JPH0649851B2 - Adhesive for electroless plating - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an adhesive for electroless plating used for producing a printed wiring board, which has particularly good heat resistance, electrical insulation and chemical stability. The present invention relates to an adhesive for producing a printed wiring board, which has excellent adhesion of a plated film.

[Conventional technology]

In recent years, the progress of electronics has been remarkable, and accordingly, electronic devices are required to be further downsized or speeded up. For this reason, a printed wiring board, in particular, a printed wiring board on which components such as IC and LSI are mounted, is required to have high density and high reliability by fine patterns.

Conventionally, as a technique for forming a conductor circuit (pattern) on a printed wiring board, a method called an etched foil method in which a copper foil is laminated on a substrate and then photo-etched is typical. This method is characterized in that it can form a conductor pattern with excellent adhesion to the substrate, but on the other hand, it has a major drawback that it is difficult to obtain a highly precise fine pattern by etching because the copper foil is thick. In addition, there is a problem that the manufacturing process is complicated and the efficiency is low.

Therefore, recently, in order to form a conductor circuit on a wiring board,
The additive method, in which an adhesive containing diene-based synthetic rubber is applied to the surface of the 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 pattern, is in the spotlight. Came.

However, since the adhesive used under this known method contains a synthetic rubber in the composition, there are drawbacks such as a large decrease in adhesion strength at high temperatures and a swelling 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 that the application range is considerably limited.

As the "resin composition for printed wiring board" used to form such a conductor pattern by electroless plating, there has been proposed one disclosed in JP-A-53-140344. However, this composition is insoluble in a so-called oxidizing agent, in which the thermosetting resin component forming the spherical particles in the composition is not etched (treated with an oxidizing agent). Since the adhesive layer on the substrate obtained by etching and roughening this resin composition has irregularities with a depth of about 20 μm, it is difficult to obtain a conductor having a fine pattern as the conductor formed on this adhesive layer. However, it has a drawback in that it is not preferable for mounting components because the insulating property is likely to be poor and the heat resistance and electric characteristics are poor.

[Problems to be Solved by the Invention]

As described above, an adhesive agent for electroless plating that has good heat resistance, electrical insulation, chemical stability, excellent adhesion between the substrate and the electroless plating film, and is easy to handle during plating. Is not yet known, and the production of a printed wiring board using such an adhesive has not yet been attempted.

On the other hand, the inventors of the present invention have previously conducted various studies in order to eliminate the above-mentioned drawbacks, and disclosed Japanese Patent Application No. 60-11898 (Japanese Patent Application Laid-Open No. 61-276).
No. 875) proposed the invention.

However, the adhesive according to the above-mentioned invention proposed prior to this invention is likely to have an unclear anchor unless the solubility of the heat-resistant resin fine powder and the matrix heat-resistant resin in the oxidizing agent is significantly different. There was a problem to be solved in that the adhesion of the film was not improved.

The object of the present invention is to solve the above-mentioned drawbacks of the conventional electroless plating adhesive and the problems of the prior art, and particularly, the adhesion between the substrate and the electroless plating film is extremely excellent, and the handling is easy. We are proposing an electroless plating adhesive that is relatively easy.

[Means for Solving the Problems]

Therefore, the present inventors aim to improve the above-mentioned prior invention that the present inventors have proposed prior to this invention, and to clarify the shape of the anchor effective for improving the adhesion of the electroless plating film. As a result of diligent research to develop an adhesive suitable for use as a result, the use of pseudo particles formed by sprinkling fine powder insoluble in an oxidizing agent on the surface of mother particles soluble in an oxidizing agent The inventors have found that the above can be advantageously eliminated, and have completed the present invention. That is, the present invention is a curing treatment that is soluble in an oxidant,
And, on the surface of the heat-resistant resin powder having an average particle size of 10 μm or less and larger than the particle size of the adhered powder, the particle size is smaller than the particle size of the resin powder and the average particle size is 0.8 μm or less, and Anchored pseudo particles for adhering at least one of a hardened heat-resistant resin fine powder that is soluble in an oxidizing agent and an inorganic fine powder,
We propose an adhesive for electroless plating, which is dispersed in an uncured heat-resistant resin liquid that becomes difficult to dissolve in an oxidant by a curing treatment.

The heat-resistant resin powder and the fine resin powder of the same kind in the pseudo particles for forming anchors are preferably bonded by heating to fuse each other or using a binder.

[Action]

The adhesive for electroless plating according to the present invention is an anchor-forming particle to be dispersed in an uncured heat-resistant resin liquid having a property of being at least hardly soluble in an oxidant by a curing treatment, and dissolved by the oxidant. For heat-resistant resin powder (base particles) that has been pre-cured,
Pseudo particles obtained by sprinkling various fine powders (adhesive powders) soluble on an oxidant on the surface of the mother particles are used.

That is, the anchor-forming pseudo-particles obtained by coating the surface of the hardened heat-resistant resin powder (mother particles) that is soluble in the oxidizing agent with the adhered powder consisting of the fine powder that is soluble in the oxidizing agent are not added. When an adhesive dispersed in a hardening heat-resistant resin liquid is used, firstly, pseudo particles for forming anchors are added to a heat-resistant resin that forms a matrix (hereinafter, this is referred to as "matrix-forming heat-resistant resin"). It is convenient to obtain an adhesive layer in which the particles are uniformly dispersed. Secondly, the “heat-resistant resin powder and the same kind of resin or inorganic fine powder which is used incidentally (whichever is the main part of the pseudo particle for forming anchor) Is soluble in an oxidizing agent) ”and the“ matox-forming heat-resistant resin ”have different solubilities in an oxidizing agent. Therefore, when the adhesive layer is treated with an oxidizing agent, Only the anchor-forming pseudo-particles dispersed on the surface portion of the adhesive layer are selectively dissolved and removed, and as a result, a clear anchor for the surface roughening of the adhesive layer is surely formed. As shown in the figure, since the surface of the mother particles that are soluble in the oxidizing agent, the pseudo particles for forming an anchor, which are sprinkled with the same kind of resin fine powder or inorganic fine powder that is soluble in the oxidizing agent, are used. The shape of the formed anchor itself is extremely complicated.

In the adhesive of the present invention, the heat-resistant resin forming the pseudo particles for forming anchors is formed by hardening treatment of both the mother particles and the adhered powder (the adhered powder may be an inorganic fine powder). About this heat resistant resin,
Only those that have been subjected to a curing treatment are those that have not been subjected to a curing treatment, and if a heat-resistant resin solution that forms a matrix or a solution obtained by dissolving this resin in a solvent is added, this resin also becomes the solution. This is because they will dissolve together. That is, when an adhesive containing such an uncured resin powder is applied to a substrate and dried and cured, the "matrix-forming heat-resistant resin" and the "heat-resistant resin powder and its fine powder" are bonded together in a eutectic state. Will form a layer. As a result, the adhesive layer is dissolved almost uniformly during the treatment with the oxidizing agent after coating, which makes it difficult to selectively dissolve and remove the adhesive layer surface (formation of anchors) necessary for roughening.

On the other hand, if these heat-resistant resin powders and fine powders are preliminarily hardened, they will dissolve at least because they become difficult for the heat-resistant resin liquid or the solvent that dissolves this resin. As a result, the heat-resistant resin powder can be "uniformly" dispersed in the matrix-forming heat-resistant resin liquid. As described above, the use of the adhesive agent in which the soluble powder or the like is dispersed facilitates the formation of a clear and complicated anchor as shown in FIG. 2 by the curing treatment.

As a method of curing the resin powder, there are a method of curing by heating and a method of curing by adding a catalyst. Among them, the method of curing by heating is practical.

Next, examples of the heat-resistant resin powder and the fine powder thereof include, for example, heat-curing the heat-resistant resin and then pulverizing the heat-resistant resin using a jet mill, a freeze pulverizer, or the like, or the heat-resistant resin before curing treatment. The solution is spray dried to produce. In addition, fine particles obtained by adding an aqueous solution curing agent to an uncured heat-resistant resin emulsion and stirring the mixture are simply heated with a hot air dryer or the like, or various binders are added and mixed and dried, and then a ball mill or It is manufactured by disintegrating with an ultrasonic disperser or the like and further classifying with an air classifier or the like. When the mother particles and the fine powder are produced from the same resin, it is necessary to classify them with a cedigraph or the like.

The particle shape of the heat-resistant resin powder thus obtained is
Since it has various complicated shapes in addition to the spherical shape, the shape of the anchor formed by this also has a complicated shape accordingly, which improves the adhesion strength of the plating film such as peel strength and pull strength. Effectively acts on.

Here, the size of the heat resistant resin powder as the mother particles is larger than the particle size of the adhered powder and has an average particle size of 10 μm.
The size is as follows, and more preferably, the size is 5 μm or less. The reason is that the average particle size is 10
When it is larger than μm, the density of anchors formed by dissolution and removal associated with the oxidation treatment tends to be small and the anchors are likely to be non-uniform. As a result, the adhesion strength deteriorates, the reliability of the product deteriorates, and the irregularities on the surface of the adhesive layer become excessively large, making it difficult to obtain a fine conductor pattern. Moreover, it is inconvenient for mounting components. Is caused.

On the other hand, as the size of the heat resistant resin fine powder or the inorganic fine powder used as the adhesion powder, those having a size smaller than the particle size of the mother particles and having an average particle size of 0.8 μm or less are used. The reason for this is that if it is larger than 0.8 μm, the curing of the anchor is lowered and the adhesion strength is deteriorated.

As the powder of the heat resistant resin and the fine powder thereof, those having excellent heat resistance and electrical insulation and stable to chemicals are used. Of these, the resin used as the mother particles is hardly soluble in the heat resistant resin liquid or the solvent that dissolves the resin by the curing treatment, but becomes soluble in the oxidizing agent such as chromic acid. Use one. For example, at least one selected from an epoxy resin, a polyester resin, and a bismaleimide-triazine resin is at least one. Among them, the epoxy resin is excellent in characteristics and is most suitable. Calcium carbonate can be used as the inorganic fine powder which is soluble in the oxidizing agent.

Now, the pseudo particles for anchor formation of the present invention are formed as shown in FIG. 1 by sprinkling the heat-resistant resin powder mother particles with the heat-resistant resin or inorganic fine powder. If the surface of the mother particles is coated with fine powder, the shape of the anchor formed by the soluble particles being dissolved and removed during the oxidation treatment can improve the adhesion strength of the plating film. Can be more complex to work with.

That is, compared with a general simple particle: that is, an anchor (shown in FIG. 4) formed when a simple spherical particle as shown in FIG. 3 is used, pseudo particles as shown in FIG. , Because the shape becomes more complicated, high beer strength,
Pull strength can be obtained, and thus adhesion strength and stability of the plated film can be obtained.

Further, the pseudo particles may be fine particles to be adhered to the surface of the mother particles only by using a binder, but the hardened heat resistant resin powder ( With respect to the mother particles), when the mother particles are still in a somewhat soft state, by sprinkling and adhering various fine powders to each other, the mother particles may be hardened in a state of being bitten into the surface, These are equally effective pseudo particles for anchor formation.

As the binder, for example, ethyl cellulose, poly (methyl methacrylate) resin, polyvinyl butyral, polyalkylene butyral, phthalic acid ester, polyethylene glycol, etc. can be used. Particularly, as shown in Example 1, acetone, etc. An epoxy resin solution diluted with is preferable because it has excellent heat resistance.

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

The properties of the pseudo particles thus obtained are as follows:
It is necessary that the particles are aggregated with an adhesive force such that they do not dissociate during mixing and return to the original fine powder. For this reason, in the present invention, the resin fine powder itself is heated to be fused or adhered via a binder to form pseudo particles which are bonded by an adhesive force such as a single particle. Further, the heat resistant resin particles (pseudo particles) according to the present invention preferably have a variation such that 60 wt% or more exists within a range of ± 2 μm with reference to the median particle size. The reason why the variation is limited to this is that if the variation is larger than the above range, the reliability of the product is reduced.

Next, the matrix-forming heat-resistant resin on the side where the pseudo particles for forming anchors composed of the above-mentioned heat-resistant resin powder and fine powder of the same kind are dispersed and held will be described. As this resin, a resin having excellent heat resistance, electrical insulation, chemical stability, and adhesiveness is used, and a resin having a property of being softly soluble in an oxidant by a curing treatment 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 in some cases, a resin having photosensitivity is used. The one having this photosensitivity is suitable as an adhesive for an interlayer insulating material of a build-up wiring board.

As described above, the soluble heat-resistant resin powder and the matrix-forming heat-resistant resin, which becomes insoluble by the curing treatment, have a large difference in the dissolution property with respect to the oxidizing agent.
Therefore, when the soluble heat-resistant resin powder and the fine powder dispersed in the surface portion of the adhesive layer are dissolved and removed by using an oxidizing agent, most of the matrix-forming heat-resistant resin that is hardly soluble in the oxidizing agent is obtained. Since it remains as a base material without being dissolved, a clear anchor is formed on the surface of the adhesive layer by the part where the pseudo particles that have been dissolved and removed are removed, as shown in FIG.

Even with the same type of heat resistant resin, for example, an epoxy resin that is easily dissolved in an oxidant is used as the heat resistant resin powder,
On the other hand, a similar curing can be expected by using a combination of an epoxy resin which is relatively insoluble in an oxidizing agent as the matrix heat resistant resin.

The reason is that these epoxy resins can greatly differ in their physical properties by controlling these prepolymers (polymers with a relatively low molecular weight of 300 to 8000), the type of curing agent, and the crosslink density. Because you can. This difference in physical properties is not an exception even with respect to the solubility in an oxidizing agent, and can be adjusted to an arbitrary one by appropriately selecting the type of prepolymer, the type of curing agent, and the crosslinking density.

For example, as an "oxidizer-soluble epoxy resin",
"Alicyclic epoxy is selected as the epoxy prepolymer, a chain aliphatic polyamine curing agent is used as the curing agent, and the molecular weight between cross-linking points (the molecular weight between cross-linking points. The larger the cross-linking density, the lower the cross-linking density is. ) Is about 700 and gently crosslinked "is used.

On the other hand, "an epoxy resin that is sparingly soluble in an oxidizing agent" is one in which bisphenol A type epoxy resin is used as an epoxy prepolymer, dicyandiamide is used as a curing agent, and the molecular weight between crosslinking points is about 500. Or, the solubility is lower than this epoxy resin, "a phenol novolac type epoxy resin as an epoxy prepolymer, an acid anhydride-based curing agent as a curing agent,
, Which has been subjected to high-density crosslinking with a molecular weight between crosslinking points of about 400 ".

Further, the above-mentioned epoxy resin can be used as the “oxidizing agent-soluble epoxy resin”, but in this case, the above-mentioned epoxy resin is the “oxidizing agent-insoluble epoxy resin”.

As described above, the epoxy resin can be adjusted to have an arbitrary solubility by appropriately selecting the type of prepolymer, the type of curing agent, and the crosslink density.
It can be used as a hardened heat-resistant resin fine powder that is soluble in an oxidizing agent, a hardened heat-resistant resin fine powder that is insoluble in an oxidizing agent, and a resin matrix that is hardly soluble in an oxidizing agent.

Further, as can be seen from the above-mentioned examples, being soluble in an oxidant or sparingly soluble (or insoluble) in an oxidant means a relative dissolution rate with respect to the oxidant. As the resin fine powder, those having a difference in solubility may be arbitrarily selected. The means for imparting a difference in solubility to the resin is not limited to adjustment of the type of prepolymer, the type of curing agent, and the crosslink density, and other means may be used.

Then, in the present invention, by utilizing this difference in solubility, each epoxy resin is oxidized for a certain period of time. In this case, the epoxy resin fine powder soluble in the oxidizing agent having the largest solubility difference is violently dissolved, but the matrix is hardly dissolved, so that the concave portion is formed.

In the present invention, heat-resistant resin powder having an average particle diameter of 0.8 μm or less adheres to the surface of the heat-resistant resin powder having an average particle diameter of 10 μm or less, and when this melts, a complicated anchor as shown in FIG. 2 is formed. Is done.

Table 1 shows the types of prepolymers, types of curing agents,
It illustrates the difference in solubility in an oxidizing agent based on the crosslink density.

Further, as the so-called matrix-forming heat-resistant resin liquid used to disperse the pseudo particles for forming anchors composed of the heat-resistant resin powder or the like, a heat-resistant resin liquid containing no solvent can be used as it is, A heat-resistant resin liquid obtained by dissolving a heat-resistant resin in a solvent has a lower viscosity, so that the above-mentioned heat-resistant resin powder can be easily dispersed uniformly and can be easily applied to a substrate, and thus can be advantageously used. As the solvent used for dissolving the heat resistant resin, for example,
Methyl ethyl ketone, methyl cellosolve, ethyl cellosolve, butyl carbitol, butyl cellulose, tetralin, dimethylformamide, normal methylpyrrolidone and the like can be used.

In addition, in the above-mentioned heat-resistant resin liquid serving as the matrix,
A filler made of an inorganic fine powder such as silica, alumina, titanium oxide or zirconia may be appropriately mixed and used.

The compounding amount of the pseudo particles for forming an anchor composed of a heat resistant resin powder or the like with respect to the matrix forming heat resistant resin is 2 with respect to 100 parts by weight of the matrix forming heat resistant resin solid content.
The amount is in the range of to 350 parts by weight, but the range of 5 to 200 parts by weight is particularly preferable because the adhesion strength between the substrate and the electroless plating film can be further increased. That is, when the compounding amount of the pseudo particles 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 plated film cannot be obtained. On the other hand, when the amount is more than 350 parts by weight, the entire adhesive layer is almost dissolved, so that the anchor is not formed.

The adhesive of the present invention can be used for electroless plating in addition to some methods which are in accordance with ordinary methods, for example, a method of etching a circuit after applying electroless plating to a substrate or a direct circuit when performing electroless plating. It can also be advantageously applied to a method of forming a.

〔Example〕

Example 1 (1) Epoxy resin powder (manufactured by Toray, trade name: Trepearl E
200 g of P-B, average particle size 3.9 μm) was dispersed in 5 acetone and Henschel mixer (Mitsui Miike Kakoki, FM
Epoxy resin powder (Toray,
Trade name: Trepearl EP-B, average particle size 0.5 μm) 300 g and epoxy resin (trade name: TA-1800 manufactured by Mitsui Petrochemical Co., Ltd.) were dispersed in acetone dissolved at a ratio of 30 g per 1 acetone. The suspension is dropped into the epoxy resin powder suspension to adhere the adhered powder to the surface of the epoxy resin powder (mother particles), the acetone is removed, and then the mixture is heated to 150 ° C. To prepare particles for forming an anchor. The obtained pseudo particles for forming an anchor had an average particle size of about 4.3 μm, and about 75% by weight was present within a range of ± 2 μm centering on the average particle size.

(2) Phenolic novolac type epoxy resin, (Oilized shell, product name: E-154) 60 parts by weight, bisphenol A type epoxy resin, (Oilized shell, product name: E-100
1) Add butylcellosolve solvent to 40 parts by weight, 4 parts by weight of imidazole curing agent (manufactured by Shikoku Kasei, trade name: 2P4MHZ), and 50 parts by weight of pseudo particles for anchor formation prepared in (1) above. On the other hand, the viscosity was adjusted to 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 laminate-E manufactured by Toshiba Chemical Co., Ltd.) on which the copper foil is not adhered using a roller coater, using the adhesive obtained in (2) above.
L) and then at 100 ° C for 1 hour, then at 150 ° C for 5 hours.
It was dried and cured for an hour to form an adhesive layer having a thickness of 20 μm.

(4) The substrate obtained in (3) above, chromic acid (Cr ₂ O ₃ ) 500g
/ After immersing in an oxidizing agent consisting of an aqueous solution at 70 ° C for 15 minutes to roughen the surface of the adhesive layer, it was immersed in a neutralizing solution (manufactured by Shipley, trade name: PN-950) and washed with water.

(5) The surface of the adhesive layer obtained in (4) above is roughened, and a palladium catalyst (manufactured by Shipley, trade name: Cataposit 44) is applied 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 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 / sodium hydroxide 0.35 mol / EDTA 0.12 mol / additive Some Plating temperature: 70~72 ℃ pH: 12.4 prepared as described above The resulting wiring board was further electroplated with copper in a copper sulfate plating bath to a thickness of 35 μm.

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 1.88 kg / cm. The change in the surface resistance of the adhesive layer after immersion in boiling water at 100 ° C. for 2 hours was 2 × 10 ¹³ Ω · cm with respect to the initial value of 5 × 10 ¹⁴ Ω · cm. In addition, set the surface temperature to 3
When a heat resistance test was conducted in which the surface of the wiring board was brought into close contact with a hot plate kept at 00 ° C and heating was performed for 10 minutes, no abnormality was found.

Example 2 A printed wiring board was manufactured basically in the same manner as in Example 1. However, in this example, a printed wiring board was prepared using the adhesive for electroless plating prepared with the composition shown in Table 2.

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

[Advantages of the Invention] As described above, the adhesive of the present invention has not only excellent heat resistance and electrical characteristics but also excellent adhesion between the substrate and the electroless plated film. Since a particularly preferable anchor can be formed, the surface roughening necessary for improving the adhesion can be easily performed, and a high quality printed wiring board can be manufactured.

[Brief description of drawings]

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

Claims (3)

[Claims] 1. A heat-resistant resin powder which is soluble in an oxidizing agent and has a mean particle size of 10 μm or less and which is larger than the particle size of the adhered powder. Is also small and has an average particle size of 0.8 μm or less and is adhered with at least one of a hardened heat-resistant resin fine powder that is soluble in an oxidant and an inorganic fine powder. An adhesive for electroless plating, in which pseudo particles for forming an anchor are dispersed in an uncured heat-resistant resin liquid that becomes difficult to dissolve in an oxidant by a curing treatment. 2. The bonding of the heat-resistant resin powder and the heat-resistant resin fine powder in the pseudo particles for forming anchors is performed by fusing the powder and the fine powder to each other. Item 2. The adhesive according to Item 1. 3. The heat-resistant resin powder and the fine powder of the heat-resistant resin in the pseudo particles for forming anchors are bonded by interposing a binder between the powder and the fine powder. The adhesive agent according to claim 1.