JPH0567881A - Manufacture of multilayer wiring board - Google Patents

Abstract

PURPOSE:To manufacture a multilayer printed circuit board which has no pinhole in an insulating layer, a small thickness tolerance of the layer and excellent heat resistant cycle characteristic of through holes or viaholes with high productivity. CONSTITUTION:A method for manufacturing a multilayer circuit board has the steps of forming an insulating layer 5 covering a conductor circuit 2 on the surface of a board 3 on which the circuit 2 is previously formed and then repeatedly again forming a conductor layer 7 on the surface of the layer 5, and comprises the steps of coating and drying the surface of the board 3 with liquidlike insulating material 4 when the layer 5 is formed, and then laminating a filmlike insulating material 1.

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 multilayer wiring board in which a conductor circuit is formed over multiple layers.

[0002]

2. Description of the Related Art Conventionally, a multilayer wiring board of this type is manufactured by forming an insulating layer on the surface of a substrate on which a conductor circuit is previously formed, and then forming a conductive circuit on the surface of the insulating layer again. This insulating layer serves to insulate the upper and lower conductor circuits. Further, it has been proposed to manufacture a more multilayered build-up wiring board by repeating the formation of the insulating layer and the conductor circuit as described above.

As a method of forming the insulating layer, for example, (a) a method of applying a liquid insulating material made of a photosensitive resin on the surface of the substrate and then hardening the insulating material,
(b) a film such as polyethylene is coated with the insulating material and dried to form a semi-cured dry film.
There is known a method of thermocompression-bonding the dry film-shaped insulating material on the surface of the substrate by a laminating machine.

[0004]

Comparing the above methods of forming an insulating layer, in the method (a) using a liquid insulating material, it is necessary to make the insulating layer surely follow an uneven base. Is advantageous in that However, in the method (a), it is difficult to form a thick insulating layer by a single coating operation, because there is a problem that if it is thickly formed at one time, insufficient curing easily occurs (due to residual diluent solvent). ,
In order to secure a sufficient film thickness, it is necessary to repeatedly apply multiple coats. Therefore, not only the surface smoothness of the formed film is deteriorated, but also the productivity of the wiring board is affected. Also, with this method, it becomes difficult to control the thickness of the insulating layer in detail, and the thickness tolerance is ± 2 as shown in FIG.
It tends to be as large as 0%.

On the other hand, the method (b) using the insulating material in the form of a dry film is advantageous in that even if a relatively thick insulating layer is formed, it can be formed by thermocompression once. Further, the film thickness of the insulating layer can be controlled to some extent, and the film thickness tolerance is about ± 10%, which is not as large as the above method. However, since this insulating material is thermocompression-bonded in a semi-cured state, it is inferior to the liquid insulating material used in the method (a) in conformity to the uneven base. Therefore, in the wiring board manufactured by the method (b), as shown in FIG. 4, a gap may be formed between the conductor circuit and the insulating material, and the insulating layer is easily peeled off.
In addition, pinholes are likely to occur in such an insulating layer, and a decrease in withstand voltage cannot be avoided.

From the above circumstances, (a) or (b)
It was difficult to manufacture a build-up multilayer wiring board that is sufficiently satisfactory in reliability and practicality by applying any of the above methods.

The present invention has been made in view of the above problems, and an object thereof is to follow an insulating layer having a sufficient film thickness and a small film thickness tolerance to a base on which the insulating layer is formed. An object of the present invention is to provide a method for manufacturing a multilayer wiring board that can be reliably formed without impairing the property.

[0008]

In order to solve the above-mentioned problems, in the present invention, an insulating layer for covering the conductor circuit is formed on the surface of the substrate on which the conductor circuit is formed in advance, and then the In the method of manufacturing a multilayer wiring board by repeating the process of forming a conductor circuit again on the surface of the insulating layer, when forming the insulating layer, a liquid insulating material is applied and dried on the surface of the substrate. After the insulating layer is formed by using the above method, a film-shaped insulating material is laminated. Further, it is desirable that the insulating layer has substantially the same thickness as the conductor circuit.

According to this method, by applying a liquid insulating material in advance, the surface of the substrate having irregularities is
The liquid insulating material can be reliably followed. Then, by laminating the film-shaped insulating material after drying the liquid insulating material, the generation of the voids on the side surface of the conductor circuit and the generation of pinholes on the surface of the insulating layer are reliably prevented. In addition, an insulating layer having a sufficient film thickness and having a small film thickness tolerance can be easily formed.
Therefore, unlike the conventional method using only a liquid insulating material or only a film-shaped insulating material, it becomes possible to manufacture a multilayer wiring board provided with a suitable insulating layer in which the drawbacks of both are eliminated. Further, in the multilayer wiring board obtained by the manufacturing method of the present invention, since the insulating layer is composed of the portion where the liquid insulating material is cured and the portion where the film-shaped insulating material is cured, Anisotropy occurs in the expansion coefficient.
As a result, the stress due to thermal expansion can be relaxed, and the heat resistant cycle characteristics of via holes and through holes are improved.

The method for manufacturing the above-mentioned multilayer wiring board will be described in more detail below in accordance with steps. As the substrate used in the present invention, for example, a glass epoxy resin substrate or a glass polyimide resin substrate containing an ultraviolet shielding material is preferable. A conductor circuit made of a metal such as copper, nickel, tin, gold or silver is formed on this substrate according to a conventional method such as a subtractive method, a part-additive method and a full-additive method. Alternatively, a substrate to which a metal plate such as copper is attached in advance may be used, and the metal plate on which a conductor circuit is formed by etching or the like may be used. It is preferable that the surface of the conductor circuit formed on the substrate is roughened by any method such as polishing treatment or blackening reduction treatment, whereby adhesion when an insulating layer is formed on the substrate The property is improved.

Next, the liquid insulating material and the film-shaped insulating material laminated thereon will be described in detail. Of the liquid insulating material and the film-shaped insulating material,
At least one of them preferably contains a filler (heat-resistant resin fine particles) soluble in an acid or an oxidizing agent. Further, it is preferable that the filler is dispersed in a heat-resistant resin liquid which is hardly soluble in an acid or an oxidant by a curing treatment.

As the heat-resistant resin fine particles used as the filler, for example, it is preferable to use powders of epoxy resin, polyester resin, bismaleimide-triazine resin, melamine resin and the like, and the size of such resin fine particles. Is 0 as a range in which the desired anchor effect is obtained.
It is preferably about 1 μm to 10 μm. As the heat-resistant resin, it is preferable to use an epoxy resin, an epoxy-modified polyimide resin, a polyimide resin, a phenol resin, or the like, and these resins have photosensitivity. To such a resin liquid, after mixing a predetermined amount of the above resin filler and adding a curing agent, for example,
By adding a solvent such as butyl cellosolve acetate and stirring, a varnish of an insulating material in which the resin filler is uniformly dispersed can be obtained.

When a varnish of a liquid insulating material is produced from the above raw materials, it is desirable that the viscosity of the varnish is adjusted to 10 Pa · S or less. This is because if the viscosity of the varnish is higher than this value, the fluidity of the varnish is lost, and the followability to the uneven base is deteriorated.

The liquid insulating material preferably has a hydroxyl equivalent of 500 or less. The reason is that the hydroxyl group equivalent is small, that is, the number of hydroxyl groups in one molecule is large, which means that the insulating material contains many oxygen atoms. This is because the adhesion of the conductor circuit is improved. Therefore, when the hydroxyl group equivalent is larger than the above range, the adhesion of the conductor circuit is deteriorated and peeling easily occurs.

When the above insulating material is adjusted to a varnish, it is preferable that the varnish of the liquid insulating material does not contain a solvent. The reason for this is that if the varnish contains a solvent, shrinkage is likely to occur due to curing treatment such as heating, and the dimensional accuracy of the formed insulating layer is reduced.

As the filler mixed in the liquid insulating material, inorganic fine particles may be contained in place of the resin filler. This is because if the inorganic filler is used, it does not shrink even when a curing treatment such as heating is performed, and it is possible to reliably prevent a decrease in dimensional accuracy of the insulating layer. Further, the filling rate of the inorganic filler is preferably 10% to 80%. The reason is that if the filling rate is set within the above range, it is possible to prevent deterioration of dimensional accuracy without deteriorating the characteristics of the substrate.

Next, a method for producing a film-shaped insulating material using the above raw materials will be described. It is desirable that the film-shaped insulating material and the liquid insulating material have the same composition. The reason is that if the two insulating materials have the same composition, the adhesiveness between them is improved and peeling can be prevented. Further, even if the curing treatment is performed by heating or the like, since the shrinkage rates are the same, the adverse effect due to the dimensional change is relatively small.

The varnish of the film-shaped insulating material produced from the above-mentioned raw materials is applied onto the surface of a flexible film substrate such as polyethylene or polypropylene by any conventional method. Then, the applied varnish is used for lamination after being adjusted to a semi-cured state (B stage) by heat treatment. Further, the varnish-coated surface of the film may be subjected to a release treatment. According to this treatment, after the film-shaped insulating material is laminated on the substrate, only the film base material can be easily released from the material.

Next, a method for forming an insulating layer using a liquid or film-shaped insulating material will be described in detail. As a method of applying the varnish of the liquid insulating material onto the surface of the substrate, various means such as roll coating, dip coating, spray coating, spinner coating, curtain coating and screen printing may be used. it can. The varnish of the insulating material may be at least as thick as the conductor circuit (20 μm to 30 μm) by any method.
m) must be applied.

After applying the varnish of the liquid insulating material, it is desirable to smooth the surface with a squeegee or the like. The reason is that a squeegee is used to scrape off excess varnish on the conductor circuit and to make the varnish have a constant film thickness. Therefore, when a film-shaped insulating material is pressure-bonded to the varnish-coated surface to form the insulating layer, the thickness tolerance is reduced and the surface smoothness is improved.

As another method of smoothing the varnish-coated surface, it is desirable that the varnish is coated and dried, and then the surface is polished to expose the conductor circuit. According to this method, even after the varnish is dried, the excess varnish on the conductor circuit can be removed, and the film thickness of the varnish can be made the same as the film thickness of the conductor circuit.

Before applying the varnish of the liquid insulating material to the substrate, it is desirable to keep the substrate at 40 ° C. to 70 ° C. in advance. When the temperature of the substrate is lower than the above range, the fluidity of the varnish is lowered and the followability to the base is deteriorated. If the substrate temperature is higher than the above range, the fluidity of the varnish will be too high. Therefore, it is necessary to increase the number of times of coating in order to secure a predetermined film thickness, and the surface smoothness of the insulating layer tends to deteriorate.

Then, after the varnish of the liquid insulating material is applied and dried as described above, the film-shaped insulating material is laminated on the varnish by a laminator, thereby forming an insulating layer having a two-layer structure. ..

After laminating the film-shaped insulating material, it is desirable that a liquid insulating material is further applied and dried. Even if it is an insulating layer having the above-mentioned two-layer structure, suitable surface smoothness can be ensured, but by applying and drying a varnish of the above-mentioned insulating material thereon, an insulating layer having more excellent smoothness is formed. This is because that.

After forming the insulating layer with the liquid insulating material and the film-shaped insulating material, a portion of the surface of the insulating layer which will be a blind via hole (hereinafter referred to as BVH) is covered with a mask. By exposing and developing in this state, the exposed portion is cured and the covered portion is opened.

When the liquid insulating material and the film-shaped insulating material have different compositions, it is desirable to form an opening in the liquid insulating material in advance, laminate the film-shaped insulating material, and then open the film-shaped insulating material. .. In this case, since the resins constituting the insulating material have different photosensitivities, it is necessary to set the exposure amount, the developing conditions, etc. according to the photosensitivity of each resin.

After the BVH is formed by the above method, the insulating layer is roughened with an acid or an oxidizing agent, whereby only the resin filler portion is selectively dissolved. Examples of the acid or oxide include chromic acid, chromate, permanganate, ozone, etc. By treating the insulating layer with these, countless micropores as anchors are formed on the surface of the insulating layer. And on the inner surface of the BVH. If a conductor circuit is formed on the surface having such fine holes, a so-called anchor effect is obtained, and as a result, the conductor circuit is less likely to peel off.

Catalyst nuclei such as palladium-tin colloid are preferably provided on the rough surface of the insulating layer surface and the inner surface of the BVH. This is because the rough surface is activated by this treatment, so that the metal is easily deposited when electroless plating is performed. Then, when a desired conductor circuit is formed on the surface and the inner surface which have been subjected to the above-mentioned treatment, a plating resist for electroless plating is laminated only on a portion where the conductor circuit is not formed. As the plating resist, for example,
A dry film having photosensitivity is suitable. By using such a dry film, it is possible to form a fine conductor circuit reliably and with high accuracy. In the state where the resist is laminated, electroless copper plating, electroless nickel plating, electroless tin plating, electroless gold plating, electroless silver plating, etc. are performed to obtain the insulating layer surface and BV.
The above metal is deposited on the conductor circuit forming portion on the inner surface of H.
As a result, a multilayer wiring board having desired conductor circuits on the surface of the insulating layer and the inner surface of the BVH is manufactured.

The conventional multi-layered wiring board obtained by the above method is different from the conventional wiring board formed by only the liquid insulating material or only the film-shaped insulating material, and has a suitable insulating layer in which the drawbacks of both are eliminated. I have it. Therefore, the insulating layer is not peeled off and the surface smoothness is not deteriorated. Further, even when this method is further repeated to manufacture a wiring board having more layers, it is possible to impart sufficient reliability and practicality to the wiring board.

[0030]

EXAMPLES AND COMPARATIVE EXAMPLES Examples 1 to 6 embodying the present invention and Comparative Examples 1 and 2 for each Example will be described in detail below with reference to the drawings. [Embodiment 1] Steps (1) to (12) constituting the method for manufacturing a multilayer printed wiring board according to Embodiment 1 will be described with reference to FIG.
Description will be made based on (f).

Step (1): 70 parts by weight of 50% acrylate of phenol novolac type epoxy resin (Nippon Kayaku, trade name, EOCN-104 S), bisphenol A type epoxy resin (made by Yuka Shell, trade name, Epicoat 1001 [hydroxyl group equivalent 457, molecular weight 900, number of hydroxyl groups in one molecule 1.97] 30 parts by weight, benzyl dimethyl ketal (manufactured by Ciba-Geigy, trade name, Dolka Cure 651) 3 parts by weight, imidazole (manufactured by Shikoku Kasei, product) (2PHZ) 5 parts by weight, and 25 parts by weight of epoxy resin fine powder (trade name, manufactured by Toray, trade name, Trepearl) having an average particle size of 0.5 μm, and then kneading the mixture with a three-roller. Then, a raw material for an insulating material made of a photosensitive resin was manufactured.

Step (2): Next, methyl ethyl ketone was added to the raw material for the insulating material produced in the step (1) to prepare a varnish for the film-like insulating material 1 having a solid content of 50%. Then, the varnish was applied onto a polyethylene film having a thickness of 40 μm and subjected to a mold release treatment using a doctor bar. After that, the applied varnish is put in a B stage in an IR furnace, that is, in an uncured state and the solvent is removed,
A dry film D having the film-shaped insulating material 1 having a film thickness of 50 μm was manufactured.

Step (3): After laminating a photoresist on a copper clad laminate (Hitachi Chemical Co., Ltd., trade name, MCL-E-67), exposure and development are carried out, as shown in FIG. 1 (a). And an inner layer plate 3 provided with an inner layer circuit 2 having a thickness of 35 μm.
Formed.

Step (4): Next, the surface of the inner layer circuit 2 of the inner layer plate 3 obtained in the step (3) is blackened and reduced by a conventional method and then heat treated at 120 ° C. for 30 minutes. It was left to cool to room temperature in a desiccator.

Step (5): A varnish of the liquid insulating material 4 having a solid content of 75% was prepared from the raw material for the insulating material produced in the step (1) using butyl cellosolve acetate. Then, as shown in FIG. 1B, after applying the varnish to the inner layer plate 3 using a roll coater, the inner layer plate 3
The excess varnish above was scraped off with a squeegee. Then, the varnish is dried at 80 ° C. for 60 minutes to give a film thickness of 3
An insulating layer 4a made of a liquid insulating material 4 having a thickness of 5 μm was formed.

Step (6): Next, heat the dry film D obtained in the step (2) on the insulating material layer 4a with a laminator so that the film-shaped insulating material 1 is bonded to the film. Crimped. As shown in FIG. 1C, the insulating layer 4
An insulating layer 5 made of a and the film-shaped insulating material 1 was obtained.

Step (7): Next, the portion other than the portion where BVH6 is formed was exposed to 300 mJ / cm ² by an ultraviolet irradiation device and cured. Then, after removing only the polyethylene film F from the dry film D, development was performed using a chlorocene solution to remove the insulating layer 5 at the portion where the BVH6 is formed, that is, the film-shaped insulating materials 1 and 4a.

Step (8): Next, after further exposing the portion other than BVH6 with an ultraviolet irradiation device at 3 J / cm ² ,
Heat treatment was performed at 100 ° C. for 1 hour and at 150 ° C. for 3 hours to form an insulating layer 5 having BVH6 in a predetermined position (see FIG. 1).
(See (d)).

Step (9): Then, a chromic acid solution (Cr
The surface of the insulating layer 5 and the inner surface of the BVH 6 are roughened by immersing in O ₃ (800 g / liter, 70 ° C.) for 10 minutes, and the chromic acid is removed by washing with water after neutralization (FIG. 1).
(See (e)).

Step (10): The inner layer plate 3 obtained in the above step is immersed in a commercially available palladium-soot colloid to form a catalyst nucleus layer on the surface of the insulating layer 5 and the inner surface of the BVH 6, and then at 30 ° C. at 30 ° C. Heat treatment was performed for 1 minute.

Step (11): Next, a dry film photoresist was laminated on the surface of the insulating layer 5 and then exposed and developed to form a plating resist. Step (12): Then, the inner layer board 3 obtained in the above step is immersed in an electroless plating solution for 15 hours to obtain a multilayer printed wiring board having an outer layer circuit 7 having a thickness of 15 μm and a conductor circuit 8 in the BVH 6. Formed (see FIG. 1 (f)). [Embodiment 2] Each step constituting the method for manufacturing the multilayer printed wiring board of Embodiment 2 will be described below.

Steps (1) to (4): The steps (1) to (4) of Example 1 were followed. Step (5): From the raw material for the insulating material prepared in the step (1), using butyl cellosolve acetate, a viscosity of 1 Pa ·
A varnish of S liquid insulating material 4 was prepared. And 50
The varnish was applied to the inner layer plate 3 heated to 0 ° C. using a curtain coater, and then heat treatment was performed at 80 ° C. for 30 minutes to form the insulating layer 4a.

Step (6): Next, as shown in FIG.
The surface of the inner layer circuit 2 of the inner layer plate 3 was exposed by buffing to make the insulating layer 4a and the inner layer circuit 2 have the same thickness. Steps (7) to (12): After that, a multilayer printed wiring board was formed according to the steps (7) to (12) of Example 1. [Embodiment 3] Each step constituting the method for manufacturing a multilayer printed wiring board of Embodiment 3 will be described below.

Steps (1) to (4): The steps (1) to (4) of Example 1 were followed. Step (5): From the raw material for the insulating material produced in the step (1), butyl cellosolve acetate is used to obtain a solid content of 75.
% Liquid insulating material 4 varnish was prepared.

Step (6): The inner layer plate 3 was coated with the varnish using a roll coater to form the insulating layer 4a, and then dried at 80 ° C. for 60 minutes. Then, the dry film D obtained in the step (2) was thermocompression bonded using a laminator, and the film-shaped insulating material 1 was laminated on the liquid insulating material 4. Then, the varnish of the liquid insulating material 4 obtained in the step (5) is applied thereonto at 80 ° C. for 3
The insulating layer 4b was formed by drying for 0 minutes. As a result, an insulating layer 9 having a three-layer structure as shown in FIG. 3 was obtained.

Steps (7) to (12): After that, a multilayer printed wiring board was formed according to the steps (7) to (12) of Example 1. [Embodiment 4] Each step constituting the method for manufacturing a multilayer printed wiring board of Embodiment 4 will be described below.

Steps (1) to (4): The steps (1) to (4) of Example 1 were followed. Step (5): 60% by weight of 50% acrylate of phenol novolac type epoxy resin (made by Yuka Shell, trade name, Epicoat 180S), bisphenol A epoxy resin (made by Yuka Shell, trade name, Epicoat 1001) 40 Parts by weight, 2-methyl [4- (methylthio) phenyl] -2-morpholinopropane-1 (manufactured by Ciba-Geigy, trade name, Dolphin Cure 907) 4 parts by weight, dicyandiamide (manufactured by Yuka Shell, trade name, DICY7) 5 Parts by weight, and 20 parts by weight of an epoxy resin fine powder (trade name, Toray Pearl, manufactured by Toray) having an average particle size of 0.5 μm, and then kneaded with a three-roller to form an insulating material made of a photosensitive resin The raw material was manufactured.

Step (6): Using butyl cellosolve acetate from the raw material for the insulating material produced in the step (5),
A varnish of the liquid insulating material 4 having a solid content of 75% was prepared, and the varnish was applied to the inner layer plate 3 using a roll coater.
Then, after scraping off the excess varnish on the inner layer plate 3 with a squeegee, it was dried at 80 ° C. for 60 minutes.

Steps (7) to (12): After that, a multilayer printed wiring board was formed according to the steps (6) to (12) of Example 1 above. [Embodiment 5] Each step constituting the method for manufacturing a multilayer printed wiring board according to Embodiment 5 will be described below.

Steps (1) to (4): The steps (1) to (4) of Example 1 were followed. Step (5): 60 parts by weight of 50% acrylate of phenol novolac type epoxy resin (produced by Yuka Shell, trade name, Epicoat 154) (hydroxyl group number 360, molecular weight 1600, number of hydroxyl groups per molecule 4.44), Bisphenol A type epoxy resin (Yukaka Shell, trade name, Epicoat 1004) 40 parts by weight, 2-hydroxy-2-methyl-1-phenylpropan-1-one (Merck, trade name, Darocur 103) 5 parts by weight , Imidazole (manufactured by Shikoku Kasei, trade name, 2PHZ) 4 parts by weight, and silica fine powder (manufactured by Admatex, trade name, Admafine SO-25R) having an average particle diameter of 0.8 μm, 50 parts by volume, By kneading with a ball mill, a raw material for an insulating material made of a photosensitive resin was manufactured.

Step (6): A varnish of the liquid insulating material 4 having a solid content of 70% is prepared from the raw material for the insulating material produced in the above step (5) by using butyl cellosolve acetate, and the varnish is formed by using a roll coater. It was applied to the inner layer plate 3. Then, after scraping off the excess varnish on the inner layer plate 3 with a squeegee, it was dried at 80 ° C. for 60 minutes.

Step (7): Next, the portion other than BVH6 is exposed to 200 mJ / cm ² by an ultraviolet irradiation device and cured, and then the portion of the film-like insulating material 1 in the insulating layer 5 of the BVH 6 portion is chlorothane. It was removed by developing using the solution.

Step (8): The dry film D obtained in the step (2) is thermocompression-bonded by a laminator to laminate the film-shaped insulating material 1 and then the polyethylene film F.
Only removed. Then, the portion other than 6 parts of BVH is exposed to 300 mJ / cm ² by an ultraviolet irradiation device and cured, and then the portion of the liquid insulating material 4 of the insulating layer 5 of 6 parts of BVH is developed using a chlorocene solution. Removed.

Steps (9) to (12): A multilayer printed wiring board was formed according to the steps (8) to (12) of Example 1 above. [Embodiment 6] Each step constituting the method for manufacturing a multilayer printed wiring board of Embodiment 6 will be described below.

Steps (1) to (4): The steps (1) to (4) of Example 1 were followed. Step (5): 50% acrylate of cresol novolac type epoxy resin (manufactured by Nippon Kayaku, trade name, ECON-104 S) 60 parts by weight, bisphenol A type epoxy resin (made by Yuka Shell, trade name, Epicoat 1007 [ Number of hydroxyl groups 322, molecular weight 2900, number of hydroxyl groups per molecule 9.01] 40 parts by weight, benzyl dimethyl ketal (manufactured by Ciba-Geigy, trade name, Irgacure 651) 3 parts by weight, imidazole (manufactured by Shikoku Kasei, trade name, 2PHZ) After mixing 5 parts by weight and 3 parts by weight of trimethylpropanetriacrylate (manufactured by Shikoku Kasei, trade name, NK ester A-TMPT), a raw material for an insulating material having a photosensitive resin was manufactured by stirring with a homogenizer. ..

Step (6): The inner layer plate 3 obtained in the step (4) of Example 1 is heated to 70 ° C., and the raw material for the insulating material prepared in the step (5) is used as an inner layer using a GAP coater. It was applied to plate 3. Then, heat treatment was performed at 80 ° C. for 10 minutes.

Steps (7) to (12): A multilayer printed wiring board was formed according to the steps (7) to (12) of Example 5. Comparative Example 1 In Comparative Example 1, a multilayer printed wiring board was manufactured using only the liquid insulating material. Each step constituting this manufacturing method will be described below.

Steps (1) to (3): The steps (1), (3) and (4) of Example 1 were followed. Step (4): A varnish having a solid content of 75% is prepared from butyl cellosolve acetate from the raw material for an insulating material produced in the step (1), and the varnish is obtained by using a roll coater in the step (3). After applying to No. 3, it was dried at 80 ° C. for 5 minutes.

Step (5): Further, the varnish prepared in the step (4) was applied again to the inner layer plate 3 and dried at 80 ° C. for 5 minutes. Then, after repeating this coating and drying three times,
It was dried at 80 ° C. for 60 minutes to obtain the insulating layer 11 shown in FIG.

Steps (6) to (12): A printed wiring board was formed according to the steps (7) to (12) of Example 1. [Comparative Example 2] In Comparative Example 2, a multilayer printed wiring board was manufactured using only a film-shaped insulating material. Each step constituting this manufacturing method will be described below.

Steps (1) to (4): The steps (1) to (4) of Example 1 were followed. Step (5): Next, on the inner layer plate 3 obtained in the step (4),
The dry film obtained in step (2) was thermocompression bonded by a laminator to obtain the insulating layer 10 shown in FIG.

Steps (6) to (12): A printed wiring board was formed according to the steps (7) to (12) of Example 1 above. In order to compare and evaluate the characteristics of the insulating layer in each of the printed wiring boards of Examples 1 to 6 and Comparative Examples 1 and 2 manufactured by the above method, the time for forming the insulating layer, the pinhole of the insulating layer, and the insulating layer The film thickness tolerance and the rate of change in resistance due to the heat cycle test were investigated. The results are shown in Table 1.

[0063]

[Table 1]

As is clear from Table 1, except for Comparative Example 1 in which the liquid insulating material needs to be repeatedly applied, the insulating layer can be formed relatively easily, so that the productivity is good. It was Observation of these multilayer wiring boards revealed that in the multilayer wiring board of Comparative Example 2, the ability to follow the underlying layer of the insulating layer 10 was poor and voids V were formed on the side surfaces of the inner layer circuit 2. Further, some pinholes P were found on the surface of the insulating layer 10. On the other hand, in the multilayer wiring boards of Examples 1 to 6 and Comparative Example 1, no void V or pinhole P was found in the insulating layer. Furthermore, as a result of investigating the thickness tolerance of the insulating layer, the multilayer wiring board of Comparative Example 1 shown in FIG. 5 has a thickness tolerance of ± 20%, and the formed insulating layer 11 has poor surface smoothness. In the multilayer wiring boards of Examples 1 to 6 and Comparative Example 2, the film thickness tolerance was ± 2%.

Further, as a result of the vapor phase heat cycle test (-65 ° C. to 125 ° C., 1000 times) of the via holes, the multilayer wiring boards of Comparative Examples 1 and 2 showed a resistance change rate of the via holes of 12% to 13%. It became large, but each Example 1-6
Then, it was as good as 2% to 3%.

In each of Examples 1 to 6, the time required to form one insulating layer was 3.5 hours.
As in the case of laminating the film as described above, a time substantially the same as that of the film was sufficient. It is considered that the reason is that the amounts of the liquid insulating material and the film-shaped insulating material were smaller than those when used alone, and the time required for drying and curing was shortened. It was proved that the methods of ~ 6 are excellent in productivity.

When the above results are put together, it is clear that the characteristics of the multilayer wiring boards obtained in the respective examples are excellent.

[0068]

As described above in detail, according to the method for manufacturing a multilayer wiring board of the present invention, an insulating layer having a sufficient film thickness and having a small film thickness tolerance is applied to a base on which the insulating layer is formed. It has an excellent effect that it can be surely formed without impairing the followability. Further, it also has an excellent effect that the thermal cycle characteristics of the via hole and the through hole can be improved.

[Brief description of drawings]

1A to 1F are schematic views showing a manufacturing process of a multilayer wiring board according to a first embodiment.

FIG. 2 is a schematic view showing one manufacturing process of the multilayer wiring board of Example 2.

FIG. 3 is a schematic view showing one manufacturing process of the multilayer wiring board of Example 3;

FIG. 4 is a schematic view showing a multilayer wiring board of Comparative Example 2.

5 is a schematic view showing a multilayer wiring board of Comparative Example 1. FIG.

[Explanation of symbols]

1 (film-like) insulating material, 2,7 inner layer circuit and outer layer circuit as conductor circuit, 3 inner layer plate as substrate,
4 insulating material (in liquid state), 4a insulating layer (formed of liquid insulating material), 5 insulating layer.

Claims (8)

[Claims] 1. An insulating layer (5) for covering the conductor circuit (2) is formed on the surface of a substrate (3) on which the conductor circuit (2) is formed, and then the surface of the insulating layer (5). In the method for producing a multilayer wiring board by repeating the process of forming the conductor circuit (7) again on the substrate (3), the liquid insulating material (4) is added to the substrate (3) when the insulating layer (5) is formed. The method for producing a multilayer wiring board is characterized in that the insulating layer (4a) is formed by coating and drying on the surface of (4), and then the film-shaped insulating material (1) is laminated. 2. The method for manufacturing a multilayer wiring board according to claim 1, wherein after the liquid insulating material (4) is applied, the surface is smoothed to form an insulating layer (4a). 3. The multilayer wiring board according to claim 1, wherein the liquid insulating material (4) is applied and dried, and then the surface thereof is polished to expose the conductor circuit (2). Production method. 4. The liquid insulating material (4) has a viscosity of 10 Pa.
・ S is adjusted to be less than or equal to S.
A method for manufacturing the multilayer wiring board according to any one of 1. 5. The method for manufacturing a multilayer wiring board according to claim 1, wherein the liquid insulating material (4) contains inorganic fine particles. 6. The multilayer according to claim 1, wherein the substrate (3) is previously kept at 40 ° C. to 70 ° C. before applying the liquid insulating material (4). Wiring board manufacturing method. 7. At least one of the film-shaped insulating material (1) and the liquid insulating material (4) contains heat-resistant resin fine particles soluble in an acid or an oxidant. The method for manufacturing a multilayer wiring board according to claim 1. 8. An insulating layer (4a) formed in advance from a liquid insulating material (4) is opened, then a film-shaped insulating material (1) is laminated, and then the film-shaped insulating material (1) is opened. The method for manufacturing a multilayer wiring board according to claim 1, wherein