JP2822840B2 - Plating method and plating apparatus for electroless tin, lead or their alloys - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for plating electroless tin, lead, or an alloy thereof on copper or a copper alloy. More specifically, the present invention corrects a change in the composition of a plating solution caused by pumping, and provides a simple and accurate method. The present invention relates to a method and a plating apparatus for electroless tin, lead or an alloy thereof capable of performing continuous plating while maintaining a constant plating performance of a plating bath.

[0002]

2. Description of the Related Art Conventionally, in order to impart solderability to copper or copper alloy parts of electronic industrial parts, circuits, etc., tin, lead or tin-lead alloy plating is carried out by electroplating. Although a film is formed, components and circuits are miniaturized or complicated with the miniaturization of electronic devices, and some parts cannot be plated by electroplating.

[0003] Therefore, an electroless tin, lead or tin-lead alloy plating method capable of plating even a portion where application of the electroplating method is difficult has been studied. For example, Japanese Patent Application Laid-Open No. 1-1842
No. 79 discloses an electroless tin-lead alloy plating containing a specific organic sulfonic acid, tin and lead salts of the organic sulfonic acid, sodium hypophosphite (reducing agent) and thiourea (complexing agent) as main components. A method using a bath has been proposed.

[0004] However, the conventional electroless tin, lead or tin-lead alloy plating method is often a disposable batch method in which the metal concentration in the plating bath is reduced to a deposition limit or less without replenishing the metal, and the metal is discarded as it is. Therefore, there is almost no proposal to use a plating bath continuously for the purpose of obtaining a thick plating film, and therefore a constant and constant deposition amount required for continuous use can be maintained. As for the replenishment management method of the plating bath, there is no practically effective proposal at present.

On the other hand, in a normal electroless plating method,
Replenishing the plating bath with a chemical corresponding to the consumed metal content enables thickening. More specifically, solution management is performed by analyzing the plating solution used, measuring the metal concentration, calculating the insufficient metal component from the measurement result, and replenishing the amount of the chemical according to the calculation result. I have.

However, according to the study of the present inventors, in the case of electroless tin, lead or a tin-lead alloy plating bath, the metal components tin and lead are elements which are originally difficult to analyze easily, and the In the electrolytic plating solution, the copper eluted from the object to be plated dissolves and accumulates in the plating bath as the plating proceeds, so that it is difficult to easily and accurately analyze tin and lead components. Plating bath management method is electroless tin,
It was difficult to apply to a lead or tin / lead alloy plating bath.

Therefore, the present inventors can relatively easily analyze the tin and lead consumption of the electroless tin, lead or tin-lead alloy plating bath, and can analyze the electroless tin, lead or tin-lead alloy plating bath. As a result of repeating various tests in order to develop a method for effectively performing bath management, the amount of copper eluted into the plating bath as the plating progresses and the amount of metal consumed is reduced. The inventors have found that there is a proportional relationship, and have previously proposed a method of measuring the copper ion concentration in a plating bath and replenishing metal components in accordance with the measured value (Japanese Patent Application Laid-Open No. 4-276081).

However, subsequent studies have revealed that the analysis of the copper concentration in the plating bath alone may not be able to maintain an appropriate concentration composition. That is, the reduction of the metal component due to the dilution of the plating solution due to the pumping out of the plating solution during the plating operation is not supplied, and even if the copper elutes into the plating bath due to the progress of plating, the copper in the plating bath is In some cases, the concentration of the eluted copper may not be increased enough to be pumped out, so that accurate metal replenishment may not be possible.

The present invention has been made in view of the above circumstances, and can easily correct the effect of pumping on a plating bath. Even when the effect of pumping is large, electroless tin, lead, or a tin-lead alloy can be used. It is possible to easily and surely control the tin and lead content in the plating bath. Therefore, it is easy to apply thick plating, and a plating method and apparatus for electroless tin, lead or tin-lead alloy capable of continuous plating. The purpose is to provide.

[0010]

Means and Action for Solving the Problems The present inventors have
After intensive studies to achieve the above object, the effect of pumping out was analyzed by analyzing the concentration of thioamides such as thiourea and its derivatives used as complexing agents, and adjusting the concentration of thioamides to the set concentration. It has been found that the problem can be solved by replenishing the species and adding other components in proportion thereto.

That is, the amount of reduction in the concentration of each component due to pumping out of the plating solution is expected to be proportional to the concentration of each component.
This can be confirmed by pumping experiments. Therefore, while preparing a replenisher solution (hereinafter referred to as “correction solution”) that is close to the solution composition, monitoring one of the components in the plating solution, and replenishing the insufficient amount with the above-mentioned correction solution, the concentration of all components is corrected. It is considered possible. However, the analysis of the metal ions in the plating bath is difficult because the concentration of the metal ions fluctuates due to the plating operation as the concentration decreases due to pumping. Therefore, the present inventors repeated trial and error and conducted various examinations. As a monitor component, thioamides such as thiourea, which complex the metal component in the plating solution, were used as a monitor component, and the above-mentioned correction solution was replenished. The effect on each component in the plating bath can be accurately corrected, and by combining this operation with the conventional method of replenishing the metal component according to the increased amount of copper ions, even if the effect of pumping is large, It has been found that tin and lead in an electroless tin, lead or tin-lead alloy plating bath can be easily and reliably controlled, and that thick plating can be easily performed and continuous plating can be performed. The present invention has been completed.

[0012] Accordingly, the present invention provides an electroless plating bath containing a water-soluble tin salt and / or a water-soluble lead salt, an acid for dissolving these salts, and a thioamide as a complexing agent. When applying electroless tin, lead or an alloy thereof to an alloy, replenishing each component constituting the plating solution in proportion to the reduction amount of thioamides in the plating bath. Using an electroless plating bath containing a water-soluble tin salt and / or a water-soluble lead salt, an acid for dissolving these salts, and a thioamide as a complexing agent; Alternatively, when plating copper alloy with electroless tin, lead or their alloys, replenish water-soluble tin salts and / or water-soluble lead salts in proportion to the increase in the concentration of copper ions eluted into the plating bath. Thiol in the plating bath Electroless tin, characterized in that replenishing the components constituting the plating solution with the reduction amount of bromide compound to provide a lead or methods for their alloy plating.

Further, the present invention provides a plating apparatus which can perform electroless tin, lead or alloy plating thereof while automatically replenishing a plating solution according to the above plating method.
A plating tank containing an electroless plating bath containing a water-soluble tin salt and / or a water-soluble lead salt, an acid dissolving these salts, and a thioamide as a complexing agent; Sampling means for sampling a plating solution, a replenishing solution tank containing a replenishing solution for each component constituting the plating bath, and a replenishing solution replenishing means for replenishing the plating tank with a predetermined amount of the replenishing solution from the replenishing solution tank. A metal salt replenishing tank containing a metal salt component constituting the plating bath, a metal salt replenishing means for replenishing a predetermined amount of the metal salt component from the metal salt replenishing tank to the plating tank, and sampling by the sampling means. Analyzing the plating solution to measure the concentration of thioamides and the concentration of copper ions, and detecting a change in these concentrations; A replenishing control means for controlling the replenishing means, sampling a predetermined amount of the plating solution from the plating tank by the sampling means, measuring the concentration of the thioamides and the copper ion concentration by the analyzing means, and changing these concentrations. And by controlling the replenishing solution replenishing means and the metal salt replenishing means with the replenishing control means in accordance with the concentration change, the water-soluble tin salt and / or the water-soluble tin salt are proportionally increased in proportion to the increase of the copper ion concentration. In addition to replenishing the metal salt component of the lead salt from the metal salt replenishing tank to the plating tank, replenishing solution composed of each component constituting the plating solution is replenished from the replenishing solution tank to the plating tank in proportion to the reduced amount of thioamides. And a plating apparatus for electroless tin, lead or an alloy thereof.

Hereinafter, the present invention will be described in more detail.
The plating bath used in the present invention contains a metal salt component composed of a water-soluble tin salt, a water-soluble lead salt or a mixture thereof, an acid component that dissolves these metal salts, and a complexing agent as main components. Things.

The water-soluble tin salt includes, for example, stannous sulfate, stannous alkanesulfonate, stannous chloride, stannous alkanolsulfonate, stannous sulfosuccinate and the like. Examples of the water-soluble lead salt include lead chloride, lead methanesulfonate, lead acetate, lead alkanolsulfonate, and lead sulfosuccinate. The content of these metal salt components is 0.1 to 50 g / L, particularly 0.5 to 2 g / L.
It is preferably 5 g / L. If the content of the metal salt component is too small, the deposition rate tends to decrease. Also,
Examples of the acid component that dissolves these metal salts include alkanesulfonic acid, hydrochloric acid, alkanolsulfonic acid, perchloric acid, sulfosuccinic acid, and borofluoric acid. The content of these acid components is 10 to 250 g / L, particularly 50 to 250 g / L.
It is preferably 200 g / L. If the content of the acid component is too small, precipitation of the metal salt may occur, while if it is too large, the deposition rate tends to decrease.

The alkanesulfonic acid and alkanolsulfonic acid include, for example, methanesulfonic acid, ethanesulfonic acid, propanesulfonic acid, 2-propanesulfonic acid, butanesulfonic acid, pentanesulfonic acid, hexanesulfonic acid, and decanesulfonic acid. , Dodecanesulfonic acid, isethionic acid (2-hydroxyethane-1-sulfonic acid), 2-hydroxypropane-1-sulfonic acid,
1-hydroxypropane-2-sulfonic acid, 3-hydroxypropane-1-sulfonic acid, 2-hydroxybutane-1-sulfonic acid, 4-hydroxybutane-1-sulfonic acid, 2-hydroxypentane-1-sulfonic acid, 2-
Hydroxyhexane-1-sulfonic acid, 2-hydroxydecane-1-sulfonic acid, 2-hydroxydodecane-1
-Sulfonic acid and the like.

As the complexing agent, thioamides are used, and specific examples thereof include thiourea and thiourea derivatives such as thioformamide and thioacetamide. Among these, thiourea is generally used. Used for The content of these complexing agents is 10-250 g / L, especially 50-250 g / L.
It is preferably 200 g / L. If the content of the complexing agent is too small, the deposition rate tends to decrease.

Further, a reducing agent can be added to the plating bath. As the reducing agent, hypophosphorous acid or a salt thereof is usually used, and its addition amount is 10 to 200 g / L, particularly 5
It is preferred to be 0 to 150 g / L.

The method of plating tin, lead or their alloys according to the present invention is carried out using the above-mentioned plating bath, and the plating bath having at least a part of the surface formed of copper or a copper alloy in the plating bath. An object is immersed, thereby forming a tin, lead or tin-lead alloy plating film on copper or a copper alloy.

In this case, the plating solution is diluted by pumping out the plating solution by repeatedly immersing and lifting a large number of objects to be plated. In the method of the present invention, thioamide compounded in the plating bath as a complexing agent is used. By measuring the concentration of each type and replenishing each component in proportion to the decrease, the effect of pumping was corrected and plating could be performed continuously while maintaining a constant bath composition. is there.

Here, the method of measuring the concentration of thioamides in the plating bath is not particularly limited, but a plating solution is taken out of the plating bath, and an acid is added to the plating solution to make it acidic, especially pH 2 or less. After the adjustment, a method of adding a bismuth ion to form a color and quantitatively determining the color by a colorimetric method is suitably adopted.

That is, the present inventors have studied a quantification method by a colorimetric method, which is an inexpensive analysis method suitable for automatic analysis, as a method for measuring the concentration of thioamides. Conventionally, there has been known a method in which thiourea is added to quantitative analysis of bismuth and measurement is performed by a colorimetric method, and this method forms a complex between bismuth ions and thiourea and a derivative thereof to form a yellow color. The present inventors have made various studies, considering that it is possible to develop color by adding bismuth ions to thioamides and to quantify the thioamides by colorimetric analysis.

However, even if bismuth ions are simply added to the plating solution separated from the tin, lead or tin-lead alloy plating bath, stable color formation cannot be obtained. As a result, further studies were conducted to stabilize the color formation. By adding an acid to the sample and acidifying it, and particularly adjusting the pH to 2.0 or less, by adding bismuth ions, a stable color can be obtained, and the concentration of thioamides can be easily and accurately determined by a colorimetric method. It has been found that quantitative analysis can be performed.

The acid for adjusting the sample to be acidic includes inorganic acids such as sulfuric acid, perchloric acid and pyrophosphoric acid, and organic sulfonic acids such as methanesulfonic acid and ethanesulfonic acid. The addition concentration can be 10 to 900 g / L. In addition, this quantitative analysis method utilizes a coloration of the complex by forming a complex between the bismuth ion and the thioamides. Therefore, by adding a complexing agent for analysis at the time of analysis, it is more accurate. Colorimetric analysis. In this case, as a complexing agent for analysis, carboxylic acids such as oxalic acid, tartaric acid and citric acid, EDTA,
Aminocarboxylic acids such as CyDTA, EDTA-OH, NTA, IDA, HEDP (hydroxyethanediphosphonic acid), NTPO (nitrilotrismethylenesulfonic acid)
And the like, and salts thereof, and the like, and these can be used alone or in combination of plural kinds. The concentration of the complexing agent for analysis is not particularly limited, but is usually in the range of 5 to 200 g / L.

The bismuth ion can be added to a sample as the above-mentioned acid salt, nitrate salt, chloride salt or a basic salt or oxide thereof. The concentration of the bismuth ion is not particularly limited. Suitably, it is about 20 g / L. The colorimetric analysis method uses a wavelength of 480.
The method of measuring the absorbance around nm is recommended because the concentration of thioamides can be easily and accurately determined.

In the plating method of the present invention, the concentration of thioamides in the plating bath is measured at any time as described above, and each component is adjusted in accordance with the mixing ratio of each component so as to compensate for the decrease in the concentration of thioamides. Add proportionally. In this case, by adjusting a replenishing solution having a predetermined composition and adding the replenishing solution so as to compensate for the decrease in the concentration of the thioamides, it is possible to simultaneously replenish an appropriate amount of all components.

Therefore, according to the electroless tin, lead or alloy plating method of the present invention, even when the plating bath is continuously used, the dilution of the plating solution by pumping is corrected to maintain a stable bath composition. be able to. In this case, the metal components of tin and lead in the plating bath gradually decrease due to the repetition of plating, and the above-mentioned replenishment alone becomes insufficient, but at this time, the plating is performed in proportion to the decrease of these metal components. By repetition of the above, the copper component elutes from the plating object into the plating bath, and the copper ion concentration in the plating bath increases. Therefore, by measuring the concentration of copper ions in the plating bath as needed, and replenishing the metal components of tin and lead in proportion to the increase of the copper ions, it is possible to accurately replenish the metal components reduced by precipitation. ,
By correcting the dilution of the plating solution by pumping as needed by the above method and by replenishing the metal component reduced by precipitation as needed by this method, the composition of the plating bath can be kept constant over a long period of time. The plating bath can be used continuously for a long period of time while maintaining the plating performance.

Here, the method of quantifying copper ions can be carried out by employing atomic absorption spectrometry or the like.
Particularly, a complexing agent such as oxalic acid or tartaric acid is added to the plating solution separated from the plating bath to adjust the pH to 4 to 11, and an oxidizing agent such as aqueous hydrogen peroxide is added to convert monovalent copper ions to divalent copper ions. After oxidizing to copper ions and further adding a coloring agent such as ammonia or amines, a method of measuring the absorbance at a wavelength of 620 nm is recommended because the total copper content can be easily and accurately determined.

By such an operation, the concentration of copper ions in the plating bath is analyzed as needed, and when the concentration of copper ions reaches a predetermined control concentration (when the amount is increased by a predetermined amount), tin in proportion to the increase is determined. The salt or lead salt can be replenished directly or dissolved in water, or as a plating solution containing the metal salt.

Further, in order to keep the deposition rate constant between the initial stage and the later stage of the plating, a copper salt is added to the new solution to raise the copper concentration in the plating bath to, for example, 2 to 10 g / L before plating. At the same time, the copper ion concentration in the plating bath may be analyzed as needed, and the metal component may be replenished when the copper ion concentration reaches the upper limit of the predetermined control range. The copper source in this case includes copper sulfate, copper chloride, copper acetate, copper nitrate, copper oxalate, copper hydroxide, copper alkane sulfonate, copper alkanol sulfonate, copper perchlorate, copper borofluoride, sulfosuccinic acid Copper oxides such as copper and copper salts, cupric oxide, etc.
Metallic copper (plate, wire, or powder) can be used.

Here, the thioamides of the complexing agent are quantified in this way to correct the change in the composition of the plating solution by pumping, and the amount of tin and / or lead consumed by quantifying the amount of copper in the plating solution. When the plating bath is controlled by replenishing, the amount of copper eluted into the plating bath by pumping is reduced, and even if tin and / or lead are replenished according to the quantitative value of copper, these metals The concentration of the component is slightly lower than the set concentration. Therefore, when performing correction of each component by quantification of thioamides, the copper pumping reduction was calculated from the copper concentration at the previous quantification, that is, from the content ratio of thioamides and copper before the plating operation. It is preferable to replace the reduced amount with tin and / or lead and supply it to the plating bath. This makes it possible to accurately supply tin and / or lead in proportion to the increase in the amount of copper eluted by the plating reaction. In this case, when the correction is performed by the quantification of thioamides or the correction by the quantification of copper, it is possible to cope with the correction by supplementing a large amount of tin and / or lead in consideration of the pumped amount of copper. .

Furthermore, it is preferable to additionally replenish other components such as an acid and a reducing agent at the time of the above-mentioned pumping correction. In this case, the replenishment amounts of these other components are appropriately selected according to the composition of the bath solution.

Further, tin and / or lead are maintained at a substantially constant concentration by the above bath management, but the copper concentration gradually increases due to repetition of plating. In this case, a complexing agent is consumed to complex the copper ions due to the increase of the copper ions, which may cause deterioration of plating performance such as a decrease in deposition rate. Therefore, it is preferable to additionally supply thioamides as a complexing agent in accordance with an increase in copper content. ,
In this case, replenishment of thioamides, for example, in the case of thiourea, is considered to require a minimum of 3 moles per mole of copper to cover up the copper. Specifically, the copper content is 0.2 g / L. It is preferred to replenish thiourea at 0.7-3 g / L each time it is increased. If the replenishment amount of the thioamides is small, the deposition rate of the plating film is decreased. On the other hand, if it is too large, the deposition rate is improved, but the alloy composition of the coating may be changed.

Correction of the pumped-out amount by quantitative analysis of the above thioamides and metal component (Sn,
Table 1 below summarizes the bath management in combination with the replenishment of the reduction in the plating reaction of Pb).

[0035]

[Table 1]

The plating method of the present invention can be performed by the plating apparatus shown in FIG. That is, FIG. 1 shows an example of the plating apparatus of the present invention. In FIG. 1, reference numeral 1 denotes a plating tank containing the plating bath 2, and reference numeral 3 denotes a replenishing solution containing replenishing liquid 9 of each component constituting the plating bath 2. Tank, 4 is plating bath 2
A metal salt replenishing tank containing a metal salt component 10 constituting
Is a pump (supplementing solution replenishing means) for replenishing the plating tank 1 with a predetermined amount of the replenishing solution 9 from the replenishing solution tank 3, and 6 is replenishing the plating tank 1 with a predetermined amount of the metal salt component 10 from the metal salt replenishing tank 4. A pump (metal salt replenishing means), and an analytical instrument (analyzing means) 7 for analyzing a predetermined amount of plating solution sampled from the plating tank 1 by a pump (sampling means) 8 to measure the concentration of thioamides and the concentration of copper ions. )
The analyzer 7 has a built-in computer (supply control means) for detecting changes in the concentrations of these components and controlling the pumps 5 and 6 according to the results.

Then, the plating tank 1 of the plating apparatus
A water-soluble tin salt and / or a water-soluble lead salt as a plating bath 2,
An acid for dissolving these salts, and containing the electroless plating bath containing thioamides as a complexing agent,
The replenishing solution tank 3 and the metal salt replenishing tank 4 respectively contain a replenishing solution 9 composed of each component constituting the plating bath 2 and a metal salt component 10 of a water-soluble tin salt and / or a water-soluble lead salt. An object to be plated is continuously immersed in a plating bath 2 in 1 and then pulled up to perform plating. In this case, a predetermined amount of the plating solution is sampled from the plating tank 1 by the pump 8 at predetermined intervals, and the concentration of the thioamides and the copper ion concentration are measured by the analyzer 7 to detect a change in these concentrations. Analytical equipment 7 according to concentration change
By controlling the pumps 5 and 6 with a computer incorporated in the water, the metal salt component 10 of the water-soluble tin salt and / or the water-soluble lead salt is supplied from the metal salt replenishing tank 4 in proportion to the increase in the copper ion concentration. In addition to replenishing the plating tank 1, a replenishing solution 9 composed of each component constituting the plating solution is supplied to the plating tank 1 in proportion to the reduced amount of thioamides.

The method of preparing the sampled plating solution, the method of measuring the metal salt concentration and the concentration of thioamides by the analytical instrument 7, and the setting of the composition and amount of the replenishing solution 9 are performed in accordance with the above-described method of the present invention. Can be. Further, one replenishing solution tank 3 and one metal salt replenishing tank 4 are provided, respectively. However, two or more of these are provided, each containing a replenishing solution having a different concentration or composition, and depending on the analysis result of the plating solution. Replenishing liquid can be appropriately supplied from these tanks to perform more accurate bath management, and other configurations can be appropriately changed.

[0039]

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to the following examples. Prior to the examples, an analysis example of the thiourea concentration in the plating bath is shown as an experimental example. [Experimental Examples] Four types of electroless tin / lead alloy plating baths having the following composition with varied amounts of thiourea were prepared, and the thiourea concentrations in these plating baths were analyzed by the following method. Table 2 shows the results.

Electroless tin / lead alloy plating bath composition 50 g / L methanesulfonic acid 20 g / L tin methanesulfonate 13 g / L thiourea See Table 2 Sodium hypophosphite 80 g / L Citric acid 15 g / L Laurylpyridium chloride 5 g / L EDTA 3 g / L pH 2.0 Bath temperature 80 ° C. Plating rate 5 μm / 15 min Sn (wt%) 75

Analysis Method 1 mL of the plating solution was taken out of the plating bath, and 40 mL of a solution containing 4 g / L of bismuth oxide, 10 g / L of EDTA.4H, and 500 g / L of methanesulfonic acid was added thereto. Make up to 50 mL with ion exchanged water. This is 5
After standing for minutes, the absorbance was measured at a wavelength of 480 nm using an absorbance meter (U-3210 manufactured by Hitachi, Ltd.), and the thiourea concentration was measured.

[0042]

[Table 2]

From the results shown in Table 2, it was confirmed that the thiourea concentration in the plating bath can be accurately measured by this method.

Example The amount of thiourea was 100 g /
Using the same electroless tin-lead alloy plating bath as that used in the above-described experimental example, the printed wiring board on which the copper pattern was formed was subjected to a running test. At this time, the plating solution was analyzed at any time, and the following replenishers (1), (2), and (3) were replenished in the amounts shown below each time the amount of copper increased by 0.2 g / L, and the amount of thiourea was reduced. Each time the amount was reduced by 2 g / L, the following replenishers (1), (2), and (3) were replenished in the amounts shown below, and plating was performed while correcting each component in the plating bath. In this case, the quantification of thiourea was performed in the same manner as in the above experimental example, and the quantification of the copper amount was performed using a fluorescent X-ray analyzer.

Replenisher (1) Tin methanesulfonate 40 g / L Thiourea 200 g / L Replenisher (2) Lead methanesulfonate 50 g / L Replenisher (3) Methanesulfonic acid 100 g / L Sodium hypophosphite 215 g / L L Citric acid 40 g / L Laurylpyridinium chloride 13 g / L EDTA 50 g / L Replenishment amount by copper amount Replenishment by thiourea amount Replenisher (1) 10 ml / L 10 ml / L Replenisher (2) 2 ml / L 5.2 ml / L Replenisher (3)-10ml / L

The plating process on the printed wiring board was continuously repeated while performing bath management as described above. At this time, immediately after the components of the plating bath were corrected by the replenishment of the replenishers (1), (2) and (3), the concentrations of Sn and Pb in the plating bath were successively measured using a fluorescent X-ray analyzer. , The fluctuation width (deviation from the set value) was observed. Table 3 shows the results. The printed wiring board used had a pattern ratio of 1.0% and a bath load of 0.5 m ² board / 100 L. A tin / lead alloy plating film having a thickness of 5 μm was formed on the copper pattern of the printed wiring board. did. The determination of the amount of copper and the determination of thiourea were performed every 45 racks.

[0047]

[Table 3]

As is clear from the results shown in Table 3, according to the plating method of the present invention, tin and lead in the plating bath can be accurately replenished while compensating for the influence of pumping out. It has been confirmed that continuous plating can be stably performed while maintaining the plating performance of.

[0049]

As described above, according to the electroless tin, lead or tin-lead alloy plating method and plating apparatus of the present invention, the influence of pumping can be eliminated, and even if the effect of pumping is large, In addition, the content of tin and lead in the electroless tin, lead or tin / lead alloy plating bath can be easily and reliably controlled, so that thick plating is easy.

[Brief description of the drawings]

FIG. 1 is a schematic view showing a plating apparatus according to one embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Plating tank 2 Plating bath 3 Replenishing liquid tank 4 Metal salt replenishing tank 5 Pump (replenishing liquid replenishing means) 6 Pump (metal salt replenishing means) 7 Pump (sampling means) 8 Analytical equipment (analyzing means) 9 Replenishing liquid 10 Metal salt component

──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Tohru Kamitama 1-5-1 Hirakata Exit, Hirakata-shi, Osaka Uemura Industry Co., Ltd. Central Research Laboratory (58) Field surveyed (Int.Cl. ⁶ , DB name) C23C 18 / 31,18 / 48

Claims (3)

(57) [Claims] 1. An electroless plating bath containing a water-soluble tin salt and / or a water-soluble lead salt, an acid for dissolving these salts, and a thioamide as a complexing agent. When plating electroless tin, lead or their alloys,
A method for plating electroless tin, lead or an alloy thereof, wherein each component constituting a plating solution is replenished in proportion to the reduction amount of thioamides in the plating bath. 2. An electroless plating bath containing a water-soluble tin salt and / or a water-soluble lead salt, an acid for dissolving these salts, and a thioamide as a complexing agent is used for copper or copper alloy. When plating electroless tin, lead or their alloys,
A water-soluble tin salt and / or a water-soluble lead salt are replenished in proportion to an increase in the concentration of copper ions eluted into the plating bath, and a plating solution is supplied in proportion to a decrease in thioamides in the plating bath. A method of plating electroless tin, lead or an alloy thereof, wherein each constituent component is supplied. 3. A plating tank containing an electroless plating bath containing a water-soluble tin salt and / or a water-soluble lead salt, an acid for dissolving these salts, and thioamides as a complexing agent, and the plating tank. A sampling means for sampling a predetermined amount of the plating solution from the tank; a replenishing solution tank containing a replenishing solution for each component constituting the plating bath; and a replenishing solution of a predetermined amount from the replenishing solution tank to the plating tank. A replenishing solution replenishing means, a metal salt replenishing tank containing a metal salt component constituting the plating bath, a metal salt replenishing means for replenishing the plating tank with a predetermined amount of the metal salt component from the metal salt replenishing tank, The plating solution sampled by the sampling means is analyzed to measure the concentration of thioamides and the concentration of copper ions, and an analysis means for detecting a change in these concentrations, and the replenisher is supplied according to the analysis result by the analysis means. Means and replenishment control means for controlling the metal salt replenishment means, sampling a predetermined amount of plating solution from the plating tank by sampling means,
The concentration of the thioamides and the concentration of copper ions are measured by the analysis means to detect a change in these concentrations, and the replenishment control means controls the replenishment liquid replenishment means and the metal salt replenishment means in accordance with the concentration change. The metal salt component of the water-soluble tin salt and / or the water-soluble lead salt is replenished from the metal salt replenishing tank to the plating tank in proportion to the increase in the copper ion concentration, and the plating solution is proportional to the decrease in thioamides. An electroless tin, lead or alloy plating apparatus configured to replenish a replenishing solution composed of each component constituting the above from a replenishing solution tank to a plating tank.