Electrical device

Abstract

This electrical device comprises: a multilayer wiring substrate in which a plurality of conductor layers that are laminated in a first direction and an insulation layer that is obtained by impregnating a glass fiber base material with a resin are laminated alternately; and a metal member that extends in the first direction. An end part of the multilayer wiring substrate that is opposite from the metal member is covered with a metal film. The metal film is electrically insulated from the plurality of conductor layers and electrically insulated from the metal member.

Description

Electrical device

[0001] The present invention relates to an electrical device.

[0002] Devices that handle electricity are required to meet various technical requirements. In Patent Document 1, a circuit board having an upper surface, a lower surface, and side surfaces, components mounted on the upper surface of the circuit board, a sealing portion provided on the upper surface of the circuit board and sealing the components and having an upper surface, a ground pattern provided on an outer peripheral portion of the lower surface of the circuit board, a top surface portion covering the upper surface of the sealing portion, a side surface portion extending from the top surface portion and covering the side surface of the circuit board, and a bottom surface portion extending from the side surface portion, provided on the ground pattern, and having a thickness that decreases as it moves away from the side surface portion, and a metal film having the same are disclosed.

[0003] International Publication No. 2010 / 103756

[0004] In the invention described in Patent Document 1, there is room for improvement from the viewpoint of suppressing migration.

[0005] An electrical device according to a first aspect of the present invention includes a multilayer wiring board in which a plurality of conductor layers laminated in a first direction and an insulating layer formed by impregnating a glass fiber base material with resin are alternately laminated, and a metal member extending in the first direction. An end portion of the multilayer wiring board facing the metal member is covered with a metal film, and the metal film is electrically insulated from the plurality of conductor layers and electrically insulated from the metal member.

[0006] According to the present invention, migration can be suppressed.

[0007] Cross-sectional view of an electrical device, cross-sectional view of a first comparative example electrical device, cross-sectional view of a second comparative example electrical device, cross-sectional view of an electrical device in a modified example

[0008] - First Embodiment - Hereinafter, a first embodiment of an electrical device will be described with reference to FIGS. 1 to 3.

[0009] Figure 1 is a cross-sectional view of the electrical device 1. The electrical device 1 comprises a multilayer wiring board 2, a cooler 3, and a metal housing 4. The metal housing 4 has a roughly C-shaped cross-section and houses the multilayer wiring board 2 and the cooler 3. Specifically, the metal housing 4 includes the left side 41, the bottom 42, and the right side 43. However, "left" for the left side 41 and "right" for the right side 43 are names used for convenience. The left side 41 and the right side 43 extend in the vertical direction shown in the figure (hereinafter referred to as the "first direction"), and the bottom 42 extends in the horizontal direction shown in the figure (hereinafter referred to as the "second direction").

[0010] The cooler 3 and the metal housing 4 are made of metal, and both can be called "metal components". The cooler 3 comprises an upper cooler 31, a lower cooler 32, and a water channel fixing member 33. The water channel fixing member 33 extends in a first direction, which is the vertical direction shown in the figure, and connects the upper cooler 31 and the lower cooler 32. Solder resist 51 is placed on the surface of the multilayer wiring board 2. The solder resist 51 at the bottom of the multilayer wiring board 2 is in contact with the lower cooler 32 via a heat dissipation sheet 52. The cooler 3 is fixed to the metal housing 4. The multilayer wiring board 2 is made by alternately laminating a plurality of conductor layers 21 that are stacked in a first direction and insulating layers 22 made by impregnating a glass fiber substrate with resin. However, different insulating layers 22 may be in contact with each other, so the conductor layers 21 and insulating layers 22 are not alternately laminated at all locations.

[0011] The multilayer wiring board 2 has through holes 23 that penetrate one or more insulating layers 22 in a first direction. The through holes 23 are a general term for general through holes 23A for connecting conductor layers 21 in different layers, and the through holes 23B that are not intended for connecting conductor layers 21. The through holes 23B are provided for the purpose of creating space for a metal member, i.e., a water channel fixing member 33, that penetrates the multilayer wiring board 2 in a first direction. Interlayer connection portions 21A for connecting conductor layers 21 are arranged on the side surface of the general through holes 23A. The side surface and edge of the through holes 23B are covered with a metal coating 24, which will be described later.

[0012] The edges of the multilayer wiring board 2 are covered with a metal coating 24. In Figure 1, the metal coating 24 is shown by dot hatching. The edges of the multilayer wiring board 2 include not only the position facing the left side surface 41 of the housing at the left end of the figure and the position facing the right side surface 43 of the housing at the right end of the figure, but also the left and right positions facing the water channel fixing material 33. Furthermore, the edges of the through holes 23 and the sides of the through holes 23 are also included in the edges of the multilayer wiring board 2. The metal coating 24 acts as a sealant, so to speak, to prevent moisture from entering the insulating layer 22.

[0013] A physical gap, or air gap, exists between the metal coating 24 and the metal components, specifically between the metal coating 24 and the left side surface 41 of the housing, the right side surface 43 of the housing, and the water channel fixing material 33, so they are not in close contact. Since air has insulating properties, it can be said that the metal coating 24 and the metal components are insulated by the air gap. Also, since air has a large insulating resistance, the resistance between the metal coating 24 and the metal components is greater than the insulating resistance between the metal coating 24 and the multiple conductor layers 21. Specifically, let Ra be the smallest resistance between the metal coating 24 and the metal components, and Rb be the smallest resistance between the metal coating 24 and the conductor layers 21. In this case, the relationship Ra > Rb holds, and current does not easily flow between the metal coating 24 and the metal components.

[0014] Furthermore, although the multilayer wiring board 2, which is an insulator, has a relatively low dielectric constant, it has a higher dielectric constant than air. In this embodiment, the capacitance between the metal film 24 and the metal member is smaller than the capacitance between the metal film 24 and the multiple conductor layers 21. Specifically, let the capacitance between the metal film 24 and the metal member be Ca, and the capacitance between the metal film 24 and the conductor layer 21 be Cb. In this case, the relationship Ca < Cb holds, and current does not easily flow between the metal film 24 and the metal member.

[0015] (Comparative Example 1) Figure 2 is a cross-sectional view of the first comparative example, the first comparative example electrical device 1Z1. The difference between the first comparative example electrical device 1Z1 and electrical device 1 is the presence or absence of the metal coating 24. The first comparative example electrical device 1Z1 does not have the metal coating 24 at any of the ends of the multilayer wiring board 2, specifically at the position facing the left side surface 41 of the housing at the left end of the figure, the position facing the right side surface 43 of the housing at the right end of the figure, and the left and right positions facing the water channel fixing material 33. At these positions, in addition to the electric field concentration at the ends of the conductors, the surface is rough due to drilling, making it susceptible to moisture absorption from the glass fiber and resin interface. Therefore, migration may occur due to the intrusion of moisture, as indicated by reference numeral 901. In contrast, in the electrical device 1 of this embodiment, the ends of the multilayer wiring board 2 are covered with the metal coating 24, so that moisture intrusion is prevented and migration is suppressed.

[0016] (Comparative Example 2) Figure 3 is a cross-sectional view of the second comparative example, the electrical device 1Z2. The difference between the electrical device 1Z2 and the electrical device 1 is the gap between the metal coating 24 and the metal member. When the water channel fixing material 33 and the metal coating 24 are electrically connected, a high voltage may be applied between the conductor layer 21 and the metal coating 24, and migration may occur between the metal coating 24 and the conductor layer 21 as indicated by reference numeral 902. In contrast, in the electrical device 1 of this embodiment, an air gap is provided between the metal coating 24 and the metal member, so that the application of voltage is prevented and migration is suppressed.

[0017] According to the first embodiment described above, the following effects can be obtained. (1) The electrical device 1 comprises a multilayer wiring board 2 in which a plurality of conductor layers 21 stacked in a first direction which is the vertical direction shown in the figure, and an insulating layer 22 made by impregnating a glass fiber substrate with resin, are alternately stacked, and a metal member extending in the first direction, namely a cooler 3 and a metal housing 4. The ends of the multilayer wiring board 2 facing the water channel fixing member 33, the left side surface 41 of the housing, and the right side surface 43 of the housing, which are metal members, are covered with a metal coating 24. The metal coating 24 is electrically insulated from the plurality of conductor layers 21, and is also electrically insulated from the water channel fixing member 33, the left side surface 41 of the housing, and the right side surface 43 of the housing. Therefore, moisture absorption from the interface between the glass fibers and resin constituting the insulating layer 22 is prevented, and the potential between the metal coating 24 and the conductor layers 21 is reduced, thereby preventing migration.

[0018] (2) The left side surface 41 and the right side surface 43 of the housing are part of the metal housing 4 that houses the multilayer wiring board 2.

[0019] (3) The multilayer wiring board 2 has the through hole 23B that penetrates in the first direction. The water channel fixing material 33, which is a metal member, is inserted into the through hole 23B. The ends of the multilayer wiring board 2 that are covered with the metal coating 24 are the edges of the through hole 23B and the sides of the through hole 23B.

[0020] (4) The metal coating 24 and the metal member are electrically insulated through an air gap.

[0021] (5) The resistance between the metal coating 24 and the metal member is greater than the insulation resistance between the metal coating 24 and the multiple conductor layers 21. Therefore, the voltage generated between the metal coating 24 and the metal member can be reduced, and migration can be suppressed.

[0022] (6) The capacitance between the metal coating 24 and the metal member is smaller than the capacitance between the metal coating 24 and the multiple conductor layers 21. Therefore, the voltage generated between the metal coating 24 and the metal member can be reduced, and migration can be suppressed.

[0023] (Modification 1) It is not essential that the multilayer wiring board 2 has both a general through-hole 23A and the through-hole 23B in question; it may have only one of them, or neither. The electrical device 1 is equipped with a cooler 3 and a metal housing 4, which are metal components. However, the electrical device 1 only needs to be equipped with at least one of the cooler 3 and the metal housing 4. If the electrical device 1 is not equipped with a cooler 3, the multilayer wiring board 2 will not have the through-hole 23B in question, and the metal coating 24 on the multilayer wiring board 2 will be formed at a position facing the left side surface 41 of the housing and at a position facing the right side surface 43 of the housing. Also, if the electrical device 1 is not equipped with a metal housing 4, for example, if a non-metallic housing is used, or if no housing is used at all, the metal coating 24 on the multilayer wiring board 2 will be formed at a position facing the water channel fixing material 33 in the through-hole 23B in question.

[0024] (Modified Example 2) Figure 4 is a cross-sectional view of the electrical device 1 in Modified Example 2. In the first embodiment described above, the metal coating 24 and the metal member were electrically insulated by an air gap. However, an insulating resin 29 may be placed between the metal coating 24 and the metal member. By placing the insulating resin 29, the metal coating 24 and the metal member can be stably insulated.

[0025] According to this modified example, the following effects can be obtained: (7) The metal coating 24 and the metal member are electrically insulated via the insulating resin 29. Therefore, the metal coating 24 and the metal member can be stably insulated, and migration is suppressed. In this modified example, the insulating resin 29 is placed at all four locations between the metal coating 24 and the metal member, but it is not essential to place the insulating resin 29 at all four locations, and the insulating resin 29 may be placed at only some locations.

[0026] (Modification 3) In the first embodiment described above, an air gap existed between the metal film 24 and the metal member. However, the metal film 24 and the metal member may be in close contact via an insulating resin. Also, when the smallest resistance value between the metal film 24 and the metal member is Ra, and the smallest resistance value between the metal film 24 and the conductor layer 21 is Rb, the relationship Ra > Rb holds, but Ra < Rb is also acceptable. Furthermore, when the capacitance between the metal film 24 and the metal member is Ca, and the capacitance between the metal film 24 and the conductor layer 21 is Cb, the relationship Ca < Cb holds, but Ca > Cb is also acceptable.

[0027] The embodiments and modifications described above may be combined in any way. Although various embodiments and modifications have been described above, the present invention is not limited to these. Other embodiments that can be conceivable within the scope of the technical idea of ​​the present invention are also included within the scope of the present invention.

[0028] 1: Electrical device 2: Multilayer wiring board 3: Cooler 4: Metal housing 21: Conductor layer 21A: Interlayer connection part 22: Insulating layer 23B: Through hole in this case 24: Metal coating 29: Insulating resin 33: Water channel fixing material 41: Left side of housing 43: Right side of housing

Claims

1. An electrical device comprising: a multilayer wiring board in which a plurality of conductor layers stacked in a first direction and an insulating layer made of a glass fiber substrate impregnated with resin are alternately stacked; and a metal member extending in the first direction, wherein the end of the multilayer wiring board facing the metal member is covered with a metal film, and the metal film is electrically insulated from the plurality of conductor layers and from the metal member.

2. An electrical device according to claim 1, wherein the metal member is a metal housing that houses the multilayer wiring board.

3. An electrical device according to claim 1, wherein the multilayer wiring board has through holes penetrating in the first direction, the metal member is inserted into the through holes, and the end is the edge of the through holes and the side of the through holes.

4. An electrical device according to claim 1, wherein the metal coating and the metal member are electrically insulated from each other via an air gap or an insulating resin.

5. An electrical device according to claim 1, wherein the resistance value between the metal coating and the metal member is greater than the insulation resistance value between the metal coating and the plurality of conductor layers.

6. An electrical device according to claim 1, wherein the capacitance between the metal film and the metal member is smaller than the capacitance between the metal film and the plurality of conductive layers.

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