JP2003213440A - Method of controlling electroless nickel plating solution - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of controlling an electroless nickel plating solution by which the content of sulfur compounds in an electroless nickel plating solution can be controlled within an optional range with a simple means, and stable performances can be maintained over a long period as to the precipitation properties of the electroless nickel plating solution and the appearance of a plating film. <P>SOLUTION: In the method of controlling an electroless nickel plating solution containing hypophosphite as a reducing agent, the amount of an electroless nickel plating film formed by using the same electroless nickel plating solution to be magnetized is measured, and, based on the measured result of the amount to be magnetized, the content of sulfur compounds in the electroless nickel plating solution is controlled. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for controlling an electroless nickel plating solution containing hypophosphite as a reducing agent.

[0002]

2. Description of the Related Art In electroless nickel plating solutions for circuit patterns of electronic devices which have been widely used recently, sulfur compounds may be added for the purpose of preventing bridges and promoting precipitation. For example, JP-A-8-269726 discloses a compound having an S—S sulfur bond such as thiosulfate, dithionate, polythionate, and dithionite as an additive component of an electroless nickel plating solution. Has been done. However, when these sulfur compounds are added excessively, the deposition rate of the plating may be lowered and the physical properties of the plating film may be adversely affected.

On the other hand, as described in JP-A-63-289014, the liquid photoresist ink printed on the circuit of the substrate may contain a sulfur compound such as thioxanthone. When a substrate having a resist film formed with such a resist ink is to be plated, the sulfur compound in the resist ink is eluted into the electroless nickel plating solution during the electroless nickel plating operation,
This often causes a decrease in the deposition rate of electroless nickel plating, a poor appearance, a nodule (abnormally deposited particles) defect, a bridge (spread between patterns) defect, and the like.

In general, a sulfur-based additive is not a single element, so that it is difficult to analyze it by a usual analysis method, and since its concentration is low, the influence of other components and impurities is large, and quantitative analysis is very difficult. Is.

A method for controlling the concentration of the sulfur-based additive in the electroless nickel plating solution is disclosed in, for example, Japanese Patent Laid-Open No. 200
0-329727 discloses a method of managing a plating solution based on the measurement result of the deposition potential of electroless nickel plating. However, as described above, since the sulfur compound is mixed as an impurity, it is difficult to obtain the effective amount of the sulfur-based additive by the above method, especially in an aged plating solution, and the appropriate control value and the control method are also required. Since it is unclear, it cannot be said to be a sufficient method for analysis management.

Conventionally, as a control method of an electroless nickel plating solution, concentration control of metallic nickel, sodium hypophosphite, sodium phosphite, etc. by a titration analysis method, pH control by a glass electrode measurement method, fluorescent X-ray film In addition to the control of the plating film thickness and phosphorus content by the thickness measuring device, the control of the deposition state by visual confirmation is performed, but as mentioned above, the control of the sulfur compound amount including the photoresist eluate etc. No method is established.

Therefore, the electroless nickel plating solution can usually be used for about 5 to 6 turns, but in order to prevent the adverse effect due to the accumulation of sulfur compounds and maintain the performance of the electroless nickel plating solution, The reality is that the electroless nickel plating solution is discarded early after it has been used for about 3 turns.

[0008]

The main object of the present invention is to:
The amount of sulfur compounds in the electroless nickel plating solution can be controlled within an appropriate range by simple means, and stable performance is maintained for a long period of time with respect to the depositability of the electroless nickel plating solution and the appearance of the plating film. It is to provide a control method of an electroless nickel plating solution that can be used.

[0009]

Means for Solving the Problems As a result of intensive studies for solving the above-mentioned problems, the present inventor has found that the amount of sulfur compound contained in the electroless nickel plating solution is less than that of the electroless nickel plating film. It was found that there is a certain relationship with the amount of magnetization. Then, in addition to the bath management by the usual bath composition analysis, the electroless nickel plating film is controlled by controlling the amount of sulfur compounds in the plating solution so that the magnetization amount of the electroless nickel plating film is within a certain range. The inventors have found that it is possible to maintain stable performance for a long period of time by preventing insufficient film thickness, non-precipitation, nodule defects, bridge defects, etc., and completed the present invention.

That is, the present invention provides the following method for controlling an electroless nickel plating solution. 1. A method for controlling an electroless nickel plating solution containing hypophosphite as a reducing agent, wherein the amount of magnetization of an electroless nickel plating film formed by using the electroless nickel plating solution is measured, and the amount of magnetization is measured. A method for managing an electroless nickel plating solution, which comprises managing the amount of a sulfur compound in the electroless nickel plating solution based on the result. 2. Magnetization amount of electroless nickel plating film is 0.5 to 2
The method for controlling an electroless nickel plating solution according to the above item 1, wherein the amount of the sulfur compound in the electroless nickel plating solution is controlled so as to be within a range of 00 mT (millitesla).

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION In the management method of the present invention, the target plating solution is an electroless nickel plating solution containing hypophosphite as a reducing agent. The electroless nickel plating solution may be an electroless nickel plating solution using a hypophosphite such as sodium hypophosphite, potassium hypophosphite, and ammonium hypophosphite as a reducing agent. Is not particularly limited, and any known electroless nickel plating solution can be applied to the management method of the present invention. Usually, such an electroless nickel plating solution is
As a basic component, in addition to a reducing agent, nickel sulfate, a water-soluble nickel salt such as nickel chloride, carboxylic acid such as malic acid, citric acid, lactic acid, succinic acid, containing complexing agents such as these salts, Further, it contains a stabilizer, a precipitation accelerator, etc., if necessary.

In the control method of the present invention, electroless nickel plating is performed using the electroless nickel plating solution to be controlled, and the amount of magnetization of the formed electroless nickel plating film is measured. At this time, the plating conditions such as the temperature of the electroless nickel plating solution may be the same as the working conditions in which the plating solution to be managed is actually used. The thickness of the electroless nickel plating film is not particularly limited,
A film having a required thickness may be formed according to the method of measuring the amount of magnetization, but normally, it may be about 3 to 5 μm.

A non-magnetic material such as an aluminum plate is preferably used as a material for forming the electroless nickel plating film. Further, for example, copper, which is used as a circuit material for electronic devices, is a diamagnetic material, but the amount of magnetization has a very low value. Therefore, it was measured even when an electroless nickel plating film was formed using copper as a material. The amount of magnetization can be substantially the amount of magnetization of the electroless nickel plating film. still,
When performing electroless nickel plating on these materials,
Pretreatments such as degreasing treatment, activation treatment, palladium catalyst application, and zinc substitution may be appropriately performed according to the conventional method depending on the type of material.

The method of measuring the amount of magnetization of the electroless nickel plating film is not particularly limited. For example, a VSM device which is a vibrating sample magnetometer, and a handy magnetic field measuring device called a Gauss meter which is commercially available. The magnetization amount may be measured using a known magnetization amount measuring device such as.

The amount of magnetization of the electroless nickel plating film measured by the above-mentioned method has a certain relation with the amount of sulfur compound contained in the electroless nickel plating solution, and the amount of sulfur compound contained in the electroless nickel plating solution is constant. It is recognized that when the amount is increased, the magnetization amount of the plating film is increased, and when the amount of the sulfur compound contained in the electroless nickel plating solution is decreased, the magnetization amount of the plating film is decreased. Therefore, by measuring the amount of magnetization of the electroless nickel plating film,
It is possible to know the increase or decrease in the amount of sulfur compound contained in the electroless nickel plating solution, and the amount of sulfur compound in the plating solution may be controlled within an appropriate range based on the result.

In particular, it is preferable to control the electroless nickel plating solution so that the amount of magnetization of the electroless nickel plating film is within the range of about 0.5 to 200 mT (millitesla), and within the range of about 1 to 100 mT. It is more preferable to manage so that By keeping the amount of magnetization within such a range, the amount of sulfur compounds in the plating solution is maintained in an appropriate range, and the plating film that is formed is prevented from having insufficient film thickness, non-precipitation, nodule defects, bridge defects, etc. You can do it. If the amount of magnetization of the electroless nickel plating film is lower than the above range, the amount of sulfur compound in the plating solution is insufficient,
The depositability is deteriorated, appearance defects are likely to occur, and insufficient film thickness, non-precipitation, uneven gloss, etc. are likely to occur. On the other hand, if the magnetization amount is high, the plating solution becomes excessively precipitating and nodules, bridges, and the like are likely to occur, which is not preferable.

In the control method of the present invention, the amount of sulfur compound in the electroless nickel plating solution may be controlled so that the amount of magnetization of the electroless nickel plating film is within an appropriate range. If the amount of magnetization of the coating is too high, reduce the amount of sulfur compounds contained in the electroless nickel plating solution by adsorbing and removing the impurities in the electroless nickel plating solution using activated carbon, ion exchange resin, etc. Thereby, the amount of magnetization of the electroless nickel plating film can be reduced. In this case, as a specific treatment method, for example, using a filter packed with activated carbon, a method of circulating and filtering an electroless nickel plating solution at appropriate intervals, a method of continuously filtering and circulating during plating, etc. Can be adopted. There is no particular limitation on the type of activated carbon, and any known activated carbon can be used. For example, powdered activated carbon or granular activated carbon made from coconut husk as a raw material, fibrous activated carbon made from coal tar as a raw material, etc. are preferably used. it can.

When the amount of magnetization of the electroless nickel plating film is too low, a known sulfur compound is added as an additive to increase the amount of the sulfur compound in the electroless nickel plating solution, thereby increasing the electroless nickel plating solution. The amount of magnetization of the plating film may be set within an appropriate range.

The control interval of the electroless nickel plating solution may be appropriately determined according to the range of performance required for the plating film to be formed, but in order to minimize fluctuations in plating performance. , For example, the fluctuation range of the magnetization amount is 5
It is preferable to manage it so that it is within about 0 mT.

As described above, according to the control method of the present invention, the amount of sulfur compound in the electroless nickel plating solution can be maintained within an appropriate range. There is no particular limitation on the type of sulfur compound that can be controlled within an appropriate range by the method of the present invention, and in addition to various sulfur compounds that are added to the electroless nickel plating solution as an additive, they are printed on the circuit of the substrate. It is also possible to manage sulfur compounds and the like that have been eluted from the photoresist ink into the electroless nickel plating solution.

[0021]

According to the control method of the electroless nickel plating solution of the present invention, the amount of the sulfur compound in the electroless nickel plating solution can be controlled within a proper concentration range by a simple means.

Therefore, various components of the plating solution are controlled by the bath composition analysis method such as the metallic nickel concentration and the reducing agent concentration and the pH value measuring method which have been conventionally adopted.
By controlling the amount of sulfur compounds contained in the electroless nickel plating solution by the management method of the plating solution of the present invention, insufficient thickness or unprecipitation of the electroless nickel plating film,
Stable plating performance can be maintained for a long period of time by preventing nodules and bridges.

[0023]

EXAMPLES The present invention will be described in more detail with reference to examples.

Example 1 A rolled copper plate (0.2 dm ² ) was used as an object to be plated, degreasing was performed, a palladium catalyst was applied, and then,
The amount of thiodiglycolic acid shown in Table 1 below was added to 200 ml of an electroless nickel plating solution having the following composition, and electroless nickel plating was performed in this plating solution at 85 ° C. for 30 minutes while stirring with air.

Nickel sulfate 0.1 mol / l sodium hypophosphite 0.2 mol / l malic acid 0.1 mol / l lead ion 1.0 mg / l pH 5.0 formed electroless nickel plating film For, the plating film thickness and the phosphorus content were measured using a fluorescent X-ray film thickness measuring device manufactured by Seiko Instruments, and the magnetization amount was measured using a VSM device manufactured by Riken Denshi. The results are shown in Table 1 below.

[0026]

[Table 1]

As is clear from the results shown in Table 1, when the electroless nickel plating solution containing no thiodiglycolic acid was used, the amount of magnetization of the formed plating film was 0 mT.

On the other hand, when thiodiglycolic acid is added to the electroless nickel plating solution, the amount of magnetization of the formed plating film increases as the amount of thiodiglycolic acid added increases, and the amount of magnetization is zero. When it was in the range of 0.5 to 200 mT, a good plating film could be formed at an appropriate deposition rate.

On the other hand, when the magnetization amount was less than 0.5 mT, that is, when thiodiglycolic acid was not added, the deposition rate was slow and the appearance of the plating film was poor. Further, when the amount of thiodiglycolic acid added was large and the amount of magnetization was more than 200 mT, the precipitation was excessive and white unevenness was observed on the entire surface.

From these results, by controlling the plating solution such that the amount of magnetization of the electroless nickel plating film is in the range of 0.5 to 200 mT, the amount of sulfur compound in the plating solution is kept in an appropriate range. It was confirmed that it can be managed.

Example 2 A resist film was formed by using a commercially available liquid photoresist ink containing a thioxanthone type sulfur compound in an electroless nickel plating solution containing no thiodiglycolic acid similar to that used in Example 1. The circuit board thus prepared was immersed at 85 ° C. for 2 hours to elute the sulfur compound contained in the photoresist ink into the plating solution. The surface area of the substrate with respect to 1 liter of the plating solution was 10 dm ² .

After immersing the circuit board in the electroless nickel plating solution in this manner, the circuit board was taken out, and the first embodiment was prepared.
Perform electroless nickel plating on the rolled copper plate in the same manner as
When the amount of magnetization of the plating film was measured, it increased to 210 mT, and the appearance was cloudy on the entire surface.

The plating solution was treated with activated carbon by continuously circulating the plating solution for 1 hour using a filter filled with fibrous activated carbon made from coal tar. When electroless nickel plating was performed using the electroless nickel plating solution after the activated carbon treatment in the same manner as described above, the formed plating film had a magnetization amount of 0 mT,
Appearance is cloudy with uneven gloss and deposition rate is 4 μm / 3
It was a low value of 0 minutes.

When 0.8 mg / l of thiodiglycolic acid was added to this electroless nickel plating solution and electroless nickel plating was performed, the amount of magnetization of the formed plating film was 20 mT, and the deposition rate and The plating appearances were all good.

The above results are shown in Table 2 below.

[0036]

[Table 2]

As is clear from Table 2, the electroless nickel plating solution in which the magnetization of the formed plating film exceeds 200 mT was treated with activated carbon, and then a sulfur compound was added to the plating film so that the magnetization of the plating film had an appropriate value. It was confirmed that the deposition rate of the electroless nickel plating and the plating appearance can be maintained in a good state by adjusting so as to fall within the range.

Example 3 As a material to be plated, a circuit board having a copper circuit on which a resist film was formed using a commercially available liquid photoresist ink containing a thioxanthone type sulfur compound was used, and as a pretreatment, degreasing treatment with an acidic degreasing agent was used. After the activation treatment with a persulfate solution and the catalytic treatment with a palladium solution, the same electroless nickel plating solution without thiodiglycolic acid as that used in Example 1 (solution temperature 85 ° C.) In the inside, an electroless nickel plating film was formed on the copper circuit.

Before the start of plating, after one turn, after two turns, and after three turns, an electroless nickel plating film was formed on the rolled copper plate by the same method as in Example 1, and the amount of magnetization was measured. As a result, as the number of turns increases, the sulfur compound elutes from the resist film on the surface of the circuit board into the plating solution, and the magnetization amount of the plating film rises. After 3 turns, the magnetization amount becomes 140 mT, and the appearance of the plating film appears. It became a little cloudy.

On the other hand, thiodiglycolic acid 0.8 mg /
Using the added electroless nickel plating solution, a copper circuit board having a resist film similar to the one described above is used as the object to be plated, and electroless nickel plating is continuously performed, and after each turn, The activated carbon treatment was carried out by continuously circulating the plating solution for 1 hour using a filter filled with fibrous activated carbon made from coal tar.

An electroless nickel plating film was formed on the rolled copper plate in the same manner as in Example 1 for each turn, and the amount of magnetization was measured.
The appearance of the plating film was good and the magnetization amount finally increased to 120 mT after 6 turns, and the plating film became slightly cloudy.

From the above results, by controlling the electroless nickel plating solution by the method of the present invention, the electroless nickel plating solution can be maintained in a good state for a long period of time, and the number of usable turns can be increased. It could be confirmed.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Takashi Yokohata             Osaka Prefecture Osaka City Tsurumi-ku Release 1-10-25 East               Okuno Pharmaceutical Industry Co., Ltd. (72) Inventor Kaoru Naito             Osaka Prefecture Osaka City Tsurumi-ku Release 1-10-25 East               Okuno Pharmaceutical Industry Co., Ltd. F-term (reference) 2G053 AA00 AA04 AB01                 4K022 BA14 DB02 DB08 DB25 DB28

Claims (2)

[Claims] 1. A method for controlling an electroless nickel plating solution containing hypophosphite as a reducing agent, which comprises measuring a magnetization amount of an electroless nickel plating film formed using the electroless nickel plating solution. A method for managing an electroless nickel plating solution, characterized in that the amount of a sulfur compound in the electroless nickel plating solution is managed based on the measurement result of the magnetization amount. 2. The amount of magnetization of the electroless nickel plating film is 0.
Within the range of 5 to 200 mT (millitesla),
The method for managing an electroless nickel plating solution according to claim 1, wherein the amount of the sulfur compound in the electroless nickel plating solution is managed.