JPH0955582A - Production of thick circuit board buried with conductor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress irregularities on the surface by laminating a thick conductor pattern and a prepreg pattern having a prepreg to be fitted in the cavity in combination. SOLUTION: A thick conductor pattern 1 having a thick conductor 1a formed into a required circuit pattern is combined with a prepreg pattern 5 having a prepreg 5a to be fitted in the cavity. It is then applied, on one or both sides with a prepreg sheet 2 and hot pressed. For example, the thick conductor pattern 1 comprises a thick conductor 1a punched or cut from a copper plate into a desired circuit pattern, a surrounding fringe frame 1c, and a conductor bridge 1b formed between adjacent thick conductors 1a and between the thick conductor 1a and the fringe frame 1c, formed integrally.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a thick-walled conductor-embedded circuit board in which a thick-walled conductor for large current is embedded in an insulating substrate.

[0002]

2. Description of the Related Art A general example of a conventional method for manufacturing a thick-walled conductor-embedded circuit board is shown in FIG. First, the thick conductor pattern 1 having the thick conductor 1a formed in a required circuit pattern is prepared. The thick conductor pattern 1 is usually manufactured by punching or cutting a copper plate into a shape in which adjacent thick conductors 1a are positioned by a conductor bridge (not shown).

Next, a required number of prepreg sheets 2 (a glass cloth impregnated with a thermosetting resin and semi-cured) are laminated on both sides of the thick conductor pattern 1, and further copper foil 3 is laminated on the outer side thereof. , Pressurize and heat with hot press,
Integrate the whole. After that, the copper foil 3 is pattern-etched to form a circuit pattern for a small current (signal), and a portion corresponding to the conductor bridge of the thick conductor pattern 1 is drilled to cut the conductor bridge. To make each thick conductor 1a independent.

In the example of FIG. 4, the thick conductor pattern 1 has one layer, but there are cases where the thick conductor pattern is laminated in two or more layers with a prepreg sheet sandwiched between them (actual flat number 3-9946).
No. 9, JP-A-4-65893, etc.). Alternatively, a multilayer circuit board may be obtained by stacking as shown in FIG. 4 and hot pressing to pattern-etch the copper foil, and then further stacking a prepreg sheet and the copper foil and hot pressing.

[0005]

The thick conductor pattern is
Since there are portions with and without a thick conductor, when a prepreg sheet is laminated on this and heated under pressure, as shown in FIG. 5, the portion with thick conductor 1a becomes thick and the portion without thick conductor has a large thickness. Is thin, and unevenness is likely to occur on the surface.
In FIG. 5, reference numeral 4 is an insulating substrate formed by pressurizing and heating the prepreg sheet.

When the copper foil 3 is pattern-etched to form a circuit pattern, the above-mentioned surface irregularities weaken the tackiness of the dry film or prevent sufficient exposure, resulting in etching defects. Cause Further, the unevenness of the surface causes a portion where the pressure is not sufficiently applied during the subsequent laminating press, which causes a void in the circuit board. Voids significantly degrade the properties of the circuit board and must be eliminated.

In view of the above problems, an object of the present invention is to further reduce the irregularities on the surface of a thick conductor embedded circuit board obtained by laminating a thick conductor pattern and a prepreg sheet and applying pressure and heating. It is to provide a manufacturing method capable of

[0008]

In order to achieve this object, the present invention has a thick conductor pattern having a thick conductor formed in a required circuit pattern, and a thick conductor pattern fitted in a void. A prepreg pattern having a fitting prepreg is combined so that the fitting prepreg is fitted into a space of a thick conductor pattern, and a prepreg sheet is laminated on both sides or one side of the prepreg sheet and heated under pressure to form a thick wall. A conductor-embedded circuit board is manufactured.

[0009] With this structure, the voids of the thick conductor pattern are filled with the fitted prepreg and the prepreg sheet does not fall into the cavities of the thick conductor pattern when heated under pressure. A conductor-embedded circuit board can be manufactured.

It is preferable that the fitting prepregs of the prepreg pattern are positioned by a prepreg bridge connecting adjacent fitting prepregs. By doing so, the relative positions of the plurality of inlaid prepregs are roughly determined, so that the work of combining the thick conductor pattern and the prepreg pattern becomes easy.

At this time, it is preferable that the prepreg bridge of the prepreg pattern is formed so as to intersect the direction of the warp and weft of the cloth in the thermosetting resin so that the warp and the weft are not continuous. If a prepreg bridge is provided, the prepreg bridge overlaps the thick conductor or conductor bridge, and the thickness of that portion may become thick.However, if the prepreg bridge is formed as described above, the prepreg bridge during pressure heating It is possible to prevent the bridge from easily disassembling and flowing, and making the prepreg bridge portion thick.

Further, it is desirable that the prepreg bridge of the prepreg pattern is provided so as to intersect with the conductor bridge of the thick conductor pattern. In this way, when heated under pressure, the prepreg bridge is pressed against the thin conductor bridge and easily flow-deformed, and it is possible to prevent the prepreg bridge from increasing in thickness, and at the same time, the thickness is slightly increased. In that case, since that portion is later removed by a drilling process for cutting the conductor bridge, there is no problem.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below with reference to FIGS. In the manufacturing method of the present invention, first, the thick conductor pattern 1 and the prepreg pattern 5 are prepared.

The thick conductor pattern 1 is the same as the conventional one, and a thick conductor 1a having a required circuit pattern and a peripheral edge frame 1c are formed by punching or cutting a copper plate.
Between adjacent thick conductors 1a and between thick conductors 1a and edge frame 1c
The conductor bridge 1b for connecting the two is integrally formed.

Further, the prepreg pattern 5 is punched or cut out from a prepreg sheet to be fitted into the void of the thick conductor pattern 1 and a prepreg bridge 5b for connecting between the adjacent prepreg 5a. Are formed in an integrated state. The number of prepreg patterns 5 corresponding to the thickness of the thick conductor pattern 1 is prepared.

Next, the thick conductor pattern 1 and the prepreg pattern 5 are assembled so that the fitted prepreg 5a is fitted in the void of the thick conductor pattern 1. Then, the required number of prepreg sheets 2 and copper foils 3 are laminated on both sides. In this state, it is set on a hot press and heated under pressure to integrate the whole.

The circuit board obtained in this manner is one in which a thick conductor is embedded inside an insulating substrate. Since the voids in the thick conductor pattern are filled with a fitting prepreg, the surface is not covered. It will be flat without unevenness. The subsequent steps are the same as in the conventional case, and the pattern etching of the copper foil 3 and the drilling for cutting the conductor bridge 1b are performed.

In this embodiment, the prepreg bridge 5b of the prepreg pattern 5 has the thick conductor pattern 1
Is formed so as to cross the conductor bridge 1b at an angle. An enlarged view of the vicinity of the prepreg bridge 5b is as shown in FIG. That is, by forming the prepreg bridge 5b obliquely, the warp yarns (longitudinal line) and the weft yarns (horizontal line) of the cloth in the thermosetting resin are cut at the portion of the prepreg bridge 5b and are not continuous. When the prepreg bridge 5b is formed in such a shape, the prepreg bridge 5b is heated when pressure is applied.
Is pressed against the thin conductor bridge 1b and is easily disassembled.
As it flows and disappears, the prepreg bridge 5b
It is possible to reliably prevent an increase in thickness due to.

In order to prevent the warp and the weft of the cloth from being continuous at the portion of the prepreg bridge 5b, the prepreg bridge 5b is formed in a substantially "V" shape as shown in Fig. 3B. May be.

The size of the prepreg 5a in which the prepreg pattern 5 is fitted may be such that the prepreg 5a is loosely fitted in the void of the thick conductor pattern 1. When the thick conductor pattern 1 and the prepreg pattern 5 are combined, even if there is a slight gap between the thick conductor 1a and the periphery of the fitted prepreg 5a, the gap is filled with the resin of the prepreg sheet 2, which is not a problem. Absent.

The fitting prepreg 5a does not necessarily have to correspond to the void of the thick conductor pattern 1 in a one-to-one correspondence. For example, when the width of the space of the thick conductor pattern 1 is narrow as shown by the symbol S in FIG. 1, the fitting prepreg corresponding to the portion S may be omitted. This part S
Can be filled with the resin of the prepreg sheet 2 even if there is no fitting prepreg.

When the number of laminated prepreg patterns 5 is large, it is preferable to slightly shift the position of the prepreg bridge for each prepreg pattern in order to stably perform the laminating press. Further, in the case of the prepreg pattern having a small number of fitted prepregs and a large area, the individual fitted prepregs may be formed as independent ones without being connected by the prepreg bridge.

[0023]

As described above, according to the present invention, it is possible to manufacture a flat thick conductor-embedded circuit board having no irregularities on its surface, so that it is possible to prevent etching defects and voids from occurring in the subsequent steps. The yield can be improved.

[Brief description of drawings]

FIG. 1 is a perspective view showing an embodiment of a manufacturing method of the present invention.

FIG. 2 is a sectional view of the same.

3A and 3B are plan views showing preferred examples of a prepreg bridge having a prepreg pattern.

FIG. 4 is a cross-sectional view showing a method for manufacturing a conventional thick conductor embedded circuit board.

FIG. 5 is a cross-sectional view showing a problem of a thick conductor embedded circuit board manufactured by a conventional method.

[Explanation of symbols]

 1: Thick conductor pattern 1a: Thick conductor 1b: Conductor bridge 1c: Edge frame 2: Prepreg sheet 3: Copper foil 4: Insulating substrate 5: Prepreg pattern 5a: Inlaid prepreg 5b: Prepreg bridge

Claims (2)

[Claims] 1. A thick conductor pattern (1) having a thick conductor (1a) formed in a required circuit pattern, and an inlaid prepreg (5a) fitted into a void of the thick conductor pattern (1). And a prepreg pattern (5) having a prepreg pattern (5) such that the fitted prepreg (5a) is fitted into the void of the thick conductor pattern (1), and the prepreg sheet (2) is laminated on both sides or one side thereof,
A method of manufacturing a thick-walled conductor-embedded circuit board, which comprises heating under pressure. 2. A thick conductor (1) of a thick conductor pattern (1).
a) is a conductor bridge (1) that connects adjacent thick conductors.
2. The thick wall according to claim 1, wherein the prepreg pattern (5) is positioned by a prepreg bridge (5b) connecting adjacent prepreg bridges (5b). Method for manufacturing a conductor-embedded circuit board.