with the gel synthetic resin, are roughened. You may do it. In this case, the state of joining with the gel-like synthetic resin layer becomes good, and thus more excellent protection characteristics can be obtained.

Further, in the above-mentioned embodiment, the rubber-like synthetic resin layer 110 is provided up to the end face of the peripheral portion of the metal plate 105, but in the embodiment of the present invention, the mounting substrate 10 is used.
A rubber-like synthetic resin layer may be provided only on the inner surface of the joint portion 108 between the case 1 and the case 109, and the other portion may be covered with a hard synthetic resin. In the case of this embodiment, since the mechanical strength of the module is greatly improved, it can be made suitable for the vertical arrangement described later.

As is clear from the above description, according to the power semiconductor module of the present invention, stable high-voltage insulation characteristics and moisture resistance are obtained inside the module. It eliminates the need for an insulation structure outside of the element, such as with conventional flat elements, which simplifies the system configuration, simplifies assembly, and facilitates maintenance. To be For example, when the power semiconductor module of the present invention is applied to a vehicle inverter device, the pressure contact structure and the pressure contact assembly process required for the conventional flat element are not necessary.

Next, FIG. 11 is an embodiment showing the arrangement state when the power semiconductor module M according to the present invention is applied to a system such as an inverter device.
HS is a heat sink. In addition, 101 is a mounting substrate of the power semiconductor module M as mentioned above.
In a conventional power semiconductor module, the module mounting substrate is normally placed horizontally. Therefore, in this case, the bottom surface of the mounting substrate is arranged at a right angle to the direction of gravity.

Therefore, in the embodiment of FIG. 11, the mounting substrate 101 of the power semiconductor module M is, as shown in the figure.
However, it is fixed to the mounting surface of the vertical heat sink SM, and the bottom surface of the mounting substrate 101 is parallel to the direction of gravity.

When the bottom surface of the mounting substrate 101 is arranged in parallel with the direction of gravity as described above, in the module according to the prior art, the components inside the module such as the solder-bonded current-carrying parts are made of gel-like synthetic resin. Since it is only covered, the force due to gravity always acts on the solder joint portion as shear stress, and as a result, there is a possibility that cracks may occur at the joint portion due to creep of the solder, leading to a decrease in reliability.

On the other hand, in the case of the power semiconductor module M according to the present invention, as described above, the rubber-like synthetic resin layer 1 is used.
Since 10 is provided, the fixing action by this is obtained, and the components inside the module are sufficiently fixed. As a result, as a result, the generation of shear stress due to gravity in the current-carrying parts joined by soldering can be sufficiently suppressed, so that it is possible to maintain sufficiently high reliability even in the case of vertical arrangement, and therefore the power semiconductor according to the present invention. When the module is used, the vehicle inverter device can be sufficiently miniaturized by the vertical arrangement.

[0053]

As described above, according to the present invention,
Since the occurrence of peeling between the mounting substrate and the case where the case is bonded can be sufficiently suppressed, deterioration of dielectric strength characteristics and element characteristics due to moisture intrusion will not occur, and high-voltage semiconductor devices with high reliability can be easily manufactured. It can be modularized.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of a power semiconductor module according to the present invention.

FIG. 2 is a plan view of the inside as seen from the line AA ′ in FIG.

FIG. 3 is a sectional view showing a conventional example of a power semiconductor module.

FIG. 4 is a sectional view showing a part of an embodiment of the present invention in an enlarged manner.

FIG. 5 is a sectional view showing a second embodiment of the present invention.

FIG. 6 is a sectional view showing a third embodiment of the present invention.

FIG. 7 is a plan view of the inside viewed from the line BB ′ of FIG.

FIG. 8 is a sectional view showing a fourth embodiment of the present invention.

FIG. 9 is a plan view of the inside viewed from the line CC ′ in FIG. 8.

FIG. 10 is a sectional view showing a fifth embodiment of the present invention.

FIG. 11 is an explanatory diagram showing an example of an arrangement state of power semiconductor modules according to the present invention.

[Explanation of symbols]

 101 Mounting Substrate 102 Insulating Substrate 103 Conductor 104 Semiconductor Element 105 Metal Plate 106 Electrode Terminal 107 Wire 108 Adhesive 109 Case 110 Rubber-like Synthetic Resin Layer 111 Gel-like Synthetic Resin Layer 112 Hard Synthetic Resin

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yuji Wakizawa 7-1-1 Omika-cho, Hitachi-shi, Ibaraki Hitachi Ltd. Hitachi Research Laboratory

Claims (6)

[Claims] 1. A conductive element, to which a semiconductor element and an electrode terminal are attached, is laminated on an attachment substrate via an insulating substrate, and a synthetic resin case is adhered to the peripheral portion of the attachment substrate to seal the conduction portion. A power semiconductor module of a stopping type, wherein a rubber-like synthetic resin coating is provided on an inner surface of an adhesive portion of the case to the mounting substrate. 2. The creeping surface of the invention as set forth in claim 1, wherein the rubber-like synthetic resin coating extends from the peripheral portion of the mounting substrate through the peripheral end face of the insulating substrate to at least the peripheral end face of the conducting portion. A power semiconductor module, which is provided in. 3. In the invention of claim 1 or 2,
A power semiconductor module, wherein a gel-like synthetic resin is enclosed in the case so as to cover at least the surface of the semiconductor element of the energizing portion. 4. The power semiconductor module according to claim 2, wherein the coating of the rubber-like synthetic resin reaches at least the planar termination region of the semiconductor element. 5. The power semiconductor module according to claim 2, wherein the creeping surface has a length of at least 2 mm. 6. An inverter device for a vehicle, comprising the power semiconductor module according to any one of claims 1 to 5.