JPH0632372B2 - Printed wiring board, manufacturing method thereof, and adhesive for electroless plating - Google Patents

Description

TECHNICAL FIELD The present invention relates to an adhesive for electroless plating used for manufacturing a printed wiring board, and particularly to heat resistance, electrical insulation, chemical stability and adhesiveness. The present invention relates to an excellent adhesive, a printed wiring board using the adhesive, and a method for manufacturing the same.

[Conventional technology]

In recent years, the progress of electronics has been remarkable, and accordingly, electronic devices have been further downsized or speeded up. To this end, printed wiring boards, especially ICs and LSs
A printed wiring board on which components such as I are mounted is required to have high density and high reliability by fine patterns.

Conventionally, as a technique for forming a conductor circuit on a printed wiring board, a method called an etched foil method in which a copper foil is laminated on a substrate and then photoetched is typical. This method is characterized in that it can form a conductor circuit with excellent adhesion to the substrate, but on the other hand, it has a major drawback that it is difficult to obtain a high-precision fine pattern by etching because the copper foil is thick. However, there are various problems such as the manufacturing process is complicated and the efficiency is low.

Therefore, recently, in order to form a conductor circuit on a wiring board,
An additive method is used in which an adhesive containing diene-based synthetic rubber is applied to the surface of a substrate to form an adhesive layer, the surface of this adhesive layer is roughened, and then electroless plating is applied to form a conductor circuit. .

However, since the adhesive used under this known method contains a synthetic rubber in its composition, there are drawbacks such as a large decrease in adhesion strength at high temperature and a swelling of the electroless plating film during soldering. Yes, low heat resistance,
There is a drawback that electric properties such as surface resistance are not sufficient, and the range of use is considerably limited.

Further, as the "resin composition for printed wiring board" used for forming such a conductor pattern by electroless plating, there is one disclosed in JP-A-53-140344. However, this composition is one in which the thermosetting resin component forming the spherical particles in the composition is not etched, i.e. insoluble in oxidizing agents. Since the adhesive layer on the substrate obtained by the etching roughening has irregularities of about 20 μm, it is difficult to obtain a conductor having a fine pattern as the conductor formed on this adhesive layer, and the insulating property between the patterns is likely to be poor. Further, it is inferior in heat resistance and electric characteristics, so that there is a defect that it is not preferable when mounting parts and the like.

[Problems to be Solved by the Invention]

As described above, conventionally, an adhesive for electroless plating, which has excellent heat resistance, electrical characteristics, adhesion between the substrate and the electroless plating film, and is easy to handle, has not yet been known. The fact is that the manufacture of printed wiring boards using such an adhesive has not been attempted yet.

On the other hand, the present inventors have previously conducted various studies in order to eliminate the above-mentioned drawbacks, and disclosed Japanese Patent Application No. 60-118898 (Japanese Patent Application Laid-Open No. 61-2798).
6875).

However, the previously proposed adhesive has a problem that the anchor tends to become unclear unless there is a significant difference in the solubility between the heat-resistant resin fine powder and the matrix heat-resistant resin in the oxidizing agent.

The object of the present invention is to solve the above-mentioned drawbacks and problems associated with the prior art that the conventional electroless plating adhesive has, and to have excellent heat resistance, electrical characteristics, and adhesion to an electroless plating film, Further, the present invention proposes an adhesive for electroless plating which can be implemented relatively easily, an advantageous printed wiring board using this adhesive, and a manufacturing method thereof.

[Means for Solving the Problems]

Therefore, the inventors of the present invention have aimed to improve the invention previously proposed by the present inventors, and as a result of earnest research to develop an adhesive capable of easily forming a more definite anchor, as a result, heat resistance The present invention has been newly discovered that the aforementioned problems can be solved by using secondary particles obtained by aggregating fine particles having an average particle diameter of 2 μm or less as the resin fine powder, and completed the present invention. That is, a pre-cured heat-resistant resin fine powder that is soluble in an oxidizer is dispersed in an uncured heat-resistant resin liquid that has a property of being hardly soluble in an oxidant by a curing treatment. And an adhesive layer formed on the substrate by applying the adhesive agent and drying and curing the adhesive layer, and at least a part of the fine powder dispersed on the surface portion of the adhesive layer is dissolved and removed. In the method for producing a wiring board, which comprises roughening the surface of the adhesive layer and then performing electroless plating, secondary particles obtained by aggregating fine particles having an average particle diameter of 2 μm or less are used as the heat-resistant resin fine powder. When used, the printed wiring board according to the present invention can be advantageously manufactured.

The thus-obtained printed wiring board according to the present invention has a cured heat-resistant resin fine powder that is soluble in an oxidant on the substrate and is hardly soluble in the oxidant by a curing treatment. An adhesive layer for electroless plating, which is dispersed in an uncured heat-resistant resin liquid having the following properties, is provided,
In a printed wiring board in which a plated conductor layer is formed via this adhesive layer, from the secondary particles obtained by aggregating fine particles having an average particle size of 2 μm or less as the heat-resistant resin fine powder of the adhesive layer. It is characterized by using the following.

[Work]

The adhesive for electroless plating according to the present invention has a property that it becomes hardly soluble in an oxidant when the heat-resistant resin fine powder that has been previously hardened and can be dissolved by the oxidant is hardened. The heat-resistant resin fine powder, which is dispersed in a hardening heat-resistant resin liquid, comprises secondary particles obtained by aggregating fine particles having an average particle diameter of 2 μm or less.

The reason why such an adhesive is used in the electroless plating of a printed wiring board is that the adhesion strength between the substrate and the electroless plated film is increased, and as a result, a highly reliable conductor pattern can be obtained. That is, when heat-resistant resin fine powder that has been previously cured is dispersed in a heat-resistant resin liquid, the heat-resistant resin that forms a matrix when applied on a substrate and dried and cured (hereinafter, heat-resistant resin that forms a matrix) Resin is called "matrix heat resistant resin")
An adhesive layer is formed in which the heat-resistant resin fine powder is uniformly dispersed. On the other hand, since the heat-resistant resin fine powder and the matrix heat-resistant resin have different solubilities with respect to an oxidizing agent, when the adhesive layer is treated with an oxidizing agent, it is dispersed in the surface portion of the adhesive layer. Only the fine powder that is soluble in the oxidizing agent is dissolved and removed. As a result, a clear anchor is formed on the surface of the adhesive layer, and the surface of the adhesive layer can be roughened. Moreover, the effect is that, as shown in FIG. 2, since the secondary particles formed by aggregating fine particles are used as the heat resistant resin fine powder, the shape of the anchor itself can be made more complicated. .

Now, the heat-resistant resin fine powder used in the present invention has been previously cured. If the heat-resistant resin fine powder that is not cured is used, it will dissolve in the liquid when the heat-resistant resin liquid or the liquid obtained by dissolving this resin in a solvent is added. Therefore, when an adhesive containing such uncured resin fine powder is applied to a substrate and dried and cured, an adhesive layer in which the matrix heat-resistant resin and the heat-resistant resin fine powder are eutectic is formed. As a result, in the treatment with the above-mentioned oxidizing agent, the adhesive layer is almost uniformly dissolved, and it becomes impossible to selectively dissolve and remove the adhesive layer surface necessary for roughening, which hinders the formation of a clear anchor. .

On the other hand, if the heat-resistant resin fine powder is hardened in advance, it becomes insoluble in the heat-resistant resin liquid or the solvent that dissolves this resin, and therefore the heat-resistant resin fine powder is added to the matrix heat-resistant resin liquid. It is possible to obtain an adhesive in which the powder is uniformly dispersed, and as a result, it is possible to facilitate the formation of a clear and uniform anchor as described above.

As such a heat-resistant resin fine powder, it has excellent heat resistance and electrical insulation, is stable to ordinary chemicals, and is hardly soluble in a heat-resistant resin liquid or a solvent that dissolves this resin by pre-curing treatment. A material that can be dissolved and can be dissolved by an oxidizing agent such as chromic acid is used. For example, at least one selected from an epoxy resin, a polyester resin, and a bismaleimide-triazine resin. Among them, the epoxy resin is excellent in characteristics and is most suitable.

As a method for curing the fine powder, a method of curing by heating or a method of curing by adding a catalyst can be used. Among them, the method of curing by heating is the most practical.

In the treatment with an oxidizing agent, an oxidizing agent such as chromic acid, chromate salt, permanganate, ozone, etc. is used. Particularly, a mixed acid aqueous solution of chromic acid and sulfuric acid can be advantageously used.

In the present invention, the heat-resistant resin fine powder has a shape as shown in FIG. 1 which is a secondary particle obtained by aggregating fine particles having an average particle diameter of 2 μm or less. By using the fine powder having such a shape, the shape of the anchor formed by dissolution and removal accompanying the treatment with the oxidizing agent can be complicated. That is, the present invention makes the shape more complicated than the anchor (shown in FIG. 4) formed when primary particles as shown in FIG. 3 which are not aggregated (not secondary particles) are used. It is possible to obtain high adhesion strength such as peel strength and pull strength and stability. However, fine powder formed into secondary particles by agglomerating particles having an average particle diameter of more than 2 μm is not preferable for forming a fine pattern because the anchor formed is too deep. Therefore, in the resin fine powder of the present invention, it is important to aggregate fine particles having an average particle diameter of 2 μm or less into secondary particles,
In particular, it is preferable to use one having a thickness of 1 μm or less. A semi-cured layer or an unreacted functional group may be provided on the surface of the heat-resistant resin fine powder so as not to dissolve in the matrix in order to improve the bonding with the matrix heat-resistant resin.

Now, as the particle size of the secondary particles formed by aggregating the fine powder having a particle size of 2 μm or less as described above, the average particle size is 10 μm or less, more preferably 5 μm or less. Good. The reason is that the average particle size is 1
This is because if it is larger than 0 μm, the density of anchors formed by dissolution and removal as described above becomes low and the anchors are likely to become non-uniform. As a result, the adhesion strength and the reliability of the product are reduced, and the irregularities on the surface of the adhesive layer become more intense than necessary, which makes it difficult to obtain a fine conductor pattern and causes inconvenience in mounting components. is there.

The properties of the secondary particles obtained in this manner are such that they are aggregated with an adhesive force to the extent that they do not dissociate during mixing and return to the primary particles.

The heat-resistant resin fine powder composed of such secondary particles is obtained by, for example, heat-curing the heat-resistant resin and then finely pulverizing it with a jet mill or freeze pulverizer, or before heat-treating the solution. The primary fine particles obtained by spray-drying or by adding an aqueous solution curing agent to an uncured heat-resistant resin emulsion, which is a more preferable method, and stirring,
Agitation is performed by simply heating with a hot air drier or by adding various binders, mixing and drying. Then, after that, it is crushed using a ball mill, an ultrasonic disperser, or the like, and further classified by a wind force classifier, etc.

The shape of the heat-resistant resin fine powder obtained in this way is not only spherical but also has various complicated shapes, and the shape of the anchor formed by this also becomes more complicated. Provides adhesion strength such as strength.

Next, the matrix heat-resistant resin in which the heat-resistant resin fine powder is dispersed has excellent heat resistance, electrical insulation, chemical stability and adhesiveness, and becomes hard to be dissolved in an oxidizer by curing treatment. A resin having characteristics is used. For example, at least one selected from an epoxy resin, an epoxy-modified polyimide resin, a polyimide resin, and a phenol resin, and those obtained by imparting photosensitivity to these resins are used. The one to which this photosensitivity is imparted is suitable as an adhesive for an interlayer insulating material of a build-up wiring board.

As described above, the heat-resistant resin fine powder and the matrix heat-resistant resin after being subjected to the curing treatment have a large difference in the dissolution property with respect to the oxidizing agent. Therefore, when the heat-resistant resin fine powder dispersed in the surface portion of the adhesive layer is dissolved and removed using an oxidizing agent, the matrix heat-resistant resin that is hardly soluble in the oxidizing agent is hardly dissolved and the base material Remains, and a clear anchor is formed on the surface of the adhesive layer. Even if the same kind of heat resistant resin,
For example, a similar effect can be obtained by using an epoxy resin that is easily dissolved in an oxidant as the heat-resistant resin fine powder and using a combination of epoxy resins that are relatively insoluble in the oxidant as the matrix heat-resistant resin. You can

As the heat-resistant resin liquid for dispersing the fine powder, a heat-resistant resin liquid containing no solvent can be used as it is, but a heat-resistant resin liquid having a heat-resistant resin dissolved in the solvent has a low viscosity. Therefore, since the fine powder can be easily dispersed uniformly and can be easily applied to the substrate, it can be advantageously used. Then, as a solvent used for dissolving the heat resistant resin, an ordinary solvent such as methyl ethyl ketone, methyl cellosolve, ethyl cellosolve, butyl carbitol, butyl cellulose, tetralin, dimethylformamide, normal methylpyrrolidone is used. Can be used. The heat-resistant resin liquid that becomes the matrix is, for example, silica, alumina, titanium oxide,
A filler made of an inorganic fine powder such as zirconia may be appropriately mixed.

The blending amount of the heat-resistant resin fine powder with respect to the matrix heat-resistant resin is in the range of 2 to 350 parts by weight, particularly 5 to 20 parts by weight based on 100 parts by weight of the matrix heat-resistant resin solid content.
The range of 0 parts by weight is preferable because the adhesion strength between the substrate and the electroless plated film can be increased. If the blending amount of the heat-resistant resin fine powder is less than 2 parts by weight, the density of the anchor formed by dissolution and removal becomes low, and sufficient adhesion strength between the substrate and the electroless plating film cannot be obtained. If the amount is too large, the entire adhesive layer is almost dissolved, so that no clear anchor is formed.

Next, a method for manufacturing a printed wiring board using the above adhesive will be described.

First, the substrate is coated with an adhesive agent in which the heat-resistant resin fine powder is dispersed in a heat-resistant resin liquid serving as a matrix. The coating method may be any of various means such as a roller coating method, a dip coating method, a spray coating method, a spinner coating method, a curtain coating method and a screen printing method.

In this stage of processing, the thickness of the adhesive layer which is applied and dried and cured on the substrate is usually about 2 to 40 μm. This adhesive layer is used as an interlayer insulating film of a metal substrate or a multilayer wiring board. When it is also used, it can be applied thicker than that. As the substrate used in the present invention, for example, a plastic substrate, a ceramic substrate, a metal substrate, a film substrate, or the like can be used, and specifically, a glass epoxy substrate, a glass polyimide substrate, an alumina substrate, a low temperature fired ceramic. Substrates, aluminum nitride substrates, aluminum substrates, iron substrates, polyimide film substrates, etc.

In the present invention, using these substrates, a single-sided wiring board,
A double-sided through-hole wiring board, such as a multilayer printed wiring board such as a Cu / polyimide multilayer printed wiring board, can be manufactured. Note that the adhesive is not limited to a general coating type, and may be a form in which a plate-shaped or film-shaped adhesive is attached to the surface of the substrate to form the adhesive layer.

Next, in the adhesive layer formed as described above, at least a part of the heat-resistant resin fine powder dispersed on the surface of the adhesive layer is dissolved and removed using an oxidizing agent. The dissolution and removal method is performed by using the above-mentioned oxidizing agent solution and immersing the substrate having the adhesive layer in the solution, or spraying the solution onto the substrate. By this treatment, the surface of the substrate, that is, the surface of the so-called adhesive layer can be roughened. In order to effectively dissolve and remove the heat-resistant resin fine powder, it is an advantageous method to lightly remove the surface portion of the adhesive layer beforehand by polishing with a fine powder abrasive or liquid honing.

Next, electroless plating is applied to the substrate having the roughened adhesive layer surface. Examples of the electroless plating include electroless plating, electroless nickel plating, electroless tin plating, electroless gold plating, electroless silver plating and the like. In particular, at least one of electroless copper plating, electroless nickel plating, and electroless gold plating is suitable. In addition, after performing the electroless plating, different types of electroless plating or electroplating may be further performed, or solder may be coated.

The printed wiring board obtained by carrying out the method of the present invention can be formed with a conductor circuit by other known methods, for example, a method of subjecting the substrate to electroless plating and then etching the circuit or electroless plating. A method of directly forming a circuit or the like can be applied when applying.

〔Example〕

Example 1 (1) Epoxy resin fine powder (manufactured by Toray, trade name: Trepearl EP-B, average particle size 0.5 μm) was placed in a hot air dryer.
Heat treatment was performed at 180 ° C. for 3 hours to aggregate. The agglomerated epoxy resin fine powder is dispersed in acetone, crushed in a ball mill for 5 hours, and then classified using a wind classifier to obtain an epoxy resin fine powder composed of secondary particles having an average particle size of 3.5 μm. A powder was made.

(2) 60 parts by weight of phenol novolac type epoxy resin (made by Yuka Shell, trade name: E-154), bisphenol A
Type Epoxy resin (made by Yuka Shell, trade name: E-1001) 40
Parts by weight, imidazole curing agent (manufactured by Shikoku Kasei, trade name: 2
P4MHZ) 4 parts by weight and 50 parts by weight of the epoxy resin fine powder prepared in (1) above, while adding a butyl cellosolve solvent, a viscosity of 120 cps with a homodisper disperser.
And then kneaded with a three-roll mill to obtain an adhesive.

(3) A glass polyimide substrate (Toshiba Chemical, trade name: Toshiba Dulite Laminated Board-E manufactured by Toshiba Chemical Co., Ltd.) to which the adhesive obtained in (2) above is not adhered, using a roller coater.
L) and then dried and cured at 100 ° C. for 1 hour and at 150 ° C. for 5 hours to form an adhesive layer having a thickness of 20 μm.

(4) Chromic acid (Cr ₂ O ₃ ) 500 g / the substrate obtained in (3) above.
The surface of the adhesive layer was roughened by immersing it in an oxidizing agent composed of an aqueous solution at 70 ° C. for 15 minutes, and then immersing in a neutralizing solution (manufactured by Shipley, trade name: PM950) and washing with water.

(5) The substrate obtained by roughening the surface of the adhesive layer obtained in (4) above, activates the surface of the adhesive layer by applying a palladium catalyst (manufactured by Shipley, trade name: Cataposit 44), It was immersed in an electroless plating solution for additive method having the composition shown in 11 hours for 11 hours to perform electroless copper plating with a plating film thickness of 25 μm.

Copper sulfate (CuSO ₄ .5H ₂ O) 0.06 mol / formalin (37%) 0.30 mol / caustic soda (NaOH) 0.35 mol / EDTA 0.12 mol / additive A little plating temperature: 70-72 ℃ pH: 12.4 As described above The produced wiring board was further subjected to copper plating with an electroplating thickness of 35 μm in a copper sulfide plating bath.

With respect to the printed wiring board thus manufactured, first, the adhesion strength between the substrate and the copper plating film was measured by the method of JIS-C-6481. As a result, the peel strength was 1.85 kg / cm. The change in surface resistance of the adhesive layer after immersion in boiling water at 100 ℃ for 2 hours is 7 × 10 ¹⁴ Ω · cm.
Was 3 × 10 ¹³ Ω · cm. Furthermore, when a heat resistance test was conducted in which the surface of the wiring board was brought into close contact with a hot plate whose surface temperature was kept at 300 ° C and heated for 10 minutes,
No abnormality was found.

〔The invention's effect〕

As described above, according to the present invention, a printed wiring board having excellent heat resistance, electrical characteristics, and adhesion between a substrate and an electroless plating film is provided, and particularly, an effect for surface roughening and an anchor effect are also excellent. The adhesive for electroless plating can be provided.

Moreover, by adopting such an adhesive, it is not necessary to go through complicated steps for surface roughening even when manufacturing a printed wiring board, and therefore the conductor pattern can be easily formed.

In this sense, the present invention can be widely applied to a high-density and high-precision printed wiring board, a hybrid IC wiring board, a multilayer wiring board on which an LSI is mounted, and the like, and therefore the present invention is industrially very useful.

[Brief description of drawings]

FIG. 1 is a front view of secondary particles used in the present invention formed by aggregating fine particles, and FIG. 2 is a partial cross-sectional view showing the shape of an anchor formed on the surface of an adhesive layer by using the secondary particles. FIG. 3 is a front view of primary particles in a conventional example, and FIG. 4 is a partial cross-sectional view showing a shape of a conventional anchor formed on the surface of an adhesive layer by using the primary particles.

Claims (6)

[Claims] 1. An uncured heat-resistant resin having a property of being hardened to a oxidizer by curing a hardened heat-resistant resin fine powder that is soluble in an oxidizer on a substrate. In a printed wiring board provided with an adhesive layer for electroless plating which is dispersed in a liquid, and a plated conductor layer is formed through this adhesive layer, the heat-resistant resin fine powder of the adhesive layer is used as an average. A printed wiring board comprising a secondary particle obtained by aggregating fine particles having a particle diameter of 2 μm or less. 2. A heat-resistant resin fine powder comprising secondary particles obtained by aggregating fine particles having an average particle diameter of 2 μm or less, which are hardened by an oxidizing agent, on a substrate, and hardened. By applying an adhesive which is dispersed in an uncured heat-resistant resin liquid having a property of being hardly soluble in an oxidizing agent, and drying and curing to form an adhesive layer, and the adhesive layer Surface is roughened by dissolving and removing a part of the heat resistant resin fine powder dispersed in this portion, and then electroless plating is performed on the roughened adhesive layer surface to form a printed wiring board. A method for manufacturing a printed wiring board, comprising: 3. A method for manufacturing a printed wiring board, characterized in that a plate-shaped or film-shaped adhesive is used as the adhesive according to claim 2. 4. A cured heat-resistant resin fine powder that is soluble in an oxidant is dispersed in an uncured heat-resistant resin liquid that has a property of being hardly soluble in an oxidant when cured. In the adhesive for electroless plating thus obtained, as the heat-resistant resin fine powder, an adhesive composed of secondary particles obtained by aggregating fine particles having an average particle diameter of 2 μm or less is used. adhesive. 5. The adhesive according to claim 4, wherein
An adhesive for electroless plating, wherein the average particle size of the secondary particles is 10 μm or less. 6. An adhesive for electroless plating, wherein the adhesive according to claim 4 is plate-shaped or film-shaped.