JP2000044799A - Polyimide resin solution and preparation of multilayered printed wiring board using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide, by a build-up process, a multilayered printed wiring board having improvements in the connection reliability between the inductive layers and bonding strength to a plating skin, and to provide a preparative process for a polyimide resin soln. capable of achieving the high densification, light- weighing, and small-holing and that for a multilayered printed wiring board using this resin soln. SOLUTION: A polyimide resin soln. has a resin particulate of an average particle dia. ranging from 0.01 to 10 μm and of the content of 0.1 to 50 vol.% relative to the resin content of a polyimide resin. In addition, a preparative process for a multilayered printed wiring board in which an insulating base board formed with a conductive circuit thereon forms on at least a part thereof an insulating resin layer and, on the surface of the resin layer, a metal layer is formed by plating, comprises coating on the insulating base board a polyimide resin soln. contg. a solvent soluble-type polyimide resin and a resin particulate having better dissolving ability to an oxidizing agent than that of the polyimide resin, thereafter removing the solvent to thereby give an insulating resin layer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyimide resin solution having a high density and improved connection reliability between conductor layers, and to an improvement in a method for manufacturing a multilayer printed wiring board using the same.

[0002]

2. Description of the Related Art A multilayer printed wiring board is formed by laminating a plurality of conductor layers and insulating layers. In recent years, as portable electronic devices have become smaller and thinner, the multilayer printed wiring board has become a component thereof. The size and thickness of the plate have also been required to be high, that is, high density. One technique to meet this demand is to increase the conduction density between the conductor layers of a multilayer printed wiring board by forming a hole for conducting between the conductor layers from a conventional through-type through-hole to provide conduction between any conductor layers. The diameter of the hole is reduced by using a penetrating via hole.

A build-up method has attracted attention as a method of manufacturing a multilayer printed wiring board that satisfies this method. As one of the methods, an insulating resin layer is formed on the surface of a printed wiring board serving as a core material. After forming through-holes or via holes for conducting between conductive layers at desired locations, the surface of the insulating resin layer, including the side walls of the holes, is roughened by etching, and then conductive by electroless plating or the like. There is a method of manufacturing a multilayer printed wiring board by repeating a process of forming a circuit by forming a copper film by electroplating to a desired thickness as required after the formation, and then patterning the circuit as required. In the multilayer printed wiring board obtained by this method, a via hole having a diameter of about 100 μm can be used as a hole for conduction between conductive layers, and a through hole having a diameter of several hundred μm machined by a conventional drill or the like. Compared to a multilayer printed wiring board having only holes for conduction between conductor layers, there is a possibility that conduction density between conductor layers can be greatly increased.

However, one of the biggest problems in the above method is that the adhesion strength of the plating film applied to the surface of the insulating resin layer cannot be sufficiently obtained. In order to solve this problem, fine particles having different solubility from the insulating resin are contained in the insulating resin, and the fine particles are selectively eluted during the etching treatment of the surface of the insulating resin layer, so that the fine particles are dissolved on the surface of the insulating resin layer. By forming fine and complicated irregularities, between the plating film formed on the surface of the insulating resin layer,
A method of producing a so-called anchor effect is used. In addition, as the fine particles used at this time, inorganic substances such as calcium carbonate have been conventionally used, but a method using an organic substance in consideration of moisture resistance and insulation reliability has been studied.

[0005]

However, although the multilayer printed wiring board obtained by this method has been partially put into practical use, since the resin generally used as the insulating resin layer is an epoxy resin, it takes a long time. In applications that require high-temperature heat resistance, problems such as deterioration of the insulating resin layer due to heat occur, so that at present, sufficient connection reliability between conductor layers has not been obtained.

Therefore, as a means for dealing with problems such as deterioration due to heat, a method using a polyimide resin as an insulating resin layer has been studied. The formation of the polyimide resin film is usually performed by applying a polyamic acid, which is a precursor of the polyimide resin, and imidizing it by a heat treatment at about 400 ° C. However, when the polyimide precursor contains resin particles having excellent solubility in order to obtain the above effect,
The high-temperature heat treatment at the time of imidization causes the resin fine particles to melt, degrade, carbonize, and the like, so that not only the expected effect is not obtained, but also, in some cases, the properties of the entire insulating resin layer may be adversely affected.

The present invention makes it possible to obtain a multilayer printed wiring board having improved connection reliability between conductor layers and improved adhesion strength of a plating film by a build-up method, which has been difficult in the past, and to provide this multilayer printed wiring board. It is an object of the present invention to provide a polyimide resin solution capable of achieving high density, light weight, and small diameter of the same, and a method for manufacturing a multilayer printed wiring board using the same.

[0008]

The present inventor has solved the above-mentioned problem by using a specific polyimide resin solution which does not require a high-temperature heat treatment at the time of film formation as a polyimide resin used as a base material of the insulating resin layer. We have found out what we can do and completed the present invention.

That is, in order to achieve the above object, a first embodiment of the present invention provides a polyimide resin solution containing a solvent-soluble polyimide resin and resin fine particles having higher solubility in an oxidizing agent than the polyimide resin. Wherein the average particle size of the resin fine particles is 0.01 to 10
μm, and the content of the resin fine particles is in the range of 0.1 to 50% by volume based on the polyimide resin content.

A second embodiment of the present invention is obtained by forming an insulating resin layer on at least a part of an insulating substrate on which a conductor circuit is formed, and forming a metal layer on the surface of the insulating resin layer by plating. In the method for manufacturing a multilayer printed wiring board, a polyimide resin solution containing a solvent-soluble polyimide resin and resin fine particles having higher solubility than the polyimide resin with respect to an oxidizing agent is applied to the insulating substrate, and then the solvent is applied. And a method for manufacturing a multilayer printed wiring board in which an insulating resin layer is formed by removing the resin.

[0011]

DETAILED DESCRIPTION OF THE INVENTION In the present invention, a polyimide resin solution containing a solvent-soluble polyimide resin and resin fine particles having higher solubility than an oxidizing agent than the polyimide resin is provided on an insulating substrate on which a conductive circuit is formed. The multi-layer printed wiring board is manufactured by coating and then removing the solvent to form an insulating resin layer. As described above, when a conventional polyimide resin is used as an insulating resin layer between conductor layers of a multilayer printed wiring board, it is extremely difficult to incorporate resin fine particles into the polyimide resin. This is because ordinary resins other than polyimide resins cause transformation such as melting, deterioration, and carbonization by a high-temperature heat treatment of about 400 ° C. necessary for imidizing polyamic acid. In addition, resin fine particles having heat resistance to the heat treatment hardly exist other than the polyimide resin.

Therefore, in the present invention, when a polyimide resin film is formed, a so-called solvent-soluble polyimide resin which has been dissolved in a solvent in advance, is used instead of a conventional method of heat condensation using a polyamic acid. This is done by removing this solvent in the process. In this method, depending on the type of the solvent used, for example, even when N-methyl-2-pyrrolidone which is a high boiling point solvent is used, a heat treatment at about 200 ° C. is sufficient. The polyimide resin solution used in the present invention is a solution containing a polyimide resin and resin fine particles in the solution, and in this case, as the polyimide resin, a polyimide resin soluble in a solvent is used as described above. There is no particular limitation.

On the other hand, the resin fine particles need only have a structure which is more easily dissolved in a certain kind of solution than the polyimide resin as a base material, and the structure is not particularly limited, but the polyimide resin is high in ordinary oxidizing agents. It is important that the resin fine particles have a structure that is easily dissolved in an oxidizing agent because of having resistance, and examples thereof include a rubber-modified epoxy resin and butadiene rubber. The average particle diameter of the resin fine particles is preferably in the range of 0.01 to 10 μm. The reason is that if the average particle diameter of the resin fine particles is less than 0.01 μm, the irregularities formed on the surface of the resin layer after the etching treatment are performed. Is insufficient to obtain a sufficient anchoring effect. On the other hand, if it exceeds 10 μm, there is no problem in terms of the anchoring effect. This is because problems such as residue are likely to occur, and the thickness of the insulating resin layer may not be sufficiently obtained. Further, the content of the resin fine particles in the polyimide resin solution is preferably in the range of 0.1 to 50% by volume based on the content of the polyimide resin. The reason is that if the content is less than 0.1% by volume, the density of irregularities formed on the resin layer surface by the etching treatment is insufficient to obtain a sufficient anchor effect,
If the content exceeds 50% by volume, the characteristics of the insulating resin layer containing the resin fine particles cannot fully utilize the characteristics inherent to the polyimide resin.

On the other hand, in the present invention, the plating treatment for forming a metal layer on the surface of the polyimide resin film is not particularly limited, but after forming the polyimide resin film and subjecting it to an appropriate etching treatment using a solution such as an oxidizing agent. After adsorbing a catalytic metal such as palladium as a plating catalyst, electroless plating is performed, and if necessary, the metal layer is made thicker by electroplating. In addition, circuit patterning
A conventionally known method may be used. For example, the method can be performed by a method such as a subtractive method, a semi-additive method, or a full-additive method. Then, after patterning the circuit layer on the surface of the insulating resin layer in the present invention, an insulating resin layer is further formed on the surface, and the plating can be repeated a desired number of times, whereby the printed wiring board can be multilayered as many times as desired. Also, according to a known method, it is possible to form conduction holes such as through holes and via holes in the insulating resin layer and form a plating film including the side wall portions of the holes, whereby conduction between the conductor layers can be obtained. Needless to say.

[0015]

EXAMPLES Next, examples of the present invention will be described in detail together with comparative examples. [Example 1] 335 mm in length, 510 mm in width, and 0.4 in thickness
A double-sided printed wiring board having a circuit with a minimum pitch of 100 μm is prepared by patterning a copper film with ferric chloride using a double-sided copper-clad glass epoxy resin substrate having a thickness of 18 μm (copper thickness: 18 μm). did. On the surface of the obtained core material, 70% by volume of a block copolymer type polyimide “Cubilon” (trade name, manufactured by PI Technology), 10% by volume based on the polyimide resin, and a spherical rubber having an average particle diameter of 2 μm A modified epoxy resin and a polyimide resin solution comprising N-methyl-2-pyrrolidone as a solvent are applied, dried at 90 ° C. for 30 minutes, and then dried at 200 ° C.
For 30 minutes to completely remove N-methyl-2-pyrrolidone in the polyimide resin film.

By the above processing, a thickness of 30
A μm polyimide resin film was formed. Thereafter, using a carbon dioxide laser, a via hole having a processing energy of 210 J / cm ² , a number of shots of 3, and a diameter of 50 μm for conducting with the core material was formed at a desired position on the substrate. Further, through holes having a diameter of 400 μm were formed at desired positions on the substrate by drilling. Thereafter, the substrate is immersed in a 70 ° C. aqueous solution containing 50 g / l of potassium permanganate and 40 g / l of sodium hydroxide for 10 minutes to etch the surface of the polyimide resin film and to leave a residue between the via hole and the core material circuit. Was removed.

Thereafter, the manganese remaining on the substrate was reduced and removed, and the substrate was immersed in a catalyst application liquid "OPC-80 Catalyst M" (trade name, manufactured by Okuno Pharmaceutical Co., Ltd.) at 25 ° C. for 5 minutes and washed with water. Then, the catalyst activity promoting liquid “OPC-55
5 Accelerator ”(Okuno Pharmaceutical Co., Ltd .: trade name)
For 5 minutes at 25 ° C., and then washed with water. Thereafter, 10 g / l of copper sulfate pentahydrate, 30 g / l of disodium ethylenediaminetetraacetate, 5 ml / l of a 37% formaldehyde solution, 0.5 g / l of polyethylene glycol (molecular weight 1000),
It contains 10 mg / l of 2,2'-bipyridyl and contains p
The substrate was immersed in an electroless copper plating solution at 65 ° C. with H adjusted to 12.5 for 20 minutes to form a 0.5 μm thick film on the surface of the substrate including the via hole and the side wall of the through hole.
Was formed.

Then, 80 g / l of copper sulfate pentahydrate, 180 g / l of sulfuric acid, and 60 mg of chloride ion
/ L, immersed in a 23 ° C. electrolytic copper plating solution containing 10 ml / L of a brightener, subjected to electrolytic copper plating at a cathode current density of 3 A / dm ² for 30 minutes using a phosphorous-containing copper plate as an anode, via holes and through holes A copper plating film having a thickness of 18 μm was formed on the surface of the substrate including the side wall portions. Furthermore, a minimum pitch of 100 μm is applied to the copper plating film surface using a photolithography technique according to a conventional method.
After patterning the etching resist layer, an etching process is performed using a ferric chloride solution of 40 Baume at a temperature of 50 ° C. and a shower pressure of 2 kg / cm ² for 40 seconds, and the resist layer is peeled off. Was formed. Through the above steps, a four-layer printed wiring board was obtained.

The adhesion strength of the plating film of the obtained four-layer printed wiring board is 1.5 kgf / cm, the insulation resistance between the circuits is 2 × 10 ¹² Ω, and the insulation resistance between the circuits separated by the polyimide resin film is The value was 2 × 10 ¹² Ω. Further, this printed wiring board was allowed to stand still in a thermo-hygrostat kept at 85 ° C. and a relative humidity environment of 85%, during which time a voltage of 50 V was continuously applied between the above-mentioned circuits. And 1
The adhesion strength of the plating film after holding for 000 hours is 1.0
kgf / cm, insulation resistance between circuits is 1 × 10 ¹¹ Ω,
The insulation resistance between circuits separated by the polyimide resin film is 1
× 10 ¹¹ Ω. On the other hand, the adhesion strength of the plating film after holding the printed wiring board obtained in the above step in the atmosphere at 150 ° C. for 1,000 hours was 1.0 kgf / cm, and from the above results, the multilayer printed sheet obtained by the above manufacturing method was used. It can be said that the wiring board has sufficient connection reliability.

Example 2 The procedure of Example 1 was repeated except that a rubber-modified epoxy resin having an average particle diameter of 0.01 μm was used and the content in the polyimide resin solution was set to 50% by volume with respect to the polyimide resin. 4 by the same procedure as in Example 1.
A layered printed wiring board was obtained.

The adhesion strength of the plating film of the obtained four-layer printed wiring board is 1.3 kgf / cm, the insulation resistance between the circuits is 1 × 10 ¹² Ω, and the insulation resistance between the circuits separated by the polyimide resin film. The value was 1 × 10 ¹² Ω. Further, this printed wiring board was allowed to stand still in a thermo-hygrostat kept at 85 ° C. and a relative humidity environment of 85%, during which time a voltage of 50 V was continuously applied between the above-mentioned circuits. And 1
After holding for 000 hours, the adhesion strength of the plating film is 1.0
kgf / cm, insulation resistance between circuits is 1 × 10 ¹¹ Ω,
The insulation resistance between circuits separated by the polyimide resin film is 1
× 10 ¹¹ Ω. On the other hand, the adhesion strength of the plating film after holding the printed wiring board obtained in the above step in the atmosphere at 150 ° C. for 1,000 hours is 1.0 kgf / cm, and the multilayer print obtained by the above method from the above results. It can be said that the wiring board has sufficient connection reliability.

Example 3 The procedure of Example 1 was repeated except that a rubber-modified epoxy resin having an average particle size of 10 μm was used and the content in the polyimide resin solution was set to 0.1% by volume based on the polyimide resin. A four-layer printed wiring board was obtained in the same procedure as in Example 1.

The adhesion strength of the plating film of the obtained four-layer printed wiring board is 1.3 kgf / cm, the insulation resistance between the circuits is 2 × 10 ¹² Ω, and the insulation resistance between the circuits separated by the polyimide resin film. The value was 5 × 10 ¹² Ω. Further, this printed wiring board was allowed to stand still in a thermo-hygrostat kept at 85 ° C. and a relative humidity environment of 85%, during which time a voltage of 50 V was continuously applied between the above-mentioned circuits. And 1
After holding for 000 hours, the adhesion strength of the plating film is 1.0
kgf / cm, insulation resistance between circuits is 1 × 10 ¹¹ Ω,
The insulation resistance between circuits separated by the polyimide resin film is 1
× 10 ¹² Ω. On the other hand, the adhesion strength of the plating film after holding the printed wiring board obtained in the above step in the atmosphere at 150 ° C. for 1,000 hours is 1.0 kgf / cm, and the multilayer print obtained by the above method from the above results. It can be said that the wiring board has sufficient connection reliability.

Comparative Example 1 A four-layer printed wiring board was obtained in the same manner as in Example 1 except that a rubber-modified epoxy resin having an average particle diameter of less than 0.01 μm was used.

The adhesion strength of the plating film of the obtained four-layer printed wiring board is 0.7 kgf / cm, the insulation resistance between the circuits is 2 × 10 ¹³ Ω, and the insulation resistance between the circuits separated by the polyimide resin film. The value was 2 × 10 ¹³ Ω. Further, this printed wiring board was allowed to stand still in a thermo-hygrostat kept at 85 ° C. and a relative humidity environment of 85%, during which time a voltage of 50 V was continuously applied between the above-mentioned circuits. And 1
After holding for 000 hours, the adhesion strength of the plating film is 0.5
kgf / cm, insulation resistance between circuits is 1 × 10 ¹² Ω,
The insulation resistance between circuits separated by the polyimide resin film is 1
× 10 ¹² Ω. On the other hand, the adhesion strength of the plating film after holding the printed wiring board obtained in the above step in the atmosphere at 150 ° C. for 1000 hours is 0.5 kgf / cm, and the multilayer print obtained by the above method from the above results. The wiring board did not have sufficient reliability in terms of the adhesion of the plating film.

[Comparative Example 2] In Example 1, the rubber modified epoxy resin had an average particle diameter of 15 μm and a maximum diameter of 30 μm.
A four-layer printed wiring board was obtained in the same manner as in Example 1 except that m was used.

The adhesion strength of the plating film of the obtained four-layer printed wiring board is 1.4 kgf / cm, the insulation resistance between the circuits is 1 × 10 ⁸ Ω, and the insulation resistance between the circuits separated by the polyimide resin film. The value was 2 × 10 ⁷ Ω. Further, this printed wiring board was allowed to stand still in a thermo-hygrostat kept at 85 ° C. and a relative humidity environment of 85%.
The voltage of 0 V was continuously applied. And 100 under the environment
After holding for 0 hours, the adhesion strength of the plating film is 1.0 kg
f / cm, the insulation resistance between circuits and the insulation resistance between circuits separated by a polyimide resin film are all 1 × 10Ω
It was below. On the other hand, the adhesion strength of the plating film after holding the printed wiring board obtained in the above step in the atmosphere at 150 ° C. for 1,000 hours is 0.9 kgf / cm, and the multilayer print obtained by the above method from the above results. The wiring board does not have sufficient reliability particularly in terms of insulation.

[Comparative Example 3] In Example 1, the content of the rubber-modified epoxy resin was 0.0
A four-layer printed wiring board was obtained in the same procedure as in Example 1 except that the volume was 5% by volume.

The adhesion strength of the plating film of the obtained four-layer printed wiring board is 0.8 kgf / cm, the insulation resistance between the circuits is 1 × 10 ¹³ Ω, and the insulation resistance between the circuits separated by the polyimide resin film. The value was 1 × 10 ¹³ Ω. Further, this printed wiring board was allowed to stand still in a thermo-hygrostat kept at 85 ° C. and a relative humidity environment of 85%, during which time a voltage of 50 V was continuously applied between the above-mentioned circuits. And 1
After holding for 000 hours, the adhesion strength of the plating film is 0.6
kgf / cm, insulation resistance between circuits is 1 × 10 ¹² Ω,
The insulation resistance between circuits separated by the polyimide resin film is 1
× 10 ¹² Ω. On the other hand, the adhesion strength of the plating film after holding the printed wiring board obtained in the above step in the atmosphere at 150 ° C. for 1,000 hours is 0.6 kgf / cm, and the multilayer print obtained by the above method from the above results. The wiring board did not have sufficient reliability, particularly in terms of the adhesion strength of the plating film.

Comparative Example 4 A four-layer printed wiring board was obtained in the same manner as in Example 1, except that the content of the rubber-modified epoxy resin was changed to 60% by volume based on the polyimide resin. .

The adhesion strength of the plating film of the obtained four-layer printed wiring board is 1.5 kgf / cm, the insulation resistance between the circuits is 5 × 10 ¹¹ Ω, and the insulation resistance between the circuits separated by the polyimide resin film. The value was 5 × 10 ¹¹ Ω. Further, this printed wiring board was allowed to stand still in a thermo-hygrostat kept at 85 ° C. and a relative humidity environment of 85%, during which time a voltage of 50 V was continuously applied between the above-mentioned circuits. And 1
After holding for 000 hours, the adhesion strength of the plating film is 1.2
kgf / cm, insulation resistance between circuits is 1 × 10 ¹⁰ Ω,
The insulation resistance between circuits separated by the polyimide resin film is 1
× 10 ⁷ Ω. On the other hand, the adhesion strength of the plating film after holding the printed wiring board obtained in the above step in the air at 150 ° C. for 1,000 hours is 1.1 kgf / cm,
From the above results, the multilayer printed wiring board obtained by the above method did not have sufficient reliability particularly in terms of insulation.

Comparative Example 5 Example 1 was the same as Example 1 except that the insulating resin layer was an epoxy resin film containing 10% by volume of a rubber-modified epoxy resin having an average particle size of 2 μm and having a glass transition point of 130 ° C. A four-layer printed wiring board was obtained in the same procedure.

The adhesion strength of the plating film of the obtained four-layer printed wiring board is 1.5 kgf / cm, the insulation resistance between the circuits is 1 × 10 ¹² Ω, and the insulation resistance between the circuits separated by the epoxy resin film. The value was 1 × 10 ¹² Ω. Further, this printed wiring board was allowed to stand still in a thermo-hygrostat kept at 85 ° C. and a relative humidity environment of 85%, during which time a voltage of 50 V was continuously applied between the above-mentioned circuits. And in this environment 10
After holding for 00 hours, the adhesion strength of the plating film is 0.2k
gf / cm, insulation resistance between circuits is 1 × 10 ¹² Ω, insulation resistance between circuits separated by epoxy resin film is 1 × 1
It was 0 ⁸ Ω. On the other hand, when the printed wiring board obtained in the above step was kept in the atmosphere at 150 ° C. for 1000 hours, the epoxy resin layer was carbonized and deformed. From the above results, the multilayer printed wiring board obtained by the above method did not have sufficient reliability.

[0034]

As described above, according to the present invention, it is possible to obtain a multilayer printed wiring board with improved connection reliability between conductor layers and improved adhesion strength of a plating film by a build-up method which has been difficult in the past. In addition, it is possible to provide a polyimide resin solution capable of achieving high density, light weight, and small diameter of the multilayer printed wiring board, and a method for manufacturing a multilayer printed wiring board using the same.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI theme coat ゛ (Reference) C08L 63:00 9:00)

Claims (4)

[Claims] 1. A polyimide resin solution comprising: a solvent-soluble polyimide resin; and resin fine particles having better solubility in an oxidizing agent than the polyimide resin. 2. The resin fine particles having an average particle size of 0.01 to 0.01.
2. The polyimide resin solution according to claim 1, wherein the thickness is in a range of 10 [mu] m. 3. The polyimide resin solution according to claim 1, wherein the content of the resin fine particles is in the range of 0.1 to 50% by volume based on the content of the polyimide resin. 4. A method of manufacturing a multilayer printed wiring board obtained by forming an insulating resin layer on at least a part of an insulating substrate on which a conductor circuit is formed, and forming a metal layer on the surface of the insulating resin layer by plating. A polyimide resin solution containing a solvent-soluble polyimide resin and an oxidizing agent and fine resin particles having higher solubility than the polyimide resin is applied to the insulating substrate, and then the solvent is removed to form the insulating resin layer. Forming a multilayer printed wiring board.