JPH08193275A - Electroless plating solution, electroless plating method and production of printed circuit board - Google Patents

Abstract

PURPOSE: To increase the average rate of deposition of plating by using an electroless plating soln. contg. compds. of one or more kinds of elements selected from among Co, Ni, Au, Ag, Sn, Pb, B and transition elements, a Cu compd., a trialkanolamine, a reducing agent and a pH adjusting agent. CONSTITUTION: The temp. of this electroless plating soln. is regulated to <=50 deg.C. The concn. of a Cu compd. in this plating soln. is 1-4.3mmol, the concn. of an Ni or Co compd. is 20-80mmol and the concn. of a trialkanolamine is 0.1-0.8mol. The trialkanolamine is at least one selected from among triethanolamine, trisopropanolamine, tri methanolamine and tripropanolamine. A reducing agent in this plating soln. is at least one selected from among aldehyde, hypophosphites, borohydrides and hydrazine and a pH adjusting agent is at least one selected from among NaOH, KOH and Ca(OH)2 . Even when the average rate of deposition of plating is increased, peeling strength is not reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electroless plating method, and more particularly to a high-speed electroless plating method suitable for forming a conductor pattern in a wiring board manufacturing process.

[0002]

2. Description of the Related Art In the formation of a conductor pattern in the manufacturing process of a printed wiring board, a plating resist is provided on a predetermined portion of a base material, and then electroless copper plating is applied to the non-resist portion.

Conventionally, a conductor pattern has been formed by using an electroless plating bath using EDTA as a complexing agent. In order to apply electroless plating, an adhesive layer for electroless plating whose surface has been roughened in advance is often formed, but the EDTA plating bath has an excellent filling rate of plating in the anchor. Such a plating bath has a low plating deposition rate, and it takes a dozen hours or more to form a conductor circuit having a thickness of several tens of μm in this plating bath, which is not industrially appropriate.

In electroless copper plating using only the EDTA plating bath, the strength of the deposited plating film is low and it is difficult to secure the peel strength of the conductor pattern. Therefore, the first plating deposition (primary plating film) is processed at a low speed in a plating bath using EDTA as a complexing agent,
Next, a method of performing higher-speed plating (secondary plating film) has been proposed. Further, a method has been proposed in which the first plating deposition (primary plating film) is treated with composite plating having a high strength of the plating film at a low speed, and then a high speed plating is performed (Japanese Patent Laid-Open No. 6-318771). . For high speed plating, for example, triethanolamine (TEA)
Electroless plating method in which the compound is used as a complexing agent (Japanese Patent Application Laid-Open No. 1-1.
No. 6881) is preferable.

[0005]

However, while the thickening plating bath containing TEA has an advantage of high deposition rate, it is difficult to deposit on the surface of the primary plating film formed by the plating bath containing EDTA. There are drawbacks. Therefore, a means for activating the surface by subjecting the primary plating film to an acid treatment is used, but even with such a method, the secondary plating film cannot be deposited, and the palladium is further deposited on the primary plating film. Is given (Pd substitution)
There was a need. However, when such Pd substitution is performed,
Not only does this lead to an increase in cost, but there is also the problem that abnormal deposition occurs due to the loss of Pd from the primary plating film that is the base. There is also a problem that the amount of copper plating deposited on an unnecessary portion increases, and thus the plating bath for thickening is deteriorated more quickly.

Further, in the technique disclosed in Japanese Patent Laid-Open No. 6-318771, citric acid is used as a complexing agent for the primary plating bath, and when a plating solution using TEA as a complexing agent is used for the secondary plating, The problem was that plating did not deposit.

The present invention has been made to solve the above-mentioned problems, and an object thereof is to achieve high-speed plating and to prevent peeling strength from decreasing even when the plating deposition rate is increased, and to provide thick coating. An object of the present invention is to provide an electroless plating solution that can eliminate the need for Pd substitution before plating, an electroless plating method using the same, and a method for manufacturing a printed wiring board.

[0008]

In order to solve the above problems, in the first group of inventions of the present application, "cobalt, nickel,
"A compound of at least one element selected from gold, silver, tin, lead, boron, and transition elements, and a monoalkanolamine, a reducing agent, a pH adjusting agent" or "cobalt, nickel, gold, silver, tin, lead, An electroless plating solution comprising a compound of at least one element selected from boron and transition elements, and a copper compound and a monoalkanolamine, a reducing agent, a pH adjusting agent, and a primary plating film for forming the same. The electroless plating method used and the method for manufacturing a printed wiring board using the same are proposed.

In the second group of inventions of the present application, a copper compound, a trialkanolamine, a reducing agent of 0.1 M or less,
Electroless plating solution consisting of pH adjuster, or electroless plating solution consisting of copper compound, trialkanolamine, reducing agent and pH adjuster and having a solution temperature of 50 ° C. or lower for use in forming a primary plating film A plating method and a printed wiring board manufacturing method using the plating method are proposed.

Since the electroless plating solution of the invention of the first group of the present application uses trialkanolamine as a complexing agent, high-speed plating using a trialkanolamine as a complexing agent as a secondary plating solution (deposition rate 5 μm / Hour or more), the secondary plating does not become unprecipitated, and there is no need to newly add catalyst nuclei to the surface of the primary plating film, and the overall plating deposition rate (average plating deposition rate) ) Can be raised.

Further, since the composite metal can be formed, the strength of the plating film is higher than that of a pure metal film, and the peeling strength can be improved by filling the roughened surface of the adhesive layer for electroless plating.

The electroless plating solution of the second group of inventions of the present application uses a reducing agent of 0.1 M or less or has a solution temperature of 5%.
By setting the temperature to 0 ° C. or lower, or using a reducing agent of 0.1 M or lower and the liquid temperature to 50 ° C. or lower, the deposition rate can be set to 2 μm / hour or less, and therefore
It is possible to improve the filling rate of the roughened surface of the adhesive layer for electroless plating, and it is possible to prevent a decrease in peel strength due to speeding up.

Moreover, high-speed plating using a trialkanolamine as a complexing agent as a secondary plating solution (deposition rate 5 μm /
(Over time), the secondary plating does not become unprecipitated, there is no need to newly add catalyst nuclei to the surface of the primary plating film, and the plating deposition rate (average plating deposition rate) is increased as a whole. be able to.

The obtained metal film is a primary plating film,
The secondary plating film is also copper, and does not peel off at the plating film interface due to the difference in thermal expansion coefficient and plating stress. The "primary plating" described in the present invention means that a plated film is directly deposited on the insulating substrate, and generally the film thickness is relatively thin. The "secondary plating" is to deposit on the primary plating or the metal film, and has a relatively large film thickness.

The compound of at least one element selected from gold, silver, tin, lead, boron and transition elements is
Potassium gold cyanide, potassium silver cyanide, tin chloride,
Examples include tin pyrophosphate, lead pyrophosphate, boric acid, sodium tungstate, and iron oxalate.

The trialkanolamines include triethanolamine (TEA) and triisopropanolamine (T
It is preferably at least one selected from IA), trimethanolamine (TMA) and tripropanolamine (TPA). This is because the complexing power is excellent. Further, since they form a complex only under the strongly basic condition, they do not become a complex under the neutral condition and do not remain on the conductor circuit, so that conduction failure or migration does not occur.

The reducing agent is an aldehyde, hypophosphite (called phosphinate or phosphinate),
At least 1 selected from borohydride salts and hydrazine
Seed is desirable. This is because these reducing agents are water-soluble and have excellent reducing power. If a Ni compound is used, hypophosphite is used.

The concentration of the reducing agent is 0.1 to 0.24M.
It is desirable that The reason for this is that if it is less than 0.1 M, the reducing power is insufficient and the plating becomes slow (2 μm / hour or less), and if it exceeds 0.24 M, the metal ions in the plating solution are reduced and the plating solution decomposes. Because I will do it. In the invention of the second group of the present application, the concentration of the reducing agent is set to 0.1 M or less to intentionally reduce the plating deposition rate to improve the filling rate of the roughened surface of the plating film.

The electroless plating solution preferably contains an iron compound and / or 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, and the iron compound is a reaction initiator and can suppress bath decomposition.

As the iron compound, potassium ferrocyanide, potassium ferricyanide and the like are preferable. The pH
The adjusting agent is at least one selected from sodium hydroxide, potassium hydroxide and calcium hydroxide, and is a basic compound. This is because the trialkanolamine forms a complex under basic conditions.

The concentration of the pH adjusting agent is 0.3 to 0.7.
M is good. This is because the pH can be adjusted to about 11 to 13 within this range. The electroless plating solution of the invention of the first group of the present application is preferably composed of a copper compound, a nickel compound or a cobalt compound, a trialkanolamine, a reducing agent, and a pH adjusting agent. The reason for this is that copper and nickel (or cobalt) obtained by this plating solution, and when hypophosphite is used as a reducing agent, alloys of copper, nickel (or cobalt) and phosphorus are obtained. Is excellent in strength and also excellent in electric conductivity, and is suitable for a conductor pattern of a wiring board.

The concentration of the copper compound is 1.0 to 4.3 m.
Concentration of M, nickel compound or cobalt compound is 2
0-82mM, trialkanolamine concentration 0.1
It is desirable to be 0.8M. This is because when the concentration of the copper compound, nickel compound or cobalt compound is in the above range, the composition of the plated film having excellent electric conductivity and strength can be obtained. Also, if the concentration of trialkanolamine is not within the above range, the precipitation reaction, especially the eutectoid reaction does not occur.

The copper, nickel, and cobalt compounds are preferably copper sulfate, nickel sulfate, cobalt sulfate, copper chloride, nickel chloride, cobalt chloride, and other copper, nickel, cobalt sulfates, and chlorides.

As a method of using the electroless plating solution of the present invention, a catalyst nucleus is provided on an adhesive layer for electroless plating whose surface is roughened, and this is used as the electroless plating solution of the present invention. The means for precipitating a plating film by immersing the plating bath in

A preferable plating method using the electroless plating solution of the invention of the first group of the present invention is an electroless plating method in which the primary plating is applied on the substrate and then the secondary plating is performed on the primary plating film. In the plating bath for the primary plating, the electroless plating solution described above is used, and as the secondary plating, a trialkanolamine, a copper compound, a reducing agent,
An electroless plating solution containing a pH adjuster is used.

Since the primary plating film directly contacts the roughened surface of the adhesive for electroless plating, the strength of the plating film controls the peel strength. For this reason, it is desirable that the primary plating film be fine crystal grains and have high strength. By using the electroless plating solution of the present invention, it is possible to realize a plating film having fine crystal particles as fine as EDTA. Further, since the electroless plating solution can easily deposit the composite metal, the peel strength can be improved.

As the secondary plating, high-speed plating using a trialkanolamine as a complexing agent (precipitation rate 5 μm /
(Over time), the secondary plating does not become unprecipitated, and it is not necessary to newly add catalyst nuclei to the primary plating film, and the plating rate (average plating rate) is increased as a whole. You can

Further, according to this method, since the complexing agents of the primary plating and the secondary plating are of the same type, the secondary plating solution can be directly immersed in the secondary plating solution without washing with water after the primary plating. Since the plating solution is not contaminated, the number of steps can be reduced.

The method according to the invention of the second group of the present application is an electroless plating method in which primary plating is performed on a substrate and then secondary plating is performed on the primary plating film. Is an electroless plating solution containing a copper compound, a trialkanolamine, a reducing agent of 0.1 M or less, and a pH adjusting agent, or a copper compound, a trialkanolamine, a reducing agent, and a pH adjusting agent, and the temperature of the solution is 50 ° C. Using the following electroless plating solution, the deposition rate was 2 μm /
In addition to the time, the electroless plating solution containing a trialkanolamine, a copper compound, a reducing agent, and a pH adjusting agent is used as the secondary plating, and the deposition rate is 5 μm.
/ It is characterized in that it is more than an hour.

According to this method, the deposition rate of the primary plating film is as low as 2 μm / hour or less, the filling rate of the surface of the adhesive layer for electroless plating with respect to the octopus-like anchor is high, and the decrease in peel strength can be prevented. Since the subsequent plating rate is 5 μm / hour or more, a conductor circuit can be formed in a short time, which is industrially advantageous. Moreover, since the complexing agents for the primary plating and the secondary plating are of the same type, there is no need for washing with water, and the secondary plating solution is not contaminated even when immersed in the plating solution, so the number of steps can be reduced.

The lower limit of the primary plating is 0.1 μm /
It is desirable to set the time and the upper limit of the secondary plating to be 10 μm / hour. Further, since the primary plating film and the secondary plating film are made of the same copper, it is possible to prevent peeling due to heat cycle at the plating interface.

This secondary plating has a liquid temperature of 50 ° C. to 90 ° C.
℃ or the amount of reducing agent 0.1M ~ 0.24M
Or by setting the liquid temperature to a temperature of 50 ° C to 90 ° C and the amount of the reducing agent to 0.1M to 0.24M.
A deposition rate of μm / hour can be achieved.

The suitable concentration of the reducing agent in the primary plating solution in this method is 0.01 to 0.05, and the solution temperature is 15 to 45 ° C. or lower. The copper compounds used in the first and second inventions of the present application are copper sulfate in both primary and secondary plating,
Sulfates and chlorides such as copper chloride are preferred. The reducing agent is preferably at least one selected from aldehydes, hypophosphites, borohydrides, and hydrazine, and formaldehyde is particularly preferable. This is because ions do not remain and migration of the printed wiring board can be prevented.

The pH adjusting agent used in the first and second groups of the present invention is at least one selected from sodium hydroxide, potassium hydroxide and calcium hydroxide for both primary and secondary plating, and is a basic compound. is there. This is because the trialkanolamine forms a complex under basic conditions.

Next, a method of manufacturing the printed wiring board will be described. The invention according to the first group is a method for manufacturing a printed wiring board, wherein a primary circuit is formed on a substrate and then a secondary circuit is formed on the primary plated film to form a conductor circuit. In addition to using the above-mentioned electroless plating solution, as the secondary plating, an electroless plating solution containing a trialkanolamine, a copper compound, a reducing agent, and a pH adjusting agent is used.

The invention according to the second group is a method for manufacturing a printed wiring board, wherein a primary circuit is formed on a substrate and then a secondary circuit is formed on the primary plated film to form a conductor circuit. The plating bath for plating uses the electroless plating solution of the second group and has a deposition rate of 2 μm.
/ Hour or less, and the secondary plating uses a trialkanolamine, an electroless plating solution containing a copper compound, a reducing agent, and a pH adjusting agent, and the deposition rate is 5 μm.
A method of manufacturing a printed wiring board, characterized in that the printed wiring board has a speed of at least m / hour.

The actions and effects of these manufacturing methods are
It is the same as that described in the above electroless plating method. In addition, compounds of each element used, reducing agent, pH
The conditions such as the preparation agent and the concentration are based on those described for the electroless plating solution.

The lower limit of the primary plating is preferably 0.1 μm / hour, and the upper limit of the secondary plating is preferably 10 μm / hour. A method for manufacturing the printed wiring board will be specifically described.

As the substrate, a copper clad laminate is etched to form a copper pattern, or an adhesive layer for electroless plating is formed on a glass epoxy substrate, a polyimide substrate, a ceramic substrate, a metal substrate, etc. and roughened. It is also possible to form a roughened surface and subject it to electroless plating to form a copper pattern.

Then, an adhesive layer for electroless plating is formed on the substrate. It is desirable that the adhesive for electroless plating contains heat-resistant resin particles that have been pre-cured in a heat-resistant resin (heat-resistant resin matrix) that is soluble in acid or oxidant. This is done by stacking the above. The heat-resistant resin particles can be dissolved and removed to form an octopus-shaped anchor.

As the heat-resistant resin particles, a heat-resistant resin powder having an average particle diameter of 10 μm or less, and an average particle diameter of 2 μm
Aggregated particles obtained by aggregating the following heat-resistant resin powders to have an average particle size of 3 times or more the particle size of the particles, heat-resistant powder resin powders having an average particle size of 10 μm or less, and the particles having an average particle size of the particles A mixture with a heat resistant resin powder having a particle diameter of ⅕ or less and 2 μm or less, a heat resistant resin powder having an average particle diameter of 2 μm or less or an inorganic powder on the surface of the heat resistant resin powder having an average particle diameter of 2 μm to 10 μm. It is desirable to be selected from pseudo particles formed by adhering at least one of the above.

Further, as the heat resistant resin matrix,
Photosensitive resin is desirable. This is because the holes for forming via holes can be formed by exposure and development. The heat-resistant resin matrix, epoxy resin, polyimide resin,
A thermosetting resin such as an epoxy acrylate resin or a composite obtained by mixing a thermoplastic resin such as a polyether sulfone with these is desirable, and the heat resistant resin particles include an epoxy resin, an amino resin (melamine resin,
Urea resin, guanamine resin) and the like are preferable.

The solubility of the epoxy resin in an acid or an oxidizing agent can be arbitrarily changed 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 curing agent is easily dissolved in an oxidizing agent. However, what hardened the novolak epoxy resin oligomer with the imidazole type curing agent is difficult to dissolve in the oxidizing agent.

The acids used in the present invention include phosphoric acid, hydrochloric acid, sulfuric acid, or organic acids such as formic acid and acetic acid, and organic acids are particularly desirable. This is because when the roughening treatment is performed, the metal conductor layer exposed from the via hole is unlikely to corrode.

The oxidant is preferably chromic acid or permanganate (eg potassium permanganate). In particular,
When the amino resin is removed by dissolution, it is desirable to perform a roughening treatment alternately with an acid and an oxidizing agent.

Catalyst nuclei are applied to the roughened surface thus formed. The catalyst nucleus is preferably a noble metal ion or colloid, and generally palladium chloride or palladium colloid is used. It is desirable to perform a heat treatment to fix the catalyst nuclei.

Next, a plating resist is applied or laminated in the form of a film, and then exposed and developed to provide a plating resist pattern. Primary plating is performed on a portion where the plating resist is not formed. The primary plating solution is "a compound of an element consisting of at least one selected from cobalt, nickel, gold, silver, tin, lead, boron, and transition elements,
Alternatively, it is an electroless plating solution containing these, a copper compound, a trialkanolamine, a reducing agent, and a pH adjusting agent. Secondary plating is applied to the surface of this primary plating film. The secondary plating is "trialkanolamine, copper compound,
It is desirable to use an "electroless plating solution comprising a reducing agent and a pH adjusting agent". The complexing agents are of the same type, and even if high-speed plating with a trialkanolamine as a complexing agent is used as the secondary plating solution, no precipitation occurs, and catalyst nuclei are newly added to the surface of the primary plating film. It is not necessary to give it to

According to the method for manufacturing a printed wiring board of the invention according to the second group, after the primary plating is applied to the substrate, the primary plating film is subjected to the secondary plating to form a conductor circuit. In the method for manufacturing a wiring board, the plating bath for the primary plating is an electroless plating solution containing a copper compound, a trialkanolamine, a reducing agent of 0.1 M or less, and a pH adjusting agent, or a copper compound, a trialkanolamine, and a reducing agent. It consists of an agent and a pH adjuster, and its liquid temperature is 50 ° C.
The following electroless plating solution is used and its deposition rate is 2
With an electroless plating solution consisting of a trialkanolamine, a copper compound, a reducing agent, and a pH adjusting agent as the secondary plating, the deposition rate is 5 μm or less.
/ It is characterized in that it is more than an hour.

In such a printed wiring board manufacturing method, the deposition rate of the primary plating film is as low as 2 μm / hour or less, the filling rate of the octopus-shaped anchor on the surface of the adhesive layer for electroless plating is high, and the peel strength is high. Further, since the secondary plating rate is 5 μm / hour or more, the conductor circuit can be formed in a short time, which is industrially advantageous. Moreover, since the complexing agents for the primary plating and the secondary plating are of the same type, there is no need for washing with water, and even when immersed in the plating solution,
Since the secondary plating solution is not contaminated, the number of steps can be reduced.

Further, since the primary plating film and the secondary plating film are made of the same copper, it is possible to reduce peeling due to heat cycle at the plating interface. Moreover, since the trialkanolamine does not remain in the conductor circuit, the electrical resistance is low.

Furthermore, not only the copper pattern but also via holes can be formed to manufacture a multilayer printed wiring board.

[0052]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, an embodiment in which the present invention is embodied in an electroless plating method in a manufacturing process of a printed wiring board will be described in detail with reference to FIGS. 1 (a) to 1 (d). (Embodiment 1) In this embodiment, a conductor pattern 8 of a printed wiring board is manufactured by a full additive process. Hereinafter, the process will be described step by step. (1) First, on the glass epoxy plate 1 as a base material,
Apply additive adhesive. The adhesive was prepared as follows.

70 parts by weight of 25% acrylate of a cresol novolac type epoxy resin (Nippon Kayaku molecular weight 2500) dissolved in diethylene glycol dimethyl ether (DMDG), polyether sulfone (PES)
30 parts by weight, imidazole curing agent (manufactured by Shikoku Kasei, trade name: 2E4MZ-CN) 4 parts by weight, caprolactone modified tris (acryloxyethyl) isocyanurate (a product of Toagosei, trade name; Aronix M325) which is a photosensitive monomer
4. 10 parts by weight, 5 parts by weight of benzophenone (manufactured by Kanto Kagaku) as a photoinitiator, 0.5 part by weight of photosensitizer Michler's ketone (manufactured by Kanto Kagaku), and an average particle size of melamine resin particles of 5. After mixing 35 parts by weight of 5 μm and 5 parts by weight of particles having an average particle size of 0.5 μm, NMP was added thereto and the viscosity was adjusted to 200 with a homodisper agitator.
Adjust to 0 CPS and then knead with 3 rolls. (2) After washing and drying the base material 1 that has undergone the plating process, this adhesive solution is applied onto the base material 2 by using a roll coater and left standing in a horizontal state for 20 minutes, and then at 60 ° C. Was dried (prebaked). (3) The wiring board subjected to the treatment of (2) was exposed with an ultrahigh pressure mercury lamp of 300 mj / cm ² . Further, the wiring board was exposed by an ultra-high pressure mercury lamp at about 3000 mj / cm ² and heat-treated at 100 ° C. for 1 hour and then at 150 ° C. for 5 hours (post bake).
By doing so, a resin adhesive layer 2 having a thickness of 50 μm and having an opening corresponding to a photomask film with excellent dimensional accuracy
Was formed.

This adhesive is obtained by dispersing a resin filler which is soluble in the roughening liquid in a resin matrix which is hardly soluble in the roughening liquid such as chromic acid and phosphoric acid.
In this case, a surface roughening treatment with chromic acid, potassium permanganate or the like is then carried out by a conventional method to dissolve the resin filler in the adhesive layer 2.

Specifically, the surface of the interlayer resin insulation layer was immersed in potassium permanganate (KMnO ₄ , 60 g / l) adjusted to pH = 13 at 70 ° C. for 1 minute and then in phosphoric acid for 30 minutes. Is roughened, and as a result, as shown in FIG. 1A, a roughened surface in which a large number of fine anchors 3 are formed on the surface of the adhesive layer 2 is formed.

Next, after providing the catalyst nuclei necessary for the first deposition of the electroless plated metal, a photosensitive resin such as photosensitive epoxy or photosensitive polyimide is applied and exposed and developed.
As a result, as shown in FIG. 1B, the permanent resist 4 partially having the opening 5 is formed on the upper surface of the adhesive layer 2.

Specifically, the following procedure was followed. DM
A cresol novolac type epoxy resin (manufactured by Nippon Kayaku, trade name: EOCN-103S) dissolved in DG (dimethyl glycol dimethyl ether) is sensitized with 25% of the epoxy groups acrylated (molecular weight 400.
0), PES (molecular weight 17,000), imidazole type curing agent (Shikoku Kasei product name 2 PMHZ-PW), photosensitive monomer acrylated isocyanate (Toagosei product name Aronix M215), benzophenone (Kanto Chemical Co., Inc.) as a photoinitiator. , A photosensitizer Michler Ketone (manufactured by Kanto Kagaku), and mixed with NMP with the following composition, and then the viscosity is 3000 cps with a homodisper agitator.
And then kneading with a three-roll mill to obtain a liquid resist.

Resin composition: Photosensitive epoxy / PES / M
325 / BP / MK / imidazole = 70/30/10
/5/0.5/5 This liquid resist is applied on the resin insulation layer of (7) above using a roll coater and dried at 60 ° C. to a thickness of about 3
A 0 μm resist layer was formed. Furthermore, L / S = 50
A mask film on which a conductor circuit pattern of / 50 was drawn was brought into close contact and exposed with an ultrahigh pressure mercury lamp of 1000 mJ / cm ² .

This was spray-developed with triethylene glycol dimethyl ether (DMDG) to form a plating resist having a missing conductor circuit pattern portion on the wiring board. With an ultra-high pressure mercury lamp, 600
Exposure was performed at 0 mJ / cm ² , and heat treatment was performed at 1000 ° C. for 1 hour and then at 150 ° C. for 3 hours.

A permanent resist 4 was formed using this resist resin. Then, after performing a conventionally known plating pretreatment, the opening 5 is subjected to primary plating. Here, as the plating bath for the primary plating, either an electroless nickel plating bath containing TEA as a complexing agent or an electroless copper-nickel alloy plating bath is used.

In this embodiment, an electroless copper-nickel alloy plating bath having the following composition is specifically used as the primary plating. The temperature of the plating bath is 50 ℃
The temperature is 80 ° C., and the plating immersion time is 20 minutes to 120 minutes.

Metal salt: CuSO ₄ .5H ₂ O; 0.6
25 g / l, (1.8 mM) ... NiSO ₄ .6H ₂ O; 12.485 g / l, (51.0 mM) Complexing agent ... TEA; 50 g / l, (0.33
M) reducing agent: Na phosphinate monohydrate; 21.2 g /
Liter, (0.2M) pH adjuster ... NaOH; 30 g / liter, (0.
75M) Others: a small amount of stabilizer (bipyridyl, potassium ferrocyanide, etc.).

As shown in FIG. 1 (c), the deposition rate is about 0.5 μm / hour by performing plating at a rate of 1.5 μm / hour or more. A 5.0 μm copper-nickel-phosphorus plating thin film 6 is formed. After this, glass epoxy board 1
Is removed from the plating bath, and the plating bath adhering to the surface is washed off with water.

Next, the oxide film on the surface layer of the copper-nickel-phosphorus plating thin film 6 is removed by the activation process of treating the glass epoxy plate 1 with an acidic solution. Then, secondary plating is performed on the copper-nickel-phosphorus plating thin film 6 without performing Pd substitution. Here, as the plating bath for secondary plating, an electroless copper plating bath for secondary plating containing TEA as a complexing agent is used.

In this embodiment, a plating bath having the following composition is specifically used as the secondary plating. The temperature of the plating bath is 50 ° C. to 70 ° C., and the plating immersion time is 90 minutes to 360 minutes.

Metal salt ... CuSO ₄ .5H ₂ O; 3.0
g / l, (8.6 mM) Complexing agent ... TEA; 22.5 g / l, (0.1
5M) Reducing agent ... HCHO; 2cc / liter (0.1M) Others. Stabilizer (bipyridyl, potassium ferrocyanide, etc.) in a small amount.

Deposition rate is 6 μm / hour. The thickness of the entire plating film is 30 μm. If the primary plating film is 2 μm, the average deposition rate of primary plating and secondary plating is 5.0 μm / hour.

The average deposition time = total plating film thickness / (primary plating film thickness / primary plating film deposition rate + secondary plating film thickness / secondary plating film deposition rate). 30 μm / {(2 / 1.5) hours + (28/6) hours} = 30 μm / 6 hours = 5 μm / hour This is the deposition rate when only the copper plating solution using EDTA as a complexing agent was used. Faster than 2.0 μm / hour.

By performing the plating under the above conditions,
As shown in FIG. 1D, the primary plating film of copper-
A copper plating film 7 is formed on the surface of the nickel plating thin film 6. Therefore, the conductor pattern 8 including two kinds of metal layers is obtained.

The thickness of the two types of metal layers is 0.5 to 3 μm for the primary plating layer and 10 to 30 μm for the secondary plating layer.
m, and secondary plating layer / primary plating layer = 3.3 to 60
The range of is desirable. When the primary plating layer becomes too large, peeling occurs at the interface between the primary plating film and the secondary plating film, and when the primary plating film is too small, the peel strength decreases.

In the electroless plating method of the present embodiment, the complexing agent contained in the plating bath for primary plating,
The complexing agent contained in the plating bath for secondary plating is the same, that is, TEA. Therefore, the compatibility between the copper-nickel-phosphorus plating thin film 6 in contact with the roughened surface of the adhesive layer for electroless plating and the copper plating deposited thereon is
It is thought that it will improve compared to when using an EDTA bath,
According to this combination, the wettability between the copper-nickel-phosphorus plating thin film 6 and the secondary plating solution is improved, and the copper plating is easily deposited on the wettability. Therefore, the initial reaction of plating does not stop midway, and the copper plating film 7 is reliably and smoothly formed.

Therefore, according to this electroless plating method,
Since it is unnecessary to replace Pd with the primary plating film, which has been indispensable in the past, the cost can be surely reduced accordingly. Moreover, P from the copper-nickel-phosphorus plating thin film 6
Since the problem of falling off of d cannot occur, the situation of abnormal deposition of plated metal can be solved. Further, there is an advantage that storage and management of the processing liquid for Pd substitution are unnecessary.

Further, since the above two plating baths contain the same type of complexing agent, there is no problem such as contamination of the plating baths even if they are mixed with each other. That is, early deterioration of the electroless copper plating bath for the secondary plating is avoided, and cleaning between the primary plating and the secondary plating can be omitted.

The peel strength of the conductor pattern 8 formed under the above-mentioned conditions was measured and found to be 1.8 kg / cm, which was acceptable for practical use. The peel strength was measured according to JIS-C-6481. (Embodiment 2) Basically, the same as in Embodiment 1, but the following nickel plating solution, cobalt plating solution, and mixed plating solution of copper and cobalt were used as the primary plating solution.

(Nickel plating solution) Plating temperature 60 ° C. Metal salt ... NiSO ₄ .6H ₂ O; 13.5 g / liter, (55.2 mM) Complexing agent ... TEA; 50 g / liter, (0.33
M) reducing agent: Na phosphinate monohydrate; 21.2 g /
Liter, (0.2M) pH adjuster ... NaOH; 30 g / liter, (0.
75M) Others: a small amount of stabilizer (bipyridyl, potassium ferrocyanide, etc.).

The average deposition rate is 1.5 μm / hour (cobalt plating solution) Plating temperature 60 ° C. Metal salt ... CoCl ₂ .6H ₂ O; 55.0 mM Complexing agent ... TEA; 0.3 M Reducing agent ... Phosphinic acid Na monohydrate; 0.2M pH adjuster ... NaOH; 0.75M Other ... Stabilizers (bipyridyl, potassium ferrocyanide, etc.) in small amounts.

The average deposition rate is 1.5 μm / hour (Cobalt-copper composite plating solution) Plating temperature 60 ° C. Metal salt ... CoCl ₂ .6H ₂ O; 25.0 mM CuSO ₄ .5H ₂ O; 30.0 mM Complexation Agent: TEA; 0.3 M Reducing agent: Sodium hydroxide borate; 0.2 M pH adjusting agent: NaOH; 0.75 M Others: Stabilizer (bipyridyl, potassium ferrocyanide, etc.) in a small amount.

The deposition rate was 1.0 μm / hour. When peel strength was measured, the values were 1.6 kg / cm for nickel plating and 1.6 kg / c for cobalt plating.
m and copper-cobalt plating was 1.7 kg / cm. Further, as a comparative example, when plating was directly performed with a plating bath containing TEA, the deposition rate was 6 μm.
Although it is m / hour, its peel strength is 0.8 kg /
It was as low as cm. (Embodiment 3) Basically, the same as in Embodiment 1, but the following compositions were used as the primary and secondary plating solutions.

(TEA low speed plating) Plating temperature is 40 ° C., metal salt: CuSO ₄ .5H ₂ O; 1.8 mM complexing agent: TEA; 0.33M reducing agent: formaldehyde: 0.05M pH adjusting agent: NaOH 0.5 M Others. Stabilizers (bipyridyl, potassium ferrocyanide, etc.) in small amounts.

The deposition rate was 1 μm / hour (TEA high-speed plating). The secondary plating solution having the following composition was used.

Plating temperature is 60 ° C., metal salt: CuSO ₄ .5H ₂ O; 1.8 mM complexing agent: TEA; 0.33M reducing agent: formaldehyde: 1.5M pH adjusting agent: NaOH; 0.5M and others ... Stabilizers (bipyridyl, potassium ferrocyanide, etc.) in small amounts.

The deposition rate is 6 μm / hour, and the average deposition rate for a thickness of 30 μm is 4.5 μm / hour. When the peel strength was measured, the value was 1.4 kg.
The value was / cm.

As a comparative example, primary plating was carried out with a plating solution containing EDTA as a complexing agent and immersed in a secondary plating solution containing TEA as a complexing agent, but no precipitation reaction occurred.

(Embodiment 4) Gold, silver, tin, lead, boron,
Electroless plating solutions were prepared for compounds of at least one element selected from transition elements, and electroless plating was performed. Used metal compounds, reducing agents, pH adjusters,
The results of the deposition rate and the peel strength are shown in Table 1.

Further, an electroless plating solution was prepared for a mixture of a compound of at least one element selected from gold, silver, tin, lead, boron, and transition elements and a copper compound, and electroless plating was performed. Used metal compound, reducing agent, p
The results are shown in Table 2 for the H modifier, the deposition rate, and the peel strength.

[0086]

[Table 1]

[0087]

[Table 2] The conditions of the secondary plating are the same as those of the first embodiment. As described above, under the conditions of the embodiment, it is found that the conductor pattern 8 has a sufficient peel strength for each. This is because the roughened surface is filled with high-strength alloy plating, and even in the case of a TEA-containing plating bath, if the plating bath is the low-speed plating bath, the fillability of the anchor 3 is comparable. Presumed to be. Also,
It can be seen that the electroless nickel plating bath has a larger peel strength than the electroless copper plating bath and the electroless copper-nickel (-phosphorus) alloy plating bath has a larger peel strength than the electroless nickel plating bath. This means that the alloy is stronger than the elemental metal, and thus metal breakage is less likely to occur.

The present invention can be modified as follows, for example. (1) The complexing agent in the electroless primary plating bath may be changed to monoethanolamine or diethanolamine which is an ethanolamine like TEA.

(2) If TEA is contained as a complexing agent, a secondary electroless copper plating bath having a composition different from that exemplified in the embodiment may be used. (3) Instead of the embodiment, electroless plating may be performed by the following procedure, for example. First, primary plating is performed using a primary electroless plating bath. Then, the base material is pulled out from the plating bath, and the base material is directly immersed in the secondary electroless copper plating bath without washing with water or drying. in this case,
In order to prevent the formation of an oxide film, the transfer from the primary electroless plating bath to the secondary electroless copper plating bath needs to be performed quickly. With the above method, the activation process for removing the oxide film is not necessary, and the process is further simplified. Further, if not limited to this method, the activation treatment can be omitted as long as a series of plating processes are performed under conditions where an oxide film is difficult to form.

(4) The electroless plating method of the present invention is not limited to the manufacturing process of a printed wiring board, but can be applied to other uses such as surface plating of automobile parts.

[0091]

As described above in detail, according to the present invention, even when the average plating deposition rate is improved, the peel strength of the conductor pattern obtained is not lowered, and the Pd substitution before the secondary plating is performed. The need for can be eliminated. Also, the average plating deposition rate can be improved.

[Brief description of drawings]

1A to 1D are partial schematic cross-sectional views showing an electroless plating method according to an embodiment.

[Explanation of symbols]

1 ... A glass epoxy plate as a base material, 6 ... a copper-nickel-phosphorus plating thin film as a primary plating film.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical indication C23C 18/52 B H05K 3/18 F 7511-4E

Claims (12)

[Claims] 1. Cobalt, nickel, gold, silver, tin,
An electroless plating solution comprising a compound of at least one element selected from lead, boron, and transition elements, or a copper compound with these, a trialkanolamine, a reducing agent, and a pH adjusting agent. 2. A copper compound, a trialkanolamine,
An electroless plating solution comprising a reducing agent of 0.1 M or less and a pH adjusting agent. 3. An electroless plating solution comprising a copper compound, a trialkanolamine, a reducing agent, and a pH adjusting agent, the solution temperature of which is 50 ° C. or lower. 4. The electroless plating solution comprises a copper compound, a nickel compound or a cobalt compound, a trialkanolamine, a reducing agent and a pH adjuster, and the concentration of the copper compound is 1.0 to 4.3 mM, nickel. The electroless plating solution according to claim 1, wherein the concentration of the compound or the cobalt compound is 20 to 82 mM, and the concentration of the trialkanolamine is 0.1 to 0.8M. 5. The electroless material according to claim 1, wherein the trialkanolamine is at least one selected from triethanolamine, triisopropanolamine, trimethanolamine and tripropanolamine. Plating solution. 6. The electroless plating solution according to claim 1, wherein the reducing agent is at least one selected from aldehyde, hypophosphite, borohydride and hydrazine. 7. The electroless plating solution according to claim 1, wherein the electroless plating solution contains an iron compound and / or bipyridyl. 8. The pH adjusting agent is sodium hydroxide,
The electroless plating solution according to claim 1, which is at least one selected from potassium hydroxide and calcium hydroxide. 9. An electroless plating method in which primary plating is applied to a substrate and then secondary plating is performed on the primary plating film, wherein the plating bath for primary plating is any one of claims 1 to 8. An electroless plating solution comprising one electroless plating solution and a trialkanolamine, a copper compound, a reducing agent and a pH adjuster as a plating bath for secondary plating. Plating method. 10. An electroless plating method in which primary plating is applied to a substrate and then secondary plating is performed on the primary plating film, wherein the plating bath for the primary plating is the plating bath according to claim 2 or 3. An electrolytic plating solution was used to control the deposition rate to 2 μm / hour or less, and as a plating bath for secondary plating,
An electroless plating method characterized in that an electroless plating solution comprising a trialkanolamine, a copper compound, a reducing agent and a pH adjuster is used and the deposition rate thereof is 5 μm / hour or more. 11. A method of manufacturing a printed wiring board, comprising: performing a primary plating on a substrate and then performing a secondary plating on the primary plating film to form a conductor circuit; wherein the plating bath for the primary plating is In addition to using the electroless plating solution according to any one of Items 1 to 8, use an electroless plating solution containing a trialkanolamine, a copper compound, a reducing agent, and a pH adjuster as a plating bath for secondary plating A method for manufacturing a printed wiring board, comprising: 12. A method of manufacturing a printed wiring board, comprising: performing a primary plating on a substrate and then performing a secondary plating on the primary plating film to form a conductor circuit; wherein the plating bath for the primary plating is Using the electroless plating solution according to Item 2 or 3, the deposition rate is set to 2 μm / hour or less, and a plating bath for secondary plating is used.
A method for producing a printed wiring board, characterized in that an electroless plating solution comprising a trialkanolamine, a copper compound, a reducing agent and a pH adjusting agent is used and the deposition rate thereof is 5 μm / hour or more.