JPH05283862A - Manufacture of laminated printed board - Google Patents

Abstract

PURPOSE:To prevent oozing of adhesive from an opening of a blind through hole by pressure and to accurately form wiring circuit on the outermost layer by arranging mold release sheets of a thickness of a special range on and underneath the printed boards disposed through an adhesive layer, pressurizing, heating, and integrally laminating them. CONSTITUTION:Copper foils 3, 3 are laminated on both side surfaces of an insulating base material 1, a hole is made in a part to be connected between wiring circuits of both side surfaces, and plated 4a as a blind through hole 4, thereby electrically connecting the circuits formed on both side surfaces. Then, after laminating, wiring circuits are formed except surfaces to serve as outermost layers. Printed boards 8, 9 are so sequentially laminated through a prepreg 9 to serve as an adhesive layer that an interconnection circuit 6 becomes an inner layer, a mold release sheet 10 is arranged, pressurized, heated through an intermediate plate 11, and integrally laminated. The thickness of the sheet 1 has desirably a range of 0.06-3mm.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a laminated printed circuit board incorporated in various electronic devices.

[0002]

2. Description of the Related Art Conventionally, for example, a television receiver,
In various electronic devices such as radio receivers, a printed circuit board on which a predetermined wiring circuit pattern is formed is often used to mount electronic components and the like.

In recent years, various electronic devices have been improved in performance and miniaturization, and it is necessary to compactly accommodate many wirings inside the electronic devices. In the above-mentioned printed circuit board, wirings are formed on both sides of the base material. This is handled by forming a circuit and increasing the density of the wiring circuit. In addition, a plurality of double-sided printed boards as described above are laminated to form a so-called laminated printed board, and a high-density wiring circuit is formed.

The laminated printed circuit board as described above is manufactured by the following manufacturing method, for example.

First, a copper foil is laminated on both sides of an insulating base material, a hole is formed in a portion where wiring circuits are to be connected on both sides, and plating is applied to this to form a so-called blind through hole. It enables conduction between the formed wiring circuits.

Next, a wiring circuit is formed except for the surface which becomes the outermost layer after lamination. For example, when manufacturing a four-layer laminated printed circuit board, the wiring circuit is formed only on the inner layer surface without forming the wiring circuit on the outermost layer surface. Specifically, an etching resist is formed according to a desired wiring circuit on the surface on which the wiring circuit is formed, and then etching is performed to leave a copper foil corresponding to the wiring circuit, and the etching resist is removed to remove the wiring circuit. To form.

Next, a prepreg serving as an adhesive layer (generally, a reinforcing material such as glass cloth impregnated with a semi-cured material such as epoxy resin) is melted by heating,
It is completely cured by heating again. ) To sequentially laminate each layer in a predetermined order, and to arrange release sheets above and below the laminated printed circuit board, pressurize and heat to melt the prepreg and conform to the unevenness of the circuit. After being melted, it is cured and laminated and integrated.

Then, holes (so-called through-holes) are formed in the portions of the printed circuit boards which are laminated and where conduction is required, and plating is performed so that conduction can be achieved. Next, the outermost wiring circuit is formed. That is, the outermost layer is plated with copper, an etching resist is formed on the outermost layer according to a desired wiring circuit, etching is then performed, copper corresponding to the wiring circuit is left, and the etching resist is removed to form a wiring circuit. Form. The laminated printed circuit board is manufactured by the manufacturing method as described above.

[0009]

However, when a laminated printed circuit board is manufactured by the manufacturing method as described above,
The following inconveniences occur.

That is, printed boards are sequentially laminated in a predetermined order via prepregs, release sheets are arranged on the upper and lower sides of the laminated printed boards, pressure heating is performed, and the prepreg is melted and then cured. Then, in the step of stacking and integrating, the melted prepreg oozes out from the opening of the blind through hole formed in the outermost layer by pressing. The exuded prepreg is hardened in the outermost layer and remains even when copper plating is applied to the outermost layer in a subsequent step. Copper plating is performed on the outermost layer while the prepreg remains as described above, an etching resist is formed according to the desired wiring circuit, and when etching is performed thereafter, the portion where the prepreg remains is in the underlying layer. The plating and etching of the copper foil have not been completed completely, and the circuit cannot be formed accurately.

At this time, a Teflon film or the like having a thickness of about 25 μm is usually used as the release sheet, and since the thickness is thin and the weight is light, sufficient pressure can be applied to the molten prepreg. It seems that it is not possible to prevent the prepreg from being pressurized and flowing out.

Therefore, a method of using a heat-resistant rubber sheet as a release sheet has been proposed. However, although a pressure can be applied to the prepreg, the rubber sheet has a low thickness accuracy at the time of sheet formation, so that it is laminated. It is difficult to apply a uniform pressure when sandwiching the above-mentioned printed circuit board with the rubber sheet and applying pressure, and the flatness of the laminated printed circuit boards is impaired. Further, since the rubber sheet has elasticity, it may expand due to the pressure of the prepreg that flows out, causing the prepreg to flow out. Furthermore, it is difficult to handle, and dust easily adheres when the sheet is formed, and if the release sheet is used with the dust adhering, the dust adheres to the laminated printed circuit board, which deteriorates the quality. In addition, since the heat-resistant rubber sheet is expensive, its production cost is high and its practicality is low.

It has also been proposed to manufacture a laminated printed circuit board by using a release sheet in which a polyethylene film having a low softening point is sandwiched by heat-resistant release sheets.
Similar results, high production cost and low practicability.

Therefore, the present invention has been proposed in view of the above circumstances, in which printed boards are sequentially laminated in a predetermined order via prepregs, and release sheets are arranged above and below the laminated printed boards. In the process of melting and then curing the prepreg by applying pressure and heating, and then laminating and integrating, the prepreg does not exude from the upper and lower openings of the blind through holes formed in the outermost layer by pressure. An object of the present invention is to provide a method for manufacturing a laminated printed circuit board, in which a wiring circuit can be accurately formed in the outermost layer in the subsequent steps and the production cost can be reduced.

[0015]

In order to achieve the above-mentioned object, the present invention provides a method for manufacturing a laminated printed circuit board in which printed circuit boards having blind through holes are laminated with an adhesive layer interposed therebetween. It is characterized in that a release sheet having a thickness of 0.06 to 0.3 mm is arranged on the upper and lower sides of the arranged printed circuit boards, pressure heating is performed, and lamination and integration are performed.

First, as shown in FIG. 1, copper foils 2 and 3 are laminated on both sides of an insulating base material 1, and holes are formed at the portions on both sides where wiring circuits are to be connected, as shown in FIG. Plating 4a is applied to this to form blind through-holes 4 to enable conduction between wiring circuits formed on both surfaces.

Next, a wiring circuit is formed except for the surface which becomes the outermost layer after lamination. For example, when manufacturing a four-layer laminated printed circuit board, the wiring circuit is formed only on the inner layer surface without forming the wiring circuit on the outermost layer surface. That is,
An etching resist is formed on the copper foil on the surface on which the wiring circuit is to be formed according to the desired wiring circuit, and then etching is performed to remove the etching resist, and as shown in FIG. 3, the copper foil corresponding to the wiring circuit is formed. 3, the wiring circuit 6 is formed while leaving the plating 4a.

Then, as shown in FIG. 4, the printed circuit boards 8 and 9 are connected to the wiring circuit 6 via the prepreg 7 serving as an adhesive layer.
Are sequentially laminated so as to be an inner layer, and release sheets 10 are arranged above and below the laminated printed circuit boards 8 and 9. Pressurization and heating are performed through an intermediate plate 11, and the prepreg 7 is formed.
After being melted, it is cured and laminated and integrated.

Then, a through hole is formed in a portion where the wiring circuit between the laminated printed circuit boards 8 and 9 needs to be electrically conductive.
It is plated to make it conductive. Then
The outermost wiring circuit is formed. That is, as shown in FIG. 6, copper plating 12 is applied to the outer layers of the printed circuit boards 8 and 9, etching resist 13 is formed according to a desired wiring circuit as shown in FIG.
The etching resist 13 is removed, and the wiring circuit 14 is formed while leaving the copper plating 12, the plating 4a, and the copper foil 2 corresponding to the wiring circuit as shown in FIG.

The material of the base material 1 is not particularly limited as long as it can be used for a usual printed circuit board, and it is prepared, for example, by impregnating or coating a paper with a phenol resin or the like. The blind through hole 4 may be formed by a drill or the like. After removing the burrs, plating 4a is applied by a method usually used for manufacturing a printed circuit board to form a space between wiring circuits formed on both surfaces of the base material 1. It enables the electric conduction of.

Further, the etching resist 5 for forming the wiring circuit 6 may be patterned by a normal photolithography technique, and the copper foil 3 may be etched by a usual method such as wet etching or dry etching. ..

Next, as the prepreg 7 serving as an adhesive layer, there may be mentioned a prepreg 7 in which a reinforcing material such as glass cloth is impregnated with a semi-cured material such as an epoxy resin, which is melted by heating and reheated. Any material that can be completely cured by

Further, the release sheet 10 is preferably made of a material having relatively low elasticity so that the molten prepreg 7 does not expand when it flows out under pressure. Examples thereof include a Teflon film, a cellulose-based cellulose triacetate film, and a methylpentene copolymer. The thickness of the release sheet 10 is preferably 0.06 to 0.3 mm. When the thickness of the release sheet 10 is less than 0.06 mm, the weight of the release sheet 10 is light and the prepreg 7
Cannot be prevented from flowing out from the opening of the blind through hole 4, and if it is larger than 0.3 mm, a film having a good thickness accuracy cannot be obtained at the time of molding the release sheet 10, and the film is laminated. It is impossible to apply uniform pressure to the printed boards 8 and 9. The release sheet 10 may be formed by stacking thin films with the thickness within the above range, but in this case, it is desirable that the release sheet be formed of one kind of material.

The formation and plating of the through holes may be carried out in the same manner as the above-mentioned formation of the blind through holes 4.
Further, the wiring circuit 6 in the outermost layer is also formed.
It may be performed in the same manner as the formation of.

[0025]

According to the present invention, in a method for manufacturing a laminated printed circuit board in which printed circuit boards having blind through holes are laminated with an adhesive layer in between, a thickness of 0.06 is provided above and below the printed circuit board arranged with the adhesive layer in between. Since a 0.3 mm release sheet is arranged and pressure-heated to perform lamination and integration, pressure-heating is applied to the prepreg to melt the adhesive layer and then to cure, so that the lamination is integrated. The adhesive layer does not ooze out from the opening of the blind through hole formed in the outermost layer due to the pressure in the step of forming the wiring, and the wiring circuit can be accurately formed in the outermost layer in the subsequent step.

[0026]

EXAMPLES Specific examples to which the present invention is applied will be described below based on experimental results.

In this example, a four-layer laminated printed circuit board was formed. First, as shown in FIG. 1, copper foils 2 and 3 are laminated on both sides of an insulating base material 1, and holes are formed in portions where wiring circuits are to be connected on both sides as shown in FIG. 4a is applied to form a blind through hole 4 to enable conduction between wiring circuits formed on both sides 2
Five sets of printed circuit boards were prepared.

Next, a wiring circuit was formed except for the surface to be the outermost layer after lamination. That is, in the above-mentioned two sets of printed circuit boards, an etching resist is formed on a copper foil on a surface on which a wiring circuit to be an inner layer is formed according to a desired wiring circuit,
After that, etching was performed to remove the etching resist, and as shown in FIG. 3, the wiring 4 was formed by leaving the plating 4a and the copper foil 3 corresponding to the wiring circuit.

Next, as shown in FIG. 4, the printed boards 8 and 9 are sequentially laminated in a predetermined order with the prepreg 7 serving as an adhesive layer so that the wiring circuit 6 is an inner layer, and the laminated prints are formed. The release sheets 10 are arranged on the upper and lower sides of the substrates 8 and 9, and pressure heating is performed through the intermediate plate 11, and the prepreg 7
After being melted, it was cured and laminated to be integrated.

At this time, of the five sets of laminated printed circuit boards 8 and 9, the first set was manufactured by using a Teflon film (film thickness 25 μm) as the release sheet 10 to obtain Comparative Example 1.
Comparative Example 2 was manufactured by using a cellulose triacetate film having a film thickness of 50 μm as the release sheet 10 for the second set. Further, the third set is manufactured by using three sheets of Tedlar films having a thickness of 25 μm as a release sheet, and is manufactured as Example 1, and the fourth set is a methylpentene copolymer film having a thickness of 60 μm. Example 2 was manufactured using the same.

In Comparative Example 1 and Comparative Example 2, FIG.
As shown in FIG. 3, the printed board 8 and 9 on which the prepreg 7 is laminated seeped out from the opening of the blind through hole 4. In addition, in Examples 1 and 2, bleeding did not exude from the openings of the blind through holes 4 of the printed circuit boards 8 and 9 on which the prepreg gub 7 was laminated as shown in FIG.

Then, through holes are formed in portions where wiring circuits between the printed circuit boards 8 and 9 laminated in Comparative Examples 1 and 2 and Examples 1 and 2 are required to be electrically conductive by plating. Made possible. Next, the wiring circuit of the outermost layer was formed. That is, as shown in FIG. 6, copper plating 12 is applied to the outer layers of the printed circuit boards 8 and 9, and an etching resist 13 is formed according to a desired wiring circuit as shown in FIG.
Then, etching was performed to remove the etching resist 13, and copper wiring, plating, and copper foil according to the wiring circuit were left, and the wiring circuit was formed.

At this time, in Examples 1 and 2, since the bleeding did not exude from the openings of the blind through holes 4 of the printed boards 8 and 9 on which the prepreg 7 was laminated as described above, as shown in FIG. In addition, the prepreg 7 does not remain under the copper plating 12, and the wiring circuit formed by the etching resist 13 is accurately formed by the copper plating 12, the plating 4a, and the copper foil 2 as shown in FIG. I was able to.

However, in Comparative Examples 1 and 2, the printed boards 8 and 9 on which the prepreg 7 is laminated as described above.
Since it oozes out from the upper and lower openings of the blind through-hole 4, the etching resist 13 is formed with the prepreg 7 left under the copper plating 12, as shown in FIG. When etching is performed as it is, the plating 4a and the copper foil 2 existing under the prepreg 7
Remained without being removed by etching, and the wiring circuit formed by the etching resist 13 could not be accurately formed.

From these results, in the method for manufacturing a laminated printed circuit board in which the printed circuit boards having blind through holes are laminated via the adhesive layer, after the printed circuit boards are laminated via the adhesive layer, the laminated printed circuit boards are arranged above and below the laminated printed circuit board. When a release sheet is placed and heated under pressure, its thickness is set to 0.
By setting the thickness to 06 to 0.3 mm, the prepreg is heated under pressure to melt the prepreg and then cured.
In the step of stacking and integrating, the molten prepreg does not seep out from the opening of the blind through hole formed in the outermost layer due to pressure, and the wiring circuit can be accurately formed in the outermost layer in the subsequent steps. Was confirmed.

[0036]

As is apparent from the above description, in the present invention, in a method for manufacturing a laminated printed circuit board in which printed circuit boards having blind through holes are laminated via an adhesive layer, the printed circuit boards are arranged via an adhesive layer. A release sheet having a thickness of 0.06 to 0.3 mm is placed on the upper and lower sides of the printed circuit board and pressure-heated to perform lamination and integration. Therefore, pressure-heat is applied to the adhesive layer to melt the adhesive layer. After that, in the step of curing and laminating and integrating, the adhesive layer does not exude from the opening of the blind through hole due to pressure, and the wiring circuit can be accurately formed in the outermost layer in the subsequent step, It is possible to obtain a laminated printed circuit board with improved quality.

When selecting a release sheet, heat resistance,
Since a wide range of materials having releasability can be selected, the production cost can be reduced, the productivity is very high, and the industrial value is high.

[Brief description of drawings]

FIG. 1 shows an example of a method for manufacturing a laminated printed circuit board of the present invention in the order of steps, and is a schematic cross-sectional view of a main part showing a step of laminating a copper foil on a base material.

FIG. 2 is a cross-sectional view showing a process of forming a blind through hole.

FIG. 3 is a cross-sectional view showing a state in which a wiring circuit is formed on a surface corresponding to an inner layer.

FIG. 4 is a cross-sectional view showing a step of stacking printed circuit boards via prepregs.

FIG. 5 is a cross-sectional view showing a state in which printed circuit boards are laminated via prepregs.

FIG. 6 is a cross-sectional view showing a step of applying copper plating to the outermost layer of laminated printed circuit boards.

FIG. 7 is a cross-sectional view showing a step of forming a wiring circuit on the outermost layer.

FIG. 8 is a cross-sectional view showing a state in which a wiring circuit is formed in the outermost layer.

FIG. 9 is a cross-sectional view showing a laminated printed circuit board manufactured by the method for manufacturing a laminated printed circuit board according to the present invention.

FIG. 10 is a cross-sectional view showing a state in which printed circuit boards are laminated via a prepreg in the steps of the conventional method for manufacturing a laminated printed circuit board.

FIG. 11 is a cross-sectional view showing a step of forming a wiring circuit in the outermost layer in the steps of the conventional method for manufacturing a laminated printed circuit board.

[Explanation of symbols]

 1 ... Base material 2 ... Copper foil 3 ... Copper foil 4 ... Blind through hole 4a ... Plating 7 ... Prepreg 8 ... Printed circuit board 9 ... ..Printed circuit board 10 ... Release sheet 12 ... Copper plating

Claims (1)

[Claims] 1. A method for manufacturing a laminated printed circuit board in which printed circuit boards having blind through holes are laminated with an adhesive layer in between, and a thickness of 0.06 to 0.3 mm is provided above and below the printed circuit board arranged with the adhesive layer. 2. A method for manufacturing a laminated printed circuit board, comprising: arranging the release sheet as described in 1 above, applying pressure and heating to perform lamination integration.