JP3398409B2 - Manufacturing method of multilayer printed wiring board - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a manufacturing method for obtaining a multilayer printed wiring board having an excellent outer copper foil surface property with high precision, workability and low cost.

[0002]

2. Description of the Related Art With the progress of higher density and higher speed of electronic equipment, wiring boards for mounting electronic parts are becoming more and more multi-layered, and the demand for 6-layer boards or more is particularly remarkable. Conventionally, such a multilayer wiring board (six-layer board as an example) has two inner layer core materials 1, 2 with circuits formed on both front and back surfaces as shown in FIG.
Are laminated with an appropriate number of prepregs 3 interposed therebetween, and the prepreg 3 and the copper foil 4 are superposed on both surfaces thereof,
It is molded by heating and pressurizing the whole body by hot pressing or the like and integrally molding. In the multilayer wiring board obtained in this manner, the inner layer core material 1 and the inner layer core material 2 must be aligned with each other in the circuit patterns formed on the front and back surfaces of the circuit, and the inner layer core material 1, Two alignments are being performed.

A conventional alignment method is as follows. (A) Pin Lamination Method As shown in FIG. 2, two copper foils 4, two inner layer plates 1,
2, reference holes 5 for alignment are made at the same pitches at predetermined positions of all the laminated materials such as the prepreg 3, and the mirror plate 6 is also made at the same pitch. Then, in these holes 5, pins 8 that are erected at a predetermined pitch in a dedicated mold 7 are provided.
Are sequentially inserted to perform alignment. Then, all of them are set in a hot press and thermocompression molding is performed. (B) Pinless method As shown in FIG. 3, two inner core materials 1 and 2 and a prepreg 3 are preliminarily provided with positioning holes 5 at predetermined positions, and these holes are stacked in order, A stopper 11 is driven into the alignment hole 5 from one side to crimp the leading end to mechanically fasten the layers. Here, a rivet 12 or the like is also used instead of the staple.

The inner layer core material and the prepreg (hereinafter referred to as inner layer unit) 13 which are aligned and fastened in this manner are shown in FIG.
As shown in, the copper foil 4 and the prepreg 3 are placed on the mirror surface plate 6, the inner layer unit 13 is placed, and the prepreg 3, the copper foil 4 and the mirror surface plate 6 are sequentially placed to form a set for one step, and hot pressing is performed. And set in a hot press machine to perform thermocompression molding.

[0005]

However, these alignment methods have the following problems. (A) Pin-lamination method High-precision alignment is possible, but if pin holes remain in the formed laminated board, it will have a serious effect on the processing of the printed circuit board in the subsequent process and it will be necessary to cut and remove it in advance. In addition, there is a problem in appearance and circuit formation due to the exudation of the prepreg resin around the pin hole. In addition, a large number of man-hours are required for pin removal work after molding and resin removal work around the pins. (B) Pinless method Since there is no pin hole, there is no need to remove the pin after molding or to remove the resin adhering to the periphery of the pin. This method is disclosed in, for example, JP-A-3-53593. In such a method, excessive pressure is applied to the portion fastened with a rim, etc., and wrinkles occur in the outer layer copper foil of this portion and the peripheral portion,
The actual situation is that a practical method cannot be called because it has a serious influence on the processing of the printed circuit board in the subsequent process.

The present invention has been made in order to solve these problems, and in a method for producing a multilayer wiring board having 6 or more layers, the workability is excellent and there is no problem in appearance of the outer layer copper foil. As a result, it is an object of the present invention to provide a method for manufacturing a multilayer wiring board having a good product yield.

[0007]

That is, according to the present invention, a prepreg is provided between a plurality of inner layer core materials formed with wiring patterns, and a prepreg and a copper foil or prepreg are provided outside the inner layer core material. In a method for manufacturing a multilayer printed wiring board in which single-sided copper-clad laminates are respectively laminated and then heated and pressed to be integrally molded, a reference hole provided in advance in the inner core material and the prepreg between the inner core materials is fitted with a reference hole. A method for manufacturing a multilayer printed wiring board, characterized in that the tip is divided into 11 to 20 when inserting and caulking and fixing.
More preferred is a method of performing press molding at a molding pressure of 15 kg / cm ² or less, and a method of molding using an autoclave type vacuum press. Hereinafter, each constituent element of the present invention will be described in detail.

The inner layer core material used in the present invention is not particularly limited, but examples of the insulating material include a glass epoxy material and a glass polyimide material, and the thickness of the insulating material is generally 0.1 mm to 0.5 mm. And the copper foil thickness is 1
8μ to 105μ is general. The prepreg used in the present invention is not particularly limited, but as the resin composition, there are epoxy, polyimide, etc., the thickness of the glass cloth used is generally 0.05 to 0.2 mm, and as a resin component. Is generally 40 to 75% by weight. The copper foil used in the present invention is not particularly limited, but it is an electrolytic copper foil and generally has a thickness of 12 to 70 μm.

The single-sided copper-clad laminate used in the present invention is one having a copper foil only on one side of an insulating layer formed by laminating a copper foil and a prepreg and curing the prepreg. The copper foil is not particularly limited. Although it is not a thing, it is an electrolytic copper foil and its thickness is 12μ-3
5μ is common. In addition, the prepreg is composed of one or a plurality of sheets, and the insulating layer thickness is generally 0.05 mm to 0.5 mm.

In the present invention, the fitting end portions 11 to 11 are
It is characterized by being divided into 20 and caulking. By this method, the shape after crimping which is good in terms of accuracy and appearance as shown in FIG. 5 can be obtained. If the tip is not divided, as shown in FIG. 6, there is a problem in accuracy due to buckling at the stage of crimping the fit, and the flange portion formed by crimping has a thickness of the plate. It swells greatly in the direction,
It is also a problem that the outer layer copper foil is wrinkled during pressing.
Or, even when the crimping tip is divided and crimped, if the number of splits is 10 or less, buckling at the crimping step can be avoided as shown in FIG. 7, but the flange portion formed by crimping work The plate has a large bulge in the thickness direction, which causes a problem such as a reduction in accuracy due to buckling during pressing and a wrinkle due to pressure concentration on the outer copper foil portion. On the other hand, if the tip of the caulking is divided into more than 20, the life of the caulking jig will be shortened, and the caulking jig will be more difficult to machine, making it impractical. In the present invention, it is desirable that the tip of the eyelet is divided at the same time as the caulking. The method of dividing the tip in advance is not practical, because the dividing work is troublesome and the smooth work is impaired when the divided eyelets are inserted into the reference holes.

The eyelets used in the present invention include copper, brass, brass and the like, and in some cases, the surface thereof is thinly plated with tin or the like. Although the shaft diameter of the eyelet used in the present invention is not particularly limited, it is usually 1
The one having a diameter of -6 mm is used, and the one having a diameter of 2-5 mm is preferable. In the present invention, the molding pressure during hot pressing is 15 kg
By setting it to be / cm ² or less, it is possible to further improve the surface properties such as wrinkles and the appearance quality. Pressure is 15Kg / cm
If the number exceeds ² , it is feared that the quality of the surface appearance such as wrinkles may be affected depending on the amount of prepreg resin and the number of prepreg resins on the outside of the fitting portion, and the number of laminated plates during hot pressing.

In the present invention, by using an autoclave type vacuum press as the hot press, it is possible to further improve the surface property such as wrinkles and the appearance quality. Molding pressure when using hydropress is usually 40
It is Kg / cm ^2, which is not practical because the formation of molding voids occurs when the pressure is lowered. The method of vacuum pressing in hydropressing is performed and the molding pressure tends to be lowered, but the present condition is about ²⁰ to 30 kg / cm ² , and by further lowering the pressure, the laminated plate to be molded is formed. Depending on the copper foil thickness of the inner layer core material and the content of the pattern, formation of molding voids may be observed. On the other hand, in an autoclave type vacuum press, molding at 15 kg / cm ² or less is common, and molding at 10 kg / cm ² or less is sufficiently possible. Thus, by using the autoclave type vacuum press, molding at 15 kg / cm ² can be realized without problems such as molding voids. The lower limit of the molding pressure is not particularly specified and can be appropriately determined experimentally, but is usually about 5 kg / cm ² .

In the present invention, the molding temperature and time at the time of hot pressing are not specified because the optimum values differ depending on the molding material, and the temperature conditions necessary for ensuring the performance of the material used (usually the material supply It is necessary to comply with the above instruction), and there is no limiting condition for carrying out the method of the present invention under temperature conditions.

As described above, the method for manufacturing a multilayer printed wiring board according to the present invention is intended to solve the problems of surface property and appearance after lamination of multilayer boards of 6 layers or more and to maintain the interlayer consistency, so that the inner core material is When inserting the eyelets into the reference holes provided in the prepreg between the inner core material and the prepreg, and fixing the eyelets,
It is divided into 20 and performed. Further, the method of the present invention comprises
In order to solve the above-mentioned problems, it is a method in which the molding pressure is 15 kg / cm ² or less in the above method.
Further, the method of the present invention is a method of performing molding using an autoclave type vacuum press in the above method in order to solve the above problems. It is preferable to use a fitter having a wall thickness of 0.2 mm or less. Further, in the peripheral portion of the hole for inserting the fitter of the inner layer core material, the copper foil at the portion where the fitter flange portion contacts is removed beforehand. It is something to put. Hereinafter, an example of an embodiment of the present invention will be described with reference to examples.

[0015]

Example 1 Two glass epoxy inner layer core materials having an insulating layer thickness of 0.3 mm and a copper foil thickness of 70 μ having wiring patterns formed on both sides, and two glass epoxy prepregs having a thickness of 0.1 mm between them. Was inserted, and a brass eyelet having a shaft outer diameter of 3 mm and a wall thickness of 0.3 mm was driven into a preinstalled eyelet reference hole, and the tip of the eyelet was divided into 12 and simultaneously caulked to form an inner layer unit. Then 0.1 mm on both sides of the inner layer unit
Two thick glass epoxy prepregs, one on the outside
Layered 8μ thick electrolytic copper foil on the whole, temperature 170 ℃, pressure 12
A 6-layer printed wiring board was manufactured by heat-press molding with an autoclave type vacuum press for 120 minutes under the condition of Kg / cm ² . Example 2 A 6-layer printed wiring board was produced in the same manner as in Example 1 except that the tip of the eyelet in Example 1 was divided into 18.

Examples 3 to 4 The press molding in Examples 1 and 2 was carried out using a vacuum hydropress under the conditions of a temperature of 170 ° C. and a pressure of 25 kg / cm ^2.
A 6-layer printed wiring board was manufactured under the same conditions as in Examples 1 and 2 except that the process was performed for 0 minutes. Examples 5 to 6 Six-layer printed wiring boards were manufactured under the same conditions as in Examples 3 and 4 except that the press molding pressure in Examples 3 and 4 was 12 kg / cm ² .

COMPARATIVE EXAMPLE 1 Except that the same inner layer core material, prepreg, and copper foil as in Example 1 were preliminarily provided with holes having a diameter of 5 mm as reference holes for pin laminating, and were aligned by a normal pin lamination method using metal pins. A 6-layer printed wiring board was manufactured under the same conditions as in Example 1. Comparative Example 2 A 6-layer printed wiring board was manufactured under the same conditions as in Example 1 except that caulking without splitting the end of the eyelet in Example 1 was performed.

COMPARATIVE EXAMPLE 3 A 6-layer printed wiring board was manufactured under the same conditions as in Example 1 except that the split end of the eyelet in Example 1 was 8.

Comparative Example 4 A 6-layer printed wiring board was prepared under the same conditions as in Comparative Example 3 except that the press forming in Comparative Example 3 was carried out for 90 minutes at a temperature of 170 ° C. and a pressure of 25 kg / cm ² using a vacuum hydropress. Was manufactured. With respect to the multilayer printed wiring boards obtained in the above Examples and Comparative Examples, evaluation tests were conducted on the appearance of copper foil surface, workability, and positional deviation, and the results are summarized in Table 1. The multilayer printed wiring board of the present invention has excellent copper foil surface appearance quality, good workability, and little positional displacement, and the effect of the present invention can be confirmed.

[0020]

As described above, according to the present invention, the stopper tip portion is 11
Since it is a method of dividing into 20 and caulking, it is possible to provide a method of obtaining a multilayer printed wiring board having excellent outer copper foil surface properties with high accuracy and workability at low cost.

[0021]

[Table 1]

[Brief description of drawings]

FIG. 1 is a sectional view showing a general method for manufacturing a multilayer wiring board.

FIG. 2 is a cross-sectional view showing a conventional alignment method by a pin-lamination method.

FIG. 3 is a cross-sectional view showing a positioning method by a pinless method.

FIG. 4 is a cross-sectional view showing a method of stacking inner layer units that are aligned and fastened by a pinless method.

FIG. 5 is a cross-sectional view of a fit portion after press-fitting after positioning and fastening by the pinless method of the present invention.

FIG. 6 is a cross-sectional view of a fitting portion after press-fitting after positioning and fastening by a conventional pinless method.

FIG. 7 is a cross-sectional view of a fitting portion after press-fitting after alignment and fastening by a conventional pinless method.

[Explanation of symbols]

1 Inner layer core material 2 Inner layer core material 3 prepreg 4 copper foil 5 Positioning reference hole 6 Mirror plate 7 Dedicated mold 8 pin laminating pin 11 maiden 12 rivets 13 Inner layer unit

─────────────────────────────────────────────────── --- Continued from the front page (56) References JP-A-3-53593 (JP, A) JP-A 63-19897 (JP, A) JP-A 64-55215 (JP, A) JP-B 58- 38259 (JP, B1) (58) Fields investigated (Int.Cl. ⁷ , DB name) H05K 3/46 B21D 39/00

Claims (3)

(57) [Claims] 1. A prepreg is laminated between a plurality of inner layer core materials formed with a wiring pattern, and a prepreg and a copper foil or a prepreg and a single-sided copper clad laminate are laminated outside the inner layer core material. In the method for manufacturing a multilayer printed wiring board that is integrally molded by post-heating and pressurization, when inserting the eyelet into the reference hole previously provided in the prepreg between the inner layer core material and the inner layer core material, when caulking and fixing, 11 to the tip
A method for manufacturing a multilayer printed wiring board, characterized in that the method is divided into 20 steps. 2. The method according to claim 1, wherein press molding is carried out at a molding pressure of 15 kg / cm ² or less. 3. The method according to claim 1, wherein the molding is performed using an autoclave type vacuum press.