JPH06314886A - Multilayer board and manufacture thereof - Google Patents

Abstract

PURPOSE:To obtain a low-cost multilayer board which provides an insulation layer with high permittivity, and what is more, excels in heat resistance and reliability by injecting and curing epoxy resin to which an inorganic filler of high permittivity and a curing agent are combined into a cavity formed between printed wiring boards laid out as opposed so that they may not come into contact with each other. CONSTITUTION:A forming die comprises a top force 1 and a bottom tool 2 and forms a cavity 3. A printed wiring board 4 is laid out in this cavity in such a fashion that its single side may come into contact with the inner surface of the cavity while the other side may not come into contact with each other, forming a cavity 5. A chemical compound, such as titanium dioxide and barium titanate as high permittivity of inorganic filler and epoxy resin to which phenol compound or the like is combined as a curing agent are heated and pressed so that they may fill up the cavity 5 from a spool 6 and cured. After cured, the forming die is opened so that it may be possible to obtain a multilayer foundation 8 having a high permittivity insulation layer 7. Then, they are drilled and a through hole 9 is made where through hole plating is performed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multilayer substrate used in electronic equipment and a method for manufacturing the same.

[0002]

2. Description of the Related Art With the increase in speed and density of electronic equipment, external noise that causes malfunctions and noise generated by electronic components themselves have become a problem. There is a substrate having a structure in which a bypass capacitor for absorbing and removing these noises is formed inside the substrate (JP-A-53-68870, JP-A-58-158996, JP-A-3-20).
1593 gazette). In the substrate having such a structure, an insulator having a high dielectric constant is used between the electrodes of the capacitor.

As described above, the following two methods are known as methods for manufacturing a multilayer substrate having a high dielectric constant of the insulating layer.

First, a resin varnish containing high-dielectric particles is impregnated into a fiber base material and dried to obtain a high dielectric constant prepreg 10 and a copper foil 11 which are laminated and press-molded to obtain a high dielectric constant. 2A is obtained (FIG. 2A), and the copper foil of this substrate is processed to form the inner layer circuit 12 to form the inner layer plate 13 (FIG. 2).
(B)), the inner layer plate 13 and the copper foil 11 thus obtained are stacked via a normal prepreg 14 and press-molded to form a multilayer (Fig. 2 (c)), and finally drilling and surface circuit This is a method in which a multilayer substrate 16 (FIG. 2 (d)) having a high dielectric constant insulating layer 15 is obtained by processing and outer shape processing (JP-A-61).
-136281).

A second method for producing a multi-layer substrate having a high dielectric constant of an insulating layer is a method of forming a thermoplastic resin containing a filler having a high dielectric constant into a sheet, laminating and molding the same (JP-A-3- See Japanese Patent Publication No. 201593).

[0006]

In the first manufacturing method,
The ratio of the fiber base material such as glass cloth in the substrate is 20 to
It is as large as 50% by volume, and the influence of the fiber base material on the dielectric properties of the substrate is large. That is, since the dielectric constant of the base material cannot be increased, the dielectric constant of the insulating layer becomes low, and even if high dielectric particles are mixed in the remaining resin, the effect of increasing the dielectric constant of the entire insulating layer is small. Further, when a large amount of high-dielectric particles are blended, the fluidity of the varnish is lowered and a prepreg cannot be produced, or the adhesiveness to metal foil is poor.

In the second manufacturing method, since the viscosity of the molten resin at the molding temperature becomes high, a large amount of filler having a high dielectric constant cannot be blended, and the dielectric constant of the insulating layer cannot be increased. In addition, many thermoplastic resins have insufficient heat resistance, and resins having good heat resistance are disadvantageous in terms of cost such as high price and high molding temperature.

The present invention has been made in view of the above circumstances, and an object thereof is to provide at low cost a multilayer substrate having an insulating layer having a high dielectric constant and excellent in heat resistance and reliability.

[0009]

According to the present invention, an epoxy resin containing a high dielectric constant inorganic filler and a curing agent is injected and cured into a void formed between printed wiring boards which are arranged so as not to contact each other. This is a multi-layer substrate.

In the multi-layer substrate of the present invention, printed wiring boards are arranged facing each other in a cavity formed by a molding die so that one surface is in contact with the inner surface of the cavity and the other surfaces are not in contact with each other, and the printed wiring boards are formed between the printed wiring boards. It is manufactured by injecting and curing an epoxy resin in which a high-dielectric-constant inorganic filler and a curing agent are mixed into the formed voids. Hereinafter, the present invention will be described in detail.

As the epoxy resin used in the present invention, those generally used as electrical and electronic insulating resins can be used. In particular, orthocresol novolak type epoxy resin and alkyl-substituted biphenol diglycidyl ether are preferable in terms of moisture resistance, heat resistance, moldability, adhesiveness, and the like.

The epoxy resin has a melt viscosity of 1 Pa at 150 ° C. using an ICI cone plate type viscometer.
It is preferably s or less, and more preferably 0.3 Pa · s or less. If the melt viscosity of the epoxy resin is high, the compounding amount of the high dielectric constant inorganic filler will be limited, and if a large amount of the inorganic filler is compounded, the fluidity at the time of molding will decrease, molding will not be possible, or the step of the circuit pattern This is because a void is generated in the part. If an epoxy resin having a low melt viscosity is used, a large amount of inorganic filler can be blended while ensuring fluidity during molding, and the dielectric constant of the insulating layer can be increased. If the viscosity under the above conditions exceeds 1 Pa · s, a sufficient amount of the inorganic filler cannot be blended, and the dielectric constant of the insulating layer cannot be increased. By using a resin having a low melt viscosity, additives such as an organic solvent, a plasticizer, and a diluent for reducing the viscosity of the resin are unnecessary. In particular, when an organic solvent is used, costs for equipment such as explosion-proof measures, recovery equipment, and exhaust treatment equipment in the drying process become unnecessary.

As the curing agent for the epoxy resin, those generally used as the curing agent for the epoxy resin for electric and electronic purposes can be used. Examples thereof include phenol compounds, acid anhydrides, guanidine derivatives, imidazoles, and polyamines. Particularly, novolac type phenol resin or phenol aralkyl resin is preferable from the viewpoint of good moisture resistance and electric characteristics.

As the high dielectric constant inorganic filler, compounds such as titanium dioxide, barium titanate, and strontium titanate can be used, and high dielectric ceramics used in general ceramic capacitors can be used. The higher the dielectric constant of the inorganic filler, the higher the dielectric constant of the insulating layer. However, an inorganic compound having a high dielectric constant is generally selected according to need because it has a large temperature characteristic, that is, a large temperature coefficient of the dielectric constant. Among these inorganic fillers, in particular, the one obtained by firing and crushing a compounded powder which is commercially available as a raw material of a ceramic capacitor is preferable because an additive or the like for controlling the temperature characteristic is previously compounded. The content of the inorganic filler in the molding material is preferably 50 to 90% by volume, more preferably 60 to 80% by volume. When the content of the inorganic filler is less than 50% by volume, the effect of increasing the dielectric constant of the insulating layer is low, and the thermal expansion coefficient of the insulating layer is large, so that the adhesiveness to the printed wiring board is reduced and the dimensional stability is improved. Becomes worse. On the other hand, when the content of the inorganic filler exceeds 90% by volume, the flowability of the molding material during molding is low and the moldability is deteriorated.

The inorganic filler is mixed in the molding material in powder form, and the particle size thereof is appropriately selected in consideration of the thickness of the insulating layer and the fluidity of the molding material in the molding die. For example, the same average particle size as the filler used in general molding materials is 5
Those having a range of up to 50 μm are preferable because they are easy to mold. Further, the shape thereof may be any shape such as a crushed shape, a spherical shape, or a fibrous shape. However, when a spherical filler is used, the flowability of the molding material at the time of molding is good, and when a crushed or fibrous filler is used, the mechanical strength of the insulating layer is increased.

If necessary, an amine-based or phosphorus-based curing accelerator that accelerates the curing reaction may be used. In addition, release agents such as higher fatty acids, higher fatty acid metal salts, ester waxes, polyethylene waxes, colorants such as carbon black and organic dyes, coupling agents such as epoxysilane, aminosilane, organic titanates, and aluminum alcoholates. May be used.

As a method for producing a molding material using the above raw materials, a generally used method can be used as it is. For example, a method may be mentioned in which a predetermined amount of raw materials are sufficiently mixed with a mixer or the like, and then kneaded with a hot roll, an extruder, or the like, cooled, and pulverized. When a resin that is liquid at room temperature is used, it may be kneaded with a kneader, a kneader, a roll or the like.

The printed wiring board is not particularly limited, and a phenol resin, an epoxy resin, a bismaleimide triazine resin, a polyimide resin-based double-sided or multi-layered substrate which is commonly used in electronic equipment can be used. In particular,
A glass epoxy printed wiring board is preferable in terms of price and reliability. Of course, it may be a multilayer substrate obtained by the method of the present invention. The thickness and outer shape of the printed wiring board can be appropriately selected and set according to the application, and holes such as through holes and counterbore may be formed. Also, one surface may be formed by combining a plurality of printed wiring boards.

As a method for producing the multilayer substrate of the present invention, a general method such as a transfer molding method, a compression molding method, an injection molding method or a casting method can be used. In particular, the transfer molding method is preferable because the molding apparatus is small, the generation of voids during molding can be suppressed to a low level, and the filling property is good. The molding die may be one generally used in the above-mentioned molding method, and the shape of the cavity serving as the outer shape of the substrate may be any shape as long as it can be molded. Examples thereof include a flat plate shape, a shape having irregularities, and a curved surface shape.

The procedure for manufacturing a multilayer substrate using the above members and the transfer molding method will be described with reference to FIG. 1, but the method of the present invention is not limited to this.

As shown in the sectional view of (a), the mold comprises an upper mold 1 and a lower mold 2 to form a cavity 3. The printed wiring board 4 is arranged in this cavity so that one surface of the printed wiring board 4 is in contact with the inner surface of the cavity and the other surface is not in contact with each other to form the void 5. As a method for fixing the printed wiring board at this time, a known method such as vacuum suction, electrostatic suction, or a method using a fixing pin or a spacer can be used. next,
A powdery, flake-shaped, sheet-shaped or tablet-shaped molding material is heated and pressed as needed to fill the voids 5 from the sprue 6 and cure. After curing, the mold is opened to obtain the multilayer substrate 8 having the high dielectric constant insulating layer 7 as shown in (b). Further, if necessary, as shown in (c), drilling is performed to provide through holes 9, and through hole plating is performed.

[0022]

By using a molding die to integrally mold two or more printed wiring boards with an epoxy resin molding material containing a high dielectric constant inorganic filler, an insulating layer having a high dielectric constant can be obtained.
It is possible to inexpensively manufacture a multilayer substrate having excellent heat resistance and reliability. That is, since it does not contain a base material such as glass cloth, a large amount of high dielectric constant inorganic filler can be blended,
The dielectric constant of the insulating layer can be increased.

Further, since the base material such as glass cloth does not affect the dielectric characteristics, the dielectric constant of the insulating layer can be effectively increased. Furthermore, since the molding is performed using a molding material that uses a thermosetting resin, a multilayer substrate having excellent heat resistance and reliability can be obtained at low cost. Since the outer shape of the obtained multi-layer substrate is given by the molding die at the time of molding, the outer shape processing step using a punch press or a router is not required.

[0024]

EXAMPLES The present invention will be described below based on examples.
The invention is not limited to this example.

Example 1 Preparation of molding material 100 parts by weight of ortho-cresol-volac type epoxy resin (ESCN-195-3, Sumitomo Chemical Co., Ltd.) having an ICI viscosity of 0.3 Pa · s at 150 ° C. ), Phenol novolac resin (Hitachi Chemical Co., Ltd., HP-800N) 50 parts, 1,8 diazabicyclo- (5,4,0) -undecene-7 (DBU) 1 part, 1
Ceramic powder mixed powder for ceramic capacitors having a dielectric constant of 1100 at 25 kHz at 25 kHz (combined powder N3300-M for ceramic capacitors manufactured by Fuji Titanium Industry Co., Ltd.
Powder that is calcined at 50 ° C for 3 hours and ground by a ball mill) 1
065 parts (corresponding to 60% by volume) were mixed and kneaded for 15 minutes by a two-roll machine at 80 ° C.

Manufacture of Multilayer Substrate Next, as shown in FIG. 1A, the depth is 0.8 mm in both upper and lower sides.
Low pressure transfer mold with cavity of 0.4, thickness 0.4
Two glass epoxy double-sided printed wiring boards having a size of 2 mm were arranged so as to contact the inner surfaces of the upper and lower mold cavities, respectively. The molding material was transferred and molded between the printed wiring boards by a low-pressure transfer press at 175 ° C., 7 MPa, 90 seconds, and post-cured at 175 ° C. for 5 hours to give a thickness of 1.6 mm and 100 m.
An m-square multilayer substrate was obtained.

Example 2 Preparation of Molding Material 100 parts of biphenol type epoxy resin (Yuka-Shell Epoxy Co., Ltd., YX-4000H) having an ICI viscosity of 0.01 Pa · s at 150 ° C., phenol novolac resin (used in Example 1) (Same as I had) 50 copies, 1,8
Diazabicyclo- (5,4,0) -undecene-7 (D
BU) 3 parts, and 1080 parts (corresponding to 60% by volume) of the compounded powder for ceramic capacitor used in Example 1 (corresponding to 60% by volume) were mixed and kneaded for 15 minutes by a two-roll machine at 80 ° C. Hereinafter, a multilayer substrate was manufactured in the same manner as in Example 1.

Example 3 Preparation of molding material 100 parts of biphenol type epoxy resin (same as used in Example 2), phenol novolac resin (Example 1)
50 parts, 1,8 diazabicyclo-
3 parts of (5,4,0) -undecene-7 (DBU), mixed powder fired powder 1 for ceramic capacitor used in Example 1
680 parts (corresponding to 70% by volume) were mixed and kneaded for 15 minutes with a two-roll machine at 80 ° C. Hereinafter, a multilayer substrate was manufactured in the same manner as in Example 1.

COMPARATIVE EXAMPLE 1 A dicyandiamide-curing epoxy resin varnish was mixed with 67 vol% of the compound powder fired powder for ceramic capacitors used in Example 1 relative to the solid content of the varnish on a three-roll mill to give a thickness of 0. A 2 mm glass cloth was impregnated and dried to obtain a prepreg. As shown in FIG. 2 (a), four prepregs and two copper foils are laminated and pressed at 170 ° C.
It was heated and pressed for 90 minutes to obtain a copper clad laminate. Figure (b)
An inner layer circuit was formed as shown in to obtain an inner layer plate.

Further, as shown in FIG. 2 (c), two ordinary prepregs containing no high-dielectric particles and one copper foil are placed on both sides of the inner layer plate, and pressed at 170 ° C.,
It was heated and pressed for 90 minutes to obtain a multilayer substrate. The ratio of the resin / glass cloth / calcined powder for ceramic capacitors in the high dielectric constant insulating layer of the substrate is 45/25/3 in volume%.
It was 0.

Comparative Example 2 A multilayer substrate was obtained in the same manner as Comparative Example 1 except that 114% by volume of the compounded powder for ceramic capacitors was used with respect to the solid content of the varnish. The ratio of resin / glass cloth / calcined powder for ceramic capacitor in the high dielectric constant insulating layer of the substrate was 30/25/40 in volume%.

Comparative Example 3 Polyethersulfone resin (Sumitomo Chemical Co., Ltd., 4
100 G) 100 parts, 170 parts (30% by volume) of the compounded powder fired powder for ceramic capacitor used in Example 1 330
Kneading was carried out at a temperature to obtain a molding material. Two printed wiring boards used in the examples were placed in an injection molding die in the same manner as in the examples, and the above molding material was injection-molded to obtain a multilayer substrate having a thickness of 1.6 mm.

Using the thus obtained multilayer substrate, the relative dielectric constant at 1 kHz and 25 ° C., the presence or absence of voids in the substrate, and the solder heat resistance were evaluated. The relative permittivity is
The capacitance between the second layer and the third layer was measured using an LCR meter (manufactured by Hewlett Packard, model 4274A) and calculated. The evaluation of voids in the substrate was performed by removing the copper foil on the surface layer and using a soft X-ray device (BR-1505 type, Hitachi, Ltd.). The solder heat resistance was evaluated by observing swelling and peeling after 20 seconds at 260 ° C. using a normal substrate according to JIS C6481. The results are shown in Table 1.

[0034]

[Table 1]

The dielectric constants of the multilayer substrates of Examples 1 and 2 are 5 times those of Comparative Example 1, and the multilayer substrates of Example 3 are 7 times or more that of Comparative Example 1. In Comparative Example 2 in which the blending amount of the inorganic filler was large, the fluidity of the resin was poor, and the resin contained a large amount of voids and could not be molded. It can be seen that the multilayer substrate of Comparative Example 3 is inferior in solder heat resistance because the material is a thermoplastic resin.

[0036]

EFFECTS OF THE INVENTION Since the multilayer substrate of the present invention can contain a large amount of a high dielectric constant filler in a molding material to be an insulating layer, a multilayer substrate having an insulating layer having a significantly high dielectric constant can be efficiently obtained. be able to. Further, since the thermosetting epoxy resin is used for molding, it is possible to inexpensively obtain a substrate having excellent reliability such as solder heat resistance.

[Brief description of drawings]

FIG. 1 (a) is a cross-sectional view of an example in which a printed wiring board is placed in a molding die in the method of the present invention, (b) is a cross-sectional view of the obtained multilayer substrate, and (c) is a plated through-hole formed on it. It is sectional drawing of what was done.

FIG. 2 is a cross-sectional view showing a procedure for manufacturing a multilayer substrate by a conventional method.

[Explanation of symbols]

 1 Upper mold 2 Lower mold 3 Cavity 4 Printed wiring board 5 Air gap 6 Sprue 7 High dielectric constant insulating layer 8 Multilayer substrate 9 Through hole 10 High dielectric constant prepreg 11 Copper foil 12 Inner layer circuit 13 Inner layer 14 Normal prepreg 15 High dielectric Insulating layer 16 Multilayer substrate

Claims (2)

[Claims] 1. A multi-layer substrate obtained by injecting and curing an epoxy resin containing a high dielectric constant inorganic filler and a curing agent in a void formed between printed wiring boards arranged so as not to contact each other. 2. A printed wiring board is arranged in a cavity formed by a molding die so that one surface is in contact with the inner surface of the cavity and the other surface is not in contact with each other, and a space formed between the printed wiring boards is arranged in the cavity. A method for producing a multilayer substrate, which comprises injecting and curing an epoxy resin containing an inorganic filler having a high dielectric constant and a curing agent.