JPH05121852A - Metal core wiring board provided with through hole - Google Patents

Abstract

PURPOSE:To raise the dielectric withstand voltage between the wiring conductor and the metallic plate at the through hole part of a board. CONSTITUTION:At least three sheets of metallic boards 1 in piles are used for this wiring board, and the more inside the metallic plate is, each individual metallic board has the smaller through hole in diameter. Insulators 2 are made on the surface and the rear of the set of these metallic plates 1a, 1b, and 1c and inside the through hole, and the conductor wirings at the surface and the rear are connected electrically through the through hole 4. Hereby, the thickness of the insulator 2 of the through hole 4 can be secured, and the dielectric withstand voltage can be raised.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a metal core wiring board with through holes, and more particularly to a metal core wiring board with through holes in which the electrical characteristics of the through holes are improved.

[0002]

2. Description of the Related Art FIG. 3 shows the structure of a conventional metal core wiring board with through holes. A conventional metal core wiring board with through holes has a metal plate 1 whose corners are chamfered in a vertical cross section of the through hole, an insulator 2 formed on the front and back surfaces of the metal plate 1, and inside the through hole, and a surface of the insulator 2. And a conductor wiring 3 on the back surface and a through hole 4 for electrically connecting the conductor wiring 3 on the front surface and the back surface.

This metal core wiring board with through holes is manufactured as follows. First, a metal plate such as an iron plate is pressed to form its outer shape. At this time, through holes are also formed at the same time. Next, a dedicated metal mold is used to press or a drill is used to chamfer the corners of the through holes. Outside corners of metal sheets are also chamfered at the same time. Then, the powder of the inorganic insulator is dissolved in, for example, a solvent of isopropyl alcohol, the metal plate is immersed in the solution charged with the particles of the powder, and the surface of the metal plate, the back surface, and the inside of the through hole are electrophoresed. Attach an insulator, for example,
Baking at 900 ° C. for 1 hour forms an insulator having a thickness of 100 to 200 μm. Further, using a screen printing method or the like on the insulator, for example, a thick film conductor of silver platinum is formed on the surface,
It is formed on the back surface and inside the through hole.

In the conventional metal core substrate with through holes, the corners of the through holes are chamfered in order to secure the thickness of the insulating layer in the through holes. Due to the nature of the electrophoresis method, the insulator does not easily adhere to the narrow portion inside the through hole, and the insulator softens and flows during firing at 900 ° C. for 1 hour, so the edge of the through hole portion It compensates for the tendency to become thinner. At the edge of the through-hole portion, the thickness of the insulator is usually 1/2 to 1/4 as compared with the flat portion on the front surface or the back surface. For example, the thickness of the through hole was 30 to 60 μm when the flat part was 120 μm, and the through hole was thin, and the low dielectric strength part was 200 VAC.

[0005]

In this conventional metal core substrate with through holes, the corners of the through holes of the metal plate are chamfered by using a press or a drill using a dedicated mold. As for the shape, the insulator thickness of the through hole portion could not be sufficiently secured, in other words, there was a thin portion of the insulator in the through hole portion. Therefore, there is a problem that the insulation withstand voltage between the through hole portion and the metal plate is insufficient. An object of the present invention is to solve the above problems and to provide a metal core wiring board with a through hole in which a sufficient withstand voltage between the through hole portion and the metal plate is secured.

[0006]

In order to achieve the above-mentioned object, a metal core wiring board with a through hole according to the present invention has an insulator portion formed around a metal plate portion having a through hole, and a surface of the insulator portion. A metal core wiring board with a through hole having a wiring conductor portion formed on the back surface and a through hole conductor portion for connecting the wiring conductor portion on the front surface and the wiring conductor portion on the back surface through the through hole, wherein the metal plate portion is at least a metal plate. Are stacked, and the diameters of the through holes of the individual metal plates are made smaller toward the inside of the stacked metal plates.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in more detail below with reference to the drawings. FIG. 1A is a plan view showing an embodiment of a metal core wiring board with through holes according to the present invention. A cross section AA is shown in FIG. Metal plate is metal plate 1
It is used by stacking three sheets a, 1b and 1c. The metal plates 1a and 1c are the same. Plate thickness 0.25 mm
The ultra-low carbon steel plate of No. 2 has a through hole with a diameter of 1.2 mm. The metal plate 1b is a very low carbon steel plate having a plate thickness of 0.25 mm and a through hole having a diameter of 0.8 mm is formed in the metal plate 1b.
Position the through holes so that they are in between and stack them, and attach the three pieces by spot welding to prevent misalignment.

Next, a powder of an inorganic insulator containing MgO or the like as a component is dissolved in a solvent of isopropyl alcohol, the metal plate is immersed in a solution in which particles of the powder are charged, and the surface of the metal plate is electrophoresed. The insulator 2 was attached to the back surface and the inside of the through hole, and baked at 900 ° C. for 1 hour to form an insulator with a thickness of about 120 μm. At this time, the hole diameter of the through hole 4 was 0.5 mm. Next, the front surface and the back surface are screen-printed while sucking the through hole portion, and the front surface and the back surface wiring form electrical connection in the conductor wiring 3 and the through hole 4.

With such a structure, the insulator in the central portion of the through hole becomes thicker in the past, and therefore the edge portion of the through hole becomes thinner, whereas the hole diameter becomes smaller in the central portion of the through hole. It is probable that the insulator did not become thicker in the central portion, so that the through-hole edge portion did not become thinner and the through-hole insulator thickness was made uniform. As a result, it becomes possible to secure a thickness of 50 to 80 μm in the through hole portion even in a thin portion with respect to the thickness of the insulating layer of 120 μm in the flat portion on the front surface or the back surface, and the dielectric strength is at least 500 VAC.
I was able to

FIG. 2A is a plan view showing another embodiment of the present invention. FIG. 2B is a sectional view taken along line BB. The third embodiment differs from the first embodiment only in that the corners of the three stacked metal plates 1d, 1e, 1f are chamfered, and other configurations and manufacturing methods are the same. As a method of chamfering corners, pressing is performed using a die for each individual metal plate. As a result, the vertical cross-sectional shape of the through hole is made smoother than that of the first embodiment.
The thickness of the insulator in the through hole was made more uniform.
The thickness of the insulating layer is 120 μm in the flat surface portion of the front surface or the back surface, and 70 to 80 even in the thin portion in the through hole portion.
It becomes possible to secure μm, and the insulation withstand voltage is at least 8
It was possible to set it to 00 VAC.

[0011]

As described above, according to the present invention, at least three stacked metal plates are used, and the inner diameter of the stacked metal plates is such that the through holes of the individual metal plates have smaller diameters. There is an effect that the thickness of the insulator in the through hole portion can be sufficiently secured, and the withstand voltage between the conductor wiring and the metal plate in the through hole portion can be increased.

[Brief description of drawings]

1A is a plan view showing an embodiment of a metal core substrate with through holes according to the present invention, and FIG. 1B is a sectional view taken along line AA.

2A is a plan view showing another embodiment of the present invention, FIG.
(B) is a BB sectional view.

3A is a plan view showing an example of a conventional metal core substrate with through holes, and FIG. 3B is a sectional view taken along line CC.

[Explanation of symbols]

 1, 1a to f ... Metal plate 2 ... Insulator 3 ... Conductor wiring 4 ... Through hole

Claims (2)

[Claims] 1. An insulator part formed around a metal plate part having a through hole, a wiring conductor part formed on a front surface and a back surface of the insulator part, and a wiring conductor part formed on the front surface and the back surface through the through hole. In a metal core wiring board with a through hole having a through-hole conductor portion for connecting wiring conductor portions, the metal plate portion is formed by stacking at least three metal plates, and each metal plate is closer to the inside of the stacked metal plates. A metal core wiring board with a through hole, characterized in that the diameter of the through hole is reduced. 2. The metal core wiring board with a through hole according to claim 1, wherein each of said at least three stacked metal plates is chamfered at each corner.