CN100593362C - Circuit boards, electronic equipment and power supply units - Google Patents

Abstract

The present invention relates to a circuit substrate, electronic equipment and a power supply unit. Can effectively suppress radiation noise. In this wiring board (lead frame) (10), a high-frequency current suppressing material (18) made of a conductive soft magnetic film with high magnetic permeability is provided on the lead frame portion (wiring portion) (10a) that becomes a radiation noise source. ) in the near field (magnetic field dominance region), preferably at the outer periphery of the lead frame portion (10a).

Description

Circuit boards, electronic equipment and power supply units

technology area

The present invention relates to a power supply device such as a wiring board, electronic equipment, and a switching power supply, and can suppress radiation noise generated by wiring.

This electronic equipment includes all electronic equipment that produces high-frequency radiated noise.

The power supply device is typically a switching power supply, including AC/DC converters, DC/AC converters, inverters (inverters), uninterruptible power supplies (UPS), and other power supply devices including power conversion units.

Background technique

In electronic devices that operate at high frequencies, radiation noise increases as processing speeds increase, and there is a growing need for technology development to more effectively suppress electromagnetic failures that occur.

In particular, due to the extreme increase in the popularity of electronic equipment at home and abroad in recent years, the erroneous operation of this equipment and other equipment caused by the radiation noise of these equipments has also had a great impact on the industrial society. The international CISPR (International Radio Trouble Special Committee) etc. are strictly regulating these electromagnetic troubles.

Such electromagnetic failures often occur at the stage of trial production evaluation, and have a profound impact on rework of circuit design and prolongation of development cycle. Therefore, the development of technologies that can easily suppress noise without changing circuit design, etc., has been desired.

For this reason, many techniques for suppressing such radiation noise have been developed. As one of these techniques, for example, Patent Document 1 shows that a ferrite layer is provided on the surface of an insulating substrate. The technique for suppressing radiation noise disclosed in this Patent Document 1 is to provide a noise suppressor made of a ferrite layer on the surface of a substrate.

Such radiation noise suppression technology is not limited to the wiring part which is the noise source, but is obtained by covering the surface of the substrate with a ferrite layer, so it can be widely used in an extremely wide area spanning electronic parts and wiring. , the radiation noise is suppressed in a wide range, and becomes such a suppression that suppresses the noise when the imaginary part μ" of the magnetic permeability representing the loss component of the noise suppressor is a high value, that is, 100 MHz to several GHz. However, to solve this problem often induces other new problems such as an increase in cost due to an increase in shutters or electronic components, and structural changes in electronic equipment.

Patent Document 1: JP-A-2005-129766.

Contents of the invention

Therefore, the present invention can effectively suppress the generation of radiation noise with respect to the wiring part which is a source of radiation noise, and solve the above-mentioned problems.

In the wiring board of the present invention, a high-frequency current suppressing material made of a conductive soft magnetic film is provided on a wiring board on which electronic components are mounted so as to be in physical contact with at least part of the conductor portion of the wiring that can become a source of radiation noise. status.

The above-mentioned wiring board includes a first substrate in which wiring of a metal material such as copper is printed on an insulating substrate, or a second substrate in which a lead frame having a desired circuit pattern is provided on the insulating substrate as wiring, and the lead frame Electronic components are mounted on it, and a part of the lead frame is resin-molded as a whole, such as a third substrate and other various substrates such as wiring.

In the case of the first substrate, a soft magnetic film may be provided on the printed wiring. In the case of the second and third substrates, a soft magnetic film can be provided on the lead frame. Alternatively, components such as jumpers may be used in the wiring portion, and a soft magnetic film may be formed on the jumpers to be mounted on the first, second, and third substrates. The shape of the wiring where the soft magnetic body is provided is not particularly limited.

Also, there is no limitation on the method of providing the soft magnetic body in the form of a film on the wiring.

Although the type is not limited as a soft magnetic material, it is better to have a higher value as a high magnetic permeability. The magnetic permeability can be expressed as μ′-jμ″. The loss component is expressed by taking μ′ as the real part of the magnetic permeability and μ″ as the imaginary part of the magnetic permeability.

Examples of soft magnetic materials that can provide such a value of magnetic permeability include iron-nickel alloys, iron-nickel-boron alloys, iron-nickel-molybdenum alloys, iron-nickel-silicon alloys, iron-nickel-copper alloys, iron-nickel-chromium alloys, iron-nickel-copper-molybdenum alloys, Iron-nickel-niobium alloys and other iron-nickel magnetic permeable alloys, iron-cobalt alloys, iron-cobalt-nickel alloys, cobalt-zirconium-niobium alloys, etc.

In addition, in addition to the above-mentioned soft magnetic materials, there are soft magnetic materials preferably in powder form, such as iron-aluminum-silicon alloy, (trade name: Sandast alloy [Sendast]), hydroxyl iron, manganese zinc type ferrite body, nickel-zinc ferrite, etc.

According to the wiring board of the present invention, the high-frequency current suppressing material made of the conductive soft magnetic film is provided on the conductor portion of the wiring where radiation noise occurs, so that only the skin flowing through the wiring portion can be effectively attenuated by the skin effect. High-frequency current, on the other hand, has low resistance to DC or low-frequency current, and does not hinder the DC or low-frequency current component flowing through the wiring.

To sum up, compared with the prior art, a shield or suppressor covering the entire surface of the substrate including the numerous electronic components and wiring mounted on the wiring substrate to the source of radiation noise is provided to suppress radiation noise. In the present invention, the structure of directly disposing a high-frequency current suppression material made of a conductive soft magnetic film on the conductor part of the wiring that becomes a source of radiation noise can be extremely easy, and it is low-cost and effectively suppresses the noise from several 10 MHz to several GHz. the occurrence of radiated noise.

In addition, in order to better attenuate high-frequency current and suppress the occurrence of radiation noise, the film thickness of the high-frequency current suppression material is made thicker than the thickness of the skin of the wiring.

According to the present invention, the high-frequency current suppressing material is provided in a thin film directly on the outer peripheral surface of the conductor part of the wiring that becomes the radiation noise source or within 5 cm in the near field region, so that the radiation noise can be suppressed extremely effectively before the radiation noise expands. happened.

In addition, in the case of the electronic device of the present invention, even though there are more or less openings or gaps, unlike the prior art, there is no leakage of radiation noise to the outside, and the above-mentioned problems can be solved at once.

In particular, in the present invention, there is no need to dispose a special radiation noise suppressing member on the wiring board side as in the prior art, so the assembly of the wiring board becomes easier and cost reduction is achieved.

When the above-mentioned wiring board is mounted on an electronic device such as a personal computer, as described above, radiation noise generated by high-frequency current can be suppressed, and an electronic device capable of reducing radiation noise can be obtained.

In addition, when the above-mentioned wiring board is mounted on a power supply device such as a switching power supply, as described above, radiation noise generated by high-frequency current can be suppressed, and a power supply device capable of reducing radiation noise can be obtained. In such a power supply device, in the switching power supply, a high-frequency current suppressing material may be provided on a current path through which a high-frequency current flows on the primary side or secondary side of the high-frequency transformer.

In particular, in the present invention, the high-frequency suppressing material is placed near the wiring near the field, that is, where the ripple impedance is small and the magnetic field is dominant, so although the magnetic shield is covered near the wiring, it is made of a soft magnetic film The high-frequency current suppression material can still effectively suppress the high-frequency magnetic field to reduce radiation noise.

In addition, when the soft magnetic material constituting the high-frequency current suppressing material is mixed into the organic binder in powder form and installed on the wiring part that can become a source of radiation noise, it can have a structure that is excellent in handling, and can be used when radiation noise occurs. The outer circumference of the wiring part is properly and easily set.

In a switching power supply, since the radiation noise power generated by the high-order high frequency associated with the switching operation of the switching transistor is very strong, although many countermeasures against this radiation noise have been proposed, the weight increases, the cost increases, and the radiation Issues such as noise leakage have not been resolved.

Effects of the Invention: In the present invention, the high-frequency current suppressing material made of soft magnetic material is provided in the magnetic field dominating region near the wiring part as the radiation noise source, so the constitution of the suppressing structure can be completed simply and at low cost. , In addition, it can effectively suppress radiation noise, which is extremely practical.

Description of drawings

1 is a plan view of a lead frame as a wiring board according to an embodiment of the present invention;

Figure 2 is a partial schematic diagram of the electrical circuit of the switching power supply;

FIG. 3 is an explanatory diagram of a magnetic field and an electric field generated by a high-frequency loop current flowing in the lead frame portion of FIG. 5;

Fig. 4 is an explanatory diagram of fluctuating impedance;

5 is a cross-sectional view of a lead frame portion (wiring portion) where a loop current flows on a lead frame that is a wiring substrate according to an embodiment of the present invention;

Fig. 6 (a), (b) is the case of the magnetic gold plating of the soft magnetic film as the high-frequency current suppression material on the lead frame and the case of non-magnetic gold plating. comparison chart;

Fig. 7 is the frequency spectrum waveform chart of the peak point in the case of the magnetic gold-plating of the soft magnetic film as the high-frequency current suppression material on the lead frame and the situation of non-magnetic gold-plating;

Fig. 8 is an explanatory diagram of placing a high-frequency current suppression material made of powder on the lead frame portion of Fig. 5;

9 (a) to (c) are explanatory views of a part of the high-frequency current suppression material of FIG. 5 disposed on the lead frame portion;

Fig. 10 is a representation diagram of frequency characteristics of magnetic permeability;

11 (a) to (q) are explanatory diagrams showing a high-frequency current suppression material in which a plurality of magnetic films are laminated;

Fig. 12 is an explanatory diagram illustrating that the high-frequency current suppression material is arranged on the lead frame via a space or even an insulator;

Figure 13(a)-(d) are explanatory diagrams of high-frequency current suppression materials being arranged on terminals or heat sinks of electronic components, and metal baskets;

Fig. 14 is a perspective view of an annular metal body used on an analytical model;

15 (a) to (c) are explanatory diagrams showing the measurement results of radiation noise of the high-frequency current suppression material using the annular metal body of FIG. 14;

Fig. 16 (a) ~ (c) are the current density distribution diagrams showing the change of the resistivity of the high-frequency current suppression material using the annular metal body of Fig. 14;

17( a ) and ( b ) are explanatory diagrams showing measurement results of radiation noise using a high-frequency current suppressing material composed of a plurality of magnetic films of the ring-shaped metal body in FIG. 14 .

Explanation of reference signs

10 lead frame; 10a lead frame part; 12 high-frequency transformer (electronic component); 14 aluminum electrolytic capacitor (electronic component); 16 switching transistor (electronic component); 18 high-frequency current suppression material; Crossed electronic components.

Detailed ways

Hereinafter, a wiring board according to an embodiment of the present invention and a switching power supply, which is an example of an electronic device (power supply unit) equipped with the wiring board, will be described in detail with reference to the drawings.

A wiring board according to an embodiment of the present invention and a switching power supply equipped therewith will be described with reference to FIGS. 1 to 3 . Electronic equipment equipped with such a switching power supply is strictly controlled for electromagnetic failure in the range of, for example, 30 MHz to 1 GHz.

FIG. 1 is a schematic view showing the wiring board and electronic components mounted thereon. In this figure, the wiring board is constituted by a lead frame 10 corresponding to a mounting pattern of electronic components of a switching power supply.

Mounted electronic components constituting a power supply are connected and fixed to the lead frame 10 indicated by the solid line. In Fig. 1, for simplification, the dotted line surrounded by a rectangle shows the representative of the electronic components: high-frequency transformer 12, the electronic component on the primary side of the high-frequency transformer 12, that is, the aluminum electrolytic capacitor 14 for smoothing, and the switching element. The switching transistor 16 and the electronic component 20 mounted so that the lead frame 10 intersects three-dimensionally.

The lead frame 10 includes a lead frame portion for mounting electronic components and a lead frame portion for wiring between electronic components. In FIG. 1 , regions where radiation noise occurs (for example, regions where loop current flows) are indicated by regions A1 to A3 surrounded by dashed-two dotted lines. In this region, radiation noise generation regions are respectively shown on the primary side and the secondary side of the high frequency transformer 12 . The boundary between the primary side and the secondary side is indicated by a dotted line.

FIG. 2 schematically shows a part of the electrical circuit of the switching power supply corresponding to these electronic components 12 , 14 , and 16 . The electrical circuit configuration of the switching power supply in FIG. 2 is well known, so its description is omitted.

A region A1 shown in FIG. 1 is a region showing loop current LC flowing through the primary side of the high-frequency transformer 12 .

FIG. 3 shows a perspective view of a part of the lead frame portion 10a through which the loop current LC flows in the switching power supply. As shown in FIG. 3, a magnetic field H1 is generated around the lead frame 10a by the loop current LC flowing in the lead frame portion 10a, and the change of the magnetic field H1 generates an electric field E1, and the change of the electric field E1 generates a magnetic field H2, and then The change of the magnetic field H2 further generates the electric field E2, so that the magnetic fields H1, H2, H3... and the electric fields E1, E2,... are alternately generated.

In this relationship, if the loop current LC increases, the strength of the magnetic field increases, and the strength of the electric field increases as the strength of the magnetic field increases. In addition, as the frequency of the loop current LC increases, fluctuations in the magnetic field also increase, and the intensity of the electric field also increases.

Also, if the loop current LC flows in the lead frame portion 10a, a magnetic field and an electric field propagate alternately, generating radiation noise. In this case, the magnetic field H1 is dominant in the vicinity (near field) of the lead frame portion 10a.

The variation of the fluctuating impedance Z is shown in FIG. 4 . In FIG. 4, the horizontal axis represents the distance D from the lead frame portion 10a, and the vertical axis represents the ripple impedance Z (=electric field E at any position/magnetic field H at any position).

As shown in FIG. 4, the area near the lead frame portion 10a is the near field NF; the area far away is the far field FF. In the near field NF, the magnetic field H1 is dominant and can be approximated to the magnetic field H1.

The junction of the near field NF and the far field FF is (1/2π) of the electromagnetic wave wavelength λ, that is, about λ/6. Far-field FF can capture electromagnetic waves that combine electric and magnetic fields.

Since the concept of the near field is λ/2π, in the case of radiated noise from 30MHz to 1GHz, the near field area is 1.7m to 5cm, so as the near field area with stronger magnetic field components, it is preferable to be 5cm away from the wiring part Set the high-frequency current suppression material within.

Referring to FIG. 5 , which shows a structure in which a high-frequency current suppressing material made of a conductive soft magnetic film is directly provided on the outer periphery of the conductor part of the wiring, a wiring board and a switching power supply equipped with it will be described.

FIG. 5 shows a cross section of a lead frame portion (wiring portion) 10a through which a loop current LC flows. As shown in FIG. 5, in order to suppress the radiated noise from the lead frame portion most efficiently, the high-frequency current suppressing material 18 is directly and physically in contact with the entire outer peripheral surface of the lead frame portion 10a, and is provided as a thin film with a uniform film thickness. shape. This high-frequency current suppressing material 18 is provided on the lead frame portion 10a through which the loop current LC flows. The high-frequency current suppression material 18 is not provided in the lead frame portion where radiation noise is not generated and the high-frequency current suppression material 18 is not required, thereby reducing the material cost.

As shown in FIG. 5, on the primary side of the high-frequency transformer 12, a high-frequency current suppression material 18 is formed on the lead frame portion 10a through which the loop current LC flows. The high-frequency current suppression material 18 is made of several 10 MHz to several GHz. Made of conductive soft magnetic film with high magnetic permeability.

As the soft magnetic body forming the high-frequency current suppressing material 18, for example, iron-nickel alloy, iron-nickel-boron alloy, iron-nickel-molybdenum alloy, iron-nickel-silicon alloy, iron-nickel-copper alloy, iron-nickel-chromium alloy, iron-nickel-copper-molybdenum alloy, iron Strong magnetic iron-nickel alloys such as nickel-niobium alloys, iron-cobalt alloys, iron-cobalt-nickel alloys, cobalt-zirconium-niobium alloys, etc.

The soft magnetic body is not limited to the form of a thin film. For example, electrolytic gold plating, electroless gold plating, sputtering, vapor deposition, rolling composite materials, etc. can be used to form the soft magnetic body into a thin film.

FIGS. 6( a ) and ( b ) show peak points of radiation noise when the wiring board shown in FIG. 1 is viewed from above. Fig. 6 (a) is the situation that the high-frequency current suppression material 18 is not set on the lead frame part 10a, and Fig. 6 (b) is the situation that the high-frequency current suppression material 18 is set on the lead frame part 10a, in order to be in Fig. 6 ( a) and (b) schematically show the color display screen of the magnetic field strength measuring device, the area with high magnetic field strength is marked with thick double cross-hatching, the area with medium magnetic field strength is marked with double cross-hatching, and the area with low magnetic field strength is represented by double cross-hatching Dashed hatching indicates.

As shown in FIGS. 6( a ) and ( b ), when the high-frequency current suppressing material 18 is provided on the lead frame portion 10 a, radiation noise is significantly suppressed. In addition, because it is difficult to see on the above-mentioned color display screen, the positions of parts such as aluminum electrolytic capacitors and high-frequency transformers are indicated by dotted lines for judging.

The material of the lead frame portion for measurement in FIG. 6 is copper, and the soft magnetic body as the high-frequency current suppressing material 18 is an iron-nickel alloy, and its film thickness is 50 μm. Radiation noise was measured with an electromagnetic wave analysis measurement system (ESV-3000) manufactured by Noise Laboratories (Japan). The measurement frequency is 30 MHz to 300 MHz.

The peak point in the region where the magnetic field intensity is high is 90.4dBμV in FIG. 6(a), and 87.7dBμV in FIG. Noise suppression effect.

Theory explains the reason for the reduction of radiation noise.

如此表皮厚度δ的式子所示，作为高频电流抑制材料18，导磁率高能够有效地抑制高频电流。A high-frequency current flows in the skin of the lead frame portion 10a due to the skin effect. In this case, the skin thickness δ is expressed in resistivity ρ, magnetic permeability μ, and frequency f as

As shown by the expression of the skin thickness δ, the high-frequency current suppressing material 18 has a high magnetic permeability and can effectively suppress high-frequency current.

For example, when the lead frame portion 10a is made of copper and the high-frequency current suppressing material 18 is an iron-nickel alloy, the resistivity ρ of the lead frame portion 10a is ρ=1.7× ^10-8 Ωm, and the resistance of the high-frequency current suppressing material 18 is The ratio ρ is ρ=2×10 ⁻⁸ Ωm, and the resistivity ρ of the high-frequency current suppressing material 18 is high.

Therefore, the high-frequency current suppressing material 18, which is a soft magnetic body with high magnetic permeability μ and high resistivity ρ, becomes thinner because of the high magnetic permeability μ, and can effectively suppress high-frequency current due to the high resistivity ρ, Thereby, radiation noise can be suppressed.

In FIG. 7 , the radiation noise reduction effect of the high-frequency current suppressing material 18 is shown over the entire frequency spectrum. 7 is an explanatory diagram of a spectrum waveform showing a peak point (place of maximum magnetic field strength) with frequency (Hz) on the horizontal axis and magnetic field strength (dBμV/m) on the vertical axis.

In addition, the data line 1 showing the measurement result is when the high-frequency current suppression material 18, that is, the soft magnetic body is not magnetically plated on the lead frame portion 10a; the data line 2 is the soft magnetic body as the high-frequency current suppression material 18. In the case of magnetic gold plating on the lead frame portion 10a, the measurement frequency range is 30 MHz to 300 MHz.

As described above, it is preferable to directly provide the high-frequency current suppressing material 18 on the lead frame portion (wiring portion) 10a where the high-frequency current flows, thereby suppressing the generation of a magnetic field and preventing leakage of radiation noise.

In addition, the high-frequency current suppressing material 18 can also be made of the soft magnetic body 18a made of powder, which is directly mixed into the organic binder 18b by means of kneading and dispersion, as shown in FIG. 8 .

The powder shape has spherical shape and crushed shape (flat shape, needle shape, etc.), and because the powder shape is flat shape, needle shape, it produces high magnetic permeability. On the other hand, if the powder shape is spherical, there is no anisotropy of magnetic permeability, and there is no need to consider alignment.

As these powdery soft magnetic bodies 18a, for example, iron-nickel-silicon alloy (trade name: Sandast alloy [Sendast]) with high high-frequency magnetic permeability, carbonyl iron, manganese-zinc ferrite, nickel-zinc ferrite, etc. The soft magnetic body 18a can be one type, or a composite soft magnetic body composed of several types.

As the organic binder 18b, for example, ABS resin, polyester resin, polyvinyl chloride resin, polyvinyl butyral resin, polyurethane resin, cellulose resin, nitrile butadiene rubber, benzene Thermoreversible resins such as ethylene butadiene rubber or copolymers of these.

In addition, examples of other organic binders 18b include thermosetting resins such as epoxy resins, phenol resins, amide resins, and imide resins.

The forming method of the powdery high-frequency current suppression material 18 is printing, dispensing, spray coating, etc., forming a sheet-like paste, or punching into a sheet and then joining, or coating powder, or stamping, etc., the method is not limited .

9( a ), ( b ), and ( c ) show structural examples of the high-frequency current suppressing material 18 made of a soft magnetic material. As shown in FIGS. 9( a ), ( b ) and ( c ), the high-frequency current suppressing material 18 may be provided only on a part of the lead frame portion 10 a.

Fig. 9 (a) is the structure that both sides of lead frame part 10a are provided with high frequency current suppression material 18, Fig. 9 (b) is the structure that one side of lead frame part 10a is provided with high frequency current suppression material 18, Fig. 9 (c) is a structure in which the high-frequency current suppressing material 18 is provided on one surface and side surfaces of the lead frame portion 10a. When the lead frame portion 10a is circular, the high-frequency current suppressing material 18 may be provided on the entire periphery or only a part thereof.

In addition, the high-frequency current suppressing material 18 may be formed by laminating a plurality of magnetic films a and b having different magnetic permeability as shown in FIG. 10 . FIG. 10 shows the frequency characteristics of the magnetic film a and the magnetic film b having different magnetic permeability. The magnetic film a has a frequency characteristic as high as several GHz, and the magnetic film b has an extremely high frequency characteristic of several 10 MHz.

11(a) to (q) show that a high-frequency current suppressing material 18 composed of magnetic films a and b is provided on the lead frame portion 10a. The magnetic film a has a low suppression effect on the high-frequency current of 10 MHz, because the magnetic film b is just the opposite, and has a high suppression effect on the high-frequency current of 10 MHz. Therefore, since the magnetic film a and b are laminated, it can be obtained in The effect of suppressing radiation noise in a wide range of several 10MHz to several GHz. At this time, the more the current of several GHz flows, the more prominent the skin effect is, and it is more preferable to arrange the magnetic film a having high magnetic permeability at several GHz outside the lead frame which is more surface. 11( a ) to ( q ) are an example of a combination of high-frequency current suppressing material 18 in which magnetic films a and b with different magnetic permeability are laminated, and the number of layers and the method of combination are not limited.

In addition, the high-frequency current suppressing material 18 may have a laminated structure of a magnetic film and a resistive film having a high resistivity. In the high-frequency current suppressing material 18 composed only of a magnetic film, although the magnetic film is required to have high magnetic permeability and high resistivity, the composition of the high-frequency current suppressing material 18 is separated into a magnetic film and a resistive film, which can effectively Suppresses radiation noise. The high-frequency current suppression material 18 composed of a magnetic film and a resistive film is the same as the laminated structure shown in FIGS. The resistive film is aluminum (ρ=2.75×10 ^-8 Ωm), zinc (ρ=5.9×10 ^-8 Ωm), nickel (ρ=7.24×10 ^-8 Ωm), tin (ρ=11.4×10 ^-8 Ωm) , chromium (ρ=17×10 ^-8 Ωm), nickel-chromium alloy (ρ=109×10 ^-8 Ωm), other high-resistance materials, organic substances or oxides, and those with added P or B, Mo, etc. Composite materials, the type of material is not fixed. In addition, the resistive film may be roughened by mechanical polishing or etching using a chemical reaction.

The high-frequency current suppressing material 18 shown in FIG. 12 may also be disposed on the lead frame 10 a via a space or even an insulating material 20 . Since the skin thickness of the high-frequency current flowing on the lead frame 10a can be reduced according to the magnetic permeability of the magnetic film, the same noise suppression effect as when the magnetic film is directly provided on the lead frame can be obtained.

The high-frequency current suppressing material 18 is added to the lead frame of such a plate-shaped metal forming the wiring portion of the electronic circuit, or may be provided on a printed circuit board obtained by printing and wiring metal materials such as copper on an insulating substrate.

The high-frequency current suppression material 18 can also be arranged on switching transistors, etc., terminals of electronic components that generate high-frequency noise or metal objects near them, such as terminals 22, heat sinks 24, and metal baskets 26 of electronic components shown in FIG. 13 superior. What Fig. 13 (a), (b) showed is the situation that high-frequency current suppressing material 18 is arranged on the terminal 22 of electronic component, and what Fig. 13 (c) shows is that high-frequency current suppressing material 18 is arranged on the heat sink 24 Situation, what Fig. 13 (d) shows is the situation that high-frequency current suppressing material 18 is arranged on the metal frame 26, the terminal 22 of electronic component is connected on the lead frame part 10a, heat sink 24 and metal frame 26 are connected In order to stabilize the potential, high-frequency currents that cause radiation noises flow, and the high-frequency current suppressing material 18 is placed in these places to suppress radiation noises as well.

14 and 15 show analytical models related to suppression of radiation noise. FIG. 14 is a perspective view of the loop metal 28 through which a high-frequency loop current LC flows. Fig. 15 (a) is the situation that high-frequency current suppressing material 18 is not set on ring-shaped metal 28, Fig. 15 (b) is the situation that high-frequency current suppressing material 18 is set on ring-shaped metal 28, Fig. 15 (c ) shows the analysis results of radiation noise when the high-frequency current suppressing material 18 is provided on the entire outer peripheral surface of the ring-shaped metal body 28 .

Comparing the analysis results of Fig. 15(a), (b) and (c), it is found that when the high-frequency current suppressing material 18 is provided on the entire outer peripheral surface of the ring-shaped metal body 28, the radiation noise can be suppressed to the maximum. . The high-frequency current suppression material 18 has a thickness of 10 μm and an analysis frequency of 30 MHz.

The magnetic film of the high-frequency current suppressing material 18 is preferably higher in magnetic permeability, but the range in which radiation noise can be suppressed is, for example, μ′=5-10000, μ″=0-500.

16(a), (b), and (c) show the current density distribution when the resistivity of the high-frequency current suppressing material 18 is changed in the structure of FIG. 15(c). Fig. 16(a) shows resistivity ρ=2×10 ^-8 Ωm, (b) shows ρ=100×10 ^-8 Ωm, and (c) shows current density variation when ρ=10000×10 ^-8 Ωm. As shown in Fig. 16 (a), (b), (c), if the resistivity increases, it is difficult to have current flow in the high-frequency current suppression material 18, and the resistivity ρ of the high-frequency current suppression material 18 is the best. It is limited within the range of ρ=2×10 ^-8 Ωm to 10000×10 ^-8 Ωm.

17( a ) and ( b ) show the analysis results of suppressing radiation noise by the high-frequency current suppressing material 18 composed of two kinds of magnetic films. Fig. 17(a) shows that the high-frequency current suppressing material composed of the magnetic film a with a magnetic permeability μ of 400 and a resistivity ρ=20×10 ^-8 Ωm is set at 2 μm. Fig. 17(b) shows that the high-frequency current suppressing material 18 composed of the magnetic film a and the magnetic film b with a magnetic permeability μ of 1000 and a resistivity ρ=20×10 ⁻⁸ Ωm is provided on the lead frame portion 10 a. The total film thickness of the magnetic films a and b in FIG. 17(b) is 1 μm. The analysis frequency is 30MHz.

Comparing the results of FIGS. 17( a ) and ( b ), it is found that lamination of a plurality of magnetic films can suppress high-frequency noise more effectively.

The high-frequency current suppression material 18 used in this analytical model is provided along the annular surface of the annular metal body 28 . The size of the ring-shaped metal body 28 is 1.5mmФ, and the radiation noise was analyzed by an electromagnetic field analysis tool (JMAG-Studio) manufactured by "Nippon Sogo Laboratories".

所以电阻率ρ越厚，表皮厚度δ也越厚。在此将表皮厚度δ考虑为配线部分的剖面积S的话，作为配线所具有的电阻值R为

伴随着导磁率μ以及电阻率ρ的增加有增大的倾向。L是配线的长度。也就是说配线部分的导磁率μ和电阻率ρ的增加，配线的电阻值R乃至是电阻Z也可以增大。The following characteristics are required for the high-frequency current suppressing material 18 that suppresses radiation noise. Skin thickness δ is expressed by resistivity ρ, magnetic permeability μ and frequency f as

Therefore, the thicker the resistivity ρ, the thicker the skin thickness δ. Here, if the skin thickness δ is considered as the cross-sectional area S of the wiring part, the resistance value R of the wiring is

It tends to increase with the increase of magnetic permeability μ and resistivity ρ. L is the length of the wiring. That is to say, as the magnetic permeability μ and resistivity ρ of the wiring part increase, the resistance value R and even the resistance Z of the wiring can also be increased.

Although the magnetic permeability of the high-frequency current suppression material 18 made of soft magnetic film is better, according to the making of "high specific resistance Ni-Fe class soft magnetic film of electrolytic method (surface technology Vo1.49, No.3 , 1998)", the soft magnetic film using FeNi is in the band above several 10MHz, the magnetic permeability is in the above-mentioned literature, μ' is up to 1000, μ"=500 or so, by adding diethyltryptamine (DET) etc., Attenuation of magnetic permeability in a frequency band of 30 MHz or higher can be suppressed.

In addition, according to "Fabrication of Soft Magnetic NiFeB/NiPC/NiFeB Laminated Film by Electroless Plating Method (The 23rd Japanese Society of Applied Magnetism Academic Lecture Collection, 1999)", the magnetic permeability of NiFeB with B added to FeNi is also in the same range. In the band above several 10 MHz, the above-mentioned maximum magnetic permeability of μ′=1000, μ″=500.

在这里记述导磁率μ＝1000、电阻率ρ＝2×10^-8Ωm的特性的磁性膜和有导磁率μ＝10、电阻率ρ＝1000×10^-8Ωm的特性的磁性膜的表皮厚度δ。当频率为30MHz的时候，前者的磁性膜的表皮厚度δ为0.4μm，后者的磁性膜的表皮厚度δ为91.9μm。另外当频率为1GHz的时候，前者的磁性膜的表皮厚度δ为0.07μm，后者的磁性膜的表皮厚度δ为15.9μm。高频电流抑制材料18的厚度最好在使30MHz～1GHz的高频电流收敛于膜中的0.1μm～100μm的范围内。Skin thickness δ is expressed by resistivity ρ, magnetic permeability μ and frequency f as

Here, the skin thickness of a magnetic film having the characteristics of magnetic permeability μ=1000 and resistivity ρ=2×10 ^-8 Ωm and a magnetic film having the characteristics of magnetic permeability μ=10 and resistivity ρ=1000×10 ^-8 Ωm are described. δ. When the frequency is 30 MHz, the skin thickness δ of the former magnetic film is 0.4 μm, and the skin thickness δ of the latter magnetic film is 91.9 μm. In addition, when the frequency is 1 GHz, the skin thickness δ of the former magnetic film is 0.07 μm, and the skin thickness δ of the latter magnetic film is 15.9 μm. The thickness of the high-frequency current suppressing material 18 is preferably within a range of 0.1 μm to 100 μm for converging a high-frequency current of 30 MHz to 1 GHz in the film.

In the high-frequency current suppressing material 18 composed of a plurality of magnetic films or even resistive films, it is preferable to set a film thickness corresponding to the thickness of the skin in each layer.

By disposing the high-frequency current suppressing material 18 directly on the lead frame portion 10a through which a high-frequency current flows as described above, generation of current can be suppressed and leakage of radiation noise can be prevented.

When the above-mentioned wiring board is mounted on an electronic device such as a personal computer, as described above, it is possible to obtain an electronic device capable of reducing radiation noise by suppressing the generation of radiation noise due to high-frequency current.

When the above-described wiring board is mounted on a power supply device such as a switching power supply, the generation of radiation noise due to high-frequency current is suppressed as described above, and a power supply device that can reduce radiation noise can be obtained. The high-frequency current suppressing material 18 may be provided on the current path through which the high-frequency current flows on the primary side and the secondary side of the high-frequency transformer in the switching power supply of the power supply unit.

The present invention is not limited to the above-mentioned embodiments, but also includes various changes and modifications within the scope described in the technical solution.

Claims (12)

1. Switching Power Supply, it has wiring substrate, and switch element is installed on this wiring substrate at least, and the lead frame of the distribution part of this wiring substrate by being formed electronic loop by plate-shape metal constitutes, and this Switching Power Supply is characterised in that,

The high-frequency current that constitutes by the soft magnetic film of conductivity suppress the distribution that material is arranged on described lead frame partly go up, near the described switch element and the distribution that flows through for high-frequency current partly on, and cover this distribution whole periphery partly;

The permeability of high-frequency current inhibition material is μ '=5～10000, μ, and "=0～500, its resistivity is ρ=2 * 10 than the resistivity height of lead frame ^-8Ω m～10000 * 10 ^-8Ω m, high-frequency current suppress the thickness of material in the scope of 0.1 μ m～100 μ m.

2. Switching Power Supply as claimed in claim 1 is characterized in that,

High-frequency current suppresses material and is laminated by a plurality of soft magnetic films with conductivity.

3. Switching Power Supply as claimed in claim 1 is characterized in that,

High-frequency current suppresses material and is arranged near the 5cm as near-field region that can become the distribution of radiation noise source part.

4. Switching Power Supply as claimed in claim 1 is characterized in that,

High-frequency current suppresses material and is arranged on the distribution part that can become the radiation noise source via space and even insulating bodies.

5. Switching Power Supply, it has wiring substrate, and switch element is installed on this wiring substrate at least, and the lead frame of the distribution part of this wiring substrate by being formed electronic loop by plate-shape metal constitutes, and this Switching Power Supply is characterised in that,

Suppress on the distribution part that material is arranged on described lead frame, by the stacked high-frequency current that forms of soft magnetic film and the resistive film of resistivity in prescribed limit, and cover this distribution whole periphery partly near the described switch element and on the distribution that flows through for the high-frequency current part;

The permeability of high-frequency current inhibition material is μ '=5～10000, μ, and "=0～500, its resistivity is ρ=2 * 10 than the resistivity height of lead frame ^-8Ω m～10000 * 10 ^-8Ω m, high-frequency current suppress the thickness of material in the scope of 0.1 μ m～100 μ m.

6. Switching Power Supply as claimed in claim 5 is characterized in that,

Above-mentioned resistive film is that resistivity is ρ=2 * 10 ^-8Ω m～10000 * 10 ^-8Resistive film in the scope of Ω m.

7. Switching Power Supply as claimed in claim 5 is characterized in that,

High-frequency current suppresses material and is arranged near the 5cm as near-field region that can become the distribution of radiation noise source part.

8. Switching Power Supply as claimed in claim 5 is characterized in that,

High-frequency current suppresses material and is arranged on the distribution part that can become the radiation noise source via space and even insulating bodies.

9. an electronic equipment is characterized in that, is provided with as any described Switching Power Supply of claim 1～8.

10. electronic equipment as claimed in claim 9 is characterized in that,

Described high-frequency current inhibition material is arranged on the metal object of the overlapping high frequency noise of meeting.

11. a supply unit is characterized in that, is provided with as any described Switching Power Supply of claim 1～8.

12. supply unit as claimed in claim 11 is characterized in that,

Described high-frequency current inhibition material is arranged on the metal object of the overlapping high frequency noise of meeting.

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