JPS63175494A - Molded printed wiring board - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application J] The present invention relates to a molded printed wiring board for configuring electronic circuits and the like.

``Prior Art J'' As shown in FIG. 4, a typical printed wiring board is one in which a conductor 3 with a thickness of about 35 JLm is provided on a substrate 1 with an adhesive layer 2 interposed therebetween.

In addition, as a molded printed wiring board, there is an invention disclosed in Japanese Patent Application Laid-open No. 80-121791, and in the case of this published invention, as shown in FIG. It's embedded.

"Problem to be Solved by the Invention J In the printed wiring board shown in Figure 4, in order to increase the mounting efficiency of circuit components by providing many conductors 3 on the board 1, or to configure a complex circuit, the board surface area is It is best to make the space factor (conductor pattern width) of the conductor 3 as small as possible, specifically increasing the thickness of the conductor 3 and reducing the width of the conductor 3, but in the case of a power circuit that flows a large current. In this case, since the cross-sectional area of the conductor 3 is increased, the pattern width of the conductor 3 inevitably becomes larger, and accordingly, the substrate tends to become larger.

In the case of the molded printed wiring board shown in FIG. 5, in addition to the same problems as above, when an external force acts on the board 11, there is a risk that the conductor 12 embedded in the board 11 may escape. .

In view of the above-mentioned problems, the present invention aims to provide a molded printed wiring board that is small in size, allows a large current to flow, and has a high bonding strength between the board and the conductor.

Means for Solving Problems J In order to achieve the intended purpose, the molded printed wiring board according to the present invention includes a conductor having a substantially tapered cross section, the lower part of which is larger than the upper part, embedded in the board. It is characterized in that the upper surface of the conductor is exposed to the surface of the substrate.

1 Effect J As described above, the molded printed wiring board of the present invention has a conductor with a substantially tapered cross section embedded in the board, and the upper surface of the conductor is exposed on the surface of the board. The conductor embedding structure is a so-called dovetail fitting, in which the width of the upper part of the conductor (conductor pattern width) is small and the cross-sectional area of the conductor is large.

Therefore, in the case of the molded printed wiring board according to the present invention, the conditions for miniaturization such as reducing the space factor of the conductor with respect to the surface area of the board, and the conditions for passing large current by increasing the cross section of the conductor are simultaneously satisfied, and the above-mentioned conditions are satisfied simultaneously. Dovetail fitting also increases the bonding strength between the substrate and the conductor. 'Example J Hereinafter, an example of a molded printed wiring board according to the present invention will be described with reference to the drawings.

In FIG. 1 showing an embodiment of a molded printed wiring board according to the present invention, 31 is a molded resin substrate, 41 is a metal conductor embedded in the substrate 31, and 51 is also a metal conductor embedded in the substrate 31. It is a metal conductor embedded in the substrate 31.

In one conductor 41 in the above, the width of the lower part 42 is equal to the width of the upper part 41.
3, and its cross-sectional shape is approximately tapered, but there is a constricted part 44 on the upper part 43 side of the conductor 41.
is formed, and the upper surface of the conductor is exposed on the substrate 31 so that it is at the same level as the surface of the substrate 31.

Furthermore, the conductor 41 also has a side edge portion 45 that is generated when forming the conductor.

The other conductor 51 described above has a thin rectangular cross section, and the conductor surface of the conductor 51 is exposed to the surface of the substrate 31 when it is embedded in the substrate 31.

Thus, the molded printed wiring board of the present invention in which the conductors 41 and 51 are embedded in the substrate 31 includes appropriate circuit components 6.
1 are mounted interconnected with these conductors 41, 51.

Note that the conductor 51 may also have a substantially tapered cross section like the conductor 41, or the conductor 51 may be omitted.

Next, an example of manufacturing a molded printed wiring board according to the present invention will be described with reference to FIGS. 2 and 3.

Initially, a thick copper plate was used for the conductor 41, and a conductor 5 was used.
A transfer sheet is constructed by laminating a copper plate with a small thickness to a releasable base sheet, and the copper plate of the transfer sheet is chemically etched to form conductors 41 and 51, respectively.
form.

FIG. 2 shows the transfer sheet after the above-mentioned etching process, with each conductor 41.5 on the surface of the base sheet 71.
1 is left.

Note that during this etching, the side edge portion 45 mentioned above
occurs.

Next, the etched transfer sheet is loaded into an injection mold (mold), and a resin serving as a molding material is injected into the mold to mold the substrate 31. At the same time, each conductor is inserted into the substrate 31. Embed 41.51.

Below, when the transfer sheet is taken out from the mold together with the substrate 31 and the base sheet 71 is peeled off from the surface of the substrate 31, each conductor 41.51 attached to the base sheet 71 is removed.
is transferred onto the substrate 31.

In this way, a molded printed wiring board as shown in FIG. 3 is obtained.

As described in FIG.
will be installed.

r Effects of the Invention J As explained above, in the molded printed wiring board according to the present invention, a conductor having a substantially tapered cross section is embedded in the board in a predetermined direction, and the narrow upper surface of the conductor is on the surface of the board. Because it is exposed, it simultaneously satisfies the requirements for making the wiring board high-density and compact, as well as enabling the passage of large currents for power circuits, and also improves the bonding strength between the board and the conductor. It can also increase

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing one embodiment of a molded printed wiring board according to the present invention, FIGS. 2 and 3 are cross-sectional views showing the manufacturing status of the molded printed wiring board according to the present invention, and FIG. , FIG. 5 is a sectional view showing a conventional printed wiring board. 31... Board 41... Φ conductor 42... Lower part of the conductor 43Φ, Upper part of the conductor 44... Narrow part of the conductor

Claims (2)

[Claims] (1) A mold printed wiring board characterized in that a conductor having a substantially tapered cross section with a lower portion larger than an upper portion is embedded in a substrate, and the upper surface of the conductor is exposed on the surface of the substrate. (2) The molded printed wiring board according to claim 1, wherein a constricted portion is formed on the upper side of the conductor.