JPH07273276A - Connection structure of power element and snubber element and its mounting structure - Google Patents

Abstract

(57) [Abstract] [Purpose] To improve the surge voltage absorption effect of the snubber element in the connection structure of the power element and the snubber element, and to improve the heat dissipation in the mounting structure of the power element and the snubber element. And [Structure] By electrically connecting the snubber element and the power element, which are respectively provided on the two metal substrates 32 and 22, via the pads 35 and 28 at the shortest distance, the parasitic inductance of the wiring is reduced, Generates power elements by reducing the generation of radio noise to the outside and by inserting and mounting the integrated combination of both metal substrates 22 and 32 into the groove formed in the radiator. Not only the heat
In addition to effectively dissipating the heat generated by the snubber element, a large shield effect of radio noise is obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a connection structure between a power element, which is a semiconductor element for power control, and a snubber element and its mounting structure, and more particularly to a technique for shortening the connection wiring length and a technique for improving heat dissipation.

[0002]

2. Description of the Related Art As a conventional connection structure between a power device of this kind and a snubber device and its mounting structure, there is, for example, one as shown in FIG. That is, the figure shows the internal structure of a commercially available power module A, and the module main body 1 is formed from a metal plate 1A and a box-shaped plastic package 1B mounted on the upper surface of the metal plate 1A. The ceramic substrate 2 is installed on the upper surface of the metal plate 1A,
A semiconductor chip 3 as a power element is mounted on the upper surface of the ceramic substrate 2. An electrode pad 4 is mounted on the upper surface of the ceramic substrate 2, and the electrode pad 4 and the extraction electrode 5 mounted on the plastic package 1B are connected via a wire 6.

FIG. 10 shows a switching circuit constructed by connecting a snubber element on the snubber module B side to the power element of the power module A. In the power module A, the extraction electrodes 5 and 7 of both snubber modules B are leads. Connected via line 8. A power supply line 9, an output line 10, and a ground line 11 are connected to the extraction electrode 5 of the power module A, respectively.

The power module A and the snubber module B thus connected are both fixedly mounted on the radiator 12 and mounted.

[0005]

However, in such a conventional connecting structure of the power element and the snubber element, the power element of the power module A and the snubber element of the snubber module B are the inner wire 6 and the outer lead. They are connected via the line 8, which causes the following problems.

That is, since the power element and the snubber element are provided in the separate modules A and B, the wiring length consisting of the wire 6 and the lead wire 8 for connecting them becomes long. Especially when a large capacity switching circuit is configured, the power module A and the snubber module B are
As a result of making both shapes larger, the wiring length of the wire 6 and the lead wire 8 becomes longer.

When the wiring length is increased in this way, the parasitic inductance of the wiring becomes a load on the power element, and the surge voltage generated by this increases as the switching current of the switching circuit increases. The snubber element itself is originally used for the purpose of absorbing this surge voltage, but if the power element and the snubber element are connected with a long wiring length having parasitic inductance as described above, the effect of the snubber element will not be sufficient. Can't get to.

Further, in the conventional mounting structure of the power element and the snubber element on the radiator, since the modules A and B provided with both elements are exposed and mounted on the upper surface of the radiator 12, There is a problem in that the contact area between each of the modules A and B and the radiator 12 is small, resulting in poor heat dissipation. Therefore,
In view of the above conventional problems, the present invention improves the surge voltage absorption effect of the snubber element by shortening the wiring length connecting the power element and the snubber element in the connection structure of the power element and the snubber element. The purpose is to reduce the size.

Another object of the present invention is to improve heat dissipation in the mounting structure of the power element and the snubber element.

[0010]

Therefore, according to the first aspect of the present invention, a substrate on which a power element is mounted and a substrate on which a snubber element is mounted are provided, and both substrates are integrated by abutting their element mounting surfaces. The power element and the snubber element are connected to each other to electrically connect the elements of both substrates to each other to form a connection structure of the snubber element.

According to a second aspect of the present invention, a wiring pattern is formed on the substrate on which the power element is mounted, and one end portion of a beam lead for external extraction is joined to the wiring pattern. The other end of the lead is projected from one end of the substrate. According to a third aspect of the present invention, a pad serving as a connecting electrode is mounted on each coupling surface of the board on which the power element is mounted and the board on which the snubber element is mounted.

According to a fourth aspect of the present invention, a spacer for preventing excessive pressure or impact from being applied to the pads on the mutual coupling surfaces of the substrate on which the power element is mounted and the substrate on which the snubber element is mounted. Is installed. According to a fifth aspect of the present invention, the integrally combined product of both the substrates according to the first aspect is inserted and mounted in a groove formed in the radiator.

According to a sixth aspect of the present invention, the beam lead is projected from the upper surface of the radiator. Claim 7
In the invention described above, a terminal plate is attached to a groove forming position on the upper surface of the radiator, a slit is formed in the terminal plate, and the beam lead protruding from the upper surface of the radiator is passed through the slit. The tip portion of the beam lead is fixedly attached to the terminal plate.

According to an eighth aspect of the invention, the slit is
It is surrounded by a magnetic material that absorbs high frequency surges.

[0015]

In the invention described in claim 1, since the snubber element and the power element respectively provided on the two substrates are electrically connected to each other at the shortest distance, the wiring length becomes extremely short, and the parasitic inductance of the wiring Can be reduced. As a result, the surge voltage generated by switching is effectively absorbed by the snubber circuit formed of the snubber element on the one substrate side, and the generation of radio noise to the outside can be reduced.

Further, it is possible to reduce the size of the circuit including the power element and the snubber element. According to the second aspect of the present invention, the beam lead for externally drawing out the integrated combined product of both substrates is easily formed. In the invention according to claim 3, the elements on both substrates can be easily electrically connected to each other by the pads serving as the connecting electrodes.

In the invention according to claim 4, it is possible to prevent excessive pressure or impact from being applied to the pad. In the invention of claim 5, since the integrated combination of both boards is inserted and mounted in the groove formed in the radiator, the whole of both boards comes into contact with the radiator, and the power element is generated. Not only the generated heat but also the heat generated in the snubber element can be effectively dissipated. Further, in the state of being inserted and mounted in the radiator, the circuit of each substrate is substantially surrounded by the radiator, so that a large shield effect of radio noise can be obtained.

In the inventions according to claims 6 to 8, since the beam lead penetrates through the magnetic body provided on the terminal plate, the radio noise is absorbed by the magnetic body, and the radio noise is radiated to the outside. It can be suppressed as much as possible.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to the accompanying drawings. First, in the connection structure of the power element and the snubber element according to the first aspect of the invention, a board on which the power element is mounted and a board on which the snubber element is mounted are provided, and both boards are connected to each other. This is a structure in which the element mounting surfaces are butted and integrally coupled.

A first embodiment of the connection structure between the power element and the snubber element according to the first aspect of the present invention will be described with reference to FIG. On the side of the substrate on which the power element is mounted, a metal substrate 22 formed by laminating a ceramic substrate 21 on the upper surface of a metal plate 20 made of aluminum, copper, or the like is provided. 23 and the flywheel diode chip 24 are bonded together. A wiring pattern 25 is formed on the ceramic substrate 21, and the wiring pattern 25 is formed.
The wire 26 is bonded to a predetermined position of.
Further, one end of a beam lead 27 for external drawing is bonded to the wiring pattern 25 by a method such as thermocompression bonding, and the other end of the beam lead 27 is projected from one end of the metal substrate 22. .

Further, pads 28 serving as connecting electrodes to the metal substrate side on which a snubber element, which will be described later, is mounted are mounted on the upper surfaces of the wiring patterns 25 at both ends of the ceramic substrate 21. Further, spacers 29 are attached to the upper surfaces of the four corners of the ceramic substrate 21 so as not to apply excessive pressure or impact to the pads 28, respectively.

Next, on the substrate side on which the snubber element is mounted, there is provided a metal substrate 32 formed by laminating a metal plate 31 made of aluminum, copper or the like on the upper surface of the ceramic substrate 30, and the upper surface of the metal substrate 32. Is provided with a capacitor 33 formed of a semiconductor element and a resistor 34 formed by screen printing as a snubber element, and a snubber circuit including a snubber element of a capacitor 33 (C) and a resistor 34 (R) is formed. ing. Further, at the upper surface positions of both ends of the metal substrate 32, there are provided electrodes for connection with the side of the metal substrate 22 on which the power element is mounted, and the pads 28 are formed.
Pads 35 that are connected to each other by thermocompression bonding or the like are mounted.

The thermocompression-bonding surfaces of the pads 28 and 35 with the mating side and the thermocompression-bonding surfaces of the beam lead 27 and the wiring pattern 25 with the mating side have Au surfaces via a buffer metal such as Ni or Ti. It is formed by. The metal substrate 22 on which the power element of such a configuration is mounted and the metal substrate 32 on which the snubber element is mounted are overlapped with the surfaces on the sides on which the pads 28 and 35 are mounted facing each other, and pressure-bonded. As shown in FIG. 1 (B), they are integrally connected.
In this case, the pads 28 and 35 of the metal board 22 on which the power element is mounted and the pads 28 and 35 of the metal board 32 on which the snubber element is mounted are connected to each other, and the elements of both boards 22 and 32 are electrically connected to each other.

Next, in the connection structure of the power element and the snubber element according to the fifth aspect of the present invention, the integrated combination of the metal substrates 22 and 32 is inserted and mounted in the groove formed in the radiator. It is a composition. That is, as shown in FIG. 2, the integrally combined product constructed as described above is inserted and mounted in the groove 37 formed on the radiator 26 and opened on the upper surface of the radiator 36. In this case, the metal substrate 22 and the metal substrate 3
The gap between the two may be filled with a silicon resin material or the like to improve the reliability of the power element and the snubber element.

The beam lead 27 provided on the metal substrate 22 on the power element side is projected from the upper surface of the radiator 36. Next, as shown in FIG.
The terminal plate 38 is attached as shown in FIG. A slit 39 is formed in the terminal plate 38, the beam lead 27 protruding from the upper surface of the radiator 36 is passed through the slit 39, and the tip end of the beam lead 27 is at the terminal plate 38.
It is bent to the upper surface side and fixedly attached to the terminal plate 38 by a screw terminal 40. The screw terminal 39 is used as a terminal for external wiring connection. In addition, the slit 39,
Surrounded by a ferrite material 41 which is a magnetic material,
The function of absorbing the high frequency surge generated in the switching circuit composed of the power element and the snubber element is exhibited.

Here, a specific structure of the snubber circuit formed of the snubber element formed on the metal substrate 32 and a manufacturing method thereof will be described. Figure 4 shows the snubber circuit.
There is something like. For example, as shown in FIG. 3A, a general individual high withstand voltage capacitor may be used in a case where only a single capacitor is used. Since the heat generation is accompanied by heat generation, heat dissipation must be taken into consideration, and in order to avoid the influence of self-resonance, some measures must be taken to lower Q, etc. Further, as shown in FIG. 3B, a Q dump resistor is provided externally or is integrated with other elements to form a module.

Therefore, in this embodiment, a capacitor forming a snubber element is formed on a Si semiconductor substrate to solve the above-mentioned heat dissipation problem and to achieve miniaturization. That is, FIG. 5 shows a cross section of the Si semiconductor substrate on which the snubber capacitor is formed. N ⁺⁺ high-concentration impurity layers 51 and 52 are formed on the front and back of the N ⁺ type Si semiconductor substrate 50, and a dielectric insulator layer 53 such as SiO ₂ or Si ₃ N ₄ is formed on the surface thereof. Cr layers 54 and 56 and Au layers 55 and 57 are continuously formed on the front and back of No. 50 in the order of numbers on the front and back surfaces. Next, the Si substrate 50 is bonded to the wiring electrode pad 58 of Al or Au formed in advance on the metal substrate 32 by a thermocompression bonding method or the like. Next, the Au layer 55 and the electrode pad 59 are connected by an Au ribbon 60 by a thermocompression bonding method or the like. Incidentally, the electrode pads 58 and 59
Are insulated from the metal substrate 32 by the alumina ceramic layer 51 and the like.

In this example, the space between the Cr layer 54 and the N ⁺⁺ layer 51 functions as a snubber capacitor, and the heat generated here is quickly transferred to the metal substrate 32 through the Si substrate 50 having a high heat conduction effect. . Since the metal substrate 32 is directly connected to the radiator 36 and a high heat radiation effect is obtained,
The size of the capacitor can be reduced if the required capacitance is obtained.

Further, in this example, the series resistance component Rs in the equivalent circuit of the snubber circuit shown in FIG. 6 can be increased by lowering the concentration of the Si substrate 50 and increasing the resistivity. As a result, the Q of the capacitor C can be reduced, and the effect of self-oscillation of the capacitor can be eliminated. That is, in the snubber circuit having the configuration of FIG. 4B, it is possible to individually form the resistors as the printing resistors on the metal substrate, but as in this example,
The parasitic resistance in the Si substrate may be effectively used.

Further, a circuit configuration having a diode in the snubber circuit as shown in FIG. 4C can be adopted. 7 and 8 show specific examples thereof. FIG. 7 shows an external resistor. Used as a P-type Si substrate 70, N ⁺ layer on the surface, to form a P ⁺ layer on the back surface. The capacitor is formed between the N ⁺ layer 72 and the metal electrode 75 sandwiching the SiO ₂ layer 74, and is connected to the P-type Si substrate 70 and the N-type Si substrate 70.
^A diode is formed on the junction surface between the ⁺ layers 72. P
^{The +} layer is for making ohmic contact with the metal electrode 76 described below. The junction withstand voltage of the diode is set higher than the maximum voltage of the power element used.
This is performed by appropriately selecting the impurity concentration of 0. That is, for example, in order to obtain a withstand voltage of 500 V, the P-type impurity concentration may be 5 × 10 ¹⁴ / cm ³ or less.

FIG. 8 shows an example in which all the elements forming the snubber circuit of the capacitor, the diode and the resistor are formed on the Si substrate. It forms a resistor connected in parallel with the diode around the diode, and it is possible to add an impurity diffusion layer 77 on the surface in addition to that of FIG. As described above, the breakdown voltage of the diode is the Si substrate 70.
It is determined by the impurity concentration of, and this also determines the resistivity of the resistance of the surrounding portion. For example, in order to obtain a diode breakdown voltage of 500 V, the impurity concentration of the substrate 70 should be 5 × 10 ¹⁴ / cm ^3.
In that case, the resistivity of the substrate 70 is about 3 Ωcm. For example, when the resistance value of the snubber resistor is 1Ω, and the thickness of the Si substrate 70 is 500 μm, the area of the P ⁺ layer 77 may be 2500 μm ² . The capacity of the capacitor is determined by the thickness of the SiO ₂ layer 74 and the area of the dielectric constant electrode 75. The SiO ₂ layer 74 is made of Si having a high dielectric constant as necessary.
₃ N ₄ , Ta ₂ O ₅ or the like or a laminate of these may be used. It is also possible to divide the above-mentioned capacitors and diodes into a plurality of chips as necessary in order to increase the electrostatic capacity and the current capacity, and connect each of them by the electrode pads 58 and 59 and the Au ribbon 60. By performing such chip division, the process yield at the time of manufacturing a capacitor and a diode can be improved.

Next, the operation and effect based on the configuration of FIGS. 1 to 3 will be described. Pads 35 and 2 are provided between the snubber element and the power element provided on the two metal substrates 32 and 22, respectively.
Since the wiring is electrically connected via the shortest distance via 8, the wiring length becomes extremely short, and the parasitic inductance of the wiring can be reduced. As a result, the surge voltage generated by switching is effectively absorbed by the snubber circuit including the snubber element on the metal substrate 32 side, and the generation of radio noise to the outside can be reduced.

In particular, conventionally, when a large-capacity switching circuit is constructed, the wiring length becomes long and the parasitic inductance increases, but in the above construction, there is no such concern. Further, according to the above configuration, it is possible to miniaturize the switching circuit including the power element and the snubber element.

Further, according to the above configuration, both metal substrates 2
Since the integrated combination of 2, 32 is inserted and mounted in the groove 37 formed in the radiator 36, the entire both metal substrates 22, 32 come into contact with the radiator 36, and the power element is generated. Not only the generated heat but also the heat generated in the snubber element can be effectively dissipated. Further, in the state of being inserted and mounted in the radiator 36, the circuits of the metal substrates 22 and 32 are substantially surrounded by the radiator 36, so that a large shield effect of radio noise can be obtained. Furthermore, the beam lead 2
Although the radiator 36 is not surrounded on the side where 7 is formed, since the beam lead 27 penetrates through the ferrite material 41 provided on the terminal plate 38, radio noise is absorbed by the ferrite material 41, Radiation of radio noise to the outside is suppressed as much as possible.

11 to 13 are views showing a second embodiment. In these examples, three power elements are mounted on one discharger 36, and each power element is a U-phase of three-phase AC,
This is used for controlling the V phase and the W phase. The control input terminals are not shown in the figure, and DC power supply input terminals C ₁ , C ₂ , C ₃ and common terminals E ₁ , E ₂ , E ₃ and three-phase outlet terminals O ₁ , O ₂ ,
O ₃ is indicated.

As shown in FIG. 11, each power element is mounted in three adjacent grooves formed in the discharger 36, and C ₁ , C ₂ , C ₃ and E ₁ projecting out of the discharger 36. , E ₂ , E
_As shown in FIG. 12, the surroundings of _{3 and} the surroundings of O ₁ , O ₂ and O ₃ are made of different magnetic materials, for example, ferrite materials 41A and 41B.
Surround with. As a result, an effect of removing common mode noise generated on the DC input side and the three-phase output side can be obtained.

FIG. 13 shows a terminal plate 38 provided in addition to the above. C ₁ , C ₂ , C ₃ and E _{1 of} each power element,
E ₂ and E ₃ are connected on this terminal board 38. Further, an external snubber element is connected between the CE terminals for the purpose of eliminating normal mode noise by directly connecting a capacitor between the C and E terminals on the terminal board 38 and assisting the function of the internal snubber. May be.

In this embodiment, the heat radiator has a shielding effect as in the first embodiment, and since three power elements are mounted inside the heat radiator, the power elements are generated. The heat generated is efficiently dissipated. In this embodiment, since the total amount of current passing through the ferrite material is set to ± 0, magnetic saturation hardly occurs, which is suitable for high power applications.

[0039]

As described above, according to the invention described in claim 1, the wiring length becomes extremely short, the parasitic inductance of the wiring can be reduced, and the surge voltage generated by switching is effective. It is possible to reduce the generation of radio noise to the outside by being absorbed by the antenna and reduce the size of the circuit including the power element and the snubber element.

According to the second aspect of the present invention, the beam lead for externally drawing out the integrally combined product of both substrates can be easily formed. According to the third aspect of the present invention, the elements of both substrates can be easily electrically connected to each other by the pad serving as the connection electrode. According to the invention of claim 4, it is possible to prevent excessive pressure or impact from being applied to the pad.

According to the fifth aspect of the present invention, not only the heat generated by the power element but also the heat generated by the snubber element can be effectively radiated, and a large shield effect of radio noise can be obtained. According to the inventions of claims 6 to 8,
Radio noise is absorbed by the magnetic material, and the emission of radio noise to the outside is suppressed as much as possible.

[Brief description of drawings]

FIG. 1 is a perspective view showing an embodiment of a connection structure of a power element and a snubber element according to the invention of claim 1, (A) shows a state before connection, and (B) shows a connection state.

FIG. 2 is a perspective view showing an embodiment of a mounting structure of a power element and a snubber element of the invention according to claim 2;

FIG. 3 is a perspective view showing an embodiment of a mounting structure of the power element and the snubber element of the invention according to claim 2;

FIG. 4 is a circuit diagram showing an example of a snubber circuit.

FIG. 5 is a cross-sectional view of a Si semiconductor substrate on which a snubber capacitor is formed.

FIG. 6 Equivalent circuit of snubber circuit

FIG. 7 is a sectional view showing a specific example of a circuit having a diode in a snubber circuit.

FIG. 8 is a sectional view showing a specific example of a circuit having a diode in the snubber circuit.

FIG. 9 is a cross-sectional view showing a conventional example of a connection structure between a power element and a snubber element and its mounting structure.

FIG. 10 is a perspective view showing a switching circuit.

FIG. 11 is a perspective view of another embodiment.

FIG. 12 is a perspective view of another embodiment.

FIG. 13 is a perspective view of another embodiment.

[Explanation of symbols]

 22 Metal Substrate 23 Chip of Power Element 25 Wiring Pattern 27 Beam Lead 28 Pad 29 Spacer 32 Metal Substrate 33 Capacitor 34 Resistor 35 Pad 36 Radiator 37 Groove 38 Terminal Board 39 Slit 41 Ferrite Material

Claims (8)

[Claims] 1. A substrate on which a power element is mounted and a substrate on which a snubber element is mounted are provided, and the two substrates are electrically connected to each other by abutting their element mounting surfaces against each other and integrally connecting them. A connection structure between a power element and a snubber element, which is characterized in that 2. A wiring pattern is formed on a substrate on which the power element is mounted, and one end portion of a beam lead for external extraction is joined to the wiring pattern, and the other end portion of the beam lead is connected to the other end portion. The connection structure of the power element and the snubber element according to claim 1, wherein the connection structure is formed by projecting from one end of the substrate. 3. The power element and the snubber according to claim 1, wherein pads for connection electrodes are mounted on the mutual coupling surfaces of the board on which the power element is mounted and the board on which the snubber element is mounted. Element connection structure. 4. A spacer for preventing an excessive pressure or impact from being applied to the pad is mounted on a mutual coupling surface of the board on which the power element is mounted and the board on which the snubber element is mounted. Item 4. A connection structure between the power element and the snubber element according to Item 4. 5. A mounting structure for a power element and a snubber element, characterized in that an integrated combination of both substrates according to claim 1 is inserted and mounted in a groove formed in a radiator. 6. The mounting structure for a power element and a snubber element according to claim 5, wherein the beam lead is projected from an upper surface of the radiator. 7. A terminal plate is attached to a groove forming position on the upper surface of the radiator, and a slit is formed in the terminal plate, and the beam lead protruding from the upper surface of the radiator is passed through the slit. 7. The mounting structure for a power element and a snubber element according to claim 5, wherein the tip of the beam lead is fixedly attached to a terminal plate. 8. The mounting structure for a power element and a snubber element according to claim 7, wherein the slit is surrounded by a magnetic material that absorbs a high frequency surge.