JPH1013022A - Method for manufacturing multilayer printed wiring board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a multilayer printed wiring board with improved fine patterning property, economy, and working efficiency. SOLUTION: In a method, an insulation layer is formed on the entire or one part of an insulation substrate surface where a conductor circuit is formed, for example, a via hole is formed as needed, an electroless plating is applied to the surface of the insulation layer, patterning is made, the conductor circuit is formed, and the above steps are repeated, thus manufacturing a multilayer printed wiring board. At this time, before electroless plating is made onto the insulation layer surface, the insulation layer is pre-treated by an alkali metal hydroxide solution of 0.1-10mol/l, is subjected to electroless plating, electrical copper plating as needed, and then heat treatment at 100-300 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in electrical insulation between circuits of a multilayer printed wiring board and an improvement in workability of an etching process on an insulating layer surface for achieving the same.

[0002]

2. Description of the Related Art As a recent multi-layered technology of a printed wiring board, an insulating layer is formed on the surface of the printed wiring board, and a via hole is formed in a part of the insulating layer by a photolithography technique or laser processing, and then the surface of the insulating layer is formed. A so-called build-up method has been developed in which an electroless plating is applied to a via hole portion, and then a method of forming a circuit using an additive method or a subtractive method is repeated as necessary. Also, this build-up method has attracted attention as a technique for inexpensively manufacturing a high-density multilayer printed wiring board.

[0003] Although it has a great effect on various characteristics of a multilayer printed wiring board obtained by this build-up method,
One is the adhesion between the insulating layer and the electroless plating film, and many proposals have been made to improve the adhesion. For example, as a typical example, an insulating layer is formed using a substance containing fine particles having solubility in an etching solution, and then the surface of the insulating layer is mechanically polished. There is a method of chemically etching the surface of the insulating layer using a strong oxidizing agent such as chromic acid to roughen the surface of the insulating layer, and then performing electroless plating.

[0004]

Although the multilayer printed wiring board manufactured by using the above-mentioned method has been partially put into practical use, a strong oxidizing agent harmful to the human body such as permanganic acid or chromic acid is used during etching. There is a drawback that the working environment is hindered because it is used as an etchant. Furthermore, when the circuit is formed by etching the electroless plating film after patterning, there is unevenness due to roughening on the surface of the insulating layer, so that the plating metal easily remains between the circuits, and when the circuit interval is small, In particular, a problem has been pointed out that insulation between circuits may be hindered.

The present invention solves the above-mentioned problems in the production of a multilayer printed wiring board by the above conventional method, and provides a method for producing a multilayer printed wiring board which is excellent in fine patterning property, economical and workable. It is intended to do so.

[0006]

The present inventors have made various studies to solve the above problems, and as a result, have found that the surface of an insulating layer formed by a chemical etching process performed as a pretreatment for electroless plating. It has been found that the protruding portions of the plating film applied to the inside of the irregularities easily cause plating metal residue when forming a circuit. Then, it has been found that by optimizing the degree of the irregularities on the surface of the insulating layer, it is possible to reduce the residual plating metal during circuit formation, thereby completing the present invention.

That is, according to the present invention for solving the above-mentioned problems, an insulating layer is formed on all or a part of an insulating substrate surface on which a conductive circuit is formed, and then a via hole or the like is formed if necessary. In the step of manufacturing a multilayer printed wiring board by repeating electroless plating and patterning to form a conductor circuit and repeating this, before applying the electroless plating to the surface of the insulating layer, the insulating layer 0.1. Pretreatment with an aqueous solution of an alkali metal hydroxide of 10 to 10 mol / l,
This is a method for producing a multilayer printed wiring board, characterized in that electroless plating is performed after electroless plating is performed, followed by electrolytic copper plating, and then heat treatment is performed at 100 to 300 ° C.

The insulating layer formed in the present invention is preferably an alkali-developing ultraviolet-sensitive resist. Further, if necessary, the formation of the insulating layer and the formation of the conductor circuit on the surface of the insulating layer are repeated at least once or more to form the multilayer printed wiring board.

[0009]

DETAILED DESCRIPTION OF THE INVENTION In the present invention, an aqueous solution of an alkali metal hydroxide is used as a pretreatment liquid for electroless plating on the surface of an insulating layer, instead of permanganic acid or chromic acid which has been conventionally used. In this pretreatment, the surface of the insulating layer swells and becomes hydrophilic. As a result, adsorption of the electroless plating catalyst such as palladium on the surface of the insulating layer becomes easy in the subsequent catalyst application treatment.

The pretreatment method of the present invention is not particularly limited as long as the surface of the insulating layer and the pretreatment liquid are in contact with each other, but, for example, a dipping method or a spraying method is recommended. In addition, pretreatment with an aqueous alkali metal hydroxide solution is not of the type that dissolves the insulating layer as strongly as conventional permanganic acid or chromic acid, so that excessive irregularities may be formed on the insulating layer surface. As a result, there is no problem such as residual plating metal during the formation of the electroless plating film. Further, there is no particular problem in the workability at the time of etching and the treatment of waste liquid.

In the present invention, the concentration of the aqueous alkali metal hydroxide solution used as the pretreatment liquid is 0.1 to 10 mol / mol.
A range of liters is appropriate. If the concentration is less than 0.1 mol / liter, sufficient effects cannot be obtained even if the pretreatment temperature, pretreatment time, and the like are increased, and problems such as non-precipitation of plated metal occur. On the other hand, when the concentration exceeds 10 mol / liter, the viscosity of the processing liquid becomes extremely high, so that it becomes difficult to uniformly perform the etching treatment even inside a fine via hole or the like formed in the insulating layer.
Again, problems such as non-precipitation of the plating film tend to occur. Further, depending on the material of the insulating layer, there is a risk that the insulating layer is partially peeled off by a high-concentration alkaline solution.

In the present invention, the pretreatment time and the pretreatment temperature cannot be unconditionally determined because an appropriate range differs depending on the above-mentioned solution concentration and the material constituting the insulating layer.
Therefore, it is necessary to determine in advance conditions such as appropriate temperature and time before actual operation. The alkali metal hydroxide used in the pretreatment liquid of the present invention is not particularly limited, but use of sodium hydroxide and potassium hydroxide is recommended from the viewpoint of economy. The insulating layer material used in the present invention preferably has a structure which is swollen and hydrophilized by an aqueous alkali metal hydroxide solution as described above, and a so-called alkali developing type ultraviolet-sensitive resist is suitable.

The pretreatment performed in the present invention does not cause excessive unevenness to be formed on the surface of the insulating layer as described above.
This is performed for the purpose of swelling and hydrophilizing the surface of the insulating layer. Therefore, the subsequent application of a catalyst for electroless plating and electroless plating can be carried out by conventional methods without any problem. However, the obtained plating film has an adhesion strength value of 0.8 kgf / cm or more, which is said to be a level that can be used practically. Can not be obtained. This is because in the pretreatment of the present invention, the so-called anchor effect obtained by the complicated penetration of the plating metal into the insulating layer as in the related art cannot be sufficiently obtained.

For this purpose, in the present invention, the electroless plating is performed by performing a heat treatment at a temperature of 100 to 300 ° C. after the electroless plating or, if necessary, the subsequent electrolytic copper plating. It enhances the adhesion of the film. If the heat treatment temperature is lower than 100 ° C., a sufficient effect cannot be obtained even if the heat treatment time is lengthened.
If the temperature exceeds 0 ° C., the insulating layer is undesirably deteriorated by high heat. Since the appropriate range of the heat treatment time varies depending on the heat treatment temperature, the material of the insulating layer, and the etching conditions, the proper time is taken into consideration in advance of the actual operation in consideration of the effect of improving the adhesion and the deterioration of the insulating layer due to heat. It is necessary to determine.

The electroless plating method performed in the present invention is not particularly limited, and a known method may be employed, and the effect of the present invention does not depend on the metal species of the plating film to be formed. Furthermore, a method of forming an insulating layer,
A well-known method may be adopted as a method of forming a via hole.

[0016]

Next, the present invention will be described in more detail with reference to Examples and Comparative Examples. Example 1: 400 mm long, 500 mm wide, 1.6 m thick
A double-sided printed wiring board having a circuit with a minimum pitch of 150 μm was obtained by patterning the copper film with a ferric chloride solution using a double-sided copper-clad glass epoxy substrate of m (copper thickness 18 μm). On the surface of the obtained printed wiring board, an alkali-developable photoresist “SL-2” made by Taiyo Ink
Is applied to a thickness of 50 μm, dried, and has a diameter of 10 μm.
A 0 μm via hole was formed at a predetermined position on the insulating layer using a photolithography technique, and a 400 μm diameter through hole was formed at a predetermined position on the substrate by drilling. Then, the insulating layer surface is buffed to a thickness of 10 μm.
m.

The substrate obtained by the above processing is heated at 40 ° C.
Was immersed in a 5 mol / liter aqueous sodium hydroxide solution for 5 minutes, and then washed with water. 25 ° C Okuno Pharmaceutical “0P
C-80 Catalyst ”solution for 5 minutes, rinse with water 2
"OPC-555 Accelerator" manufactured by Okuno Pharmaceutical Company at 5 ℃
It was immersed in the solution for 5 minutes and washed with water. After that, the substrate is made of
Hydrate 10 g / l, ethylenediaminetetraacetic acid 2
30 g / l of sodium, 5 g / l of a 35% formaldehyde solution and 10 g of 2,2'-bipyridyl
pH mg containing 0.5 g / l of polyethylene glycol having an average molecular weight of 1,000 mg / l.
5. Dipped in an electroless copper plating solution at 65 ° C. for 10 minutes to form an electroless copper plating film having a thickness of 0.3 μm.

The obtained substrate was left in a heating furnace maintained at 150 ° C. for 10 minutes to perform a heat treatment. Thereafter, an electrolytic copper plating solution containing 80 g / l of copper sulfate pentahydrate and 180 g / l of sulfuric acid was used on the electroless copper plating film at a cathode current density of 3 A / dm ² and at 23 ° C. for 3 hours.
Electroless copper plating was performed for 0 minutes. Further, after an etching resist is patterned on the electrolytic copper plating film at a circuit interval of a minimum pitch of 150 μm by a photolithography technique according to a conventional method, a ferric chloride solution of 40 Baume is used at a temperature of 50 ° C. and a shower pressure of 2.0 kg / cm. ² in 4
The circuit was formed by etching for 0 seconds.

Through the above steps, a four-layer printed wiring board having a circuit thickness of 18 μm, a minimum circuit pitch of 150 μm, a via hole diameter of 100 μm, and a through hole diameter of 400 μm was finally obtained. The adhesion strength of the circuit of the obtained printed wiring board to the substrate is 1.0 kgf /
cm, which was a value that could be put to practical use. Also, no problems such as disconnection of the circuit due to non-deposition of plating and poor conduction of via holes did not occur, no copper plating film remained between the circuits, and the electrical reliability was satisfactory. Was.

Example 2 A four-layer printed wiring board was manufactured in the same procedure as in Example 1 except that the heat treatment of the electroless copper plating film was performed by holding the substrate in a heating furnace maintained at 100 ° C. for one hour. I got The adhesion strength of the circuit to the substrate of the obtained printed wiring board is 0.8 kgf / cm,
This value was a value that could withstand practical use. Also, no problems such as disconnection of the circuit due to non-deposition of plating and poor conduction of via holes did not occur, no copper plating film remained between the circuits, and the electrical reliability was satisfactory. Was.

Example 3 Four-layer printed wiring board in the same procedure as in Example 1 except that the heat treatment of the electroless copper plating film was performed by holding the substrate in a heating furnace maintained at 300 ° C. for 3 minutes. I got The adhesion strength of the circuit of the obtained printed wiring board to the substrate is 1.0 kgf / cm,
This value was a value that could withstand practical use. Also, no problems such as disconnection of the circuit due to non-deposition of plating and poor conduction of via holes did not occur, no copper plating film remained between the circuits, and the electrical reliability was satisfactory. Was.

Example 4 A four-layer printed wiring board was obtained in the same procedure as in Example 1, except that an etching treatment was performed at 70 ° C. for 1 hour using a 0.1 mol / L aqueous solution of sodium hydroxide. . The adhesion strength of the circuit of the obtained printed wiring board to the substrate was 0.8 kgf / cm, which was a value that could withstand practical use. Also, no problems such as disconnection of the circuit due to non-deposition of plating and poor conduction of via holes did not occur, no copper plating film remained between the circuits, and the electrical reliability was satisfactory. Was.

Example 5 A four-layer printed wiring board was obtained in the same manner as in Example 1 except that an etching treatment was performed at 30 ° C. for 2 minutes using a 10 mol / L sodium hydroxide aqueous solution. The adhesion strength of the circuit of the obtained printed wiring board to the substrate was 1.0 kgf / cm, which was a value that could withstand practical use. Also, no problems such as disconnection of the circuit due to non-deposition of plating and poor conduction of via holes did not occur, and no copper plating film remained between the circuits.
The electrical reliability was satisfactory.

Example 6 A four-layer printed wiring board was obtained in the same manner as in Example 1, except that an etching treatment was performed at 40 ° C. for 5 minutes using a 5 mol / L sodium hydroxide aqueous solution. The adhesion strength of the circuit of the obtained printed wiring board to the substrate was 1.0 kgf / cm, which was a value that could withstand practical use. Also, no problems such as disconnection of the circuit due to non-deposition of plating and poor conduction of via holes did not occur, and no copper plating film remained between the circuits.
The electrical reliability was satisfactory.

Example 7: Without electroless copper plating, instead of nickel sulfate hexahydrate 0.1 mol / l, glycine 0.3 mol / l, sodium phosphinate 0.1 mol / l Using the same electroless nickel plating solution having a pH of 7 and immersing it at 60 ° C. for 1 minute to perform electroless nickel plating to form a nickel plating film having a thickness of 0.1 μm, the same procedure as in Example 1 was repeated. A layer printed wiring board was obtained. The adhesion strength of the circuit of the obtained printed wiring board to the substrate is 1.1 kgf / cm,
This value was a value that could withstand practical use. Also, no problems such as disconnection of the circuit due to non-deposition of plating and poor conduction of via holes did not occur, no copper plating film remained between the circuits, and the electrical reliability was satisfactory. Was.

Example 8: On the surface of the four-layer printed wiring board obtained by the procedure of Example 1, in the same procedure as in Example 1, form an insulating layer resist, form a via hole, form a through hole, and electrolessly. A six-layer printed wiring board was obtained by performing formation of a copper plating film, heat treatment, formation of an electrolytic copper plating film, and patterning by photolithography. The adhesion strength of the circuit of the obtained printed wiring board to the substrate was 1.0 kgf / cm, which was a value that could withstand practical use. In addition, problems such as disconnection of the circuit due to undeposited plating and poor conduction of the via hole did not occur.
Further, no residual copper plating film was observed between the circuits, and the electrical reliability was sufficiently satisfactory.

Comparative Example 1: Electroless copper plating on a resist surface in the same procedure as in Example 1 except that etching was performed at 80 ° C. for 2 hours using an aqueous solution of 0.05 mol / L sodium hydroxide. The process up to the formation of the film was performed. As a result, a large number of undeposited portions of electroless copper plating were formed on the resist surface, and it was not possible to obtain a printed wiring board using this.

Comparative Example 2 An electroless copper plating film was formed on a resist surface in the same procedure as in Example 1 except that an etching treatment was performed at 25 ° C. for 1 minute using a 12 mol / liter sodium hydroxide aqueous solution. Performed up to formation. As a result, undeposited portions of electroless copper plating were formed on the side surfaces of a large number of via holes, and a part of the insulating layer resist was peeled off from the substrate. Therefore, a printed wiring board could not be obtained by using this.

Comparative Example 3: Heat treatment after electroless copper plating was 9
A four-layer printed wiring board was obtained in the same procedure as in Example 1, except that the substrate was held in a heating furnace maintained at 0 ° C. for 3 hours. The adhesive strength of the circuit of the obtained printed wiring board to the substrate was 0.7 kgf / cm, and a value that could withstand practical use was not obtained.

A four-layer printed wiring board was obtained in the same procedure as in Example 1, except that the heat treatment after the electroless copper plating was performed by holding the substrate in a heating furnace maintained at 310 ° C. for one minute. Although the adhesion strength of the circuit to the substrate of the obtained printed wiring board was 0.8 kgf / cm, partial discoloration and deterioration were observed in the insulating layer resist, and the use of this as an electronic component lacked reliability. Therefore, it was not practically usable.

[0031]

As described above, according to the present invention,
It is possible to form an electroless plating film having excellent fine patterning properties on the surface of the insulating layer, which has been difficult in the past, and it is possible to obtain a high-density multilayer printed wiring board by a method excellent in economy and workability.

Claims (3)

[Claims] An insulating layer is formed on all or a part of an insulating substrate surface on which a conductive circuit is formed, and then the surface of the insulating layer is subjected to electroless plating and patterning to form a conductive circuit, and this is repeated. In the process of manufacturing a multilayer printed wiring board by, before performing electroless plating on the insulating layer surface,
A method for producing a multilayer printed wiring board, wherein the insulating layer is pretreated with a 0.1 to 10 mol / l alkali metal hydroxide aqueous solution, subjected to electroless plating, and then heat-treated at 100 to 300 ° C. . 2. The method for manufacturing a multilayer printed wiring board according to claim 1, wherein after the electroless plating is performed, an electrolytic copper plating is further performed. 3. The method for manufacturing a multilayer printed wiring board according to claim 1, wherein said insulating layer is an alkali-developing ultraviolet light-sensitive resist.