JPH0541576A - Manufacture of printed circuit board - Google Patents

Abstract

PURPOSE:To prevent expansion of a board due to absorption of moisture and to accurately form a fine pattern at a desired position to manufacture an additive printed circuit board. CONSTITUTION:After a board is annealed, an electrolessly plating adhesive layer is formed, dried, cured, roughed, supplied with nuclei, electrolessly plated to form a conductor circuit, and an additive circuit board is manufactured.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a printed wiring board in which a conductor circuit is formed of metal on an insulating substrate.

[0002]

2. Description of the Related Art As one of methods for forming a printed wiring board of this type, an additive method has been conventionally proposed. According to this forming method, an adhesive layer is formed by applying an adhesive for electroless plating on a glass epoxy insulating substrate, and after roughening the surface of the adhesive layer, a plating resist is added as necessary. Along with the formation, a metal to be a conductor circuit is attached by electroless plating. According to this method, since the conductor circuit is basically formed by electroless plating, there is an advantage that a fine pattern can be easily and reliably formed by a small number of manufacturing steps.

[0003]

SUMMARY OF THE INVENTION In the above method,
Before forming the adhesive layer, it is desirable to polish the insulating substrate and then wash it with water to remove polishing debris.

However, when a printed wiring board is manufactured by applying an adhesive agent onto a substrate that is not sufficiently dried and heat-curing the adhesive agent, the adhesive strength (peel strength) between the conductor circuit and the adhesive layer is low, and It was found that the circuit could not be formed at the designed position.

As a result of diligent research, the inventors of the present invention have found that in the former case, the cause is a diameter of several tens of μm formed in the adhesive layer.
It was found that the bubbles were m, and the latter was swelling of the substrate. As a result of further research, it has been found that bubbles in the adhesive layer having a diameter of several tens of μm and swelling of the substrate are caused by water in the substrate. The air bubbles generated in the adhesive layer and the swelling of the substrate will be described below.

When an adhesive is applied to a substrate that is not sufficiently dried and is cured by heating, the residual moisture in the substrate becomes steam due to heat, and many bubbles with a diameter of several tens of μm are formed in the adhesive layer. Will end up. When such large air bubbles are mixed in the adhesive layer, the original insulating property of the substrate cannot be exhibited. In addition, when a heating test is performed, the bubbles thermally expand, and the expansion causes a change in the dimensions of the substrate. Further, even when an anchor is formed on the surface of the adhesive layer, the presence of a large number of bubbles makes it easier for the anchor recesses on the substrate surface to communicate with the bubbles. Then, the anchor effect is lowered and the strength is lowered, and even if a conductor circuit is formed on such an insulating substrate, peeling occurs in the conductor circuit.

Further, since the substrate is made of resin, there is a problem that the substrate absorbs water and the resin swells to change the dimensions of the substrate. If the dimensional change of the substrate is large, it is impossible to surely form a high-density conductor circuit peculiar to the additive method or a fine pattern such as a small-diameter through hole or via hole at a predetermined position. Therefore, even if an attempt is made to manufacture a multilayer printed wiring board using such an insulating substrate, it is impossible to achieve high density and high reliability.

The present invention has been made in view of the above problems, and an object of the present invention is to improve the insulating property of the substrate and the adhesion strength of the conductor circuit by removing the residual moisture of the insulating substrate, and It is an object of the present invention to provide a method for manufacturing a printed wiring board that can form an accurate fine pattern on a substrate.

[0009]

In order to solve the above problems, the present invention cleans the surface of an insulating substrate (a).
Step, forming an adhesive layer for electroless plating on the insulating substrate obtained in the step (a), and roughening the surface of the adhesive layer (b) step, and the step (b) And (c) step of forming a catalyst nucleus layer on the adhesive layer surface obtained by the above, (c)
In a method for producing a printed wiring board, which comprises a step (d) of forming a conductor circuit by electroless plating on the surface of the catalyst core layer obtained in the step, at least any one of the steps (b) to (d) It is characterized in that an annealing treatment is carried out before two steps. In the step (d), a method (full additive method) of forming a plating resist at a predetermined position and forming a conductor circuit at a position where the plating resist is not formed by electroless plating is preferable.

Even if the insulating substrate is washed with water after the steps (a), (b) and (c), the insulating substrate is dried by the annealing treatment to remove the residual moisture on the substrate. Therefore, the insulating substrate can be maintained at a constant size through a series of steps, and by designing the pattern formation position and the formation positions of through holes and via holes based on the annealing, the fine pattern can be accurately formed on the insulation substrate. And it becomes possible to form reliably. Further, according to this method, since the insulating substrate is not warped or the dimensions are not changed later, peeling of the conductor circuit or the like can be prevented.

It is desirable that the annealing process be performed before the step (b). The reason is that by sufficiently removing the residual water content on the insulating substrate before applying the adhesive, it is possible to reliably prevent large bubbles generated in large numbers in the adhesive layer. Therefore, it is possible to avoid various problems relating to the generation of bubbles in the adhesive layer, such as deterioration of the insulating property of the substrate, dimensional change of the substrate, and peeling of the conductor circuit due to the reduction of the anchor effect.

The annealing process is performed at 50 ° C. to 1 ° C.
It is desirable to carry out at 50 ° C. for 0.5 to 3.0 hours. In this case, a blower dryer that blows high-temperature air onto the substrate to evaporate the moisture, a far-infrared dryer that evaporates the residual moisture in the substrate by irradiation with far-infrared rays, or the like is used.
If the processing temperature is lower than 50 ° C., the temperature is too low to sufficiently evaporate the moisture in the insulating substrate, and the moisture remains in the substrate. If the processing temperature exceeds 150 ° C., for example, when the substrate is made of resin, the color changes due to heat,
There is a risk of deformation. Further, if the treatment time is less than 0.5 hours, the moisture in the insulating substrate is not sufficiently removed, and bubbles tend to be generated due to the residual moisture in the substrate. If the treatment time exceeds 3.0 hours, the production efficiency is deteriorated. During the annealing process of the substrate, the substrate is held horizontally on a mounting table or the like, which prevents the substrate from being deformed or warped.

The method for manufacturing the above-mentioned printed wiring board will be described in more detail below according to the manufacturing steps. As the insulating substrate, it is preferable to use, for example, a glass epoxy resin substrate, a glass epoxy resin substrate containing an ultraviolet shielding material, a glass polyimide resin substrate, or the like. Washing with water is the most preferable method for washing the substrate in the step (a). In the step (a), it is advantageous to roughen the substrate before cleaning, and as a method of roughening the surface of the insulating substrate, for example, sandblasting for polishing by spraying abrasive grains, Buffing or the like in which polishing is performed by a rotary buff having abrasive grains held on the surface is suitable. Even conventional polishing methods other than these can be sufficiently applied as long as a desired rough surface can be formed on the insulating substrate.

Next, the composition of the adhesive applied on the insulating substrate in order to improve the adhesiveness between the insulating substrate and the metallic conductor circuit will be described in detail. The adhesive for forming the adhesive layer in the step (b) includes a heat-resistant resin fine particle (filler resin) that is soluble in an acid or an oxidant and is pre-cured, and an acid or A heat-resistant resin liquid (matrix resin) that is hardly soluble in an oxidant, wherein the fine particles are dispersed in the resin liquid and the resin liquid is cured by a curing treatment. desirable. Also,
The matrix resin may be a photosensitive resin.

Examples of the heat-resistant resin fine particles include
Agglomerated particles obtained by condensing heat-resistant resin powder having an average particle size of 2 μm or less to have an average particle size of 2 μm to 10 μm, heat-resistant resin powder having an average particle size of 2 μm to 10 μm, and an average particle size of 2
At least one of a heat-resistant resin powder having an average particle size of 2 μm or less or an inorganic fine powder is attached to the surface of a particle mixture with a heat-resistant resin powder having an average particle size of 2 μm to 10 μm It is desirable to be selected from the pseudo particles thus formed.

Particularly, it is preferable to use the above-mentioned particle mixture as the heat-resistant resin fine particles, and the anchor formed of this resin can secure a more reliable anchor effect. Therefore, sufficient peeling strength can be imparted to the conductor circuit and the like formed thereon.

The curing of the adhesive is carried out, for example, by heat treatment or addition of a catalyst. By this treatment, the adhesive layer is in a state in which the matrix resin that is hardly soluble in the oxidizing agent or the like has the filler resin soluble in the oxidizing agent or the like dispersed therein. In this state, if oxidation treatment is performed with, for example, chromic acid, chromate salts, permanganate salts, ozone, etc., only the filler resin portion is selectively dissolved, and the matrix resin surface has numerous fine pores as anchors. It is formed. As a result, the surface of the adhesive layer is roughened.
If a plating resist or a conductor circuit is formed on the surface of the adhesive layer having the fine pores, a so-called anchor effect is obtained, and this effect makes it difficult for the plating resist and the conductor circuit to be separated from the adhesive layer.

As the heat-resistant resin fine particles to be the filler resin, for example, it is preferable to use powder of epoxy resin, polyester resin, bismaleimide-triazine resin or the like, and the size of such resin fine particles. Is 0.1μ as the range in which the desired anchor effect is obtained.
It is preferably about m to 10 μm. Epoxy resin, epoxy-modified polyimide resin, polyimide resin, phenol resin and the like can be used as the heat-resistant resin to be the matrix resin, and these resins may be given photosensitivity. By mixing a predetermined amount of the above resin fine particles with this resin liquid and then adding a solvent such as butyl cellosolve and stirring, a varnish of an adhesive in which the resin fine particles are uniformly dispersed can be obtained.

Various methods such as a roll coater, a dip coating method, a spray coating method, a spinner coating method, a curtain coating method and a screen printing method can be used to apply the adhesive varnish on the surface of the insulating substrate. Can be used. The adhesive varnish is applied to a thickness of about 10 μm to 100 μm by any of these methods.

After the adhesive varnish is applied, cured and roughened, catalyst nuclei such as palladium-tin colloid are applied to the rough surface of the adhesive layer in step (c). By this treatment, the rough surface of the adhesive is activated, and the metal can be easily deposited when electroless plating is performed.
Then, in the step (d), a plating resist for electroless plating is laminated corresponding to the non-formed portion of the conductor circuit in order to form a desired conductor circuit pattern on the surface subjected to the above treatment. .. As the plating resist, for example, a photosensitive dry film or the like is suitable.
With such a dry film, it is possible to reliably and highly accurately form a fine conductor circuit on the adhesive layer. Therefore, it is possible to sufficiently meet the demand for higher density and higher integration.

Then, the plating resist laminated on the surface of the adhesive layer is exposed to light and then developed to mask only the portion where the conductor circuit is not formed. In this state, electroless copper plating, electroless nickel plating, electroless tin plating, electroless gold plating, electroless silver plating, etc. are performed to deposit metal on the conductor circuit forming portion of the adhesive layer surface to which the catalyst nucleus has been added. .. After the electroless plating is performed, the plating resist is removed to obtain a desired conductor circuit pattern.

The above-mentioned manufacturing method is a method for manufacturing a single-layer printed wiring board by the so-called additive method. By repeating this method several times, each layer is electrically connected by a through hole or a via hole. A multilayer printed wiring board can be manufactured. Further, in the multilayer printed wiring board obtained by the above method of subjecting the board to the annealing treatment, the problem of dimensional change in the board is solved, and therefore a more complicated conductor circuit or a fine pattern such as a small diameter through hole or via hole is provided. It is possible to surely form at the position. Therefore, it is possible to manufacture a multilayer printed wiring board having higher density and higher reliability than conventional ones.

[0023]

EXAMPLES AND COMPARATIVE EXAMPLES Examples 1, 2 and 3 embodying the present invention and comparative examples to these examples will be described in detail below with reference to the drawings. [Example 1] In Example 1, a single-layer printed wiring board is manufactured by the additive method. The manufacturing steps (1) to (5) will be described below with reference to FIGS.

Step (1): In Example 1, as the insulating substrate 1, an FR-4 grade insulating substrate LE-67N, W type (manufactured by Hitachi Chemical Co., Ltd.) was used. High precision jet scrub polishing machine IJS-60 manufactured by Ishikawa Inscription for this substrate 1.
The surface of the substrate 1 is polished with 0 to obtain a surface roughness of 7 μm.
Rough surface 2 was obtained.

Next, the substrate 1 was washed under running water to remove polishing debris. Then, after holding the substrate 1 in a horizontal state, a hot air dryer D ₁ (manufactured by Tabai Spec, IPH-2
00M), and annealed at 50 ° C. for 1 hour (see FIG. 1 (a)).

Step (2): 60 parts by weight of phenol novolac type epoxy resin (Okaka Shell, trade name, E-154), 40 parts by weight of bisphenol A epoxy resin (Okaka Shell, trade name, E-1001) Part, imidazole curing agent (manufactured by Shikoku Kasei, trade name, 2P4MHZ) 4 parts by weight, epoxy resin fine powder (made by Toray) having a particle size of 5.5 μm 10 parts by weight, and epoxy resin fine powder (made by Toray) particle size 0 25 parts by weight of 0.5 μm were mixed and kneaded with a three-roller, and butyl cellosolve acetate was added in an appropriate amount to prepare an adhesive varnish.

Step (3): A varnish of the above adhesive is applied on the insulating substrate 1 using a roll coater, and then 1
It was dried and cured at 00 ° C. for 1 hour and 150 ° C. for 5 hours to form an adhesive layer 3 having a thickness of 50 μm (see FIG. 1 (b)).

Step (4): Next, the epoxy resin fine powder is dissolved and removed by immersion in chromic acid for 10 minutes,
The surface of the adhesive layer 3 was made a rough surface 4 (see FIG. 1 (c)). Then, after the neutralization, it was washed with water to remove chromic acid.

Step (5): The rough surface 4 is activated by immersing it in a commercially available palladium-tin colloid catalyst, and the catalyst core layer 5 is formed.
Formed. Then, after heat treatment at 120 ° C. for 30 minutes, dry film photoresist is laminated and
Exposure and development were performed to form the plating resist layer 6 (see FIG. 1).
(See (d)). And electroless copper plating solution (CuSO ₄ ·
5H ₂ O: 111.8 g / 10 liters, EDTA ・ 2N
a: 388.2 g / 10 liter, NaOH: 111.8
g / 10 liters, HCHO: 35.3 g / 10 liters,
The conductor circuit 7 having a thickness of about 35 μm was formed by immersion in an additive (appropriate) for 15 hours (see FIG. 1 (e)). Then, after removing the plating resist layer 6, the substrate 1 is dipped in a mixed solution of tartaric acid and hydrochloric acid (tartaric acid 5 to 100 g / liter, 35% hydrochloric acid 200 to 350 ml / liter),
The printed wiring board was manufactured by removing the catalyst in the conductor forming portion (see FIG. 1 (f)). [Embodiment 2] Next, regarding the manufacturing steps (1) to (5) of the multilayer printed wiring board of Embodiment 2 by the build-up method,
A description will be given based on FIGS. 2A to 2F.

Step (1): In Example 2, the insulating substrate 11 used in Example 1 was used. The substrate 11 was surface-polished by using an oscillation grinder IOP-600 manufactured by Ishikawa Inscription, and a rough surface 12 having a surface roughness of 2 μm was obtained.

Next, the substrate 11 was washed under running water. Then, after holding the substrate 11 in a horizontal state, using a blower dryer (manufactured by Tokyo Kakoki Co., Ltd.), 80 ° C., 3
A time annealing process was performed.

Then, the steps (2)-
According to (5) (however, roughening is H₂SO _FourLine using
It was. ) The additive method is applied to the substrate 11 to form an insulating substrate.
11, adhesive layer 13, rough surfaces 12 and 14, catalyst core layer 15 and
The wiring board 10 including the inner layer circuit 16 and the inner layer circuit 16 is formed (see FIG. 2).
(See (a)).

Step (2): 60 parts by weight of 50% acrylate of cresol novolac type epoxy resin (made by Yuka Shell, trade name, Epicoat 180S), bisphenol A type epoxy resin (made by Yuka Shell, trade name, E -1001) 40 parts by weight, diallyl terephthalate 15 parts by weight, 2-methyl-1- [4- (methylthio) phenyl] -2-morpholinopropanone-1 (manufactured by Ciba Geigy, Irgacure 907) 4 parts by weight, Imidazole (manufactured by Shikoku Kasei, trade name, 2P4MHZ) 4 parts by weight, epoxy resin fine powder (manufactured by Toray, particle size 0.5 μm) 50 parts by weight are mixed, and butyl cellosolve is added while stirring with a homodisper stirrer to bond. The varnish of the agent was created.

Step (3): The above-mentioned adhesive varnish is applied to the inner layer circuit 16 using a roll coater, and the temperature is 100 ° C.
Then, it was dried and cured for 1 hour to form a photosensitive adhesive layer 17 having a thickness of 50 μm (see FIG. 2 (b)).

Step (4): Next, a photomask film having a black circle with a diameter of 100 μm and a punched-out cut portion printed in black is brought into close contact with the wiring board 10 subjected to the treatment of the step (3), and the ultrahigh pressure mercury lamp is used. Exposure at 500 mj / cm ² . This was subjected to ultrasonic development treatment with a chlorocene solution to form an opening 18 having a diameter of 100 μm and serving as a via hole on the wiring board 10 (see FIG. 2 (c)).

Next, the wiring board 10 is exposed by an ultra-high pressure mercury lamp at about 3000 mj / cm ² and further heat-treated at 100 ° C. for 1 hour and then at 150 ° C. for 3 hours to obtain dimensional accuracy equivalent to a photomask film. Excellent opening 1
The interlayer insulating layer 21 having No. 8 was formed.

Then, the surface of the interlayer insulating layer 21 was changed to the rough surface 19 by immersing it in chromic acid for 10 minutes, and after neutralization, it was washed with water to remove chromic acid (see FIG. 2 (d)). Step (5): The catalyst core layer 22 is formed by immersing it in a commercially available palladium-tin colloidal catalyst, and then 120 in a nitrogen atmosphere.
Heat treatment was performed at 30 ° C. for 30 minutes. Then, after the dry film photoresist 20 was laminated, exposure and development were performed (see FIG. 2 (e)). Then, after dipping in an electroless copper plating solution having the same composition as in Example 1 for 15 hours to form a copper plating layer having a thickness of about 35 μm as the outer layer circuit 23 (see FIG. 2 (f)), the plating resist was removed and the via hole was removed. A multilayer printed wiring board with holes was manufactured. [Embodiment 3] Embodiment 3 is a build-up type multilayer printed wiring board in which a polishing method different from those of Embodiments 1 and 2 is adopted, and a manufacturing method thereof will be described with reference to FIGS.
A description will be given based on (d).

Process: In Example 3, the copper layer 3 was formed on the substrate 31.
FR-4 grade copper clad laminate MCL-
E-67 (manufactured by Hitachi Chemical Co., Ltd.) was used (see FIG. 3 (a)). Then, the copper layer 32 was subjected to an etching treatment by a conventional method to form an inner layer circuit 33 (see FIG. 3 (b)).

After that, the surface of the substrate 31 is changed to a rough surface 34 having a surface roughness of 5 μm by using the high precision jet scrubbing machine and by the same method as the step (1) of the first embodiment. (See Fig. 3 (c)). And the inner layer circuit 3
In order to change the surface of No. 3 into the rough surface 35, a so-called blackening reduction treatment was performed in which the surface of the inner layer circuit 33 was oxidized and then the surface was reduced again (see FIG. 3 (d)). The surface roughness of the inner layer circuit 33 was 3 μm (1 μm to 5 μm is a preferable range).

Next, the substrate 31 is washed with water, then held horizontally, and dried by a far infrared dryer D _{2 at} 120 ° C. and 30 ° C.
A minute annealing process was performed. Then, according to steps (2) to (5) of Example 2, a multilayer printed wiring board provided with via holes was manufactured by a build-up method. [Comparative Example] In a comparative example with respect to Examples 1 to 3, first, the same substrate as that used in Example 1 was subjected to jet scrub polishing and water washing. After that, the step (2) of Example 1 was performed without performing the annealing treatment.
A single-layer printed wiring board was manufactured by the same method according to the procedure of step (5).

Example 1 manufactured by the above method
In order to compare and evaluate the characteristics of the adhesive layer in each of the printed wiring boards of Nos. 2 and 3 and the comparative example, from the design state of the bubble generation state in the adhesive layer, the flatness of the adhesive layer, and the plating resist forming position. We investigated the gap.

As shown in Table 1, as a result of investigating the generation of bubbles in the adhesive layer, no bubbles having an inner diameter of 5 μm or more were generated in the adhesive layer in any of Examples 1, 2 and 3. It was On the other hand, in the comparative example, the inner diameter is 5 μ in the adhesive layer.
It was observed that many bubbles of m or more were generated. Further, as a result of investigating the flatness of the adhesive layer, in each of Examples 1, 2 and 3, the adhesive layer was excellent in smoothness as shown in Table 1, while the adhesive of Comparative Example was used. The layer smoothness was inferior to any of the examples. Further, in the printed wiring boards of the respective examples, no particular peeling was observed in the conductor circuit. On the other hand, in the comparative example, peeling was often seen in the conductor circuit, and mounting failure was apt to occur when electronic components or the like were placed on the wiring board. In addition, the displacement of the formation position of the plating resist was smaller and better in Examples 1 to 3 than in the comparative example.

[0043]

[Table 1]

In the table, ◯ indicates that the flatness of the adhesive layer is less than plus or minus 5 μm, and x indicates that the flatness of the adhesive layer is plus or minus 5 μm or more. Also, regarding the peel strength in the table, JIS-C-6
The measurement was performed according to 481.

[0045]

As described in detail above, according to the method for manufacturing a printed wiring board of the present invention, the residual moisture of the insulating substrate is surely removed, so that the insulating property of the substrate and the adhesion strength of the conductor circuit are improved. In addition, it has an excellent effect that the expansion of the resin can be suppressed and an accurate fine pattern can be formed on the substrate.

[Brief description of drawings]

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

2 (a) to 2 (f) are schematic views showing a manufacturing process of the printed wiring board of Example 2. FIG.

3 (a) to 3 (d) are schematic views showing a manufacturing process of the printed wiring board of Example 3. FIG.

[Explanation of symbols]

1 insulating substrate, 3 adhesive layer, 5 catalyst core layer, 7 conductor circuit.

Claims (3)

[Claims] 1. A step (a) of cleaning a surface of an insulating substrate (1), and an adhesive layer (3) for electroless plating formed on the insulating substrate (1) obtained in the step (a). In addition, the surface of the adhesive layer (3) is roughened (b), and the catalyst core layer (5) is formed on the surface of the adhesive layer (3) obtained in the step (b) (c). In the method for producing a printed wiring board, which comprises a step and a step (d) of forming a conductor circuit (7) on the surface of the catalyst core layer (5) obtained in the step (c) by electroless plating, A method for manufacturing a printed wiring board, which comprises performing an annealing treatment before at least any one of the steps b) to (d). 2. The method of manufacturing a printed wiring board according to claim 1, wherein the annealing treatment is performed before the step (b). 3. The annealing treatment is performed at 50 ° C. to 150 ° C.
The method for producing a printed wiring board according to claim 1 or 2, which is performed at 0.5 ° C for 0.5 hours to 3.0 hours.