JPH10298771A - Electroless nickel plating method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electroless nickel plating method that is a electroless nickel plating method of forming a resist film on the surface of an org. substrate having conductor circuits on the surface on the side having these conductor circuits, then immersing the substrate into an electroless nickel plating liquid to form nickel plating films, and that can avoid the formation of the parts not forming nickel plating films. SOLUTION: In this method for forming nickel plating films on the surfaces of the conductor circuits 11, the conductor circuits 11 are immersed into the first electroless nickel plating liquid 35 to form the first nickel plating film 30 on the surfaces of the conductor circuits 11 and thereafter, the conductor circuits are immersed into the second electroless nickel plating liquid 36 of the deposition rate of nickel higher than that of the first electroless nickel plating liquid 35, by which the second nickel plating films 31 are formed on the surfaces of the first nickel plating films 30.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for electroless nickel plating which is performed during the manufacture of a printed wiring board.

[0002]

2. Description of the Related Art As a printed wiring board used for electric and electronic equipment, the purpose is to improve the adhesion of solder to improve the reliability of mounting electronic components, and to provide the connection reliability of inserting and contacting a connector. For the purpose of enhancing
2. Description of the Related Art A printed wiring board having a conductor circuit having a gold plating film formed on a surface is used.

A printed wiring board having a conductor circuit having a gold plating film formed on its surface is manufactured by, for example, the following steps. Fig. 2
An organic substrate 10 having a copper foil layer 12 on the surface as shown in FIG. Then, as shown in FIG. 2B, after forming a resist film 25 for etching on the surface of the substrate 10 where a conductive circuit is to be formed, the copper foil layer 12 not covered with the resist film 25 is formed. Is etched to form a copper conductive circuit 11 as shown in FIG.

Then, after the resist film 25 is peeled to expose the copper conductive circuit 11, as shown in FIG. 2 (d), a portion of the substrate 1 where a gold plating film is not to be formed is to be formed.
On the zero surface, a plating resist film 20 is formed.

[0005] Next, as shown in FIG. 2 (e), in order to stabilize the deposition property of the gold plating, the surface of the copper conductive circuit 11 not covered with the plating resist film 20 is subjected to electroless nickel plating. , Nickel plating film 50
To form Subsequently, the electroless gold plating is performed to form a gold plating film 60 on the surface of the nickel plating film 50.

Incidentally, as a method of electroless nickel plating or displacement electroless gold plating, generally, a method of immersing the substrate 10 in an electroless nickel plating solution or a gold plating solution is used. In addition, since the substitutional electroless gold plating is a plating in which the gold plating film 60 is formed by replacing a part or all of the nickel plating film 50, the quality of the formation of the nickel plating film 50 depends on the rotation of the gold plating film 60 as it is. This is plating that affects the properties.

Since the thickness of the plating resist film 20 is generally thicker than the thickness of the copper conductive circuit 11, when the nickel plating film 50 is to be formed, the thickness of the resist film 20 is as shown in FIG. Shown is a resist film 20 for plating.
The electroless nickel plating solution is stirred or the substrate 10 is swung so that a highly active portion of the electroless nickel plating solution is supplied to the bottom surface of the concave portion 21 formed by the copper conductive circuit 11 and the like. Thus, a nickel plating film 50 is formed.

With the recent high-density mounting of printed wiring boards, the conductor circuits 11 for signals, lands and the like also tend to be reduced in width and diameter. Therefore, the size of the portion where the nickel plating film 50 or the gold plating film 60 is to be formed is also reduced, and the opening of the concave portion 21 formed by the plating resist film 20 or the like is formed in the portion where the nickel plating film 50 is to be formed. Also tends to be smaller.

In general, electroless nickel plating generates hydrogen gas by a chemical reaction when nickel is deposited. In the case of the concave portion 21 having a small opening as described above, even if the electroless nickel plating solution is agitated or the substrate 10 is swung, the supply of the plating solution to the inner portion of the concave portion is performed. As shown in FIG. 3, the amount of hydrogen gas bubbles 70 that are stuck to the wall surface of the concave portion 21 or the surface of the conductor circuit 11 and do not move is easily formed.

The supply of the electroless nickel plating solution 55 becomes particularly small in the portion where the hydrogen gas bubbles 70 adhere, and an unformed portion of the nickel plating film generally called a skip is generated. The gold plating film formed on the surface also has an unformed portion, which causes a problem that the connection reliability of the obtained printed wiring board may be reduced. Therefore, a method of electroless nickel plating in which an unformed portion of the nickel plating film hardly occurs is desired.

[0011]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide an organic substrate having a conductor circuit on a surface thereof. This is an electroless nickel plating method in which a resist film is formed on the surface on the side and then immersed in an electroless nickel plating solution to form a nickel plating film. It is to provide a method.

[0012]

According to a first aspect of the present invention, there is provided an electroless nickel plating method comprising the steps of: forming a resist film on an organic substrate having a conductive circuit on the surface thereof; In an electroless nickel plating method of immersing in an electroless nickel plating solution and forming a nickel plating film on the surface of a conductor circuit in contact with the electroless nickel plating solution, a method of forming a nickel plating film on the surface of the conductor circuit includes: A conductor circuit is immersed in a first electroless nickel plating solution to form a first nickel plating film on the surface of the conductor circuit, and then a second nickel plating speed is higher than the first electroless nickel plating solution. Dipping in an electroless nickel plating solution to form a second nickel plating film on the surface of the first nickel plating film.

[0013] In the electroless nickel plating method according to the second aspect of the present invention, in the electroless nickel plating method according to the first aspect, the second electroless nickel plating solution may be formed from the first electroless nickel plating solution. It is characterized by a high temperature liquid.

According to a third aspect of the present invention, there is provided the electroless nickel plating method according to the first aspect, wherein the second electroless nickel plating solution is different from the first electroless nickel plating solution. The liquid is characterized by a high concentration of the nickel compound and the reducing agent.

According to a fourth aspect of the present invention, there is provided the electroless nickel plating method according to any one of the first to third aspects, wherein the first nickel plating film has a thickness of 0.1 mm. 1 to 2 μm.

According to the present invention, after a first nickel plating film is formed on a surface of a conductor circuit in advance with a first electroless nickel plating solution having a low nickel deposition rate, the first electroless nickel plating solution is applied. To form a second nickel plating film on the surface of the first nickel plating film with a second electroless nickel plating solution having a high nickel deposition rate, the nickel deposition rate of the first electroless nickel plating solution is If it is performed at such a speed that hydrogen gas bubbles are hardly generated,
The first nickel plating film is formed on almost the entire surface of the conductor circuit, and even when bubbles of hydrogen gas adhere to the surface of the first nickel plating film in the second electroless nickel plating solution, The minimum thickness of the nickel plating film can be ensured, and the unformed portion of the nickel plating film hardly occurs.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An electroless nickel plating method according to the present invention will be described with reference to the drawings. FIG. 1 is a process diagram illustrating one embodiment of the electroless nickel plating method according to the present invention.

In the electroless nickel plating method according to the present invention, a resist film is formed on the surface of an organic substrate having a conductor circuit on the surface having the conductor circuit, and then dipped in an electroless nickel plating solution. This is an electroless nickel plating method in which a nickel plating film is formed on the surface of a conductor circuit that comes into contact with an electroless nickel plating solution.

FIG. 1 shows the manufacturing process.
A substrate 10 having a conductor circuit 11 on the surface as shown in FIG. Then, a plating resist film 20 is formed on the surface of the substrate 10 where the gold plating film is not to be formed on the side having the conductor circuit 11.

The substrate 10 used in the present invention comprises a conductor circuit 11
An organic board having a surface on which a metal foil such as a copper foil is stretched on one or both sides of a sheet of the thermosetting resin composition, an inorganic fiber such as glass or polyester, polyamide, cotton, etc. Organic fiber cloth, a base material such as paper is adhered with a thermosetting resin composition, and a metal foil such as a copper foil is stretched on one or both sides, and the metal foil on the surface is etched. A conductor circuit 11 is formed, and
A metal plate such as copper plating is formed on the surface of a similar plate on which no metal foil is provided, and a conductor circuit 11 is formed.

The inside of the substrate 10 may have a conductor circuit or a hole provided with a metal film on the wall surface thereof. In addition, as the thermosetting resin composition, for example, a thermosetting resin such as an epoxy resin type, a phenol resin type, a polyimide resin type, an unsaturated polyester resin type, a polyphenylene ether resin type, and the like; And a resin composition in which an inorganic filler or the like is blended. Examples of the metal forming the conductor circuit 11 include copper and stainless steel, and copper is preferable from the viewpoint of electrical reliability.

The plating resist film 20 used in the present invention
The resist is cured by UV light irradiation or heating to form a film that can withstand electroless nickel plating. As a method of forming the plating resist film 20, a non-cured resist resin is selectively applied to the surface of the substrate 10 where a nickel plating film is not to be formed by a printing method or the like, and then UV light irradiation is performed. Or, a method of forming by curing by heating, or applying an uncured resist resin on the entire surface of the substrate 10 or thermocompression bonding, and then irradiating only the portions where the nickel plating film is not to be formed with UV light and curing, Next, a method of forming by removing an uncured portion which has not been irradiated with UV light, or the like can be given.

The plating resist film 20 is
It may be removed in a later step and not remain when the printed wiring board is completed, or may be left when the printed wiring board is completed as generally called a solder resist. The thickness of the plating resist film 20 is not particularly limited, but is generally about 30 to 200 μm.

Next, if necessary, the surface of the conductor circuit 11 on which the nickel plating film is to be formed is cleaned by performing degreasing, soft etching, or the like. Next, the conductor circuit 1
After applying a catalyst for electroless nickel plating to the surface of 1, the catalyst is activated.

Next, as shown in FIG. 1B, the substrate 10 having the conductor circuit 11 on the surface is immersed in a first electroless nickel plating solution 35, and the first nickel After the plating film 30 is formed, as shown in FIG. 1C, the plating film 30 is immersed in a second electroless nickel plating solution 36 to coat the second nickel plating film 31 on the surface of the first nickel plating film 30. Form.

The first electroless nickel plating solution 35 and the second electroless nickel plating solution 36 used in the present invention contain nickel sulfate, nickel chloride or the like as a nickel compound, and sodium hypophosphite as a reducing agent. An acidic type aqueous solution containing, and a similar nickel compound,
Examples of the reducing agent include an ammonia-alkali type aqueous solution and a caustic alkali-type aqueous solution containing sodium hypophosphite and sodium borohydride.

The second electroless nickel plating solution 36
It is important that the deposition rate of nickel is higher than that of the first electroless nickel plating solution 35. The deposition rate of nickel of the second electroless nickel plating solution 36 is the same as the deposition speed of nickel of the first electroless nickel plating solution 35,
Or, in the case of a slow speed, bubbles of hydrogen gas are likely to be generated in the first electroless nickel plating solution 35, and the bubbles of hydrogen gas adhere to the surface of the conductor circuit 11 and the like, and the nickel plating film (30, 31) is formed. ) May easily occur, or the speed at which the nickel plating films (30, 31) are formed may be reduced, resulting in reduced productivity.

The first electroless nickel plating solution 35
The nickel is deposited at a rate lower than that of a conventional electroless nickel plating solution, in which bubbles of hydrogen gas are hardly generated. Further, the deposition rate of nickel of the second electroless nickel plating solution 36 is not particularly limited as long as the deposition rate of nickel is higher than that of the first electroless nickel plating solution 35. The speed may be approximately the same as or higher than that in the case of using a nickel plating solution.

As a method of making the deposition rate of nickel of the second electroless nickel plating solution 36 faster than the deposition rate of nickel of the first electroless nickel plating solution 35,
Using an electroless nickel plating solution of the same composition, a method of changing the deposition rate by changing the temperature, and a method of changing the deposition rate by using an electroless nickel plating solution of the same temperature with a changed composition, And a method of changing the deposition rate using an electroless nickel plating solution having a changed temperature.

The first electroless nickel plating solution 35
And the second electroless nickel plating solution 36 having the same composition, if the temperature is high, the deposition rate of nickel is high. The liquid 36 has a higher temperature than the first electroless nickel plating liquid 35.

The first electroless nickel plating solution 35
When the second electroless nickel plating solution 36 is at the same temperature, if the concentration of the nickel compound and the reducing agent contained is high, the deposition rate of nickel is high. The second electroless nickel plating solution 36 has a higher concentration of a nickel compound and a reducing agent than the first electroless nickel plating solution 35.

In the method of changing the deposition rate by changing the composition, the first electroless nickel plating solution 35
And the second electroless nickel plating solution 36 also contains a compound other than a nickel compound and a reducing agent that affects the deposition rate of nickel, the concentration of which is changed at the same time, the nickel deposition Although the rate is stable and preferable, the content that does not affect the nickel deposition rate may or may not be changed. If the deposition rate of nickel can be changed by changing the concentration of the content other than the nickel compound and the reducing agent, the deposition rate is affected without changing the concentration of the nickel compound and the reducing agent. Change the concentration of the ingredients,
The deposition rate of nickel may be changed.

The thickness of the first nickel plating film 30 to be formed is preferably 0.1 to 2 μm. 0.
If the thickness is less than 1 μm, a portion where the first nickel plating film 30 is not formed may occur due to in-plane variation, so that when immersed in the second electroless nickel plating solution 36, the first nickel plating film 30 There is a case where hydrogen gas bubbles adhere to the surface of the part where no nickel plating film is formed, so that the second nickel plating film 31 is not formed, and an unformed portion of the nickel plating film (30, 31) is formed. Further, even if the thickness exceeds 2 μm, there is no difference in the effect of making it difficult to form the unformed portion of the nickel plating film (30, 31), which is not economical.

After immersion in the first electroless nickel plating solution to form a first nickel plating film on the surface of the conductor circuit, immersion in the second electroless nickel plating solution, A second nickel plating film was formed on the surface of the nickel plating film, and then immersed again in the first electroless nickel plating solution to form a third nickel plating film on the surface of the second nickel plating film. After that, it is immersed again in the second electroless nickel plating solution, and immersed in the first electroless nickel plating solution as in the case of forming the fourth nickel plating film on the surface of the third nickel plating film. When the immersion in the second electroless nickel plating solution is defined as one cycle and the cycle is repeated a plurality of times, the immersion is performed so that the total time becomes the same (for example, 1/20 cycle and 1/40 cycle). If, even in 2 cycles) 10 minutes and 20 minutes, preferably it particularly hard to occur is not formed part of the nickel plating film.

[0035]

【Example】

(Examples 1 to 9) Copper foil thickness 35 μm, thickness of insulating portion 1.
Using a 2 mm epoxy resin double-sided copper-clad laminate [product name: R1766, manufactured by Matsushita Electric Works Co., Ltd.], the copper foil on the surface is etched to form a substrate having 3000 land-like conductor circuits having a diameter of 140 μm on one surface. Formed. Next, an alkali-developable liquid resist (manufactured by Tamura Kaken Co., Ltd.) is applied to the surface of the substrate on which the land-shaped conductor circuits are formed by a curtain coating method, and then dried, and the entire surface of the surface is uncured. A resist film for plating was formed.

Next, the portion excluding the portion where the land-shaped conductor circuit is formed and its surroundings is irradiated with UV light to be cured, then the uncured portion is developed, and the land-shaped conductor circuit is exposed on the bottom surface. A 180 μm diameter concave portion formed of a plating resist film or the like was formed in each of the land-shaped conductor circuits.

Next, as a pretreatment for nickel plating,
Degreasing, soft etching, acid washing, pre-dipping, catalyst application and catalyst activation were performed by the following methods. For degreasing,
Performed at room temperature for 5 minutes using Atotech degreasing solution [trade name: acidic cleaner], soft etching was performed for 30 seconds using a room temperature World Metal soft etching solution, and acid cleaning was performed using 98% sulfuric acid [reagent]. For 3 minutes using an aqueous solution at room temperature containing 1% by volume of
% Aqueous hydrochloric acid [reagent] is used for 30 seconds using an aqueous solution containing 10% by volume of room temperature, and the catalyst is applied at 60 ° C., a catalyst for electroless nickel plating [trade name AT-90, manufactured by World Metal Corporation].
The catalyst is activated by 98% sulfuric acid [reagent].
For 1 minute using an aqueous solution at room temperature containing 1% by volume.

Next, the substrate was immersed in the first electroless nickel plating solution at the temperature shown in Table 1 for 20 minutes to form a first nickel plating film on the surface of the conductor circuit. The first electroless nickel plating solution has a standard concentration of an aqueous solution containing 20% by volume of an electroless nickel plating solution [trade name: Linden 202-0] manufactured by World Metal Co., and its standard concentration, 1/2 of the standard concentration, Liquids bathed at a composition of 1/3 of the standard concentration and 1/5 of the standard concentration were used in Examples shown in Table 1.

Next, a bath was prepared with the composition having the above standard concentration.
By immersing in a second electroless nickel plating solution at 0 ° C. for 40 minutes to form a second nickel plating film on the surface of the first nickel plating film,
A nickel plating film (first and second total) was formed.

The thickness of the formed first nickel plating film was measured with an electron microscope by observing a cross section.
The thickness was as shown in FIG. In addition, instead of the first electroless nickel plating solution, the above-mentioned second electroless nickel plating solution at 80 ° C. was immersed for 20 minutes to form a nickel plating film on the surface of the conductor circuit. When the thickness of the nickel plating film was measured in the same manner, it was 2.2 μm. In each of the examples, the deposition rate of nickel of the second electroless nickel plating solution was less than that of the first electroless nickel plating solution. It was confirmed that the deposition rate was higher than the deposition rate.

[0041]

[Table 1]

Example 10 After immersion in a first electroless nickel plating solution for 10 minutes to form a first nickel plating film on the surface of a conductor circuit, the substrate was immersed in a second electroless nickel plating solution for 20 minutes. Immersion to form a second nickel plating film on the surface of the first nickel plating film, and then immersing again in the first electroless nickel plating solution for 10 minutes, Example 2 except that after forming the third nickel plating film, it was immersed again in the second electroless nickel plating solution for 20 minutes to form the fourth nickel plating film on the surface of the third nickel plating film. 1
Similarly, a nickel plating film (first to fourth) was formed on the surface of the conductor circuit.

Example 11 After immersion in a first electroless nickel plating solution for 10 minutes to form a first nickel plating film on the surface of a conductor circuit, the substrate was immersed in a second electroless nickel plating solution for 20 minutes. Immersion to form a second nickel plating film on the surface of the first nickel plating film, and then immersing again in the first electroless nickel plating solution for 10 minutes, Example 2 except that after forming the third nickel plating film, it was immersed again in the second electroless nickel plating solution for 20 minutes to form the fourth nickel plating film on the surface of the third nickel plating film. 6
Similarly, a nickel plating film (first to fourth) was formed on the surface of the conductor circuit.

Comparative Example Without immersion in the first electroless nickel plating solution, immersion in the second electroless nickel plating solution at 80 ° C. for 60 minutes to form a second nickel plating on the surface of the conductor circuit A nickel plating film (second only) was formed on the surface of the conductor circuit in the same manner as in Example 1 except that the film was formed directly.

(Evaluation and Results) The throwing power of the nickel plating films obtained in each of Examples and Comparative Examples was evaluated. The method is as follows. After immersing in a replacement metal electroless gold plating solution [trade name: MN-AUA] manufactured by World Metal Co.
World Metal Co. thick electroless gold plating [Product name G
OLD-8] for 10 minutes to form a gold-plated film on the surface of the nickel-plated film. Observe the 3000 land-shaped conductor circuits with a microscope. The case where it was not formed was rejected, and the number of passed samples was counted.

As a result, as shown in Table 1, it was confirmed that in each of the examples, the ratio of the gold plating was higher than that of the comparative example, and the unformed portion of the nickel plating film was hardly generated. . Further, in Examples 2 to 5 and 7 to 9 in which the thickness of the first nickel plating film was in the range of 0.1 to 2 μm, the thickness of the nickel plating film was particularly small compared to Examples 1 and 6. It was confirmed that a formed portion was hardly generated. Examples 10 and 11 in which the cycle of immersion in the first electroless nickel plating solution and the cycle of immersion in the second electroless nickel plating solution were repeated twice were particularly advantageous in comparison with Examples 1 to 9, It was confirmed that an unformed portion of the plating film was hardly generated.

[0047]

According to the electroless nickel plating method of the present invention, immersion in the first electroless nickel plating solution
After the first nickel plating film is formed on the surface of the conductor circuit, the first nickel plating solution is immersed in a second electroless nickel plating solution having a higher nickel deposition rate than the first electroless nickel plating solution. Since the second nickel plating film is formed on the surface of the film, an unformed portion of the nickel plating film hardly occurs.

[Brief description of the drawings]

FIG. 1 is a process diagram illustrating an embodiment of an electroless nickel plating method according to the present invention.

FIG. 2 is a process diagram illustrating a conventional electroless nickel plating method.

FIG. 3 is a diagram illustrating a part of the steps of a conventional electroless nickel plating method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Substrate 11 Conductor circuit 12 Copper foil layer 20 Plating resist film 21 Concave part 25 Etching resist film 30 First nickel plating film 31 Second nickel plating film 35 First electroless nickel plating solution 36 Second electroless Nickel plating solution 50 Nickel plating film 55 Electroless nickel plating solution 60 Gold plating film 70 Hydrogen gas bubble

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Shoichi Fujimori 1048 Kadoma Kadoma, Osaka Prefecture Matsushita Electric Works, Ltd. (72) Inventor Hiroaki Fujiwara 1048 Kadoma Kadoma, Kadoma City, Osaka Prefecture, Japan Inside Matsushita Electric Works Co., Ltd. Matsushita Electric Works Co., Ltd., 1048, Kazuma, Kadoma-shi (72) Inventor Yoshihiro Nakagawa 1048 Kadoma, Kazuma, Kadoma, Osaka, Japan Within Denko Corporation

Claims (4)

[Claims] 1. An organic substrate having a conductive circuit on its surface,
After forming a resist film on the surface having the conductor circuit, immersed in an electroless nickel plating solution, the electroless nickel plating method of forming a nickel plating film on the surface of the conductor circuit in contact with the electroless nickel plating solution. , A method of forming a nickel plating film on the surface of a conductor circuit,
Immerse the conductor circuit in the first electroless nickel plating solution,
After the first nickel plating film is formed on the surface of the conductor circuit, the first nickel plating solution is immersed in a second electroless nickel plating solution having a higher nickel deposition rate than the first electroless nickel plating solution. An electroless nickel plating method, which comprises forming a second nickel plating film on the surface of the film. 2. The electroless nickel plating method according to claim 1, wherein the second electroless nickel plating solution has a higher temperature than the first electroless nickel plating solution. 3. The electroless nickel according to claim 1, wherein the second electroless nickel plating solution has a higher concentration of a nickel compound and a reducing agent than the first electroless nickel plating solution. Plating method. 4. The thickness of the first nickel plating film is:
The electroless nickel plating method according to claim 1, wherein the thickness is 0.1 to 2 μm.