JPH09162514A - Printed wiring board and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To remarkably improve the heat cycle characteristic of a printed wiring board without sacrificing the adhesive property of the board by forming a copper alloy layer of a gradient alloy, the copper concentration of which becomes higher as going toward the lower surface of the alloy layer. SOLUTION: A copper alloy layer 7 formed on a copper-made lower layer conductor circuit 2 in a printed wiring board is made of a graded alloy, the copper concentration of which becomes higher as going toward the lower surface of the layer 7. Therefore, the adhesion between the circuit 2 and an upper-layer conductor circuit 8 having the copper alloy layer 7 can be improved without sacrificing the adhesion property of the layer 7 with an insulating resin layer. It is preferable to adjust the copper concentration so that the concentration can change within the range of 20-90atm% continuously or in stages from the upper surface side to the lower surface side of the layer 7. In addition, the thickness of the layer 7 is adjusted to 0.5-3μm. In a method for manufacturing the printed wiring board, the bath load of a plating bath is adjusted to 0.2-1.5dm<2> /l in order to form the copper alloy layer 7 having such a copper concentration gradient.

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 and a method of manufacturing the same, and more particularly to a highly reliable printed wiring board having improved adhesion between an upper conductor and a lower conductor formed by an additive method. suggest.

[0002]

2. Description of the Related Art In recent years, electronic devices have been reduced in size and increased in speed with the progress of the electronic industry. Therefore, printed wiring boards and wiring boards on which LSIs are mounted have been made compatible with high density by fine patterns. High reliability has come to be required.

On the other hand, in the additive type printed wiring board, as a means for improving the adhesion between the conductor and the resin insulating layer, for example, a method of forming fine irregularities by chemical etching on the conductor forming surface side of the resin insulating layer. It has been known.
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, when wiring with higher density and higher pattern accuracy is required, it is necessary to reduce the size of the anchor formed by roughening the surface of the resin insulating layer in order to form a fine resist pattern with high accuracy. Becomes Therefore, in the above-mentioned conventional technique, when the anchor is made small, the fracture area becomes small, resulting in a problem that the peel strength is remarkably lowered.

As a means for solving this problem, a method of increasing the strength of the insulating layer resin can be considered, but such a method causes a new problem that the conductive metal portion is broken. In particular, such a fracture phenomenon was remarkable in a conductor made of copper, which generally has a low elastic modulus, a yield point, or a tensile strength.

[0006] Therefore, the inventor previously conducted research on improving the strength of the conductor metal, and it is preferable to use an alloy plating layer having excellent hardness for at least a part of the metal filled in the anchor depressions of the roughened surface. It was found that the printed wiring board disclosed in Japanese Unexamined Patent Publication No. 6-318771 is effective in improving the printed wiring board.

[0007]

However, in the above-proposed printed wiring board, a via hole having an alloy plating layer (for example, a copper-nickel-phosphorus alloy layer) is formed on the lower surface of the conductor in the resin insulating layer. When connecting to the copper pad of the lower conductor, it was found that the copper-nickel-phosphorus alloy layer had a new problem of poor adhesion to the copper pad of the lower conductor. It is considered that this is because the alloy plating layer is formed of a eutectic alloy having a uniform composition, and nickel of this eutectic alloy has a poor affinity with copper.
That is, when forming a conductor circuit having an alloy plating layer made of a eutectic alloy with a uniform composition on the conductor lower surface on a copper lower layer conductor circuit, the upper alloy plating layer adheres to the copper lower layer conductor. There was a problem that was bad.

An object of the present invention is to solve the above problems of the prior art, and particularly to improve the adhesion between the lower conductor circuit made of copper and the upper conductor circuit having a copper alloy layer on the lower side surface. By doing so, it is possible to provide a printed wiring board that is excellent in reliability such as peel strength even in wiring having higher density and higher pattern accuracy.

[0009]

As a result of further intensive research aimed at achieving the above object, the inventor has conceived the present invention having the following contents as its gist. That is, the present invention is a printed wiring board in which a lower conductor circuit made of copper and an upper conductor circuit having a copper alloy layer on the lower side surface are electrically connected via the alloy layer, wherein the copper alloy layer is The printed wiring board is characterized in that the lower side of the alloy layer is formed of a graded alloy having a higher copper concentration. In the printed wiring board of the present invention, the copper alloy layer has a copper concentration of 20 to 90 atm from the upper surface side to the lower surface side of the alloy layer.
%, More preferably in the range of 40 to 80 atm%, it is desirable to be formed of a graded alloy that increases continuously or stepwise, and the thickness of the copper alloy layer is desirably 0.5 to 3 μm. .

Further, in the method for manufacturing a printed wiring board according to the present invention, when the upper conductor circuit having the copper alloy layer on the lower side surface is formed on the lower conductor circuit made of copper by plating, the copper is lowered toward the lower surface. It is characterized in that a copper alloy layer made of a highly concentrated gradient alloy is formed by adjusting the bath load of the plating bath. In order to form a copper alloy layer composed of a graded alloy in which the copper concentration changes continuously or stepwise in the range of 20 to 90 atm%, the bath load of the plating bath should be 0.2 dm ²
It is desirable to adjust to a range of over 1 / l and 1.5 dm ² / l or less.

In the present invention, the lower-layer conductor circuit means a conductor circuit on the side relatively close to the core substrate of the printed wiring board, and conversely, the upper-layer conductor circuit relatively to the core substrate. A conductor circuit on the far side. The lower side surface or the lower surface side means the side relatively close to the core base material of the printed wiring board.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The printed wiring board of the present invention is characterized in that the copper alloy layer formed on the lower conductor circuit made of copper is composed of a graded alloy having a higher copper concentration on the lower surface side of the alloy layer. is there. As a result, a printed wiring board having excellent adhesion such as peel strength, which improves the adhesion between the lower conductor circuit made of copper and the upper conductor circuit having a copper alloy layer while maintaining the adhesion with the resin insulation layer, is provided. can do.

Here, in the printed wiring board of the present invention, the copper alloy layer has a copper concentration of 20 to 90 atm%, more preferably 40 to 80 atm from the upper surface side to the lower surface side of the alloy layer.
It is preferable to increase continuously or stepwise in the range of%. The reason for this is that within the above range, it is possible to improve the adhesion to the lower-layer copper conductor of the copper alloy layer without affecting the resistance value and peel strength.
Incidentally, the atm% of the copper concentration mentioned here indicates the existence ratio of the number of copper atoms in the total number of atoms, and is measured by a fluorescent X-ray analyzer. In addition, continuous means a plating film obtained when treated with the same plating solution with adjusted bath load, and when the copper concentration always changes from the lower surface side to the upper surface side of the copper alloy layer. is there. Stepwise means Cu /
A plating film obtained when treated with two or more plating solutions with different Ni solution concentrations, where the copper concentration changes stepwise from the bottom side to the top side of the copper alloy layer while maintaining a constant value. Say. That is, if a graph is created in which the horizontal axis represents the distance from the lower side surface of the copper alloy layer and the vertical axis represents the copper concentration, the former draws a downward-sloping curve or straight line, and the latter draws a downward-sloping staircase graph. .

The copper alloy layer having such a copper concentration gradient is
It is desirable that the film thickness is 0.5 to 3 μm. The reason is that if the film thickness is less than 0.5 μm, the peel strength of the copper alloy layer decreases, while if it exceeds 3 μm, the copper alloy layer takes a long time to deposit, which is not economical.

In the method for producing a printed wiring board of the present invention, in order to form the copper alloy layer having the above-mentioned copper concentration gradient, the bath load of the plating bath is preferably set to exceed 0.2 dm ² / l.
The feature is that it is adjusted within the range of 1.5 dm ² / l or less. As a result, a copper alloy layer made of a graded alloy in which the copper concentration changes continuously or stepwise in the range of 20 to 90 atm% can be formed on the copper lower layer conductor circuit, and the copper lower layer conductor circuit can be formed. It is possible to provide a printed wiring board having improved reliability such as peel strength, which has improved adhesion between the upper conductor circuit. The bath load of the plating bath indicates how much area of the material to be plated must be plated per unit plating solution, and bath load = (area of conductor circuit to be plated: m ² ). / (Amount of plating solution: 1)

[0016] In the present invention method, the reason for adjusting the range 0.2dm ² / l beyond the 1.5 dm ² / l or less a bath loading of the plating bath, at a bath load 0.2dm ² / l or less, uniform If a copper alloy layer with a different composition is deposited, while the bath load exceeds 1.5 dm ² / l, the amount of nickel on the base material side (lower conductor side, lower surface side) of the copper alloy layer will increase and the resistance value will decrease. This is because the adhesion with the lower copper conductor of the copper alloy layer is reduced.

In the method of the present invention, alloy plating using a plating bath adjusted to the above-mentioned bath load is preferably performed under the following conditions. That is, it is desirable that the bubbling condition is 40 to 100 l / min in terms of air amount. The reason for this is that if it is less than 40 l / min, the stability of the plating solution is lowered and the stirring conditions are not sufficient. On the other hand, if it exceeds 100 l / min, the plating solution becomes excessively stable and the deposition rate of the alloy plating decreases. It is desirable that the rocking condition is that the stroke is 4 cm and the rocking is performed once every 7 seconds. The reason for this is that if the rocking conditions become gentler than this, the penetration of the plating solution into the via holes and through holes deteriorates, and if the rocking conditions become severer than this, the substrates will bend and will easily come into contact with each other. Is. The shock swing condition is a displacement length of 5.5 cm, and it is desirable to swing every 5 seconds. The reason why such shock swing is necessary is that the H ₂ gas generated in the plating reaction is released from the substrate, so that the throwing power of the plating is improved. Note that other plating conditions can be carried out according to a conventional method and are not particularly limited.

In the printed wiring board of the present invention and the method for manufacturing the same as described above, the metal other than copper constituting the copper alloy layer may be a combination of metals that form an alloy with copper. From the viewpoint of maintaining low resistance, it is desirable to use at least one selected from nickel, cobalt, silver, gold and tin. Above all,
Nickel and cobalt can be advantageously used because they have excellent hardness and can improve the peel strength.

Further, in the present invention, since a wiring having a higher density and a higher pattern accuracy is provided, it is preferable that the conductive metal be capable of electrolytic plating or electroless plating. Co, Cu, Au and Ag,
And Sn, Pb, B, P, C and transition metals are used.

Among them, the Cu-Ni-P alloy is preferable in that it has excellent strength and resistance characteristics, and that its plating bath has less abnormal precipitation and the stability of the plating bath is excellent. here,
The source of Cu 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 any water-soluble source, but NiSO ₄ , NiCl ₂ , nickel acetate, and Ni (NO ₃ ) ₂ are preferable.

In the present invention, the substrate constituting the printed wiring board is a glass epoxy substrate, a polyimide substrate, a bismaleimide triazine resin substrate, a ceramic substrate of alumina, aluminum nitride, silicon nitride, etc., a metal substrate of iron, aluminum, stainless steel, etc. Etc. can be used. In particular, a copper clad laminate formed by forming a copper foil on one surface of a substrate is etched to form a copper pattern, which is most commonly used. It is also possible to use an adhesive layer for electroless plating formed on a substrate, roughening this to form a roughened surface on the surface of the adhesive layer, and subjecting this to electroless plating to form a copper pattern.

In the present invention, the interlayer insulating layer of the printed wiring board is, for example, a thermosetting resin such as an epoxy resin, a polyimide resin, a bismaleimide triazine resin or a phenol resin, a photosensitive resin obtained by sensitizing these resins, or It is composed of a thermoplastic resin such as polyether sulfone, a resin composite of a thermoplastic resin and a thermosetting resin, or a resin composite of a photosensitive resin and a thermoplastic resin. It is advantageous to roughen the surface of such an interlayer insulating layer with an oxidizing agent, an acid, an alkali, etc., and it is possible to improve the adhesion with the conductor circuit by the uneven surface formed on the surface of the insulating layer. it can. An adhesive for electroless plating is an interlayer insulating agent advantageous for forming the uneven surface. This adhesive for electroless plating is capable of uniformly roughening and forming an effective anchor dent, so that it is resistant to acid or oxidant in heat-resistant resin that is hardly soluble in acid or oxidant. An adhesive agent in which soluble heat-resistant resin particles are dispersed is preferably used. That is, by removing the heat-resistant resin particles soluble in an acid or an oxidizing agent by the roughening treatment, an octopus-shaped anchor can be formed on the surface of the insulating layer, and the adhesion with the conductor circuit can be improved. In particular, in order to obtain a fine pattern of L / S = 50/50 (μm) or less, it is desirable that the heat-resistant resin particles have an average particle size of 10 μm or less. The depth needs to be 15 μm or less, and the alloy plating according to the present invention is effective for obtaining high peel strength (adhesion) even with such a shallow anchor. That is, the alloy plating according to the present invention, in particular, the Cu-Ni-P alloy plating is excellent in the depositability, and is deposited even in a small gap with good followability even on a roughened surface having a fine anchor shape. To do. Therefore,
Even after applying the alloy plating, the anchor shape remains,
Since the secondary plating is applied here, the alloy plating according to the present invention is also excellent in the adhesiveness with the upper conductor circuit.

Here, as the heat-resistant resin which is hardly soluble in an acid or an oxidizing agent, a photosensitized thermosetting resin or a composite of a photosensitized thermosetting resin and a thermoplastic resin is desirable.
This is because the photosensitization can easily form the opening for forming the via hole 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, as a composite with such a thermoplastic resin, a composite of an epoxy acrylate obtained by reacting an epoxy resin with acrylic acid, methacrylic acid, or the like and a polyether sulfone is preferable. Especially,
The epoxy acrylate is preferably one in which 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. . They are,
This is because a complicated anchor can be formed. 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 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, phosphoric acid, hydrochloric acid, sulfuric acid, organic acids (formic acid, acetic acid, etc.) and the like can be used as the acid used for the roughening treatment, and the organic acid is preferable. The reason is that there are few residual ions and migration is less likely to occur. Also, it is difficult to corrode the inner layer conductor circuit exposed from the via hole. As the oxidizing agent, chromic acid, permanganate (potassium permanganate, etc.) and the like are desirable.

The interlayer insulating layer as described above is
It 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) In the interlayer insulating layer provided between the upper-layer conductor circuit and the lower-layer conductor circuit, the side close to the upper-layer conductor circuit is soluble in acid or oxidant in a heat-resistant resin that is hardly soluble in acid or oxidant. An interlayer insulating layer having a two-layer structure, which is an adhesive for electroless plating in which heat-resistant resin particles are dispersed, and a heat-resistant resin hardly soluble in an acid or an oxidant is used on the side close to the lower conductor circuit. 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) In the interlayer insulating layer provided between the upper conductor circuit and the lower conductor circuit, a filling resin material is embedded between the lower conductor circuits, and the lower conductor circuit and the surface of the filling resin material are flush with each other. And a heat-resistant resin layer that is hardly soluble in an acid or an oxidizing agent is formed on top of this, and a heat-resistant resin that is soluble in an acid or an oxidizing agent in a heat-resistant resin that is poorly soluble in an acid or an oxidizing agent is further formed thereon. An interlayer insulating layer having a three-layer structure, in which an adhesive for electroless plating, in which functional resin particles are dispersed, is formed. In this configuration, since the filling resin material is filled between the lower layer conductor circuits, the surface of the substrate becomes smooth and there is no development failure caused by the 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.

In the present invention, a commercially available product can be used as the plating resist constituting the printed wiring board, but it is desirable to use an epoxy acrylate obtained by reacting an epoxy resin with acrylic acid or methacrylic acid, and an imidazole curing agent. And a composition comprising an epoxy acrylate, a polyether sulfone, and an imidazole curing agent are preferred. Here, the ratio of epoxy acrylate and polyether sulfone is 50/50.
Approximately 80/20 is desirable. 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. Epoxy acrylate accounts for 20-80% of all epoxy groups.
It is desirable to react 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. Furthermore, as the epoxy resin which is the basic skeleton resin, novolac type epoxy resin,
For example, cresol novolac type epoxy resin and phenol novolac type epoxy resin are 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.

In the present invention, a commercially available product (eg, Tamura Kaken Co., Ltd., trade name: DSR-2200, 1DX-5-5) can be used as the solder resist constituting the printed wiring board. Desirably, an acrylate of a novolac type epoxy resin containing a dye such as phthalocyanine green and an imidazole curing agent is suitable.

[0030]

【Example】

(Example 1) (1) By attaching a resist film to a copper clad laminate (FIG. 1 (b)), exposing and developing to form an etching resist, and performing an etching treatment with an etching solution such as cupric chloride, Conductor circuits 2 were formed on both sides of the substrate 1 (see FIG. 1 (b)). (2) The surface of the conductor circuit 2 thus formed was subjected to blackening reduction treatment according to a conventional method to roughen the conductor surface. (3) Solvent-free epoxy resin (Y-KA Shell, E-807)
100 parts by weight, 170 parts by weight of silica (particle size 1.6 μm), 6 parts by weight of curing agent (2-E4MZ-CN manufactured by Shikoku Kasei) and defoaming agent
1.5 parts by weight are mixed to form an insulating material composition (filling resin material 3), which is applied to both surfaces of the substrate 1 treated in (2) above by using a roll coater, and this is applied at 60 ° C. for 1 hour. It was dried for an hour and further cured at 150 ° C. for 10 hours. After that, the resin layer was ground by a belt sander until the surface of the conductor circuit 2 was ground by about 1 μm to smooth the surface of the substrate (FIG. 1).
(c)). (4) The conductor circuit surface thus exposed was subjected to needle-like crystal alloy plating (made by Ebara: interplate plating) made of copper-nickel-phosphorus. (5) 70 parts by weight of 25% acrylate of cresol novolac type epoxy resin (Nippon Kayaku, molecular weight 2500) dissolved in diethylene glycol dimethyl ether (DMDG), 30 parts by weight of polyether sulfone (PES), imidazole curing agent (Shikoku Kasei Co., Ltd., trade name: 2E4MZ-CN) 4 parts by weight, caprolactone modified tris (acryloxyethyl) isocyanurate (a product of Toagosei, trade name:
10 parts by weight of Aronix M325), 5 parts by weight of benzophenone (manufactured by Kanto Kagaku) as a photoinitiator, and 0.5 parts by weight of photosensitizer Michler's ketone (manufactured by Kanto Kagaku) are added while adding NMP, and the viscosity is obtained with a homodisper stirrer. 2000 CPS
And then kneading with a three-roll mill to obtain an interlayer insulating agent. (6) On the other hand, diethylene glycol dimethyl ether (DM
DG) 70 parts by weight of 25% acrylate of cresol novolac type epoxy resin (Nippon Kayaku, molecular weight 2500) dissolved in DG), 30 parts by weight of polyether sulfone (PES), imidazole curing agent (Shikoku Kasei, trade name: 2E4MZ-CN) 4 parts by weight, caprolactone-modified tris (acryloxyethyl) isocyanurate (manufactured by Toagosei, a photosensitive monomer)
Product name: Aronix M325) 10 parts by weight, a mixture of 5 parts by weight of benzophenone (manufactured by Kanto Kagaku) as a photoinitiator and 0.5 part by weight of photosensitizer Michler's ketone (manufactured by Kanto Kagaku), and an average particle size of melamine resin particles. After mixing 35 parts by weight of 5.5 μm and 5 parts by weight of particles having an average particle size of 0.5 μm, NMP was further added, and the viscosity was adjusted to 2000 CPS with a homodisper stirrer, followed by kneading with a three-roll mill. I got an adhesive. (7) First, the wiring board that has been subjected to the treatment of (4) is coated with the interlayer insulating agent using a roll coater and dried at 60 ° C.,
Next, the adhesive was applied and dried at 60 ° C. to form an interlayer insulating layer 4 having a two-layer structure (see FIG. 1 (d)). (8) A photomask with a 100 μmφ black circle printed on it by attaching a polyethylene terephthalate (PET) film with an adhesive on the back side to the wiring board that has been subjected to the treatment in (7) above to block O ₂ Super-high pressure mercury lamp 5
It was exposed at 00 mj / cm ² and spray-developed with DMDG to form an opening to be a via hole of 100 μmφ on the wiring board. Furthermore, this wiring board was exposed with an ultra-high pressure mercury lamp at about 3000 mj / cm ² , exposed at 100 ° C. for 1 hour, then
By performing a heat treatment (post-baking) at 150 ° C. for 5 hours, an interlayer insulating layer 4 having a thickness of 50 μm and having an opening 5 corresponding to a photomask film and having excellent dimensional accuracy was obtained.
O ₂ deactivates radicals before the initiation of photopolymerization and inhibits polymerization. PET film can block O ₂ . (9) By alternately roughening the surface of the interlayer insulating layer 4 thus formed using potassium permanganate (pH = 13) and phosphoric acid, a large number of fine anchors are formed on the surface of the interlayer insulating layer 4. To form a roughened surface (see FIG. 1 (e)). (10) Next, after providing the catalyst nuclei necessary for the first deposition of the electroless plated metal, a liquid resist was applied and exposed and developed according to the following procedure (see FIG. 1 (f)). . Epoxy group 25 of cresol novolac type epoxy resin (manufactured by Nippon Kayaku, trade name: EOCN-103S) dissolved in DMDG
% Acrylated photosensitizing oligomer (Molecular weight:
4000), PES (molecular weight: 17,000) 30 parts by weight, imidazole curing agent (manufactured by Shikoku Kasei, product name: 2 PMHZ-PW), acrylated isocyanate as a photosensitive monomer (product name: Aronix M215 manufactured by Toagosei), photo initiation Benzophenone (manufactured by Kanto Chemical Co., Inc.) and photosensitizer Michler Ketone (manufactured by Kanto Chemical Co., Inc.) were mixed with NMP so that the composition shown below was obtained, and the viscosity was adjusted to 3000 CPS with a homodisper stirrer. The mixture was kneaded with a roll to obtain a liquid resist. Resin composition: Photosensitive epoxy / PES / M325 / BP / MK / imidazole = 70/30/10/5 / 0.5 / 5. This liquid resist is applied on the interlayer insulating layer of (9) using a roll coater and dried at 60 ° C to a thickness of about 30μ.
m of resist layers were formed. . Then, a mask film on which a conductor circuit pattern of L / S = 50/50 is drawn is brought into close contact, and the ultra high pressure mercury lamp 1000J
/ Exposed with cm ^2, by which the spraying developed with triethylene glycol dimethyl ether (DMTG), to form a plating resist dislodgement conductor circuit pattern portion on the wiring board. Furthermore, 6000J by ultra-high pressure mercury lamp
/ Exposed with cm ^2, 1 hour at 1000 ° C., a heating treatment was performed at subsequent 3 hours at 0.99 ° C., to form a permanent resist 6 using a resist resin. (11) Next, the wiring board having the permanent resist 6 (plating resist) formed thereon was subjected to copper-nickel-phosphorus plating (primary plating). The composition and plating conditions of this plating solution are shown in Tables 1 and 2. In this way, as shown in FIG. 1, a copper-nickel-phosphorus-plated thin film 7 having a thickness of about 2 μm is formed in the via hole opening 5 which is a non-resist formation portion.
Was formed (see FIG. 1 (f)). Since this alloy plating film has excellent followability to the roughened surface, the anchor is formed by tracing the shape of the roughened surface as it is (see Fig. 2). Even when copper plating is applied to this upper layer, the upper layer It was confirmed that the copper conductor was difficult to peel off. Fig. 3 shows the results of an examination of the relationship between the deposition time of this alloy plating film and the copper concentration in the film.
Shown in As is clear from this figure, it was found that the copper concentration continuously changes from the upper surface to the lower surface in the range of 60 to 80 atm%. The copper concentration was measured by fluorescence X
According to a line analyzer. Also, under the same conditions, the bath load is 0.2 dm ²
/ L is shown in FIG. 3, and the bath load is 1.0 dm ² / l in FIG. As is clear from FIG. 3, the bath load was set to 0.
It can be seen that when the concentration is ² dm ² / l, the copper concentration hardly changes between the upper surface side and the lower surface side. On the other hand, the bath load is 0.4 dm ^2.
When it is set to 1 / l, the copper concentration continuously changes from the upper surface side to the lower surface side in the range of 60 to 80 atm% at the plating film thickness of 0 to 2 μm. Moreover, as is clear from FIG. 4, the bath load was 1.
It can be seen that when the concentration is 0 dm ² / l, the copper concentration continuously changes from the upper surface side to the lower surface side in the range of 40 to 90 atm% at the plating film thickness of 0 to 2 μm.

[0031]

[Table 1]

[0032]

[Table 2]

(12) Next, the plated wiring board was washed with water and the plating solution adhering to the wiring board was washed away. Then, the copper-nickel-phosphorus plating thin film 7 is subjected to the same treatment as the activation treatment of treating the glass epoxy plate with an acidic solution.
The surface oxide film was removed. Then, secondary plating was performed on the copper-nickel-phosphorus thin film 7 without performing Pd substitution (see FIG. 1 (g)). Here, as the plating bath for secondary plating, an electroless copper plating bath for secondary plating containing TEA as a complexing agent, specifically, a plating bath having the composition shown in Table 3 was used. The plating conditions are: plating bath temperature: 50-70 ° C
Plating immersion time: 90 to 360 minutes, plating deposition rate is 6
It was μm / hour. In this way, the copper plating film 8 as the secondary plating film was formed on the surface of the copper-nickel-phosphorus plating thin film 7 as the primary plating film. That is, a conductor pattern composed of two kinds of metal layers and a via hole (upper layer conductor circuit) were obtained.

[0034]

[Table 3]

Example 2 Basically the same as in Example 1, except that the mixed plating solution of copper and cobalt shown in Table 4 was used as the primary plating solution, and the primary plating was performed under the plating conditions shown in Table 5. did. The obtained primary plating film is a Cu-Co-P alloy, and its copper concentration is 60 from the upper surface side to the lower surface side.
It was found to change continuously in the range of ~ 80 atm%.

[0036]

[Table 4]

[0037]

[Table 5]

(Comparative Example) Basically the same as in Example 1, but the primary plating was performed with the bath load of the primary plating solution being 0.1 dm ² / l. As a result, the bath load shown in Example 1 was 0.2d.
Similar to the case of m ² / l, the copper concentration was almost uniform.

With respect to the printed wiring boards obtained in Examples 1 and 2 and Comparative Example 1 in this manner, a heat cycle test and a peel strength measurement were conducted in order to examine the adhesion between conductors. Heat cycle test is -65 ° C (15 minutes)
→ 25 ° C (15 minutes) → 125 ° C (15 minutes) was set as one cycle, and the disconnection state of the via hole was observed with an optical microscope, and the number of cycles at which disconnection was confirmed was evaluated. The peel strength was measured and evaluated according to JIS-C-6481.

The results of the heat cycle test and peel strength measurement are also shown in Table 6. As is clear from the results shown in this table, it was confirmed that the structure of the printed wiring board of the present invention can significantly improve the heat cycle characteristics.

[0041]

[Table 6]

[0042]

As described above, according to the present invention, since the copper alloy layer formed on the lower conductor circuit made of copper is composed of a graded alloy having a higher copper concentration on the lower surface side, it is possible to form an interlayer insulating layer. The adhesiveness between the lower conductor circuit made of copper and the upper conductor circuit having the copper alloy layer can be improved while maintaining the adhesiveness. As a result, it is possible to stably provide a printed wiring board having significantly improved heat cycle characteristics even in wiring having higher density and higher pattern accuracy.

[Brief description of the drawings]

FIG. 1 is a diagram showing one manufacturing process of a printed wiring board of the present invention.

FIG. 2 is a micrograph showing (a) a planar structure and (b) a cross-sectional structure of an alloy plating film formed on a roughened surface of an interlayer insulating layer according to the printed wiring board of the present invention.

FIG. 3 is a graph showing the relationship between the deposition time of an alloy plating film and the copper concentration in the film.

FIG. 4 is a graph showing the relationship between the deposition time of the alloy plating film and the copper concentration in the film.

[Explanation of symbols]

1 Substrate 2 Conductor Circuit (Lower Layer Conductor Circuit) 3 Filling Resin Material 4 Interlayer Insulating Layer (Adhesive Layer) 5 Opening for Via Hole 6 Plating Resist 7 Cu-Ni-P Alloy Plating Thin Film (Copper Alloy Layer, Primary Plating Film) 8 Cu plating film (secondary plating film)

Claims (5)

[Claims] 1. A printed wiring board in which a lower conductor circuit made of copper and an upper conductor circuit having a copper alloy layer on a lower side surface are electrically connected through the alloy layer, wherein the copper alloy layer comprises: A printed wiring board, wherein the lower surface side of the alloy layer is formed of a graded alloy having a higher copper concentration. 2. The copper alloy layer is formed of a graded alloy in which the copper concentration increases continuously or stepwise in the range of 20 to 90 atm% from the upper surface side to the lower surface side of the alloy layer. The printed wiring board according to claim 1, wherein: 3. The printed wiring board according to claim 1, wherein the copper alloy layer has a film thickness of 0.5 to 3 μm. 4. A method of manufacturing a printed wiring board, wherein when forming an upper conductor circuit having a copper alloy layer on a lower side surface on a lower conductor circuit made of copper by plating, a gradient alloy having a higher copper concentration on the lower surface side. Is formed by adjusting the bath load of the plating bath. 5. The plating load of the plating bath exceeds 0.2 m ² / l.
By adjusting the range to 5dm ² / l or less, the copper concentration becomes 20
The manufacturing method according to claim 4, wherein the copper alloy layer is formed of a graded alloy that changes continuously or stepwise in the range of 90 to 90 atm%.