JP2008035657A - Power module for power converter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To simply and easily reduce common-mode noise. <P>SOLUTION: A certain impedance is imparted to an insulating substrate (here, a high-impedance substrate 63 is equivalent to it) itself of a module in an AC-manner, so as to execute a noise countermeasure with a common loop via a converter module 3 and an inverter module 4. By this, it is possible to take a countermeasure even with a PIM module, for example, in which a part between an inverter and a converter is built in one module. In addition, Fig. 1 shows an example that the inverter and the converter are respectively arranged in different substrates. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a configuration for reducing noise emitted during switching of a power semiconductor.

In recent years, EMC (Rules for Electromagnetic Compatibility) regulations have become stricter, and reduction of radiation noise has become a technical issue in various industrial fields including general-purpose inverters. In particular, measures are required to reduce the noise generated when the power semiconductors, which are the main components, and the power module on which these are mounted are switched.
When taking countermeasures for EMC in general-purpose inverters, etc., filter insertion to the input is often used, which is mainly common mode noise via the ground line between the motor and other main circuit components. The current is suppressed. However, noise that can be suppressed by the input filter is noise caused by a common loop passing through the input line, and it is difficult to suppress noise generated between common loops other than the input line.

8 and 9 show conventional examples. In FIG. 8, 1 is an input filter, 2 is a varistor, 3 is a converter module, 4 is an inverter module, 5 is a load, 65 is an insulating substrate, and 7 is a cooling fin. In FIG. 9, reference numeral 6 denotes a module, 61 denotes a chip, 62 denotes a conductor pattern, and 64 denotes a base metal plate.
In other words, a ceramic (Al ₂ O ₃ ) substrate is conventionally used as the insulating substrate 65, but this has a dielectric loss tangent (tan δ) of 0.1 or less (1M to 100 MHz), and therefore has a very high resistance to alternating current. small.

Therefore, measures are taken at each common loop. For example, in Patent Document 1, as a ground line in the main circuit system, a countermeasure is provided by providing a damping impedance to a fin of an electric power converter, an AC reactor, and a ground line of a motor that is a load.
In Patent Document 2, for the power inverter module, a main wiring having a low resistivity and a skin wiring having a high resistivity and magnetic permeability are formed in a circuit pattern so that noise is suppressed in the skin wiring portion.
In addition, Patent Document 3 discloses that in an electric compressor integrated with a motor drive circuit, by using an insulating material such as rubber for piping or the like existing between a housing and a vehicle body, the impedance is increased and noise is reduced. It is cited as an effective effect.

  However, with respect to the common countermeasure of the power converter in Patent Document 1, a damping impedance is provided only for the line dropped from the fin to the ground, but in reality, a noise current also flows in the common loop between the inverter module and the converter module. This means that noise countermeasures for this loop have not been achieved. In other words, the countermeasure against the damping impedance cannot cope with the case where the inverter and the converter are mounted on the same fin. Also, even if the fins on which the inverter and converter are mounted are separated and separated, if a PIM (Power Integrated Module) type module in which the inverter and converter are built in one module is used Can not do it.

  In addition, the addition of impedance is presumed to be effective in suppressing noise functionally and structurally, but the magnitude of the damping impedance is unknown. In addition, the noise reduction amount cannot be controlled unless the frequency at which noise is to be reduced, that is, the target frequency, is clarified and a frequency having a damping impedance is selected. Furthermore, the insertion of impedance complicates the configuration. In particular, between the fins of the power converter and the ground, in general, the fins are bonded or screwed and directly connected to the housing and dropped to the ground. This complicates the structure, increasing the number of steps and making it complicated.

On the other hand, in Patent Document 2, the wiring of the circuit pattern related to the power inverter module is provided with skin wiring having high resistivity and magnetic permeability to reduce noise. It is fundamentally different. In addition, the high-frequency resistance by the skin effect is aimed at, but even at 10 MHz where the effect is seen, the resistivity of the flat wiring member is as small as 10 ⁻¹ Ω / cm. It is difficult to earn with the skin effect alone.

  Furthermore, in Patent Document 3, an impedance is added between the housing and the vehicle body of the motor drive circuit integrated electric compressor in which a drive circuit incorporating a module such as an IGBT is incorporated. Since the loop that can be performed is larger than the loop that is formed around the module in question, the frequency band of noise that can be suppressed by this countermeasure is greatly different. In Patent Document 3, the loop between the inverter and the converter around the module is not targeted, and the influence of the vehicle body when dropping to ground from the housing in which both the inverter and the converter are incorporated is examined. Not only are there no measures around the module to be output, but the target frequency is not clear.

JP 2006-025467 A JP 2001-326300 A JP 2006-027315 A

  The present invention has been made in view of the above-described points, and an object thereof is to enable an appropriate impedance to be added to a common loop through a module substrate without increasing unnecessary space and man-hours. At that time, it is desirable to clarify the “what frequency range” noise is reduced by “what kind of impedance addition”.

In order to solve such a problem, in the invention of claim 1, in the power module of the power conversion device using the power semiconductor element,
The insulating substrate itself on which the power module is mounted has an impedance to suppress common mode noise current.
In the first aspect of the present invention, the insulating substrate can increase the impedance in the vicinity of 1 M to 100 MHz extending from the conductive electromagnetic wave to the radiation noise (the second aspect of the present invention). In the above, the insulating substrate can have a resistance value of 0.05 to 240Ω as an impedance (invention of claim 3).
In the invention according to any one of claims 1 to 3, the insulating substrate can have a value of 1 to 10% as tan δ (invention of claim 4). In the invention, the insulating substrate may be a thermosetting composition in which an epoxy resin is filled with an inorganic material (invention of claim 5). In the invention of claim 5, a low-elasticity rubber component can be added to the epoxy resin (invention of claim 6).

In invention of Claim 7, in the power module of the power converter device using the power semiconductor element,
The sheet member laid under the insulating substrate on which the power module is mounted is provided with impedance to suppress common mode noise current.
In the invention of claim 7, the sheet member can increase the impedance in the vicinity of 1 M to 100 MHz extending from the conductive electromagnetic wave to the radiation noise (invention of claim 8). In this case, the sheet member can have a resistance value of 0.05 to 240Ω as an impedance (invention of claim 9).
Moreover, in the invention of any one of claims 7 to 9, the sheet member can have a value of 1 to 10% as tan δ (invention of claim 10), and any one of claims 7 to 10. In the invention, the sheet member may be a thermosetting composition in which an epoxy resin is filled with an inorganic material (invention of claim 11). In the invention of claim 11, a low-elasticity rubber component can be added to the epoxy resin (invention of claim 12).

  According to the present invention, the module and the fin are arranged so that the common mode noise can be taken even when the module has an integral structure, such as between the inverter and the converter, which has been difficult with the measures of the input filter. A high impedance material is placed between the two. In the case of inserting a conventional damping impedance, an increase in complicated structure and man-hours, such as floating a fin and insulating it from the housing, is unavoidable. Thus, a great effect is brought about in suppressing common mode noise.

First, an insulating substrate (hereinafter also referred to as a high impedance substrate) of the module itself has an impedance so that a countermeasure can be taken with a common loop through the inverter module and the converter module. An embodiment based on this viewpoint is shown in FIGS.
In FIG. 1, 1 is an input filter, 2 is a varistor, 3 is a converter module, 4 is an inverter module, 5 is a load, 63 is a high impedance substrate (insulating substrate), and 7 is a cooling fin. 2 denotes a module, 61 denotes a chip, 62 denotes a conductor pattern, and 64 denotes a base metal plate.

  In FIG. 1, the converter module 3 and the inverter module 4 are abbreviated, but in reality, two 1-in-1 modules in which one chip 61 that is a semiconductor rectifier element or semiconductor switch element is mounted on a high-impedance substrate 63 are mounted. 2 in 1 modules, 6 in 1 6 in 1 modules and 7 in 7 in 1 modules are used, and the above modules are used in combination depending on the application and current / voltage class.

Further, according to this method, a PIM module in which an inverter and a converter are arranged on one high impedance substrate 63, or a converter portion is mounted on one high impedance substrate 63, and the inverter portion is another one high impedance substrate. Even when these high impedance substrates are mounted on one base metal plate 64, measures can be taken.
However, if it is not an integrated type, a member (hereinafter also referred to as a high impedance sheet) that provides the same effect may be laid under the insulating substrate, and another embodiment based on this point of view may be used. 3 and FIG.

In the conventional example shown in FIGS. 8 and 9, a ceramic (Al ₂ O ₃ ) substrate is used as the insulating substrate 65, and this has a dielectric loss tangent (tan δ) of 0.1 or less (1M to 100 MHz), and therefore Resistance value against alternating current is very small.
In contrast, the high-impedance substrate (insulating substrate) 63 shown in FIGS. 1 and 2 and the high-impedance sheet 66 shown in FIGS. 3 and 4 have a tan δ of 1 or more (1 M to 100 MHz) and higher than the conventional one. Since it has a resistance value, the noise current flowing through these can be suppressed. That is, in FIGS. 3 and 4, by placing the high impedance sheet 66 between the fins 7 under the module, a resistance and a member capacitance are inserted in series as an equivalent circuit of the common loop. Therefore, if this member is a high impedance member, the noise current of the common loop can be suppressed.

  Although FIG. 1 shows an example in which the inverter and converter modules are separately configured as a general example, they may be PIM modules mounted on the same base metal plate. Further, the positional relationship between the input filter 1 and the varistor 2 in the circuits shown in FIGS. 1, 3, 8 and the like may be on the input power supply side, and may enter the right side of the rectifier diode. The location varies depending on how to set. In addition, the arrangement of the ground C and the varistor C in the filter is not limited to that shown in FIGS. 1, 3, and 8, and the arrangement can be changed depending on how the circuit constants are set. The varistor of the converter module may be ground C and may be omitted.

  The target frequency is 1 M to 100 MHz, which has a low countermeasure effect in a general filter design used in an inverter or the like. In the filter, the main noise is around 150 kHz where the noise is the largest at the noise terminal voltage, and a material having a large impedance at this frequency is used. However, when such a conventional filter is used, the noise at 150 kHz can be reduced in many cases. The effect diminishes in the frequency region after 1 MHz.

  The noise generated in this region is not sufficient as a countermeasure because the margin becomes smaller as the standard becomes more severe (for example, equivalent to Class A or Class B in CISPR (International Electrotechnical Commission)). Since many of the loops of noise generated at 1M to 100 MHz pass through the module substrate in terms of circuit configuration, they are also effective as countermeasures. Therefore, in the present invention, 1M to 100 MHz, which is difficult to take measures with a general filter, is targeted, and a large impedance is exhibited at this frequency.

Furthermore, in the present invention, when the high-resistance insulating substrate is put into practical use, it is determined as 0.05 to 240Ω as a realizable resistance value. The basis for this will be described below.
First, the resistance value R of a certain frequency f on the substrate is expressed by the following equation (1).
From tan δ = ωCR, R = tan δ / ωC = tan δ / 2πfC (1)
In the formula (1), parameters for determining R include tan δ, frequency f, and capacitance C.

The frequency is determined to be 1M to 100 MHz as a range in which noise to be reduced exists. Subsequently, the capacitance C can be expressed by the following equation (2), where S is the substrate area of the module and d is the substrate thickness.
C = ε ₀ ε _r S / d (2)
ε ₀ : dielectric constant of vacuum ε _r : relative dielectric constant of module

As for the area S, a small capacity to large capacity class module is used when a motor drive is performed by using an inverter module and a converter module. = 2.3 × 10 ^{−4 to} 1.9 × 10 ⁻² [m ² ]. Further, the thickness of the high impedance sheet laid under the high impedance substrate and the module is determined as d = 0.1 to 3 mm as a usable range in the semiconductor power module application while ensuring thermal conductivity and insulation. As a capacitance value that can be taken under these conditions, the capacitance C was determined to be 5 to 6000 pF from the above equation (2).

Further, tan δ possesses frequency characteristics and temperature dependence characteristics. Accordingly, when the semiconductor power module is used in a temperature range of −40 to 150 ° C. at a frequency of 1 M to 100 MHz, tan δ is in a range of 1 to 10% as a practical value. .
As described above, the ranges of the frequency f, the capacitance C, and tan δ that are the parameters of the resistance R are determined. If the range that can be used as a high impedance substrate under this condition is calculated from the above equation (1), 0.05Ω <resistance value < 240Ω. Table 1 summarizes these results.

  5a to 5e show examples of common loops having a noise suppressing effect by inserting a high impedance substrate as shown in FIGS. For the circuit of FIG. 1 with the filter 1 and the varistor 2, there are five common loops 1-5 indicated by arrows in FIGS. This also applies to the case where a high impedance sheet is inserted as shown in FIGS. In addition, in the inverter module and the converter module, as long as there is no common loop, it is needless to say that a high impedance substrate or a high impedance sheet is not necessary.

Table 2 shows the measurement results of the noise terminal voltage when a high impedance material is used for the substrate of the inverter module and the inverter is operated with a general circuit configuration as shown in FIG.

  Table 2 shows an example in which Example 1 shows a resistance of 4.8Ω at 10 MHz and Example 2 shows a resistance of 10Ω at 10 MHz. As a result of the comparison, a module using a ceramic substrate was used, and as a result, the reduction effect of -5 dB was obtained in Example 1, and the reduction effect of -11 dB was obtained in Example 2. Moreover, the measurement result of the noise terminal voltage in the case of Example 2 in which the reduction effect of −11 dB was obtained is displayed in a graph in FIG. 7 in comparison with the conventional example.

Next, specific examples of materials and manufacturing methods of the high impedance substrate or the high impedance sheet will be described.
As the high-impedance substrate or high-impedance sheet, a thermoplastic composition in which an inorganic filler is blended with an epoxy resin having a high dielectric loss tangent tan δ is used. The filling amount of the inorganic filler is about 60 to 90 wt% of the total composition, and the blending amount is controlled in accordance with the necessary thermal conductivity within this range. As the epoxy resin, bisphenol A type epoxy resin, bisphenol F type epoxy resin, phenol novolac type epoxy resin, cresol novolac type epoxy resin are used. Each resin may be used alone or in combination of two or more.

Here, in order to increase tan δ, a low-elastic rubber component is added to the above-described epoxy resin. Silicone rubber, acrylic rubber, acrylonitrile butadiene rubber, etc. are used for the rubbery component.
Moreover, in order to make the epoxy resin itself a flexible structure, a rubber material is reacted. This rubber component generates a loss component that makes it difficult for the dipole to follow the electric field when an alternating electric field is applied, and tan δ increases. The loss component is converted into heat energy. By doing so, an insulating layer having high tan δ characteristics can be formed in a wide temperature range from −60 ° C. to 180 ° C.

  On the other hand, as the inorganic filler, those having low thermal conductivity such as silicon oxide, aluminum oxide, silicon nitride, aluminum nitride, boron nitride and the like are used. These may be single systems or mixed systems. The filling amount is about 60 to 90 wt% of the total composition. In addition, in order to improve the adhesiveness of an inorganic filler and an epoxy resin, a silane coupling agent is added to resin. Although the resin is cured by overheating, imidazole is used as a curing accelerator to advance the reaction at this time. A solvent such as methyl ethyl ketone MEK is added to the resin composition and mixed to obtain a constant viscosity resin solution. This resin solution is coated on a roll-shaped copper foil sheet having a thickness of 18 to 175 μm with a coater to an arbitrary thickness. The thickness is 50 to 200 μm. As the rolled copper foil, one having a width of 1 m or 1.5 m is usually used. The length is from several tens of meters to several hundreds of meters.

  Next, the solvent of the coated resin solution is volatilized to prepare a prepreg. This prepreg is cut into a length of about 1 to 1.5 mm to form one sheet. Next, the prepreg is placed on a metal base, is heat-formed with a vacuum heat-forming machine, and is completely cured. Thereby, the thermal conductivity of the insulating layer becomes 1.6 W / m · K or more. The thickness is 100 μm or more.

Here, the relative dielectric constant ε _r of the resin is 5.0 or less. Since the thickness of the insulating layer is 100 μm or more and ε _r is 5.0 or less, the insulating layer can be excellent in insulating characteristics such as partial discharge characteristics and migration resistance.
The material of the base metal plate 64 is made of aluminum, copper, iron, SiC and alloys thereof, or clad materials thereof, and the thickness is generally 0.5 to 3.0 mm. Aluminum is generally used because of its heat dissipation and economy.

Circuit diagram showing an embodiment of the present invention Schematic diagram showing module configuration of FIG. Circuit diagram of another embodiment of the present invention Overview diagram showing module configuration of FIG. Explanatory drawing explaining the 1st example of a common loop Explanatory drawing explaining the 2nd example of a common loop Explanatory drawing explaining the 3rd example of a common loop Explanatory drawing explaining the 4th example of a common loop Explanatory drawing explaining the 5th example of a common loop Inverter circuit diagram for noise terminal voltage evaluation Spectrum example of noise terminal voltage in the case of FIG. Circuit diagram showing a general inverter circuit Schematic diagram showing the module configuration corresponding to FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Input filter, 2 ... Varistor, 3 ... Converter module, 4 ... Inverter module, 5 ... Load, 61 ... Chip, 62 ... Conductor pattern, 63 ... High impedance substrate (insulating substrate), 64 ... Base metal plate, 65 ... Insulating substrate, 66 ... high impedance sheet, 7 ... cooling fin.

Claims (12)

In the power module of the power converter using the power semiconductor element,
A power module of a power conversion device, wherein an impedance is given to an insulating substrate itself on which the power module is mounted to suppress a common mode noise current.   The power module of a power conversion device according to claim 1, wherein the insulating substrate has a large impedance in the vicinity of 1M to 100MHz, which spans radiation noise from conductive electromagnetic waves.   The power module of the power conversion device according to claim 1, wherein the insulating substrate has a resistance value of 0.05 to 240Ω as an impedance.   The power module of a power converter according to any one of claims 1 to 3, wherein the insulating substrate has a value of 1 to 10% as tan δ.   The power module for a power converter according to any one of claims 1 to 4, wherein the insulating substrate is a thermosetting composition in which an inorganic material is filled in an epoxy resin.   The power module of a power converter according to claim 5, wherein a low-elastic rubber component is added to the epoxy resin. In the power module of the power converter using the power semiconductor element,
A power module for a power converter, wherein a sheet member placed under an insulating substrate on which the power module is mounted has an impedance to suppress common mode noise current.   The power module of the power conversion device according to claim 7, wherein the sheet member has a large impedance in the vicinity of 1M to 100MHz ranging from conductive electromagnetic waves to radiation noise.   The power module for a power converter according to claim 7 or 8, wherein the sheet member has a resistance value of 0.05 to 240Ω as an impedance.   The power module of a power converter according to any one of claims 7 to 9, wherein the sheet member has a value of 1 to 10% as tan δ.   The power module of a power converter according to any one of claims 7 to 10, wherein the sheet member is a thermosetting composition in which an inorganic material is filled in an epoxy resin.   The power module of the power converter according to claim 11, wherein a low-elastic rubber component is added to the epoxy resin.

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