JP2937951B2 - Method for manufacturing multilayer printed wiring board - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for manufacturing a multilayer printed circuit board, and more particularly to a method for manufacturing a multilayer printed wiring board having an outer layer formed by roll lamination.

[0002]

2. Description of the Related Art A conventional method for manufacturing a multilayer printed wiring board will be described by taking a multilayer printed wiring board having four layers as an example. First, the inner layer circuit board on which the circuit is formed is blackened, and a copper foil is thermocompressed to the inner layer circuit board via a semi-cured adhesive sheet called a prepreg by a lamination press to obtain a copper-clad laminate with an inner layer circuit (hereinafter, referred to as a “clad laminate”). ,
(Referred to as a multilayer shield substrate)). In the process of thermocompression bonding of copper foil, complicated work is necessary to combine the inner layer circuit board, prepreg, copper foil, release film, etc.
In addition, there is a problem that the thermocompression bonding time is long.

[0003] As a method of manufacturing a multilayer printed wiring board which solves these problems, Japanese Patent Application Laid-Open Nos. 7-336054, 7-307576, and 7-24548.
No. 5 discloses a method of thermocompression bonding an adhesive sheet by roll lamination (hereinafter, these methods are referred to as a first method). FIG. 5 is a view showing one example of a method of manufacturing a multilayer shield substrate in the order of steps. First,
As shown in FIG. 5A, the surface of the inner layer circuit 1 of the inner layer circuit board 3 on which the circuit is formed is roughened by a blackening process in order to improve the resin adhesion. Next, the ultraviolet curable resin 4a is applied to one surface of the inner circuit board 3, and is dried by touch in an ultraviolet curing furnace (FIG. 5B). Similarly, the inner-layer circuit board 3
FIG. 5 (C) shows a state where the ultraviolet curable resin 4a is applied to the other side and dried. Next, an adhesive resin 5a for additive plating and a copper foil 6, or a copper foil 6 with an adhesive resin 5a, etc., are thermocompression-bonded to both surfaces of the inner layer circuit board 3 by roll lamination, and a four-layer laminate (FIG. D))
Then, the multilayer body is subjected to a heat treatment to obtain a multilayer shield substrate 7 (FIG. 5E).

Another method is disclosed in Japanese Patent Laid-Open No. 5-678.
No. 81 discloses a method for manufacturing a multilayer shield substrate using a thermosetting resin instead of the ultraviolet-curable resin 4 in the first method (hereinafter, referred to as a second method). FIG. 6 is a view showing an example of a method of manufacturing a multilayer shield substrate in the order of steps. First, as shown in FIG. 6A, the inner layer circuit board 3 on which the copper foil circuit 1 is formed is subjected to blackening treatment, and the thermosetting resin 11 is applied to one side of the inner layer circuit board 3 as shown in FIG. And dried by touch in a baking oven. Similarly, FIG. 6C shows a state where the thermosetting resin 11 is applied to the other surface of the inner circuit board 3 and dried. An adhesive resin for additive plating and a copper foil, or a copper foil with an adhesive 5 or the like is thermally bonded to the inner layer circuit board 3 by roll lamination to form a four-layer laminate (FIG. 6D). Next, this laminate is subjected to a heat treatment to obtain a multilayer shield substrate 6 (FIG. 6E).

[0005]

The problem with the first method is that when the ultraviolet curable resin is finally cured, bubbles 12
(Laminate voids) occur in the multilayer shield substrate. The bubbles 12 cause peeling abnormalities due to thermal shock during mounting or the like, and when bubbles are present in the through-hole processing portion of the multilayer shield substrate in the drilling step, the plating solution is introduced into the multilayer shield substrate 6 through the bubbles. Soak,
It is known to cause an inner layer short-circuit abnormality of a multilayer printed wiring board.

As a cause of the generation of the bubbles in the first method, an ultraviolet curable resin is cured by irradiating ultraviolet rays, and then an adhesive resin or a copper foil with the adhesive resin is directly thermocompression-bonded to the inner circuit board. Therefore, it is considered that the moisture absorption in the ultraviolet curable resin evaporates and evaporates during the heat treatment of the multilayer shield substrate.

[0007] The resin surface of the inner layer circuit board has surface irregularities due to the profile of glass cloth or copper foil used for the board material, and the surface of the ultraviolet curable resin applied to this portion also has this surface. Irregularities are formed due to surface irregularities. The maximum variation (maximum roughness) on the roughness profile measured by the surface roughness meter is Rm.
ax, the surface roughness of the ultraviolet curable resin is 10 to
It is about 15 μm (Rmax).

When laminating a copper foil with an adhesive resin on the inner layer circuit board, air is held between the ultraviolet curable resin and the copper foil due to the unevenness at this level, and the air bubbles are formed, and multi-layer printing is performed similarly to the above-mentioned moisture absorption. This may cause an inner layer peeling abnormality or a short circuit abnormality of the wiring board. The problems with the second method are that the working time is increased due to touch drying of the thermosetting resin, and that the multilayer shield substrate and the multilayer printed wiring board of the final product due to the heating of the substrate have large warpage and dimensional behavior.

An object of the present invention is to provide a method for manufacturing a multilayer printed wiring board in which an outer layer which solves the above-mentioned problems of the prior art is formed by roll lamination.

[0010]

According to the present invention, there is provided a method for manufacturing a multilayer printed wiring board, comprising the steps of: etching a copper-clad laminate to form an inner circuit board having a desired inner circuit; Coated with a light / thermosetting resin,
Irradiating ultraviolet rays to the surface of the thermosetting resin, the purple
After the step of irradiating the outside line, the inner layer circuit board is heat-treated.
At the same time as removing water from the photo-thermosetting resin
A step of smoothing the surface of the photo-thermosetting resin, and after thermocompression bonding the copper foil with an adhesive resin containing a thermosetting resin as a main component to the inner layer circuit board with the adhesive resin surface as an adhesive surface. , Heating to form a multilayer shield substrate, and forming holes in the multilayer shield substrate, copper plating, and then forming an outermost layer circuit.

The step of heat-treating the inner-layer circuit board includes:
At the same time as removing the moisture-absorbed moisture of the photo-thermosetting resin after the ultraviolet irradiation curing, the surface of the photo-thermosetting resin is thermally melted and smoothed, thereby preventing air entrapment during lamination, and a multilayer shield substrate. Can be heated to prevent the formation of air bubbles in the substrate when it is finally cured.

A process for irradiating the photo-thermosetting resin with ultraviolet rays;
After that, the inner layer circuit board is heat-treated to
In the step of smoothing the surface of the cured resin, the heat treatment
The roughness Rmax of the surface of the photo-thermosetting resin is 5 μm.
By smoothing to less than m , a great effect can be obtained in the present invention.

As the photo-thermosetting resin, a resin containing an epoxy resin as a main component can be used.
The coating method on the inner layer circuit board can be a screen printing method, a curtain coating method or a roll coating method.

[0014]

Next, embodiments of the present invention will be described with reference to the drawings. 1 and 2 are drawings for explaining a method of manufacturing a multilayer printed wiring board according to a first embodiment of the present invention. FIGS. 1A to 1F are diagrams for forming an inner circuit board to a multilayer. FIG. 2A to FIG. 2C are cross-sectional views of a main part of a substrate in a process from forming a through hole to forming an outer layer circuit of a multilayer shield substrate. FIG.

In the first embodiment of the present invention, screen printing is used as a method for forming the photo-thermosetting resin on the inner circuit board.

First, as shown in FIG. 1A, a copper-clad laminate of an epoxy glass substrate is etched by a usual method.
An inner circuit board 3 having an inner circuit 2 is formed on a substrate 1. Irregularities are formed on the surface of the substrate 1 due to the effect of the profile of the glass cloth or copper foil of the substrate. Next, the surface of the inner circuit 2 is needle-like crystallized (roughened) by immersing the inner circuit board 3 in an aqueous cupric chloride solution. This process is performed to improve the adhesion between the inner layer circuit 2 of the inner layer circuit board 3 and the photo-thermosetting resin in the next step.

Next, a photo-thermosetting resin 4 containing an epoxy resin as a main component is applied to one surface of the inner circuit board 3 by a screen printing method, and dried by touch in an ultraviolet curing oven (FIG. 1).
(B)). At this time, screen printing conditions were as follows: screen mesh: 80 to 100 mesh, squeegee hardness: 70
Degree, coating speed: 0.05 to 0.1 m / sec. The photo-thermosetting resin 4 has a viscosity of 10 to 20 poise at 20 ° C., a heat melting start temperature of 80 to 100 ° C. when heated after ultraviolet curing, and a melt viscosity of 10,000 to 50,
It is important to use a resin that is 000 poise.
At the time of touch-drying of the photo-thermosetting resin 4, it is preferable to leave a standing time of 15 minutes or more after application of the resin in order to improve the smoothness of the resin surface and defoam the resin. The thickness of the photo-thermosetting resin 4 is set to about 20 μm on the inner circuit 2.

Next, ultraviolet irradiation is performed under the condition of a light amount of 1 to 3 J / cm ² , and touch drying is performed. Similarly, FIG. 1C shows a state in which the photo-thermosetting resin 4 is applied to the other surface of the inner-layer circuit board 3 and dried by touch. The surface roughness of the light / thermosetting resin 4 on the substrate 2 is 10 to 10 in a state immediately after coating.
It is about 15 μm (Rmax).

Next, the inner layer circuit board 3 coated with the photo-thermosetting resin 4 and dried by touch is heat-treated. The heating conditions in the heat treatment are important for ensuring the adhesion when the copper foil with the adhesive resin is thermocompression-bonded to the light / thermosetting resin 4. For this purpose, the degree of curing of the photo-thermosetting resin 4 in ultraviolet irradiation and subsequent heating is controlled so that the photo-thermosetting resin 4 is melted during thermocompression bonding. Table 1 shows appropriate heating conditions for the photo-thermosetting resin 4.

FIG. 1D shows the state of the substrate after the heat treatment. By the heat treatment, the photo-thermosetting resin 4 is thermally melted and its surface roughness is smoothed so that Rmax is less than 5 μm. In addition, it has been confirmed that this heat treatment removes the moisture-absorbing component in the photo-thermosetting resin 4. This allows
It has been confirmed that excessive resin curing at a level at which the adhesion reaction during lamination is inhibited can be prevented.

[0021]

[Table 1]

Next, after heat-pressing the copper foil 6 with the adhesive resin 5 on the inner layer circuit board 3 after the heat treatment by roll lamination, it is further heat-treated at a temperature of 140 to 160 ° C. for 30 to 60 minutes, and FIG. 4), the multilayer shield substrate 7 has four layers. In order to prevent moisture absorption, the inner layer circuit board 3 after the heat treatment has a temperature of 20 to 25 ° C. and a relative humidity of 50 to 60%.
It is preferable to perform thermocompression bonding of the copper foil 6 within 2 hours in the atmosphere described above. Further, in order to improve the adhesion of the copper foil 6, the surface temperature of the photo-thermosetting resin 4 on the inner circuit board 3 before the roll lamination is controlled to 50 to 70 ° C. by a method such as infrared rays or roll heating. The conditions for roll lamination are lamination roll temperature 100 to 12
The temperature was set at 0 ° C., the lamination pressure was 3 to 6 kg / cm ² , and the lamination speed was 0.5 to 2.0 m / min.

Next, a through hole 8 is formed in the multilayer shield substrate 7 (FIG. 2A), and a copper panel plating is performed to form a through hole 9 (FIG. 2B). Further, the outermost layer circuit 10 is formed by a normal etching method to obtain a target multilayer printed wiring board 11 (FIG. 2C).

Next, a second embodiment of the present invention will be described.
This will be described with reference to FIGS. In the first embodiment of the present invention, the photo-thermosetting resin is applied by the screen printing method, but in the present embodiment, the roll coating method is used.

First, an inner circuit board 3 having an inner circuit 2 is formed on a substrate 1 in the same manner as in the first embodiment.
Next, the surface of the inner circuit 2 is needle-like crystallized (roughened) by immersing the inner circuit board 3 in an aqueous cupric chloride solution (FIG. 3).
(A)).

Next, a photo-thermosetting resin 4 is simultaneously applied to both sides of the inner circuit board 3 by a roll coater, and this is touch-dried in a double-sided ultraviolet curing oven (FIG. 3B). By using a roll coater, the work time can be shortened by simultaneous application on both sides, and when it is a part of the compare line, it can be produced in a smaller space than screen printing, etc., making the production line area effective Can be achieved. light·
The thermosetting resin 4 needs to have the same properties as those used in screen printing.

However, the viscosity of the photo-thermosetting resin 4 is smaller than that of the photo-thermosetting resin of the first embodiment, and is adjusted to 1 to 10 poise at 20 ° C. Thereby, the depth of the roll slit is adjusted between 10 and 50 μm, and the resin thickness is about 20 μm on the inner layer circuit 2.
The resin thickness is controlled so as to be m. The standing time after application of the resin is set to 15 minutes or more for improving the resin surface smoothness and defoaming. For the next touch drying, as in Example 1,
Ultraviolet irradiation is performed under the conditions of a light amount of 1 to 3 J / cm ² . The surface shape of the undercoat was 1 in the same manner as in Example 1.
There are irregularities of about 0 to 15 μm.

Next, FIG. 3C shows a state in which the inner-layer circuit board 3 has been heat-treated under the heating conditions shown in Table 1. The surface of the photo-thermosetting resin is smoothed by the thermal melting at the time of heating, and the surface roughness Rmax of the resin is reduced to less than 5 μm. The heat treatment removes the moisture absorbing component of the photo-thermosetting resin 4. As for the adjustment of the degree of curing of the photo-thermosetting resin, the heating conditions in Table 1 can be applied as they are, as in the first embodiment. By adjusting the degree of resin curing, excessive curing of the resin can be prevented, and the adhesion of the copper foil during lamination is ensured.

Next, the copper foil 6 with the adhesive 5 is thermocompression-bonded to the inner circuit board 3 by roll lamination in the same manner as in the first embodiment.
Further heat treatment is performed for another minute to form a multilayer shield substrate 7 having four layers as shown in FIG. The conditions for roll lamination were the same as in the first embodiment. A through hole 8 is formed in the multilayer shield substrate 7 (FIG. 4A), and a copper panel plating is performed to form a through hole 9 (FIG. 4).
(B)). Further, the outermost layer circuit 10 is formed by etching to obtain a multilayer printed wiring board 11 (FIG. 4C).

As described above, by simultaneously applying the light / thermosetting resin on both sides using the roll coater, the working time can be further reduced, and the multilayer printed wiring which is equivalent in quality to the first embodiment can be obtained. Boards can be manufactured.

[0031]

The first effect of the present invention is that the moisture absorption of the photo-thermosetting resin is reduced by heating the inner circuit board 3 coated with the photo-thermosetting resin 4 and dried by touch. That is, it is possible to remove the laminated voids due to vaporization of moisture absorption.

The second effect of the present invention is that the inner layer circuit board is subjected to heat treatment to thermally melt and smooth the surface of the photo-thermosetting resin after curing by irradiation with ultraviolet rays, thereby reducing unevenness during lamination. This is to prevent bubbles from being entrained and prevent the occurrence of laminated voids due to entrainment of bubbles.

A third effect of the present invention is that the processing time is shorter and the working efficiency is improved as compared with the conventional method.

[Brief description of the drawings]

FIG. 1 is a diagram for explaining a method for manufacturing a multilayer printed wiring board according to a first embodiment of the present invention, and is a cross-sectional view of a main part of a substrate in a process from formation of an inner circuit board to formation of a multilayer shield substrate. It is.

FIG. 2 is a cross-sectional view of a main part of a substrate after the formation of the multilayer shield substrate of FIG. 1 in the method for manufacturing a multilayer printed wiring board according to the first embodiment of the present invention.

FIG. 3 is a diagram for explaining a method for manufacturing a multilayer printed wiring board according to a second embodiment of the present invention, and is a cross-sectional view of a main part of a substrate in steps from formation of an inner circuit board to formation of a multilayer shield substrate. It is.

FIG. 4 is a cross-sectional view of a main part of a substrate after a step of forming the multilayer shield substrate of FIG. 3 in the method for manufacturing a multilayer printed wiring board according to the second embodiment of the present invention.

FIG. 5 is a cross-sectional view of a main part of a substrate, for explaining a step of manufacturing a multilayer shield substrate according to a first conventional method.

FIG. 6 is a cross-sectional view of a main part of a substrate, for explaining a step of manufacturing a multilayer shield substrate according to a second conventional method.

[Explanation of symbols]

 Reference Signs List 1 base material 2 inner layer circuit 3 inner layer circuit board 4 light / thermosetting resin 4a ultraviolet curing resin 4b thermosetting resin 5 adhesive 6 copper foil 7 multilayer shield board 8 through hole 9 through hole 10 outermost layer circuit 11 multilayer printing Wiring board 12 Bubbles

Claims (3)

(57) [Claims] A step of etching a copper-clad laminate to form an inner layer circuit board having a desired inner layer circuit; and coating the surface of the inner layer circuit board with a light / thermosetting resin;
Irradiating ultraviolet rays to the surface of the thermosetting resin, the purple
After the step of irradiating the outside line, the inner layer circuit board is heat-treated.
At the same time as removing water from the photo-thermosetting resin
A step of smoothing the surface of the photo-thermosetting resin, and after thermocompression bonding the copper foil with an adhesive resin containing a thermosetting resin as a main component to the inner layer circuit board with the adhesive resin surface as an adhesive surface. And heating to form a multilayer shield substrate, and forming a hole in the multilayer shield substrate, copper plating, and then forming an outermost layer circuit. 2. The copper clad laminate is etched to form a desired inner layer.
Forming an inner circuit board having a circuit; and
The surface of the circuit board is coated with a light / thermosetting resin,
Irradiating the surface of the thermosetting resin with ultraviolet light;
After the step of irradiating the outside line, the inner layer circuit board is heat-treated.
And melt the light / thermosetting resin to smooth its surface.
And a thermosetting resin after the smoothing step.
Copper foil with an adhesive resin whose main component is the adhesive resin surface
A step of thermocompression bonding to the inner layer circuit board with an adhesive surface,
After the thermocompression bonding, heat the light and thermosetting resin and
Thermosetting the adhesive resin to form a multilayer shield substrate
Forming an outermost layer circuit on the multilayer shield substrate
And a process for producing a multilayer printed wiring board. 3. The method according to claim 1, wherein the heat treatment in the smoothing step is performed.
The surface roughness of the light / thermosetting resin is Rmax of 5 μm.
3. The method for manufacturing a multilayer printed wiring board according to claim 2 , wherein the surface is smoothed to less than m .