Substrate unit, fixing structure for substrate unit and precursor substrate for substrate units

Abstract

To provide a substrate unit 1 capable of shielding an electronic component 222 even if a metal case is omitted.SOLUTION: The substrate unit 1 comprises: a mounting substrate 2 in which the electronic component 222 is mounted on a rear face of a printed wiring board 21; a frame-shaped insulation plate 3 which covers a peripheral part 23 of a rear face of the mounting substrate 2; and an insulation shield plate 4 which covers the entire rear face of the mounting substrate 2 via the insulation plate 3. A first shield pattern 212 is formed on the mounting substrate 2. A second shield pattern 321 conducted with a first through hole 213 of the first shield pattern 212 is formed on the insulation plate 3. A third shield pattern 411 conducted with a second through hole 322 of the insulation plate 3 and opposed to the electronic component 222 on the rear face of the mounting substrate 2 is formed on the insulation shield plate 4. The electronic component 222 is stored and shielded in an inner peripheral space of the insulation plate 3 while being held between the first shield pattern 212 and the third shield pattern 411.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a substrate unit having a mounting board in which electronic components are mounted on at least the back surface circuit pattern of a printed wiring board, a fixing structure for the substrate unit, and a precursor substrate for the substrate unit. [Background technology]

[0002] In recent years, various electronic devices have been using substrate units having a mounting board on which multiple electronic components are mounted to drive the electronic devices (see, for example, Patent Document 1). To block external noise and electrical noise generated by the mounted electronic components themselves, these devices generally have a metal case that covers the electronic components and is partially connected to a ground terminal on the printed wiring board as a shield. As electronic devices become smaller, substrate units are also required to be smaller, and it is desirable to miniaturize the metal case as well. However, when a substrate unit is installed near a high-voltage element (e.g., IGBT, FET, etc.) or a metal housing, it is necessary to ensure a sufficient insulation distance between the substrate unit and the metal case, which limits the miniaturization of the metal case. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-344812 Summary of the Invention [Problem to be solved by the invention]

[0004] In view of the above, an object of the present invention is to provide a substrate unit, a fixing structure for the substrate unit, and a precursor substrate for the substrate unit that can shield electronic components even if a metal case is omitted. [Means for solving the problem]

[0005] In order to solve the above-mentioned problems, the substrate unit of the present invention has a mounting substrate on which electronic components are mounted on at least the circuit pattern on the back surface of the circuit patterns on the front and back surfaces of a printed wiring board. The substrate unit includes a frame-shaped insulating plate that covers the peripheral portion of the back surface of the mounting substrate, and an insulating shield plate that covers the entire back surface of the mounting substrate via the insulating plate, wherein the mounting substrate has a first shield pattern formed thereon with a plurality of first through holes that penetrate from the front to the back, the insulating plate has a second shield pattern formed thereon with a plurality of second through holes that penetrate from the front to the back and that are electrically connected to each of the first through holes in the first shield pattern, and the insulating shield plate has a third shield pattern formed thereon that is electrically connected to the second through holes that are opened in the insulating plate and that faces the electronic components protruding from the back surface of the mounting substrate, and the electronic components are sandwiched between the first shield pattern and the third shield pattern and are thereby housed in the inner space of the insulating plate and shielded.

[0006] According to the present invention, electronic components can be shielded even if the conventional metal case for shielding is omitted.

[0007] The fixing structure of the present invention is a fixing structure for a board unit that fixes the board unit to a metal housing or a high-voltage element, and is characterized in that the mounting board is fastened to the metal plate or high-voltage element that constitutes the metal housing via the insulating plate and the insulating shield plate. With this, the presence of the insulating plate and the insulating shield plate makes it possible to ensure an insulation distance between the mounting board and the metal plate or high-voltage element.

[0008] Furthermore, in the precursor substrate for a substrate unit used to fabricate a substrate unit of the present invention, the mounting substrate, the insulating plate, and the insulating shield plate have the same external shape, and the mounting substrate, the insulating plate, and the insulating shield plate are aligned and defined on a single precursor substrate, and dividing sections that can be divided by bending are formed at the boundaries between each of the mounting substrate, the insulating plate, and the insulating shield plate and adjacent plates. This allows the mounting substrate, the insulating plate, and the insulating shield plate to be fabricated by bending and dividing a single precursor substrate, thereby reducing the manufacturing cost of the substrate unit. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is an exploded perspective view showing an embodiment of a substrate unit of the present invention from the front side; [Figure 2] FIG. 2 is an exploded perspective view showing an embodiment of a substrate unit of the present invention from the rear side. [Figure 3] FIG. 3 is an enlarged cross-sectional view of a substrate unit according to the present invention. [Figure 4] FIG. 1 is a perspective view showing an embodiment of a precursor substrate for producing a substrate unit of the present invention. [Figure 5] 2 is a perspective view showing an embodiment of a fixing structure of a substrate unit of the present invention for fixing the substrate unit shown in FIG. 1 to a high-voltage element. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0010] 1 to 3, the board unit 1 of this embodiment includes a mounting board 2 having electronic components 221, 222 mounted on circuit patterns 211, 212 on the front and back surfaces of a printed wiring board 21, a frame-shaped insulating plate 3 covering a peripheral portion 23 on the back surface of the mounting board 2, and an insulating shield plate 4 covering the entire back surface of the mounting board 2 via the insulating plate 3.

[0011] The printed wiring board 21 has a rectangular plate shape, and the circuit pattern 211 on the front surface consists of a circuit 211a extending linearly in the longitudinal direction of the printed wiring board 21 and a circuit 211b formed to surround the circuit 211a. The circuit pattern 212 on the back surface consists of a circuit 212a extending in the longitudinal direction of the printed wiring board 21 and a circuit 212b formed to surround the circuit 212a. In this embodiment, the circuit pattern 212 constitutes a first shield pattern. The circuits 211a, 211b, 212a, and 212b are made of a metal film such as copper and are connected to a ground potential. A plurality of first through holes 213 are formed on both ends of the circuit 211b perpendicular to the longitudinal direction, penetrating the printed wiring board 21 from front to back. Each of the first through holes 213 is electrically connected to a second through hole 322 in the insulating plate 3, which will be described later. In this embodiment, the circuit pattern 212 is connected to the ground potential, but the present invention is not limited to this. For example, the circuit pattern 212 may be connected to a floating potential of a metal housing or the like.

[0012] The electronic components 221 mounted on the circuit pattern 211 of the printed wiring board 21 are multiple capacitors 5, each of which has a body 51 and a pair of leads 52. The capacitors 5 are spaced apart in the longitudinal direction of the circuits 211a and 211b, and one lead 52 of each capacitor 5 is connected to both the circuit 211a and the circuit 212a located on the back side of the circuit 211a. The other lead 52 of each capacitor 5 is connected to both the circuit 211b and the circuit 212b located on the back side of the circuit 211b. The printed wiring board 21 has multiple through holes (not shown) formed therein so that the leads 52 can pass through from the front to the back. Each lead 52 is bent and inserted through the through hole and soldered to the circuits 212a and 212b, thereby fixing all of the capacitors 5 to the printed wiring board 21. Electronic components 222 mounted on circuit pattern 212 on the back surface of printed wiring board 21 are multiple semiconductor chips 6, and each semiconductor chip 6 is bridged and connected between circuits 212a and 212b and fixed to printed wiring board 21. Each semiconductor chip 6 also protrudes from the back surface of mounting board 2.

[0013] The insulating plate 3 has the same outer shape as the printed wiring board 21, a frame-like shape corresponding to the peripheral portion 23 on the back surface of the mounting board 2, and an inner circumferential space 31 surrounded by the frame-like portion. The insulating plate 3 has circuit patterns 321, 321 formed as second shield patterns at the inner edge portions on both sides along the longitudinal direction of the inner circumferential space 31. The circuit patterns 321, 321 are made of a metal film such as copper, and have a plurality of second through holes 322 penetrating the insulating plate 3 from front to back. The inner circumferential space 31 of the insulating plate 3 can be formed by router processing or the like. In this embodiment, two insulating plates 3, 3 are stacked together to prevent the semiconductor chips 6 mounted on the circuit pattern 212 on the back surface of the printed wiring board 21 and protruding from the back surface of the mounting board 2 from contacting the insulating shield plate 4 (see FIG. 3 in particular). In this embodiment, an example in which two insulating plates 3, 3 are overlapped will be described, but the number of insulating plates 3 to be overlapped can be determined appropriately depending on the size of the electronic component 222 to be mounted on the back surface of the mounting substrate 2 and the thickness of the insulating plates 3.

[0014] The insulating shield plate 4 has the same external shape as the printed wiring board 21, and on its surface (i.e., the surface facing each semiconductor chip 6 mounted on the back surface of the mounting board 2) is formed a circuit pattern 411 as a third shield pattern. The circuit pattern 411 is made of a metal film such as copper having the same contour as the circuit pattern 212, and is electrically connected to the second through-hole 322 opened in the insulating plate 3.

[0015] In this embodiment, connecting holes 7 penetrating the front and back surfaces are provided at the four corners of each of the mounting substrate 2, insulating plate 3, and insulating shield plate 4. When one insulating plate 3 is superimposed on the peripheral portion 23 of the back surface of the mounting substrate 2 and the insulating shield plate 4 is superimposed on the other insulating plate 3, the connecting holes 7 communicate with each other in the front-to-back direction of the substrate unit 1. In this embodiment, when the mounting substrate 2, insulating plates 3, 3, and insulating shield plate 4 are superimposed as described above, each semiconductor chip 6 protruding from the back surface of the mounting substrate 2 is sandwiched between the circuit pattern 212 and the circuit pattern 411 and is housed in the inner peripheral space 31 of the insulating plate 3 for shielding. Therefore, according to this embodiment, each semiconductor chip 6 can be shielded even if a metal case for shielding is omitted.

[0016] Next, with reference to FIG. 4, a substrate unit precursor substrate 8 (hereinafter simply referred to as "precursor substrate 8") for producing the substrate unit 1 will be described.

[0017] The mounting substrate 2, the two insulating plates 3, 3, and the insulating shield plate 4 are formed from a precursor substrate 8. The precursor substrate 8 is a long plate material, and the two insulating plates 3, 3 are defined side by side in the longitudinal direction, and the mounting substrate 2 and the insulating shield plate 4 are defined side by side in the lateral direction, adjacent to each insulating plate 3. In addition, V-shaped grooves 81 are engraved in the precursor substrate 8 at the boundaries between the mounting substrate 2, the insulating plates 3, 3, and the insulating shield plate 4 as dividing sections. The precursor substrate 8 is bent along the V-shaped grooves 81 and then pressed and broken to obtain the mounting substrate 2, the two insulating plates 3, 3, and the insulating shield plate 4. The precursor substrate 8 is generally formed by impregnating a non-folded fabric made of glass cloth, carbon fiber, or the like with a thermoplastic resin such as polypropylene or a thermosetting resin such as epoxy resin, and then curing the impregnated material. According to this embodiment, one precursor substrate 8 can be bent and divided at the V-groove 81 to produce a mounting substrate 2, two insulating plates 3, 3, and an insulating shield plate 4, thereby reducing the manufacturing cost of the substrate unit 1.

[0018] Next, with reference to FIG. 5, a fixing structure for fixing the substrate unit 1 to the high-voltage element 9 will be described.

[0019] In the fixing structure of the board unit 1 of this embodiment, an insulating shield plate 4 is placed on a high-voltage element 9 such as an IGBT or FET. Two insulating plates 3, 3 are placed on the insulating shield plate 4, and the mounting board 2 is placed with the peripheral portion 23 of its rear surface overlapping the insulating plate 3. At this time, connecting holes 7 formed at the four corners of the mounting board 2, each of the insulating plates 3, 3, and the insulating shield plate 4 communicate the board unit 1 from front to back. Furthermore, the semiconductor chip 6 protruding from the rear surface of the mounting board 2 is sandwiched between the circuit pattern 212 and the circuit pattern 411 and is housed in the inner peripheral space 31 of the insulating plate 3 for shielding. Then, screws 10 are threaded into the high-voltage element 9 from the mounting board 2 side through the connecting holes 7, thereby fixing the board unit 1 to the high-voltage element 9. According to this embodiment, the insulating plates 3, 3 and the insulating shield plate 4 are present between the mounting board 2 and the high-voltage element 9, ensuring an insulation distance between the mounting board 2 and the high-voltage element 9. In this embodiment, the description will be made taking an example of fixing to the high voltage element 9, but it can also be fixed to a metal plate in a metal casing in the same way.

[0020] Although the embodiments of the present invention have been described above, the present invention is not limited to these. For example, various embodiments are possible for the configuration and structure of printed wiring board 21, the shapes and materials of circuit patterns 211 and 212 on the front and back surfaces, the types of electronic components 221 and 222 to be mounted, the configuration, structure and materials of insulating plate 3 and insulating shield plate 4, and the shape and material of circuit pattern 411 on the front surface. Furthermore, insulating plate 3 and insulating shield plate 4 may be made of different materials, and insulating plate 3 and insulating shield plate 4 may have different thicknesses.

[0021] In addition, in the above embodiment, an example was described in which circuit patterns 321, 321 and multiple second through holes 322 are provided on the periphery of the inner space 31 of the insulating plates 3, 3, but the number and opening positions of the second through holes 322 are not limited to this as long as they can provide electrical conductivity between the circuit pattern 212 of the mounting board 2 and the circuit pattern 411 of the insulating shield plate 4. [Explanation of symbols]

[0022] 1...board unit, 2...mounting board, 21...printed wiring board, 211...circuit pattern, 212...first shield pattern (circuit pattern), 213...first through hole, 222...electronic component (semiconductor chip), 23...periphery, 3...insulating plate, 321...second shield pattern (circuit pattern), 322...second through hole, 4...insulating shield plate, 411...third shield pattern (circuit pattern), 8...precursor substrate for board unit, 81...dividing portion (V-groove), 9...high-voltage element.

Claims

1. A substrate unit having a mounting substrate in which electronic components are mounted on at least the circuit pattern on the back surface of a printed wiring substrate, a frame-shaped insulating plate that covers a peripheral portion of a rear surface of the mounting substrate, and an insulating shield plate that covers the entire rear surface of the mounting substrate via the insulating plate; A first shield pattern is formed on the mounting board, the first shield pattern having a plurality of first through holes penetrating the mounting board in a front-to-back direction; A second shield pattern is formed on the insulating plate, the second shield pattern having a plurality of second through holes penetrating the insulating plate in a front-to-back direction and electrically connected to the first through holes of the first shield pattern; the insulating shield plate is electrically connected to the second through hole formed in the insulating plate and is provided with a third shield pattern facing the electronic components protruding from the rear surface of the mounting board; The board unit is characterized in that the electronic component is housed in an inner peripheral space of an insulating plate so as to be sandwiched between a first shield pattern and a third shield pattern, and is shielded.

2. A fixing structure for a board unit according to claim 1, for fixing the board unit to a metal housing or a high-voltage element, comprising: A fixing structure for a board unit, characterized in that the mounting board is fastened to a metal plate constituting a metal casing or a high-voltage element via the insulating plate and the insulating shield plate.

3. A precursor substrate for a substrate unit for producing the substrate unit according to claim 1, a precursor substrate for a substrate unit, characterized in that the mounting substrate, the insulating plate and the insulating shield plate have the same external shape, the mounting substrate, the insulating plate and the insulating shield plate are arranged side by side on a single precursor substrate, and dividing portions that can be divided by bending are formed at the boundaries between each of the mounting substrate, the insulating plate and the insulating shield plate and each of the adjacent plates.

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