JP2919364B2 - Method for manufacturing multilayer printed wiring board - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method of manufacturing a multilayer printed wiring board, and more particularly to a method of manufacturing a multilayer printed wiring board capable of forming a fine pattern.

[0002]

2. Description of the Related Art Conventionally, a multilayer printed wiring board uses a copper-clad substrate to form an inner layer circuit by etching, roughens the inner layer circuit, and uses a prepreg in which an insulating resin is immersed in glass fiber as an interlayer insulating material. The inner circuit board is laminated and bonded to form a laminate, and then a hole is formed by drilling or the like, then electroless copper plating or electrolytic copper plating is performed, and the outermost circuit is etched.
In this method, there is a problem that the working efficiency is low because the internal circuit boards are laminated and adhered for a long time by using a heating and pressing press device using a prepreg of an interlayer insulating material.

As a method for solving this problem, FIG.
As shown in FIG. 6 (B), the adhesive resin 14 with a long copper foil is continuously roll-laminated on the inner circuit board 8 shown in FIG. 6 (A) via the heating laminating rolls 16a and 16b under normal pressure. Form a laminate. Thereafter, a method for manufacturing a multilayer printed wiring board characterized in that the adhesive resin 14 with copper foil is cured by heating and pressing to obtain a multilayer shield board 15 is disclosed in Japanese Patent Application Laid-Open No. 5-7094.

On the other hand, Japanese Patent Application Laid-Open No. Hei 5-136575 proposes the following manufacturing method as the above-mentioned improvement method.
That is, as shown in FIG. 7B, a photo-curable resin ink is applied by roll coating and screen printing on the entire surface of the inner layer circuit board 8 having a roughened circuit surface shown in FIG. To cure the undercoat layer 13
To form Thereafter, as shown in FIG. 7 (C), the adhesive resin 14 with the long copper foil is heated and laminated on both sides of the inner circuit board 8 on which the undercoat resin has been formed.
The laminate is formed by continuous roll lamination through b. Thereafter, the undercoat layer 13 is heated by heat treatment.
And the adhesive resin with copper foil 14 are integrally cured to form a multilayer shield plate 15. Next, a target multilayer printed wiring board is obtained by drilling, electroless copper plating or electrolytic copper plating, and further etching the outermost layer circuit.

[0005]

However, the above-mentioned conventional method for manufacturing a multilayer printed wiring board has the following problems. That is, Japanese Patent Laid-Open No. 5-709 shown in FIG.
No. 4, the adhesive resin with copper foil 14 is used for the inner circuit board 8
The method of laminating directly from both sides to obtain a laminate is as follows. The thermosetting resin is caused to flow by heating the laminating rolls 16a and 16b under normal pressure to remove air remaining between the inner layer circuits 7. In order to obtain a smooth surface of the laminate, after the adhesive resin 14 with the copper foil is roll-laminated, a heating and pressurizing operation by the laminating rolls 16a and 16b is required again, and there is a problem that workability is reduced. Further, by performing the heating and pressurizing operation using the laminating rolls 16a and 16b, distortion remains in the multilayer printed wiring board. When a solder flow or an infrared solder flow is performed when components are mounted on the multilayer printed wiring board, there is a problem that the distortion is released and warpage or twist occurs.

On the other hand, Japanese Patent Application Laid-Open No. 5-136575 discloses an improved method as described above.
4 before the lamination of the inner circuit 7 with the undercoat layer 13
And the step of the inner-layer insulating substrate 1 is reduced, so that the lamination time is shortened and the working efficiency is improved. However, on the other hand, it is possible to reduce the level difference between the inner-layer insulating substrate 1 and the inner-layer circuit 7 only by applying the photo-curable resin ink to the entire surface of the inner-layer circuit board 8 and curing it with ultraviolet rays, but it is possible to completely smooth the surface. It is very difficult to do. Thereafter, the adhesive resin 14 with a copper foil is adhered by the laminating rolls 16a and 16b. In the roll laminating method in a short time, the unevenness of the undercoat layer 13 caused by the inner layer circuit 7 is filled and the laminated body is formed. It is difficult to smooth the surface. As a result, irregularities occur on the copper foil surface of the multilayer shield substrate 15. Regarding the finish of the copper foil surface of the multilayer shield substrate 15, the step between the inner layer circuit 7 and the inner layer insulating substrate 1 was 30 μm at the maximum. This inner layer insulating substrate 1
Surface irregularities may cause hole burr and drill breakage during the drilling process,
In the process of forming the inner layer circuit 7, a circuit pattern abnormality such as a disconnection of the circuit due to insufficient adhesion of the etching resist on the uneven portion of the copper foil surface has been a serious problem.

On the other hand, when the undercoat layer 13 is formed,
By reducing the amount of ultraviolet irradiation and suppressing the degree of curing of the resin of the undercoat layer 13 and making the resin flexible, the laminate can be smoothed by laminating the adhesive resin 14 with a copper foil in a short time. However, due to the difference in the coating thickness of the photocurable resin ink on the inner layer circuit 7 and the inner layer insulating substrate 1, the photocuring of the photothermosetting resin particularly on the inner layer insulating substrate 1 becomes insufficient, and unreacted photocurable components The monomer remains in the undercoat layer 13.
This monomer was vaporized during the heating process after laminating the copper foil sheet, and as a result, voids were generated in the undercoat layer 13, resulting in a problem that the adhesion of the undercoat layer 13 was reduced.

An object of the present invention is to provide a method of manufacturing a multilayer printed wiring board which has solved the problems of the conventional method and has excellent smoothness on the surface of the copper foil and excellent adhesion of the insulating layer.

[0009]

According to the present invention, there is provided a method for manufacturing a multilayer printed wiring board comprising the following steps (A) to (E), particularly when forming an undercoat layer in step (B): By selectively changing the degree of cure of the undercoat resin on the inner layer circuit and the degree of cure of the undercoat resin on the inner layer insulating substrate, a multilayer shield substrate having excellent surface copper foil smoothness and insulating layer adhesion is provided. A method for producing a multilayer printed wiring board characterized by the above feature is obtained. (A) A step of forming a wiring pattern composed of a conductor layer on the surface of an insulating substrate to form an inner insulating substrate. (B) the inner layer insulating the photocurable resin ink is applied to the surface of the substrate, after the formation of a more undercoat layer to the first exposure for irradiating ultraviolet rays to the photocurable resin ink entire surface, the distribution
The underlayer excluding the undercoat layer on a line pattern;
UV light having a higher intensity than the first exposure on the surface of the coat layer
And smoothing the surface of the inner circuit board by the second exposure . (C) An adhesive resin with a copper foil obtained by coating a long copper foil with a resin composition containing a thermosetting resin as a main component is applied to the inner-layer insulating substrate on which the undercoat layer has been formed under normal pressure. A step of continuously performing roll lamination to form a laminate.

(D) A step of forming a multilayer shield substrate by heating the laminate and tightly and integrally curing the undercoat layer resin and the adhesive resin with copper foil. (E) A step of forming an outermost layer circuit after drilling and copper plating in the multilayer shield substrate.

[0011]

Embodiments of the present invention will now be described with reference to the drawings.

1 (A) to 1 (E), 2 (A) to
(E), FIG. 3, FIG. 4 (a), (b) and FIG.
(C) is sectional drawing shown in order of the process explaining the manufacturing method of the multilayer printed wiring board of one Embodiment of this invention. A method for manufacturing a multilayer printed wiring board according to an embodiment of the present invention includes the following steps (1) to (3).

(1) An inner layer process for forming an inner circuit board 8 constituting an inner layer of a multilayer printed wiring board as shown in FIGS. 1 (A) to 1 (E).

(2) As shown in FIGS. 2 (A) to 2 (E) and FIG. 3, an underlayer having a resin curing degree selectively changed on the inner circuit 7 and the inner insulating substrate 1 on the surface of the inner circuit board 8. A lamination step of forming a multilayer shield plate 15 by forming the coat resin layer 13 and then roll-laminating the adhesive resin 14 with copper foil.

(3) The multilayer shield substrate 15 shown in FIGS. 5A to 5C is drilled, electroless copper plating or electrolytic copper plating is performed, and the outer layer circuit 22 is formed by etching. A step of forming a wiring board;

The inner layer plate in the step (1) has a structure in which an epoxy resin is used as an insulating layer, and copper foil of 12 μm to 35 μm is provided as a conductor layer on both sides of the insulating layer.
A substrate having a thickness of 0.1 mm to 1.6 mm can be generally used. In the step of forming the inner layer circuit of the inner layer circuit board, first, as shown in FIG. 1A, a negative curing type photosensitive resin sheet 3 is used as an etching resist on the inner layer copper foil 2 of the inner layer insulating substrate 1. Laminate. Next, FIG.
As shown in (B), the inner layer circuit pattern is printed on the photosensitive resin sheet 3 by irradiating and irradiating ultraviolet rays 5 through the inner layer pattern negative film 4.

Next, as shown in FIG. 1C, after an etching resist layer 6 is formed by development, as shown in FIG. 1D, etching is performed by spraying an etching solution on the surface of the inner insulating substrate 1. , The exposed copper foil is removed and the inner layer circuit 7 is removed.
To form Thereafter, as shown in FIG. 1 (E), the etching resist layer 6 is peeled off by spraying a peeling solution on the etched inner layer insulating substrate 1. Thereafter, the surface of the inner circuit 7 is roughened to complete the formation of the inner circuit board 8.

Next, as a laminating step, first, in order to reduce the level difference between the inner layer circuit 7 and the inner layer insulating substrate 1 shown in FIG.
An undercoat resin layer is formed. This consists of the steps described below. That is, the photocurable resin ink 9 is applied to the entire surface of the inner circuit board 8 as shown in FIG. What is important here is that the photocurable resin ink 9 has a viscosity at room temperature of 10 to 10.
It is in the range of 10 ² poises. If it is less than 10 poise, the resin flows out during application of the resin ink, and it becomes impossible to control the resin film thickness. On the other hand, when the viscosity exceeds 10 ² poise, air escape during application of the photo-curable resin ink 9 becomes poor, causing voids in the insulating layer. In the present embodiment, the photocurable resin ink 9 is mainly composed of a novolak type brominated epoxy resin and a liquid bisphenol A type epoxy resin, imidazole as a curing agent, epoxy acrylate as a photocurable component, and a photoreaction start. An epoxy resin having diethylene glycol monoethyl ether as an agent and a diluent was used. The photocurable resin ink 9 was applied by a screen printing method. As a method of applying the photocurable resin ink 9, a curtain coating method and a roll coating method are also applicable. In the present embodiment, the thickness of the inner layer circuit 7 is 35 μm, and the set value of the coating thickness of the photocurable resin ink 9 on the inner layer circuit 7 is 20 μm.

Next, the photocurable resin ink 9 applied to the inner layer circuit board 8 is irradiated with ultraviolet rays 5 so that the undercoat layer 13
Is formed. Here, the difference from the conventional method is that the degree of curing of the photocurable resin ink 9 on the inner layer circuit 7 and the inner layer insulating substrate 1 is selectively changed, and this is a method of irradiating ultraviolet rays in two steps. Do with. That is, as shown in FIG. 2C, in the first-stage light irradiation, only the surface of the photo-curable resin ink 9 is cured to make the surface tack-free,
In particular, it aims at curing the photocurable resin 10 on the inner layer circuit. In this embodiment (inner circuit thickness 35 μm)
m, the light irradiation amount at a photocurable resin thickness set on the inner layer circuit of 20 μm) was 0.5 J / cm ^2, and ultraviolet curing was performed using an ultraviolet irradiator having a high-pressure mercury lamp. The next second stage of light irradiation aims to cure only the photocurable resin 11 on the inner insulating substrate, as shown in FIG. 2 (D). Therefore, in order to cure the photocurable resin 10 on the inner layer circuit and prevent the degree of curing from proceeding, ultraviolet curing was performed through the inner layer pattern positive film 12 which is the reverse of the negative film used when forming the inner layer circuit 7. Note that the second light irradiation amount in this embodiment is 1.0 J / cm ² ,
An ultraviolet irradiator having a high-pressure mercury lamp was used as in the case of the second time. Thus, the formation of the undercoat layer on both surfaces of the inner circuit board 8 in which the degree of curing of the photocurable resin ink 9 on the inner circuit 7 and the inner insulating substrate 1 is selectively changed is completed.

Next, as shown in FIG. 2E, the adhesive resin 14 with copper foil was roll-laminated on both sides of the inner circuit board 8 on which the formation of the undercoat layer 13 was completed, to form a laminate. Thereafter, the laminate is subjected to a heat treatment under normal pressure to obtain a multilayer shield substrate 15 shown in FIG.

The lamination of the adhesive resin 14 with copper foil is carried out via heat and pressure laminating rolls 16a and 16b. The heating of the rolls 16a and 16b such as heating and pressurizing reduces the viscosity of the adhesive resin layer, and the rolls 16a and 16b such as heating and pressurizing.
Along with the pressure of 16b, it is necessary to obtain copper foil smoothness. As shown in FIG. 4 (A), the adhesive resin 14 with a copper foil is formed by coating a long copper foil 17 with a thermosetting resin ink and drying a solvent component to form an adhesive resin layer having a uniform thickness. 18 are obtained. As another method, as shown in FIG. 4B, a thermosetting resin ink 18 is coated on a long release film 19 having a releasable property, and the solvent is dried to obtain a uniform thickness. It is also possible to form the adhesive resin layer 18 and then bond the adhesive resin layer to the long copper foil 17 to manufacture the same. Since the adhesive resin 14 with copper foil obtained in this way is long, it is used as a small roll that is easy to handle with a flow of several tens to several hundreds of meters. The adhesive resin layer 1 according to the present embodiment
The composition of No. 8 is mainly composed of bisphenol A type epoxy resin and bisphenol F type epoxy resin.
An epoxy resin composed of an organic solvent was used as a curing agent, a reaction accelerator, a filler, and a diluent for the thermosetting resin. What is important here is that the melt viscosity of the adhesive resin in the initial stage (80 to 120 ° C.) of the heat treatment, which is the next step of lamination, is in the range of 10 ⁴ to 10 ⁵ poise. 1
If less than 0 ⁴ poise, flow of the copper foil adhesive resin 14 in the heating process in the laminates and the next step becomes remarkable, the insulating resin interlayer thickness retention is difficult in the laminated body. In addition, it causes the surface copper foil wrinkles of the laminate. On the other hand, if it exceeds 10 ⁵ poise, the adhesion between the undercoat layer 13 and the adhesive resin 14 with copper foil deteriorates, thereby causing the laminate insulating layer to peel off. Next, an 18 μm thick copper foil 17 was used, and a long adhesive resin 14 with a copper foil having a thickness of the adhesive resin layer 18 of 50 μm was used. The laminating conditions of the present embodiment are as follows.
After setting to 00 ° C., the feed rate of the inner layer circuit board 8 is 0.5
The adhesive resin 14 with a copper foil was adhered at a roll pressure of 6.0 kg / cm at m / min. In the heat treatment after the lamination, the multilayer shield substrate 15 was obtained by heating in a baking furnace set at 150 ° C. for 45 minutes. At this time, the melt viscosity of the adhesive resin at 120 ° C. was 2 × 10 ⁴ poise. In FIG. 3, the finish of the surface copper foil 17 of the multilayer shield substrate 15 is such that the step between the inner layer circuit 7 and the inner layer insulating substrate 1 is at most 2 μm. The thickness L of the insulating layer between the insulating layer and the outermost copper foil 17 was kept at least 50 μm, there was no void, and there was no problem.

After the above-described laminating step is completed, FIG.
As shown in (1), a through hole 20 is formed in the multilayer shield substrate 15 by drilling. Next, as shown in FIG. 5B, electroless copper plating and electrolytic copper plating are applied to form the through holes 21.
5C, the outermost layer circuit 22 of the outermost layer is formed by etching in FIG.
Get. In the present embodiment, a drill having a diameter in the range of 0.3 to 3.0 mm was used for drilling, but the drilling quality was good without any breakage of the drill and no excessive burr. Further, as a result of laminating a photosensitive resin film on the surface of the multilayer shield substrate 15 after copper plating, exposing through a mask film, and observing the substrate surface after development, there is no floating of the etching resist and the etching can be performed. No etching liquid seepage, circuit width 7 as design value
It was confirmed that a circuit having 5 μm and a circuit gap of 75 μm was also formed with high accuracy.

[0023]

As described above, according to the present invention,
In a method of manufacturing a multilayer shield substrate by roll laminating an adhesive resin with a copper foil on an inner layer circuit board ,
Photo-curing on the surface of the inner insulating substrate with the wiring pattern
Apply a curable resin ink and apply it over the entire surface of the photocurable resin ink.
The undercoat layer is formed by the first exposure to irradiate ultraviolet rays.
After formation, remove the undercoat layer on the wiring pattern.
UV light stronger than the first exposure is applied to the surface of the dark coat layer.
By performing the second exposure to irradiate, the degree of curing of the undercoat layer is selectively changed on the inner layer circuit and the inner layer insulating substrate, and the multilayer printed wiring is excellent in the smoothness of the copper foil surface and the adhesion of the insulating layer. Plates can be manufactured.

[Brief description of the drawings]

FIGS. 1A to 1E are cross-sectional views illustrating a method of manufacturing a multilayer printed wiring board according to an embodiment of the present invention in the order of steps.

FIGS. 2A to 2E are cross-sectional views illustrating a method of manufacturing a multilayer printed wiring board according to one embodiment of the present invention in the order of steps.

FIG. 3 is a sectional view illustrating a method of manufacturing a multilayer printed wiring board according to an embodiment of the present invention in the order of steps for explaining the method.

FIGS. 4A and 4B are cross-sectional views illustrating a method of manufacturing a multilayer printed wiring board according to an embodiment of the present invention in the order of steps.

FIGS. 5A to 5C are cross-sectional views shown in the order of steps illustrating a method for manufacturing a multilayer printed wiring board according to an embodiment of the present invention.

6 (A) and 6 (B) are cross-sectional views shown in the order of steps for explaining an example of a conventional method for manufacturing a multilayer printed wiring board.

FIGS. 7A to 7C are cross-sectional views shown in the order of steps for explaining another example of the conventional method for manufacturing a multilayer printed wiring board.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 inner layer insulating substrate 2 inner layer copper foil 3 photosensitive resin sheet 4 inner layer pattern negative film 5 ultraviolet ray 6 etching resist layer 7 inner layer circuit 8 inner layer circuit board 9 photocurable resin ink 10 photocurable resin on inner layer circuit 11 inner layer insulating substrate Upper photocurable resin 12 Inner layer pattern positive film 13 Undercoat layer 14 Adhesive resin with copper foil 15 Multilayer shield substrate 16 Laminating roll 17 Copper foil 18 Adhesive resin layer 19 Release film 20 Through hole 21 Through hole 22 Outer layer circuit 23 Multilayer Printed wiring board

Claims (1)

(57) [Claims] 1. A method for manufacturing a multilayer printed wiring board comprising the following steps (A) to (E). (A) A step of forming a wiring pattern composed of a conductor layer on the surface of an insulating substrate to form an inner insulating substrate. (B) the inner layer insulating the photocurable resin ink is applied to the surface of the substrate, after the formation of a more undercoat layer to the first exposure for irradiating ultraviolet rays to the photocurable resin ink entire surface, the distribution
The underlayer excluding the undercoat layer on a line pattern;
UV light having a higher intensity than the first exposure on the surface of the coat layer
And smoothing the surface of the inner circuit board by the second exposure . (C) An adhesive resin with a copper foil obtained by coating a long copper foil with a resin composition containing a thermosetting resin as a main component is applied to the inner-layer insulating substrate on which the undercoat layer has been formed under normal pressure. A step of continuously performing roll lamination to form a laminate. (D) a step of forming a multilayer shield substrate by heating the laminate to tightly and integrally cure the undercoat layer resin and the adhesive resin with copper foil; (E) A step of forming an outermost layer circuit after drilling and copper plating in the multilayer shield substrate.