JPH028281A - Adhesive for nonelectrolytic plating - Google Patents

Abstract

PURPOSE:To obtain the title adhesive for printed-wiring board having excellent adhesion with a plating film and good heat resistance and electrical insulating properties by using a pseudo-particle covering a fine powder insoluble to an oxidant on the surface of matrix particle soluble to the oxidant. CONSTITUTION:The aimed adhesive obtained by dispersing (A) pseudo-particle for anchor formation obtained by bonding either one of (ii) heat resistant resin powder soluble to an oxidant, subjected to curing treatment and having <=0.8mum average particle size or (iii) inorganic powder soluble to the oxidant and having <=0.8mum average particle size to the surface of (i) a heat resistant powder soluble to an oxidant, subjected to curing treatment and having <=10mum particle size into (B) uncured heat resistant resin liquid capable of having properties slightly soluble to an oxidant by curing treatment. The bonding between the component (i) and component (ii) of component (iii) is preferably carried out by mutually fusing or through a binder.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to electroless plating used for manufacturing printed wiring boards, and has particularly good heat resistance, electrical insulation, and chemical stability. In particular, it relates to an adhesive for producing printed wiring boards that has excellent adhesion to plating films.

[Conventional technology]

BACKGROUND ART In recent years, advances in electronics have been remarkable, and as a result, electronic devices need to be further miniaturized or faster. For this reason, printed wiring boards, especially printed wiring boards mounted with components such as ICs and LSIs, are required to have higher density and higher reliability using fine patterns.

Conventionally, a typical technique for forming a conductor circuit (pattern) on a printed wiring board is a method called an etched foil method, in which copper foil is laminated on a board and then photo-etched. This method has the feature of being able to form a conductor pattern with excellent adhesion to the board, but on the other hand, it has the major drawback that it is difficult to obtain a highly accurate fine pattern by etching because the copper foil is thick. Moreover, there were also problems such as the manufacturing process was complicated and inefficient.

Therefore, recently, in order to form conductor circuits on wiring boards,
The additive method, in which an adhesive containing diene-based synthetic rubber is applied to the surface of a substrate to form an adhesive layer, and the surface of this adhesive layer is roughened, is then subjected to electroless plating to form a conductor circuit pattern has been gaining attention. It's here.

However, since the adhesive used in this known method contains synthetic rubber in its composition, it has drawbacks such as a significant decrease in adhesion strength at high temperatures and blistering of the electroless plating film during soldering. was there. In addition, the heat resistance is low and the electrical properties such as surface resistance are not sufficient, so the range of application is considerably limited.

As a "resin composition for printed wiring boards" used to form conductor patterns by such electroless plating, a composition as disclosed in Japanese Patent Application Laid-open No. 140344/1983 has been proposed. However, this composition
The thermosetting resin component forming the spherical particles in the composition is not etched (treated with an oxidizing agent) and is insoluble in so-called oxidizing agents. The adhesive layer on the substrate obtained by etching and roughening this resin composition has irregularities with a depth of about 20 μm, so it is difficult to obtain a conductor with a fine pattern, and there are gaps between the patterns. Its insulation properties tend to be poor, and its heat resistance and electrical properties are also poor, making it undesirable for mounting components.

[Problem to be solved by the invention]

As explained above, it is an adhesive for electroless plating that has good heat resistance, electrical insulation, and chemical stability, and has excellent adhesion between the substrate and the electroless plating film, and is easy to handle during plating. This is not yet known, and the fact is that no attempt has yet been made to manufacture printed wiring boards using such adhesives.

In response to this, the present inventors have previously conducted various studies to eliminate the above-mentioned drawbacks and proposed the invention disclosed in Japanese Patent Application No. 118898/1982 (Japanese Patent Application Laid-open No. 276875/1982).

However, in the adhesive according to the invention proposed prior to this invention, unless there is a significant difference in solubility in oxidizing agents between the heat-resistant resin fine powder and the matrix heat-resistant resin, the anchor tends to become unclear and the plating The problem remained that the adhesion of the film could not be improved.

The purpose of the present invention is to solve the above-mentioned drawbacks of conventional adhesives for electroless plating and the problems faced by the prior art, and in particular, to provide extremely excellent adhesion between a substrate and an electroless plating film and to be easy to handle. The purpose is to propose an adhesive for electroless plating that is relatively easy to make.

[Means to solve the problem]

Therefore, the present inventors aimed to improve the prior invention proposed by the present inventors prior to this invention, and clarified the shape of the anchor that is effective for improving the adhesion of the electroless plating film. As a result of intensive research to develop adhesives suitable for oxidizing agents, we found that using pseudo-particles made by sprinkling oxidizing agent-insoluble fine powder on the surface of oxidizing agent-soluble base particles could solve the above-mentioned problems. The present inventors have discovered that it is possible to advantageously solve this problem, and have completed the present invention. That is, the present invention is a product that is hardened to be soluble in an oxidizing agent, and has an average particle size of 10. On the surface of heat-resistant resin powder below crm,
Heat-resistant resin fine powder that is hardened to be soluble in oxidizing agents and has an average particle size of 0.8 μm or less, or inorganic fine powder that is soluble in oxidizing agents and has an average particle size of 0.8 μm or less Electroless plating in which anchor-forming pseudo-particles to which at least one of the powders is attached are dispersed in an uncured heat-resistant resin liquid that becomes poorly soluble in oxidizing agents through curing treatment. Suggest adhesive for use.

The heat-resistant resin powder and the fine powder of the same type of resin in the anchor-forming pseudo-particles are preferably bonded together by heating to fuse them together or by using a binder.

[For production]

The adhesive for electroless plating according to the present invention has anchor-forming particles dispersed in an uncured heat-resistant resin liquid that has a property of becoming at least poorly soluble in oxidizing agents by curing treatment, and is dissolved by an oxidizing agent. For pre-cured heat-resistant resin powder (base particles),
It is characterized by using pseudoparticles obtained by further sprinkling various fine powders (adhesive powders) soluble in an oxidizing agent on the surface of the base particles.

That is, the anchor-forming pseudo-particles, which are made by coating the surface of a cured heat-resistant resin powder (base particle) that is soluble in an oxidizing agent with an adhesion powder made of a fine powder that is soluble in an oxidizing agent, are When an adhesive dispersed in a cured heat-resistant resin liquid is used, first, anchor-forming pseudo particles are added to the heat-resistant resin that forms the matrix (hereinafter referred to as "matrix-forming heat-resistant resin"). It is convenient for obtaining an adhesive layer in which particles are uniformly dispersed.
Because there is a difference in solubility to oxidizing agents between the above-mentioned "matrix-forming heat-resistant resin" (both are soluble in oxidizing agents), when the adhesive layer is treated with oxidizing agents, , only the anchor-forming pseudo-particles dispersed on the surface of the adhesive layer are selectively dissolved and removed, and as a result, clear anchors for roughening the surface of the adhesive layer are reliably formed; Third, As shown in FIG. 1, the anchor-forming pseudo-particles are prepared by sprinkling the same type of resin fine powder or inorganic fine powder that is soluble in the oxidizing agent on the surface of the base particle that is soluble in the oxidizing agent. This makes the shape of the formed anchor itself extremely complicated.

Now, in the adhesive of the present invention, the heat-resistant resin constituting the anchor-forming pseudo-particles is formed by curing both the base particles and the adhering powder (the adhering powder may be an inorganic fine powder).

This heat-resistant resin is limited to those that have been cured; if it is not cured, it is added to the heat-resistant resin liquid that forms the matrix or to a solution in which this resin is dissolved using a solvent. This is because this resin is also dissolved in the solution. In other words, when an adhesive containing such uncured resin powder is applied to a substrate and dried and cured, an adhesive is created in which the "matrix-forming heat-resistant resin" and "heat-resistant resin powder and its fine powder" are eutectic. This will form a layer. As a result, during treatment with an oxidizing agent after coating, the adhesive layer is almost uniformly dissolved, making it difficult to selectively dissolve and remove the adhesive layer surface (forming an anchor) necessary for surface roughening.

On the other hand, if these heat-resistant resin powders or fine powders are cured in advance, they will be at least poorly soluble in the heat-resistant resin liquid or the solvent that dissolves this resin, so they will not dissolve. As a result, the heat-resistant resin powder can be "uniformly" dispersed in the matrix-forming heat-resistant resin liquid. In this way, by using an adhesive in which soluble powder or the like is dispersed, it becomes easy to form an anchor with a clear and complex shape as shown in FIG. 2 through the curing process.

Note that methods for curing this resin powder include a method of curing by heating and a method of curing by adding a catalyst, among which a method of curing by heating is the most practical.

Next, as for the heat-resistant resin powder and its fine powder, for example, the heat-resistant resin is heat-cured and then finely pulverized using a jet mill or a freeze-pulverizer, or the heat-resistant resin is The solution is prepared by spray drying. In addition, fine particles obtained by adding an aqueous curing agent to an uncured heat-resistant resin emulsion and stirring are simply heated in a hot air dryer, or various binders are added and mixed and dried, and then a ball mill or It is manufactured by crushing using an ultrasonic dispersion machine or the like, and then classifying it using a wind classifier or the like. When producing base particles and fine powder using the same resin, it is necessary to classify them using a Sedigraph or the like.

The particle shape of the heat-resistant resin powder obtained in this way is
It is not only spherical (it has various complex shapes, so the shape of the anchor formed by this will also be complicated accordingly), which improves the adhesion strength of the plating film such as beer strength and pull strength. It works effectively.

Here, the size of the heat-resistant resin powder serving as the base particles is set to an average particle size of 10 μm or less, more preferably 5 μm or less. The reason is that when the average particle size is larger than 10 μm, the density of the anchors formed by dissolution and removal accompanying the oxidation treatment is low and tends to be non-uniform. As a result, the adhesion strength deteriorates, reducing the reliability of the product.Furthermore, the unevenness of the surface of the adhesive layer becomes more severe than necessary, making it difficult to obtain a fine conductor pattern, which is also inconvenient when mounting components. This is because

On the other hand, the heat-resistant resin fine powder or inorganic fine powder used as the adhering powder has an average particle size of 0.8 μm or less. The reason for this is that if the thickness is larger than 0.8 μm, the anchoring effect will be reduced and the adhesion strength will be poor.

Further, as the heat-resistant resin powder and its fine powder, those having excellent heat resistance and electrical insulation properties and stable properties against chemicals are used. Furthermore, by curing the resin used as the base particles, it becomes poorly soluble in heat-resistant resin liquids or solvents that dissolve this resin, but becomes soluble in oxidizing agents such as chromic acid. use something For example, it is at least one selected from epoxy resins, polyester resins, and bismaleimide-triazine resins. Among these, the epoxy resin has excellent properties and is most suitable. Furthermore, calcium carbonate can be used as the inorganic fine powder that is soluble in the oxidizing agent.

The anchor-forming pseudo-particles of the present invention are formed into a shape as shown in FIG. 1 by sprinkling heat-resistant resin or inorganic fine powder onto base particles of heat-resistant resin powder. In this way, if a base particle is coated with fine powder on its surface, the shape of the anchor formed when the soluble particles are dissolved and removed during oxidation treatment and the adhesion strength of the plating film are It can be made more complex to help improve it.

In other words, a single particle such as the one shown in FIG. The higher the beer strength, the more complex the shape.
Pull strength can be obtained, and therefore adhesion strength and stability of the plating film can be obtained.

The pseudo-particles may be made by simply adhering fine powder to the surface of the base particle using a binder, but the pseudo-particles may also be made by hardening heat-resistant resin powder that is soluble in oxidizing agents ( When the mother particles are still in a somewhat soft state, various types of fine powder may be sprinkled on the mother particles and adhered to the mother particles, thereby hardening them while slightly biting into the surface of the mother particles. These are equally effective anchor-forming pseudoparticles.

In addition, in order to improve bonding with the matrix-forming heat-resistant resin, a semi-cured layer or unreacted functional group is applied to the surface of the heat-resistant resin powder (base particles and attached powder) to the extent that it does not dissolve in the matrix. May be granted.

The properties of the above pseudoparticles obtained in this way are as follows:
It is necessary that the particles be aggregated with such adhesive strength that they will not dissociate during mixing and return to the original fine powder. For this reason, in the present invention, the fine resin powder itself is heated and fused or bonded via a binder to form pseudo particles bonded by adhesive force such as a single particle. Furthermore, the heat-resistant resin particles (pseudo-particles) according to the present invention preferably have a variation of 60 wt % or more within a range of ±2 μm based on the center particle size. The reason why it is limited to those with such variations is that if the variations are larger than the above range, the reliability of the product will decrease.

Next, the matrix-forming heat-resistant resin that disperses and holds the anchor-forming pseudo particles made of the heat-resistant resin powder and the same type of fine powder will be described. This resin is one that is excellent in heat resistance, electrical insulation, chemical stability, and adhesiveness, and has the property of becoming poorly soluble in oxidizing agents when cured. For example, at least one selected from epoxy resins, epoxy-modified polyimide resins, polyimide resins, and phenol resins, and in some cases, photosensitive resins are used. This photosensitive adhesive is suitable as an adhesive for interlayer insulating materials of build-up wiring boards.

As already mentioned, there is a large difference in solubility characteristics with respect to oxidizing agents between the heat-resistant resin powder, which is soluble, and the matrix-forming heat-resistant resin, which becomes poorly soluble through hardening treatment.

Therefore, when the soluble heat-resistant resin powder and fine powder dispersed on the surface of the adhesive layer are dissolved and removed using an oxidizing agent, most of the matrix-forming heat-resistant resin that is poorly soluble in the oxidizing agent is removed. Since the particles remain as a base material without being dissolved, clear anchors are formed on the surface of the adhesive layer by the portions of the pseudo particles that have been dissolved and removed, as shown in FIG.

Even if the same type of heat-resistant resin is used, for example, using an epoxy resin that is easily dissolved in an oxidizing agent as a heat-resistant resin powder,
On the other hand, the same effect can be expected even if an epoxy resin, which is relatively difficult to dissolve in oxidizing agents, is used in combination as the matrix heat-resistant resin.

Furthermore, as the so-called matrix-forming heat-resistant resin liquid used to disperse the anchor-forming pseudo-particles made of the heat-resistant resin powder, a heat-resistant resin liquid that does not contain a solvent can be used as is. A heat-resistant resin liquid prepared by dissolving a heat-resistant resin in a solvent can be used more advantageously because it has a lower viscosity, which makes it easier to uniformly disperse the heat-resistant resin powder, and it is easier to apply the heat-resistant resin powder to a substrate. Note that, as the solvent used for dissolving the heat-resistant resin, for example, methyl ethyl ketone, methyl cellosolve, ethyl cellosolve, butyl calpitol, butyl cellulose, tetralin, dimethylformamide, n-methylpyrrolidone, etc. can be used.

Note that the heat-resistant resin liquid that serves as the matrix contains:
A filler made of inorganic fine powder such as silica, alumina, titanium oxide, and zirconia may be appropriately mixed and used.

The blending amount of the anchor-forming pseudo particles made of heat-resistant resin powder or the like with respect to the matrix-forming heat-resistant resin is within the range of 2 to 350 parts by weight based on 100 parts by weight of the solid content of the matrix-forming heat-resistant resin. The range of 5 to 200 parts by weight is a preferable range because it can further increase the adhesion strength between the substrate and the electroless plated film. That is, if the amount of N-like particles is less than 2 parts by weight, the density of the anchors formed by dissolving and removing them will be low, making it impossible to obtain sufficient adhesion strength between the substrate and the electroless plated film. On the other hand, if the amount exceeds 350 parts by weight, almost the entire adhesive layer will be dissolved and no anchor will be formed.

The adhesive of the present invention can be used for electroless plating in addition to several conventional methods, such as applying electroless plating to a substrate and then etching the circuit, or directly etching the circuit when applying electroless plating. It can also be advantageously applied to methods of forming.

〔Example〕

200 g of epoxy resin powder (manufactured by Toshi Co., Ltd., trade name: Trepar EP-B, average particle size 3.9 pm) was dispersed in 51 acetone, and mixed with a Henschel mixer (
Epoxy resin powder (Mitsui Miike Kakoki, FMIOB type) was mixed with epoxy resin powder (manufactured by Toshi, product name: Trepearl EP-8).
A suspension prepared by dissolving 300 g of epoxy resin (manufactured by Mitsui Petrochemicals, trade name: TA-1800) in acetone at a ratio of 30 g to 11 acetone was prepared using the above-mentioned method. The adhering powder is attached to the surface of the epoxy resin powder (base particles) by dropping it into the epoxy resin powder suspension, and then the acetone is removed, and then heated to 150°C to form an anchor. Created particles. The obtained anchor-forming pseudoparticles had an average particle size of about 4.3 μm, and about 75% by weight existed within a range of ±2 μm around the average particle size.

(2) 60 parts by weight of phenol novolak epoxy resin (manufactured by Yuka Shell, trade name: E-154), bisphenol A epoxy resin (manufactured by Yuka Shell, trade name:
E-1001) 40 parts by weight, 4 parts by weight of imidazole curing agent (manufactured by Shikoku Kasei, trade name IP4MH2), (1) above
The viscosity was adjusted to 120 cps using a homodisper disperser while adding a butyl cellosolve solvent to 50 parts by weight of the anchor-forming pseudo particles prepared above, and then kneaded using a triple roll to obtain an adhesive.

(3) The adhesive obtained in (2) above was applied using a roller coater to a glass polyimide substrate (manufactured by Toshiba Chemical, trade name: Toshiba Durite Laminated Board-EL) to which no copper foil was attached. After that, at 100℃ for 1 hour, and then for another 15 days.
It was dried and cured at 0° C. for 5 hours to form an adhesive layer with a thickness of 20 μm.

(4) The substrate obtained in (3) above was treated with chromic acid (Crz
oz) 500g/Il aqueous solution at 70°C.
The adhesive layer was immersed for 15 minutes to roughen the surface of the adhesive layer, and then immersed in a neutralizing solution (manufactured by Sibley, trade name: PN-950) and washed with water.

(5) Applying a palladium catalyst (manufactured by Sibley, trade name: Cataposit 44) to the substrate with the roughened surface of the adhesive layer obtained in (4) above to activate the surface of the adhesive layer, It was immersed in an electroless copper plating solution for additive method having the composition shown below for 11 hours to form electroless copper plating with a thickness of 25 μm.

Copper sulfate (CuSO, 58zO) Formalin (37%) Sodium hydroxide DTA Additive plating temperature near 0 to 72°C 0.06 mol/1 O630 mol/1 O035 mol/1 0.12 mol/l A little PH: 12 .4 The wiring board produced as described above was further electroplated with copper to a thickness of 35 μm in a copper sulfate plating bath.

Regarding the printed wiring board manufactured in this way, first, the adhesion strength between the board and the copper plating film was measured according to JIS-C-644.
It was measured by method 1. As a result, the beer strength was 1.88
kg/cm. Further, the change in surface resistance of the adhesive layer due to immersion in boiling water at 100° C. for 2 hours was 2×10′3 Ω·am compared to the initial value of 5×10 14 Ω·cm. Further, 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 maintained at 300° C. and heated for 10 minutes, no abnormality was observed.

A printed wiring board was produced basically in the same manner as in Example 1. However, in this example, a printed wiring board was prepared using an adhesive for electroless plating prepared with the formulation shown in Table 1.

The adhesion strength between the substrate and the copper plating film was measured in the same manner as in Example 1, and is shown in Table 1.

〔Effect of the invention〕

As explained above, the adhesive of the present invention has extremely excellent not only heat resistance and electrical properties but also adhesion between the substrate and the electroless plated film. Since a particularly preferable anchor can be formed, the surface roughening necessary to improve the adhesion can be easily performed, and a high-quality printed wiring board can be manufactured.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of the anchor-forming pseudo-particles used in the present invention, and FIG. 2 is a section showing the shape of the anchor formed on the surface of the adhesive layer by using the anchor-forming pseudo-particles in the present invention. FIG. 3 is a cross-sectional view of anchor-forming particles in a conventional example, and FIG. 4 shows the shape of a conventional anchor formed on the surface of an adhesive layer by using the anchor-forming pseudo particles. FIG.

Claims (1)

[Claims] 1. On the surface of a heat-resistant resin powder that has been hardened to be soluble in an oxidizing agent and has an average particle size of 10 μm or less,
Heat-resistant fine resin powder that is hardened to be soluble in oxidizing agents and has an average particle size of 0.8 μm or less, or fine inorganic powder that is soluble in oxidizing agents and has an average particle size of 0.8 μm or less In an uncured heat-resistant resin liquid that becomes poorly soluble in oxidizing agents by curing the anchor-forming pseudo particles to which at least one of the following is attached,
Adhesive for electroless plating made by dispersing. 2. According to claim 1, the heat-resistant resin powder and the heat-resistant resin fine powder in the anchor-forming pseudo particles are bonded by fusing the powder and the fine powder to each other. Adhesives listed. 3. A claim characterized in that the heat-resistant resin powder and the heat-resistant resin fine powder in the anchor-forming pseudo particles are bonded by interposing a binder between the powder and the fine powder. The adhesive according to item 1.