JP2023150211A - High voltage application circuit - Google Patents

Abstract

To provide a high voltage application circuit capable of suppressing corona discharge.SOLUTION: The high voltage application circuit comprises: a heat sink 10 having a plane connected to a ground potential; a flat-plate shaped ceramic plate 20 provided on the plate of a first metal member; a metal substrate 30; and an insulating resin 40 covering the metal substrate 30 except a first terminal 36 and a second terminal 37. The metal substrate 30 has a metal material 31, an insulating layer 32, a first conductive region 33 to which a first high voltage is applied, and a second conductive region 34 to which a second high voltage is applied, and an electric component 35 is mounted between the first conductive region 33 and the second conductive region 34, and the first terminal 36 and the second terminal 37 are formed. The metal substrate 30 is thermally connected to the heat sink 10 via the insulating resin 40 and the first terminal 36 and the second terminal 37 of the metal substrate 30 are provided on a side opposite to the ceramic plate 20.SELECTED DRAWING: Figure 1

Description

The present disclosure relates to a high voltage application circuit to which a high voltage is applied.

Plasma processing equipment used in the process of manufacturing semiconductor wafers and liquid crystal substrates is equipped with a power supply device that generates a high voltage, such as a pulse power supply device that generates a pulsed voltage (pulse voltage). For example, see Patent Document 1).
For example, a pulse power supply device converts DC power into AC power using an inverter circuit, converts it into AC power with a different voltage value using a transformer, rectifies and smoothes it using a rectifier and smoothing circuit, and then converts the pulse voltage into AC power using a switching circuit, etc. configured to generate.
The pulse power supply device as described above outputs a pulse voltage having a high voltage potential with an absolute value of about 10 kV. For this reason, in the rectifying and smoothing circuit and the switching circuit, there are parts (hereinafter referred to as high potential parts) to which a high voltage with an absolute value of about 10 kV is applied. As is well known, the higher the applied voltage, the more likely corona discharge will occur, so it is necessary to suppress corona discharge in a high voltage application circuit used at such a high potential site.

An example of a document disclosing a technique for suppressing corona discharge is Patent Document 2. This Patent Document 2 describes a technology for suppressing the occurrence of corona discharge caused by concentration of an electric field in a gap (part of a screw hole) around a screw (ground potential) of a high voltage application circuit that includes components such as switching elements. Disclosed. Specifically, corona discharge is suppressed by inserting a ground potential conductor between the gap around the screw and the high potential area to eliminate electric field concentration in the gap.

Japanese Patent Application Publication No. 2013-125729 Japanese Patent Application Publication No. 2018-067644

However, Patent Document 2 is only a measure against the void around the screw. Furthermore, since the applied voltage is about 3.3 kV, it is a relatively low voltage.
On the other hand, if a high voltage with an absolute value of 10 kV or more is applied, for example, corona discharge becomes even more likely to occur. It is necessary to take measures to prevent corona discharge from occurring between the components. In particular, since corona discharge is likely to occur from the terminals and angular parts of components, it is necessary to take measures to suppress corona discharge at these parts.

The present invention has been made in view of these problems, and aims to provide a high voltage application circuit that can suppress corona discharge between a high potential part to which a high voltage is applied and a member at ground potential. purpose.

The high voltage application circuit according to the present disclosure includes:
a first metal material having a plane connected to ground potential;
a flat plate-shaped first insulating material provided on a plane of the first metal material;
a second metal material, an insulating layer, a first conductive region to which a first high voltage is applied, and a second conductive region to which a second high voltage different from the first high voltage is applied, and the first conductive region and the second conductive region, and a first terminal electrically connected to the first conductive region and a second terminal electrically connected to the second conductive region. a metal substrate formed;
a second insulating material that covers the metal substrate except for the first terminal and the second terminal,
The metal substrate is provided at a position opposite to the first metal material with respect to the first insulating material,
A surface of the metal substrate close to the first insulating material is thermally connected to the first insulating material via the second insulating material,
The first terminal and the second terminal of the metal substrate are provided on a side opposite to the first insulating material.

According to the present invention, in a high voltage application circuit, corona discharge between a high potential portion to which a high voltage is applied and a member at ground potential can be suppressed.

FIG. 1 is a cross-sectional view of the high voltage application circuit 1 of this embodiment. FIG. 2 is a plan view of the high voltage application circuit 1 of this embodiment viewed from above. FIG. 3 is an explanatory diagram for explaining the potential of the metal substrate 30. FIG. 4 is a cross-sectional view of a high voltage application circuit 2 of a comparative example corresponding to FIG.

The high voltage application circuit 1 of this embodiment is used, for example, in a pulse power supply device that supplies a pulsed voltage (pulse voltage) to a plasma processing apparatus. For example, a pulse power supply device converts DC power into AC power using an inverter circuit, converts it into AC power with a different voltage value using a transformer, rectifies and smoothes it using a rectifying and smoothing circuit, and then converts the absolute value into AC power using a switching circuit, etc. Outputs a high pulse voltage of about 10kV.
Since the high voltage application circuit 1 is used in a part where a high voltage with an absolute value of about 10 kV is applied (hereinafter referred to as a high potential part), such as a rectifying and smoothing circuit or a switching circuit, it suppresses the occurrence of corona discharge. We need to create a structure that allows us to do so.

Hereinafter, an embodiment of a high voltage application circuit 1 according to the present disclosure will be described in detail with reference to the accompanying FIGS. 1 to 4.
FIG. 1 is a cross-sectional view of the high voltage application circuit 1 of this embodiment.
FIG. 2 is a plan view of the high voltage application circuit 1 of this embodiment viewed from above.
As shown in FIGS. 1 and 2, the high voltage application circuit 1 includes a heat sink 10, a ceramic plate 20 provided above the heat sink 10, a metal substrate 30 provided above the ceramic plate 20, and a metal substrate 10. and an insulating resin 40 covering 30.

Note that in FIG. 2, the insulating resin 40 is shown as being transparent, so that the insulating layer 32, the first conductive region 33, the second conductive region 34, the electrical component 35, and the second conductive region 34 inside the metal substrate 30, which would normally not be visible, can be seen. A first terminal 36 and a second terminal 37 are illustrated. The metal material 31 is not shown because it is hidden by the insulating layer 32, the first conductive region 33, and the second conductive region 34. Furthermore, only a portion of the insulating layer 32 is shown due to the limitations of the drawing.

The heat sink 10 is an example of a "first metal material" and is a cooling metal material connected to a ground potential, and has a flat plate shape with a plane. The material of the heat sink 10 is, for example, copper, aluminum, etc., and a material with high thermal conductivity is suitable. Note that the heat sink 10 may be configured to allow cooling water to circulate inside the heat sink 10.

The ceramic plate 20 is an example of a "first insulating material" and is a flat plate-shaped member provided on the plane of the heat sink 10 (first metal material). Preferably, alumina, silicon nitride, aluminum nitride, etc. are used. The thickness of the ceramic plate 20 in this embodiment is 10 mm.
Generally, the thicker the ceramic plate 20 is, the longer the distance between the metal material 31 of the metal substrate 30 and the heat sink 10, which will be described later, makes it more difficult for corona discharge to occur. However, the thicker the ceramic plate 20 is, the lower the heat dissipation effect by the heat sink 10 becomes, so it is not preferable to make it too thick. As in this embodiment, by configuring the ceramic plate 20 to be an alumina ceramic plate and having a thickness of 10 mm, corona discharge is suppressed when a high voltage with an absolute value of 10 kV or more is applied to the component. At the same time, a sufficient heat dissipation effect can be obtained.

The metal board 30 is, for example, a circuit board using a metal base board or a metal core board, and heat dissipation can be improved by using a metal material in the base or inside of the board. Although FIG. 1 shows an example in which a metal base substrate is used as the metal substrate 30, it is also possible to use a metal core substrate.

As shown in FIG. 1, the metal substrate 30 includes, for example, a metal material 31, an insulating layer 32, a first conductive region 33, a second conductive region 34, an electrical component 35, a first terminal 36, and a second terminal 37. ing.

The metal material 31 is an example of a "second metal material" and is a metal material for improving heat dissipation. The material of the metal material is, for example, aluminum, copper, or stainless steel. Although the metal material 31 is positioned below the metal substrate 30 as a metal base in FIG. 1, it may be sandwiched between insulating layers like a metal core substrate.
Although the metal material 31 is not electrically connected to other conductors, it is thermally connected to the heat sink 10 via the insulating resin 40 and the ceramic plate 20, so that the heat generated by the electrical components 35 can be effectively absorbed. It can dissipate heat effectively.
The thickness of the metal material 31 is approximately 0.8 to 5.0 mm. In this embodiment, a metal material 31 having a thickness of 2 mm (aluminum or copper) is used.
The thermal conductivity and thickness of the metal material 31 are determined in consideration of the cost, the size of the metal substrate 30, the weight of the package (to avoid warping), etc.
Note that, as described above, since corona discharge is likely to occur in angular areas, the corners of the metal material 31 and the first conductive region 33 are not at right angles but are rounded, as shown in FIG. .

The insulating layer 32 is an insulating layer formed on the metal material 31 and serves to insulate the metal material 31 from the first conductive region 33 and the second conductive region 34 .
Note that the thickness of the insulating layer 32 is about 0.1 mm, so it is thin. However, in FIG. 1, the thickness is shown to be thicker than it actually is in order to make it easier to understand.

The first conductive region 33 is a conductive region to which a first high voltage having an absolute value of 10 kV or more is applied, and is formed by processing the copper foil layer on the surface of the metal substrate 30. For example, a voltage of -10 kV is applied to the first conductive region 33.

The second conductive region 34 is a conductive region to which a second high voltage with an absolute value of 10 kV or more is applied, and is formed by processing the copper foil layer on the surface of the metal substrate 30. For example, a voltage of -11.5 kV is applied to this second conductive region 34.

The electrical component 35 is an electrical component mounted between the first conductive region 33 and the second conductive region 34. The electrical components 35 are, for example, diodes, capacitors, inductors, switching elements, resistors, connectors with two or more terminals, jumpers, and the like.
In the above example, a potential of -10 kV is applied to one terminal of the electrical component 35, and a voltage of -11.5 kV is applied to the other terminal. That is, in the above example, a voltage with a potential difference of 1.5 kV is applied to both ends of the electric component 35.

Note that the voltage applied across the electrical component 35 (the voltage between the first conductive region 33 and the second conductive region 34) may be a DC voltage, but is usually an AC voltage or a pulse voltage. It is a voltage whose voltage value changes as follows. In this case, the voltage applied across the electrical component 35 changes over time.

Furthermore, although only one electrical component 35 is shown in FIG. 1 to simplify the explanation, a plurality of electrical components 35 may be mounted. Furthermore, a plurality of electrical components 35 connected in series may be mounted between the first conductive region 33 and the second conductive region 34.
Furthermore, if the electrical component 35 is, for example, a MOSFET (Metal-Oxide-Semiconductor Field Effect Transistor), there are originally three terminals (gate, drain, and source). Therefore, conductive regions other than the first conductive region 33 and the second conductive region 34 are required, but in order to simplify the explanation, some terminals and conductive regions of the electrical component 35 are omitted in FIG. .

The first terminal 36 is a terminal electrically connected to the first conductive region 33, and can be electrically connected to the outside via this terminal. Further, the second terminal 37 is a terminal electrically connected to the second conductive region 34, and can be electrically connected to the outside via this terminal. Therefore, the first terminal 36 and the second terminal 37 formed on the related substrate 30 protrude from the insulating resin 40.

Note that in the following, the first conductive region 33 to which the first high voltage is applied and a region having the same potential as the first conductive region 33 will be referred to as a first high potential region, and the second conductive region 34 to which a second high voltage is applied will be referred to as a first high potential region. and a region with the same potential as the second conductive region 34 is defined as a second high potential region.

The insulating resin 40 is an example of a "second insulating material" and is an insulating material that covers the metal substrate 30 except for the first terminal 36 and the second terminal 37, and is made of an insulating material such as silicone, for example.
This insulating resin 40 is used to suppress corona discharge from the metal substrate 30 and to improve heat dissipation. Therefore, it is desirable that the insulating resin 40 has high dielectric strength and good thermal conductivity.

Here, it is known that the dielectric strength of an insulating material such as silicone is greater than the dielectric strength of air, which is 3.0 kV/mm. For example, silicone rubber having a dielectric strength of about 20 to 30 kV/mm is commercially available.
Further, the thermal conductivity of the silicone rubber is higher than the thermal conductivity of air, 0.0241 W/m·K, for example, about 0.1 to 5.1 W/m·K. Therefore, if the insulating resin 40 is formed of an insulating material such as silicone, corona discharge can be suppressed without significantly reducing heat dissipation.
As described above, a variety of insulating materials such as silicone are on the market depending on the application, so it is only necessary to select an appropriate material by considering dielectric strength and thermal conductivity.

Note that, as will be described later, the thickness of the insulating resin 40 applied to the bottom surface of the metal plate is about 0.1 mm, so it is thin. Further, the thickness of the insulating resin 40 on the side surface of the metal plate is preferably 1 to 2 mm or more. However, in FIG. 1, the thickness is shown different from the actual thickness in order to make it easier to understand.

Furthermore, as described above, the voltage applied across the electrical component 35 (the voltage between the first conductive region 33 and the second conductive region 34) usually has a voltage value such as an alternating current voltage or a pulse voltage. is the voltage that changes. Therefore, in terms of suppressing corona discharge, not only the dielectric strength but also the dielectric constant is important. This will be explained.

<Regarding the dielectric constant of the insulating resin 40>
Corona discharge occurs on the path from the metal substrate 30 to the heat sink 10. In this path, it can be considered as a capacitor (capacitor) with the metal material 31 of the metal substrate 30 serving as one electrode and the heat sink 10 serving as the other electrode.
Furthermore, when the high voltage applied to the electrical component 35 changes in voltage value such as an alternating current voltage or a pulse voltage, it is desirable that the dielectric constant of the insulating resin 40 is large. This is because the larger the dielectric constant, the larger the capacitance between the electrodes, and the smaller the impedance to alternating current. As a result, the electric field strength weakens (becomes smaller), which makes it difficult for corona discharge to occur. Therefore, the relative permittivity of the insulating resin 40 needs to be greater than 1, which is the relative permittivity of the atmosphere, and is preferably at least 3 or more. This makes it possible to reliably weaken the electric field strength and suppress corona discharge.

Further, the dielectric constant of the insulating resin 40 is preferably about the same as the dielectric constant of the ceramic plate 20. This is because if the dielectric constant of the insulator (dielectric) on the path from the metal substrate 30 to the heat sink 10 is uniform, the electric field strength changes linearly on the path, causing corona discharge. This is because it works in a direction that makes it difficult to do so.
However, the relative permittivity of alumina, silicon nitride, aluminum nitride, etc. used for the ceramic plate 20 is about 8 to 10, but the relative permittivity of silicone, etc. used for the insulating resin 40 is about 6 at most. It is difficult to make the relative permittivity the same. Therefore, the insulating resin 40 is selected after allowing a certain degree of difference in dielectric constant. Considering this situation, it is preferable that the dielectric constant of the insulating resin 40 is 6 or more. In this case, the difference between the dielectric constant of the ceramic plate 20 and the dielectric constant of the insulating resin 40 is 2 to 4. In this way, it becomes easier to suppress the occurrence of corona discharge.

<About the potential of the metal substrate 30>
As described above, although the metal material 31 is not electrically connected to other conductors, it has a high potential. The reason for this will be explained with reference to FIG.
FIG. 3 is an explanatory diagram for explaining the potential of the metal substrate 30.
Since the first conductive region 33, the second conductive region 34, and the heat sink 10 are conductors, it can be considered that the capacitor 50 has the first conductive region 33 and the second conductive region as one electrode and the heat sink 10 as the other electrode. I can do it. Strictly speaking, a voltage of, for example, -10 kV is applied to the first conductive region 33, and a voltage of, for example, -11.5 kV is applied to the second conductive region 34, so there are two types of capacitors. To simplify the explanation, it is assumed here that a voltage of -10 kV is applied to one electrode of the capacitor 50, and the other electrode is at ground potential.

Because of the above relationship, the metal material 31 becomes a floating electrode between the one electrode and the other electrode. Therefore, as shown in FIG. 3, the capacitor 50 can be considered to be a first capacitor 51 and a second capacitor 52 connected in series.
In this case, the dielectric between the electrodes of the first capacitor 51 becomes the insulating layer 32. The dielectric between the electrodes of the second capacitor 52 is the insulating resin 40 and the ceramic plate 20.
However, the thickness of the insulating resin 40 applied to the bottom surface of the metal material 31 (about 0.1 mm) is much thinner than the thickness of the ceramic plate 20 (10 mm). Further, although the dielectric constant of the insulating resin 40 and the dielectric constant of the ceramic plate 20 are not the same, they are not significantly different. Therefore, in order to simplify the explanation, the following description will be made assuming that the dielectric between the electrodes of the second capacitor 52 is the ceramic plate 20.

Here, the capacitance C51 of the first capacitor 51=ε ₀・ε _r51・S ₅₁ /d ₅₁ ,
It is assumed that the capacitance C52 of the second capacitor 52=ε ₀ ·ε _r52 ·S ₅₂ /d ₅₂ .
However, ε ₀ is the permittivity of vacuum, ε _r51 is the relative dielectric constant of the insulating layer 32, S ₅₁ is the electrode area of the first capacitor 51, d ₅₁ is the distance between the electrodes of the first capacitor 51, and ε _r52 is the ceramic plate 20. , _S52 is the electrode area of the second capacitor 52, and _d52 is the thickness (10 mm) of the ceramic plate 20.

Further, in order to simplify the explanation, the relative permittivity ε _r51 of the insulating layer 32 and the relative permittivity ε _r52 of the ceramic plate 20 are the same, and the electrode area of the first capacitor 51 and the electrode area of the second capacitor 52 are the same. Suppose that they are the same.
Assuming this, C51:C52=100:1. That is, the capacitance C51 of the first capacitor 51 is 100 times the capacitance C52 of the second capacitor 52. Therefore, in terms of alternating current, the impedance of the first capacitor 51 is 1/100 of the impedance of the second capacitor 52. Further, the voltage applied to the first capacitor 51 is 1/100 of the voltage applied to the second capacitor 52.
Therefore, the potential of the metal material 31 serving as the floating electrode is approximately -10 kV, which is almost the same as that of the first conductive region 33 and the second conductive region . Therefore, corona discharge is likely to occur in the metal material 31 (particularly at the corners).

<Method for forming insulating resin 40>
Next, a method for forming the insulating resin 40 will be explained.
(Step 1) An insulating resin 40 is applied to the bottom surface of the metal substrate 30 (the surface close to the ceramic plate 20).
(Step 2) The metal substrate 30 is fixed to the ceramic plate 20, and a mold is fixed around the metal substrate 30. Since the mold is slightly larger in size than the metal substrate 30, the metal substrate 30 fits into the mold.
(Step 3) After filling the mold with insulating resin 40, it is hardened.
(Step 4) By removing the mold, the metal substrate 30 is covered with the insulating resin 40.
(Step 5) The insulating resin 40 at the first terminal 36 and the second terminal 37 is removed, and the first terminal 36 and the second terminal 37 are attached.
By performing the above steps, the metal substrate 30 can be covered with the insulating resin 40 except for the first terminal 36 and the second terminal 37.

Note that in order to improve heat dissipation from the bottom surface of the metal substrate 30, the thermal conductivity of the insulating resin 40 is preferably 0.3 W/m·K or more. Furthermore, the viscosity of the insulating resin 40 is preferably 10 Pa·s or less so that it can be applied thinly.

Further, since corona discharge is likely to occur on the side surfaces of the metal substrate 30 (particularly the corners of the metal material 31 and the corners of the first conductive region 33), it is preferable that the thickness of the insulating resin 40 is 1 to 2 mm or more. .

<Effects of providing the insulating resin 40>
Next, the effect of providing the insulating resin 40 will be further explained by comparing with the comparative example shown in FIG.
FIG. 4 is a cross-sectional view of a high voltage application circuit 2 of a comparative example corresponding to FIG. 1, which does not include the insulating resin 40 compared to the high voltage application circuit 1 shown in FIG. Note that the configuration other than the insulating resin 40 is the same as in FIG. 1, so the same symbols as in FIG. 1 are used.

In the comparative example shown in FIG. 4, since the insulating resin 40 is not provided, corona discharge is likely to occur. Corona discharge is particularly likely to occur in the portions surrounded by dotted lines, that is, the corners of the metal material 31. Similarly, it is considered that corona discharge is likely to occur at the corners of the first conductive region 33 as well.
However, since the metal substrate 30 of this embodiment is covered with the insulating resin 40 except for the first terminal 36 and the second terminal 37, it is possible to make corona discharge less likely to occur. This is because the dielectric strength of the insulating resin 40 is greater than that of air. Further, since the dielectric constant of the insulating resin 40 is sufficiently larger than that of air, even if the high voltage applied to the electrical components 35 etc. changes in voltage value such as an AC voltage or a pulse voltage, , the electric field strength at the high potential sites (the first high potential site and the second high potential site) can be weakened (reduced). Therefore, it is possible to make it difficult to generate corona discharge. That is, corona discharge can be suppressed.

This suppression of corona discharge will be explained in more detail.
Assuming that the location where corona discharge occurs is the corner of the metal material 31 of the metal substrate 30, the path from the corner of the metal material 31 to the heat sink 10 is compared between the comparative example and this embodiment as follows. Become.
(1) Comparative example: corner of metal material 31 → air layer → ceramic plate 20 → heat sink 10
(2) This embodiment: corner of metal material 31 → insulating resin 40 → ceramic plate 20 → heat sink 10

In this way, the portion that was an air layer in the comparative example is replaced by the insulating resin 40 with high dielectric strength in the present embodiment, so that corona discharge can be made less likely to occur than in the comparative example.
Further, since the first terminal 36 and the second terminal 37 of the metal substrate 30 are provided on the opposite side of the ceramic plate 20, the distance from the first terminal 36 and the second terminal 37 to the heat sink 10 is can be physically far away. Therefore, corona discharge from the first terminal 36 and the second terminal 37 can be made less likely to occur.
Therefore, if the high voltage application circuit 1 is configured as in the present embodiment, the heat sink 10 can be connected to a high potential portion with an absolute value of 10 kV or more (particularly a corner of the metal material 31 or a corner of the first conductive region 33, etc.). Corona discharge between the two can be suppressed.

Further, the metal substrate 30 is provided at a position opposite to the heat sink 10 with respect to the ceramic plate 20, and is thermally connected to the ceramic plate 20 via the insulating resin 40. Therefore, the heat generated in the metal substrate 30 can be effectively radiated. That is, in this embodiment, not only can corona discharge be suppressed, but also measures can be taken in terms of heat dissipation.

<Others>
(1) An oil compound may be applied between the heat sink 10 and the ceramic plate 20. In this way, the adhesion between the heat sink 10 and the ceramic plate 20 can be improved, so that the effect of dissipating heat generated in the metal substrate can be improved.
(2) In the embodiment shown in FIGS. 1 and 2, the first high potential region (for example, −10 kV) is located outside the metal substrate 30, and the second high potential region (for example, −11.5 kV) is located outside the metal substrate 30. It was placed at the center of the metal substrate 30. However, the present invention is not limited thereto, and the first high potential region may be disposed at the center of the metal substrate 30 and the second high potential region may be disposed outside the metal substrate 30. However, as explained with reference to FIG. 4, since corona discharge is more likely to occur on the outside of the metal substrate 30, it is preferable to arrange the first high potential portion having a low potential on the outside.
(3) In the embodiment described above, the first high potential portion and the second high potential portion have a negative (minus) potential, but they may have a positive (plus) potential.

Although the embodiments of the present disclosure have been described above, the embodiments described above are presented as examples, and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, substitutions, and changes can be made without departing from the gist of the invention. These novel embodiments and modifications thereof are included within the scope and gist of the invention, and are included within the scope of the invention described in the claims and its equivalents.

Further, the effects in the embodiments described in this specification are merely examples and are not limited, and other effects may also be provided.

1 High voltage application circuit 1
10 heat sink 20 ceramic plate 30 metal substrate 40 insulating resin 31 metal material 32 insulating layer 33 first conductive region 34 second conductive region 35 electrical component 36 first terminal 37 second terminal

Claims (4)

a first metal material having a plane connected to ground potential;
a flat plate-shaped first insulating material provided on a plane of the first metal material;
a second metal material, an insulating layer, a first conductive region to which a first high voltage is applied, and a second conductive region to which a second high voltage different from the first high voltage is applied, and the first conductive region and the second conductive region, and a first terminal electrically connected to the first conductive region and a second terminal electrically connected to the second conductive region. a metal substrate formed;
a second insulating material that covers the metal substrate except for the first terminal and the second terminal,
The metal substrate is provided at a position opposite to the first metal material with respect to the first insulating material,
A surface of the metal substrate close to the first insulating material is thermally connected to the first insulating material via the second insulating material,
The first terminal and the second terminal of the metal substrate are provided on a side opposite to the first insulating material,
High voltage application circuit. The second insulating material has a dielectric constant of 3 or more,
The high voltage application circuit according to claim 1. an oil compound is applied between the first metal material and the first insulating material;
The high voltage application circuit according to claim 1 or 2. The first high voltage is a voltage with an absolute value of 10 kV or more,
The high voltage application circuit according to any one of claims 1 to 3, wherein the second high voltage has an absolute value of 10 kV or more and is different from the first high voltage.

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