JPH09223859A - Printed wiring board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a printed wiring board excellent in adhesion to a resin insulating layer for a conductor formed by the additive method and in heat cycle characteristics by improving the adhesion between a primary plating layer and a secondary plating layer comprising the conductor. SOLUTION: A conductor circuit 2 as the first layer, composed of a plurality of conductor patterns, is formed on the surface of a substrate 1, and light- sensitive adhesive solution is applied to the surface of the conductor circuit 2. The conductor circuit 20 is left for 20 minutes, and then dried at 60 deg.C to form openings 4, 100μm in diameter, to be via holes on the wiring board. Further, heat treatment is performed to form a resin insulating layer 3 having the opening 4 excellent in dimensional accuracy. Prebaking, exposure, development and curing are performed to form plating resist 5. An electroless Cu-Ni-P alloy layer 6 is formed in the areas with no resist formed, and an electroless copper plating layer 7 is formed on the surface of a copper-nickel plating thin film, the primary plating film. This improves the adhesion between the primary plating layer and the secondary plating layer comprising the conductor, and makes it possible to form a printed wiring board, excellent in adhesion between conductor and resin insulating layer, with stability.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a printed wiring board having improved adhesion between a conductor formed by an additive method and a resin insulating layer, and more particularly, adhesion between a primary plating layer and a secondary plating layer forming the conductor. Is a proposal of.

[0002]

2. Description of the Related Art In recent years, with the progress of the electronic industry, electronic devices have been reduced in size and increased in speed. For this reason, a printed circuit board and a wiring board on which an LSI is mounted have a high density and a fine pattern. High reliability is required.

For this reason, recently, as a method of forming a conductor on a wiring board, an adhesive is applied to the surface of the substrate to form a resin insulating layer, and the surface of the resin insulating layer is roughened, and then electroless. Attention has been paid to the additive method of forming a conductor by plating.

In such an additive method, as a means for improving the adhesion between the conductor and the resin insulation layer (hereinafter referred to as "peel strength"), chemical etching is conventionally performed on the conductor formation surface side of the resin insulation layer. There is known a method of providing fine irregularities by According to this method, since the unevenness provided on the surface of the resin insulating layer is filled with the plating metal such as copper plating, the peeling strength can be improved by the anchor effect due to the unevenness. The improvement of the peel strength due to the anchor effect is generally performed by increasing the breaking area and the strength of the conductor metal or the insulating layer resin.

However, in a recent additive type printed wiring board which requires a wiring with higher density and higher pattern accuracy, the resin insulating layer is formed by surface roughening in order to accurately form a fine pattern of a resist. It is necessary to make the anchor small. Therefore, in the above-mentioned conventional technique, when the anchor is made smaller, the fracture area becomes smaller, resulting in a problem that the peel strength is significantly reduced.

[0006] In order to solve this problem, the present inventors previously performed thin electroless alloy plating (primary plating) treatment by providing catalyst nuclei on the roughened surface of the resin insulating layer provided on the substrate. We have proposed a printed wiring board that is directly applied, and then the surface of the alloy plating layer is subjected to thick electroless copper plating (secondary plating) to form a conductor layer. Particularly in this proposal, it is desirable to use a copper-nickel alloy having a low conduction resistance and excellent hardness as the primary plating metal filled in the anchor. Therefore, according to the technique of the above proposal,
Even in a wiring having a higher density and a higher pattern accuracy, the peel strength can be improved to some extent while keeping the conduction resistance low.

[0007]

However, when the copper-nickel alloy is used as the primary plating metal and copper is used as the secondary plating metal as described above, the primary plating layer is oxidized because it contains nickel. Cheap. As a result, for example, when the primary plating layer is exposed to the air for a long time due to manufacturing trouble or the like, the surface of the primary plating layer is oxidized, and the primary plating layer (copper-nickel alloy layer) and the secondary plating layer (copper plating). There was a problem that poor adhesion of the layer) occurred.

[0008] In addition, such poor adhesion causes the anchor formed on the resin insulating layer to become smaller as the wiring pattern becomes higher in density even if the surface oxidation of the primary plating layer does not occur, as shown in FIG. In addition, when the primary plating layer formed on the roughened surface side including the anchor recess is completely filled with the primary plating metal in the anchor recess and is evenly coated.

As described above, when the adhesion between the primary plating layer and the secondary plating layer forming the conductor is deteriorated, the adhesion (peel strength) between the conductor formed by the additive method and the resin insulating layer is deteriorated. . Further, such a conductor composed of two layers, a primary plating layer and a secondary plating layer, may have peeling due to a heat cycle or the like because the layers have different thermal expansion coefficients.

An object of the present invention is to solve the above problems of the prior art, and in particular, by improving the adhesion between the primary plating layer and the secondary plating layer forming the conductor, a higher density is achieved. It is an object of the present invention to provide a printed wiring board having excellent adhesion (peel strength) of a conductor formed by the additive method to a resin insulating layer and excellent heat cycle characteristics even in wiring having high pattern accuracy.

[0011]

Means for Solving the Problems The inventor of the present invention has intensively studied for realizing the above-mentioned object, and as a result, has completed the invention having the following contents as the gist. That is, the present invention is a printed wiring board having a conductor circuit formed by a primary plating process and a secondary plating process on a roughened surface of a resin insulating layer provided on a substrate, wherein the conductor circuit includes an anchor dent. The roughened surface side is composed of a primary plating layer provided along the roughened surface, and the surface of the primary plating layer is filled with a secondary plating layer so as to occupy at least part of the anchor recess. The printed wiring board is characterized in that it is formed in an open state.

Here, the primary plating layer has a film thickness of 1 or more and less than 2 μm, a ratio in the anchor recess of 30 to 50 vol%, or of Ni, Co, Cu, Au and Ag. It is desirable to be composed of at least two kinds of alloys. The primary plating layer is preferably made of an alloy of at least one kind of Ni, Co, Cu, Au and Ag and at least one kind of Sn, Pb, B, P, C and a transition metal.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION In a printed wiring board according to the present invention, a conductor circuit is composed of a primary plating layer having a roughened surface side including anchor recesses provided along the roughened surface, and the surface of the primary plated layer. Is characterized in that the secondary plating layer is formed so as to be filled so as to occupy at least a part of the anchor recess. This increases the contact area between the primary plating layer and the secondary plating layer. Moreover, since the interior of the anchor recess is not completely filled with the primary plating layer, a physical bonding force due to the anchor effect is applied between the primary plating layer and the secondary plating layer in addition to the chemical bond. As a result, the adhesion between the primary plating layer and the secondary plating layer forming the conductor can be improved, and even in wiring with higher density and higher pattern accuracy, the adhesion (peel) of the conductor formed by the additive method to the resin insulation layer can be improved. It is possible to provide a printed wiring board having improved strength.

Such an effect becomes more remarkable when the thickness of the primary plating layer is 1 μm or more and less than 2 μm and the proportion of the primary plating layer in the anchor recess is 30 to 50 vol%.

The reason why the thickness of the primary plating layer is set to 1 μm or more and less than 2 μm is to suppress the variation in quality of each product, eliminate the pinholes in the plating film, and prevent the resistance value from increasing. is there. That is, when the thickness is less than 1 μm, the composition of the deposited plating film varies, and the peel strength varies from product to product. Further, pinholes are likely to occur in the primary plating film, the secondary plating solution does not come into sufficient contact, and voids are created in the plating layer. These voids also expanded upon thermal shock and caused cracks. This point, 1
When the thickness exceeds μm, such pinholes disappear and the composition of the deposited plating film becomes stable. However, if it exceeds 2 μm, the resistance value becomes large, which is not preferable as a conductor circuit. Therefore, in the present invention, the thickness of the primary plating layer is limited to the range of 1 μm or more and less than 2 μm.

The reason why the proportion of the primary plating layer in the anchor recess is 30 to 50 vol% is to improve the peel strength and to secure the adhesion to the upper secondary plating film. That is, if it is less than 30 vol%, the peel strength is not sufficiently improved, while if it exceeds 50 vol%, the surface of the primary plating film is smoothed and the anchor effect cannot be achieved. Adhesiveness with the secondary plating formed cannot be secured sufficiently. Therefore, the ratio of the primary plating layer in the anchor recess is 30 to 50 vol.
%.

In the present invention, the metal of the primary plating layer that constitutes the conductor of the printed wiring board may be a combination of metals that form an alloy. In particular, from the viewpoint of maintaining low conduction resistance, Ni, Co , Cu, Au, and Ag are essential components.

In the printed wiring board of the present invention, it is preferable that the conductor metal is capable of electrolytic plating or electroless plating because wiring having higher density and higher pattern accuracy is provided. Ni, Co, Cu, Au
And Ag, and Sn, Pb, B, P, C and transition metals are used.

Among them, the Cu-Ni-P alloy plating is preferable because it is excellent in strength and resistance characteristics, and in the plating bath, there is little abnormal precipitation and the stability of the plating bath is excellent. The Cu source may be any water-soluble Cu source, but CuSO ₄ , CuCl ₂ , copper acetate, and Cu (NO ₃ ) ₂ are preferable. The supply source of Ni may be a water-soluble source, but is preferably NiSO ₄ , NiCl ₂ , nickel acetate, Ni (N
O ₃ ) ₂ .

In the present invention, the adhesive for electroless plating forming the resin insulating layer of the printed wiring board is a heat-resistant resin soluble in an acid or an oxidant in a heat-resistant resin liquid that is hardly soluble in the acid or the oxidant. It is most suitable that the particles are dispersed. This is because by roughening and removing the heat-resistant resin particles soluble in an acid or an oxidizing agent, an octopus-shaped anchor can be formed on the surface and the adhesion to the conductor circuit can be improved. Further, since the primary plating film traces this roughened surface, the adhesion with the secondary plating film can be improved at the same time.

Here, the heat-resistant resin which is hardly soluble in an acid or an oxidant is preferably a photosensitized thermosetting resin or a composite of a photosensitized thermosetting resin and a thermoplastic resin. By photosensitization, the opening for via hole formation
This is because it can be easily formed by exposure and development. In addition, by compounding with a thermoplastic resin, the toughness can be improved, the peel strength of the conductor circuit can be improved, and the generation of cracks in the via hole portion due to heat cycle can be prevented. Specifically, an epoxy acrylate obtained by reacting an epoxy resin with acrylic acid, methacrylic acid, or the like, or a composite of epoxy acrylate and polyether sulfone is preferable. In particular, epoxy acrylate is
It is desirable that 20 to 80% of all epoxy groups have reacted with acrylic acid or methacrylic acid.

The heat resistant resin particles include: Heat resistant resin powder having an average particle size of 10 μm or less ,. Average particle size is 2μ
Agglomerated particles obtained by aggregating a heat-resistant resin powder having a particle diameter of m or less to have an average particle size three times or more the size of the powder. Average particle size
A mixture of a heat-resistant resin powder having a particle diameter of 10 μm or less and a heat-resistant resin powder having an average particle diameter of 1/5 or less and 2 μm or less of the powder, It is preferable that the heat-resistant resin powder having an average particle diameter of 2 μm to 10 μm is selected from pseudo particles formed by adhering at least one of the heat-resistant resin powder having an average particle diameter of 2 μm or less and the inorganic powder on the surface of the heat-resistant resin powder. . These are because they can form complex anchors. L / S = 50/50
In order to obtain a fine pattern of (μm) or less, the depth of the anchor recess formed in the resin insulating layer needs to be 15 μm or less. In particular, the alloy plating layer (primary plating layer) according to the present invention is It is effective for obtaining a high peel strength (adhesion) even with such a shallow anchor. Epoxy resin, amino resin (melamine resin, urea resin, guanamine resin) or the like can be used as the resin constituting such heat-resistant resin particles. Among these, the epoxy resin can arbitrarily change the solubility in an acid or an oxidizing agent by changing the kind of the oligomer, the kind of the curing agent, and the crosslinking density. For example, a bisphenol A-type epoxy resin oligomer cured with an amine-based curing agent is easily dissolved in an oxidizing agent. On the other hand, a novolac epoxy resin oligomer cured with an imidazole-based curing agent is difficult to dissolve in an oxidizing agent.

In the present invention, as the acid that can be used for the roughening treatment, there are phosphoric acid, hydrochloric acid, sulfuric acid, organic acids (formic acid, acetic acid, etc.), and the organic acid is preferable. The reason for this is that the metal conductor layer exposed from the via hole is unlikely to corrode when the roughening treatment is performed. As the oxidizing agent, chromic acid, permanganate (potassium permanganate, etc.) and the like are desirable. In particular, when the amino resin particles are dissolved and removed, it is desirable to carry out a roughening treatment alternately with an acid and an oxidizing agent.

In the present invention, when a multilayer wiring board is formed, the resin insulation layer as described above may be composed of a plurality of layers. For example, in the case of using a plurality of layers, there are the following modes. (1) The side close to the substrate is a heat-resistant resin layer that is hardly soluble in an acid or an oxidizing agent, and the upper layer is a heat-resistant resin particle that is soluble in an acid or an oxidizing agent in a heat-resistant resin that is hardly soluble in an acid or an oxidizing agent. And an adhesive layer for electroless plating in which
A two-layer resin insulation layer. With this configuration, even if the electroless plating adhesive is roughened, it is not roughened too much and short-circuiting between layers does not occur.

(2) A filling resin material is embedded between the conductor circuits formed on the substrate so that the surface of the filling resin material and the conductor circuit are flush with each other. Conductive resin layer is formed, and further thereon, an adhesive for electroless plating is formed in which heat-resistant resin particles soluble in an acid or an oxidizing agent are dispersed in a heat-resistant resin that is hardly soluble in an acid or an oxidizing agent. Three-layer resin insulation layer. In this structure, since the filling resin material is filled between the conductor circuits on the substrate side, the surface of the substrate becomes smooth and there is no development failure caused by variation in thickness. In addition, by including inorganic particles such as silica in the filler resin material, curing shrinkage can be reduced and the substrate warpage can be prevented. As the filling resin material, a solventless resin is desirable, and a solventless epoxy resin is particularly suitable. If a solvent is used, the residual solvent will evaporate when heated, causing delamination.

Next, an example of a method for manufacturing the printed wiring board of the present invention will be described. (1) First, an adhesive layer is formed on a substrate surface such as a glass epoxy substrate, a polyimide substrate, a ceramic substrate, or a metal substrate by a conventional method, and then the above-mentioned adhesion is performed by using an acid or an oxidizing agent according to a conventional method. The surface of the agent layer is roughened, and then a catalyst is applied to fix the surface of the roughened adhesive layer. When the copper clad laminate is etched to form a copper pattern, a solventless insulating resin (epoxy resin or polyimide resin) is applied, and after curing, polishing is performed to expose the copper pattern and the substrate It is desirable to smooth it. This is because when the substrate is smoothed, the photosensitive insulating layer formed thereon has a uniform thickness, which facilitates exposure and development.

(2) Next, after activating the catalyst by acid treatment, electroless alloy plating (primary plating) is applied to the roughened surface side including at least the anchor depressions, and further ordinary plating (secondary plating) Then, a conductor pattern is formed to obtain a desired printed wiring board. Desirably, the film thickness is 1 μm along the roughened uneven surface of the resin insulation layer provided on the substrate.
More than 2 μm or more, or 30 to 50 vol in the anchor recess
The primary plating layer is provided in such a state that the copper alloy is an alloy such as a copper-nickel alloy, and then secondary plating by ordinary plating is performed on the primary plating layer to form a conductor pattern.

Here, the conductor circuit forming the above-mentioned printed wiring board can be formed by various methods which have been carried out for known printed wiring boards. For example, a method of forming a conductive circuit by plating after forming a plating resist printed in a predetermined pattern, a method of etching a circuit after performing electroless plating on a substrate, or a method of directly forming a circuit when performing electroless plating The method etc. which do can be applied. Among these, in the method of forming a conductor circuit using a plating resist, first, after roughening the surface of the resin insulation layer provided on the substrate, before forming the plating resist, a catalyst nucleus for primary plating is applied. To do. Then, primary plating is applied to the portion where the plating resist is not formed. Then, by the secondary plating, not only the copper pattern but also the via hole is formed.

When manufacturing a multilayer wiring board, the surface of the conductor circuit as the lower layer is roughened. As this roughening treatment, oxidation-reduction treatment (blackening reduction treatment) and roughening treatment by plating treatment are desirable, and copper-nickel-phosphorus alloy plating is most suitable. Since this alloy plating forms a roughened surface of needle-like crystals, it has excellent adhesion to the insulating resin, and
This is because it has electrical conductivity and therefore does not need to be removed even when forming a via hole.

As the plating resist, a commercially available product may be used, but preferably, a composition comprising an epoxy acrylate obtained by reacting an epoxy resin with acrylic acid or methacrylic acid and an imidazole curing agent, or an epoxy acrylate. A composition consisting of polyether sulfone and an imidazole curing agent is suitable. In the above composition, the ratio of epoxy acrylate and polyether sulfone is preferably about 50/50 to 80/20. This is because if the amount of epoxy acrylate is too large, the flexibility is lowered, and if it is too small, the photosensitivity, base resistance, acid resistance and acid resistance are lowered. The epoxy acrylate is preferably one in which 20 to 80% of all epoxy groups have reacted with acrylic acid or methacrylic acid. This is because if the degree of acrylate is too high, the hydrophilicity due to the OH group increases and the hygroscopicity increases, and if the degree of acrylate is too low, the resolution decreases. As the epoxy resin as the basic skeleton resin, a novolak type epoxy resin is desirable. This is because the crosslinking density is high, the water absorption of the cured product can be adjusted to 0.1% or less, and the base resistance is excellent. Examples of novolac type epoxy resins include cresol novolac type and phenol novolac type. To develop plating resists consisting of acrylate and methacrylate of novalac type epoxy resin and imidazole curing agent, diethylene glycol dimethyl ether (DMDG), triethylene glycol dimethyl ether (DMTG), diethylene glycol dibutyl ether (DB
It is desirable to use a developer consisting of a glycol solvent such as DG) and water. This is because there is no development residue. For example, there is a trade name SN-OX-4844 manufactured by San Nopco. The mixing ratio of glycol solvent and water is 8: 2-9.
5: 0.5 is good.

Noble metal ions or colloids are desirable as the catalyst nuclei, and palladium chloride or palladium colloid is generally used. In addition, it is desirable to perform heat treatment to fix the catalyst nucleus.

The treatment liquid for the above primary plating is at least 2 selected from copper, nickel, cobalt and phosphorus.
It is desirable to use an electroless plating solution containing one or more kinds of metal ions. The reason is that the alloy formed by the electroless plating solution containing these metal ions has excellent strength and is advantageous for improving the peel strength. As the copper ion source, the nickel ion source, and the cobalt ion source, compounds such as copper sulfate, nickel chloride, and cobalt chloride that release copper ions, nickel ions, and cobalt ions upon dissolution are used. Such an electroless plating solution requires at least a complexing agent, a reducing agent and a pH adjusting agent. Of these, the complexing agent is preferably a hydroxycarboxylic acid that forms a stable complex with copper ions, nickel ions and cobalt ions under basic conditions. Examples of the hydroxycarboxylic acid include citric acid, malic acid and tartaric acid. The concentration of such hydroxycarboxylic acid is preferably 0.1 to 0.8M. If the concentration of hydroxycarboxylic acid is less than 0.1 M, a sufficient amount of complex is not formed and abnormal deposition or decomposition of the plating solution occurs. On the other hand, if it exceeds 0.8 M, problems such as a slow deposition rate and a large amount of hydrogen generation may occur. As a reducing agent for reducing metal ions to metal elements, it is desirable to use at least one selected from aldehydes, hypophosphites (called phosphinates), borohydrides and hydrazines. This is because these reducing agents are water-soluble and have excellent reducing power. Hypophosphite, which can deposit nickel, is particularly preferable. As the pH adjuster, at least one basic compound selected from sodium hydroxide, potassium hydroxide and calcium hydroxide is preferable. This is because hydroxycarboxylic acid forms a complex with nickel ions or the like under basic conditions. It is desirable that the electroless plating solution contains bipyridyl. The reason for this is that bipyridyl can suppress the generation of metal oxides in the plating bath and suppress the generation of nodules in the conductor (plating film).

By the primary plating using the electroless plating solution as described above, the followability of the adhesive for electroless plating to the roughened surface is excellent, and a primary plating film is formed by tracing the shape of the roughened surface as it is. To be done. As a result, the primary plating film has an anchor as well as the roughened surface, and therefore the secondary plating film formed on this primary plating film secures the adhesion to the primary plating film by the action of the anchor. Is done. That is, the primary plating film is preferably a deposition film of the above-mentioned plating solution having high strength in order to control the peel strength, while the secondary plating film has higher electric conductivity than the composite plating, as described below. A simple copper plating film with a high deposition rate is desirable.

The treatment solution for the secondary plating is an electroless copper plating solution, especially an electroless plating solution comprising copper ions, trialkanolamine, a reducing agent and a pH adjusting agent, and the concentration of copper ions is 0.005 to 0.015. mol / l, reducing agent concentration 0.01-0.04 mol / l, pH adjuster concentration 0.
It is desirable to use an electroless copper plating solution characterized in that it is 25 to 0.35 mol / l. This electroless plating solution
This is because the bath is stable and there is little generation of nodules. In the electroless copper plating solution, the trialkanolamine concentration is preferably 0.1 to 0.8M.
This is because the plating precipitation reaction most easily proceeds in this range. Such trialkanolamine is preferably at least one selected from triethanolamine, triisopropanolamine, trimethanolamine and tripropanolamine. Because it is water-soluble. As the reducing agent, aldehyde, hypophosphite,
At least one selected from borohydride salts and hydrazine is desirable. This is because it is water-soluble and has a reducing power under basic conditions. As a pH adjuster,
At least one selected from sodium hydroxide, potassium hydroxide and calcium hydroxide is desirable.

[0035]

【Example】

(Example 1) (1) A photosensitive dry film is laminated on the surface of a glass-epoxy copper-clad laminate, exposed to ultraviolet light through a mask film on which a desired conductor circuit pattern is drawn, and an image is printed, 1,1,1- Development was performed with trichloroethane to form an etching resist. Then, after removing the copper in the non-conductive portion using a cupric chloride etching solution, the resist was peeled off with methylene chloride. As a result, the first-layer conductor circuit 2 having a plurality of conductor patterns was formed on the surface of the substrate 1 (see FIG. 2 (a)). (2) 70 parts by weight of a 25% acrylate of a cresol novolac type epoxy resin (manufactured by Nippon Kayaku: molecular weight 2500) dissolved in diethylene glycol dimethyl ether (DMDG), 30 parts by weight of polyether sulfone (PES), an imidazole curing agent ( Shikoku Kasei, trade name: 2E4MZ-CN) 4 parts by weight, caprolactone modified tris (acryloxyethyl) isocyanurate (a product of Toa Gosei, a photosensitive monomer)
Trade name: Aronix M325) 10 parts by weight, benzophenone (manufactured by Kanto Kagaku) as a photoinitiator, 5 parts by weight of Michler's ketone (manufactured by Kanto Kagaku) as a photosensitizer, and epoxy to a mixture thereof. A total of 40 parts by weight of 20 parts by weight of resin particles having an average particle size of 5 μm and 20 parts by weight of particles having an average particle size of 0.5 μm were mixed. Then, while adding an appropriate amount of NMP to this mixture, the mixture was stirred with a homodisper stirrer to adjust the viscosity to 2000 cps, and subsequently kneaded with three rolls to obtain a photosensitive adhesive solution. (3) This photosensitive adhesive solution was applied on the surface of the conductor circuit 2 formed in (1) above using a roll coater, left standing for 20 minutes in a horizontal state, and then dried at 60 ° C. (See FIG. 2 (b)). (4) A photomask film having a 100 μmφ black circle printed thereon was brought into close contact with the substrate subjected to the treatment of (3), and exposed at 500 mJ / cm ² by an ultra-high pressure mercury lamp. This is spray-developed with DMDG solution to give 100 μm on the wiring board.
An opening 4 was formed to serve as a mφ via hole. further,
The wiring board was exposed at about 3000 mJ / cm ² with an ultra-high pressure mercury lamp, and heat-treated at 100 ° C. for 1 hour, and then at 150 ° C. for 5 hours to obtain an opening 4 having excellent dimensional accuracy equivalent to a photomask film. A resin insulating layer 3 having a thickness of 60 μm was formed (see FIG. 2 (c)). (5) The surface of the resin insulation layer 3 formed in (4) above is adjusted to pH = 13.
Adjusted to potassium permanganate (KMnO ₄ , 60g / l (0.38
mol / l)) (chromic acid may be used) at 70 ° C. for 15 minutes to roughen the surface of the resin insulating layer 3 and form a roughened surface having fine anchors on the surface. The depth of the roughened surface at this time was 8 to 10 μm as a result of observing and measuring the cross-cut resin insulating layer 3 with an optical microscope. Then, it was immersed in a neutralizing solution (made by Shipley) and washed with water (see FIG. 2 (d)). (6) After the catalyst nuclei necessary for the deposition of the electroless plated metal are applied to the surface of the resin insulating layer 3 whose surface is roughened, a photosensitive resist is further applied to a thickness of 30 μm, prebaked, exposed,
Development and curing were performed to form a plating resist 5. (7) Replace the substrate on which the plating resist 5 was formed in (6) above with 10
% H ₂ SO ₄ solution to activate the catalyst nuclei, and then dipped in an electroless alloy plating solution (primary plating solution) having the composition shown in Table 1 for 50 minutes to form a plating film thickness An electroless Cu-Ni-P alloy layer 6 having a thickness of 1.5 μm was formed on the resist non-forming portion (see FIG. 2 (e)). (8) After performing the primary plating in (7) above, the substrate is shown in Table 2.
The electroless copper plating solution (secondary plating) with a thickness of 11 μm is formed by immersing in the electroless copper plating solution for secondary plating (EDTA-based copper electroless plating solution) of the composition shown in 2 hours and 40 minutes. ,
A printed wiring board having a via hole and a copper pattern was obtained. In this secondary plating, an electroless copper plating layer 7 having a thickness of 11 μm was formed on the surface of the copper-nickel plating thin film which is the primary plating film (see FIG. 2 (g)). (9) The adhesion strength (peel strength) of the plating film applied in (7) and (8) above was measured by an autograph. As a result, the table
As shown in 10, it was 1.42 kg / cm 2. Further, when a heat cycle test was conducted, the number of heat cycles at which peeling occurred at the interface between the primary plating film and the secondary plating film was 1500 cycles.

[0036]

[Table 1]

[0037]

[Table 2]

Example 2 An electroless Co-WP alloy plating (primary plating) having a plating film thickness of 1.5 μm was performed by immersing in an electroless alloy plating solution having a composition shown in Table 3 for 1 hour. Except for the above, the peel strength measurement and the heat cycle test were performed in the same manner as in Example 1. As a result, the peel strength was 2.0 kg / cm, as shown in Table 10. The number of heat cycles at which peeling occurred at the interface between the primary plating film and the secondary plating film was 1500 cycles.

[0039]

[Table 3]

Example 3 An electrolytic Cu solution having a plating film thickness of 1.3 μm was prepared by immersing the electrolytic plating solution having the composition shown in Table 4 for 10 minutes.
A peel strength measurement and a heat cycle test were performed in the same manner as in Example 4 except that the -Co-Ni plating (primary plating) was performed. As a result, the peel strength is
As shown in 10, it was 1.8 kg / cm. The number of heat cycles at which peeling occurred at the interface between the primary plating film and the secondary plating film was 1500 cycles.

[0041]

[Table 4]

(Example 4) Other than that the electroless Cu-Ni-B plating (primary plating) having a plating film thickness of 1.5 μm was applied by immersing in an electroless plating solution having the composition shown in Table 5 for 1 hour. In the same manner as in Example 2, the peel strength measurement and the heat cycle test were performed. As a result, the peel strength was 2.4 kg / cm, as shown in Table 10. The number of heat cycles at which peeling occurred at the interface between the primary plating film and the secondary plating film was 1500 cycles.

[0043]

[Table 5]

Example 5 An electroless Cu-Ni-BC plating (primary plating) having a plating film thickness of 1.8 μm was applied by immersing the electroless plating solution having the composition shown in Table 6 for 1 hour. Except for the above, the peel strength measurement and the heat cycle test were performed in the same manner as in Example 2. As a result, the peel strength was 2.2 kg / cm, as shown in Table 10. The number of heat cycles at which peeling occurred at the interface between the primary plating film and the secondary plating film was 1500 cycles.

[0045]

[Table 6]

Example 6 Electrolytic Ag having a plating film thickness of 1.8 μm was immersed in an electrolytic plating solution having the composition shown in Table 7 for 15 minutes.
A peel strength measurement and a heat cycle test were performed in the same manner as in Example 2 except that the Sn plating (primary plating) was performed. As a result, the peel strength was 1.7 kg / cm, as shown in Table 10. The number of heat cycles at which peeling occurred at the interface between the primary plating film and the secondary plating film was 1400 cycles.

[0047]

[Table 7]

Example 7 Electrolytic Au having a plating film thickness of 1.8 μm was immersed in an electrolytic plating solution having the composition shown in Table 8 for 15 minutes.
A peel strength measurement and a heat cycle test were performed in the same manner as in Example 4 except that the -Pb plating (primary plating) was performed. As a result, the peel strength was 1.7 kg / cm, as shown in Table 10. The number of heat cycles at which peeling occurred at the interface between the primary plating film and the secondary plating film was 1500 cycles.

[0049]

[Table 8]

(Embodiment 8) The electrolytic plating solution having the composition shown in Table 9 was dipped in the electrolytic plating solution for 15 minutes to form an electrolytic Au- having a plating film thickness of 2 μm.
Example 4 except that Ag plating (primary plating) was performed
A peel strength measurement and a heat cycle test were performed by the same method as described above. As a result, the peel strength was 1.6 kg / cm, as shown in Table 10. The number of heat cycles at which peeling occurred at the interface between the primary plating film and the secondary plating film was 1600 cycles.

[0051]

[Table 9]

(Example 9) After the treatment (7) in Example 1, the wiring board was left in the air at 25 ° C for 24 hours. After standing, whether or not an oxide film was formed on the surface of the primary plating film of the wiring board was judged by the presence or absence of water-repellent phenomenon, and the water-repellent phenomenon was observed. That is, it was found that an oxide film was formed on the surface of the primary plating film. This wiring board was subjected to the treatments (8) to (9) of Example 1 to obtain a multilayer printed wiring board. The peel strength of the wiring board thus obtained is 1.4k.
g / cm. The number of heat cycles in which peeling occurred between the primary plating film and the secondary plating film was 1000 cycles.

Comparative Example 1 Table 1 in Example 1 (7)
2 in the electroless alloy plating solution (primary plating solution) having the composition shown in
For 47 minutes, electroless with plating film thickness of 5.0 μm
A conductor was formed in the same manner as in Example 1 except that the Cu-Ni-P alloy layer 6 was formed, and the peel strength measurement and the heat cycle test were performed. At this time, the coating state of the primary plating layer is, as shown in FIG. 1, a state in which the inside of the anchor recess is completely filled with the primary plating metal (filling ratio in the anchor is 100 vol.
%) And a flat coating. As a result, the peel strength was 1.4 kg / cm, as shown in Table 10. The number of heat cycles at which peeling occurred between the primary plating film and the secondary plating film was 800 cycles.

Comparative Example 2 Table 1 in Example 1 (7)
Other than forming an electroless Cu-Ni-P alloy layer 6 (filling ratio in the anchor: 20 vol%) with a thickness of 0.5 μm of the plating film by immersing in an electroless alloy plating solution having the composition shown in A conductor circuit was formed in the same manner as in Example 1, and a peel strength measurement and a heat cycle test were performed. As a result, the peel strength was 1.0 kg / cm, as shown in Table 10. Further, in the heat cycle test, a crack in the conductor circuit occurred before the peeling of the interface between the primary plating film and the secondary plating film. It is presumed that this is because the bubbles caused by the pinholes in the primary plating film expanded during heating.

Comparative Example 3 In Example 9, the electroless alloy plating solution having the composition shown in Table 1 was dipped for 2 hours and 45 minutes,
A conductor circuit was formed in the same manner as in Example 9 except that the electroless Cu-Ni-P alloy layer 6 (filling ratio in the anchor was 100 vol%) having a thickness of the plating film of 5.0 μm was formed, and the peel strength was measured. And a heat cycle test was performed. As a result, the peel strength was 1.4 kg / cm, as shown in Table 10. The number of heat cycles in which peeling occurred between the primary plating film and the secondary plating film was 500 cycles.

[0056]

[Table 10]

As is clear from the results shown in Table 10, it was confirmed that the printed wiring board of the present invention was excellent in peel strength as compared with the comparative example according to the prior art. Moreover,
It was confirmed that the printed wiring board of the present invention can keep the specific resistance of the conductor low and is excellent in the L / S = 50/50 (μm) forming ability. It was also confirmed that the heat cycle characteristics were excellent.

A test method or evaluation method for peel strength, specific resistance and heat cycle characteristics will be described. (1) Peel strength Measured and evaluated according to JIS-C-6481. (2) Specific resistance The specific resistance ρ means the reciprocal of electrical conductivity. Cross-sectional area S,
The resistance R of the portion of length l is measured by the four-terminal method, and R =
The specific resistance ρ was calculated from (l / S) ρ and evaluated. (3) Heat cycle characteristics A thermal shock test from -65 to 125 ° C was performed, and the presence or absence of peeling at the interface between the primary plating film and the secondary plating film was confirmed in 100 cycle units, and evaluated by the number of cycles at which peeling occurred. did.

[0059]

As described above, according to the present invention, the adhesion between the primary plating layer and the secondary plating layer forming the conductor can be improved, and the conductor can be used even in wiring of higher density and high pattern accuracy. It is possible to stably provide a printed wiring board having excellent adhesion (peel strength) between the resin insulating layer and the resin insulating layer.

[Brief description of drawings]

FIG. 1 is a partial cross-sectional view showing a covering state of a primary plating layer according to a conventional technique.

FIG. 2 is a diagram showing one manufacturing process of the printed wiring board according to the present invention.

[Explanation of symbols]

 1 substrate 2 conductor circuit 3 resin insulation layer 4 opening for via hole 5 plating resist 6 primary plating layer 7 secondary plating layer

Claims (5)

[Claims] 1. A roughened surface of a resin insulating layer provided on a substrate,
In a printed wiring board having a conductor circuit formed by a primary plating treatment and a secondary plating treatment, the conductor circuit is configured such that a roughened surface side including an anchor recess is formed by a primary plated layer provided along the roughened surface. The printed wiring board is characterized in that a secondary plating layer is formed on the surface of the primary plating layer so as to occupy at least a part of the anchor recess. 2. The primary plating layer has a thickness of 1 or more and 2 μm.
The printed wiring board according to claim 1, which is less than m. 3. The printed wiring board according to claim 1, wherein the proportion of the primary plating layer in the anchor recess is 30 to 50 vol%. 4. The primary plating layer is made of an alloy of at least two kinds of Ni, Co, Cu, Au and Ag.
The printed wiring board according to any one of 3 above. 5. The primary plating layer comprises an alloy of at least one or more of Ni, Co, Cu, Au and Ag and at least one or more of Sn, Pb, B, P, C and a transition metal. Item 5. The printed wiring board according to any one of Items 1 to 3.